Histology

Question 1

How are muscle fibres grouped?

Answer 1

Into bundles called fascicles

Question 2

What is the connective tissue called which surrounds:

a) the muscle fibre as a whole
b) the connective tissue around a single fascicle?
c) the connective tissue around a single muscle fibre?

Answer 2

a) Epimysium
b) Perimysium
c) Endomysium

Question 3

What is a motor unit?

Answer 3

One motor neurone and all the muscle fibres that it innervates (anywhere from a few to more than a hundred)

Question 4

How are the fibres arranged in a motor unit?

Answer 4

Are all scattered in the muscle (not bunched together) and are all the same fibre type

Question 5

Describe the features of a Type I skeletal muscle type

Answer 5

• Slow contracting fibres
• Depend on oxidative metabolism
• Abundant mitochondria
• Resistant to fatigue
• Produce relatively little force
• ‘red’ fibres

Question 6

Describe the features of a Type IIA skeletal muscle type

Answer 6

• Intermediate between type I and type IIA
• Relatively fast contracting, but also reasonably resistant to fatigue
• These fibres are relatively uncommon

Question 7

Describe the features of Type IIB

Answer 7

• Fast contracting fibres
• Depend on anaerobic metabolism
• Few mitochondria
• Fatigue relatively easily
• Produce relatively greater force
• ‘white fibres’

Question 8

What are the differences between bone and cartilage?

Answer 8

Cartilage: semi-rigid and deformable, permeable, avascular, cells nourished by diffusion through extracellular matrix

Bone: Rigid, Not permeable, cells within the bone must be nourished by blood vessels that pervade the tissue

Question 9

What are Chondrocytes?

Answer 9

• Live within a space in the extracellular matrix termed a lacuna
• They are active cells which not only secrete, but also maintain the extracellular matrix around them

Question 10

What is the difference between type I and Type II collagen?

Answer 10

Type I: linear bundles

Type II: forms a 3-meshwork

Question 11

Where is type I collagen found?

Answer 11

Skin, tendon,bone, organs

Question 12

Where is type II collagen found?

Answer 12

Cartilage

Question 13

Name the three types of cartilage

Answer 13

Hyaline, Elastic and Fibrocartilage

Question 14

Describe Hyaline cartilage

Answer 14

Blue-white in colour and translucent

Most common form of cartilage

Question 15

Describe Elastic Cartilage

Answer 15

Light yellow in colour, addition of elastic fibres makes it quite flexible

Question 16

Describe Fibrocartilage

Answer 16

• Hybrid between tendon and hyaline cartilage
• Bands of densely packed type I collagen, interweaved with rows of chrondrocytes
• Appears white

Question 17

Name some site where Hyaline cartilage can be found

Answer 17

Articular surfaces, Tracheal rings, Costal cartilage, Epiphyseal growth plates

Question 18

What are the main functions of bone?

Answer 18

Support, levers for effective movement, protection of internal organs, calcium store, haemopoiesis (blood cell production)

Question 19

What are the two types of bone which can be seen in a longitudinal section through a long bone?

Answer 19

Cancellous and Cortical

Question 20

Which bone occupies the shaft of a long bone?

Answer 20

Cortical

Question 21

Which bone occupies the ends of the bone?

Answer 21

Cancellous or Trabecular

Question 22

What are ‘cement lines’

Answer 22

The lines that are often visible surrounding the osteon

Question 23

What are osteoprogenitor cells?

Answer 23

Located on bone surfaces for example under the periosteum, these cells serve as a pool of reserve osteoblasts

Question 24

What are osteoblasts?

Answer 24

Bone forming cells found on the surface of developing bone. They have plentiful RER and prominent mitochondria

Question 25

What are osteocytes?

Answer 25

A bone cell trapped within the bone matrix

Question 26

What are osteoclasts?

Answer 26

large multinucleate cells. They are found on the surface of bone and are responsible for bone resorption.

Question 27

How does bone remodelling occur?

Answer 27

A number of osteoblast will congregate and begin to 'drill' into the bone, forming a tunnel. A blood vessel will grow into the tunnel and begin laying down new lamellar bone. This process continues until only the space of a Haversian canal remains

Question 28

What is osteoid?

Answer 28

Osteoblast secrete collagen, glycosaminoglycans, proteoglycans and other organic components of the matrix which is collectively termed osteoid. This becomes mineralised over time in the extracellular space.

Question 29

What is Woven bone?

Answer 29

The deposition of collagen fibres is not orientated in a single direction-haphazard fashion- during development or after an injury. This bone is not as strong and is subsequently remodelled into lamellar bone by being broken down by osetoclasts and reformed by new osteoblasts.