Cell PDF - Histology Foundation

Histology - Foundation Cell The cell is the - functional & structural unit of the body. A group of cells with similar structure & function...

Histology - Foundation Cell The cell is the - functional & structural unit of the body. A group of cells with similar structure & function will form tissues. - - E These tissues are grouped to form O organs. A group of organs collect to form the body systems. - - Animal cell structure - Cytoskeleton · Resolution Power membraneorganelles Inclusionsis & jjjSid Cell Membrane > cell Diff Functions stored carbohydrates, ) g e... stored lipid (energy. Lysosome , g e. - Genes Mitochondria. Resolution of LM = 0 1 Mm power. Plasma membrane = Plasmalemma LM: It cannot be seen by light microscope because it is too thin to be seen but the conden sation of the stain on the outer surface of the cell membrane marks its. ~ :g 1500 Si LMI EM: gs,S? ~ 1. At Low Magnification: thin dense line 8-10 nm in thickness. 2. With Higher Magnification Magnification: a trilaminar ElecBlack use structure, with an outer (= extracellular leaflet) and an inner ↳ 3 whitecent - (= cytoplasmic leaflet) electron dense lines and a middle 3 - electron lucent zone in between. N.B: The entire structure is known as the unit membrane. Molecular structure of the Cell membrane: 3 Components: 1. Lipid molecules: a. Phospholipids b. Cholesterol ↳ cholesterol 2. Protein molecules. 3. Carbohydrate molecules N.B: The cell membrane & almost all the membranes surrounding the membranous organelles have the same structure except for minor differences. N.B: Membrane phospholipids & the associated proteins are usually present in 1:1 ~phospholipids proportion by weight - 35s phospholipid/1 ! Be , 55 -issl - Si S 1 ·  Histology - Foundation ↳ why are the phospholipids arranged N 6. 1. Lipid Molecules. : Head bilayers- in S ↳ Phosphate Glycero , A. Phospholipids: me Fatty acid (saturated unsaturated) , Hydrocarbonle :Sm Each phospholipid molecule consists of:... Hydrophobic s : Nig 1. One polar hydrophilic head: faces the aqueous media on s - - either side of the membrane. · sNe 2. Two long non polar hydrophobic tails (fatty acids): project X - - - towards the center of the membrane facing each other. They form weak non covalent bonds with each other, holding the bilayer together. S25 Why does the cell membrane appear as a trilaminar structure? · 5 Deposition - of osmium in the hydrophilic heads while the hydrophobic tails remain unstained. - SFunctions of Phospholipid molecules: semipermeability - Prevent passage of: Radissolve Likes of the membrane. 1. Water soluble substances. - 2. Polar ions. es Na , K - Allow passages of: 1. Fat soluble substances. re vitamins : A,D K E - , , 2. Nonpolar substances. · Hormones : Testosterone Progesterone -00 Cortisol - B. Cholesterol: Same semipermeability as phospholipids. ps They are incorporated within the lipid bilayer. Functions of Cholesterol: -55 slisl 1. Stability of the membrane. e &?. 2. Regulation of membrane fluidity in body temperature. 2. Protein Molecules A. Integral Membrane Proteins: They are embedded within the lipid bilayer. Most of these proteins traverse the whole thickness of the membrane and are called transmembrane 3 proteins while others are partially embedded within 2 the membrane. 2  Histology - Foundation There are six functional forms of integral membrane proteins: = · /) , + Sisisilin s · 1. Pumps: transport ions (Na+, K+) actively across the membrane. dis 2. Channels: transport substances passively. os e. g Or. , CO2 M gli - - /S-- 3. Receptors: allow binding of specific molecules e.g., hormone. 4. Enzymes: ATP synthase of the inner mitochondrial membrane and some types of ↳ digestive enzymes in the small intestine. ↳ 5. Linkers: anchor the intracellular cytoskeleton to the - T 9 extracellular matrix. 2 6. Structural proteins: form junctions between neighboring cells. B. Peripheral Membrane Proteins: They are not embedded into lipid bilayer, but they are loosely associated with membrane. - / : 1555232 They are usually located on the cytoplasmic surface of the membrane. Extracellular RBCs m e. g Function: form a link between the cell membrane and the cytoplasmic components.. Attached to protein Glycoprotein 3. Carbohydrate Molecules - > - > Attached to - lipid > - Glycolipid They are present as glycoproteins and glycolipids of the cell membrane. They are oriented towards the outside of the membrane forming the cell coat or glycocalyx. The cell coat is represented by the "fuzzy" material on the outer sacckrides Branching surface of the membrane. Ssj Functions of cell coat: 1. Cellular recognition e.g. the glycocalyx on the surface of red blood cells determines the four blood groups. 