Histology Revision 2024 PDF

Medicine and Surgery Program Fall 2023-2024 NORMAL STRUCTURE Prof. dr. Manal shaaban Hafez OF HUMAN BODY Professors of Histology and Cell Biology MODULE Dr. Asmaa El shafei Lecturer of Histology and Cell biology Course C...

Medicine and Surgery Program Fall 2023-2024 NORMAL STRUCTURE Prof. dr. Manal shaaban Hafez OF HUMAN BODY Professors of Histology and Cell Biology MODULE Dr. Asmaa El shafei Lecturer of Histology and Cell biology Course Code (BMS 111 )  1. Organelles 2. Inclusions ✓ Living ✓ Non-Living ✓ Permanent ✓ Temporary ✓ Essential ✓ Not essential except?? ✓ Active ✓ Inert ✓ Have vital functions ✓ Metabolic products 3. Cytosol ▪ Semifluid cytoplasmic matrix Faculty of Medicine 3  Cell Organelles Membranous Non-membranous ▪ Covered by membrane ▪ Uncovered by membrane Cell (Plasma) membrane Ribosomes Mitochondria Proteosomes Rough endoplasmic reticulum (rER) Cytoskeleton Smooth endoplasmic reticulum (sER) Golgi apparatus Lysosomes Peroxisomes Faculty of Medicine 4 Definition: ▪ The limiting membrane of the cell. Other names: Plasma membrane or Plasmalemma L.M.: ▪ H&E: Difficult to be seen; Very thin (8-10 nm). ▪ SP. stain: Ag & PAS Ag PAS E.M.: Trilaminar appearance ▪ 2 electron-dense (dark) layers separated by electron-lucent (light) zone. ▪ Cell coat (glycocalyx): on the outer surface only Faculty of Medicine 5 Lipid Component Phospholipid bilayer Cholesterol Protein Component (50%). Peripheral proteins Integral proteins Carbohydrate Component Faculty of Medicine 6  Each phospholipid molecule has: Heads Tails (phosphate group) (Fatty acids) ✓ Charged ✓ Non-charged ✓ Polar ✓ Non-polar ✓ Hydrophilic ✓ Hydrophobic ✓ Directed towards ✓ Directed inwards to the aqueous solutions center facing each other away from aqueous solutions Functions: Selective permeability of cell membrane; allow passage of small, non-polar & fat-soluble substances Faculty of Medicine 7  Fill gaps between the hydrophobic fatty acid tails. Functions: ✓ Stability of the membrane. (Restricting movement of phospholipid molecules) ✓ Modulating membrane fluidity. Faculty of Medicine 8  Peripheral (extrinsic) proteins B. Integral (intrinsic) proteins ✓ Small molecules. ✓ Larger molecules. ✓ Loosely attached to both surfaces of ✓ Firmly attached to cell cell membrane. membrane. ✓ Outside the lipid bilayer. ✓ Embedded in the lipid bilayer. Faculty of Medicine 9 B. Integral (intrinsic) proteins Some proteins are partially embedded in the lipid bilayer. Other proteins extend across the cell membrane from side to side (Transmembrane proteins). Functions of transmembrane proteins: ✓ Channels ✓ Carriers ✓ Receptors Faculty of Medicine 10 Sugar chains: oligosaccharide chains linked to: Membrane proteins: glycoproteins Membrane phospholipids: glycolipids ✓ located on the outer surface only of plasma membrane. Functions: Cell to Cell adhesion. Cell identification. Receptor for ligands. Faculty of Medicine 11  3 Bulk transport Endocytosis: Active movement of substance into the cell by forming vesicles. 3 types Phagocytosis Pinocytosis Receptor mediated endocytosis Exocytosis: Active movement of substance from inside to outside of the cell by forming vesicles Faculty of Medicine 12  Receptor mediated endocytosis Receptors (Integral proteins) accumulate at the cell membrane to bind specific ligands. ✓ They associate with other proteins on the cytoplasmic side called Clathrin to form coated pit. ✓ The coated pit invaginates gradually and pinches off, forming coated vesicle containing ligands and their receptors. Clathrin is dissociated and recycled. ✓ Ex: uptake Faculty of of hormones as GH & uptake of LDL. Medicine 13  Medical application Dwarfism Caused by GH deficiency OR Non-functioning GH receptors at cell membrane of target cells (Level of GH is normal)  Definition: ✓ Membranous organelles responsible for cell respiration & energy production. (Power-houses of the cell). Site: all cells expect RBCs. Number: ✓ More in active cell as liver cell (1000/cell). Histological structure: L.M.: H&E: Cytoplasmic acidophilia (If abundant). (Large number of basic membrane proteins)  SP. stain: appear as granules or rods with Fe Hx & Janus green stains. E.M.: ✓ Oval or rounded vesicles. ✓ Surrounded with two membranes separated by intermembranous space. Outer membrane Inner membrane Smooth & porous ✓ Folded into Cristae Contains transmembrane surface area for attachment proteins called Porins of "ATP synthase“ enzyme (forms ATP in