Connective Tissue BSM

Question 1

How many types of tissue are there? Name the different types of tissues?

Answer 1

. 4 Types of Tissue
. Epithelial Tissue, Connective Tissue, Nervous Tissue and Muscle Tissue

Question 2

Extracellular matrix facts

Answer 2

. Made up of proteins in the form of fibres
. Ground Substance
. Cells

Question 3

What does connective tissue develop from?

Answer 3

. The mesenchyme -> comes from mesoderm layer of the embryo -> mesenchyme contains stem cells which can differentiate into different cells that make up connective tissue. So mesenchyme is a type of embryonic connective tissue.

Question 4

Name the 3 layers in the embryo?

Answer 4

. Ectoderm, mesoderm and endoderm
. These layers give rise to all the organs in the body

Question 5

Connective Tissue Proper - divisions and subdivisions

Answer 5

. Divided as loose and dense connective tissue
. Loose CT = areolar tissue, adipose (fat) tissue and reticular tissue
. Dense CT = further subdivided into dense regular & dense irregular connective tissue

Question 6

Specialised Connective Tissue

Answer 6

. Includes bone and carilage - these are supportive connective tissue
. Blood - the fluid connective tissue

Question 7

3 fundamental components of connective tissue

Answer 7

. Cells, protein fibres and ground substance - (cells, gels and fibres)

Question 8

Cells of Connective Tissue

Answer 8

. Specialised CT - like cartilage = chondrocytes, Bone = osteoblasts, osteocytes, adipocytes = adipose tissue
In general, CT = 2 groups of cells
1. Permanent Resident Cells
2. Transient Cells

Question 9

Transient Cells

Answer 9

. Usually immune cells like macrophages, neutrophils, eosinophils, plasma cells, mast cells
- macrophages = phagocytic scavengers - different names depending on location; (dust cells in lungs, kupffer cells in liver & langerhan cells in skin - but these macrophages are fixed so they are actually permanent residents)
- wandering macrophages = ones that move around = tranisent cells

Question 10

Brief overview of Neutrophils, Eosinophils, Plasma cells and Mast Cells

Answer 10

Neutrophils = involved in ACUTE INFLAMMATION
Eosinophils = allergic reactions, parasitic infections
Plasma cells = differentiated B-lymphocytes , produce antibodies
Mast cells = granulated, involved in inflammation in hypersensitivty disorders, degranulate to release inflammatory mediators

Question 11

Permanent Resident Cells

Answer 11

. Most common cells in CT = permanent resident cells
. Depending on certain circumstances some immune cells like mast cells and macrophages can be permanent residents
. Stem cells - give rise to all the other cell types
. Fibroblast = most common cells
. Fibrocyte = second most common cell
. Fibroblast and Fibrocyte are related

Question 12

Fibroblast function

Answer 12

. Synthesising the proteins listed below:
. Protein fibres - collagen, reticulun and elastin
. Ground substance - Glycosaminoglycans (GAG), proteoglycans, adhesive glycoproteins

Question 13

Name some protein fibres and ground sunstances in CT

Answer 13

. Protein fibres - collagen, reticulun and elastin
. Ground substance - Glycosaminoglycans (GAG), proteoglycans, adhesive glycoproteins
. The aforementioned are all proteins and are syntheised by fibroblasts

Question 14

Compare & contrast the ultrastructure of fibroblasts and fibrocytes

Answer 14

. Fibroblasts structure relates to function
. Because fibroblasts synthesise alot of protein
. Ultrastructure =
. RER
. Mitochondrion
. Golgi Appartus
. Fibrocytes:
- More mature cell, spindle shaped,

Question 15

Name 3 of the protein fibres found in CT

Answer 15

. Collagen
. Reticulun
. Elastin
. Distributed in different proportions depending upon what part of the body they are in

Question 16

Elaborate on protein fibres

Answer 16

Collagen = most abundant of the 3 protein fibres - found in skin, bone, tendon, cartilage
. Important for tensile strength and support
Reticulun = Type of collagen, specifically type three collagen
organs like spleen, bone marrow, lymph nodes have reticular tissue, forms a fine meshwork in organs, important for structural support
. Elastin = elastic = stretchy -> elasticity = stretch and return to original shape -> needed in the lungs, elastic arteries, elastic ligaments and also in the skin

Question 17

Ground substance of the CT

Answer 17

. Ground substance = made up of cabohydrates and proteins and they bind to water
. Includes glycosaminoglycans, (GAG) proteoglycans and adhesive glycoproteins

Question 18

Proteoglycans - structure

Answer 18

. Structure -
proteoglycan monomer = protein core & glycosaminoglycan side chains -> the GAG side chains are sulfated
. proteoglycan megacomplex = many proteoglycan monomers attaching to hyaluronic acid via link proteins

Question 19

Adhesive glycoproteins

Answer 19

. Are adhesive - so they connect stuff
. for example, fibronectin = connects cells to protein fibres, so adhesive glycoproteins act like an adhesive between the different components of connective tissue
Ground subustance = well hydrated
GAGs, proteoglycans and adhesive glycoproteins for the ground substance
fluid which is in the ground substance forms the interstitial fluid which is present outside the cells. So interstitial fluid is part of the ECF and Starling forces are the forces which guide the exchange across the capillary membrane.

