Cytology Part 1 Lecture Notes PDF

‫كلية الطب البيطري‬ ‫جامعة الزقازيق‬ Dr. Dina Mohammad Al-sadek professor of Histology and Cytology  Cytology Cytology : is the science that studies all aspects of the cell (structure, function, division, etc….. Histology : is the science that s...

‫كلية الطب البيطري‬ ‫جامعة الزقازيق‬ Dr. Dina Mohammad Al-sadek professor of Histology and Cytology  Cytology Cytology : is the science that studies all aspects of the cell (structure, function, division, etc….. Histology : is the science that study structure and function of the tissues and organs. Groups of cells form a tissues. Groups of tissues form an organs. Organs form a system. Groups of system form the body as: digestive, urinary system, etc. tools of studying histology The cell is the smallest structural and functional units of living material of multicellular organism. Cell is composed of mass of protoplasm divided into: 1 – Cytoplasm. 2- Nucleus. A-The cytoplasm consists of: a- cytoplasmic organelles b- cytoplasmic inclusions c- Cytoplasmic matrix I – Cytoplasmic organelles They are living and permanent inside cytoplasm. They are metabolically active structures. They perform specific functions. They are essentials for life of the cells. They are classified according to presence of membranes into: - (A) Membranous organelles (B) Non- membranous organelles  (A) -Membranous organelles 1- The cell membrane"plasma membrane" "plasmalemma": Def.: is the outer membrane of the cell that acts as a barrier between its internal and external environment. At light microscope level (LM): -It is invisible because the cell membrane measures (8-10 nm) in thickness. -It can be stained with silver impregnation appear as dark brown line or Periodic acid Schiff (PAS) appear as pink line.  At electron microscope level (EM): it appears as a trilaminar structure (3 lamina) consisting of 1-Outer electron-dense lamina (2.5 nm). 2- Intermediate electron-lucent lamina (3 nm). 3- Inner electron-dense lamina (2.5 nm).  The molecular structure of the cell membrane Arranged in amanner called Fluid mosaic model According to this model, the cell membrane is made up of three major components 1-phospholipids, 2-proteins and 3-carbohydrates. because integral membrane proteins have the ability to float like icebergs in the sea of phospholipids 1- Lipid (30%) A- Phospholipid molecule "lipid bilayer" :Each molecule is formed of two ends 1-one polar heads (hydrophilic) (has affinity with water) 2- tow long non polar tails (hydrophobic) has no affinity with water The phospholipids molecules are arranged with their hydrophilic ends are directed outward, while hydrophobic tails are directed inward toward the center of the membrane. B- Glycolipid C- Cholesterol  2- Proteins (60%) - They are a major molecular constituent of membranes. - They are embedded into the phospholipids layer either A- Partially (peripheral or extrinsic protein): only partially embedded to either aspects of the membrane. B-Completely (integral or intrinsic protein): are firmly attached to the lipid bilayer. two types: 1- Transmembrane protein (participate in cell receptors) 2- Incomplete pass proteins  3- Carbohydrates (10%) (Glycocalyx =cell coat) - Carbohydrates Attachment site: to external surface of the cell. - Carbohydrates Attachment types: - 1- glycoprotein: carbohydrates attached to transmembrane protein. 2- glycolipid: carbohydrates attached to lipid polar heads. N.B: (glycolipid+ glycoprotein =cell receptors = Glycocalyx) Functions of the cell coat (Glycocalyx) 1-Mechanical and chemical protection the cell membrane. 2- Aids in the induction of immunological (antigen-antibody) response. 3- Site for binding of hormones. 4- Shares in the formation of intercellular adhesions. 5- Contributes to the formation of the basement membrane. 6- Cell recognition. Diagram for molecular structure of cell membrane Functions of cell membrane: 1-Protection: Protect the cell from dangers. 2-Regulation: Regulate the entry and exit of substances into the cell. 3-Recognition: It allows the different cells to recognize each Other and adhere to each other. 4-Modified to: special structure that play important roles : Cell membrane modifications are: A-Cell junctions: keeping cell-cell attachment. B-Microvilli and cilia: for motility or increasing the cell surface area. 5- Transportation: cell membrane transmits substances by different ways: a- Endocytosis Endocytosis involves either the a- engulfment of solid particles (phagocytosis) or b- minute droplet of fluid (pinocytosis). The engulfed material is surrounded first by cytoplasmic extensions called pseudopodia. When the particles become completely surrounded, the plasma membrane fuses and the membrane surrounding the engulfed particles forms a vesicle, known as a phagosome or endocytotic vesicle, which detaches from the cell membrane to float freely within the cytoplasm. Once the phagosome enters the cytoplasm it fuses with the lysosomes and their contents are subjected to enzymatic digestion. b- Exocytosis Exocytosis (Exo = out) is the process by which some membranous vesicles located within the cytoplasm fuse with the plasma membrane and release their contents outside the cell. It occurs in many secretory processes.  