oxidative phosphorylation) Permeable to small molecules less permeable (selective)  E.M.: ✓ The mitochondria, is filled with semifluid called Matrix; contains: - Oxidative enzymes of citric acid cycle. - Mitochondrial DNA , RNA & few ribosomes. - Dense granules rich in Ca2+ (catalysts). Functions: Power Houses: produce ATP. Self-Replicating Organelles: by simple fission. (Mitochondria can synthesize some of their structural proteins by their own DNA & RNA)  SER RER LM basophilia of cytoplasm LM acidophilia of cytoplasm EM flat cisternae or sacs. EM branching tubules. Attached ribosome. No attached ribosome. Lipid and glycogen synthesis. isolated & segregated. Calcium release in muscles. Initial glycosylation of proteins (early Neonatal jaundice. modification of protein), transport newly Detoxification of the drug. formed proteins to Golgi complex  E.M.: Flattened parallel curved saccules; interconnected & arranged one above the other forming a stack. Each stack has 2 surfaces: (Cis face) (Trans face) Immature face Mature face Cis face Usually convex Usually concave Receive transfer From which vesicles originating secretory vesicles from RER and carry containing mature Trans face newly synthesized secretion arise proteins. 19  Functions: Modification Chemical modification of proteins & lipids (for lysosomes , secretion & plasma membrane) by addition of carbohydrates Packaging & Sorting Formation of lysosomes. Discharge secretory products as hormones in secretory vesicles (Exocytosis). 20 Histological structure: L.M.: ✓ They contain hydrolytic enzymes (as acid phosphatase). E.M.: Primary lysosomes Secondary lysosomes Newly released from Formed by fusion of 1ry lysosome 1ry Golgi apparatus with phagosome, pinocytic vesicle or autophagic vacuole 2ry Enzymes Inactive Enzymes Active Homogenous Heterogenous 21  Types of secondary lysosomes: 1. Heterolysosomes (1ry lysosome + Phagosome) 2. Multivesicular bodies: (1ry lysosome + Pinocytic vesicle) 3. Autolysosomes: (1ry lysosome + old organelle) Residual bodies: ▪ Vesicles containing undigested material. (Exocytosis)  ▪ Membranous organelles. ▪ Contain oxidative enzymes as Catalase & Oxidase. ▪ The enzymes produce and degrade H2O2. Importance of peroxisomes:- 1.Synthesis and degradation of hydrogen peroxide kills micro-organisms. 2. helps detoxification of ethanol (alcohol) in the liver. 3. β-oxidation of long chain fatty acids.  Ribosomes are non-membranousorganelles. They are formed of ribonucleoprotein (ribonucleic acid rRNA +Protein). The RNA is synthesized in the nucleolus. It is formed of large and small subunits Free ribosomes synthesis Attached ribosomes Proteins will be Proteins to be used inside stored in RER and transported to Golgi the cell (for mitochondria and complex to form :- nucleus……). 1.Secretory proteins 2.Cell membrane proteins 3.Lysosomes  Protein synthesis Free /polyribosomes Attached ribosomes to RER Structural PTNs Secretory PTNs  Definition: ubiquitin ✓ Barrel shaped organelle responsible for active degradation of cytoplasmic proteins tagged with ubiquitin. Functions: ✓ Remove excess enzyme & unnecessary proteins. ✓ Remove proteins that are incorrectly folded. ✓ Destroy viral proteins. ❑ Defective proteasomes lead to accumulation of Medical unwanted proteins that are related to application Alzheimer’s disease. 27  Diameter: 5-7 nm. Histological structure: L.M.: Immunohistochemical staining E.M.: ✓ Double helix of 2 filaments (F-actin). ✓ Each filament is formed by polymerization of (G-actin) monomers. Stability: Dynamic ✓ Each filament has 2 ends ( + and - ).  Functions: ▪Cell support ▪Contractile ring ▪Muscle contraction Concentrated beneath Interact with myosin Interact with myosin cell membrane during cell division (cell cortex) ▪Cell shape changes (Endocytosis, exocytosis & amoeboid movements) ▪Microvilli core 29  Diameter: 24 nm. Histological structure: L.M.: Immunohistochemical staining E.M.: ✓ Long hollow cylinders with a wall of 13 parallel protofilaments. ✓ Each filament is formed by polymerization of α & B tubulin subunits. ✓ Polymerization of tubulin occurs at microtubular organizing centers (MTOC) ; Centrioles, Basal bodies of cilia & flagella. Stability: Dynamic ✓ Each filament has 2 ends ( + and - ).  Functions: ▪Cell shape ▪Formation of mitotic & support spindle (during cell division) ▪Intracellulartransport ▪ Formation of (Organelles, vesicles & centrioles, cilia & macromolecules) flagella. 