Question 20

Characteristics of loose connective tissue

Answer 20

. Areolar Tissue is loose connective tissue
Characteristics:
- Lesser cells, more ground substance
- CT fibres are loosely arranged
- example lamina propria - situated beneath the epithelial lining of lots of organs + also the capsule around organs
Function - flexible, not very resistant to stress

Question 21

Characteristics of Dense CT

Answer 21

. More fibres, lesser ground substance
. Can be further split into regular or irregular
. Dense irregular CT - randomly oriented fibres - e.g. found in the deep dermis of the skin - can handle stress and forces that are acting in different directions due to the random orientation of fibres - collagen fibres = give them tensile strength
. Dense regular CT = more organised, parallel bundles of fibres like e.g. in the tendon, due to fibres being in a parallel arrangement they can handle stress going in a single direction
. Histology - between the fibres = see fiborblasts (because fibroblasts synthesise the fibres)

Question 22

CT Quick Review

Answer 22

. CT = tissue that supports other tissue
. It anchors, binds and connects cells, tissues & organs
. Depending on its location, its got cells and an ECM
. ECM = ground substance embedded with protein fibres
. So Connective tissue = cells, fibres & ground substance
. Fibres = made up of proteins & there are 3 main types:
. Collagen - most abundant + also most abundant protein in the body, important for tensile strength & support
. Reticulun - thin, mostly made of Type 3 collagen
. Elastin - stretchy, is elastic - so can stretch and return to its original shape
. These 3 fibres are distributed differently depending on the type of tissue, where it is located and whats its function is

Question 23

Collagen
- Main function & the key types

Answer 23

Main function = strength & support
Many types of collagen but most collagen belongs to type 1 to 4

Question 24

What is the most abundant type of collagen?

Answer 24

. Type 1

Question 25

Where is type 1 collagen found?

Answer 25

. Bone, tendon & dermis of the skin

Question 26

What type of collagen does cartilage have? & what other areas (if any) have this type of collagen

Answer 26

Type 2
. Vitreous humour of the eye
& the nucleus pulposus of the intervertebral discs

Question 27

What type of collagen is in reticular fibres?

Answer 27

. Reticular fibres - fine & more delicate
. Found in organs which form part of the reticuloendothelial system - CT of the spleen, the liver, lymph nodes & bone marrow -> have reticular fibres & it forms reticular CT
. Stains black with particular stains - histology

Question 28

What does type 4 collagen do?

Answer 28

. Forms the floor of the epithelial cells -i.e. the basement membrane (basal lamina)
. Also found in the lens of the eye

Question 29

What types of collagen form fibrils?

Answer 29

Type 1, 2 and 3 -> thus called fibril forming collagen

Question 30

What does type 4 collagen form?

Answer 30

. Networks/Sheets

Question 31

Collagen

Answer 31

. Is a protein made up of 3 polypeptide chains; 3 alpha chains, triple helix structure
. Amino acis sequence - triple repeating sequence
. X - Y - Glycine
. X & Y = any amino acid but usually proline & hydroxyproline
. Fibroblasts = protein synthesis
. Fibroblasts = synthesise the proteins that then form the fibres & the ground substance

Question 32

Collagen Synthesis

Answer 32

. Initial step of synthesis = similar to any protein synthesis -i.e. transcription & translation
. Transcription occurs - DNA is transcribed & translated to produce a polypeptide chain with a leader sequence called a signal peptide -> this is PREPROCOLLAGEN
. The signal peptide guides the peptide chain into the cisternae of the RER, now enzymes remove the peptide sequence -> Voila, we have PROCOLLAGEN
RER = procollagen goes alot of post-translational modification

Question 33

What breaks down collagen?

Answer 33

Collagenases - these are matrix metalloproteinases which break down the collagen into protein components

Question 34

Elastin

Answer 34

Function - more for elasticity - stretch & return to its original shape
Location - lungs, elastic arteries, elastic ligaments & dermis of the skin -> reason why pinched skin returns to its original state is that there are elastin fibres in the dermis

Question 35

Outline the synthesis of elastin

Answer 35

Synthesised in fibroblasts
Precursor = Tropoelastin - which eventually forms elastin
elastin deposits on microfibrils which form a scaffold
. These microfibrils = made up of fibrillins & there are three types mostly type 1
Clinical Relevance
. Gene defect for Fibrillin Type 1 can result in Marfan’s Syndrome
. Elastin UNLIKE collagen does not have a triple helical structure + does not have a repeating sequence of amino acids

Question 36

What is the enzyme that breaks down elastin and what does it break elastin into?

Answer 36

. Enzyme = elastases