Histology NBME Review and Answers

HistoShelfo Wednesday, September 21, 2005 5:56 PM

1. A drawing is shown for you to identify the process of adding to the plasma membrane, similar to exocytosis, but does not have granules. 2.In which part or structure does the process of protein translocation to a membrane occur most frequently. ANS: rER 3. Drawing of connective tissue with different cells. Identify the plasma cell that makes the antigen binding protein.

This is a plasma cell with prominent cytoplasmic rough endoplasmic reticulum. The nucleus has radially arranged clumps of chromatin. The perinuclear Golgi apparatus does not appear in this plane of sectioning. 4.Identify the myelinated axon.

5. Identify where the ATP synthase is. ANS: inner membrane of the mitochondria

The mitochondrion consists of four major sections – the outer membrane, the intermembrane space, the inner membrane, and the matrix.

ATP synthase -- "peppers" the inner mito membrane

6. Identify where the proton pumps are. a.

Inner membrane space

A proton pump is an integral membrane protein that is capable of moving protons across the membrane of a cell, mitochondrion, or other subcellular compartment, thereby creating a difference or gradient in both pH and electrical charge (ignoring differences in buffer capacity) and tending to establish an electrochemical potential. Pasted from

7. Identify where the paneth cells are (small intestine)

Paneth cell

8. Identify enteroendocrine cells. (somatostatin, serotonin)

The enteroendocrine cells of the PC = paneth cells

Enteroendocrine cells Scattered endocrine cells of the gut. Similar cells may occur in the respiratory and reproductive systems. Produce hormones such as somatostatin and serotonin. Taken together these cells constitute a very large endocrine gland.

The image at left shows the nature of the endocrine cells (EC) even more clearly. The secretions are seen here as eosinophilic granules (SG). They will eventually be released from the cell by the process of exocytosis, and diffuse across the basement membrane into the intercellular space close by the nearest capillary. Then they'll diffuse into the capillary and be carried away to their target cells. Also shown in this image are two Paneth cells, an entirely different type of secretory resident cell of the intestine; and one that's not any sort of endocrine cell at all, despite some similarities of appearance. Paneth cells secrete their product into the lumen; and their granules (PCG) are much larger and coarser than those of the true endocrine cells. Hormones and edocrine cells: Hypothalamus: GnRH - TRH - CRH - GHRH - somatostatin Posterior pituitary: ADH - oxytocin Anterior pituitary: GH - ACTH - TSH - LH - FSH - prolactin - MSH Thyroid: thyroid hormone - calcitonin Parathyroid: parathyroid hormone Adrenal medulla: epinephrine - norepinephrine Adrenal cortex: aldosterone - cortisol Pancreas: insulin - glucagon Ovary: estradiol - progesterone - inhibin - activin Testis: testosterone - AMH Pineal gland: melatonin Stomach: gastrin Duodenum: CCK - GIP - secretin - motilin - VIP Ileum: enteroglucagon

9. A drawing with arrows pointing to cells asks you to indicate which cell produces hormones which affect this structure?

10. Identify in the seminiferous tubule the cells that came out from the cells which migrated from the yolk sac.(primordial germ cells, spermatogonia)

11. Identifiy late spermatids.

12. What cells make up the blood/testis barrier? ANS: Sertoli Cells 13. What can happen if you block the production of LH in a man? ANS: Testicles atrophy 14. If you inject choline it will rapidly be visible in type 2 pneumocytes, Why? Answer: Surfactant produced lowering surface tension allowing gas exchange. Experiment: Intratracheal injection of 3-day-old rabbits with radioactively labeled palmitic acid and choline results in an 8-10-fold increase in the efficiency of their incorporation into surfactant phosphatidylcholine when compared to the intravenous injection of these precursors.

15. If you inject something into the veins in which capillary bed will it end up in? ANS: Lungs 16. What does not cross the blood brain barrier? ANS: Albumin  Possibly due to size of pore in the bbb -- does not allow Albumin through b/c large protein 17. Identify in a drawing which is the structure or protein that "gets fucked up" in red blood cells and causes spherocytes to appear? The protein is spectrin, but the answer is being able to identify it.

