ANAT241 Lecture 10 - Connective (Support) Tissue and the Extracellular Matrix Flashcards
what are connective (support) tissues?
tissues that provide general structure, physical + metabolic support for more specialised tissues, mechanical strength (tension for tendons/bones) and fills spaces in the body
what are the 3 key properties of connective tissues?
tensile strength from collagen
elasticity from elastin
volume from ground substance
what provides tensile strength of connective tissue?
collagen
what provides elasticity of connective tissue?
elastin
what provides volume of connective tissue?
ground substance
what do collagen and elastin have in common?
they are both fibular
what is ground substance?
a mixture of various types of molecules that bind water to create volume?
what are the 4 classes of connective tissue?
connective tissue proper
cartilage connective tissue
bone connective tissue
blood connective tissue
what can connective tissue proper be divided into?
loose connective tissue proper or dense connective tissue proper
what is loose connective tissue proper?
an open and loose structure
what are the 3 types of loose connective tissue proper?
areolar tissue
reticular tissue
adipose tissue
what is areolar tissue of loose connective tissue proper?
areolar tissue is strong yet cushioning and forms the lamina propria by underlying epithelium
what does areolar tissue form?
forms the lamina propria by underlying epithelium
what is reticular tissue of loose connective tissue proper composed of?
composed of reticular fibres that form a supportive mesh to support organs
what is the function of reticular tissue?
forms a supportive mesh to support organs
what is adipose tissue of loose connective tissue proper made up of?
made up of adipocytes
what is the function of white adipose tissue?
to store energy
what is brown adipose tissue associated with?
associated with thermoregulation
what are the 2 types of dense connective tissue proper?
regular dense tissue and irregular dense tissue
what is the relationship between dense connective tissue proper and the proportion of fibres it contains?
dense connective tissue proper contains a large proportion of fibres
what is regular dense tissue of dense connective tissue proper?
regular dense tissue arranged in parallel fibres of mainly type I collagen
where is regular dense tissue of dense connective tissue proper found?
found in ligaments and tendons
what is irregular dense tissue of dense connective tissue proper?
irregular dense tissue arranged in non-parallel fibres
where is irregular dense tissue of dense connective tissue proper found?
found in the dermis
what is the relationship between dense connective tissue proper and ground substance?
dense connective tissue proper has little ground substance
what are the 3 types of cartilage connective tissue?
hyaline cartilage
fibrocartilage
elastic cartilage
what is hyaline cartilage of cartilage connective tissue?
smooth and translucent cartilage with few collagen fibres supported by semi rigid chondrocytes
what are chondrocytes?
the support cells of hyaline cartilage that are semi rigid
what does fibrocartilage contain?
many collagen fibres
where is fibrocartilage present?
present in cartilaginous joints
e.g the mensci of the knee joint
what is elastic cartilage of cartilage connective tissue made up of?
made up of elastin and collagen fibres
where is elastic cartilage present?
present in the ear
what is bone connective tissue?
a collagen containing matrix that becomes calcified
where is compact bone positioned?
positioned on the outside for strength
where is cancellous/spongy bone positioned?
arranged in the middle to form the trabeculae
what does the arrangement of bone depend on?
depends on the stress/weight bearing nature of the bone
what are the 2 key components of connective tissue?
cells and the ECM
what determines the properties of the connective tissue?
the constituents of the ECM
what are support cells for connective tissue derived from?
derived from embryological tissue mesenchyme which is a type of connective tissue
what do support cells produce?
produce the ECM components
what is mesenchyme the common embryonic origin for?
fibroblasts
chondroblasts
osteoblasts
what is the development of fibroblasts?
fibroblasts –> fibrocyte –> connective tissue proper
what is the development of chondroblasts?
chondroblast –> chondrocyte –> cartilage
what is the development of osteoblasts?
osteoblast –> osteocyte –> bone (osseous)
what do fibroblasts produce?
produce cells that secrete the ECM
what is the matrix of connective tissue proper?
jelly-like matrix
what is the matrix of adipose tissue
very little matrix
what is the matrix of cartilage?
firm almost solid matrix
what is the matrix of bone?
solid and rigid matrix
what 3 things compose the ECM?
ground substance
fibrillar proteins
adhesion proteins
what are the structural glycoproteins present in the ground substance?
glucoaminoglycans (GAGs) and proteoglycans
what are GAGs (glucoaminoglycans)?
2 different sugar chains in a very long unbranching polysaccharide
what are proteoglycans?
proteins that bind covalently to GAGs (glucoaminoglycans)
what fibrillar proteins?
fibres that provide strength and elasticity
what do adhesion proteins link together?
link fibres, ground substance and cells together
what is the most common GAG (glucoaminoglycan)?
hyaluronic acid (hyaluronate)
what is hyaluronic acid?
a long linear molecule of 2 repeating sugar molecules
what is the other GAG (not hyaluronic acid)?
dermaton sulphate
what is the relationship between dermaton sulphate and hyaluronic acid?
dermaton sulphate GAGs attach via hyaluronic acid as proteoglycans
why are GAG’s hydrophillic?
these molecules are hydrophilic as they are negatively charged
what do proteoglycans and GAGs interact with?
interact with each other
water + salt
collagen
other fibres + molecules
what is the most abundant protein the human body?
collagen
why is collagen the most abundant protein in the human body?
because it is found in most supporting tissues
what is collagen secreted by?
secreted by fibroblasts
what colour does collagen stain from the H&E stain?
pink
what is collagen in terms of fibres?
a series of twisted protein fibres
what is the relationship between collagen fibres and the electron microscope?
collagen fibres are banded under the electron microscope due to the overlap between the triple helices
how many different types of collagen are there?
28 different types
what is type I collagen?
makes up around 90% of collagen in the body and composes ligaments, tendons, bone and skin
what is type II collagen?
cartilage
what is type III collagen?
reticular tissue that forms reticular fibres
what is type IV collagen?
the basement membrane
what is the function of adhesion glycoproteins?
mediate interactions between cell cytoskeletons and the ECM
what is fibronectin?
an adhesion protein that is a dimeric glycoprotein that binds collagen to intergrins on the cell surface + proteoglycans + cells
what is laminin?
an adhesion protein that binds multiple ECM components that forms sheets that makeup the basement membrane and binds cells to the basement membrane (integrins)
what are cell-matrix adhesion mechanisms?
junctions between cells and the ECM that are important for maintaining structural integrity
what is the function of focal adhesions?
bind cells to the ECM
what is the function of hemidesmosomes?
attach epithelial cells to the basement membrane
what are the 4 methods cells use to anchor to the ECM?
1) GAGs and proteoglycans anchor to the matrix
2) collagen and elastin anchor to structural fibres
3) fibronectin and laminin anchor to adhesive glycoproteins
4) integrins anchor to transmembrane receptors
what do integrin proteins interact with?
interact with other proteins on both sides of the lipid bilayer
how do support cells bind to the ECM?
via focal adhesions
how do cells anchor to the basement membrane?
cells anchor to the basement membrane as intermediate filaments (cytokeratin) attach to stationary epithelial cells that bind to the ECM via hemidesmosomes
how are integrins linked to intracellular intermediate filaments?
linked via an electron dense plaque