Epithelial Tissue 2 types Membranous Glandular Membranous Covers

Epithelial Tissue 2 types Membranous & Glandular

Membranous § § § Covers body and lines serous cavities Lines blood & lymphatic vessels Lines respiratory, digestive & genitourinary tracts Glandular § This tissue is grouped in a solid cord that forms secretory units of endocrine and exocrine glands.

Functions of Epithelial 1. 2. 3. 4. 5. Protection – most important (skin) Sensory functions –found in nose, eyes and ears Secretion- most important glandular function…. hormones, mucus, digestive juice and sweat Absorption- lines lungs and sm. Intestine Excretion- lines kidney and allows removal of urine from kidneys.

n n Epithelial tissue has generally little or no matrix. Epth. Tissue connects to underlying connective tissue by a permeable noncellular adhesive – basement membrane Both connective and epth. tissue secrete a basement membrane made of glycoproteins.

What makes the basement membrane? Epithelial tissue – basal lamina (makes membrane) n Connective tissue – reticular lamina (makes membrane) **Epth. Tissue has no blood vessels – avascular ** This tissue is held together depending on where the tissue is in the body by 3 types of cell junctions. n

3 types of cell connections (junctions) 1. 2. 3. Desmosomes Gap Junctions Tight Junctions

1. v v 2. v v v Desmosomes Very strong, resist stretching Like small “spot welds” they resemble Velcro Hold cells together or to underlying basal lamina Found in superficial layers of the skin Gap Junction Form gaps or tunnels bt. Two adjoining cells This tunnel allows cytoplasmic materials to pass bt. both cells This coordinates movements such as cilia in trachea

3. Tight Junctions v Join cells by “collars” (similar to six pack) v Molecules can not pass through this connection v Found in the lining of intestines.

Classification by Shape and Layers Four cell shapes 1. Squamous – flat and plate like 2. Cuboidal – cube-shaped 3. Columnar – rectangle shaped

4. Pseudostratified Columnar – one layer of oddly shaped cells that all must touch the basement membrane.

Classify by Layers Simple – single layer 2. Stratifiedlayered on top of each other (same cell type) 3. Transitional – 1. different cell shapes in a layered arrangement.