Unit 1 Organization of Animal Bodies Topic Epithelial

Unit 1: Organization of Animal Bodies Topic: Epithelial Tissues Types and Functions B. Ed (Hons) Secondary Semester IV Subject: Advance Biology II Course Title: Animal Form and Function–I Represented By: Ms Sidra Younis Department of Education(Planning and Development) Lahore College for Women University, Lahore

EPITHELIAL TISSUES � � � Epithelial tissues covers the outside of body and lines organs and cavities. The cells in this tissue are very closely packed together. This tissue has many types on the basis of the shape of cells as well as the number of cell layers.

CELL TO CELL JUNCTIONS � � Cells of epithelia are closely connected and are not separated by intracellular material. Three basic types of connections Tight Junctions Anchoring Junctions Gap Junctions

TIGHT JUNCTIONS � � The cells making up epithelia are often closely bound to one another through specialized structures called tight junctions. They are also free from blood vessels and nerves and are supported by a connective tissues called basement membrane.

ANCHORING JUNCTIONS � � � Anchoring junctions are common on the lateral and basal surfaces of cells where they provide strong and flexible connections. In contrast with the tight and anchoring junctions. GAP JUNCTIONS A gap junction forms an intercellular passageway between the membranes of adjacent cells to facilitate the movement of small molecules and ions between the cytoplasm of adjacent cells.

TYPES OF EPITHELIAL TISSUES 1: Squamous Epithelial 3: Cuboidal Epithelial 2: Columnar Epithelial 4: Ciliated Columnar Epithelial 5: Stratified Squamous Epithelial 6: Glandular Epithelial

1: SQUAMOUS EPITHELIUM � � � Consists of a single layer of flat cells. It is found in lungs, heart and blood vessels. It allows the movement of materials across it.

2: COLUMNAR EPITHELIUM � � � Has elongated cells. It is found in alimentary canal, gall bladder etc. It makes secretions.

3: CUBOIDAL EPITHELIUM � � � Consists of a single layer of cube-shaped cells. It is found in kidney tubes, small glands etc. It makes secretions.

4: CILIATED COLUMNAR EPITHELIUM � � � Epithelium has elongated cells with cilia. It is present in trachea and bronchi It propels mucous.

5: STRATIFIED SQUAMOUS EPITHELIUM � � � It has many layers of flat cells. It is present in the lining of oesophagus and mouth and also over the skin. It protects the inner parts of body.

6: GLANDULAR EPITHELIUM � � � Glandular epithelium is a type of epithelial tissue which covers the glands (both exocrine and endocrine) of our body. Their main function is secretion. Both endocrine and exocrine glands produce their secretions through the glandular epithelium via special cells called goblet cells

GLANDS CLASSIFICATION ENDOCRINE GLANDS � � A ductless gland that releases secretions directly into surrounding tissues and fluids (endo= “inside”) For examples: Pineal gland, pituitary gland, thyroid gland etc. EXOCRINE GLANDS � � An exocrine gland whose secretions leave through a duct that opens directly, or indirectly, to the external environment (exo- = “outside”). For examples: Salivary glands, Sweat glands etc.

EPITHELIAL TISSUES FUNCTIONS � � � Covering and lining the outer layer of skin. To protect the tissues that lie beneath from radiation, desiccation, toxins, invasion by pathogens, and physical trauma. Inside the body epithelial cells form the lining of the mouth and alimentary canal and protect these organs. Absorb water and digested food in the lining of digestive canal. To provide sensation.

CONT… � � � Help in the elimination of waste. The regulation and exchange of chemicals between the underlying tissues and a body cavity. Play an important function in the secretion of hormones into the circulatory system, as well as the secretion of sweat, mucus, enzymes, and other products that are delivered by ducts.