Medical Histology: Key Concepts and Review Questions

Revision By Dr. Shaimaa Zaher Lecturer of Histology

Which of the following features best describes osteoblasts? A.They are called bone resorbing cells. B.They have deep basophilic cytoplasm. C.They are found inside lacunae. D.Their cytoplasm is rich in carbonic anhydrase enzyme. Answer: B

• Lysis of the inorganic part of bone matrix depends on the activity of which of the following enzymes? A. Lysosomal enzymes B. Oxidizing enzymes C. Carbonic anhydrase enzyme D. Alkaline phosphatase enzyme Answer: C

• The 2 nd zone of the epiphyseal growth plate starting from the epiphysis is: A. Zone of ossification B. Zone of hypertrophy C. Zone of proliferation D. Zone of calcification Answer: C

• Which of the following statements is correct about erythrocytes? A. They are the least abundant formed blood element. B. They have acidophilic cytoplasm due to multiple mitochondria. C. Old RBCs are phagocytosed by macrophage in the liver. D. In rapid blood stream they adhere with a rouleaux appearance. Answer: C

Which of the following proteins associated with the erythrocyte plasma membrane is responsible for maintaining the cell's biconcave disk shape? (A) Troponin (B) Hemoglobin (C) Spectrin (D) α- Actinin Answer: C

Which of the following possesses specific and azurophilic granules? (A) Red blood cell (B) Lymphocyte (C) Platelet (D) Neutrophil Answer: D

What is the statement that best describes the nuclei of the following leukocytes? A. Polymorphs have multiple nuclei B. Monocytes have multilobulated nuclei C. Lymphocytes have spherical nuclei D. Basophils have horseshoe-shaped nuclei Answer: C

• Which of the following statements about granules of leukocytes is correct? A. Azurophilic granules of basophils contain antibacterial proteins. B. Specific granules of eosinophils contain major basic protein. C. Specific granules of basophils contain histaminase enzyme. D. Specific granules of neutrophil contain myeloperoxidase enzyme. Answer: B

Basophilia occurs in which of the following cases? A. Allergic conditions B. Lung diseases C. Acute Bacterial infections D. Tuberculosis Answer: A

Which of the following histological methods can differentiate between types of lymphocytes? A. Hematoxylin and eosin staining B. Leishman staining of blood films C. Immunohistochemical staining for surface receptors D. Electron microscopic detection of azurophilic granules Answer: C

Which of the following best describes T lymphocyte? A.They represent 60 to 80 % of circulating lymphocytes. B.They acquire surface markers in the bone marrow. C.They are responsible for humoral immunity. D.They can differentiate into plasma cells. Answer: A

• Blood platelets are characterized by which of the following features? A. Their glycocalyx determine blood groups B. Marginal bundle is located centrally C. Glycogen granules accumulate around the nucleus D. Alpha granules contain coagulation factors Answer: D

• What is the name connective tissue that surround each skeletal muscle fiber? A. Perimysium B. Endomysium C. Epimysium D. Epineurium Answer: B

What is the type of connective tissue of the epimysium? A. Loose connective tissue B. Reticular connective tissue C. Dense irregular connective tissue D. Specialized type formed of joined fibroblasts Answer: C

The sarcomere lies between which of the following paired structures in myofibrils? A. Adjacent A bands B. Adjacent I bands C. Adjacent M lines D. Adjacent Z lines Answer: D

• Which of the following portions of the sarcomere contains both thick and thin filaments? (A) A band (B) H zone (C) I band (D) M line Answer: A

• Which of the following is true for skeletal muscle? (A) T tubules are located at the Z line. (B) T tubules are absent. (C) Troponin is absent. (D) It possesses triads. (E) It possesses caveolae Answer: D

• Which of the following is true for cardiac muscle? (A) Sarcoplasm appears basophilic. (B) T tubules have a smaller diameter than those of skeletal muscle. (C) It is formed of multinucleated cells. (D) It possesses diads. Answer: D

• The axon hillock contains (A) rough endoplasmic reticulum. (B) free ribosomes. (C) microtubules. (D) Golgi complex. Answer: C

Which of the following statements is characteristic of the perineurium? (A) It surrounds many bundles of nerve fibers. (B) It surrounds a single nerve fiber. (C) It is formed of reticular connective tissue. (D) Its cells form blood nerve barrier. Answer: D

• Which of the following represents one of central neuroglia? A. Astrocytes B. Schwann cells C. Satellite cells D. Ganglionic cells Answer: A

Which statement best describes microglia? A. It support neurons of PNS B. It is ectodermal in origin C. It lines central canal of spinal cord D. It is a motile phagocytic cell Answer: D

Synaptic vesicles possess which of the following characteristics? (A) Manufacture neurotransmitter (B) Release neurotransmitter via exocytosis (C) Are attached to the postsynaptic membrane (D) Enter the synaptic cleft Answer: B

• Which of the following features characterizes electrical synapse? A. It is the most common type of synapse B. It includes gap junctions of smooth muscles C. Transmission of the impulse is unidirectional D. It requires neurotransmitters for its function Answer: B

Put ( ✓ ) or (  ) 1 The type of junctions found in the lateral portions of intercalated discs are gap junctions. ✓ 2 Multiple osteocytes are found in the same lacuna.  3 The first bone to be produced during fetal development is woven bone ✓ The outer circumferential bone lamellae are parallel to the endosteum.  Spongy bone forms the outer and inner plates of the skull  Endochondral ossification occurs in a model of elastic cartilage  Crescent shaped RBCs are fragile and result in hemolytic anemia ✓