18. Which cell has the nucleus very compacted because it has more histones? ANS? I'm not sure but I answered spermatids. Spermatids have lots of histones that convert to protamines in the final stages of spermatogenesis. Oocytes keep their histones. If the question has oocytes, go with that, but otherwise, the correct answer is spermatids. 19. You give someone something 3H hydrocortisone and 40% will go to the nucleolus, what is it? ANS: rRNA (found in chromatin of the nucleolus which makes this rRNA) Hydrocortisone is a glucocorticoid produced in the zona fasciculata of the adrenal cortex. It depresses the immune and inflammatory response by suppressing interleukin-1 and IL2 production by lymphocytes and macrophages. Glucocorticoids also stimulate the destruction of lymphocytes in lymph nodes and inhibit mitosis by transformed lymphoblasts. Hydrotcortisone A steroid hormone, produced by the adrenal cortex, that regulates carbohydrate metabolism and maintains blood pressure. Also called cortisol. A preparation of this hormone obtained from natural sources or produced synthetically and used to treat inflammatory conditions and adrenal failure. No free [3H]hydrocortisone was found in nuclei, in isolated nuclei it is found in the fraction of nuclear membranes, nucleoplasm, nucleolus and chromatin

20. Identify the quantity of DNA in a cell undergoing metaphase II of meiosis in a table with the following values which define the content of DNA in the cells during spermatogenesis. ANS: N

21. Basophillic staining erythroblast has lots of? Identify it on a graph! ANS: RNA Basophilic structures are stained by basic dyes: Basic dyes are positive Basophilic structures are negative (ex. DNA, RNA, ribosomes, RER) Mnemonic: Basophilic = Blue

DNA and RNA are basophillic due to the presence of phosphate group 22. Stroma cells of the cortex of the thymus which help with T lymphocyte maturation are derived from? Possible ANS? Mesenchymal mesoderm, endoderm, or neural crest cells The stroma within the cortex is a network of epithelial cells derived from embryonic ectoderm (third branchial cleft) and endoderm (third pharyngeal pouch).

23. What phase comes after DNA replication? ANS: G2 and M phase a. i.

Cell cycle - all cell growth - check points - p53 (etc.)

24. What is the amount of DNA in a cell which was produced by mitosis and of a cell that was 2n? Ans. 1N 25. Emphysema is caused by the loss of alveolar ducts. I. A. Alveolar ducts a. Cubiodal cells with and without cilia b. No goblets

26. Trisomy is due to non disjunction : Non-disjunction can occur during meiosis I or meiosis II 27. Where are glycoprotein secretory vesicles just before exocytosis. The plasma membrane and cytoplasm were not an option. ANS: trans golgi These and many other cells simultaneously utilize two different classes of vesicles to move proteins from the trans-Golgi to the cell surface: secretory vesicles for regulated secretion and transport vesicles for constitutive (continuous) secretion.

29. Identify the organelle where glycosylation begins rER N-linked glycosylation begins in the lumen of the rough ER. O-glycosylation occurs in the Golgi. 30. Identify organelle that contains circular DNA.(mitochondria) 31. Identify the mitochondria of skeletal muscle with sarcoplasmic reticulum. ANS: sER Cardiac muscle has a much richer supply of mitochondria than skeletal muscle. This reflects its greater dependence on cellular respiration for ATP

32. Leydig cells, testosterone, have many SER 33. Cross sectional skeletal muscle proportional to contracting force in the same skeletal muscle. 34. Melanosomes are given to the cells of the epidermis . ANS: Keratinocytes After being produced in the melanocytes, packets of melanin called melanosomes transfer to the keratinocytes. There they are arranged to protect the deoxyribonucleic acid (DNA), or genetic material, of the keratinocytes.