2. Cell cell adhesion. 3. Receptor: for ligands by the glycoproteins of the cell membrane. N.B: The glycocalyx vary from species to species/ from cell to cell. This diversity enable membrane carbohydrate to function as markers that distinguish one cell from another (e.g. The ABO blood system) ~"i Receptors cell-cell adhesion cell recognation 3 Receptor cell membrane Protein Protein cett cholesterole  of small molecules Transporting pumps channels I - , with without energy > - or Histology - Foundation Vesicular transport across the cell membrane Mass transfer of materials through the cell membrane occurs by formation of vesicles. 5jo It involves 2 processes: 1. Endocytosis. 2. Exocytosis. 1. Endocytosis Definition: the uptake of material from the extracellular space. It is an active process that involves invagination of the membrane to form a vesicle. /s S4. 3 mechanisms of endocytosis are present in the cell: A. Pinocytosis (cell drinking) : sX receptor Definition: a non selective process, occurs in nearly all cell types for uptake of fluid containing ions and small protein molecules. Vesicle: pinocytotic vesicles are small and have smooth surface. Site: most evident in the endothelium of blood vessels. ~ especially Blood Capillaries Tissues) · , Blood Nutrients/1Jde. wil B. Receptor mediated endocytosis - - Definition: a highly selective process resulting in uptake of specific substances by a specific cell that has receptors for these substances e.g. protein hormones. These receptors are concentrated in specialized regions of the Responsible for Cytoplasm plasma membrane called coated pits (coated by clathrin). as un shaping the 1. When a substance binds to its receptor, clathrin coated pits vesicle. invaginate and give rise to clathrin coated vesicles containing this Extracellular fluid specific substance. 2. Clathrin is lost and recycled leaving uncoated vesicles. separate a Lysosomes the receptors from the C. Phagocytosis (cell eating): entered substances. Definition: ingestion of large solid particles, such as bacteria and cell debris, it is a receptor mediated endocytosis; however, it does not involve formation of coated pits or vesicles. Sites: phagocytes e.g. macrophages& neutrophils. ↓ ↓ 4 CT WBC  Histology - Foundation 1. Binding of the receptor and foreign body results in extension of pseudopodia that engulf the particle. 2. Fusion of the membrane to internalize the particle into the cytoplasm forming a phagosome. 3. The contents of the phagosome are then digested through lysosome. Types of endocytosis Receptor mediated Pinocytosis Phagocytosis endocytosis 1. Endocytosed Fluid containing ions Specific substances Large solid particles material & small molecules. (ligand) e.g. hormone. e.g. bacteria. 2. Receptors for Nonselective. Present. Present. endocytosed material 3. Shape of the Small& smooth. Coated with clathrin. No coated vesicle but vesicle the membrane fused to form phagosomes. 4. Type of cells Nearly all cell types Specific cell that has Phagocytic cells. especially endothelium receptor for specific of blood vessels. substance. 2. Exocytosis Definition: the release of cell products into the extracellular space. During this process, a vesicle moves from the cytoplasm to the cell membrane, fuses with it and discharges its content. There are 2 types of exocytosis: A. Regulated secretion (stimulus dependent) Golgi apparatus I s produced protein * 1. The secretory products become stored forming secretory granules. secretory granules < stored until stimulus. 2. As a result of a stimulus (hormonal or neural stimulus), these vesicles move to the surface and fuse with the cell membrane to pour their contents outside the cell. e.g., occurs during release of the digestive enzymes by the pancreas. 