Epithelial Tissues (Functions of epithelial cells (Immune survelliance…
Functions of epithelial cells
Controlls movement acorss the epithleum. Tight junction modules flow. Protects underlyng organs e.g. epidermis
exocrine glands - secrete into the extracellular space. small ducts = simple cubodial and large ducts= stratifed cuboidal or columnar
Merocrine: release by exocytosis, Apocrine: release portion of the apical membrane, holocrine: cell disintegrates and remnants are excreated
absorb nutrients, ions, and water from lumen and deliver to the underlying vasculature
Epithelial monolayers transport substances along the apical surface. e.g. ciliated cells in the trachae and bronchi; mucocilliary escalator.
Immune survelliance and response
Important to epithelia facing the external environment. Secrete defensins, promote cytokin release and stimulate bacterial apoptosis.
Lymphocytes, neutrophils, and other defensive cells lie underneath epithelia layers
Peyer'a Patches = large aggregates of lymphoid tissue in the illeum
Histology of Epithelial Tissues
Cover Body Cavities, Line cavities of the CV, digestive, genitourinary, and respirtaory systems, line peritoneum, Form secretory glands and some endocrine glands
Mucosal Membranes: Location - respiratory, digestive, and urogenital tracts. Secrete mucous Structure: Epithelium, Lamina Propria, and Muscularis Mucoasae
Cell Type: Squamous, cubodial, columnar Layers: simple, stratified, pseudostratifed
Tissue type and function
Location: inner surface of blood vessels, body cavitiies, air sacs, loop of Henley, parietal layer of glomerulus.
Function: solute diffusion and filtration
Location: kidney tubules, glandular ducts, germinal epithlisum, ovaries, thyroid follicles, salivary glands
Function: secretion and absoprtion
Location: non cililiated - digestive tract, gallbladder, excretory ducts, ciliiated: brochi, fallopian tubes, regions of uterus, spinal cord.
Function: absorption, mucus secretion, enzymes cilliated --> propel mucus, spinal fluid, or reproductive cells
Location: endometrium of uterus, trachae/upper respiratory tract. Epididymis/vas deferens (stereocilia tpe)
Function: absorption, secretion, propulsion of mucus
Location: Nonkertatinized: mucous membrane in esophagus, mouth, cervix, vagina, foreskin, cornea
keratinized: Epidermis of the skin
Function: Protects underlying tissues in areas subject to abrasion
Location: large ducts of sweat glands, mammary glands, salivary galnds. Very rate
Function: barrier and secretion
Location: Small amounts in male urethra and in large ducts of some glands. Rare in the body.
Function: Barrier and secretion
Urothelium (transitional epithelium)
Lines the renal pelvis, ureters, urinary bladder, ad upper third of the urethra
Function: Adats to urine volume by changes in cell and tissue architectiure
Fine structure of polarized epithelial cells
Location: Intestinal Tract
Function: Regulates tissue hydration, prevents edema, lubrication, restricts molecule movement, traps pathogens
Location: GI tract, cornea, fallopian tube, and bladder
Function: cushion and protect the apical surface from abrasion and mechancical damage.
Location: Enterocytes, Proximal tubule cells, brush cells in nasopharynx and urethra,
Function: Absorption, mechanotransduction, sensory perception
Location:Primarily found on pseudostratified columnar epithelum, Hair cells in cochlea, epidydimis and vas deferens
Function: reabsorps seminal fluid, sound perception
Location: trachea, oviduct
Function: transport fluid or fim of mucus
Hemidesmosomes: protect epithelial cells against abrasive and shearing forces and particularly abundant in the stratum basale of the epidermis.
avascular; nutrients and gas exchange occurs from diffusion of substances from underlying capillary bed
Junctional complex aka terminal bar
Seal off external environment from the rest of the body