31  E.M.: ✓ 2 cylindrical structures, perpendicular to each other & surrounded by a matrix of tubulin (MTOC) = (centrosome) ✓ The wall of each cylinder is formed of 9 bundles of MT, each bundle is formed of 3 MTs (triplets); 3X9= 27 MT. Functions: 1. MTOC; Form mitotic spindle during cell division & regulate growth of new microtubules in non-dividing cells. 2. Share in the formation of cilia & flagella  E.M.: 1- Basal body: =One centriole, embedded in the apical cytoplasm (27 microtubule in 9 triplets). 2- Shaft (axoneme): Finger-like cytoplasmic projection covered by cell membrane. Shaft is formed of 9 peripheral doublets + 2 central singlets formed by polymerization (20 microtubules). Shaft ✓ Repeated beating motion produced by axonemal dynein, moving secretions or particles in one direction as in respiratory & female genital systems. 33  Definition: ✓ Motile processes designed to move the cell itself. Histological structure: ✓ The same structure as axoneme of cilium (9 peripheral doublets + 2 central singlets), but extremely longer. Function: ✓ In human, flagellum forms the tail of sperm, helps its movements 34  H&E H&E A- Stored Food Carbohydrates Fats As glycogen granules in liver & As large globules in fat cells or muscle cells. small droplets in liver cells. PAS L.M.: L.M.: H & E: dissolves leaving H & E: dissolves leaving empty Sudan III empty spaces. spaces. PAS: Magenta red granules. Sudan III: Orange globules. E.M.: Non-membranous electron dense granules.  B- Pigments Endogenous Exogenous (from inside the body) (from outside the body) Hemoglobin (Hb): Red, in RBCs. Carbon & Dust particles: Black, Melanin: Brown to black, in skin in phagocytic cells of lung. & hair. Carotene pigments: Orange, in Lipofuscin: Brown, accumulated carrots. residual bodies in cardiac muscle Tattoo marks: dyes injected & nerve cells. under skin & taken by phagocytic cells.  Definition: ✓ It is the largest membranous organelle inside the cell. ✓ It contains DNA of chromosomes. ✓ It is the site of transcription of 3 types of RNA. ✓ It is essential for life of the cell.  By EM: Components of the nucleus 1. Nuclear envelop 4. Nuclear sap 2. Chromatin 3. Nucleolus  Chromatin Chromatin: is the genetic material consists of DNA double helix + histones + non-histone proteins. In non-dividing nuclei: ✓ Chromatin is the chromosomal material in uncoiled Euchromatin state. In dividing nuclei: ✓ Chromatin start to condense and form chromosomes. ❖ Forms of chromatin: ▪ Euchromatin: Extended chromatin. Heterochromatin ▪ Heterochromatin: Condensed chromatin.  Euchromatin Heterochromatin Extended chromatin Condensed chromatin Not visible by LM Deeply basophilic by LM Electron lucent by EM Electron dense by EM Transcriptionally active Transcriptionally inactive (direct protein synthesis) (don’t direct proteins synthesis) Predominates in nuclei Predominates in nuclei of of active cells as liver inactive cells as small cells lymphocyte The euchromatin/ heterochromatin ratio is indicator of cell activity. Malignant tumor cells have enlarged, abnormal nuclei with abnormal  It composed of 2 main stages:- A) Interphase: ✓ It is the time between two successive cell divisions (90% of the cycle). ✓ It is divided into 3 phases:- ❑Gap 1 (G1) ❑Gap 2 (G2) & ❑Synthesis phases (S) B) Mitosis: cell division.  Apoptosis is active programmed cell death. Apoptotic cells have several morphological features:- 1. Chromatin condensation (pyknotic nucleus). 2. Breaking up of the nucleus. 3. Blebbing of the plasma membrane. 4. The cell shrinks and is fragmented into membrane-enclosed fragments called apoptotic bodies which are phagocytosed by macrophages  Definition: Stem cells are undifferentiated cells that are capable of self-renewal and differentiation (production of different types of specialized cells). E.M: The nucleus : contains mainly euchromatin (active genes) and minimal heterochromatin. The cytoplasm: contains Numerous polyribosomes & mitochondria Types: ▪ Embryonic stem cells in embryo. ▪ Adult stem cells in bone marrow, adipose tissue, placenta , GIT , liver , skin and bl. Vs.  Static cell populations consist of cells that no longer divide ex. cells of the central nervous systems and cardiac muscle cells. Stable cell populations consist of cells that divide episodically and slowly to maintain normal tissue or organ structure. ex. Liver cells, smooth muscle cells and endothelial cells. Rapidly renewing populations ex. blood cells, epithelial cells of the skin and alimentary (GIT) tract. Thank You 46