5  Histology - Foundation B. Constitutive secretion The secretory products leave the cell immediately after their synthesis. These cells lack secretory granules. restored protein The secretion is released continuously through secretory vesicles.. E.g. occurs during release of antibodies by plasma cells. Types of exocytosis Regulated secretion Constitutive secretion 1. Stimulus Stimulus dependent No stimulus. They released continuously. Concentrated & stored Leave the cell membrane immediately after 2. Secretory product inside secretory granules. their synthesis. No secretory granules. 3. Example of the Digestive enzymes from Antibodies from plasma cell, fibers released secretion pancreatic cell. secreted from fibroblast. Membrane Recycling During the vesicular transport, the cell membrane is maintained; the excess membrane added to the cell membrane by exocytosis is constantly recycled again into the cytoplasmic compartments by endocytosis. ↳s Pinocytosis - X 6 rephagocytosis X ab Exocytosis -  Histology - Foundation Cell organelles Definition: metabolically active structures carrying out specific - - essential functions. - Types: 1. Membranous organelles: nucleus, endoplasmic reticulum, Golgi G - apparatus, transport vesicles, endosomes, lysosomes, -- mitochondria, and peroxisomes. 3 1 ↳ - 2. Non membranous organelles: ribosomes, centrosome, and the cytoskeleton. - only - 3 G - - & N.B: Haematoxylin and Eosin (H&E): Haematoxylin is a basic violet stain. ① - - Eosin is an acidic pink stain. - ⑦ Basophilic structure= A structure that has affinity - - to stain with basic dyes = acidic in nature So it - stains violet with haematoxylin. - ↳ ribosomes. Nucleus se g. ,. > - & NA RNA Acidophilic or eosinophilic structure= A structure & - - that has affinity to stain with acidic dyes = basic in > - - nature So it stains pink with eosin. ↳ Mitochondria a ↳ e. g. Ribosomes Factories. - - ~ - > - Cytoplasmic Organelles that participate in the process of protein synthesis: · rER-Modification & Transport. 1. Ribosomes u Factories · Golgi apparatuschemicalmodaiting - Definition: granules of nucleoproteins (ribosomal RNA (rRNA) + proteins). - - Site: They are present in all cells especially in protein synthesizing cells. - - - Structure: two subunits; small subunit & large subunit. > - - Synthesis: RNA S : ms / 1. The rRNAs are synthesized inside the nucleolus. => 2. Ribosomal associated proteins are synthesized in the cytoplasm. - & 3. Ribosomal subunits then leave the nucleus, via the nuclear pores, to - enter the cytoplasm. - The small and large subunits are present in the cytosol individually and do - - - not form a ribosome until protein synthesis begins. -messenger (mRNA) G LM: When present in large amounts they cause cytoplasmic = - basophilia.as iii. violet - entral I st 6 EM: Ribosomes are small electron dense granules. - 9  Histology - Foundation Types: A. Free ribosomes: 1. Solitary particles: scattered in the cytoplasm. ⑮ Function: act as a Orig reserve.... => 2. Aggregated (polysomes): clusters of 10 or &1 - => more connected by single strand of mRNA. - producing a - - Proteins require Function of polysomes: responsible for synthesis of - cytosolic protein VIP ~ => - - r e.g. in dividing cells and growing cells, synthesis of hemoglobin in => - developing red blood cells and contractile - protein in muscle cells.-Activ - - & Miosine. & B. Attached ribosomes: these are polysomes - that become attached to the outer membrane of the endoplasmic reticulum. as largesubunit 14 /j 4) - + - -. I h from ribosome attacked to rER, transported to Golgi apparatus Protein synthesized Protein , Hormones Enzymes covered with vesicles Secretory is us e. g. ,. ↳ lysosomes we lysosomal enzymes reside me - Lysosome ↳ cell membrane proteins renewal. Types of Free solitary Free aggregated Attached ribosomes ribosomes ribosomes ribosomes ( polysomes) 1. LM Not seen but in large amount Not seen but in large amount give cytoplasmic basophilia. give cytoplasmic basophilia. Small electron 10 or more ribosomes Small electron dense 2. EM dense particles. connected by a single strand particles attached to rER. of mRNA. 3. Function Reserve. Synthesis of cytosolic proteins Synthesis of secretory (used within the cell) proteins, lysosomal enzymes & membrane proteins. parallel tubes ~ Ribosomes attached. 