Anatomy Facts

On the first day of this semester, the brilliant Miss Charlotte suggested that she and I start an email-an-anatomy-fact-a-day habit to help us keep on top of our anatomy studies this semester. She got the idea from a friend who is a year ahead of us and therefore privy to the challenge that is second semester of second year. Anatomy this semester is only 3 credits, less than half of what it was previously. It is therefore very easy to let it fall to the side – which we can’t do with our final exam approaching!

We decided to turn it up a notch and send each other the same number of facts per day as the week of the semester (1 each day for the first week, 2 for the second, etc).

The rules? None really! We can write about anything we want as long as it involves anatomy. Since we will building up quite the stash of facts, I thought it would be fun to post them here as well. So, follow along on our anatomy fact adventure!

Disclaimer: these facts are correct to the best of our knowledge, if you notice a mistake, please let me know and I will fix it!

UPDATE: We made it to week 7 before we burned out ūüôā As Charlotte said, “it served its purpose”. It worked well in the beginning, but since we are studying so much anatomy anyway, we don’t need it as a motivational tool anymore. I’ll leave up the facts I was able to upload here in case anyone is curious¬†about what type of facts we need to know.¬†


1. The pterygomandibular space is one of the four masticator spaces. It contains two nerves in a characteristic arrangement: anteriorly, the lingual nerve, and posteriorly, the inferior alveolar nerve. It also contains the inferior alveolar vessels and the sphenomandibular ligament.

2. The superior mesenteric artery is at the level of L1. “Nutcracker Syndrome” (aka Renal Vein Entrapment) is a condition in which the left renal vein is compressed in its location between the superior mesenteric artery and the abdominal aorta.

3. The nasolacrimal canal connects the orbit to the inferior nasal meatus. it contains the nasolacrimal duct.

4. The weakest part of the skull is called the pterion. It is the meeting point of three bones: parietal bone, squamous part of the temporal bone and the greater wing of the sphenoid bone. The anterior division of the middle meningeal artery runs underneath it and a traumatic blow to this region may rupture the artery causing an epidural hematoma

Fun additional fact: Hermes (messenger of the gods in Greek mythology) had wings on his sandals and on his head – attached to the pterion!

5. The Whipple procedure, also known as a pancreaticoduodenectomy, is a major surgery involving the pancreas, duodenum and antrum (the distal segment) of the stomach.

This surgery is performed to remove cancerous tumors from the head of the pancreas. Since the pancreas and duodenum share the same arterial blood supply, both must be removed. This artery is the gastroduodenal artery, which is a branch of the common hepatic artery, supplies the organs via the anterior and posterior superior pancreaticoduodenal arteries. If only one of the organs were to be removed, it would interrupt the blood supply to the remaining organ, eventually leading to tissue necrosis.

6. Ligamentum flavum (yellow ligament, color from elastic fibers) extends between the laminae of vertebrae from the axis to the sacrum, on the posterior wall of the central canal. It is thickest in the lumbar region; Thickening (hypertrophy) can lead to central canal stenosis, especially when the canal is already narrowed, eg due to herniation of a vertebral disc.

7. The bilaminar embryonic disk occurs in the second week after fertilization. Two layers originate from the inner cell mass (embryoblast) prior to implantation:

    1. Hypoblast Рinner, cuboidal cells lining the primitive yolk sac; gives rise to extraembryonic endoderm, including the yolk sac.
    2. Epiblast¬†– outer, columnar cells lining the amnionic cavity and continuous with the amnion;¬†the fluid-filled space in the epithelium of the epiblast is the¬†primordial ¬†amniotic cavity.Only the epiblast is responsible for forming the embryo proper.¬†Epiblast cells also undergo a special “epithelial-to-mesenchymal” transition to become the mesenchyme of the primitive streak.

(The primitive streak is important for differentiation of the endo-, meso-, ectoderm and for establishing bilateral symmetry).

8. Urine passes from the apex of the renal papilla (via a papilla) into the minor calyx –> major calyx –> renal pelvis (=the convergence of a few major¬†calices) –> ureter –> bladder.

9. The lungs are not symmetrical:

The right lung has 3 lobes: superior, middle, and inferior. The horizontal fissure separates the superior lobe from the middle lobe; the right oblique fissure separates the middle and inferior lobes.

The left lung is smaller due to the position of the heart. It has 2 lobes, superior and inferior, which are separated by the left oblique fissure.

10. Platelets are not actually cells, but rather fragments of cells. They are fragments of megakaryocytes, giant cells within bone that fragment, releasing platelets into the blood.

11. Calot’s triangle (also, cystohepatic or hepatobilliary triangle) is an anatomical space bordered medially by the common hepatic duct, laterally by the cystic duct and superiorly by the inferior margin of the liver. The triangle contains the cystic artery and Mascagni’s lymph node (or Lund’s lymph node).

12. The kidneys are retroperitoneal organs located in the abdominal cavity in the paravertebral gutters. They lie at a slightly oblique angle and, due to the asymmetry caused by the liver, the right kidney lies lower than the left. The left is approximately at T12-L3.

13. Gerota’s fascia is a layer of connective tissue encapsulating the kidneys and suprarenal glands.

Anteriorly, called fascia of Toldt, it passes anterior to the kidney, renal vessels, abdominal aorta and inferior vena cava and fuses with the anterior layer of the renal fascia of the other kidney.

Posteriorly, called Zuckerkandl’s fascia, it fuses with the fascia of the psoas major muscle and bodies of the vertebrae.

Superiorly, the anterior and posterior layers fuse at the upper pole of the kidney, split to enclose the suprarenal gland, and then fuse again. At this upper part, the layers form the suspensory ligament of the suprarenal gland and fuse with the fascia of the diaphragm.

Inferiorly, the layers don’t fuse. The posterior layer continues inferiorly to fuse with the iliac fascia and the anterior layer blends with the fascia of the iliac fossa.

14. Kraissl’s lines on the skin are used by surgeons to make incisions as non-traumatic/least scarring as possible. Cuts should be made parallel to them.¬†They are lines of maximum skin tension¬†in vivo (as opposed to Langer’s lines, which correspond to¬†collagen fiber orientation in cadavers).¬†Borges referred to ‚Äúrelaxed skin tension lines‚ÄĚ, which¬†disappear in a relaxed state, in contrast to wrinkles.

15. Bichat’s fat pad is one of several fat masses in the cheek. It is deep, and lies between the buccinator and masseter muscles.

16. The foramen lacerum is a gap between the sphenoid, temporal pars petrosa, and occipital bones. It is filled by the fibrocartilaginoussphenopetrous synchondrosis.

A synchondrosis is a cartilaginous joint uniting bones (the cartilage can by fibrocartilage or hyaline).  Although the foramen lacerum is covered in such cartilage, there are openings through which these main structures pass:

    • Greater petrosal n. from CNVII
    • Lesser petrosal n. from CNIX

17. Glisson’s capsule covers the liver, even over the bare area. It is composed of collagen¬†type III and mesothelial cells with sensory innervation. It extends into the liver, forming a sheath around the main structures there, including hepatic ducts, hepatic arteries, portal tributaries.

18. The celiac trunk (vertebral level = Th12) is the first branch of the abdominal aorta. It supplies structures that have developed from the embryonic foregut. Its main branches are:

    • L. Gastric a.
    • Common Hepatic a.
    • Splenic a.

19. Behold the fallopian (uterine) tube (aka oviduct)! unnamedIt has four parts, from lateral to medial: infundibulum, ampulla, isthmus and uterine part.

In cross section, the ampulla has an irregular labyrinthic lumen with numerous folds. A distinguishing feature is the peg/pin cell in the epithelium of the tunica mucosa. These cells are degenerating secretory cells with characteristic dark, long nuclei and a cell body shaped like an inverted pyramid.

