Histology Of Soft Connective Tissue

Question 1

What does soft connective tissue generally comprise of?

Answer 1

Cells embedded in abundant extracellular matrix

Question 2

What is the most abundant cell in soft connective tissue?

Answer 2

Fibroblasts

Question 3

What are the functions of soft connective tissue? (5)

Answer 3

Space filler + protection

Attachment + mechanical support

Highway for nutrient diffusion

Storage of fat and calcium

Site of immunological defence

Question 4

What are the five main types of soft connective tissue?

Answer 4

Mesenchyme (embryonic)

Loose/areolar (mesentery, under dermis)

Dense (tendons, dermis, organ capsules)

Reticular (bone marrow, lymph nodes)

Adipose (fat)

Question 5

What does the extracellular matrix consist of?

Answer 5

Proteins (mainly glycoproteins)

Glycosaminoglycans (GAGs)

Question 6

What synthesises and secretes the major proteins of a general extracellular matrix?

Answer 6

Fibroblasts

Question 7

What is the function of collagen in the ECM?

Answer 7

Tensile strength

Question 8

What is the structure of collagen?

Answer 8

Rod-shaped triple helix of polypeptides

Highly ordered inextensible fibres

Question 9

How long can one collagen fibril be?

Answer 9

420nm

Question 10

Where is type I collagen found?

Answer 10

Skin

Bone

Tendons

Dentin

Question 11

Where is type II collagen found?

Answer 11

Cartilage

Question 12

Where is type III collagen found?

Answer 12

Blood vessels

Skin

Question 13

Where is type IV collagen found?

Answer 13

Basement membrane (sheet collagen)

Question 14

What makes up elastic fibres?

Answer 14

Network of microfibrils of fibrillin with a core of cross-linked elastin

Question 15

How are elastin molecules held together?

Answer 15

Covalent bonds

Question 16

How does the structure/arrangement of elastin molecules change from relaxed to stretched?

Answer 16

Relaxed - random structure

Stretched/deformed - pulled apart to a wider arrangement as it stores energy to recoil

Question 17

Where is the greatest density of elastic fibres and why?

Answer 17

Aorta

Highest pressure

Question 18

How many cycles of stretch-recoil can an elastic fibre withstand before losing elasticity?

Answer 18

Over 2 billion

Question 19

What part of the cytoskeleton is associated with integrins?

Answer 19

Actin

Question 20

What are the major ECM proteins for cell binding?

Answer 20

Fibronectin + collagens

Tenascin (sounds)

Laminin (attaches epithelia to basal lamina)

Question 21

What is another word for glycosaminoglycans?

Answer 21

Mucopolysaccharides

Question 22

Which GAG is not synthesised as a proteoglycan?

Answer 22

Hyaluron

Question 23

What is the structure of a GAG?

Answer 23

70-200 unit polymers formed from a repeating disaccharide subunit

Question 24

What causes GAGs to have such a large volume?

Answer 24

SO3- and COO- groups
High density of negative charge
Attracts lots of water so very hydrated

Sugar chains too stiff to fold into compact structures (negative charges repel)

Question 25

What allows the ECM to withstand compressive pressure?

Answer 25

Turgor created by water (hydrated GAGs)

Question 26

How much of the ECM mass is GAGs?

Answer 26

<10%

Question 27

What are the three indigenous cells of the soft connective tissue? What are their functions?

Answer 27

Fibroblasts (produce ECM elements) Adipocytes (fat storage and leptin secretion) Mast cells (histamine secretion)

Question 28

What forms most of the indigenous cells of soft connective tissue? Which is the exception?

Answer 28

Mesenchymal stem cells Mast cells

Question 29

What are the immigrant cells of soft connective tissue? (6)

Answer 29

(Immune system cells) Lymphocytes Neutrophils Monocytes/macrophages Dendritic cells Eosinophils Basophils