Glands - CH4 PDF

Glands 4.1 Four Types of Tissue (2 of 3) Epithelial tissue –Covers exposed surfaces –Lines internal passageways –Forms glands Epithelial tissue includes epithelia and glands –Epithelia (singular, epithelium) ▪Layers of cells covering internal or external surfaces –Glands ▪Structures that produc...

Glands 4.1 Four Types of Tissue (2 of 3) Epithelial tissue –Covers exposed surfaces –Lines internal passageways –Forms glands Epithelial tissue includes epithelia and glands –Epithelia (singular, epithelium) ▪Layers of cells covering internal or external surfaces –Glands ▪Structures that produce fluid secretions 4.3 Classification of Epithelia Cuboidal epithelia –Simple cuboidal epithelia ▪Secretion and absorption ▪Glands and portions of kidney tubules –Stratified cuboidal epithelia ▪Relatively rare ▪Ducts of sweat glands and mammary glands Glandular epithelia- a type of tissue that produces and releases substances in the body –Glands are collections of epithelial cells that produce secretions –Endocrine glands- through the bloodstream ▪Release hormones that enter bloodstream ▪No ducts –Exocrine glands- on the skin ▪Produce exocrine secretions ▪Discharge secretions through ducts onto epithelial surfaces Gland structure –Unicellular glands –Multicellular glands Unicellular glands –Goblet cells are unicellular exocrine glands –Endocrine glands ▪In epithelia of intestines ▪Secrete mucin, which mixes with water to form mucus Multicellular exocrine glands are classified by Examples of multicellular exocrine glands include: Sweat glands: Also known as sudoriferous glands Oil glands: Also known as sebaceous glands Salivary glands: Contain serous cells that secrete a protein-rich fluid, and mucous cells that secrete mucins Multicellular glands are tubular Simple glands: Have a single, continuous duct Compound glands: Have branched ducts Tubular glands: Have tubular secretory units with straight or coiled tubes  Merocrine secretion –Released by secretory vesicles (exocytosis) –Example: merocrine sweat glands Apocrine secretion –Released by shedding cytoplasm –Example: mammary glands Holocrine secretion –Released by cells bursting, killing gland cells –Gland cells replaced by stem cells –Example: sebaceous glands Types of secretions produced by exocrine glands –Serous glands ▪Watery secretions –Mucous glands ▪Secrete mucins –Mixed exocrine glands ▪Both serous and mucous