8/21/17 Flashcards
Epithelium basics
Covers exterior body surfaces
Lines body cavities and tubes, stained by cytokeratin
Regulate contact between the external environment and underlying tissues
Functions: protection, transportation, glandular secretion, sensation
Epithelium polarity
Apical: faces lumen or outside world
Lateral: cells are close to each other via special attachments
Basal domain: sits atop a basement membrane
Simple squamous epithelium
Selectively permeable barrier, permits rapid diffusion
Alveoli of lungs, Bowman’s capsule, endothelium of blood vessels, mesothelioma of body cavities
Polygonal shape from birds eye view
Simple cuboidal epithelium
Mainly absorption and secretion
Protection, a barrier, less capable of diffusion
Small ducts of exocrine glands (like pancreas), kidney tubules, thyroid follicles
Simple columnar epithelium
Absorption and secretion
Stomach, small intestines and colon, gallbladder
Nuclei at the same level
Pseudostratified epithelium
Absorption, secretion, transport
Bronchial tree (ciliated pseudostratified epithelium) Vas deferens and epididymis
Stratified squamous epithelium
Protection from physical and chemical damage
Epidermis, oral cavity and esophagus, vagina
Kerstinized or non-keratinized, cancer has abnormal keratin called keratin pearls
Stratified cuboidal epithelium
Protection and conduit
Large ducts of exocrine glands (salivary, mammary, sweat)
Anorectal junction
Stratified columnar epithelium
Protection and conduit
Largest exocrine ducts (large salivary duct)
Anorectal junction
Transitional epithelium (urothelium)
Distensible, protection
Lower urinary tract
Dome shape on top
Exocrine vs. Endocrine gland
Exocrine:
Secrete into ducts, which can modify the secretions
Secretions released on the apical surface
Endocrine:
Secrete through bloodstream, no ducts
Secrete through basal surface into connective tissue on path to blood
Methods of exocrine secretion
Merocrine: most common, do exocytosis to release product once fuse with plasma membrane (Endocrine glands do this)
Apocrine: budding of the product from the plasma membrane
Holocrine: programmed cell death that releases secretions and cell debris
Goblet cells
Unicellular exocrine glands
GI and respiratory tracts
Produce mucin, a component of protective mucus
Important types of simple and compound multicellular exocrine glands
Simple coiled tubular: eccrine sweat glands of the skin
Simple tubular glands: large intestine, goblet cells
Compound acrinar: exocrine portion of the pancreas, secrete enzymes for digestion and absorption of nutrients, serous-secreting cells, defects lead to pancreatic insufficiency that cause malabsorption and diarrhea
Serous-secreting vs. mucus-secreting exocrine glands
Serous secretions: thin and watery, proteins and enzymes, not glycosylated
Mucous secretions: viscous and slimy, glycosylation of proteins make appear empty from H&E stains
