Histology and Cytology PDF

‫سججامعة بنى سوٌف‬ ‫كلٌة الطب البٌطري‬ ‫قسم الهستولوجً‬ ‫أهلا بكم‬  CYTOLOGY By Prof.Dr/Khaled Mazher Professor and Chairman of Cytology and Histology of the department  Histology Definition The science which deals with the microsco...

‫سججامعة بنى سوٌف‬ ‫كلٌة الطب البٌطري‬ ‫قسم الهستولوجً‬ ‫أهلا بكم‬  CYTOLOGY By Prof.Dr/Khaled Mazher Professor and Chairman of Cytology and Histology of the department  Histology Definition The science which deals with the microscopic structure of all body tissues and organs It also called microscopic anatomy Histology includes: 1- Cytology 2- General histology: - Epithelial tissue - Connective tissue - muscular tissue - Nervous tissue 3- Special histology: - respiratory system - cardiovascular system - digestive system - Urinary system - lymphatic system - endocrine system - male genital system - female genital system  Cytology The term cytology (CYTO=CELL, OLOGY=SCIENCE) deals with the microscopic and ultrastructure of the different cell types and their constituents in addition to their functions and functional correlates. THE CELL Defenition: the cell is structural and functional unit of any living organism. In some animals the cell can exist independently.  Shape: It may be spherical, star shape, cuboidal, oval, columnar, flat or polyhedral. Cell size: - In mammals, cells are rarely seen by naked eye. - They are measured by microns. -The smallest cell is measured about 4 µm (granular cells in cerebellum) - The largest one is about 300 µm (megakaryocyte in bone marrow). - Some cells are greatly elongated so that their length is measured in centimeters (skeletal muscle cells) or even in meters (nerve cells). Function: secretion, contraction, respiration, sensation, growth, reproduction and absorption. Structure: the living cells either eukaryotic (contain true nucleus) or prokaryotic (contain only chromatin material). The animal cell is eukaryotic type consists of cytoplasm and nucleus  Cytolasm 1- Cytosol: it is the fluid component consists of water, lipid, proteins, carbohydrates, RNA, minerals, ions, salts, metabolites, O2 and CO2. The cytosol plays an important role in cell metabolism and cell movement. 2- Organelles: they are living and permanent structures essential for all nucleated cells. They also have vital functions and are metabolically active. 3- Inclusions: they are non living and temporary structures not essential for each cell. They result from the cell activity and are metabolically inactive. 10/16/2021 Dr. Hariom Yadav  The cytoplasmic organells Definition: they are living and permanent intracellular structures that carry out the vital functions of the cell. They are classified according to the presence or absence of membrane into membranous and non membranous organelles. Membranous organelles Non membranous organelles Surrounded with membrane not surrounded by membrane Have metabolic enzymes free from enzymes It includes: It includes 1-Cell membrane 1-Ribosomes 2-Mitochondria 2-Cytoskeleton: 3-Rough endoplasmic reticulum a-microtubules 4-Smooth endoplasmic reticulum b- microfilaments 5-Golgi apparatus 6-Lysosmes  1-The cell membrane It also called plasma membrane or plasmalemma Definition: it is a limiting membrane surrounding the cell cytoplasm externally. It measures about 7.5-10 nm in thickness. LM: can not be seen by light microscopy while the cell coat (the external part of the cell membrane) can be demonstrated when stained with PAS (pink) or silver stains (black). EM: It appears as tri laminar membrane as it formed from two electron dense dark lines separated by an electron lucent clear one. It also called unit membrane.  Molecular structure of the cell membrane: 1-lipid components: includes phospholipids and cholesterol. A- phospholipid molecules: appear as two layers (lipid bilayer), each layer has polar and non polar ends * hydrophilic polar ends: they are charged ends like water and directed outward the cell membrane. * hydrophobic non polar ends (tails): non charged, do not like water and directed inward the cell membrane, B-Cholesterol molecules: they are insert themselves among the tails of the phospholipids. 2- Protein component: A- Integral protein: embedded in the lipid bilayer and some of them extend across the cell membrane from side to side (transmembranous protein). B- Peripheral protein: small molecules loosely attached to the inner surfaces of the cell membrane. 3- Carbohydrate component: A- Glycoproteins: oligosaccharide chains linked to the protein moloecules B- glycolipids: oligosaccharide chains linked to the phospholipid moloecules  Cell coat (glycocalyx): it represents the external surface of the cell membrane formed of glycoproteins and glycolipids. It includes specific receptors for drugs and hormones. Functions of the cell coat: 1-cell immunity 2- cell adhesion 3- cell protection 4- cell recognition  Functions of the cell membrane 1-passive transport: water, ions and dissolved gasses enter the cell according to their concentration. 