10  Histology - Foundation 2. Endoplasmic reticulum large The endoplasmic reticulum forms the most extensive membrane = system in the cytoplasm. The ER has- two types: - & - Rough endoplasmic - - reticulum (rER). us vribosomes. - Smooth endoplasmic reticulum (sER). u X ribosomes. --- - Both types form a single membrane system. A. Rough Endoplasmic Reticulum 6 (rER): - - - LM: When present in large amounts they cause cytoplasmic basophilia due - to their attached ribosomes. - EM: 1. It consists of interconnected parallel flattened sacs called - ~ 2 cisternae. - - as - - 9161 Cribosomes 2. Its outer surface is studded with ribosomes, resting by Cisterae - > - - their large subunit on the membrane. - 3. It is continuous with the outer membrane of the nuclear envelope. - 4. The lumen contains flocculent material that represents newly - formed protein. - Functions: insulin digestive enzymes. ↑ - , 1. Synthesis of secretory proteins, lysosomal enzymes and proteins - - inserted into the cytoplasmic membranes. - 2. Post translational modification of the newly formed protein e.g.folding, sulfation and initial glycosylation. Golgi apparatus.is & 3. Transport the newly synthesized protein to the Golgi body by transport vesicles. - e Sites: Protein synthesizing & secreting cells e.g. liver cells, pancreatic acini, fibroblasts - - > - CT = Fibers - and plasma cells. - Antibodies Plasma - Protein di smembranous as organell. B. Smooth Endoplasmic Reticulum (sER) s ↳ composed of. protein. "Si "Fish ! Basic in nature 4. AA = type LM: Cells with large amounts of sER exhibit cytoplasmic eosinophilia.& - - > - - - EM: - 1. It consists of close network of interconnectedW branching - tubules and vesicles. 2. The membranes have smooth surface. - 3. The membranes of the sER are continuous with that of rER. - - 13  Histology - Foundation Functions: 1. Synthesis of membrane lipids; the phospholipids and cholesterol. - - 2. Synthesis of steroid hormones. - us Testosterone Progesteronee , , 3. Synthesis of glycogen in liver. - Estrogen , Cortisol (Supravenal gland). 4. Detoxification of toxic substances e.g. alcohol and drugs. - - - 5. Regulation of calcium ions during muscle contraction. ~ - Sarcoplasmic Reticulum - - Sites: steroid secreting cells (in the adrenal cortex, testis and ovary), liver cells & muscles. - - - - - - - Types of endoplasmic Rough endoplasmic reticulum Smooth endoplasmic reticulum reticulum 1. LM Not seen but in large amount give Not seen but in large amount give cytoplasmic basophilia. cytoplasmic acidophilia. 2. EM Parallel, flattened interconnected Interconnected branching tubules tubules. Studded with ribosomes. and vesicles. No ribosomes. - - - - 3. Functions 1. Synthesis of secretory proteins, 1. Synthesis of lipid & cholesterol of lysosomal enzymes& membrane the cell membrane. proteins. 2. Synthesis of steroid hormones. 2. Post translational modification of 3. Synthesis of glycogen. - protein. 4. Detoxification of toxic substances. 3. Transport protein to Golgi. 5. Storage of calcium in muscles. 4. Sites Protein secreting cells e.g. liver , Steroid secreting cells, liver & muscles. fibroblasts. X Parallel tubes Xvesicles (RNA) ↳ Active & usecretory Mucine. Proteins SERmeLipids · - ·y some- 14  Histology - Foundation 3. Golgi apparatus Nucleus LM: shighly glycoselated membrane. - 1. It is not stained with H&E in routine histological sections. - - - 2. H&E stained sections of the cells synthesizing protein, its site secretory - as - XHSE - could be seen as negative Golgi image e.g. plasma cells. antibodies > as Produce 3. It can be seen in histological sections stained with silver stain. - ~Eidedemesug - EM: Brown spring - 1. It consists of saccules or cisternae called the Golgi stacks. - - 2. Each stack consists ofE 4 6 cisternae (flattened, curved, membrane cup shaped Tconnected => - - - bounded, slightly expanded at the ends). -Parallel - ~ - - - 3. The Golgi stack is cup shaped with a convex surface and a concave surface: - - - a) The cis face (forming face; immature face): ↳VERS i Trans So, i Stace - - transport reside - - Convex in shape. a => Golgi apparatus -. - Lies near to the rER. = "immature Protein" - Cis-face - It is the site where the transport vesicles containing the newly formed proteins from rER enter the Golgi for further processing. - - - - b) The trans face (secretory face; mature face): S - - - Concave in shape.