Lecture 11 Flashcards
3 ways we classify epithelium
- morphological (shape,layers)
- surface specialisations (cilia, microvilli)
- surface (covering) or glandular (secretory)
Where would you find stratified squamous epithelium and why?
Protective
- epidermis
- oesophageal
What is an example of metaplasia
- reversible transition from one cell type to another
E.g columnar epithelium in oesophagus due to gastric reflux
What do connective tissues provide?
- general structure
- physical and metabolic support for more specialised tissues
- mechanical strength
- fills spaces in the body
Three key properties of connective tissue and what component provides this.
• Tensile strength
• collagen
• Elasticity
• elastin
• Volume
• ground substance
4 types of connective tissue
• Connective tissue proper
• Cartilage
• Bone
• Blood
Collegen esists..
Tension
Two types of connective tissue proper
Loose
Dense
Structure of loose connective tissue proper
Open, loose structure
(Open species are filled with ground substance)
Features of AREOLA loose connective tissue proper
- strong yet cousinionig
- underlies epithelium, forms laminated propria (network of connective tissue, collagen, elastin for support)
Features of RETICULAR loose connective tissue proper
- reticular fibres (supportive mesh)
- supports organs - forms supportive scaffolding around them
- network structure - branches a lot
- made of specialsied collagen fibres
Features of ADIPOSE loose connective tissue
- sometimes classified seperately
- adipocytes
- white: stores energy
- brown: thermoregulation
Which has a greater proportion of fibres, dense of loose connective tissue proper
Dense
Two types of dense connective tissue proper
- regular
- irregular
Difference between regular and irregular dense connective tissue proper
Regular: parallel fibres (mainly type 1 collagen)
- e.g ligaments, tendons
Irregular: non-parallel fibres
- e.g in dermis
Both are tightly packed
Where loose and dense connective tissue proper is found
Three types of cartilage
- hyaline
- fibrocartilage
- elastic
Features of hyaline cartilage
- smooth, translucent
- few collagen fibres
- ends of bones, tracheal rings
Features of fibrocartilage
- many collagen fibres
- e.g cartilaginous joints, menisci of knee joint
-absorbing shock
Features of elastic cartilage
- elastin and collagen fibres
- e.g ear
Features of bone matrix
Collagen in extracellular matrix (Tension)
But also becomes calcified (compression)
Two layouts of bone
- compact
- cancellous, forming the trabeculae
- spreads out the force
What does the layout of the bone depend on
- the stress/weightbearing nature of the bone
Two key components of connective tissue
- cells
- ECM
What determines the properties of the tissue?
The constituents of the ECM
What do support cells do?
- give rise to the support tissue??> yap
- produce the ECM components
Where are support cells derived from?
Embryologival tissue mesenchyme
What do osteoblasts create
Bone
What do chondroblasts create
Cartilage
What do fibroblasts create?
Connective tissue proper
Mature connective tissue has predominant ___ with sparse ____ ______
ECM
Cellular component
______ characteristics are crucial to _______ performed by tissue
Matrix
Functions
Class of connective tissue and the resulting matrix components and general function
Different tissue = different
Matrix
Loose areola CT v dense irregular CT extracellular matrix
Support cells secrete…
ECM
Characteristics of ECM crucial to
Fuctnion of tissue
Do cells of connective tissue prefer to adhere to extracellular materials or other cells
ECM materials
3 main components of ECM
- ground substance
- fibrillar proteins
- adhesion proteins
What does ground substance do?
Binds to water, salts, collagen proteins, other modules to make a massive matrix structure
Two main components of ground substance
• Glycosaminoglycans (GAGs) – very long unbranching polysaccharides (sugars)
• Proteogylcans – proteins that covalently bond to GAGs
What do fibrillar proteins do in the ECM
- proteins that make fibres
- fibres provide strength or elasticity
What do adhesion proteins in the ECM do?
- link fibres, ground substance and cells together
What are Glycosaminoglycans (GAGS)
• Long unbranched polysaccharide chains
What is the most common GAG? What is their structure?)
• Hyaluronic acid (hyaluronate) most common GAG
• Long linear molecules of two repeating sugar molecules
Other GAGS (dermatan sulphate) attach via hyaluronic acid via core proteins (forming proteoglycans)
THEY HAVE A NEGATIVE CHARGE MAKING THEM HYDROPHILLIC - makes them very attractive to water - easy to bind - water good at resisting compression - good to trap in place
What do Pr oteoglycans and Glycosaminoglycans
Do?
• Form the ground substance • volume and compression resistance
What do Pr oteoglycans and Glycosaminoglycans interact with?
• each other
• with water and salts
• collagen
• and other fibres and molecules.
What do fibrillar proteins do - what components allow them to do this?
Add strength/ elasticity to tissue
- collagen
- forms fibrils, fibres and sheets, gives tenasile strength
- many types of
- elastin
- forms fibres or sheets, allows stretching and elastic recoil
Features of collages
- must abundant protein in the human body
- found in most support tissues
- secreted by fibroblasts
- stains pink in H and E
Structure of collages
- a series of twisted protein fibres
• Fibres are banded under the electron microscope due to the
different overlap between the triple helices
What differs the collagen types
Amino acid composition, produced by different genes
How many different types of collagen
28
What the different types of collagen make up which structures
• Type I: ~90% of collagen in body. Makes up ligaments,
tendons, bone, skin
• Type II: cartilage
• Type III: reticular tissue (forms reticular fibres)
• Type IV: basement membrane
Diseases due to to collagen defects
Osteogenesis Imperfecta
Ehlers-Danlos syndromes
What is elastin produced by?
Fibroblasts
Where is elastin abundant
blood vessels, skin, lungs, elastic cartilage
Structure of elastin
• Elastin protein comprised of short-segments
• Covalently bound to each other, to allow stretching and relaxation
What do adhesion proteins (glycoproteins) do?
• Mediate interactions between cell cytoskeleton and extracellular matrix
Two examples of adhesion proteins
- fibronectin
- laminin
Features of fibronectin
• Dimeric glycoprotein
• Binds collagen, proteoglygans and cells
• Binds collagen to integrins on cell surface \
Adhesion protein
Features of laminin
• Binds multiple components of the ECM
• Form sheets that make up basement membrane
• Binds cells to basement membranes
• Binds to integrins
Adhesion protein
Junctions between cells and ECM are important in maintaining structural integrity, what are some examples of cell-matrix adhesion mechanisms
• Focal adhesions
• Bind cells to the extra cellular matrix
• Hemidesmosomes
• Attach epithelial cells to basement membrane
• Intregrin proteins are important in both types of junction
What attaches cells to ECM?
Support cells
How do facial adhesions attach cells to ECM
Integrin molecules interact with other proteins on both sides of the lipid bilayer
What are Hemidesmosomes
• Modified desmosomes
Where are hemidesmosomes
• Basal surface of cell
What do hemidesmosomes do?
Anchor to basement membrane
• Bind to cytokeratin
What is hemidesmosomes main transmembrane protein?
• Main transmembrane protein
• integrins
How do cells anchor to basement membrane?
Integrins bound through to collagen fibres
What are intentions linked too
• intracellular
intermediate
filaments
(cytokeratin) via an
electron dense
plaque
• the basement
membrane by
anchoring to
filaments composed
of laminin
How do hemidesmosomes and inegrins relate?!?!?!
KNOW THIS
Know that linkage between the integrity and the strucutres of the basement membrane
Know the differnce between how cells anschor ECM with focal adhesions vs how hemidesmosomes anchor epithelial cells
