Connective Tissue

Question 0

Give some examples of the functions of connective tissue.

Answer 0

• provides substance and form to body/organs
• medium for diffusion of nutrients/waste products
• attaches muscle to bone (tendon) and bone to bone (ligaments)
• cushion between tissues/organs
• defence against infection
• aids injury repair

Question 1

Define connective tissue.

Answer 1

Continuum throughout the body linking muscle, nerve, and epithelial tissue in a structural way whilst providing support in a metabolic and physiological way.

Question 2

What are the components of connective tissue?

Answer 2

CELLS & EXTRACELLULAR MATRIX

Extracellular matrix = GROUND SUBSTANCE + FIBRES (collagen, reticular, or elastic)

Question 3

What does ground substance do, and what is it composed of?

Answer 3

Provides route for communication/transport between cells (by diffusion).
GLYCOSAMINOGLYCAN + PROTEOGLYCAN MONOMERS
e.g. hyaluronate proteoglycan aggregate
Negative charges on GAGs attract water -> forms hydrated gel

Question 4

What are some significant examples of highly modified ground substance?

Answer 4

PLASMA (blood): gs lacks stabilising macromolecules (free-flowing)
BONE: gs has been mineralised by calcium deposits (rigid)
CARTILAGE: gs more solid, but still resilient

Question 5

What is the structure and function of collagen?

Answer 5

Triple alpha-helix (Gly-X-Y repeating sequence) with H-bonds between alpha chains, and cross-links between molecules to form fibrils, and between fibrils to form fibres.

Confers tensile strength to connective tissue

Question 6

What is a fibrous capsule?

Answer 6

Fibrous connective tissue surrounding an organ/tissue acting as a barrier
e.g. capsule around lymph node prevents lymph diffusing out into the surrounding tissues, and also prevents lymph infections

Question 7

What is the function of reticular fibres?

Answer 7

Reticular fibres (reticulin) = type of collagen that cross-links to form a delicate supporting framework for loose cells in soft tissues.

Question 8

What is the function of elastic fibres?

Answer 8

Elastic fibres (elastin enfolding fibrillin molecules) = restores normal shape after distortion

Question 9

What are the types of connective tissue and how do they differ?

Answer 9

LOOSE = few fibres, lots of ECF
DENSE IRREGULAR = lots of fibres orientated in multiple directions (resists forces in different directions, therefore prevents tearing)
DENSE REGULAR = lots of fibres running parallel (in line with tensile force exerted by muscle)

Question 10

Give some examples of loose connective tissue.

Answer 10

Lamina propria (mucosa)
Submucosa (COLON)
Mesentery (serosa)			
Blood vessels 
Nerves

Question 11

Give some examples of dense irregular connective tissue.

Answer 11

Dermis
Submucosa (?)
PERIOSTEUM = membrane covering bone surface
PERICHONDRIUM = membrane surrounding cartilage

Question 12

Give some examples of dense regular connective tissue.

Answer 12

Tendons = join muscle to bone

Ligaments = join bone to bone

Question 13

What is the function and location of fibroblasts?

Answer 13

Secretes fibres e.g. procollagen, reticulin, elastin, and ground substance.
Important for healing and scar formation.
Most common cell found in connective tissue.

Question 14

What is a trabecula?

Answer 14

Column of connective tissue extending from capsule into tissue.

Divides glands into lobules

Question 15

Explain how different types of connective tissue are of embryonic origin.

Answer 15

EMBRYONIC CONNECTIVE TISSUE = mucous connective tissue (umbilical cord) + MESENCHYME (multipotent cells of mesodermal origin).

The mesenchyme can differentiate to form cells involved in synthesising connective tissue (fundamentally fibroblasts, but also chondroblasts -> cartilage, osteoblasts -> bone, and lipoblasts -> adipose)

Question 16

What is the function of macrophages?

Answer 16

Blood monocytes -> macrophages —> connective tissue (esp. during inflammation).

Phagocytic (degrades cell debris/foreign bodies by forming a phagolysosome)

Present foreign material to T lymphocytes e.g. bacteria (immune response activated).

Question 17

What is the function of mast cells?

Answer 17

Abundant in cytoplasm as granules. Present in connective tissues near blood vessels (but ABSENT from CNS -> prevent oedema in brain).

Secrete heparin (anticoagulant), histamine (increase blood vessel wall permeability), and chemoattractants for eosinophils and neutrophils.

Allergen binding to IgE receptors on surface -> releases contents -> hypersensitivity -> allergy/anaphylaxis

Question 18

Give some examples of specialised connective tissue.

Answer 18

• ADIPOSE TISSUE
• BLOOD = plasma + haemopoietic tissue (blood cellular components)
• CARTILAGE
• BONE
• LYMPHATIC TISSUE

Question 19

Explain the differences in structure and function between types of adipose tissue.

Answer 19

ADIPOCYTES -> LIPOBLASTS -> lipid droplets in cytoplasm of fat cells.
Lipid droplets remain separate = brown adipose tissue (multilocular)
Lipid droplets combine = white adipose tissue (unilocular)

Both are fuel reserves, and act as insulators/shock absorbers.

Brown adipose is also involved in non-shivering thermogenesis (uncoupling of oxidative phosphorylation to release heat energy).

Question 20

What are the clinical features of Marfan’s syndrome?

Answer 20

Autosomal dominant
Mutant fibrillin gene -> deformed elastin fibres
Arachnodactyly (long fingers), tall, wing span>height, high arched palate.
Mitral valve disorders.
Risk of aortic dissection.

Question 21

What are the clinical features of Ehlers-Danlos syndrome?

Answer 21

Autosomal dominant 
Defect in collagen (type can determine severity) -> abnormal cross-linking between fibrils 
Hypermobile joints (frequent dislocations), fragile blood vessels, hyperelastic skin, heart valve problems.