35. Meissner corpuscle-light touch. ANS: Dermal papilla 

the dermal papillae for oval-shaped, lightly staining groups of cells

36. Pacinian corpuscle – The vibrations of a tuning fork

A vibrating tuning fork activates pacinian corpuscles very rapidly and widely across the periosteum of the skull or the sternum.  PACINIAN CORPUSCLES: They mediate the sensation of vibration. o Rapidly-Adapting, Phasic response: The receptor stops firing after the stimulus has been present for a while. o STRUCTURE: It is like an onion.  If you remove the layers of the onion, then the receptor becomes slowly-adapting. The onion-layers thus serve the purpose of adaptation -- they make it so the underlying nerve fiber is only discharged temporarily.  The onion layers also filter out the low-frequency stimuli, such that Pacinian Corpuscle has frequency specificity for high frequency vibrations

37. Where would you expect to see the primary squamous cancer? ANS: Anus Neck cancer is associated with squamous cell cancer, no anus found.

38. Who produces chylomicrons?White adipose tissue (stores), are produced by enterocytes Enterocytes assemble chylomicrons from absorbed lipids and transfer them to lymphatic capillaries (lacteals) in the lamina propria. 39. By what mechanism is protein returned to the Rough Endoplasmic Reticulum? COP I coated vesicles 40. Dyenin arms involved in transportation of vesicles down the axon. ANS: Retrograde Transport The motors for retrograde transport are dyneins, similar to the motors of flagella.  41. What organelle does not have the axon? Golgi was not an option, I answered RER 42. Microvilli are made of? ANS: actin microvilli:

-core made of actin filaments with fimbrin and villin crosslinking the filaments, myosin I attaches filaments to the membrane, actin filaments of the microvilli are linked into the actin filaments of the terminal web, the terminal web is made of other actin filaments associated with tropomyosin, spectrin and myosin II

43. What protein is involved in anchoring the endothelial cell of the basement membrane? Laminin 44. GFAP (Glial fibulary acidic protein ) are of the astrocyte GFAP is the marker used to identify astrocytes. 45. Description of what part of the cell does not permit movement of material in intercellular space and connective tissue? ANS? I answered tight jxns 46. Know all the types of capilaries and where they are found

  

continuous, : muscle, lung, central nervous system fenestrated, : endocrine glands, sites of fluid absorption (gallbladder and intestinal tract) sinusoidal : liver, spleen, bone marrow

47. Collagen type II is hyaline cartilage and it's found in the nose. a. SEE Shelf question 2 above (cocaine…) 48. In organ rejection which is the cell of the epidermis which migrates to start this process? ANS: Langerhans One major mechanism in the inititiation of allogeneic organ rejection is mediated by specialized antigen-presenting cells within the gut associated lymphatic tissues (GALT). Besides the commonly described professional antigen presenting cells (APCs) like Langerhans cells...

49. How can you distinguish a neutrophillic myelocyte from the non differentiated myelocytes? ANS: Azurophillic granules.

Neutrophilic myelocyte

50. What part is responsible for the growth of longitudinal of the bone? ANS: Epiphyseal plate (secondary ossification center) Longitudinal bone growth (measured with weekly radiographs) occurred at the epiphyseal, not at the metaphyseal, surface of the growth plate

Secondary ossification centre is established

51. Where is the secondary ossification center? ANS: Epiphysis 52. What type of cartilage does not receive nutrients from synovial fluid. ANS? medial meniscus was one of many options. 53. Red skeletal muscle has HIGH levels of succinate dehydrogenase which is low in white muscle cells. 54. When a muscle gets fucked up what is responsible for it's regeneration? ANS: satellite cells, which were among the options. The answer is satellite cells

55. When the skin closes in a few days it is because of? ANS: Keratinocytes 56. There are low calcium serum levels, and the muscle continues contracting as a result of ? ANS: Tetany The process of contracting takes some 50 msec; relaxation of the fiber takes another 50–100 msec. Because the refractory period is so much shorter than the time needed for contraction and relaxation, the fiber can be maintained in the contracted state so long as it is stimulated frequently enough (e.g., 50 stimuli per second). Such sustained contraction is called tetanus.

In the figure,

 

When shocks are given at 1/sec, the muscle responds with a single twitch.

