Bones first lecture

Question 1

Describe the structure of long bone

Answer 1

• Epiphysis (head) - articular surface and covered by hyaline cartilage
• Metaphysis - between epiphysis and diaphysis (region of growth in childhood)
• Diaphysis (shaft) - hollow cylinder and contains bone marrow in marrow cavity
• Periosteum - fibrous connective tissue sheath covering external surfaces

Question 2

What is the function of bone

Answer 2

• Enable movement
• Protect vital organs
• Structural support

Question 3

What is trabecular/cancellous bone

Answer 3

It is spongy and porous. Gives supporting strength to the ends of the weight-bearing bone. Weaker and more flexible than compact bone

Question 4

What is cortical bone

Answer 4

It is solid. Bone on the outside forms the shaft of the long bone. Provides stiffness and strength. The cells are arranged like an onion. Collagen fibres in each layer oriented differently

Question 5

What is the function of haversian canals

Answer 5

They carry blood along the long axis of the bone

Question 6

What is the function of volkman’s canals

Answer 6

They carry blood perpendicularly

Question 7

What is the function of an osteoblast

Answer 7

It is a bone forming cell, depositing collagen then hydroxyapatite. They cover the surface of bone, forming an osseous matrix in which it becomes enclosed as an osteocyte

Question 8

What is the function of an osteoclast

Answer 8

In response to mechanical stresses and physiological demands they resorb bone matrix by dimineralization using H+ and hydrolytic enzymes

Question 9

What is the function of an osteocyte

Answer 9

They are retired osteoblasts. They maintain bone matrix through cell-to-cell communication and influence bone remodelling

Question 10

Describe the formation of woven bone during fracture healing

Answer 10

• Takes 2-4 weeks for healing
  dependent on the severity and position of the fracture and age of patient
• Inflammation and additional blood flow lead to
  callus formation.
  osteoblasts quickly form woven bone, to bridge the gap
  woven bone is weak as the collagen fibres are irregular
• Lamellar bone laid down -
  collagen organised in regular sheets to gives strength and resilience

Question 11

What are the causes of changes in bone density

Answer 11

• It can increase as a result of excessive mechanical simulation
• It can decrease due to immobilisation and sex hormone deficiency (menopause)

Question 12

What is wolff’s law

Answer 12

Bone adapts to the load under which it is placed

Question 13

Describe bone growth from fetus to adult

Answer 13

• Cartilage model formed by chondroblasts and reshaped by chondrocytes
• Replaced by bone (ossification) - endochondral (long bones) and intramembranous (flat bones)
• Ossification begins in the diaphysis
• Epiphysis is the 2nd centre of ossification
• Bone is laid down in the shaft and in the head
• The bony parts are separated by a plate of cartilage
• As long as the plate of cartilage is present and active the bone will increase in length
• By the end of puberty the epiphyseal plates fuse