Connective tissue Flashcards
What is connective tissue? and where does it come from ?
Tissues that provide structure, strength and support
derived from embryonic mesoderm
Characterised by abundance of matrix with few cells
ECM consists of fibres and ground substance
What are the 3 properties of connective tissue?
- Tensile strength (collagen)
- Elasticity (elastin)
- Volume (ground substance)
What is the ECM made up of?
Fibres and ground substance and tissue fluid
What is the ECM produced by?
Fibroblasts
What do fibres contribute to ECM?
Tensile strength, elastic recoil and defined structure
What is ground substance made of?
Glycosaminoglycans and glycoproteins
What does ground substance contribute to ECM?
Hydration → Resistance to compression
10% GAGs in ECM, the rest is water so lots of spaces for diffusion
Fibre cross-linking
What is type I collagen?
Main structural collagen. forms skin, tendons, ligaments and bone
What is another name for type II collagen?
Hyaline cartilage
What does hyaline cartilage make up?
Nose and larynx
What does type III collagen make up?
Liver, bone marrow, lymphoid organs
What is another name for type III collagen?
Reticular collagen
What is the function of elastin fibres?
Allow tissues to respond to stretch and distension
What causes skin ageing?
Reduced density of collagen and elastin
What is the function of fibroblasts?
Secrete, maintain and recycle ECM
(synthesise and secrete GAGs, collagen, elastin and other ECM parts)
What is the main fibre in connective tissue and how is it made?
Collagen fibres- secreted by ECM to form tropo-collagen monomer
What is ground substance?
semi-solid gel that provides volume and compression resistance
4 tissue types
nerve
muscle
connective
epithelium
what is the epithelium and its functions
derived from either one of the 3 germ layers (ectoderm, mesoderm, endoderm)
tissue which covers or lines a surface of an organ.
has a free surface - exposed to external environment
functions:
protects underlying tissue
separates areas of body
thermoregulation
hormone release
absorption
what is muscle tissue and where is it derived from ?
derived from mesoderm
composed of cells (or multinucleated syncytia) whose cytoplasm contains filaments made of contractile proteins (actin, myosin etc)
what is nervous tissue and where is it derived from?
develop from neuro-ectoderm
consist of cells of which possess axons and dendrites which conduct impulses when stimulated
Where can epithelia be found?
epithelia - on surfaces
endothelium - lining blood vessels
mesothelium - lining body cavities
types of epithelium
simple - 1 layer
stratified = many layers
cuboidal = cube shaped
columnal = tall
transitional = can change shape
what type of epithelium shape and where would it be found :
A) provides protection ?
B) facilitates diffusion?
C) is absorbative/secretory ?
D) is stretchy?
stratified squamous ; areas of wear and tear e.g skin, oesophagus
simple squamous ; alveoli and capillaries
columnar (space needed for lots of organelles) ; small intestine/glands
with cilia as well if absorbative
transitional ; bladder
Where in the body would we expect to find
- Simple squamous?
- Simple columnar?
- Simple columnar with microvilli?
- Columnar (pseudostratified) with cilia?
- Simple cuboidal
- Stratified squamous?
- Transitional?
alveoli , endothelium
glands
small intestine
lining airways
in gland ducts /convoluted tubules in kidneys
areas of wear and tear
bladder
basement membrane
structure(what is it made of) and functions
sheets of matrix (not cells) that site between the epithelium and connective tissue
•Composed mainly of type 4 collagen, glycoproteins (laminin secreted by epithelial cells. Fibronectin from fibroblasts) and glycosaminoglycans (GAGs)
i.e the basement membrane is made by the cells above and below it
functions:
- adhesion of epitelium to organ below,
- barrier (selectively permeability),
- organisation of cells
(controlling growth and
differentiation) - tells cells which way is up
shape and structure of glands
secretory portion has a columnar epithelium
duct part has cuboidal epithelium
glands are derivatives of epithelia
difference between exocrine and endocrine glands
•Exocrine glands
Secrete their products onto the epithelial surface directly or via a duct for local action e.g. Sweat glands, liver
•Endocrine glands
Release their secretions directly into the blood to act on different tissues e.g. Pituitary and thyroid glands
far acting
what is merocrine
merocrine - release via golgi vesicles
elastin fibres structure
stropoelastin polymerises to elastin
requires fibrillin(glycoprotein) for assembly
what is type III collagen called
what is its main features
reticulin
mesh of thin branched fibres
process of collagen formation
procollagen made by fibroblasts inside the cell
assembled into collagen fibres outside cell
name the 3 main examples of glycoproteins found in ECM
fibrillin - a microfibre needed to make elastin
fribronectin - involved in maintaining collagen structure / binds to cells via integrins (membrane-spanning receptor proteins)
laminin (forms major part of BM)
glycosaminoglycans
examples and functions
they are polysaccharide chains made of repeating disaccharide units
hydrophilic so attract water
stabilize the CT by binding to collagen and elastic fibers, cells and water. also absorb forces
- Chondroitin sulfate
- Heparan sulfate
- Hyaluronan
- Keratan sulfate
types of connective tissue
●Loose: packing material - filling gaps between glands
●Dense: tough physical support: dermis, organ capsule, ligaments, tendons
●Areolar: fatty
●Specialised support: cartilage and bone
●Metabolic: adipose tissue
●Immune: contain immune cells (mast cells, tissue macrophages, WBCs, plasma cells) and effect repair
what is apocrine
apocrine - release via budding of membrane
what is holocrine ?
holocrine - release via cell death
roles of connective tissue
Mechanical and structural role
carry blood and lymph vessels
Mediate exchange of nutrients, metabolites and waste products from blood and tissues