2-facilitated transport: through the integral proteins e.g. glucose and amino acids 3-active transport: against the concentration gradient so it needs energy as sodium potassium pump. 4- endocytosis: bulk uptake of substance across the cell membrane, it may be: A- phagocytosis: the cell engulf an extra cellular material as bacteria, virus or damaged cell. The engulfed material called phagosome B- pinocytosis: the cell engulf fluid material. The engulfed material called pinosome. 5- exocytosis: a membranous cytoplasmic vesicle fuses with the cell membrane to release its content outside the cell.  2- Mitochondria Definition: one of the membranous organelles responsible for energy production. They consider the power house of the cell. Site: they present in the part of the cytoplasm where the energy is needed as beside rER in secretory cells, between myofibrils in muscle cells and in the basal infolding in the ion transport cells. Number: their number varies according to the activity of the cell. Mitochondria are self replicating organelle, so they can increase their number as they contain DNA. LM: appear as dark blue dots when stained with iron hematoxylin appear as green dots when stained with genus green. EM Functions: 1- production of energy from metabolites present in the cytoplasm by Kreb`s cycle. 2- storage of energy as ATP molecules by oxidative phosphorylation. 3- Rough endoplasmic reticulum (rER) Definition: one of the membranous organelles responsible for protein synthesis. Present mainly in protein secreting cells. Site: present around the nucleus and associated with the nuclear membrane. LM: either localized or diffused basophilic dots, in pancreatic cells (basal basophilia) or diffused as in plasma cell (diffused basophilia).  EM: appear as parallel flattened membranous sacs or cisternae connected with each other by short canaleculi. These membranous sacs are studded with polyribosomes on a special site which give this organelle its rough appearance.  Functions: 1-Synthesis of protein for export outside the cell as polypeptide hormones and digestive enzymes. 2- Synthesis of hydrolytic enzymes of primary lysosome. 3- Act as intracellular pathway for some substances.  4- Smooth endoplasmic reticulum Definition: one of the membranous organelles responsible for steroid synthesis Site: well developed in steroid hormone secreting cells (adrenal cortex, testis and ovary), fat cells and liver cells. LM: cannot be seen. EM: Branching and anastomosing intercommunicating tubules with variable shaped cisternae. They may be continuous with rER but they lacking attached ribosomes. 10/16/2021 Dr. Hariom Yadav  Functions: 1- synthesis of steroid hormones as cortisone, esterogen and progesterone. 2- Act as a pump releasing calcium ions during muscle contraction. 3- Synthesis of cholesterol and phospholipids. 4- Act as intracellular pathway for some substances. 5- Detoxication of drugs, hormones and some chemicals in liver cell.  5- Golgi apparatus Definition: one of the membranous organelles responsible for secretion, so it is well developed in secretory cells. Site: - in pancreatic cells present supra nuclear (in the apical part). - In nerve cells present peri nuclear (around the nucleus). LM: it can be demonstrated by silver stains as network of brownish granules and fibers. In plasma cell, which characterized by diffuse basophilia, Golgi apparatus could be recognized as a pale unstained area near the nucleus called negative Golgi image. EM: Golgi apparatus consists of: 1-Golgi stalks or membranous saccules: several parallel, flat and curved saccules with dilated ends. These saccules are interconnected with each other. Each saccule has two surfaces: a-immature convex surface: receives transfer vesicles which carry crude protein from rER. b- Mature concave surface: from which the secretory vesicles bud off carrying protein ready for secretion. 2-Transfer or Micrivesicles: small membrane bound vesicles carrying crude protein from rER to the immature surface of the Golgi stalks. 3-Secretory or Macrovesicles: large membrane bound vesicles arise from the mature active surface of Golgi stalks carrying protein ready for secretion. Dr. Hariom Yadav 10/16/2021 Dr. Hariom Yadav Functions: 1- concentration, storage and packing of proteins recieved from rER. 2- conjugation of protein with carbohydrates, sulphates and salts. 3- formation of coated vesicles and primary lysosomes. 4- renewal and maintenance of the cell membrane.  