20. The mandibular division of the trigeminal nerve is composed of both motor and sensory fibers. It leaves the middle cranial fossa through the foramen ovale and enters the infratemporal fossa on the external aspect of the base of the skull.

Its sensory branches are: auriculotemporal, lingual, inferior alveolar (also has motor) and buccal.

Its motor branches are: masseteric, deep temporal nerves, pterygoid nerves, nerve of the tensor tympani muscle and nerve of the tensor veli palatini muscle.

21. The nerve terminals of the paraventricular and supraoptic hypothalamic nuclei release two peptide hormones into the posterior pituitary lobe:oxytocin, by the paraventricular nucleus and ADH, by the supraoptic nucleus.

The axons from both nuclei pass through the pituitary stalk and are stored in vesicles called Herring bodies. These are stored in the cell bodies and then carried to the posterior lobe by antegrade axoplasmic transport.

22. Arterial blood supply to the spinal cord is derived from both vertical and horizontal components. The vertical system consists of the unpaired anterior spinal arteries and the paired posterior spinal arteries. The spinal arteries arise intracranially from the vertebral arteries (though the posterior spinal arteries may also arise from PICA.

The spinal arteries receive reinforcing contributions from the anterior and posterior segmental medullary arteries. These arise from spinal branches of vertebral, ascending cervical, deep cervical, posterior intercostal, lumbar, and lateral sacral arteries. They vary in their level of origin and number, but average 8 anterior and 12 posterior.

At all other vertebral and spinal cord levels, small radicular arteries arise from the spinal branches and supply ventral and dorsal nerve roots. These do not reach or contribute to the spinal arteries.

23. One of the segmental medullary arteries is significantly larger than the others and reinforces the blood supply to approx. ‚ÖĒ of the cord. It is called the¬†segmental medullary artery of Adamkiewicz. It arises from the left in 65% of individuals, typically at T12/L1, but may arise anywhere between T7-L4.

24. The basal ganglia are subcortical nuclei of the telencephalon that have a role in the planning and execution of movements. They are the central relay station of the extrapyramidal motor system and make up almost all of the central gray matter or the cerebrum. The only other central grey matter is the thalamus, which is mainly sensory and is only involved through feedback mechanisms.

The three nuclei of the basal ganglia are: caudate nucleus, putamen andglobus pallidus.

They are sometimes referred to as: lentiform nucleus: putamen and globus pallidus or the corpus striatum: putamen and caudate nucleus.

25. The retina is composed of 9(10) layers (from out to in):

    1. Pigment epithelium
    2. Processes of photoreceptor cells
    3. Outer limiting membrane
    4. Outer nuclear layer (nuclei of photoreceptor cells)
    5. Outer plexiform layer
    6. Inner nuclear layer (nuclei of bipolar cells)
    7. Inner plexiform layer
    8. Nuclei of ganglion cells
    9. Nerve fiber layer
    10. Inner limiting membrane

26. Deep in the adipose tissue of the posterior femoral region we can find the ascending posterior femoral subcutaneous branch of the small saphenous vein, termed the vein of Giacomini. This vessel is present in about one third of all cases, either as a continuation of the small saphenous vein or as a side branch of the subcutaneous vein. It passes anteriorly to join to the great saphenous vein or the femoral vein.

27. The retropharyngeal space extends behind the posterior wall of the pharynx to the deep cervical fascia and is laterally related to the parapharyngeal space. It starts from the base of the skull and is continuous with the posterior mediastinum. It contains loose connective tissue, 2-3 retropharyngeal lymph nodes located immediately below the cranium, and small veins from the pharyngeal plexus.

The practical importance of the perivisceral spaces of the neck (parapharyngeal, retropharyngeal and retroesophageal) is their potential role in the transmission of pharyngeal inflammation or absesses, which can transmit to the posterior mediastinum.

28.The leptomeninx of the CNS are the arachnoid mater and pia mater, which are connected by the arachnoid trabeculae. The arachnoid is avascular, while the pia is highly vascular.¬†( “Lepto” is Greek for “thin”; “pia mater” is Latin for tender mother; “dura mater” means tough mother; “arachnoid mater” is named for its spider-web appearance.)¬†Arachnoid granulations (villi) protrude from the arachnoid through the dura into the venous sinuses. CSF can thus flow from the subarachnoid into venous circulation. Large arachnoid granulations, such as those going into the superior sagittal sinus, are also called “Pacchionian bodies” after the Italian anatomist.

29. The spinal cord has 2 enlargements along its ~45 cm length. These “intumescences” or “swellings” are due to increased nerve supply in the plexuses for the upper and lower extremities.

    • cervical/brachial intumescence is from C5-T1
    • lumbosacracal intumescence is from L1-S2

30. The submandibular ganglion lies together with several small secondary ganglia in the floor of the mouth, above the submandibular gland and below the lingual nerve, to which it connects with several ganglionic branches. It receives PSY fibers from the superior salivatory nucleus originating from the facial nerve. These PSY fibers leave the facial nerve to join the taste fibers of the chorda tympani. The chorda tympani joins the lingual nerve and extends into the floor of the mouth, where the fibers then cross over into the ganglion. (So, the path of the PSY fibers: superior salivatory nucelus > facial nerve > chorda tympani > lingual > submandibular ganglion.) The ganglion aslo receives SY fibers from the plexus of the external carotid artery, which reach the ganglion via the sympathetic branch, which is given off by the plexus of the facial artery. The SY fibers pass through the ganglion without synapsing.

Postganglionic PSY fibers and preganglionic SY fibers ¬†pass partly in the glandular branches to the submandibular gland, partly in the lingual nerve to the sublingual gland and to the glands of the distal ‚ÖĒ of the tongue.

31. The flocculonodular lobe of the cerebellum, together with the lingula, make up the oldest portion of the cerebellum – the archicerebellum. Functionally, it is connected to the vestibular nuclei through the vestibulocerebellar tracts.

32. The substantial gelatinosa of Rolando (the central sulcus of the brain is also named after him!) is at the tip of the posterior horn of spinal cord gray matter. It transmits and filters sensation of pain. Unmyelinated afferent (C-type) fibers terminate here, as well as first order neurons of the spinothalamic tract.

33. The stria vascularis of the cochlear duct is unique because it is the only vascular epithelial tissue, i.e. it has capillaries and other small vessels. It produces endolymph, an extracellular fluid with high [K+] (!) that flows in the membranous labyrinth.

34. The ductus venosus of Arantius is a fetal shunt from the left umbilical v. to the IVC, bypassing the liver. The umbilical vein carriesoxygenated blood from the mother. About one week after birth, the ductus venous closes to become the fibrous ligamentum venosum, located on the base of the liver, attached to the portal vein.

35. The left renal vein is generally longer than the right due to inferior vena cava’s location on the right side of the body. ¬†Another consequence of this asymmetry is that the renal vein receives the blood of several veins (which drain directly into the IVC on the right side): left inferior phrenic, left suprarenal, left gonadal (testicular or ovarian) and left 2nd lumbar.

36. The carotid sheath, part of the deep cervical fasica, is fibrous connective tissue formed by three major fascial layers: the investing fascia, pretracheal fascia and prevertebral fascia. It is located at the lateral boundary of the retropharyngeal space, at the level of the oropharynx and deep to the sternocleidomastoid muscle, and extends from the base of the skull to the first rib and sternum. It contains the internal carotid artery, internal jugular vein, vagus nerve and deep cervical lymph nodes. The carotid artery lies medial to the internal jugular vein and the vagus posterior to the two vessels. In the cranial part of the sheath, the contents also include the glossopharyngeal nerve, the accessory nerve, and the hypoglossal nerve. The anterior wall of the sheath also contains the deep ansa cervicalis, which is formed by C1, C2 and C3.  

