Connective Tissue Flashcards
Ground Substance and GAGs
- composed. of water, proteins and polysaccharides
- polysaccharides are glycosaminoglycans (GAGS) which are long, unbranched polysaccharides , repeating disaccharide units
- GAGs join with core proteins to form proteoglycans
- GAGs trap and attract water (highly polar)
Sulphate GAGs - bind to proteins to form proteoglycans
Non-sulphated GAGs - hyaluronic acid
-does not bind directly to protein backbones but joined to various proteoglycan links
GAGs applications and exophthalmos
Hyaluronic acid - viscous, slippery substance binds cells together, lubricates joints and maintains shape of eyeball
Hyaluronidase - produced by white blood cells, sperm and some bacteria, makes GS more liquid
Chondriotin sulphate - supports and provides the adhesive features of cartilage, bone, skin and blood vessels
Keratan sulphate - found in bone, cartilage and cornea of the eye
Dermatan sulphate - found in skin, tendons, blood vessels and heart valves
Periorbital ECM deposition and thyroid disease (exophtalmos)
-common in younger women, goitre (swollwn thyroid gland), autoimmune over activation of thyroid and fibroblasts in ECM of eye causing influx of water which increases orbital contents
3 Protein fibres of ECM
Collagen fibres - thick, very strong, flexible to resist pulling forces, features vary, make up 25% of your body, most abundant protein, parallel bundles, common in bone, cartilage, tendons and ligaments
Reticular fibres - composed of collage with glycoprotein coating, made by fibroblasts, strength and support, form part of BM, thinner and branching, forms network
Elastic fibres - thinner than collagen fibres, fibrous network, protein elastin surrounded by glycoprotein fibrillin for strength and stability, can be stretched q50% without breaking, skin, blood vessels and lung
Marfan syndrome
- defect in elastic fibres
- hereditary defect resulting from dominant mutation on a gene from chromosome 15 coding for fibrillin
- TGFb (growth factor) produced by body
- individuals with Marfan syndrome are usulaly tall, long limbed, chest deformity, normal lifespan but medical vigilance for blood pressure control, weakened heart valves and arterial walls
- 1 in 20,000 births
Connective tissue cell types
Fibroblasts - migratory, widely distributed in connective tissue, secrete components of ECM (fibres and GS)
Adipocytes (fat cells) - under skin and around organs, stores fat (triglycerides)
Macrophages (histiocytes)
- dust cells: lung
- kupffer cells: liver
- langerhans cells: skin
- wandering in CT - sites of infection, inflammation and injury
Connective tissue classification
-embryonic or mature
Embryonic
- type 1: mesenchyme - gives ruse to all other connective tissue, consists of connective tissue cells (mesenchymal cells) in a semi-fluid ground substance containing reticular fibres
- type 2: mucous. -has widely scattered fibroblasts embedded in jelly like ground substance, supports umbilical cord of foetus
Mature
-loose proper, dense proper, blood, lymph, cartilage and bone
Loose proper CT
-many cells, fewer fibres
Areolar connective tissue - 3 fibre types present, widely distributed around almost every structure, strength, elasticity and support
Adipose connective tissue - adipocytes dominant, found with areolar tissue including fibroblasts, insulation, energy source and temperature control
- white adipose = energy storage
- brown adipose = heat production
Reticular connective tissue - fine interlacing network of reticular fibres and reticular cells, fond in stromas of many organs as well as reticular lamina of BM, red bone marrow and around blood vessels and muscles
Dense proper CT
Regular dense connective tissue - tendons, ligaments, aponeuroses, regularly arranged collagen, shiny white colour, slow healing, for attatchment
Irregular dense connective tissue - made up of collagen fibres usually irregularly arranged with few fibroblasts, located in sheets often, dermis of skin, tensile pulling strength in many directions
Elastic dense connective tissue - contains elastic fibres mainly with fibroblasts between
Cartilage CT
-dense network of collagen and elastic fibres embedded in chondroitin sulphate
Hyaline cartilage - abundant, weak, gel where fibres are present but not obvious, flexibility and movement
Elastic cartilage - chondrocytes in threadlike network of elastic fibres within ECM, strength and elasticity, maintains shape of certain structures
Fibrous cartilage - has chondrocytes among clearly visible thick bundle of collagen fibres within ECM, no perichondrium (elastic cartilage has), support and joining of structures, strongest cartilage type
Bone CT
-bones are organs composed of several CT types including bone tissue
Compact bone - outer layer of bone, forms shafts of long bones, known as cortical bone, composed of osteons/harvesian systems, stores calcium and phosphorus, protection and support
Spongy bone - porous inner bone that lies underneath compact bone, known as cancellous bone, lacks osteons, stores triglycerides (yellow marrow) and produces blood cells (red marrow), consists of columns of bone called trabeculae
Bone CT. cell types
Osteogenic cells - mesenchymal stem cells that develop, start to lay down collagen, become trapped and become osteoblasts
Osteoblasts - bone forming cells, lay down collagen more, mineralisation process starts
Osteocytes - mature bone cells, maintain bone tissue, involved in exchange of nutrients and wastes, have gap junctions
Osteoclasts - large, multinucleated cells, formed from the fusion of blood monocytes, break down bone (resorption, breakdown of bone matrix)
Osteon structure (harvesian system)
- osteons are aligned along lines of stress (long axis of bone shaft)
- basic unit of compact bone
Lamellae - concentric rings of mineral shafts for hardness and collagen for tensile strength
Lacunae - small spaces between lamellae that contain osteocytes
Canaliculi - minute canals containing extracellular fluid and minute osteocytic processes that radiate from lacunae and provide routes for oxygen, nutrients and waste
Central (harvesian) canal - blood, lymph and nerves
