Model of answer. 1) Give short notes about the following: (6 marks; 2 for each)

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1 Histology and Cell Biology Department, course code: MED 0702 First year Final Exam. (2 nd term) Date: 21/ 6 /2012 Allocated time: 1 1 / 2 hour Total allocated marks: 37.5 Number of papers: 3 papers Number of questions: 7 Model of answer 1) Give short notes about the following: (6 marks; 2 for each) a- Cartilage histogenesis. - Aggregation of mesenchymal cells, which withdraw their processes and transformed to chondroblast. - Chondroblast synthesize and deposits intercellular matrix in the form of thin plates and of collagen fibers. - The differentiation of cartilage take place from the center outward; therefore, the more central cells have the characteristics of chondrocytes, where the peripheral cells are typical chondroblast. - The superficial mesenchyme develops into chondroblasts and fibroblasts of perichondrium. b- Contraction of smooth muscle. - The contractile force is generated by a sliding filament mechanism between actin and myosin and transmitted by the dense bodies and cytoskeleton of intermediate filaments to decrease cell length. - This actin-myosin interaction requires calcium ions for activation, the reservoir for calcium is the subsarcolemmal caveolae. - The contractile unit is the cell, not the sarcomere c- Ultrastructure of blood platelets. The cell membrane is irregular and is covered with a cell coat formed of glycoprotein. 1-The Hyalomere or the peripheral area: contains bundles of microtubules and microfilaments. They have a contractile function so can change the shape of platelets during retraction of blood clot. Types of microtubules: - Surface connecting canalicular system: the microtubules are 1

2 invagination from the cell membrane. - Dense tubular system: the tubules are remnants of the Golgi apparatus of the mother cell. 2-The Granulomere or the central area: contains - Alpha granules: are numerous and are lysosomes. - Mitochondria or Beta granules are few and small in size. - Delta granules are rounded vesicles with clear contents. - Very Dense Granules are rich in serotonin substances, ATP, ADP and Ca. - Glycogen granules present in small or large groups. - A system of tubules and vesicles. 2) Enumerate: (6 marks; 2 for each) a- Types of synapses. a- According to the site of termination of the axon: 1-Axo-somatic synapse 2-Axo-dendritic synapse 3-Axo-axonic synapse b- According to the presence of electron-dense granules: 1-Assymmetrical synapse 2-Symmetrical synapse c- According to the presence or absence of chemical transmitter: 1- Chemical synapse 2- Electrical synapse 3-Mixed synapse b- Stages of erythropoiesis. 1. Undifferentiated Mesenchymal Cell (UMC): 2. Colony-Forming Unit (CFU) Cell: 3. Erythrocyte Colony-Forming Unit (CFU-E) Cell: 4. Proerythroblast: 5. Basophil Erythroblast (Early Normoblast): 6. Polychromatophil Erythroblast : 7. Normoblast (Late Normoblast): 8. Reticulocyte (Immature RBC): 9. Mature Erythrocyte: c- Types of capillaries. 1- Continuous or somatic capillary 2

3 2- Fenestrated or visceral capillary 3- Fenestrated without diaphragms 4- Sinusoidal capillary 3) Define: (3 marks; 1 for each) a- Antigen presenting cells (APCs). APCs are the cells that have the capacity to partially digest proteins, reducing them into small particles which is a necessary preliminary step for activation of T-cells. b- Receptors. They are the terminal ends of sensory nerve fibers. c- Vascular portal system. It is a vascular network of capillaries or sinusoids interposed in the course of an artery or vein 4) Compare between: (6 marks; 3 for each) a- Skeletal and cardiac muscles. 3

4 b- Spinal and autonomic ganglia. 5) Draw a labeled diagram for a section in: (7.5 marks) a- Spleen. (3.5 marks) 4

5 b- Decalcified compact bone. (3 marks) 6) Choose the correct answer: (5 marks; 0.5 for each) 1- )B) 2- )C) 3- )D) 4- )D) 5- )B) 6- )B) 7- )D) 8- )C) 9- )C) 10- )B) 7) Complete: (5 marks; 1 for each) 1- macrocytic 2- sarcolemma 3- ganglion 4-germinal center 5- tight junction 5