37. The spermatic cord is a cord-like structure in males formed by the vas deferens and surrounding tissues that runs from the deep inguinal ring through the inguinal canal and superficial inguinal ring and down to each testicle. It contains “3 arteries, 3 nerves, 3 other things”: testicular artery, artery to the ductus deferens, cremasteric artery, genital branch of genitofemoral nerve, cremasteric, symptathetic nerves, vas deferens, pampiniform plexus, and lymphatic vessels.

38. The scrotum has 7 layers, from deep to superficial:

      1. Tunica vaginalis (visceral layer)/epiorchium
      2. Tunica vaginalis (parietal layer)/periorcium (from peritoneum)
      3. Internal spermatic fascia (from tranversalis fascia)
      4. Cremaster muscle and its fascia (from internal oblique muscle)
      5. External spermatic fascia (from external oblique muscle)
      6. Skin with dartos fascia

39. The neurovascular structures that pass through the foramen magnum are:

      1. Meninges
      2. Medulla oblongata, spinal cord
      3. Vertebral arteries
      4. Anterior spinal artery
      5. Posterior spinal arteries
      6. Accessory nerve (CN XI): spinal roots
      7. Spinal vein

40. The otic ganglion is located medial to the mandibular nerve just inferior to the foramen ovale. Sensory and motor fibers exit the foramen ovale and pass through the flat body of the ganglion without synapsing.

    • Preganglionic PSY fibers originate from the inferior salivatory nucleus. They run in the glossopharyngeal nerve and branch off, together with the tympanic nerve, from the inferior ganglion of the glossopharyngeal nerve in the fossula petrosa to the tympanic cavity. The fibers leaves the tympanic cavity through the hiatus for the lesser petrosal nerve as a fine branch, the lesser petrosal nerve (PSY root). The nerve runs beneath the dura mater along the surface of the petrous bone and reaches the otic ganglion after passing through the foramen lacerum. The postganglionic fibers leave the otic ganglion via a communicating branch to enter the auriculotemporal nerve and then pass to the facial nerve via another anastomosis. The fibers ramify in the parotid gland with the branches of the facial nerve. They supply the buccal and labial glands via the buccal nerve and inferior alveolar nerve.¬†(Path of PSY is:¬†Inferior salivatory nucleus > glossopharyngeal nerve > inferior ganglion > tympanic nerve > lesser petrosal nerve > otic ganglion > communciating branch > auriculotemporal nerve > facial nerve.)
    • Fibers of the SY root originate from the plexus of the middle meningeal artery.
    • Motor fibers from the motor root of the trigeminal nerve pass through the ganglion and leave it in the nerve to tensor veli palatini and the nerve to the tensor tympani.
    • Motor fibers for the levator palatini run from the facial nerve through the communciating branch with the chorda tympani into the ganglion. They leave the ganglion without synapsing in a comminucating branch that connects them to the greater petrosal nerve. They then enter the pterygopalatine ganglion via the greater petrosal nerve. (Path of levator palatini motor fibers: facial nerve > communicating branch with chorda tympani > otic ganglion > comminicating branch > greater petrosal nerve > pterygopalatine ganglion.)

41. The thymus is a primary lymphatic organ derived from the pharyngeal pouches. During week 6, the paired primordia begin to migrate from the 3rd pouch down to the mediastinum behind the sternum.

The two lobes are epithelial of endodermal origin, and become invested with a capsule of connective tissue derived from the neural crest. The involvement of neural crest cells is required for the development of the thymus.

The process is complete by week 15, resulting in the mature thymus lymphatic us. After puberty, the parenchyma of the thymus is replaced by adipose tissue, forming the so-called thymus adiposus.

42. Quadratus plantae is a muscle of the sole of the foot that originates as medial and lateral heads from the plantar surface of the calcaneus; it inserts into the lateral margins of flexor digitorum longus (FDL) tendon.

It is innervated by the lateral plantar nerve branch of the tibial nerve.  Quadratus plantae assists FDL in toe flexion and straightens the oblique vector of its tendon.

Quadratus plantae, FDL tendons, and the lumbricals make up the second muscular layer of the plantar region (the first muscle seen more superficially is flexor digitorum brevis).

43. The lateral lingual sulcus is between the mylohoid (lateral) and the hyoglossus (medial) muscles.  It contains:

    • Lingual nerve
    • Submandibular duct
    • CN XII Hypoglossal nerve

44. Contraction of the risorius, a muscle of facial expression, is one cause of dimples. Its origin is the fascia of the face and parotid, and it inserts into the skin at the angle of the mouth.

Dimples may also be caused by contraction of zygomaticus major, which originates from the zygomatic arch and inserts at the skin of the angle of the mouth. ¬†Contraction of the zygomaticus ¬†occurs with a “genuine” smile that also causes crinkles by the eye.

These two muscles, along with the other facial muscles around the mouth, insert into an area of the face called the modiolus, where several facial muscles are held together by fibrous connective tissue.

45. In the larynx, the¬†ventricle¬†or sinus of Morgagni is the bilateral recess below the¬†vestibule, between the ventricular (superiorly) and vocal (inferiorly) folds (=vocal cords). ¬†The ventricular/vestibular vocal fold is also called the “false” vocal cord because it is not involved in vocalization.

46. The median umbilical ligament is attached to the anterior abdominal wall, apex of the bladder, and umbilicus. It forms the median umbilical fold. The ligament is a remnant of the urachus, a part of the allantois, which helps in ridding the embryo of waste products.

47. The foramen of Magendie (median ventricular aperture) opens from the 4th ventricle to the subarachnoid cisterna magna (=cisterna cerebellomedullaris).
The lateral apertures, Luschka foramina, open from the 4th ventricle into the cistern ambiens.

48. Borders of the popliteal fossa:

    • superior medial: semitendinosus, semimembranosus
    • inferior medial: gastrocnemius, medial head
    • superior lateral: biceps femoris
    • inferior lateral: gastrocnemius, lateral head
    • floor: popliteus, capsule of knee joint

49.  The greater petrosal nerve arises directly at the geniculate ganglion. It leaves the anterior surface of the petrous pyramid at the hiatus of the canal for the greater petrosal nerve. It continues through the foramen lacerum, enters the pterygoid canal and passes to the pterygopalatine ganglion. It carries presynaptic parasympathetic fibers from the superior salivatory nucleus via the facial nerve.

50. The pterygoid canal (Vidian canal) transmits the following structures:

    • greater petrosal nerve (PSY branch of the facial nerve)
    • deep petrosal nerve (SY fibers from the carotid plexus)
    • artery of the pterygoid canal with accompanying veins
    • nerve of pterygoid canal

51. Borders of the pterygopalatine fossa:

    • Anterior: maxillary tuberosity
    • Posterior: pterygoid process
    • Medial: perpendicular plate of the palatine bone
    • Lateral: infratemporal fossa (via pterygomaxillary fissure)
    • Superior: greater wing of the sphenoid bone, junction with the inferior orbital fissure
    • Inferior: retropharyngeal space

52. The bony nasal septum is formed by the nasal bone (roof of the septum), ethmoid bone, vomer, sphenoid bone, palatine bone and maxilla. The latter three contribute only small bony projections to the nasal septum.

53. There are four structures that open into the middle nasal meatus: frontal sinus, maxillary sinus, anterior ethmoid cells and middle ethmoid cells.

54. The temporomandibular joint capsule is supplied by articular branches arising from three branches of the mandibular division of the trigeminal nerve: auriculotemporal, deep temporal and masseteric nerves.

55. The temporomandibular joint is surrounded by a lax capsule that permits physiological dislocation during jaw opening. The joint is stabilized by 3 ligaments: lateral ligament (strongest), stylomandibular ligament and sphenomandibular ligament.