At 5/sec and 10/sec, the individual twitches begin to fuse together, a phenomenon called clonus.  At 50 shocks per second, the muscle goes into the smooth, sustained contraction of tetanus. Clonus and tetanus are possible because the refractory period is much briefer than the time needed to complete a cycle of contraction and relaxation. Note that the amount of contraction is greater in clonus and tetanus than in a single twitch. As we normally use our muscles, the individual fibers go into tetanus for brief periods rather than simply undergoing single twitches.

57. Dense body of the smooth muscle is like the Z band. o

o

o

o

In each sarcomere, the broad band which appears dark in standard histological procedures is called the A-band. This band indicates the location of thick filaments (myosin); it is darkest where thick and thin filaments overlap. The broad light band between the dark bands is the I-band. The Iband indicates the location where thin filaments (actin) extend beyond the thick filaments. A distinct dark line running down the middle of the I-band is the Zline, where thin filaments are attached end to end. Where thick filaments are attached end-to-end in the center of the A-band is the M-line. When muscle is stretched, an H-band appears along the middle of the A-band, between the free ends of the thin filaments.

58. Rigor mortis: ATP is needed for muscle relaxation. 59. They show you different experiments to choose which show that muscles generate a substance that acts on the axons and influences ---- which muscles innervate best. The terminals of motor axons contain thousands of vesicles filled with acetylcholine (ACh).

When an action potential reaches the axon terminal, hundreds of these vesicles discharge their ACh onto a specialized area of postsynaptic membrane on the fiber. This area contains a cluster of transmembrane channels that are opened by ACh and let sodium ions (Na+) diffuse in.

a. Skeletal b. Smooth c. Cardiac 60. Intrafusal fibers have sensory stretch receptors. 61. Heart has an atrial natrieuretic peptide. Myocardial endocrine cells are secreted in response to high blood volume or venous pressure. ANF is released by walls of the cardiac atrium in response to high sodium concentration, high extracellular fluid volume, or high blood volume. It then acts via various mechanisms to excrete Na, and to cause

vasodilation in the circulatory system. Notably, it is secreted in response to immersion of the body in water, which causes an atrial stretch due to altered distribution of intravascular fluid. It has been shown that in horses, it is also released in response to exercise. Physiological Effects Renal  Dilates the afferent glomerular arteriole, constricts the efferent glomerular arteriole, and relaxes the mesangial cells. This increases the glomerular filtration rate, resulting in greater excretion of Na+ and water.  Decreases Na resorption in the renal distal convoluted tubule and cortical collecting duct.  Inhibits renin secretion. Vascular  Relaxes vascular smooth muscle in arterioles and venules and opposes the pressor effects of catecholamines and Angiotensin-II

62. What is the type of epithilium of the apocrine sweat gland? ANS: Simple cuboidal 63. Identify myelinated axons. -- see questions 4 above 64. Schwann cells are in charge of?

Any of the cells that cover the nerve fibers in the peripheral nervous system and form the myelin sheath.

65. Purkunje cells are the only output of the cerebellum

The Purkinje cell (left) compares and processes the varying inputs it gets, and finally sends its own axons out through the white matter and down to the deep nuclei. Although the inhibitory Purkinje cells are the main output of the cerebellar cortex, the output from the cerebellum as a whole comes from the deep nuclei. The three deep nuclei are responsible for sending excitatory output back to the thalamus, as well as to postural and vestibular centers. There are a few other cell types in cerebellar cortex, which can all be lumped into the category of inhibitory interneuron. The Golgi cell is found among the granule cells. The stellate and basket cells live in the molecular layer. The basket cell (right) drops axon branches down into the Purkinje cell layer where the branches wrap around the cell bodies like baskets.

66. What causes the blood to stop going to the capillaries of a pregnant woman? ANS: Metarterioles with their precapillary sphincters. 67. Identify one of the cells of the intra alveolar septum, the ones that produce surfactant. ANS: pneumocyte type II. 68. A pain in the following tissue makes you feel referred pain. ANS? I answered the belly button because it reminded me of the appendix.

Pain that is felt in a part of the body at a distance from the area of pathology, as pain in the right shoulder derived from the presence of a gallstone in the bladder. Myocardial ischemia is the heart tissue that is the best know cause of referred pain.