Erythrocytes can exit the capillaries by squeezing between endothelial cells to function in connective tissue  Basophils can divide outside the bone marrow  CD4 T-lymphocyte can recognize antigens on the surface of antigen presenting cells ✓ NK cells kill target cells in a similar way to that of c ytotoxic T lymphocytes ✓ Dense bodies are unique to the cardiac muscle  Neurofilaments can be stained by silver satin ✓ Axons carry nerve impulses toward the perikaryon  Dendrites have constant diameter 

Small diameter axons in PNS are unmyelinated and surrounded by Schwann cells ✓ One Schwann cell can form myelin around multiple internodal segments of the same axon  Neurilemmal sheath is found in nerves of PNS and CNS  The neurons of dorsal root ganglia are multipolar and scattered  The neurons of autonomic ganglia are surrounded by incomplete layer of satellite cells ✓

• The structural unit of compact bone is … osteon (Haversian system) … . • Intramembranous ossification occurs in … flat bones … & … ..clavicle … . • Replacement of immature bone by mature bone depends on … bone remodeling … . • Blood film is stained by … .. Leishman ’ s stain …… to demonstrate its different elements. • An increase in the number of RBCs above the normal range is called ……… Polycythemia or erythrocytosis ………………………… • Skeletal muscles of marathon runners are mainly formed of .. slow oxidative … muscle fibers • Myelin sheath is specially stained by .. osmic acid … .

➢ Mention bone lamellae of the compact bone. ✓ Outer circumferential lamellae ✓ Haversian system (osteons) ✓ Interstitial lamellae ✓ Inner circumferential lamellae ➢ Enumerate types of ossification. ✓ Intramembranous ossification,. ✓ Endochondral (intracartilagenous) ossification

➢ Mention the first three zones of the epiphyseal growth plate starting form the epiphysis. ✓ 1- Zone of reserve cartilage ✓ 2- Zone of proliferation ✓ 3- Zone of hypertrophy ➢ Enumerate types of anemia ✓ Deficiency anemia as: • Iron deficiency anemia • Pernicious anemia (Vitamin B 12 & folic acid deficiency anemia). ✓ Hemorrhagic anemia ✓ Hemolytic anemia ✓ Aplastic anemia

➢ Mention conditions that causes neutrophilia. ✓ Acute bacterial infections as in: ▪ Acute tonsillitis ▪ Acute appendicitis ▪ Abscess formation ➢ Mention conditions that causes monocytosis. ✓ Chronic infections as in tuberculosis ✓ Monocytic Leukemia

• Enumerate types of skeletal muscle fibers. ✓ Red fibers (Slow oxidative muscle fibers) ✓ White fibers (Fast glycolytic fibers) ✓ Intermediate fibers ➢ Mention components and site of each triad of skeletal muscle fibers. ✓ Components: ▪ Transverse tubule (T-tubule) ▪ Two terminal cisternae of sarcoplasmic reticulum ✓ Site: ▪ A-I junction of each sarcomere

➢ Mention types of neurons according to the number of processes. ✓ Pseudounipolar neurons ✓ Bipolar neurons ✓ Multipolar neurons ➢ Mention three sites of bipolar neurons ✓ Retina ✓ Olfactory epithelium ✓ Inner ear

➢ Enumerate types of central neuroglia (in CNS) ✓ Astrocytes ✓ Oligodendrocytes ✓ Microglia ✓ Ependymal cells ➢ Enumerate types peripheral neuroglia (in PNS) ✓ Schwann cells ✓ Satellite cells (of ganglia)

➢ Enumerate the three types of synapses between neurons according to the site of contact of the axon. ✓ Axodendritic ✓ Axosomatic ✓ Axoaxonic ➢ Mention the three major components of the neuromuscular junction. ✓ The presynaptic axon terminal ✓ The postsynaptic cell membrane ✓ The synaptic cleft

Primary (Azurophilic) granules = Lysosomes Secondary (Specific) granules SizeNumber Larger & less numerous than specific granules Smaller & more numerous than 1ry granules. LM Stained purple with azure stain Stained pale pink (salmon pink)(but hardly demonstrated by LM) EM larger and more electron dense small and less electron dense Contents They contain acid hydrolases and antibacterial proteins , including: Myeloperoxidase , Lysozyme and Defensins Contain various enzymes as collagenase , and other antimicrobial peptides (e.g. lactoferrins ) Granules of neutrophils

Granules of eosinophils Primary (Azurophilic) granules = Lysosomes Secondary (Specific) granules LM Stained purple with azure stain Coarse acidophilic shiny red. EM few , roundedelectron dense numerous,elongated or oval with flattened electron dense core (Crystalloid core) surrounded by less electron dense matrix . Contents They contain hydrolytic enzymes as acid hydrolases Contain Major basic protein (MBP)HistaminaseSulfataseEosinophil-Derived Neurotoxin (EDN)

Granules of basophils Primary (Azurophilic) granules = Lysosomes Secondary (Specific) granules LM Stained purple with azure stain basophilic granules that obscure the nucleus metachromatically stained with toluidine blue EM very large, irregularly shaped electron dense Contents They contain hydrolytic enzymes as acid hydrolases Contain heparinhistamineleukotrienes eosinophil chemotactic factor

✓ Glycogen granules. ✓ Alpha granules (the most numerous) contain coagulation factors and growth factors. ✓ Delta granules contain ADP, ATP, and serotonin ✓ Lambda granules are lysosomes containing hydrolytic enzymes Granules of blood platelets (thrombocytes)

Junctions Gap junctions Fascia adherens & Desmosomes Tight junctions Processes of osteocytes Smooth muscle fibers Lateral component of the intercalated disc Transverse component of the intercalated disc Epithelial like fibroblasts of perineurium to form blood nerve barrier Ependymal cells to form blood CSF barrier