- compact - cancellous, forming the trabeculae - spreads out the force

Lecture 11 Flashcards by Becky Ross

3 ways we classify epithelium

morphological (shape,layers)
surface specialisations (cilia, microvilli)
surface (covering) or glandular (secretory)

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Where would you find stratified squamous epithelium and why?

Protective
- epidermis
- oesophageal

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What is an example of metaplasia

reversible transition from one cell type to another
E.g columnar epithelium in oesophagus due to gastric reflux

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What do connective tissues provide?

general structure
physical and metabolic support for more specialised tissues
mechanical strength
fills spaces in the body

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Three key properties of connective tissue and what component provides this.

• Tensile strength
• collagen
• Elasticity
• elastin
• Volume
• ground substance

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4 types of connective tissue

• Connective tissue proper
• Cartilage
• Bone
• Blood

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Collegen esists..

Tension

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Two types of connective tissue proper

Loose
Dense

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Structure of loose connective tissue proper

Open, loose structure
(Open species are filled with ground substance)

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Features of AREOLA loose connective tissue proper

strong yet cousinionig
underlies epithelium, forms laminated propria (network of connective tissue, collagen, elastin for support)

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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

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Features of ADIPOSE loose connective tissue

sometimes classified seperately
adipocytes
white: stores energy
brown: thermoregulation

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Which has a greater proportion of fibres, dense of loose connective tissue proper

Dense

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Two types of dense connective tissue proper

regular
irregular

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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

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Where loose and dense connective tissue proper is found

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Three types of cartilage

hyaline
fibrocartilage
elastic

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Features of hyaline cartilage

smooth, translucent
few collagen fibres
ends of bones, tracheal rings

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Features of fibrocartilage

many collagen fibres
e.g cartilaginous joints, menisci of knee joint
-absorbing shock

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Features of elastic cartilage

elastin and collagen fibres
e.g ear

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Features of bone matrix

Collagen in extracellular matrix (Tension)
But also becomes calcified (compression)

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Two layouts of bone

compact
cancellous, forming the trabeculae
spreads out the force

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What does the layout of the bone depend on

the stress/weightbearing nature of the bone

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Two key components of connective tissue

cells
ECM

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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

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