* - - It is the site where the modified protein is packaged and released from the Golgi in & - large secretory vesicles. - - - c) The medial compartment: Between the cis & trans compartments. - - Functions: - 1. Post translational modifications of proteins e.g.removal, addition or modification of sugars - 2. Packaging of different proteins in membrane bounded vesicles. - > - - · - - 3. Sorting and targeting of vesicles to the right destination: Mini - Formation of lysosomes. - 2 - - - - Formation of secretory granules for exocytosis. - Secretory resides - Membrane recycling. - Sites: Protein synthesizing and secretory cells. ↳ N.B: or Glycoprotein. - Cytoplasmic Organelles that participate in the process of Protein synthesis: - - 1. Ribosomes (factories) - 2. Rough endoplasmic reticulum (modification& transport) - 3. Golgi apparatus (chemical modification,package,sorting& targeting) 17  Histology - Foundation share in Endocytosis Body 4. Endosomes Definition: are system of vesicles and tubules - = > - involved in the endocytotic pathway. - Types: A. Early endosomes: - - Site: at the periphery of the cell as a part in the -... · pathway of the receptor mediated endocytosis. on - -Endocytosis (1 - Content: the receptors ligands complex. - - The membrane of the endosomes pumps H+ ions > - into its interior lowers the pH of endosomes to - less than 6 uncoupling of the receptors and the ligands. => -- - - The receptors recycle to the cell membrane and the ligands move to the late endosomes. - - - - B. Late endosomes: - - Site: deep within the cytoplasm near the Golgi - - complex. - => - - They receive: ⑤5. - 1. The ligands from early endosomes. => Non-secre > Protein tory2. Clathrin coated vesicles containing lysosomal enzymes from Golgi complex. - - PH: 5.5. (The enzymes become active at the acidic pH of the late endosome). - - - The lysosomal enzymes in the late endosome begin to degrade the ligands accompanied - - by further decrease in the internal pH which then "mature" to form lysosomes. lysosomalenzyme - M id - = =>- - LPHd Lysosome J5d Types of Early endosome Late endosome endosomes 1. Site Periphery of cytoplasm. Deep in cytoplasm , near Golgi. 2. Content Receptor ligand complex. 1. Ligands from early endosome. 2. Lysosomal enzymes from Golgi. 3. Function Uncoupling of the receptor from Lysosomal enzymes begin to degrade ligand. ligands, then the late endosome matures to lysosome. 4. pH Less than 6. 5.5. 20  Histology - Foundation 5. Lysosomes Definition: membrane bounded organelle containing about 40 types of - acid hydrolytic digestive enzymes (proteases, nucleases, phosphatases, - -- - - and lipases). - Function: They are responsible for intracellular digestion of different materials. - - Synthesis: by a gradual maturation process as by fusion of the clathrin coated vesicles coming from Golgi complex with late endosomes. - - - - - Lysosome has a surrounding membrane with unique phospholipids & - - - specialized glycoproteins line the lysosomal membrane from inside that prevents: - - - 1. The leak out of the enzymes to the cytoplasm. => 2. Protects the membrane from hydrolysis by its own enzymes. - > - - - - If a lysosome leaks its contents, the released enzymes > - es- would be inactive because of neutral pH of the cytoplasm. Xseeu & 5% 59 - adi - LM: They can be recognized by several histochemical methods = · 2 - - used to demonstrate the lysosomal enzymes. - EM: Lysosomes are heterogeneous in shape and the appearance of their interior. Some are - - > & electron dense, others show electron lucent areas. - Site: - are abundant in phagocytic cells. - Pathways for intracellular digestion by lysosomes: - 1. Extracellular small particles: internalized by pinocytosis and - - - receptor mediated endocytosis early endosome => late endosome where the - endocytosed materials are degraded by the lysosomal hydrolases. -- 2. Extracellular large particles: are engulfed in the process of phagocytosis forms a - - - phagosome fuses with a late endosome. - & 50 - e 3. Intracellular particles: are removed by a process called autophagy - > - the enclosure of this organelle by membranes from sER forms an - = -- autophagosome fuses with a late endosome. & - - lipids - The hydrolytic enzymes digest most of the content of the lysosomes. e g.. & - - Any indigestible substances remain in lysosomes forming residual bodies. - In long lived cells, accumulated residual bodies indicate cellular aging and are called - - & lipofuscin pigments.