Cytology PDF

Dr. Mohamed Hassany Ali PhD in Cell, Histology, and Genetics sinaiuniversity.net 1  Cytology @Sinaiunieg [email protected] www.su.edu.eg Cytology: The cell is the basic structural and functional unit of the living body. The cell...

Dr. Mohamed Hassany Ali PhD in Cell, Histology, and Genetics sinaiuniversity.net 1  Cytology @Sinaiunieg [email protected] www.su.edu.eg Cytology: The cell is the basic structural and functional unit of the living body. The cells vary in size from 4 µm (granular cells of cerebellum) to 150 µm (ovum). The cells vary in shape; rounded, oval, flat, stellate, polygonal, cubical, and columnar. Functions: 1. Absorption. 2. Respiration. 3. Secretion. 4. Excretion. 5. Sensation. 6. Conduction. 7. Movement. 8. Contraction. The cell is formed of two basic component (cytoplasm and nucleus). 3 Cytoplasm: It is formed of : 1. Cytoplasmic matrix (cytosol): Carbohydrates. Minerals. Ions and salts. RNA. Metabolites. O2 and CO2 2. Cytoplasmic organelles. 3. Cytoplasmic inclusions 4  Cytoplasmic organelles: Membranous organelles Non-membranous organelles Covered by membranes Uncovered by membranes Contain enzymes No enzymes Cell membrane. Ribosome. Mitochondria. Proteasome. Endoplasmic reticulum. Cytoskeleton. Golgi apparatus. 1. Microtubule (forming cilia, centriole, Lysosome. and flagella). Peroxisome. 2. Microfilament (forming microvilli). Endosome. Coated secretory vesicle. 5 Cell membrane: The outermost covering of the cell (envelopes all the cell). LM: difficult to be seen due to its thickness (7.5-10 nm). It can be detected using with silver (Ag) stain and PAS stain. EM: Trilaminar membrane ( formed of 3 layers), 2 electron-dense (dark lines) layers, and separated by one electron lucent (light line) layer. 6 Molecular structure of CM: Lipids: 1. Phospholipid: arranged into two layers (Phospholipid bilayer): Head (phospholipid) Tails (fatty acid) Charged Non-charged Polar Non-polar Hydrophilic Hydrophobic Directed towards aqueous solutions. Directed to the center facing each other (away from aqueous solutions) 2. Cholesterol: among the hydrophobic fatty acids (tails), restricting the movement of phospholipids to stabilize the CM. 7 Molecular structure of CM: Proteins: Integral (intrinsic) Peripheral (extrinsic) Embedded in the phospholipid bilayer. Small molecules. Large molecules that extend through the bilayer Outside the phospholipid bilayer. from side to side (transmembrane). Loosely attached to both surfaces of the cell Forming channel proteins for transport of ions and membrane. water. Forming carrier proteins for transport of small polar molecules as glucose and ions like Na, K pump. 8  Molecular structure of CM: Carbohydrates: Forming layer over the cell membrane called cell coat (glycocalyx) formed of glycoproteins (oligosaccharide linked to protein) and glycolipid (oligosaccharide linked to phospholipid). Found on the external surface of cell membrane. It includes receptors for drugs, hormones, bacteria, and viruses. Has a vital role in cell adhesion, protection, recognition, immunity, and receptor functions. 9 Molecular structure of CM: 10  Functions of CM: 1. Passive diffusion: gases, water, and ions. 2. Active transport: large molecules and ions using energy (ATP). 3. Selective transport (permeability): molecules using receptors. 4. Endocytosis: entrance of substances inside the cell Phagocytosis (cell eating): entrance of solid particles. Pinocytosis (cell drinking): entrance of fluids. 5. Exocytosis: expulsion of substances outside the cell. 6. Surface modifications: - Cilia: produce current movement (in trachea). Flagella: for cell membrane (in sperms). Microvilli: increase cell surface (in intestinal epithelium). Desmosomes: for cell adhesion (in epithelial cells). 11 Mitochondria: Membranous cytoplasmic organelles, containing enzymes for aerobic respiration and energy production. Power-house of the cell. Number: increase in active cells (up to 1000 mitochondrion in hepatocyte). LM: when abundant thy cause cytoplasmic acidophilia. Appear as rods, granules, or filaments with dark blue color with Iron Hematoxylin and green with Janus green. 12 Mitochondria: EM: appear as oval, rounded membranous vesicle. Surrounded by two membranes: Outer membrane Inner membrane Smooth Less permeable Permeable to small molecules. Projects to the matrix forming finger- Contains transmembrane proteins like folds called cristae (increase surface area for energy production) The mitochondrial matrix contains: oxidative enzymes of citric acid cycle (Krebs cycle), circular molecule of DNA, mRNA, tRNA, rRNA, ions. 13 Function of mitochondria: 1. Cellular respiration. 2. Obtaining energy from metabolites in the cytoplasm by Kreb’scycle. 3. Most of energy stored as ATP molecules and liberated as heat to maintain body temperature. 14 THANK YOU For any questions feel free to contact me by mail [email protected] Dr. Mohamed Hassany Ali PhD in Cell, Histology, and Genetics 15