Dentistry Epithelium PDF

Dr. Shehab Hafez General Histology For Level (1) Dentistry Epithelium Prof. Dr. Shehab Hafez Professor of Histology & Cell Biology Mansoura University  Dr. Shehab Hafez Basic b...

Dr. Shehab Hafez General Histology For Level (1) Dentistry Epithelium Prof. Dr. Shehab Hafez Professor of Histology & Cell Biology Mansoura University  Dr. Shehab Hafez Basic body tissues 1. Epithelium 2. Connective tissue 3. Muscular tissue 4. Nervous tissue  Dr. Shehab Hafez Epithelium  Dr. Shehab Hafez General characters of epithelial tissue 1. Closely aggregated cells with strong adhesions. 2. Little intercellular substance. 3. The cells rest on a basement membrane. 4. Avascular tissue: No blood vessels enter between the cells. Nutrition and blood supply: from the underlying connective tissue. 5. Contain nerves. 6. Epithelium is subjected to continuous degeneration and regeneration.  Dr. Shehab Hafez Epithelium (1) (2) (3) Surface (Covering) Glandular Neuro-epithelium epithelium epithelium  Dr. Shehab Hafez Classification of surface (covering) epithelium Sheets of cells that: Cover body surfaces. Line body cavities. Classified according to the number of layers into: A. Simple epithelium Single cell layer. All cells reach the basement membrane. B. Stratified epithelium More than one layer of cells. Only one layer reaches the basement membrane.  Dr. Shehab Hafez A. Simple epithelium Classified according to the shape of cells into: 1. Simple squamous epithelium 2. Simple cuboidal epithelium 3. Simple columnar epithelium 4. Pseudostratified columnar epithelium  Dr. Shehab Hafez 1. Simple squamous epithelium ▪ Thin flat cells with bulging nuclei. Sites Lining of blood vessels eg aorta. Lung alveoli.  Dr. Shehab Hafez 2. Simple cuboidal epithelium ▪ Cubical-shaped cells with central and round nuclei. Sites Thyroid follicles. Renal tubules.  Dr. Shehab Hafez 3. Simple columnar epithelium ▪ Column-like cells with basal and oval nuclei. Types 1. Simple Columnar Secretory: in the stomach  Dr. Shehab Hafez 2. Simple columnar Absorptive: in the small intestine. 3. Simple columnar Ciliated: in the fallopian tube.  Dr. Shehab Hafez 4. Pseudo-stratified columnar epithelium ▪ Overcrowded Columnar cells, all cells reach the basement membrane. ▪ Nuclei are at various levels (giving a false impression of being stratified). Types 1. Ciliated: trachea and bronchi. 2. Non-ciliated: large ducts of glands. Pseudo-stratified columnar ciliated epithelium  Dr. Shehab Hafez B. Stratified epithelium 1. Stratified squamous epithelium 2. Transitional epithelium  Dr. Shehab Hafez Non-keratinized Stratified squamous epithelium Sites ▪ Mouth cavity. ▪ Esophagus.  Dr. Shehab Hafez keratinized Stratified Squamous Epithelium Site: epidermis of Skin  Dr. Shehab Hafez Transitional epithelium (urothelium) ▪ Sites: Found only in the urinary tract (urinary bladder and ureter). ▪ Specialized to accommodate a great degree of stretch and to withstand the toxicity of urine. ▪ Why Transitional? ▪ Its cells can undergo a transition in their appearance in full bladder and empty bladder.  Dr. Shehab Hafez In non-distended (empty) bladder ▪ 4-6 layers of cells. ▪ Very thin basement membrane. ▪ Basal layer is columnar or cuboidal. ▪ Middle layers: polyhedral ▪ Top layer: very large dome-shaped cells: umbrella (U) cells. Transitional epithelium in non-distended bladder  Dr. Shehab Hafez Transitional epithelium in non- distended (empty) bladder In distended (full) bladder ▪ The epithelium is stretched & reduced in thickness. ▪ Appears; 2-3 layers thick.  Dr. Shehab Hafez Glandular Epithelium Classification of glandular epithelium Classified according to: A. According to the duct & secretory part B. According to the nature of secretions  Dr. Shehab Hafez A. Classification according to the duct & secretory part 1. Presence or absence of the duct a) Exocrine gland: salivary glands. b) Endocrine gland: thyroid glands. c) Mixed gland: pancreas and liver. 2. Shape of secretory part a. Tubular glands b. Alveolar (acinar) glands The secretory part is tube-like. The secretory part is flask-shaped  Dr. Shehab Hafez 3. Branching of the duct and secretory part a) Simple glands Single (unbranched) duct. Single (unbranched) secretory part. b) Simple branched glands Single (unbranched) duct. Branched secretory part. c) Compound branched glands Branched duct. Branched secretory part.  Dr. Shehab Hafez B. Classification according to nature of secretion a) Mucous glands produce viscid mucous poor in enzymes e.g. goblet cells. b) Serous glands produce watery solution rich in enzymes e.g. parotid gland. c) Mucoserous glands produce both types of secretions e.g. Submandibular gland. d) Sweat glands: of skin. e) Oily glands: secrete fatty secretion e.g. sebaceous gland.  Dr. Shehab Hafez Neuroepithelium Definition: Special type of epithelium modified to receive external sensations. Sites ▪ Tongue: taste buds. ▪ Inner ear: organ of Corti. ▪ Eye: retina. ▪ Olfactory epithelium. Structure a) Sensory cells: ▪ Tall cells with hairlets on their free borders. ▪ Their bases are surrounded by free sensory nerves. b) Supporting cells. c) Basal cells: precursors for the above types