69. Identify in a picture with all the tubules of the kidney, Which is the part of the tube on which ADH has it's action/effect. Ans. Collecting duct

Antidiuretic hormone binds to receptors in the distal or collecting tubules of the kidney and promotes reabsorption of water back into the circulation.

70. Primary convoluted tubule – reabsorption of proteins via microvilli 71. Capillaries that surround the tubules of the kidneys came from where? Efferent arteriole Outflow from the glomeruli is via the efferent arterioles, which are somewhat smaller than the afferent ones. These almost immediately break up into the fine capillary networks which surround the loops of the nephrons. The capillaries are vital to maintaining the gradient of sodium concentration in the kidney's interstitial spaces; the concentration is highest in the deep medulla and lowest in the cortex. You'll see some places where the capillaries are arranged in a net-like configuration, close to the glomeruli from which they arise; and others where capillary beds are arranged as long straight segments. Within these straight regions are recurrent loops. By appropriate opening and closure of venous shunts the kidney can regulate sodium concentrations by regulating the flow of blood in the capillaries that surround the nephrons proper (the rete mirabile) or their extension, the straight and recurrent vessels of the vasa recta.

72. If the hypothalamus is destroyed what cells of the hypophysis are going to increase their secretions? Choices acidofiles, basofiles, chromophobes, follicle stillate cells. 73. Know suprarenal gland parts and their secretions(fasc- glucocorticoides) 74. What happened to a woman which has thicker hair? (maybe androgens ZRet) 75. Pineal gland synthesizes serotonin during the day and melatonin at night. 76. Person loses something in the phalanges (maybe merckel cells) (See question 2 from Shelf Site) 77. Identify respiratory passageways.

78. Identify where respiration occurs for the first time (resp epth), DON’T CONFUSE WITH ALVEOLAR DUCT. If the question asks about where gas exchange occurs, it is after the terminal bronchiole, beginning with the respiratory bronchiole. 79. Somatostatin inhibits secretion of? ANS: somatotropin (growth hormone) Growth hormone, also known as somatotropin, is a protein hormone of about 190 amino acids that is synthesized and secreted by cells called somatotrophs in the anterior pituitary. It is a major participant in control of several complex physiologic processes, including growth and metabolism. Growth hormone is also of considerable interest as a drug used in both humans and animals. o o o

Growth hormone-releasing hormone (GHRH) is a hypothalamic peptide that stimulates both the synthesis and secretion of growth hormone. Somatostatin (SS) is a peptide produced by several tissues in the body, including the hypothalamus. Somatostatin inhibits growth hormone release in response to GHRH and to other stimulatory factors such as low blood glucose concentration. Ghrelin is a peptide hormone secreted from the stomach. Ghrelin binds to receptors on somatotrophs and potently stimulates secretion of growth hormone.

EXTRA: Somatostatin appears to act primarily in a paracrine manner to inhibit the secretion of both insulin and glucagon. It also inhibits Ca

80. CCK stimulate pan dig enz secretion 81. Lactose digests milk - beta galactolidase activity at the cell surface of enterocytes (see question 1 from shelf site) 82. Identify bile cannaliculi in a longitudinal manner . 83. Identify the layer which is continuous with the proximal convoluted tubule in an EM of a renal corpuscle. Loop of Henle

84. Know the epithelium of the renal tubules, I think the key was that one of them did not have microvilli or did not interact with something of "absorcon". The ones that have the brush border are the proximal convoluted tubules and the descending loop of henle 85. Where are the JG cells found which secrete renin? ANS: Near the macula densa, (JGA) juxtaglomerular aparatus. 86. Proliferative phase, secretory phase…what hormone controls/regulates? ANS: Proliferative (estrogen/FSH) and secretory (LH and Progesterone) 87. I think they describe the histo of the secretory phase and you have to answer something respect to what is happening in that phase . . . They have spiral arteries. Progesterone starts the secretory phase. 88. The Cones are those of the fovea centralis 89. Identify basilar membrane. YOU SEE A DRAWING OF THE EAR.

90. Identify a cell of the organ of corti which has something that's related to axons. ANS. Hair cells

myelocyte