IAS21 Flashcards
embryonic origin of connective tissues
all from mesoderm (mesenchyme)
general connective tissue function
- material exchange (through blood vessel, deliver nutrients, remove wastes)
- support & binding of other tissues tgt
- protection, e.g. inflammation & immune response against infection
- wound healing
- regulating behaviour of cells: platform for cell attachment -> allow migration, proliferation, differentiation
ECM ground substances
amorphous gelatinous material
dynamic matrix of water
hyaluronic acid, proteoglycan, glycoprotein stabilize water -> form of ground substance from solid to fluid depend on their proportions
ground substance function
- bind to EC components to stabilize ECM
- can anchor cell to ECM by binding to integrins of cell surface receptors
- control cell migration
- provide route for comm. & transport of ions & molecules btn tissues
- determine tissue functionality
hyaluronic acid
linear, non-sulphated GAG
viscous, slippery, good lubricant -> reduce friction e.g. joint
proteoglycan
core protein attached to GAG, varying sidechain
can attach to HA to form larger structure of proteoglycan aggregate -> -vely charged, attracts cations -> osmotically active -> traps water
glycoprotein
adhesion proteins
links components of ground substance to surface of cell
e.g. fibronectin (common), laminin (basal lamina), osteopontin (bone ECM)
collagen
provide flexibility & high tensile strength
secreted in ECM to form stable polymers
oriented in diff. directions
wavy fibers, variable width
type I most abundant type, synthesized by fibroblasts & osteoblasts
collagen in wound healing
fibroblasts produce type III first -> forms a mesh near injured site & scaffolds for tissue injury
type III replaced by stronger type I during recovery
reticular fibres & staining
fine fibrils in short & branched network, type III collagen, arranged in meshwork, does not bundle extensively
house cell for better cell-cell interaction & struc support
provide supporting mesh framework for soft organs (not in bundles, e.g. spleen, red bone marrow, liver, lymph node)
invisible to H&E: silver -> black/brown; PAS stain -> pink
elastic fibre
thin, long fibrils of elastin, no bundles, extensively crosslinked
fresh fibres yellow in color, wavy appearance when relaxed
-> allows stretch & recoil, difficult to break apart
in aortic wall, larynx, ligamentum flavum in vertebral column
marfan syndrome
autosomal dominant, defect in gene for protein fibrillin-1
less microfibrils to make elastic fibrils -> less elastic, more proteoglycans w/ fibrils loosely arranged -> stretch & recoil ability of aorta lost
-> long limbs & fingers, tall, heart complications
cellular components of connective tissue
resident cells: low motility
transient cells: mobile, temporary
fibroblast
most common cell type
spindle shaped, branching cell w/ deeply basophilic cytoplasm, prominent nucleolusm, large euchromatic nucleus
fibrocytes (less active form) sickle shape
a lot of rER w/ cisternae distended (active synthesis)
function: synthesize collagen, elastic & reticular fibres, ground substance of ECM
tissue repair
adipocyte types, structure & distribution
WAT (white): monoocular, larger (enlarge through expansion of lipid droplet), more abundant, nucleus & organelles squeezed into periphery
in subcutaneous & visceral fat pads
BAT (brown): multiocular, smaller, more mitochondria
abundant in babies; in kidney & spine