2-Mitochondria: Definition: Mitochondria are membranous organelles involved primarily in cell respiration and energy production. Structure: 1- Outer mitochondrial membrane. 2-Inner mitochondrial membrane. (Contains ATP synthase &infolding into cristae) 3-intermembrane space. 4-mitochondrial matrix (has: enzymes, ribosomes, DNA &RNA) N.B: Number of mitochondria differs according to the cell type in which: 1- They Absent in RBCs. 2-hundreds in muscles &liver. Diagram of mitochondrial structure EM structure of mitochondria Functions: 1- Mitochondria are a powerhouse of the cell and site for ATPs production. (ATPs are the form of stored energy) 2- Cellular respiration (metabolize nutrient into ATPs) 3- It absorbs and stores calcium ions. 4- Mitochondria play key roles in activating apoptosis in mammalian cells.  3-Endoplasmic Reticulum (ER): The Endoplasmic reticulum (Endo=inside; plasm=cytoplasm; reticulum = network) is an irregular network of branching and anastomosing tubules, cisternae and vesicles. Two types of ER are recognized, rough and smooth. A-Rough Endoplasmic Reticulum (RER) Definition: one of the membranous cell organelles It is called rough due to the presence of large number of ribosomes attached to its limiting membrane. With LM, it appears as basophilic cytoplasmic areas With EM, it consists of an anastomosing network of tubules, vesicles and flattened cisternae  EM micrograph of RER Functions: 1- Synthesis of proteins for extracellular use (secretory proteins, lysosomal proteins and membrane proteins). 2- Glycosylation of proteins to form glycoproteins.  B- Smooth Endoplasmic Reticulum (SER) Definition: membranous cell organelle that formed from smooth surfaced anastomosing tubules. With LM, it does not appear. The cytoplasm of the cells contained abundant sER usually appears acidophilic. With EM, it appears as irregular network of membranous tubules and vesicles devoid of ribosomes, The sER tubules may be continuous with those of rER and Golgi apparatus Functions 1- Steroid hormone synthesis 2- Drug detoxification in liver cells. 3- Lipid synthesis in the intestinal absorptive cells. 4- Release and storage of Ca ++ ions in striated muscle cells. 5- Production of HCL in gastric parietal cells. EM picture of SER  4-Golgi Apparatus: (Golgi complex) Definition: a membranous organelle concerned principally with synthesis, concentration, packaging and release of the secretory products. With LM, it can be stain with silver salts or osmium where it appears as a black network located near the nucleus. In H&E sections, it may be visible as a lighter- stained region called negative Golgi image With EM, composed of 3 distinct smooth membrane- limited comartement 1- slightly curved stacks of 3-10 flattened cisternae , each stack has A- immature convex face (cis face) B- mature concave face (trans face) 2- numerous small vesicles around periphery of the stack. 3- few large vacuoles at one pole of the Golgi complex. Functions 1- Packaging and concentration of secretions. 2- Modification of the secretory products 3- Production of primary lysosomes.  EM picture of Golgi apparatus Diagram for Golgi apparatus structure  5-Lysosomes: Definition: They are membrane-bounded vesicles containing a number of hydrolytic enzymes that are active at acid pH (acid hydrolases). This group of enzymes is capable of destroying all the major macromolecules (e.g., proteins and lipids) of the cells. N.B: The lysosomes increased in number in phagocytic cells. With LM, Can be seen in cell using specific histochemical reaction called acid phosphatse as small dark granules. N.B: if we found amount of acid phosphatase is high in the cell, this mean that cell go to degeneration.. With EM, The lysosomes appear as spherical membrane-bounded vacuoles with their contents showing varying degree of electron density. Types of lysosomes 1- Primary lysosomes :are lysosomes freshly formed from the Golgi or sER. They contain nothing but hydrolytic enzymes. 2- Secondary lysosomes: formed as the result of fusion of primary lysosomes with phagosomes. A phagosome is a membrane-bounded vesicle containing either exogenous material (e.g., bacteria) and it is called heterophagosome or endogenous material (e.g., damaged organelle) and it is called autophagosome. 3-Multivesicular bodies : are spherical forms of heterophagosomes. They are membrane-bounded vesicles containing a number of smaller vesicles. 4-Residual bodies: are debris containing vacuoles representing the terminal stage of lysosomal activities. Their contents may either be extruded from the cell by exocytosis or accumulate in the cytoplasm as lipofuscin pigments. Functions 1- Degradation of any exogenous macromolecules (phagocytosis and pinocytosis). 2- Disposition of any organelles or cell constituents that are no longer useful to the cell (autophagy). Diagram showing types of lysosomes