Histology Lecture (7) Epithelium (1) PDF

Histology lecture (7) Epithelium (1) Histology It is one of the four main types of tissue structures of the human body. It covers:  Outer surfaces body surface.  Inner surfaces of cavities. It forms most of the glands. S...

Histology lecture (7) Epithelium (1) Histology It is one of the four main types of tissue structures of the human body. It covers:  Outer surfaces body surface.  Inner surfaces of cavities. It forms most of the glands. Surface coverage Link or support other specialized tissues Contractile property Cells forming brain, spinal cord, and nerves 1. Covers the body surface, cavities & form most of the glands. 2. Cellularity cohesiveness: cells are in close contact with intercellular junction between them. 3. Polarity: epithelial tissues always have an apical and basal surface 4. The epithelial cells rest on basement membrane (BM) 5. The basal surface adheres to the basement membrane. 6. Cell appendices: Cell surface may have microvilli or cilia 7. Epithelial tissue is avascular: nutrients transported by diffusion from the underlying blood vessels in the C.T 8. Epithelial tissue is highly innervated. 9. Regeneration: epithelial tissues have a high capacity to continuous renewal. 1. Protection 4. Filtration barrier 2. Secretion 5. Ion or gases transport 3. Absorption. 6. Forms slippery surfaces  Histology 1. Covering and lining epithelium on external and internal surfaces 2. Glandular epithelium secretory tissue in glands 3. Neuroepithelium  Formed of single layer of cells & rest on  Formed of many layers of cells (5 - 30), the basement membrane (BM) first layer of cells rests on the BM.  Subclassified according to shape of cells  Classified according to shape of superficial into: cell layers into : 1. Simple squamous epithelium. 1. Stratified squamous epithelium. 2. Simple cubical epithelium. 2. Stratified cubical (Transitional) 3. Simple columnar epithelium. epithelium. 4. Pseudostratified columnar epithelium. 3. Stratified columnar epithelium. Histology A Monolayer of flat & thin shaped cells Monolayer of square shaped cells Central & flat nuclei Central & rounded nuclei 1. Endothelium on inner surface of 1. Renal tubules heart, blood vessels & lymph vessels. 2. Thyroid follicles 2. Mesothelium lining serous 3. Small ducts of exocrine glands e.g., membranes around the organs salivary glands (pericardium, pleura & peritoneum). 3. Alveoli of the Lung  This type of epithelium is formed of a monolayer of crowded cells.  All the cells rest on the BM, but some cells Monolayer of columnar tall cells became short & fail to reach the surface and tall ones with oval nuclei can reach the free surface. Oval nuclei arranged in different levels which Basal oval nuclei give a false appearance of stratified epithelium Histology 1. Simple columnar Secretory 1. Pseudostratified columnar non-ciliated epithelium e.g. Stomach epithelium e.g.: large ducts of the salivary glands. 2. Simple columnar Absorptive 2. Pseudostratified columnar epithelium with epithelium e.g. Small Intestine motile cilia & goblet cells e.g.: nasal cavity, (has numerous microvilli) nasal air sinuses, trachea, bronchi 3. Simple columnar ciliated 3. Pseudostratified columnar epith. with non- epithelium e.g. Bronchioles, motile cilia. e.g.: epididymis. fallopian tube & uterus. Histology b  It is composed of multiple cell layers. columnar cells  The same structure like Stratified basal & oval nuclei. squamous non-keratinized epithelium with super added polyhedral cells formed of flat dried horny central & rounded scaly cells filled with keratin. squamous (Flat) cells central & flat  It covers the wet mucosa which open  It form the dry surface of the skin into the skin 1. Cornea & conjunctiva  Epidermis of Skin 2. Oral cavity 3. Esophagus 4. Anal canal 5. Urethra. 6. Vagina. Histology  It is a type of stratified epithelium called transitional because the shape of the surface cells changes (undergoes transitions) depending on the degree of stretch & increased pressure inside the urinary bladder.  The cells rest on a thin basement membrane which can contract and expand in order to adapt to the degree of distension needed. formed of (5 - 8 layers):- Multilayers of Large cubical cells with polyhedral cells with Columnar cells convex upper surface mucous substance (dome shape). between the cells Central rounded nuclei Basal oval. Central rounded Some are binucleated. The number of cell layers changed to 2 or 3 layers in full bladder. All cell layers (undergo transitions) depending on the degree of stretch & fullness of the urinary bladder. The presence of mucous substance between the cells facilitates sliding of the cells on each other in full bladder. Superficial cell layer: is stretched & flattened temporarily. 1. Pelvis of Kidney. 2. Ureter 3. Urinary Bladder (U.B.). 4. Prostatic Urethra Histology  It is composed of multiple cell layers. Columnar cells Polyhedral cells Columnar cells Basal oval. Central rounded Basal oval. 1. Large ducts of salivary glands 2. Recto-Anal junction 3. Male Urethra (Membranous Part) Histology Glandular epithelia are formed by cells specialized to secrete. The molecules to be secreted are generally stored in the cells in small membrane-bound vesicles called secretory granules.  Have ducts  Ductless G.  Posses the two types  Secreting hormones pass directly to the blood  Sweat glands.  Pineal G  Liver  Sebaceous Glands  Pituitary G  Pancreas  Salivary glands.  Thyroid G.  Testes.  Suprarenal G.  Formed of a single cell  Formed of numerous cells  Goblet cells.  Salivary glands & pancreas Histology  have tubular secretory part  have grape like or acinar  possess both tubular & secretory part alveolar shaped glands  Kidney, liver, Testes &  Sebaceous glands.  Salivary glands. intestinal glands.  Mammary glands.  pancreas  Prostate gland. Viscid mucous poor in enzymes Goblet cells & minor salivary glands. Watery solution rich in enzymes Parotid glands and pancreas. Both types of secretions Submandibular& sublingual glands. Watery secretion containing some enzymes & waste products. Fatty secretion Sebaceous & meibomian gland Waxy secretion Ceruminous glands of external canal. Produce cells Testis & ovary Histology  Sweat glands  The cells Secrete via Exocytosis  Salivary glands.  The cells secrete via membrane  Mammary glands. bounded vesicles  During secretion, the cell lysis &  Sebaceous glands release entire contents of the  Meibomian gland. cytoplasm & cell membrane