IAS21 Flashcards
general connective tissue function
SMBII
1. material exchange through blood vessel
2. support & binding of other tissues tgt
3. protection, e.g. inflammation & immune response against infection
4. wound healing
5. regulating behaviour of cells: platform for cell attachment -> allow migration, proliferation, differentiation
ECM clinical connection
may thicken in certain pathological states e.g. autoimmune disease, nephropathy & vasculopathy
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
SAM FR
1. bind to EC components to stabilize ECM
2. can anchor cell to ECM by binding to integrins of cell surface receptors
3. control cell migration
4. provide route for comm. & transport of ions & molecules btn tissues
5. 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 (but generally thick), eosinophilic, tough, non-branching, most abundant protein
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
thin fibrils in short & branched network, collagen III, arranged in meshwork, does not bundle extensively
house cell for better cell-cell interaction & struc support; provide supporting mesh framework for soft organs
found in spleen, red bone marrow, liver, lymph node & other organs where blood & lymph are filled
invisible to H&E: silver -> black/brown; PAS -> pink
elastic fibre
thin, long fibrils of elastin & microfibrils (fibrillin), no bundles, extensively crosslinked (branching)
fresh fibres yellow in color, wavy appearance when relaxed
randomly oriented when unstretched, same dir. when stretched -> allows stretch & recoil, difficult to break apart
in aortic wall, skin dermis, bladder, lung, (larynx, ligamentum flavum in vertebral column)
marfan syndrome
autosomal dominant, defect in gene for protein fibrillin-1 –> less microfibrils to make elastic fibres -> less elastic fibres, 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, e.g. fibroblasts & adipocytes
transient cells: mobile, temporary, e.g. macrophages, mast cells, plasma cells
fibroblast & fibrocyte
most common cell type
spindle shaped w/ deeply basophilic cytoplasm, prominent nucleolus, 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), nucleus & organelles squeezed into periphery
in subcutaneous & visceral fat pads
BAT (brown): multiocular, smaller, more mitochondria
abundant in babies; in kidney & spine
adipocyte functions & mechanisms
WAT: fuel storage, fatty acid DNS, release of FA when other tissues need them, form TAG from FFA from lipoproteins (chylomicrons & VLDL), protection & insulation
BAT: fuel storage, thermoregulation (releases heat to keep infants & organs warm), endocrine regulation
macrophage
phagocytic cells derived from monocyte
engulf pathogens, dead cells & RBC by phagocytosis, contain many lysosomes, innate immunity
macrophages as antigen-presenting cells
antigen broken down –> bind to MHC -> phagocytic vesicle fuses w/ plasma membrane -> antigen presented to T cell
mast cell
large & oval, contains secretory granules; dense
contains IgE antibodies, when allergens or antigens bind to IgE -> exocytosis of granules containing vasoactive & immunoreactive substances e.g. histamine (increase vessel perme), heparin (anti-coagulant) & chemotactic factors (attract lymphocytes)
function: mediate inflammation & allergic Rx
plasma cell
strong basophilia, oval shape
prominent golgi & rER, spherical nucleus in eccentric location, large clumps of peripheral heterochromatin alternating w/ euchromatin -> clock face
function: specific antibody prod.
connective tissue proper & types
fibrous component predominant
loose (areolar): more cells than fibres
dense: more fibres than cells, regular vs irreg
loose connective tissue
more cells than fibers
fine fiber network filled w/ ground substance
mostly transient cells migrating from local vessels in response to specific stimulus -> site of inflammatory & immune responses
support & binding, material exchange, body defense
(SMB)
e.g. lamina propria under epithelia, mesentery
dense irregular connective tissue
large amt of (type I) collagen fibres organised into thick bundles in random dir., matrix relatively acellular
provide elasticity & tensile strength, support organ
e.g. capsule of joints & organs, skin dermis
dense regular connective tissue
dense parallel orientation of (type I) collagen fibres -> max strength, withstand tensile force in one dir.
attach bones & muscles, stabilize & support joint
cells producing & maintaining fibres packed & aligned btn collagen bundles
little ECM, relatively avascular
e.g. tendon, ligament