56. The branches of the external carotid artery are:

  • Anterior
    • Superior thyroid artery
    • Lingual artery
    • Facial artery
  • Medial
    • ascending pharyngeal artery
  • Posterior
    • occipital artery
    • posterior auricular
  • Terminal
    • maxillary artery
    • superficial temporal artery

57. The internal carotid artery has four parts:

    1. Cervical part
    2. Petrous part – traverses the carotid canal
    3. Cavernous part – traverses the cavernous sinus
    4. Cerebral part

58. The lateral pterygoid muscle has two parts and two functions. Its superior part extends from the infratemporal crest (greater wing of the sphenoid bone) to the articular disk of the temporomandibular joint. Its inferior part extends from the outer surface of the lateral plate of the pterygoid process to the condylar process of the mandible. Its first action – bilateral contraction – initiates mouth opening by protruding the mandible and moving the articular disk forward. The second action – unilateral contraction – elevates the mandible to the opposite side during mastication. The muscle is innervated by the lateral pterygoid nerve, a branch of the mandibular division of the trigeminal nerve.

59. The arteries of the nasal septum arise from branches of the external and internal carotid arteries. The anterior part of the septum contains a highly vascularized area called Kisselbach’s plexus, which is supplied by vessels from both major arteries. This is the most common site of nosebleeds. The arteries supplying the septum are: anterior ethmoidal artery (with anterior septal arteries) and posterior ethmoidal artery from the opthalmic artery (a branch of the internal carotid artery) and posterior septal branches from the sphenopalatine artery (a branch of the maxillary artery, from the external carotid).

60. The blood-brain barrier in normal brain tissue consists mainly of the tight junctions between the capillary endothelial cells. It prevents paracellular diffusion of hydrophilic substances from CNS capillaries into surrounding tissues. Essential hydrophilic substances that are needed by the CNS must be channeled through the barrier with the aid of specific transport mechanisms. It is absent at fenestrated capillary endothelial cells in the choroid plexus and the circumventricular organs. Tight junctions in the overlying ependyma of these regions do, however, create a two-way barrier between the brain tissue and ventricular CSF. This means that the diffusion barrier is shifted from the vascular endothelium to the cells of the ependyma and choroid plexus.

61. The duodenum is characterized by mucoserous, branched tubular¬†Brunner’s glands ¬†located in the submucosa. They are not found elsewhere in the small intestine.

62.¬†Chief (=zymogenic) cells¬†of the¬†stomach¬†fundus secrete pepsinogen. They are located in the basal part of the¬†funds glands and stain darkly basophilic due to an abundance of rough ER.¬†Parietal (=oxyntic) cells¬†are found in the body of the gland.¬†Parietal cells are eosinophilic with a “boiled egg nucleus”. These cells secrete HCl and a so-called intrinsic factor that is necessary for vitamin B12¬†binding and absorption (vitamin B12 was originally known as “extrinsic factor”).¬†Pernicious anemia is an autoimmune disease where antibodies¬†destroy intrinsic factor or¬†parietal cells.

63. In general, the layers of the GI tract are:

I. Tunica Mucosa: a. Epithelium Mucosae, b. Lamina Propria Mucosae, c. Lamina Muscularis Mucosae

II. Tela Submucosa = connective tissue

III. Tunica Muscularis:  a. Tela Subserosa, b. Tunica Serosa

(If the organ is not covered by peritoneum, layer III is Tunica Adventitia)

64. The¬†tunica¬†muscularis of the esophagus is different along the length of the organ: there is striated muscle in the upper¬†‚Öď; mixed striated and smooth muscle in the middle¬†‚Öď; smooth muscle in the lower¬†‚Öď.

65. The triangular space of the deltoid region is also known as the “medial axillary hiatus“. It contains the circumflex scapular artery. ¬†Its borders are –¬†lateral: triceps long head,¬†superior:¬†teres¬†major, inferior: teres minor

66. The arytenoid cartilage of the larynx has medial, lateral, and posterior surfaces, and a base and apex since it is pyramidal. At the apex are the 2 corniculate cartilages of Santorini; sometimes they are fused to the arytenoid cartilage.

67. The descending tracts in the spinal cord convey information from higher motor centers to the motor neurons in the spinal cord. The lateral system includes the pyramidal and rubrospinal tracts and the medial includes the reticulospinal, tectospinal and vestibulospinal tracts.

68. Mossy fibers are the axons of neurons of the pontine nuceli, the spinal cord and vestibular nuclei (pontocerebellar, spinocerebellar and vestibular tracts).

69. The vestibulocochlear nerve has 6 nuclei. The vestibular part includes: medial, superior, lateral and inferior vestibular nuclei. The cochlear part includes: anterior and posterior cochlear nuclei.

70. The subthalamus is located at the junction of the midbrain and diencephalon. It contains ascending (i.e. sensory) and descending (i.e. motor) fibers from the cerebellum; both terminate in the thalamus. It has several areas, including:

  • H fields of Forel (H1, H2)¬†– white matter tracts from the globus pallidus
  • Zona incerta¬†– grey matter, reticular formation
  • Subthalamic nuclei¬†– reciprocal connection with the globus pallidus

71. Renshaw cells (named after Birdsey Renshaw; what a fun name!) are inhibitory interneurons that fine-tune motoneuron activity. Their neurotransmitter is glycine.

72. The portal triad of a hepatic lobule consists of:

a. interlobular vein, a branch of the portal vein
b. interlobular artery, a branch of the proper hepatic artery
c. interlobular common bile duct

Although called a “triad”, it also contains lymph vessels and branches of CNX.unnamed

73. The nasopharynx (or epipharynx) starts from the basilar part of the occipital bone and continues to the soft palate. It communicates anteriorly with the choanae and inferiorly with the oropharynx. Superiorly, it communicates with the roof of the pharynx, which opens into the tympanic cavity through theauditory tube or ostium pharyngeum tubae auditivae. Behind this opening is the tubal elevation or torus tubarius, which is formed by the cartilaginous part of the tube. From this elevation, there are two folds: posteriorly, thesalpingopharyngeal fold, containing the salpingopharyngeus muscle, and anteriorly, the smaller salpingopalatine fold, containing some fibers of thesalpingopalatine muscle and connecting to the hard palate. Above the tubal elevation is an area called the pharyngeal recess. This is where the tubal tonsils Рpart of the Waldemyer ring Рare located. The pharyngeal tonsils can be found in the fornix of the pharynx, which is between the superior and posterior walls.

74. The anterior and posterior ethmoidal foramina connect the orbit to the middle cranial fossa and the posterior ethmoidal air cells, respectively. The anterior transmits the anterior ethmoidal artery, nerve and vein and the posterior transmits the posterior ethmoidal artery, nerve and vein.

75. The semilunar hiatus is a crescent-shaped hiatus located between the bulla ethmoidalis and the uncinate process in the middle nasal meatus of the nasal cavity. It connects to the frontal sinus anteriorly, the anterior and middle ethmoidal air cells laterally and to the maxillary sinus (also known as the antrum of Highmore) posteriorly.

76. The mandibular canal is the main structure of the mandible. It runs from the foramen mandibulae, which is located on the inner surface of the ramus, and to the foramen mentale on the outer surface of the mandible. It transmits the inferior alveolar nerve and arteyr. The mylohyoid sulcus runs behind the mandibular foramen and transmits the mylohyoid nerve.

77. The foramen mandibulae is covered by a tiny lingula called the lingula mandibulae.

78. The sublingual caruncle is the common opening of the submandibular and sublingual glands. It is located lateral to the frenulum linguae.

79. At the ileocecal junction, the ileocecal valve of Bauhin marks the  connection of the ileum of the small intestine to the cecum of the large intestine. The cecum is a blind pouch located in the right lower iliac fossa, semi-intraperitoneally.

80. The Hilton white line, aka the intersphincteric groove, marks the transition between the non-keratinized, squamous stratified epithelium of the anal canal and the keratinized,  squamous, stratified epithelium of the surrounding skin.

