IAS21

Question 1

embryonic origin of connective tissues

Answer 1

all from mesoderm (mesenchyme)

Question 2

general connective tissue function

Answer 2

1. material exchange (through blood vessel, deliver nutrients, remove wastes)
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

Question 3

ECM ground substances

Answer 3

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

Question 4

ground substance function

Answer 4

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

Question 5

hyaluronic acid

Answer 5

linear, non-sulphated GAG
viscous, slippery, good lubricant -> reduce friction e.g. joint

Question 6

proteoglycan

Answer 6

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

Question 7

glycoprotein

Answer 7

adhesion proteins
links components of ground substance to surface of cell
e.g. fibronectin (common), laminin (basal lamina), osteopontin (bone ECM)

Question 8

collagen

Answer 8

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

Question 9

collagen in wound healing

Answer 9

fibroblasts produce type III first -> forms a mesh near injured site & scaffolds for tissue injury
type III replaced by stronger type I during recovery

Question 10

reticular fibres & staining

Answer 10

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

Question 11

elastic fibre

Answer 11

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

Question 12

marfan syndrome

Answer 12

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

Question 13

cellular components of connective tissue

Answer 13

resident cells: low motility
transient cells: mobile, temporary

Question 14

fibroblast

Answer 14

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

Question 15

adipocyte types, structure & distribution

Answer 15

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

Question 16

adipocyte functions & mechanisms

Answer 16

WAT: fuel storage, fatty acid DNS, release of FA when other tissues need them, form TAG from FFA from lipoproteins (chylomicrons & VLDL)
BAT: fuel storage, thermoregulation (releases heat to keep infants & organs warm), endocrine regulation

Question 17

macrophage

Answer 17

phagocytic cells derived from monocyte
engulf pathogens, dead cells & RBC by phagocytosis, contain many lysosomes, innate defence & immune response

Question 18

macrophages as antigen-presenting cells

Answer 18

lysosome fused w/ phagosome -> antigen broken down into smaller peptide frags -> bind to MHC -> phagocytic vesicle fuses w/ plasma membrane -> antigen presented to T cell

Question 19

mast cell

Answer 19

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

Question 20

plasma cell

Answer 20

derived from activated B lymphocytes
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.

Question 21

connective tissue proper

Answer 21

fibrous component predominant: loose (areolar) & dense

Question 22

loose connective tissue

Answer 22

more cells than fibers
fiber network filled w/ ground substance
mostly transient cells migrating from local vessels in response to specific stimuluis -> site of inflammatory & immune responses
e.g. lamina propria under epithelia, dermis of skin, mesentry

Question 23

dense connective tissue

Answer 23

more fibers than cells, regular vs irregular

Question 24

dense irregular connective tissue

Answer 24

large amt of collagen fibres organised into thick bundles in random dir., matrix relatively acellular
functions same as collagen e.g. capsule of glands & organs

Question 25

dense regular connective tissue

Answer 25

dense parallel orientation of collagen fibres -> max strength, withstand tensile force in one dir.
cells producing & maintaining fibres packed & aligned btn collagen bundles
little ECM, relatively avascular e.g. tendon, ligament