6- Lysosome Definition: one of the membranous organelles contains hydrolytic enzymes and responsible for cellular digestion. Number: a huge number of primary lysosomes present in the phagocytic cells as monocyte, neutrophils, lymphocytes and macrophages. Origin: the hydrolytic enzymes are synthesized in the rER then transferred to Golgi apparatus then released as primary lysosomes. LM: can not be seen but the acid phosphatase enzyme inside the lysosome could be detected by histochemical reactions. EM: Primary lysosomes: membrane bound spherical vesicles contain hydrolytic enzymes. They have homogenous electron density. Secondary lysosomes: when the primary lysosome fuses with any intra cytoplasmic vesicle either exogenous or endogenous it becomes a secondary lysosome. The secondary lysosome appear heterogenous in electron density due to digested and undigested particles. 10/16/2021 Dr. Hariom Yadav Types of secondary lysosomes: Heterolysosome: fusion of the primary lysosome with a phagocytic vesicle as dust, bacteria or virus Multivesicular body: fusion of the primary lysosome with a pinocytotic vesicle Autophagosome: fusion of the primary lysosome with an old organelle as mitochondria or ER leading to its hydrolysis Residual body: the undigested materials inside the lysosome as dust retained as residual body then the cell expelled it by exocytosis (cytostol) or it accumulate inside the cell as lipofuscin pigment in nerve cells. Functions: 1- protection of the cell by digestion of the engulfed bacterea or viruses. 2- Maintain the cell health by continuous removal and elimination of the old organelles. 3- Autolysis after cell death the lysosomal enzymes liberated and hydrolyse the cell constituents. 4- Helps in fertilization of the ova by the acrosomal enzymes. 5- Formation of thyroid hormones by digestion of colloid.  Non membranous organelles 1- Ribosomes Definition: they are non membranous electron dense bodies present in all cells but increased greatly in protein producing cells. LM: may be diffused (embryonic cells), localized (pancreatic cells) or focal (Nissl`s granules of nerve cells). EM: a ribosome appears as small electron dense granule formed of small and large subunits. The large subunit contains a groove in its center housing the polypeptide chain. The two subunits connected together by mRNA. More than one ribosomes are connected together by mRNA forming polyribosomes, the latter may be free or attached. Functions: -Free ribosomes: synthesize protein to be used inside the cell as glycolytic enzymes. -Attached ribosomes: they form the proteins that secreted outside the cells as hormones and enzymes.  2-Cytoskeleton The term cytoskeleton refers to a complex network of microtubules and microfilaments A-Microtubules : Definition: they are fine tubules of variable lengths and regular diameter of about 25nm. LM: can not be seen but they could be demonstrated by immunohistochemistry EM: they appear as fine tubules formed of alpha and beta tubulin protein molecules arrange into 13 protofilaments Forms: 1- Dynamic form with continuous assembly and disassembly helping in cell movement 2- Stable or organized form represented by centerioles, cilia and flagella. Functions: 1-determination of the cell shape 2-formation of mitotic spindle during cell division 3-intracellular 10/16/2021 transport of macromolecules Dr. Hariom Yadav  Centerioles Definition: one of the non membranous organelles formed of highly organized microtubules. LM: appear as two dark bodies near the nucleus when stained with iron hematoxylin. EM: appear as two perpendicular cylinders, each one formed of nine triplets microtubules connected with each other by protein link. The two cylinders are surrounded by matrix of tubulin called centromere. Functions: 1- formation of mitotic spindles during mitosis 2- it forms the basal body of the cilia and flagella. Yadav  Cilia Definition: they are motile processes formed of a core of microtubules covered by cell membrane. Origin: the centeriole duplicate several times forming basal bodies of the cilia that migrate to the apical part of the cytoplasm, then shafts grow up. LM: appear as hair like striations EM: each cilium is formed of a basal body, a shaft and a rootlet 1-the basal body: nine triplets microtubules resembling the centeriole 2- the shaft: nine doublets microtubules and two singlets at the center 3- the rootlet: nine singlets microtibules fix the basal body and the shaft to the cytoplasm. Dr. Hariom Yadav  B-Microfilaments Definition: they are thread like structures distributed allover the cytoplasm and constitute a part of the cytoskeleton L/M: Some of them appear in ordinary sections (Tonofibrils & Myofibrils), others require a special stain (Neurofibrils are argyrophilic). They appear as very fine lines. E/M: They appear as very fine thin threads of varying length and diameter. In C.S they appear as minute dots. Functions: 1-Microfilaments in every cell act as a cytoskeleton. 