epithelia and connective tissues Flashcards
function of epithelia
have a free surface. -protect underlying tissues from the outside world
- protects/separates areas within the body.
- help told tissues together
- thermoregulation
- hormone release
- absorption
epithelia
on surface
endothelium
lining blood vessels
mesothelium
lining body cavities
simple
1 layer
squamous
flat
to exchange functions eg alveoli, capillaries
cuboidal
cube
for absorption and secretion eg, renal tubed, secretory glands
columnar
taller than wide large intracellular volume potential for energy reserves and high organelle density. motility, absorption and processing. small intestine
stratified
many layers
pseudostratified
looks stratified but all cells connect to the basement membrane
respiratory tract
transitional
many layers
waterproof and stretchy
bladder, urinary tract
the basement membrane
sheets of matrix at interface of functional tissue [epithelium] and support tissue [connective tissue]. composed mainly of type IV collagen, glycoproteins and glycosaminoglycans
structure of glands and ducts
epithelium folds and glands enable increased secretion. generally the secretory portion is columnar. ducts are cuboidal epithelium.
epidermolysis bullosa
separation of epidermis and dermis- causes blistering
carcinomas
cancers derived from epithelial cells
adenocarcinoma
cancer in the glands
exocrine glands
secrete their products onto the epithelial surface directly/ via a duct for local action eg, sweat glands, liver
endocrine glands
release their secretions directly into the blood to act on different tissues eg, pituitary and thyroid glands
connective tissue
the support tissue of the body. originated from embryonic mesoderm. abundance of matrix with few cells- cells[5%] and extracellular matrix [95%]- ECM
what is the extracellular matrix composed of?
fibres (collagen and elastin), ground substance [glycoproteins ad glycosaminoglycans), cells- the fibroblast secretes ECM for most tissues.
collagen
1) Procollagen- polypeptide chain synthesized on ribosome of rER and secreted into lumen, then modified by hydroxylation of certain proline and lysine residues and glycosylation before chain association and triple helix formation
2) Procollagen molecules secreted into extracellular space where the N and C propeptides are cleaved by specific proteases
3) The collagen molecules assemble into fibrils, stabilized by formation of covalent crosslinks.
elhers danlos syndrome
type 1 collagen disorder- reduced tensile strength- tissue laxity, joint hypermobility and susceptibility to injury
reticulin
type 3 collagen, branched
elastin
provides elasticity. stretching and elastic recoil. Tropoelastin polymerises to elastin. requires fibrillin for assembly
marfans syndrome
genes coding for fibrillin are defective- rupture of the aorta
structural glycoproteins
- fibrillin- microfibrils-links to elastin.
- fibronectin- deposition and orientation of collagen and its links to cells via integrin.
- Laminin- major component of the basement membrane
glycosaminoglycans
polysaccharide chain that attracts water