81. This is different from the pectinate line, which separates the junction part of the superior anal canal derived from the hindgut from the inferior part derived from the proctodeum. The blood supply and innervation differ above and below this line:

    • superior rectal a. and v. above the line
    • inferior rectal aa. and v. below the line
    • inferior hypogastic plexus (sympathetic and parasympathetic) is¬†superior¬†to the pectinate line; sensitive to stretch only, which is why deep hemorrhoids are not painful.
    • inferior rectal nerves from the pudendal nerve are¬†inferior¬†to the pectinate line; sensitive to pain, touch, temperature

82. The inguinal ligament is the thickened aponeurosis of the external oblique muscle that stretches from the ASIS to the pubic tubercle. It forms the floor of the inguinal canal.

83. The anterior cranial fossa is made up of the ethmoid and frontal bones. It is separated from the middle cranial fossa by the lesser wings of the sphenoid. Olfactory nerves pass through the cribriform plate of the ethmoid bone, which is in the center of the anterior cranial fossa. The crista galli projects sagittally from the cribriform plate.

84. The cerebral falx is anchored to the crista galli anteriorly. It is a fold of dura mater located in the longitudinal fissure between the cerebral hemispheres. Posteriorly, it is continuous with the tentorium cerebelli, another dural fold.

85. The inferior vena cava develops from several segments:

    • hepatocardiac segment from the right vitelline vein (from the liver, known as¬†revehent veins)
    • prerenal segment from the right subcardinal vein
    • renal segment from the anastomosis between the right subcardinal and supracardinal veins
    • postrenal segment from right supracardinal vein.

86. The parotid gland is innervated by the great auricular nerve, glossopharyngeal nerve and the external carotid nerve plexus. The greater auricular is a branch of the cervical plexus and innervates the parotid sheath and overlying skin. The glossopharyngeal nerve supplies parasympathetic fibers to the gland and the external carotid nerve plexus supplies sympathetic nerve fibers.

87. The epithelium of the nasopharynx is continuous with the epithelium of the nasal cavity, ciliated respiratory epithelium. The epithelium of the oropharynx and laryngopharynx are continuous with the mucosa of the oral cavity, stratified, non-keratinized squamous epithelium.

88. The infrahyoid muscles are four strap-like muscles that anchor the hyoid bone. The sternohyoid depresses the hyoid, the sternothyroid depresses the thyroid cartilage, the thyrohyoid elevates the thyroid and depresses the hyoid bone and the omohyoid depresses the larynx and hyoid bone. The thyrohyoid is innervated by the hypoglossal nerve and the other three by the ansa cervicalis.

89. The occulomotor nerve has 2 nuclei:

    • The¬†occulomotor nucleus¬†at the level of the superior colliculus in the central gray matter has¬†somatomotor¬†function to supply¬†levator palpebrae superioris and extrinsic eye muscles (all except the lateral rectus and superior oblique).
    • The¬†Edinger-Westphal accessory nucleus¬†is also in the midbrain. It has¬†parasympathetic¬†(general visceromotor) function, with presynaptic fibers to the ciliary ganglion for innervation of the ciliary muscles and sphincter¬†pupillae.

90. The musculotubarian canal can be demonstrated from the external base of the skull as a canal beginning at the junction of the petrous and squamous parts of the temporal bone, passing to the tympanic cavity. It contains the semicanal for the auditory tube and the semicanal for the tensor tympanic muscle.

91. The omoclavicular (supraclavicular) triangle is bound by the clavicle, the inferior belly of the omohyoid, sternocleidomastoid, and the floor is the first rib.

It contains the trunks to the brachial plexus, subclavian artery and vein, suprascapular artery, and suprascapular lymph notes.

92.  The genioglossus is the only muscle that protracts the tongue. It is innervated by CNXII.

93. The carotid triangle is one of the ventrolateral cervical regions. The boundaries are: the sternocleidomastoid, the omohyoid, and the posterior belly of the digastric.

94. The muscles of the scalp, the occipitofrontalis and temporoparietalis, constitute the epicranius. This is very loosely bound to the periosteum but firmly to the scalp. The epicranial aponeurosis is a taut tendon that stretches between the anterior and posterior bellies. The temporoparietal muscles arise from this aponeurosis.

95. Bones preformed in cartilage include the occipital bone (except the upper part of its squama), the sphenoid bone (except the medial lamella of the pterygoid process), the temporal bone with its petrous part and the auditory ossicles, the ethmoid bone, the inferior nasal concha and the hyoid bone.

96.  Sometimes, the upper squama of the occipital bone may be present as a separate bone, the incarial bone. The term is derived from the word Inca, because it has frequently been found in old Peruvian skulls.

97. The sternoclavicular joint of the shoulder girdle functions as a synovial ball-and-socket, with the bulbous medial end of the clavicle inserting into the superolateral manubrium of the sternum and the cartilage of the first rib. There is a fibrocartilaginous articular disk separating the joint into two cavities.

98. The serous cells of  the submandibular gland form semilunar caps called serous demilunes of Gianuzzi that surround the terminal part of the mucous acini. Secretion by the submandibular gland is merocrine.

99. The fate of the 6th pharyngeal arch is closely tied to the larynx: the intrinsic laryngeal muscles except the cricothyroid (which is from the 4th arch), the cricoid, arytenoid, and corniculate cartilages, and recurrent laryngeal nerve all develop from the 6th arch.

100. The cardiovascular system is the 1st organ system to reach a functional state in utero. Fetal heartbeat begins around the end of week

101. The scalene muscles represent the cranial continuation of the intercostal muscles. They arise from the vestigial ribs of the cervical vertebrae. They are the most important muscles for quiet inhalation, since they lift the first two pairs of the ribs and therefore the superior part of the thorax. Their action is increased when the head is bent backward. Unilateral contraction tilts the cervical column to one side. They include the scalenus anterior, from C4-C6 to the anterior scalene tubercle of the first rib, the scalenus medius, from C2-C7 to the first rib behind the groove for the subclavian artery, and the scalenus posterior, from C5-C7 to the 2nd (3rd) rib. The scalenus posterior can be absent and occasionally there is a scalenus minimus muscle arising from C7 and joining scalenus medius. All of the muscles are innervated by the brachial plexus, the scalenus medius is additionally supplied by the cervical plexus.

102. The mentalis muscle arises from the mandible in the region of the alveolar jugum of the lateral incisor and radiates into the skin of the chin. It produces the chin-lip furrow and is responsible for an expression of doubt and indecision.

103. The orbicularis oris appears like a circular muscle, but it is in fact four parts. It also has an inner labial and outer marginal part. The shape of the mouth is determined by its tone and the shape of the underlying bone and teeth. In weak contraction the lips are in contact or closed, while in strong contraction they pout forward and protrude in a sucking shape. The main function of this muscle is best seen in eating and drinking.

104. In the event of respiratory obstruction, a coniotomy is used as an emergency measure. A transverse incision is made at the median cricothyroid ligament, the free portion of the elastic cone of the larynx. This causes gapping of the incision.

105. The arcuate line of Douglas (linea semicircularis) marks the inferior limit of the posterior layer of the rectus sheath. It is a horizontal crescent just below the level of the iliac crest.

It is not to be confused with the linea semilunaris, which is a vertical crescent marking the lateral border of the rectus abdominis. 

106. The¬†cutaneous innervation of the nuchal region¬†is provided by the ¬†lesser occipital,¬†greater occipital, and third occipital nerves(aka the “least” occipital nerve, poor nerve). ¬†¬†

The lesser occipital nerve is part of the cervical plexus from C2 and C3. The greater occipital nerve is a dorsal branch of C2, and the third occipital nerve is a dorsal branch of C3.

107. The¬†ascending pharyngeal artery¬†is the¬†smallest¬†branch of the external carotid artery (apparently that’s my theme for the day). It ascends between the¬†pharynx and the internal carotid artery on¬†longus¬†capitis¬†to the external base of the skull. It supplies stylopharyngeus and the middle pharyngeal constrictors.

