Medicine Notes Organisation of the Body Notes
1st year Oxford notes and tutorial essays in the module Organisation of the body. ...
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Connective tissue
Definition: association of the extracellular matrix and the various cell types within it. It varies in type and amount in different locations of the body.
Functions:
Mechanical
-supporting matrix for highly organised structures such as the blood, nerve, lymp
-force transmitter- tendon-MUSCLE to bone, ligaments- bone to bone
-facilitates movement between structures
Metabolic
-route for exchange between metabolites and regulatory molecules- between the blood and tissues between blood and tissues
-storage of fat- subcutaneous and mesentries
Defense
-fat in the superficial fascia forms an insulating layer. Fat in the loculi of loose connective tissue of the dermis provides cushioning and padding
-Inflammation- macrophages and mast cells of the connective tissue- inflammation- local response to bacteria
Repair- after injury fibroblasts lay down collagen fibres- scar tissue
STRUCTURE
-cells
Fibroblasts-STRUCTURAL ROLE: embryonic mesenchyme- secrete most of the extracellular matrix components (fibres and ground substancs)
-GAG, PROTEOGLYCANS, COLLAGEN, ELASTIC, GLYCOPROTEINS , GROWTH FACTORS
-Secrete fibroblast growth factors- mutation in FGF3R leads to Achondroplasia
-plays a role in wound healing
-active and quiescent forms are distinct-
-active fibroblasts have euchromatin and a prominent nucleolus and ovid shaped nuclei
-queicsent fibroblasts have fusiform cells, less ERcytoplasm is elongated into a thin line
-Secretes glycogen in a particular orientation
Macrophages: DEFENCE-phagocytosis, antigen presentation, cytokine secretion
- resident phagocytic cells- blood monocytes-engulf and remove invading organisms and dead cells- secrete cytokines the local inflammatory response – recruit other phagocytic cells such as leucocytes from the blood stream
-specialised roles in certain tissues: Kuppfer cells (liver), microgilia (CNS), Langerhan’s cells (epidermis),osteoclasts in bone
Mast cells
-contain secretory granules containing bioactive molecules-histamine, serotonin, tumour necrosis factor, proteases, heparin, prostaglandins
-activation of IgE receptors on cell surface- activation of mast cells, release the mast cells granules- vasodilation, increase capillary permeability, breakdown of ECM- inflammatory response
adipose cells
- white adipose cells- single large droplet of lipid- energy storage, insulation, padding and shock absorber
- brown adipose cells- fat globules are smaller and numerous-heat productions
Matrix- ground substance
GAG-long unbranched polysaccharide chains- repeating disaccharide units- amino sugar- N-acetylglucosamine) chondroitin sulphate, keratin sulphate
-Highly anionic- attract sodium ions and water which leads to swelling, turgor and resists compression in joints
-stornly hydrophilic-porous hydrated gels
proteoglycans- covalent linkage GAG to core protein-aggrecan found in cartilage-control the activity of growth factors
glycoproteins- laminin and fibronectin- EXTRACELLULAR matrix –cells can attach to and move through the matrix- bind to integrins
-integrin receptors in the plasma membrane link the cytoskeleton to extracellular glycoproteins and collagen
Fibres
-Collagen-
-made up of three alpha helix chains, rod like super helix- fibrils, fibres
-Type 1: found in tendons and bones- resists tension
-type 2: found in hyaline cartilage- reisist pressure
-Type 3: found in skin, muscles and vessels- resists deformation on expansion
- type 4 sheets basal lamna
-collagen is arranged in a staggered fashion that is cross linked to form fibrils and many of these fibrils are linked together to form fibres- banded appearance- electron microscopy- collagen is stained using H&E stain- pink stain
Collagen Type I biosynthesis:
Preprocollagenα chains synthesised
Signal peptide cleaved to form procollagen
Hydroxylation of specific prolyl and lysyl residues by peptidylproline/lysine hydroxylases
Requires Vitamin C as cofactor
Glycosylation of hydroxylysines: glucosyl/galactosyl groups added
Self-assembly of procollagen triple helix with N and C registration peptides
Secretion
Procollagen Peptidase catalyses formation of Tropocollagen(a...
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1st year Oxford notes and tutorial essays in the module Organisation of the body. ...
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