Bones and the skeleton 1

Question 1

What are the 4 main functions of the skeleton?

Answer 1

Framework - supports soft tissues
Movement - muscles act on bones
Protection - of vital organs (eg, rib cage, skull)
Storage and release of chemical elements - (eg, Ca to regulate levels in blood and maintain healthy skeletal system)

Question 2

What are the 5 main bone shapes?

Answer 2

Flat bones - protect internal organs
(cranial vault, sternum, ribs, scapula, pelvic bones)
Lone bones - support weight, allow movement
(Most bone of upper/lower limbs)
Short bones - cube shaped, stability and some movement
(Wrist and ankle bones)
Irregular bones - complex shape
(Vertebrae)
Sesamoid bones - embedded in tendons, aid joint function
(patella)

Question 3

What is ‘lamellar bone’?

Answer 3

Adult bone

Question 4

What 2 sections is lamellar bone organised into?

Answer 4

Cortical and trabecular bone.

Question 5

What are the microscopic columns called within cortical bone?

Answer 5

Osteons

Question 6

What are osteons composed of? And what do they surround?

Answer 6

• Osteoblasts and osteocytes
• Surround central Haversian canal

Question 7

How are osteons and respective Haversian canals connected to each other?

Answer 7

Volkmann’s canals

Question 8

What covers cortical bone on the outside?
What covers cortical bone on the inside?

Answer 8

Outside: periosteum
Inside: endosteum

Question 9

What is cortical bone?

Answer 9

The hard outer layer of bones

Question 10

What is trabecular bone?

Answer 10

Spongy internal part of bones, located at wither end, near joints.

Question 11

What are the roles of an osteoclast?

Answer 11

Break down bone tissue: bone resorption.
Essential in maintenance, repair, remodelling of bones, regulates levels of blood Ca.
Dissolve minerals in bone and break down organic components using acids and enzymes.

Question 12

What is the role of an osteoblast?

Answer 12

Bone cells which work together in a group in osteon to synthesise organic and mineral parts of bone.
Are main cellular component of bone (mainly in periosteum and endosteum).

Question 13

What are the 3 types of cartilage?

Answer 13

Hyaline
Fibrocartilage
Elastic

Question 14

What are the properties of hyaline cartilage? Give example

Answer 14

Smooth, glossy
Ribs, nose, trachea

Question 15

What are the properties of fibrocartilage? Give example

Answer 15

Tough, resists strong compression and tension
Pubic symphysis, knee, intervertebral disc

Question 16

What are the properties of elastic cartilage? Give example

Answer 16

Flexible, provides support and shape.
External ear, epiglottis

Question 17

Describe endochondral ossification.

Answer 17

Indirect ossification so hyaline cartilage is the model/template for the bone to form from.
Primary and secondary ossification centres. Important in skull base formation as allows for growth.

Question 18

Describe intramembranous ossification.

Answer 18

Direct ossification, no cartilage precursor. This type of ossification is responsible for the formation of the flat bones of the skull, clavicle and mandible.

Question 19

Describe the 2 stages of endochondral ossification.

Answer 19

Primary ossification centre
Middle of the diaphysis (shaft of a long bone).
Secondary ossification centre
Appears at epiphysis (end of a long bone) near time of birth.
This then forms an epiphyseal plate (growth plate) of cartilage, which is sandwiched between primary and secondary ossification centres.
This allows increase in length of long bones.
Epiphyseal plates fuse at different times, most are fused by 20yrs.

Question 20

Describe the process of ossification in intramembranous ossification.

Answer 20

Ossification centres, which start the formation of the bone, appear in fibrous connective tissue. This happens when cells cluster together and become osteoblasts.
The osteoblasts then secrete a bone matrix, which forms little bits of bone.
Eventually a woven bone (disorganised bone) and periosteum form.
Later, the woven bone becomes an organised lamellar bone, which then forms cortical and trabecular bone.

Question 21

Describe the formation of primary teeth. 4 stages

Answer 21

Bud stage: tooth bud appears (week 8)
Cap stage: tooth bud cells arrange into enamel organ (eventually produce enamel), dental papilla (eventually produce dentine and pulp), and dental sac (provides a sort of ‘coating to enamel organ and dental papilla, eventually producing the supporting structures of the tooth).
Bell stage: cells separate into different layers, the crown of the tooth takes shape.
Crown stage: hard tissues of the tooth start to develop (dentine and enamel)

Question 22

What is Dentinogenesis ?

Answer 22

Formation of dentine

Question 23

What is Amelogenesis ?

Answer 23

Formation of enamel

Question 24

Describe process of dentinogenesis.

Answer 24

1st feature in crown stage of tooth development
Odontoblasts secrete organic matrix around area of the future cusp(s) of the tooth
Odontoblasts move towards centre of tooth, forming primary dentine.
Secondary dentine formed later after root formation, continues to develop throughout life.
Tertiary dentine forms in response to tooth wear and decay.

Question 25

Describe process of Amelogenesis.

Answer 25

Occurs during the crown stage of tooth development.
Dentine formation always before enamel formation
Ameloblasts release enamel proteins that contribute to enamel matrix
Enamel starts to mineralise by enzyme action ~3/4 month of pregnancy, beginning from the cusps and moving outwards. (Opposite direction of movement to dentine formation).

Question 26

What are the ages of tooth eruption, creating different dentition?

Answer 26

Primary dentition stage: 6 mnths to 5/6 yrs
Mixed dentition stage: 5/6 yrs to 10/12 yrs
Permanent dentition stage: 10/12 yrs onwards

Question 27

Expected number of primary teeth?

Answer 27

20

Question 28

Expected number of permanent teeth?

Answer 28

32