2-Myofibrils in muscle cells contract muscle fibers. 3-Tonofibrils in epithelial cells connect adjacent cells together.  Cytoplasmic inclusions They are temporary, nonliving and nonessential metabolically inactive materials in the cytoplasm. 1- Stored food a- Carbohydrates: - liver and muscle in the form of glycogen. LM. As red granules when stained with Best`s carmine or pink granules when stained by PAS stain. b- Fats: -stored in special cells called fat cells or adipocytes as large globules LM. as black spots when stained with Sudan black or osmic acid stains, and orange colour when stained with Sudan III. 2- Pigments -Endogenous pigments: as hemoglobin in RBCs, melanin in melanocytes and lipofuscin in cardiac and nerve cells. -Exogenous pigments: phagocytosed by the cell from outside as dust particles in lung, tattoo marks in skin and carotene pigments. 3-Secretory granules:  Nucleus Definition: it is the largest and most prominent and important component of the cell. It is present in all true cells Shape: the nucleus may be spherical, oval, flattened, lobulated, segmented or kidney-shape. Position: The nucleus usually take a central position but sometimes it may be eccentric, basal or peripheral. Number: the cell may be mononucleated (one nucleus in each cell), binucleated (two nuclei in each cell as liver cell) or multinucleated (more than two nuclei in each cell as skeletal muscle cell). Components of the nucleus: 1- Nuclear membrane 3- Nuclear sap 2- Nuclear chromatin 4- Nucleolus 10/16/2021 Dr. Hariom Yadav  The nucleolus: It is a rounded or oval deeply basophilic mass formed of rRNA and surrounded by chromatin material. The nucleus contains one or more nucleoli. EM: it appears as non membranous oval spongy structure formed of dark and light areas. The dark area consists of: Pars granulosa: mature rRNA. Pars fibrosa: newly formed rRNA. Pars amorpha (nuclear organizer): DNA filaments. The light area formed of nucleolar sap. 10/16/2021 Dr. Hariom Yadav  Cell renewal The majority of the mature specialized cells are not in the active cycle (mitosis-interphase-mitosis). They perform their specific function in prolonged GI phase. Types of cells according to renewal ability:- Renewable cell:- Some cells are continuously in mitosis with very short GI-phase as stem cells in bone marrow. Potentially renewable cells:- Some specialized cells that go to GO phase (outside the cycle) can return back to continue the cycle under certain conditions as liver cells when exposed to severe degenerative effect the normal cell can divide to restore the normal size. Non-renewable cells:- Contain cells as nerve cell and cardiac myocyte leave the cycle and persist in GO phase and can not return to the cycle. Cell death The cell life and activity is terminated by either apoptosis or necrosis Apoptosis:- - Also called programmed cell death or physiological cell death which occurs at the end of life span of each cell under the effect of a specific gene on DNA of the cell. - In this type of cell death, the apoptotic cell do not swell but decrease in size together with condensation of the nuclear chromatin which later on dissolute with the cytoplasm forming apoptotic bodies → phagocytosed. Necrosis:- - It is a pathological condition results from toxins, mechanical injury or anoxia. - The necrotic cell swelled, vacuolated then brust and degenerated → phagocytosed.  Modifications in cell constituents to perform specific function 1- Steroid hormone-secreting endocrine cells: They are characterized by: Abundant smooth endoplasmic reticulum, Mitochondria with tubular cristae. Many lipid droplets, this is where cholesterol is stored. Large Golgi apparatus. Large vesicular nucleus. e.g., adrenal cortical cells, Leydig cells of testis and leutin cells of the ovary Dr. 2) Protein-secreting cells: - Abundant rough endoplasmic reticulum. - Many mitochondria. - Large vesicular nucleus. - Well-developed Golgi apparatus. - Numerous zymogen granules. e.g. pancreas. 3) Glycoprotein-secreting cells: - Abundant rough endoplasmic reticulum. - Well-developed Golgi apparatus(addCHO). -Numerous apical mucigen granules (glycoprotein). - Oval basal nucleus. e.g. trachea and intestine (goblet cells). 4) Ion-transport cells: 4) Ion-transport cells: Basal infolding (multiple and deep invaginations) of the cell membrane without infolding of the basal lamina. Abundant elongated mitochondria filling the basal infolding the cell membrane.. Tight junctions seal the apical portion of the cells. Numerous microvilli. e.g., kidney (proximal&distal convoluted tubules) and striated duct of salivary gland..