Connective tissue Flashcards
1
Q
Origin of CT
A
-Mainly derived from undifferentiated mesenchymal cells
-Also, haematopoietic stem cell line:
Monocytes, macrophages, lymphocytes and mast cells, blood cells
2
Q
Constituents of CT
A
- Cellular component-fibroblasts/adipocytes, Adipose cells.
- Visible fibres- collagen, elastic, reticulin.
- Ground substance (hydrophilic jelly)-proteoglycans and glycosaminoglycans (GAGs). Invisible fibres-laminin and fibronectin.
- Ground substance doesn’t stain with H and E therefore appears as white spaces on histological slides.
3
Q
Types of Connective Tissue (CT)
A
- Fibrous-loose and dense
- Hard-cartilage and bone
- Fatty-white and brown
4
Q
Collagen: principle extracellular fibre
A
- Tropocollagen-triple helix of peptides
- Fibroblasts-secrete tropocollagen subunits
- Fibroblasts produces elastic fibres and sheets
- Fibres-assembled extra-cellularly
- Collagen cells may be longer than the cells that produce them
- Not elastic or contractile
5
Q
Types of Collagen
-More than 20
A
- Type 1 skin and bone, tendons
- Type 2-cartilage
- Type 3 liver, bone marrow, spleen
- Type 4 basement membranes of epithelia
- Type 5 placenta
6
Q
Collagen Fibres
A
- Extracellular fibres that stain pink with H&E
- Variable thickness and length, often run in bundles
- Sometimes confused for muscle fibres (intracellular-nucleus lies within them) that also stain pink but collagen fibres are extracellular.
- Most forms of collagen form linear fibres
7
Q
Loose Connective Tissue
A
- widely spaced thin collagen fibres
- fibroblasts/fibrocytes that secrete them (blasts when immature and cytes when matured)
- Unstained ground substance
8
Q
Dense Connective Tissue
A
- closely packed thick collagen fibres
- Fibroblasts/fibrocytes
- Unstained ground substance (less abundant than seen in loose ct)
- May be irregular or regular depending on arrangement of collagen fibres and fibroblasts/fibrocytes within it.
- Irregular-arranged haphazardly, found in penis
- Regular- collagen fibres and fibroblasts regularly arranged running parallel to one another, found in tendons.
9
Q
Reticulin
A
- Type 3 collagen.
- Forms branched fibres.
- Fibrillar collagen
- Forms a supporting scaffold in blood cells and many organs: bone marrow, liver, kidney, lymph node and spleen
- Not visible on H&E-need silver stain
10
Q
Elastin
A
- Elastic tissue contains fine fibres and sheets of elastin
- Elastin fibres may be branched/unbranched
- Produced by fibroblasts
- Stain pink on H&E
- Easily confused with smooth muscle cells
11
Q
White Adipose (fatty) Tissue
A
- Large cells with single fat globule in each cell. Pushes remainder of cytoplasm and nucleus to edge of cell
- Usually appear empty (white) in conventional slides as fat is extracted during processing
- Don’t confuse with alveoli of lungs. Lung tissue contains airways but white adipose tissue doesn’t.
12
Q
Brown Adipose (Fatty) Tissue
A
- Cells with many globules of fat. Pink foamy appearance.
- Found across shoulders and down back of neck
- Important in neonatal thermo-regulation (generate heat on breakdown).
13
Q
Cartilage: 3 Types
A
-Cells-chondroblasts, chondrocytes
Extracellular matrix:
- Glycosaminoglycans-Hyaluronic acid.
- Proteoglycans-Condroitin sulphate, keratin glycan
- Extracellular fibres-collagen, elastin
- Cartilage is avascular- derives blood supply from vessels on either side of cartilage.
14
Q
Hyaline Cartilage
A
- Found in synovial joints
- Chondrocytes in lacunae surrounded by a glassy amorphous matrix (blue/grey)
- Chondrocytes appear in clumps in matrix
- No visible fibres
- Perichondrium-fibroblasts and collagen.
15
Q
Elastic Cartilage
A
- Found in pinna of ear and epiglottis
- Visible elastic fibres in matrix (blue/grey)
- Perichondrium-fibroblasts and collagen