- - e g.. Live Heart Neurons. - ibosomes - rER 23 out & - X > - Golgi - - X 2 - = X  Histology - Foundation 6. Mitochondria Function: Powerhouses of the cell as they are the sites of adenosine triphosphate (ATP) - - production. us cell-respiration > Sites: All cells EXCEPT terminal keratocytes & RBCs. - - - Structure: - LM: When present in large numbers contribute to the cytoplasmic - eosinophilia (due to large amount of membrane they contain). Silver stain e "Small granules" EM: ↳ Basic membrane ⑪ Mitochondria a. Membrane bounded organelles. · A Nucleus -H present - - the only & are structures 2 membranes b. Surrounded by two membranes: outer and with - inner, which define two mitochondrial compartments: - inside the cell & - - The intermembranous > space: between the two membranes. - - The matrix space: enclosed by the inner membrane. - 1. The outer mitochondrial membrane - - - It is smooth and porous. z 2 Mi - Function: allows passage of small molecules due to the - presence of specific transmembrane proteins called porins. - 2. The inner mitochondrial membrane * a. Folded into cristae which increase its surface area; the number of - - cristae is greater in cells of greater demand for ATP. - - Types of cristae: - Lamellar Cristae. Tubular Cristae. Shelf Like. Lamellar cristae: most of cells. & Tubular cristae: steroid secreting cells. b. Impermeable to ions and small molecules due to presence of phospholipid called & - -- - cardiolipin. & b - Function: contains the enzymes of the electron transport system (respiratory chain - - ↳ enzymes) and the ATP synthase (known as elementary particles attached to the cristae - - and their heads are projecting toward the matrix like a lollypop). - 3. Intermembranous space as through Porous Entered. - Contains substances diffusing from the cytoplasm Y - through the outer membrane and ions pumped out of the 2 - - matrix space through the inner membrane. 26  Histology - Foundation 4. Matrix space - Surrounded by the inner mitochondrial membrane. - - - Functions: a. Enzymes involved in mitochondrial functions as - citric acid cycle. - b. Mitochondrial DNA and few ribosomes. - c. Matrix granules: store calcium ions, play a role in mitochondrial regulation of Ca 2+ intracellular - - => concentration. The genetic system of mitochondria: - The mitochondrial DNA: - - a. A circular molecule. produce protein - - b. Limited coding capacity.. to hability - => c. Represents 1% of the total DNA of the cell. & - Function: Mitochondria can synthesize some of their structural & proteins by their own RNAs. - Most of the mitochondrial proteins are encoded by the - nuclear DNA and are synthesized in the cytoplasm and - - - imported into mitochondria. & Mitochondria are self replicating organelles. - - How do mitochondria adapt to its function? (E/M) a. Outer membrane: smooth &porous contains mitochondrial porins allow easy passage of small molecules. b. Inner membrane is folded into numerous cristae increase surface area for energy - production. c. Inner membrane contains cardiolipin make it highly impermeable to ions & small - molecules. d. Matrix space: contains enzymes for citric -- acid cycle, mito DNA & ribosomes synthesize some of their structural proteins, also contains matrix granules store Ca & - - - thus play an important role in regulation of intracellular Ca concentration. - What is your source of mitochondria? S * Mother "Egg cell's mitochondria & - 27  Histology - Foundation 7. Peroxisome- - Definition: membrane bounded organelles that contain oxidative enzymes. - Peroxisomes possess no genetic material of their own. - - Structure of Peroxisome - LM: They are not seen by H&E stain. EM: - a. Small, spherical bodies with fine granular electron dense content. - - - b. Surrounded by a single membrane. Functions of peroxisomes - a. β oxidation of long chain fatty acids to release energy. However, they differ from mitochondria in that they are unable to store this energy in - - - - the form of ATP. This energy is released as heat to maintain body temperature. = - - b. Generation of hydrogen peroxide, which detoxifies toxic agents. H202 - - => c. Contain catalase enzyme that converts the excess hydrogen peroxide into water, thus - - - protecting the cell. - - > - d. Detoxification of alcohol in cooperation with the smooth endoplasmic reticulum in the - liver. - - 6 => Mitochondria Peroxisome 1. LM Not seen by H&E except in large Not seen. amount cause cytoplasmic acidophilia. By special stain (silver stain) appear as brownish granules. 