Connective tissue Flashcards
Embryonic connective tissue and example
Embryonic CT derived from mesoderm and contains large amounts of proteoglycans in ECM and less collagen and reticular fibers. Contains Mesenchymal cells
Eg:
1. Umbilical cord (Wharton’s Jelly) - contains hydrophilic ECM
2. Pulp of a developing tooth
Adult connective tissue
- Loose (aerolar) CT: contains more cells compared to collagen fibers. Eg: blood vessels, nerves and muscle
- Dense CT: contains more collagen fibers than cells
a. Regular dense CT: collagen fibers oragnised in regular direction eg: Tendon, ligament and retina
b. Irregular dense CT: collagen fibers organised irregularly Eg: epidermis of the skin and submucosa of alimentary tube - Reticular CT: contains reticular fiber eg: lymphoid organs, liver and haematopoietic bone marrow
- Elastic CT: contains elastic fibers eg: aorta to provide elasticity
Components of CT
- Cells - Fibroblast, mastcells, macrophages, plasma cells
- ECM
- Fibers: collagen, reticular, elastic
Specialised CT
- Adipose tissue - contains more adipocytes than collagen and ECM. Function for energy storage
- Cartilage- contains uncalcified ECM
- Bone - contains calcified ECM
- Haematopoietic tissue
Fibroblast
- Can produce all components of ECM, collagen and reticular fibers
- Contains rER and Golgi
- Spindle shaped with elliptical nucleus
- Can synthesize and continuously secrete proteoglycans,
glycoproteins and precursors for collagen and reticular fibers
ECM composition
- contains axial of hyaluronan
- linker protein for attachment of core protein to axial
- proteoglycan - consisting of core protein and glycosaminoglycan assembly
Collagen synthesis
- Procollagen and precollagen in rER - glycosylation, disulfide bond formation and hydroxylation of lysine and proline
- Golgi - packaging of preprocollagen and secretion
- before leaving in ECM - trimming of uncoiled portion of N-terminal and C-terminal produces tropocollagen from procollagen
- Tropocollagen produces collagen fibril by staggered array arrangement
- Collagen fibril joined side by side to form collagen fibre - process facilitated by proteoglycans and FACIT collagen
Types of Collagen
Type I - for tensile strength found in bone, tendon, dentin and skin
Type II - found in hyaline cartilage
Type III - reticular fiber. produces mesh work and found around soft tissue like lymphoid tissue, liver and bone marrow. first synthesized during wound healing then replaced by Type I
Type IV - found in basal lamina
Type V - found in amnion and chorion of embryonic tissue and muscle and tendons
Type VII - provide anchoring. Link ECM to basement membrane
Which vitamin is essential for hydroxylation of proline and lysine during collagen synthesis
Vitamin C and deficiency leads to scruvy
Cell sources for collagen
Fibroblast
Osteoblast (Bone), Odontoblast (teeth), Chondroblast (cartilage)
Reticular cells
Smooth muscle cells in arteries, respiratory tract - produces type I and III
Epithelial cell - produces type IV
Which fibers lack collagen
Elastic
Synthesis of elastic fiber
- rER: Starts with proelastin which converts to tropoelastin after cleavage
- Golgi: packaging of tropoelastin, fibrilin 1 and 2 and fibulin 1
- tropoelastin contains desmosine - linkage with fibrilin and fibulin to produce elastic fiber
Which connective tissue is avascular
Cartilage
