Histology Lecture 7 (Epithelium I) 2024 PDF

Faculty of Medicine Histology & Cell Biology Epithelium I By Dr. Amany Abd El Fattah Mohamed Lecturer of Medical Histology & Cell Biology  Learning outcomes ❑ At the end of the lecture, the students should be able t...

Faculty of Medicine Histology & Cell Biology Epithelium I By Dr. Amany Abd El Fattah Mohamed Lecturer of Medical Histology & Cell Biology  Learning outcomes ❑ At the end of the lecture, the students should be able to: Enumerate 4 basic body tissues. Recognize the general characteristics of epithelial tissue. Classify epithelium according to its function. Identify the different types of surface epithelium according to morphological criteria. Describe different types of simple epithelium. Describe different types of stratified epithelium. Q1: What is meant by “tissue”? Q2: Of which tissue is formed?  Learning outcome 1 Enumerate 4 basic body tissue  Connective tissue Muscle Nervous Epithelium tissue Human body  Learning outcome 2 Recognize the general characteristics of epithelial tissue.  Avascular tissue. Formed of closely- aggregated cells. Rest on basement membrane Covers the body from outside & line its cavities from inside →always have a free surface It also forms glands & receptors for special senses.  Learning outcome 3 Classify epithelium according to its function.  Classifications: ❑ According to the function: I. Surface II. Glandular III. Neuroepithelium  Learning outcome 4 Identify the different types of surface epithelium according to morphological criteria.  Simple Classifications Num. of (Single layer) layers Stratified (Multiple layers) Surface epithelium Squamous (flat cell) Shape of Cubical cells (cubical cell) Columnar (tall cell)  Squamous Simple Cubical Stratified columnar  Learning outcome 5 Describe different types of simple epithelium.  Simple epithelium Simple Simple Simple Pseudo- squamous cubical columnar stratified columnar  Simple Squamous Epithelium Single layer of flat cells with flat nuclei e.g. lung alveoli. blood vessels (endothelium).  Simple Cubical Epithelium Single layer of cubical cells with central rounded nuclei. e.g. Kidney tubules. Thyroid follicles.  Simple Columnar Epithelium Single layer of tall columnar cells with oval basal nuclei. e.g. large duct of glands. It may be modified to:  1- Simple Columnar Secretory Epithelium Single layer of tall cells with oval basal nucleus and foamy cytoplasm. Secrete mucin. e.g. stomach lining  2- Simple Columnar Absorptive Epithelium with goblet cells. Single layer of tall cells with oval basal nucleus and brush border (have microvilli → increase surface area). Absorb nutrients. e.g. lining of intestine.  3- Simple Columnar Ciliated Epithelium Single layer of tall cells with oval basal nucleus and have projecting cilia. e.g. uterus, fallopian tube  Pseudo-stratified Columnar Epithelium Single layer of cells of differing heights. All cells are attached to the basement membrane. Nuclei lie at different levels (false appearance as stratified) Types: Non ciliated e.g. large ducts of glands. Ciliated with goblet cells e.g. respiratory tract → Respiratory epithelium.  Cilia Goblet cell Pseudostratified columnar non ciliated versus ciliated with goblet cells  Learning outcome 6 Describe different types of stratified epithelium.  Stratified epithelium. Stratified Stratified cubical Stratified squamous (Transitional) columnar  Stratified squamous epithelium Multiple layers of cells (5-30 layer). Basal layer: single layer of columnar cells Middle layers: many layers of polygonal cells Top layer: flat cells. Types: Keratinized (have keratin layer on its surface) e.g. skin. 1. Non-keratinized e.g. mouth cavity, esophagus, vagina.  Keratin ? ? Stratified squamous Non keratinized Versus Keratinized  Transitional Epithelium Multiple layers of cells (6-8). Basal layer: single layer of low columnar cells Middle layers: layers of polygonal cells Top layer: large cubical cells (dome-shaped) →umbrella cells e.g. urinary tract (ureter, urinary bladder) → Urinary epithelium (Urothelium).  Stratified Columnar Epithelium Multiple layers of cells (20 layer). Basal layer: single layer of low columnar cells Middle layers: many layers of polygonal cells Top layer: columnar cells. e.g.: conjunctiva of the eye.  Summary and wrap up Body is formed of 4 basic tissues, epithelium, connective tissue, muscle & nervous tissue. Epithelium is avascular tissue formed of aggregated cells. It is divided into surface, glandular & neuroepithelium. Surface epithelium is divided into simple and stratified types according to number of layers, Simple & stratified are further subdivided according to shape of cells.  References https://www.youtube.com/watch?v=P3714_a3l0w https://www.youtube.com/watch?v=Bi4K_IIJl3w