2. EM Double membrane: outer is smooth, and Single membrane enclosed fine inner is folded into cristae enclosed granular contents. matrix space. 3. Function Production of energy & store it in the 1. Produce energy & released it in the form of ATP. form of heat (unable to store it). 2. Produce hydrogen peroxide. 3. Convert excess hydrogen peroxide into water. 4. Detoxification of toxic substances. 4. Sites All body cells except red blood cells & Many cells especially liver keratinocytes. 5. Genetic Present Absent material 30 ~ Double membrane Mitochondria -Cristae X (outer) * (Matrix space) X impermeable. - inner membrane  Histology - Foundation 8. Cytoskeleton The cytoskeleton is a network of structural proteins (non-membranous cell organelles). - Types of cytoskeletons: - - 3 types, depending on their thickness& their structural proteins: E Intermediate filaments Microfilaments Microtubul - Protein 1. Microfilaments (actin filaments) 8 - Diameter: 7 nm. XRoutine& & solsing abody Stain LM: can be visualized by using immunohistochemical staining. - - - - EM:Othin electron dense E filaments. CHAE) Structural proteins: monomers of G actin (globular actin) - - polymerize to form F actin (filamentous actin) arranged as - a double helix. + G- activ -xpermenant r They are& dynamic structures that can elongate & shorten. =G-activ - Functions of microfilaments: - A. Cell motility for: Plasa - G - Cell migration. mapeendopodia - - - Cytoplasmic streaming: minus- end - G during movement of organelles and transport of vesicles.rewaving - move. - Cytokinesis: formation of contractile ring during cell division. - - - Muscle contraction associated with myosin. und sactin/1JjSj! g.. e /I. 9 Smyosin B. Structural role: · -... I - Maintenance of the cell shape. - - - Formation the core - o of microvilli. folds Irregular ↑ cell surface · 33  Histology - Foundation 2. Microtubules O Diameter: 25 nm. T LM picture: by using immunohistochemical staining. -X HAE. EM picture:W fine tubules. Structural proteins: 2 subunits JA. A globular protein dimer called tubulin (each is composed of - - alpha and beta subunits). & monomer. & > - B. Chains of tubulin dimers form a protofilament. - C. The wall of a microtubule is made up of 13 - - protofilaments that run longitudinally. - - Motor proteins associated with - microtubules: Kinesin & dynein; they - = ↳ Ss5is use ATP to provide energy for. - · movement of vesicles and organelles & - along the microtubules. - Microtubules are[ dynamic structures; can elongate & shorten ↳ Itubulin Dimer = - Functions of microtubules: - a. Transport: of organelles & vesicles in the cytoplasm. -- - b. Structural role: - Asidi - - Formation of the mitotic spindle. - - Formation of- centrioles, cilia & flagella. The microtubule organizing centers: a. Centriole which forms the mitotic spindle. - - & b. The basal bodies of cilia and flagella. = mail = - - - of spe - - 3. Intermediate filaments : O Diameter:10 G nm LM: by using immunohistochemical staining. > EM: electronG dense filamentsG thicker than actin filaments. Structural proteins: like woven ropes. - - Function of intermediate filaments: They are the G most stable (not dynamic) types of the cytoskeletons thus they 0- play a structural role. shape maintenance. 34  Histology - Foundation Classification Of Intermediate Filaments: According to their protein composition and their cellular distribution into: - A. Cytoplasmic: - ⑧ 1. Keratin: epithelial cells. Sin. originated from mesoderms useg - - cell 2. Vimentin: in the cells of mesenchymal origin e.g., fibroblasts.se - = > 3. Desmin: muscle cells. - - - 4. Glial fibrillary acidic protein: neuroglia. - as Calial cells 5. Neurofilaments: nerve cells. - - Lamin 6B. Nuclear: Q : (Xinin lines the inner nuclear envelope Lamins: lining the inner nuclear envelope. of the cell. N.B: - The intermediate filaments (except for the lamins) are located in specific tissue types; - - they can be used to determine the origin of cancer by immunohistochemical staining. > - - Cytoskeleton Microfilaments Microtubules Intermediate filaments 1. Diameter 7 nm. 25 nm. 10 nm. 2. LM Seen only by Seen only by Seen only by immunohistochemistry. immunohistochemistry. immunohistochemistry. 