L3 Epithelium Histology BMS 122 Lecture Notes PDF

Textbook guide General Histology for Faculty of Dental Students BMS 122 Junqueira's Basic Histology, Text F A L L 2 0 2 4 and Atlas. Mescher, 15th...

Textbook guide General Histology for Faculty of Dental Students BMS 122 Junqueira's Basic Histology, Text F A L L 2 0 2 4 and Atlas. Mescher, 15th Edition, 2018 T H E F U T U R E S T A R T S H E R E  INTENDED LEARNING OBJECTIVES (Ilos) By the end of this Lecture, you will be able to identify  The four basic tissues of the body.  General characters of epithelial tissue.  Types of epithelium.  Histological classification, structure and functions of covering epithelia.  ORGANIZATION OF THE HUMAN BODY Cell Tissue Organ System Faculty of Pharmacy  There are four basic tissues which include: 1) Epithelium 2) Connective tissue 3) Muscular tissue 4) Nervous tissue All of them are composed of:  Cells &  Extracellular matrix in different proportions  General characters of the epithelial tissue: 1- Epithelium covers surfaces, (covering epithelium) or lines cavities. 2- Epithelial tissue is composed mainly of cells with little intercellular substances. 3-The cells lie on a basement membrane which separates the epithelium from the underlying connective tissues. 4- Blood vessels or lymphatic cannot penetrate the tissue (avascular), but nerves can. 5- Nourishment of epithelial tissue occurs by diffusion of nutrients and oxygen from the blood vessels present in the underlying connective tissue.  Enumerate types of epithelial tissues 1. Covering & Lining 2. Glandular 3. Specific epithelium Epithelium Epithelium Simple epith. Exocrine Myoepithelial One layer glands cells Specialized sensory Stratified epith. Endocrine epith. glands ˃ One layer Neuroepithelium  Classification of covering epithelium According to the number of layers Simple Stratified epithelia epithelium One layer Two or more layers  Simple epithelium Types of simple epithelium: It can be classified according to the shape of the cell: 1. Simple squamous. 2. Simple cubical, cuboidal. 3. Simple columnar. 4. Pseudo stratified.  1. Simple squamous epithelium Formed of one layer of flat cells with flattened nuclei.  Function: thin & smooth surfaces  Sites:  The endothelium lining of blood vessels.  Alveoli of the lung. Alveoli  2. Simple cuboidal epithelium Formed of one layer of cubical-cells with central rounded nuclei.  Function: Secretion & Reabsorbsion  Sites:  Thyroid follicles.  Lining the convoluted tubules of the kidney. Thyroid follicles Kidney tubules  3. Simple columnar epithelium  Formed of one layer of tall columnar cells with basal oval nuclei.  The cells may be:  Simple columnar ciliated epithelium: lining uterus and fallopian tubes to move ova. Simple columnar non-ciliated epithelium: lining stomach & intestine for secretion & absorption. Faculty of Pharmacy  4. Pseudostratified columnar epithelium  It is simple type of epithelium formed of one layer of tall columnar cells & short cells. All the cells are rest on the basal lamina but some of them do not reach the surface.  The nuclei appear to lie at different levels.  Result in a false appearance of stratified epithelium.  Pseudostratified columnar ciliated with goblet cells (Respiratory epithelium): Trachea  Pseudostratified columnar non ciliated (Large ducts of the glands)  Goblet Cells Goblet cells are modified simple columnar cells which secrete mucus, present in the small, large intestines and respiratory tract. Goblet cells have a cub-like expanded apical part full of mucus and a basal cylindrical part containing a flat nucleus. They appear as vacuoles or pale areas in the epithelial membrane, as their mucus content dissolves during preparation. Goblet cells (arrows) in intestinal crypt  Stratified epithelium Types of stratified epithelium: - It can be classified according to the shape of the superficial cell layer: 1. Squamous. 2. Cuboidal. 3. Columnar. 4. Transitional  1. Stratified Squamous epithelium  Several cell layers  Basal layers: cuboidal to columnar  Intermediate layer: polyhedral  Surface layers: flattened (squamous) Function: Protection a. Stratified squamous keratinized b. Stratified squamous (dead superficial cells) non- keratinized Dry surfaces Wet surfaces Keratin layer Site: Site: Epidermis of the skin Esophagus, Mouth , Vagina  2. Transitional epithelium - Sites: In the urinary system (urinary bladder & ureter) - In empty state of the urinary bladder: The transitional epithelium lining the urinary bladder is formed of 6-8 1ayers of cells; Basal columnar cells resting on a thin basement membrane, middle layer of 3-5 polyhedral cells and superficial dome shaped cells, sometimes binuclear - In full state of the urinary bladder: the cells in the middle layer glide on each other and become arranged in about 2-3 layers and the superficial cells become flattened Covering epithelium  Glandular epithelium Classification of exocrine glands Exocrine glands are further classified according to: 1- Number of cells: Unicellular (goblet cells) Multicellular 2- Type of secretion: Mucous Serous Mixed 3- Mode of secretion: Merocrine (salivary glands) Apocrine (mammary glands) Holocrine (sebaceous glands)  Assignment 1 1- Compare in a table between: A- Cell organelles & cell inclusions B- RER & SER 2- Enumerate types of simple & stratified epithelium & mention one site for each one