108. The olfactory tract lies in the olfactory sulcus, contains the anterior olfactory nucleus, and divides into the lateral, medial, and intermediate olfactory stria. The lateral olfactory stria projects to the piriform cortex, which in turn projects to the thalamus (medial dorsal nucleus), hypothalamus, and hippocampal formation.1.

109. Mast cells are often stained with toluidine blue. They are large cells (20-30 micron) with an oval shape and poorly stained nucleus with prominent nucleolus.
Their characteristic histological feature is metachromasia of the cytoplasmic granules. Metachromasia is process by which a stained material takes on a different color than the applied dye. In this case, the densely packed basophilic granules rich in histamine stain red-violet instead of blue.
mast cell
110.¬†Secondary retroperitoneal¬†organs include the pancreas and the duodenum from the superior flexure to the duodenojejunal flexure. They are “secondary” retroperitoneal because they were originally intraperitoneal during development.

111. The azygos vein drains the posterior wall of the thorax and the abdominal wall.  It is formed by the union of the ascending lumbar veins and right subcostal veins at the level of T12, and drains into the superior vena cava from behind (i.e. on the right side of the body).  It can sometimes provide an alternative path for blood to enter the right atrium if one of the venae cavae is blocked.
It produces an impression on the right lung on its way.
The hemiazygos vein is on the other side of the vertebral column, and drains into the azygos vein.

The word “azygos” is of Greek etymology and refers to the unpaired nature of this vein.

112. The mediastinum is the space in the thoracic cavity between the lungs. It is bound anteriorly by the sternum, posteriorly by the vertebral column, superiorly by the thoracic inlet, and inferiorly by the diaphragm. The root of the lung and pulmonary ligament divide the mediastinum into anterior and posterior. The anterior mediastinum can further be divided into cardiac and supracardiac parts.

113. . The pancreas is 98% exocrine, 2% endocrine organ. Its endocrine functions have to do with hormones, i.e. insulin, glucagon, and somatostatin.  Islets of Langerhans (more prevalent in the tail) have A cells (glucagon synthesis), B cells in the center (insulin synthesis) and D cells (only seen with special stain, somatostatin secretion).

The exocrine functions involve secretion of pancreatic juice for digestion of carbohydrates, proteins, and fats. The secretory units are acini, composed of serous acinar cells. 

114. ¬†The¬†gall bladder¬†has no submucosa or¬†muscularis mucosa! The epithelial mucosal is simple columnar with microvili forming a “brush border. Under light microscope, the brush border is also referred to as “cuticle”

115.  The periportal hepatic lobule (Acinus of Rappaport) is thepathologic functional unit of the liver. It is rhomboid with the portal triad located centrally. Zone I is around the portal triad, with high enzyme and oxygen concentrations; moving outward, Zone II is intermediate, and Zone III receives the least oxygen and is therefore most susceptible to hypoxia.

116. The ureter is part of several crossings:

    • over psoas major and genitofemoral n.
    • behind testicular/ovarian a. & v.
    • over common iliac a.
    • behind ductus deferens/uterine a.

117. The anterior cervical region is bounded by the mandible superiorly, the sternocleidomastoid laterally, and the midline of the neck. It is subdivided into 4 triangles: the submandibular, submental, carotid, and muscular triangles.

118. The medial inguinal fossa is between the medial and lateral umbilical folds. The inferior border is the inguinal ligament. Direct inguinal hernias develop here.

119. The lateral umbilical fold covers the inferior epigastric vessels, which are continuations of the external iliac vessels.

120.   Vitelline arteries initially supply the yolk sac. They gradually fuse to form arteries in the dorsal mesentery of the gut. In adults, these are the celiac trunk, superior mesentery, and inferior mesentery artieries.
<——- Grey’s inspired!

121. The thick subcutaneous tissue of the cartilaginous part of the external acoustic meatus contains cerumen glands. These resemble sweat glands and are covered externally by myoepithelial cells. The cerumen glands produce a watery secretion that combines with sebum and sloughed epithelial cells to form cerumen (ear wax), which is protective. It screens out foreign bodies, prevents the epithelium from drying out and prevents maceration of meatal skin by trapped water.

122. The majority of the auricle (of the ear) is firm and supported by elastic fibrocartilage. There is no cartilage in the lobule or between the tragus and the crus of the helix (where the gap is filled by dense fibrous tissue).

123. The auricle is connected to the surrounding parts by ligaments and muscles. There are two sets of ligaments associated with the auricle.

  • Extrinsic ligaments ‚Äď connect the auricle with the temporal bone
    • Anterior ‚Äď extending from the tragus and the spine of the helix to the root of the zygomatic process of the temporal bone
    • Posterior ‚Äď from the posterior surface of the concha to the lateral surface of the mastoid process
  • Intrinsic ligaments ‚Äď connect individual auricular cartilages
    • A strong fibrous band from tragus to helix (completing the meatus anteriorly)
    • A band passing between the antihelix and tail of the helix

124. Extrinsic muscles of the ear connect the auricle to the skull and scalp and move the whole auricle:

o¬†¬†¬†Auriculares anterior¬†‚Äď smallest; thin fan of fibers from lateral edge of epicranial aponeurosis to the spine of the helix

o¬†¬†¬†Auriculares superior¬†‚Äď largest; thin and fan shaped and converges from the epicranial aponeurosis via a thin, flat tendon to attach to the upper part of the cranial surface of the auricle

o¬†¬†¬†Auriculares posterior¬†‚Äď two/three fleshy fasiculi from the mastoid part of the temporal bone to the ponticulus (an oblique ridge) of the eminentia conchae

125. The pretracheal layer of the deep cervical fascia can further be divided into a muscular part, which encloses the infrahyoid muscles, and the visceral part, which encloses the thyroid, trachea, and esophagus. The pretracheal layer thickens to form the trochlea, the tendon through which the digastric passes.

126. The digastric muscle has 2 bellies (as its name literally means!) with different innervations: the anterior belly is innervated by CN V3, while the posterior belly is innervated by CN VII. This is due to their separate embryological origin: the former from the first pharyngeal arch, the latter from the second pharyngeal arch.

127. The carina of the trachea is a cartilaginous ridge between the primary bronchi at the site of tracheal bifurcation at Th5.

128. The¬†rotator cuff¬†shoulder muscles are the supraspinatus, infraspinatus,¬†teres minor, and¬†subscapularis (“SITS”). As a unit, they maintain the stability of the glenohumoral joint, which sits in the relatively shallow glenoid fossa of the scapula. The rotator cuff muscles also allow the movements of abduction and rotation.

129. The stellate ganglion is also called the cervicothoracic ganglion because it is comprised of both the inferior cervical ganglion and the first thoracic ganglion. It is a sympathetic ganglion whose nerves supply the face and arms. It is located in the scalenotracheal fossa below the subclavian artery.

A stellate ganglion block can be injected into the neck to manage pain, sweating, and other sympathetic nerve-induced symptoms.

130. The suboccipital triangle contains the vertebral artery and suboccipital nerve.
Its floor is the atlanto-occipito membrane, its roof is semispinalis.
Medially, it is bordered by rectus capitis posterior major, laterally by obliquus capitis superior, and inferiorly by obliquus capitis inferior.

131. Brain sand (corpora arenacea) is a characteristic of the aging pineal gland. It can be seen in histological specimens as dark blue extracellular bodies of calcified material. Brain sand is used as a radiological landmark because it is so clearly visible.

132. The synergistic extraocular muscle pairs are: superior rectus & inferior oblique (when looking up) and inferior rectus and superior oblique (when looking down).