3. EM Thin electron dense Fine tubules. Thicker electron dense filaments. filaments. 4. Structural Monomers of G actin Tubulin dimer polymerize Woven ropes. proteins polymerize to form F to protofilaments. actin. 13 protofilaments form a microtubule, 5. Functions Dynamic Dynamic. Not dynamic. 1. Muscle contraction. 1. Transport of Structural support. 2. Contractile ring in cell organelles & vesicles. division. 2. Formation of 3. Pseudopodia in centrioles, cilia & migration. flagella. 4. Microvilli. 5. Cytoplasmic streaming. 37  Histology - Foundation Centrosome Definition: a non membranous organelle. - EM: 1. It is formed of 2 centrioles, perpendicular to - each other. =29X3 2. Each centriole is composed of 9 triplets of microtubules (a sum of - 27 microtubules). O 3. Each triplet is composed of three microtubules (one complete; - formed of 13 protofilaments and 2 incomplete; each is formed of - => 10 protofilaments). S : 3 si * - > S! Functions of centrosome: ·s.23Gile 1. It is the microtubule organizing center. - 2. Formation of mitotic spindles. - ~ 3. Formation of cilia & flagella. sperm. - 3 empodi glass Cytoplasmic Inclusions 1. Stored Food: Pale Vaculated R coea appearance - A. O Glycogen S Storage form of carbohydrates. - Function: source of energy. - - Sites: mainly in liver & muscle cells. - LM: - H&E: not visualized as they dissolve during preparation of the specimen leaving a - - pale vacuolated cytoplasm. - Periodic acid Schiff: appears magenta red. - - - Best's carmine: appears bright red. - => EM:- dense granules, larger than ribosomes. - - In cytoplasm of hepatocytes, glycogen appears - as- rosette shaped aggregates 38  Histology - Foundation B. Lipids O Function: 1. Source of energy. - 2. Synthesis of membranes & steroid hormones. - - Sites: stored in the adipocytes; many other cell types - -b contain few small lipid droplets. mesincymerizarigi) -vimentin / 1 intermediate - · filaments LM: - H&E: not visualized because they dissolve during - - preparation of the specimen leaving a pale vacuolated - - cytoplasm. - Osmium tetroxide: appear black. - - or C. Proteins & white or black- > Depending EM: grey non membrane bounded small droplets or large globules. the degree of saturation.acids fatty ⑧ Site: in protein - synthesizing cells e.g. salivary gland and pancreas. Digestive ·. - enzymesi LM: eosinophilic zymogen granules. LArquenin (AA) L Granules inactive form EM: homogenous electron dense membrane bounded with an 6 secretory granules. -. 1s &s s ~ Enzymes and secreted are secreted when needed (stimulated) heterogenous - ribosomes by "Regulated Exocytosis" 2. Pigments: - - & A. Endogenous pigments- 6 1. Hemoglobin: in red blood cells. - - 2. Hemosiderin: brownish granules in phagocytic cells of - - - liver and spleen following phagocytosis of old - - - - RBCs. Melanin pigment: brown to black granules. Melanocyte a ~ - 3. - Hair. 4. Lipofuscin pigment: yellow brown pigment - present in cells with long life span. * Accumulation of residual bodies us lysosomes = by B. Exogenous pigments - Liver cardiac 8 muscles. , Nervous cells 1. Tattooing: colored pigments are injected into the deep layers of the - - skin. - & 2. Dust & smokes: in lung of smokers and people living - in polluted areas. & - - - 39  Histology - Foundation Nucleus It is the largest membranous organelle of the cell. Functions: 1. It contains the chromosomes. 2. Contains the machinery for DNA replication& RNA transcription. Number: 1. Single: most of the cells. 2. Binucleated: liver cells.inst activity 3. Multinucleated: skeletal muscle fibers. 3 Fusion of 4. Absent: RBCs. many cells Cytoplasmic Inclusions A. The Nuclear Envelope:~ It consists of two parallel membranes; outer & inner separated by the perinuclear cisterna. It is perforated by the nuclear pores which provide - - a channel between the nucleus and cytoplasm. - - 1. The outer membrane: It is continuous with the rough endoplasmic reticulum. It is - covered with ribosomes on its outer surface. - - Function: The ribosomes synthesize the transmembrane - proteins of the nuclear membranes. - 2. The inner membrane: It is supported at its inner surface by the lamins.