week 5: tissues of the body - CT Flashcards
origin of CT
- mesoderm –> fibrous tissue, bone, cartilage, fluid tissue (blood)
- some from ectoderm –> neural crest (odontoblasts and skull bones)
what is CT first formed
formed from mesenchyme, which contains abundant AGS, primitive mesenchymal cells and few retiicular fibres
- primitive mesenchymal cells gives rise to –> stem blood cells, and CT cells
what makes up extracellular matrix?
- fibres
- AGS
what makes up CT
- extracellular matrix (fibres and AGS)
- cells
fibres in CT their function
- collagen fibres
- connects and binds tissues and organs
- transmits forces
- support, shapes and flexibility
- provides mechanical protection - reticular fibres
- gives support, shape and flexibility
- net-like framework - elastic fibres
- gives support, shape and flexibility
- elasticity
what are the cell types of CT and their function
- macrophages, leukocytes, and plasma cells
- provides immune protection - adipocytes
- stores enegy and acts as insulation - mesenchymal cells
- stem cells which can differentiate into other cell types of the matrix - fibroblasts
- produces the CT - collagen type I, III, and Iv, and proteoglycans
components of AGS and function
- proteoglycans –> protein core with attached GAGs (hihgly negative and attracts water)
- provides medium for exchange of nutrients and waste products
- between cells and fibres
- fluid/gell-like
what are the 3 classifications of CT
- loose CT
- dense CT (regular or irregular)
- specialised CT
what is loose CT
- more cells + AGS than fibres
- types of loose CT = Adipose (breast tissue), areolar (under the dermis) and reticular (basement membrane)
what is dense CT
- more fibres than AGS + cells
- regular = fibres run parallel and can withstand tensile stresses (strong in one direction) , e.g. elastic CT in elastic arteries.
- irregular = fibres run in all directions :. good at counteracting stress in all directions.
exampls of specialised CT
- blood
- bone
- cartilage
what is the function of dense CT
- dense irregular CT
- Connects and binds other tissue types and organs
- transmits forces in all directions
- gives support and shape
- mechanical protection - dense regular CT
- provides strength and transmits forces in one direction
function of specialised CT and give an example of specialised CT
- gives support and shape
- e.g. cartilage and bone
types of dense regular CT
- tendons
- ligaments
function of loose CT
- stores energy and acts as insulation (adipocytes)
- transports nutrients and waste products between blood and epithelium
- protects body from infection via the immune cells present.
collagen: moleculear composition, morphological characteristics, distribution and function
MOLECULAR COMPOSITION:
- type I collagen
- primarily composed of collagen protein
- 3 polypeptide chains joined together ina triple helix configuration
MORPHOLOGICAL CHARACTERISTICS
- thick, strong, felxible,
- rope-like appearence
- appear as densly packed bundles of fibrils
DISTRIBUTION
- found in various types of CT - tendons, ligaments, skin, bones, cartilage, blood vessles.
FUNCTION
- provide tensile strenght to CT
- mechanical strenght, support and resistance to stretching
- structural integrity of the tissue
- role in wound repair and healing.
Elastic : moleculear composition, morphological characteristics, distribution and function
MOLECULAR COMPOSITION:
- composed of amorphous elastin proteins (elasticity) and glycoprotein microfibrils (scaffolding support for fibres)
- elastin is a random coiled structure when relaxed and elongated when stretched
MORPHOLOGICAL CHARACTERISTICS
- thin and long - rubber band like –> thinnest fibre
- under microscope, appear: wavy, coiled or branched in nature. –> enables fibres to stretch when tension is applied and recold to original shape when tension is released.
DISTRIBUTION
- in tissues that require elasticity and resilience.
- in skin, blood vessles, lungs,ligaments, vocal cords and elastic cartilage
FUNCTION
- passive stretch and recoil.
Reticular : moleculear composition, morphological characteristics, distribution and function
MOLECULAR COMPOSITION:
- mainly composed of type III collagen –> thinner and more delicate than type I collagen in collagen fibres
MORPHOLOGICAL CHARACTERISTICS
- branching and delicate structure
- under microscope = fine, irregular arrangment –> mesh-like
- fibers interconnect –> supportive framework for structural organisation within tissue.
DISTRIBUTION
- found in spleen, bone marrow and lymph nodes.
- forms reticular lamina in basement membrane.
FUNCTION
- provides supportive yet flexible framework for cells and other components of the tissue.
types of collagen (I - IV), structure, location found, function
- Collagen type I
- structure: fibrils, fibre bundles
- location: most CT, dermis, tendon, ligament, bone, dentine
- function: resistance to stress and tension; enables flexibility within tissue. transfer of unidirectional forces - Collagen type II
- structure: fibrils only
- location: cartilage
- function: provides resistance to pressure - collagen type III
- structure: fibrils and fibres
- location: reticular fibres, cellular organs
- function: delicate, flexible framework - collagen type IV
- structure: network sheet
- location: basal lamina
- function: support of delicate structures - filtration.
collagen type III and IV make up basement membrane
what is oedema?
abnormal accumulation of interstitial fluid`
function of macrophages
- antigen presentation
function of plasma cell
syntheis of antibodies
function of neutrophils
neutralises bacterial infection
function of mast cells
increases permeability of blood capillaries.
fibroblast appearance
- flattened ovoid nucleus
- only nucleus visible in H&E section
fibrocytes appearance
- does not appear as dark as fibroblasts in H&E due to reduced protein production
adipocytes appearance
- H&E: huge cell with a thin rim of cytoplasm arround a clear lipid droplet; peripheral nucleus
- EM: lipid droplet fixed and coloured grey-black. thin basal lamina type structure surrounding each cell
macrophage apperarance
- H&E: when inactive - only nucleus is visible (roundish and dented); cytoplasm contains visible phagosomes and lysosomes
- EM: pseudopodia with microfilaments for phagocytosis and cell mobility.
plasma cells appearance
- LM: ovoid cell, basophillic, nucleus off centre, clock face clumping of chromatin
- EM: abundant RER, extensive gogli, no seretory granules.
mast cell appearance
- H&E: indistinguishable, large basopbillic cytoplasm, granules filled with heprin
- located near capillaries
leukocytes appearance
- lymphocytes = small round cells, dark round nucleus
- neutrophils = lobulated nucleus
- eosinophils = bring red granules in cytoplasm and 2 lobes to nucleus.
function of fibroblasts
- younger, immature cell
- more active in protein production and production of intracellular matrix
- respond to injury by dividing and producing large amounts of collagen –> form scar tissue during healing.
function of fibrocytes
- mature cell
- less protein production
- maintains intercellular components
- during CT injury –> can revert to actove form.
function of adipocytes
- stores fat as energy source
- clumped together for insulation
- acts as a shock absorber; protective padding
function of macrophage
- defence cell that phagocytoses
- ## antigen presenting cell –> initiate immune response
function of plasma cell
- produces antibodies
function of mast cell
- storage of chemical mediators of inflammatory response
- allergy reactions
- release heprin and histamine
function of lymphocytes
- principle cell in immune reaction
function of neutrophils
- neutralises bacterial infection
function of eosinophils
- accumulated in parasitic infection and allergy reaction
CT structure that connects bone to bone
ligaments
CT structure that connects bone to muscle
tendon