133. The extraocular muscles are attached to the sclera of the eye and the bony orbit of the skill.

134. BMP4 (bone morphogenic protein 4) permeates the mesoderm and ectoderm of the gastrulating embryo. In the presence of this factor, the ectoderm becomes epidermis and the mesoderm forms intermediate and lateral plate mesoderm. When the ectoderm is protected from exposure to BMPs, it will revert to its default state and become neural tissue.

135. FGF (fibroblast growth factor) represses BMP transcription and upregulates expression of chordin and noggin, which inhibit BMP activity. These two proteins, plus a third, follistatin, are present in the primitive node (the organizer), the notochord and the prechordal mesoderm. As a consequence of their inhibition of BMP, the ectoderm becomes neural tissue; the mesoderm becomes the notochord and paraxial mesoderm. It is important to note that these neural inducers act only on forebrain and midbrain types of tissues. There are other factors involved in more caudal structures.

136.¬†The¬†radiocarpal joint¬†or¬†wrist joint¬†is a biaxial, ellipsoid joint ‚Äď formed on one side by the radius and the articular disk and on the other by the proximal row of carpal bones. Not all of the carpal bones of the proximal row are in continual contact with the socket shaped articular surface of the radius and the disk.

137. The fibrous capsule of the wrist joint attaches to the distal ends of the radius and ulna and the proximal row of the carpals, except for the pisiform. The capsule is lax, relatively thin dorsally, and reinforced by numerous ligaments. The joint space is unbranched and sometimes contains synovial folds.

138. The wrist joint is stabilized by four ligaments:

      1. Palmar radiocarpal ligament¬†‚Äď passes from the distal end of the radius to the scaphoid, lunate and triquetrum (sometimes also the capitate).¬†
      2. Distal radiocarpal ligament¬†‚Äď passes obliquely from the distal radius at Lister‚Äôs tubercle to the dorsal surfaces of the scaphoid, lunate and triquetrum
      3. Ulnar collateral ligament¬†‚Äď passes from the styloid process of the ulna and divides into two parts, one that attached to the medial side of the triquetrum and the other to the pisiform and flexor retinaculum.
      4. Radial collateral ligament¬†‚Äď passes from the styloid process of the radius to the radial side of the scaphoid, with some fibers passing to the trapezium.

139. The scalene hiatus is a triangular space formed by the scalenus anterior and scalenus medius muscles and the first rib. It contains the muscular part of the subclavian artery and the roots of the brachial plexus. Compression of these structures is referred to as thoracic outlet syndrome.

140. The external jugular vein begins at the parotid gland where theretromandibular and posterior auricular veins converge. It runs down the neck at the posterior border of the sternocleidomastoid, which it then crosses. It drains into the subclavian vein next to scalenus anterior.

141. The anterior jugular vein descends in the midline of the neck (usually there are 2, sometimes 1). It begins as a confluence of superficial veins at the level of the hyoid and drains into the external jugular vein.

142. Thyroid hormones are stored extracellularly in thyroid follicles.  These follicles contain a homogenous, eosinophilic colloid material that is secreted by follicular cuboidal epithelial cells. The colloid is the storage form of the thyroid hormones (thyroglobulin, a glycoprotein). In inactive thyroid glands, the follicles are larger with more flattened cuboidal epithelium.

143.¬†Parafolicular C (“clear”) cells¬†are cells found in the¬†interfollicular spaces of the¬†thyroid. They secrete calcitonin, whichtones down¬†calcium levels in the blood.

144. The sphincter of Oddi is a valve that controls the flow of bile through the ampulla of Vater into the duodenum. The sphincter of Oddi surrounds the major duodenal papilla.

145. The ampulla of Vater is the union of the pancreatic duct with the common bile duct, i.e. it drains the pancreas and biliary system.  It marks the border between foregut and midgut.

146. Circular folds of Kerckring (aka plicae circulares) are valvular folds projecting into the small intestine. They increase surface area for absorption.

147. The perisinusoidal space of Disse is between a hepatocyte and a sinuosoid. Hepatocytes absorb compounds flowing through the blood plasma of the space of Disse. The space also contains Ito cells (just at the the level of microscopic resolution), which store vitamin A.

148. Interstitial cells of Leydig are grouped in the spaces between the seminiferous tubules of the  testis in loose connective tissue.

They are endocrine cells producing testosterone. Thus, they contain abundant  smooth ER and tubular mitochondria for steroid synthesis.

149 The rete testis of Haller is a labyrinthic channel system of tubules  embedded in the tunica albuginea. It is lined by simple cuboidal or squamous epithelium.  The tubules carry sperm from the seminiferous tubules to the efferent ducts.

150. Fetal testes contains tubules without lumen and no spermatogenesis. The majority of the cells contain oval, dense nucleus (precursor of Sertoli cells). They do have Leydig cells.

151. Sertoli cells secrete the hormone inhibin, which inhibits FSH synthesis by the pituitary gland. Sertoli cells form the blood-testis barrier: outside the barrier are diploid spermatogonia. Primary spermatocytes pass through this barrier.

152. Layers of the adrenal gland cortex are the following zonae: Glomerulosa (outmost; produces mineral corticoids e.g. aldosterone), Fasciculata (produces glucocorticoids, e.g. cortisol), Reticularis (innermost; produces sex hormones, e.g. androgens).

153. Chromaffin cells can be seen in the adrenal medulla as large cells with prominent nucleoli. The adrenal medulla is a derivative of the neural crest, hence it has direct preganglionic sympathetic innervation.

154. The epithelium of the pharyngeal tonsil is ciliated pseudostratified columnar epithelium infiltrated with lymphoid cells. It has islands of stratified squamous non-keratinizing epithelium on top of the folds and in the pits.

155. Cells migrating from the splanchnic mesoderm form the endocardial tubs, which later becomes the endocaridum. Thickening of the splanchnic mesoderm gives the myoepicardial mantles from which the myocardium, and the visceral layer of the pericardium (epicardium) develop. The intraembryonic celom transforms into the pericardial cavity. The somatic layer of the mesoderm differentiates into the parietal layer of the pericardium.

156. The splenorenal ligament is a peritoneal ligament that contains the splenic artery and vein.

157. The gastrosplenic ligament is a peritoneal ligament that contains the beginning of the left gastroepiploic artery and short gastric arteries.

158. The epiploic foramen of Winslow is the natural mouth of the omental bursa. Its borders are: anterior: hepatoduodenal ligament, posterior: hepatorenal ligament, superior: caudate lobe of the liver, and inferior: duodenorenal ligament.

159. Possible surgical entry points into the omental bursa are: via the lesser omentum, via the greater omentum, or via the transverse colon.

160. The submandibular duct is also known as Wharton’s duct.

161. There are two major types of oral mucosa: lining mucosa has no keratinization and masticatory mucosa has thin keratinization.

162. The root of the mesentery is the line of attachment of the mesentery. It extends from the duodenojejunal flexure to the iliocecal junction. It crosses the inferior part of the duodenum, inferior vena cava, right gonadal vessels, right ureter and psoas major.

163. There are 6 types of cells in the liver: hepatocytes, endothelial cells, Kupffer cells, Ito cells, cholangiocytes and the cells of the connective tissue.

164. Best-carmin staining can be used to visualize the glycogen granules of the hepatocytes.

165. There are 4 regions of portal-caval anastomoses: esophagus, abdominal wall, rectum and retroperitoneum.

166. Vaginal lubrication is achieved through Bartholin’s glands and cervical glands. Before and during ovulation, the cervical mucous glands secrete different variations of mucous, which provides an alkaline environment in the vaginal canal that it favorable to the survival of sperm.

167. The tetralogy of Fallot is a complex cardial malformation. It includes 1) narrowing of the pulmonary valve, 2) thickening of wall of the right ventricle, 3) displacement of aorta over ventricular septal defect, 4) ventricular septal defect, opening between the right and left ventricles.

