Connective Tissues

Question 1

What are connective tissues ?

Answer 1

Tissues with cells embedded in an extensive extracellular matrix

Question 2

What is the function of the connective tissues ?

Answer 2

• mechanical function
• support
• wrapping and binding
• packing and space filling
• wound healing
• infection control

Question 3

What are the general features of connective tissues ?

Answer 3

• relatively few cells
• lots of extracellular matrix

Question 4

What is the composition of the extracelular matrix ?

Answer 4

There are fibres embedded in ground substances

The fibres are -
• collagen (high tensile strength - don’t stretch or branch)
• elastic fibres (stretch and then recoil - branched)

The ground substance is glycosaminoglycans and proteoglycans (complex sugars)

Question 5

What is the function of the complex sugars in the ECM ?

Answer 5

They are highly charged and so attract water into the matrix
- swelling pressure
- forms a jelly
- compression resistance
- diffusion of nutrients

Question 6

What is the role of connective tissue cells ?

Answer 6

• make the matrix
• sense loading on the matrix
• modify the matrix according to load

Question 7

What are the types of connective tissue ?

Answer 7

• connective tissue proper
• cartilage
• bone

Question 8

What are the different types of connective tissue proper ?

Answer 8

There are 5-6 different types -
1) loose connective tissue
2) dense fibrous connective tissue
• regular
• irregular
3) adipose tissue
• white - storage fat
• brown - also storage fat but can’t turn the stored fat into ATP
4) reticular connective tissue
5) pigmented connective tissue - found in sclera of eye
6) blood

Question 9

What are the different cells of the loose connective tissue ?

Answer 9

Resident cells :
- fibroblasts
- fat cells
- mast cells
- endothelial cells

Immigrant cells :
- monocytes (in blood) > macrophages (outside of blood)
- lymphocytes > plasma cells

Question 10

Summarise the role of fibroblasts

Answer 10

• make the ECM
• it is not possible to tell the difference between active and inactive fibroblasts

Question 11

Summarise the role of fat cells

Answer 11

Used for storage, cushioning and space filling

Question 12

Summarise the role of mast cells

Answer 12

They contain secretory vesicles (granules) which contain histamine and heparin

Question 13

Describe the dense fibrous connective tissue

Answer 13

The matrix is dominated by collagen fibres
They can highly organised - regular e.g. tendons and ligaments
They can be random - irregular e.g. the dermis

Question 14

What is the role of reticular connective tissue ?

Answer 14

It is used for the network and organisation of cells

Question 15

What is cartilage ?

Answer 15

A skeletal connective tissue
It is avascular and aneural

Question 16

What are the 3 types of cartilage ?

Answer 16

• hyaline cartilage
• fibrocartilage
• elastic cartilage

Question 17

Summarise hyaline cartilage

Answer 17

• it occurs on the surface of all joints except the TMJ and in the foetal skeleton and tracheal rings
• it has an outer fibrous layer known as perichondrium
• the cells within it are known as chondrocytes and they sit within a hole known as a lacuna

Question 18

Summarise fibrocartilage

Answer 18

• It is an intermediate between hyaline cartilage and dense fibrous connective tissue
• It has a high glycosaminoglycan content
• The TMJ is made of fibrocartilage

Question 19

Summarise elastic cartilage

Answer 19

It is similar to the hyaline cartilage but with lots of elastic fibres in the matrix
E.g. pinna of the ear

Question 20

What is bone ?

Answer 20

• Bone is a type of connective tissue made of osteocytes which are embedded in calcified matrix
• It is used for support, movement and protection
• 2/3 is inorganic and made of calcium hydroxyapatite
• 1/3 is organic and is made up of 90% collagen and 10% other

Question 21

Describe the different bone cells and their roles

Answer 21

• osteocytes are derived from osteoblasts and they are the cells that make up the bone
• osteoblasts sit on top of the surface of the bone and make new bone
• osteoclasts remove bone

Question 22

Why does the skin have irregular dense fibrous connective tissue ?

Answer 22

It provides tension resistance

Question 23

Why do tendons and ligaments have regular dense fibrous connective tissue ?

Answer 23

High tensile strength is needed to transfer muscle contraction force

Question 24

Describe the structure of bone

Answer 24

• compact on the outside and spongy in the middle
• contains bone marrow
• highly vascular and innervated