W4: Biochem And Physiplpgy Of Connective Tissue

Question 1

What are connective tissues?

Answer 1

Tissues of which the major constituent is extracellular matrix.

Question 2

What is the function of connective tissues?

Answer 2

Mechanical: to maintain cells, tissues, organs in the correct spatial relationships when acted upon by different forces. And support, binding, protection and insulation.

Question 3

What are the 5 types of connective tissue?

Answer 3

Loose, dense, cartilage, mineralised, blood

Question 4

What are the subtypes in loose CT?

Answer 4

Areolar CT, reticular tissue, adipose tissue, mucous tissue

Question 5

Describe areolar CT

Answer 5

Most common, structural support organ, glands, blood vessels, nerves. Fibres loosely arranged in a net or mesh works to bind tissue parts together whilst maintaining movements/flexibility.

Question 6

Describe reticular tissue

Answer 6

Fine stroma matrix/support network, e.g., in bone marrow and spleen

Question 7

Describe adipose tissue

Answer 7

Providing nutrient/energy storage, protection, and insulation

Question 8

Describe mucous tissue

Answer 8

Mostly ‘gel-like’ ground substance, e.g. umbilical cord, dental pulp

Question 9

What is dense CT made of? (Fibrous CT)

Answer 9

Regular closely packed fibrous tissue (collagen fibre bundles running in same direction, fewer cells than loose CT). E.g. tendons and ligaments.
Irregular orientated collagen fibre bundles, e.g. dermis

Question 10

Describe cartilage (as a CT)

Answer 10

Lacks nerve fibres and is a vascular. Support with some pliability.

Question 11

Describe mineralised CT

Answer 11

Calcified cartilage, bone, dentine, cementum. Support and protective role.

Question 12

Describe blood (CT)

Answer 12

Plasma as the ECM

Question 13

Connective tissues of the tooth

Answer 13

Oral mucosa: subepithelium
Periodontal ligament
Alveolar bone of tooth socket
Cementum
Dentine
Dental pulp

Question 14

Cells and extracellular matrix (ECM) of connective tissue

Answer 14

Pic at 9:30

Question 15

Fundamental cell types of CT

Answer 15

• Fibroblasts (secretion of ECM/collagen)
• Cells for specialised matrix production/maintenance: chondrocytes, osteoblasts, osteocyte, odontoblast, cementoblast
• Macrophages, immune cells (plasma cells, leukocytes), melanocytes (pigment cells), adipose cells, mesenchymal cells.

Question 16

Extracellular matrix of CT

Answer 16

• protein fibres (e.g. collagen, elastin) are embedded within a ‘polymeric aqueous gel’ = ‘ground substance’
• ground substance (interfibrillar matrix) consists of proteoglycans, glycoproteins, phospholipids, water

Question 17

How are protein fibres formed?

Answer 17

Protein molecules are synthesised and secreted by fibroblasts into ECM (ground substance). These aggregate into fibres, which provide mechanical strength (collagen) or elasticity (elastin).

Question 18

What is the main fibre type found in most supporting tissues and most abundant protein in human body?

Answer 18

Collagen

Question 19

Function of collagen

Answer 19

Collagen is very strong. Most important function is to provide tensile strength.

Question 20

What is tensile strength?

Answer 20

When something can be bent but is relatively inelastic.

Question 21

How is collagen formed?

Answer 21

Collagen is secreted into the ECM as tropocollagen. Tropocollagen polymerises to form collagen.

Question 22

Collagen composition and properties

Answer 22

High content of few amino acids. 33% glycine. High proline and hydroxyproline content causes a loss of free rotation causing stiffness of the chain. Basic and hydrophilic protein. Cross-linked collagen fibre.

Question 23

How can collagen fibres be arranged?

Answer 23

Compressive loads and tensional loads

Question 24

How can collagen stretch?

Answer 24

Lattice-like arrangement of fibre bundles allow tissues to stretch to some extent. Imparts both strength and flexibility.

Question 25

What are the different collagen types and where are they found?

Answer 25

Type I - in every CT, most common
Type II - cartilage
Type III - reticular fibres, healing wounds, smooth muscle
Type IV - basement membrane (small amounts in bone, dentine)
Type V - tendons (small amounts in bone, dentine, dental pulp)

Question 26

What happens to the collagen fibre with maturation/ageing?

Answer 26

Weak bonds become strong covalent bonds (cross-links). Mechanical strength increases. Becomes more brittle (skin, bone)

Question 27

Structure and properties of elastin

Answer 27

4 polypeptide chains connected by high number of cross-links. Stable, rubber-like elasticity (stretch/recoil). Very insoluble. Lipophilic.

Question 28

What tissues does elastin contribute elasticity to?

Answer 28

Arteries, lungs, skin etc

Question 29

Amino acid residues in elastin

Answer 29

High content of non-polar residues

Low content of polar residues

Question 30

Functions of ground substance

Answer 30

• provides an unstructured extracellular material filling space between cells and fibres
• provides environment for laying down and maturation of protein fibres during tissue development and turnover
• role in mineralisation
• holds water

Question 31

Composition of ground substance

Answer 31

Proteoglycans and glycoproteins

Question 32

Properties of proteoglycans

Answer 32

Unbranded, polysaccharide chains consisting of repeating disaccharide units (glycosaminoglycans). Highly polar. Water binding. Can act as a lubricant (role in dental pulp or attracting and binding water).

Question 33

Describe hyalauronic acid

Answer 33

A proteoglycan. Regulates cell functions. Holds water (synovial fluid: lubricant and shock absorber for cartilage joints; dental pulp; PDL)

Question 34

Structure of glycoproteins

Answer 34

Conjugated proteins with one or more short irregular hetero/oligosaccharide side chains bound to a polypeptide chain. Often integrated in cell membrane.

Question 35

Main functions of glycoproteins.

Answer 35

Cell adhesion, migration, mineralisation