168. The route of lymph through the lymph node is: vasa afferentia – marginal sinus (subcapsular) – trabecular sinus – medullary sinus – vasa efferentia.

169. The¬†caput medusae¬†(“head of medusa”) is a distention of the paraumbilical veins, which join the systemic veins as one of the¬†portal-caval anastomoses.¬†

This is a pathological  result of portal hypertension: the paraumbilical veins enlarge to reduce pressure in the portal system by shunting blood to the inferior epigastric vein of the systemic system.

170. There are approximately 300 cervical lymph nodes, which can be classified in many ways. A common way is in 7 levels from the submandibular region to the mediastinum.

171. According to Gray’s¬†anatomy, the¬†lymph nodes of the neck¬†can be grouped as:

    • submandibular (3-6)
    • submental (between the anterior bellies of the digastric)
    • superficial cervical (close to external jugular v. and parotid)
    • anterior cervical (anterior to larynx and trachea)

172. The middle gland of Stahr is one of the submandibular lymph nodes (also called lymph glands); it is noteworthy because it is the most constant of them, located on the external maxillary artery where it crosses the mandible. From here, lymph travels to the superior deep cervical glands. 

173. The diaphysis is the shaft of a long bone, usually also containing bone marrow and adipocytes; it is the site of primary ossification. Theepiphysis is the end of a long bone, and is the site of secondary ossification centers. The epiphyseal plate (called epiphyseal line in adults) is hyaline cartilage between the diaphysis and epiphysis. 

174. The histology of the epiphyseal growth plate shows morphological changes from the upper part to the central marrow cavity. The following zones can be seen under the microscope:

  • Resting zone of typical hyaline chondrocytes
  • Zone of proliferation, where dividing chondrocytes form rows and columns
  • Zone of degeneration, where chondrocytes are enlarged and vacuolated.
  • Zone of mesenchymal invasion and ossification, where chondrocytes die and chondroclasts¬†resorb their remnants. Osteoblasts invade!
  • Osteogenic zone with osteoblast and osteoclast activity.

175. ¬†The¬†thyrohyoid¬†muscle is the only¬†infrahyoid muscle not innervated by the ansa cervicalis. Rather, it is innervated by spinal nerve C1 “hitchhiking” on CNXII. Aside from depressing the hyoid, this muscle also elevates the larynx.

176. The external laryngeal nerve is a branch of the superior laryngeal nerve (from CNX) that runs lateral to the larynx. It innervates the cricothyroid muscle (an intrinsic muscle of the larynx), which tenses vocal cords. It is the nerve most commonly damaged during thyroid surgery, leading to an inability to create high-pitched sounds (EEK!).

177. Extrinsic muscles of the larynx are those that support its position in the trachea, as opposed to intrinsic muscles, whose function is related to the vocal cords. The infrahyoid muscles, inferior constrictors of the pharynx, suprahyoid muscles, genioglossus, and hyoglossus are considered extrinsic laryngeal muscles.1.

178. The flower basket of Bochdalek is part of the choroid plexus of the 4th ventricle that protrudes through the foramen of Luschka and rest in on CN IX. It is in the lateral pontine (aka pontocerebellar) cistern.

179. Although CN II, IV, V1, V2, and VI have their dural exit in the cavernous sinus,¬†only CN VI ascends freely in the cavernous sinus. CN VI travels in Dorello’s canal, which is at the petrous ridge of the temporal bone, immediately below the posterior clinoid process.

180.¬†Prussak’s space¬†is a recess in the middle ear between the pars¬†flaccida of the tympanic membrane (“Shrapnell’s membrane”) and the short head of the malleus.

181. The auditory ossicles are covered by the mucous membrane lining the tympanic cavity. Unlike other bones, they lack periosteum.

182. The tegmen tympani part of the temporal bone separates the tympanic cavity from the dura of the middle cranial fossa. It thus forms the roof of the tympanic cavity, along with the epitympanic recess.

183. The superior articular facets of C3 lie at an angle of 142 degrees from each other. C4-C7 have superior articular facets that lie 180 degrees.

184. The cruciform ligament of the atlas consists of: transverse ligament of the atlas, superior band and inferior band.

185. The cruciform ligament and the alar ligaments function to keep the odontoid process in place in the atlantoaxial joint.

186. The nasopharynx lies in the space between the medial pterygoid plates and the anterior arch of the atlas.

187. The superior orbital fissure divides the greater and lesser wing of the sphenoid bone.

188. The lymphatic drainage of the head goes from the various lymph nodes to the deep cervical lymph nodes to the jugular duct and then to the right and left venous angles.

189. The venous angle (also known as Pirogoff’s angle) is the junction of the internal jugular and subclavian veins at both sides of the neck.

190. The thoracic duct (also known as van Hoorne’s canal) is the largest vessel of the lymphatic system. It is about 38-45 cm long and 5 mm in diameter. It originates in the abdomen at L2 and drains into the left venous angle. It traverses the diaphragm at the aortic aperature and ascends the superior and posterior mediastinum between the descending thoracic aorta and the azygos vein.

191. The cisterna chyli is a dilation at the origin of the thoracic duct located on the anterior aspects of the bodies of L1 and L2. It is retroperitoneal and located posterior to the abdominal aorta. It receives lymph from the intestinal trunk and two lumbar lymphatic plexuses. It receives fatty chyle from the intestines and therefore acts as a conduit for lipid products of digestion.

192. The external opening of the auditory tube is bony, and thus always open. The inner opening in the nasopharynx is cartilaginous and membranous, and usually closed.193. CN X can be divided into cranial, cervical, thoracic, and abdominal parts.194. The branches of the cervical part of CN X are

    • meningeal¬†
    • auricular
    • pharyngeal
    • superior cardiac
    • superior laryngeal

195. The recurrent laryngeal nerve is from the thoracic part of CN X. One of its branches is the inferior cardiac n., which exerts parasympathetic influence on the heart.


196. The pharyngeal tonsil and tubal tonsil look very similar under the microscope. However, they can be distinguished because the tubal tonsil has a layer of hyalin chondrocytes. 

197. Salpingopharyngeus makes the posterior wall part of the torus tubarius. It raises the pharynx and larynx, and is innervated by CN X.198. The foramina transversaria transmit the vertebral arteries and veins. C7 does not transmit the artery and is smaller than the others.

199. In the cervical vertebrae, C3-C7, the superior articular facets are generally pointing in the superoposterior direction and the inferior articular facets in the inferoposterior direction.

200. C7 is not bifid like the other cervical vertebrae! It attaches the nuchal ligament.

201. The hyoid bone lies at the level of C3. It is suspended from the styloid process of temporal bones by stylohyoid ligaments and bound to the thyroid cartilage by the thyrohyoid membrane. It provides a moveable base for the tongue and attachment for the middle pharynx.

202. The platysma is almost entirely subcutaneous. It serves to convey tension or stress.

203. The investing layer of the deep cervical fascia is attached superiorly to the: superior nuchal lines of the occipital bone, the mastoid processes of the temporal bone, the zygomatic arches, the inferior border of the mandible, hyoid bone and spinous process of the cervical vertebrae.

204. The stylomandibular ligament is a thickened modification of the investing layer of fascia.

205. Superior to the hyoid, a thickening of the pretracheal fascia forms a pulley or trochlea through which the intermediate tendon of the digastric muscle passes, suspending the hyoid. By wrapping around the lateral border of intermediate tendon of the omohyoid, the pretracheal layer also tethers the two-bellied omohyoid muscle, redirecting its course. 

206.¬†Virchow’s node¬†is the left supraclavicular lymph node in the left supraclavicular fossa. (It is on the¬†left¬†side because that is the side on which the thoracic duct drains lymph.)¬†When Virchow’s Node is enlarged, this is referred to as Troisier’s sign, and often indicates¬†abdominal cancer that has metastasized through the lymph vessels, often asymptomatic until a late stage.

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