L1: Skeletal system

Question 1

What are bones?

Answer 1

Calcified connective tissue.

Question 2

How many bones are found in the body?

Answer 2

206

Question 3

What are the functions of bones?

Answer 3

1) Support body & shapes it (framework for the body)
2) Protection of certain organs e.g. skull protects brain.
3) gives attachment to muscles & joints
4) Long bones provide levers for muscles to move joints
5) Formation of blood cells in red marrow.
6) Store & provide body with minerals; Calcium & phosphorus in emergencies.

Question 4

What are bones classified according to?

Answer 4

According to:

A. Position.
B. Development.
C. Structure.
D. Shape.

Question 5

Classification of bones according to position

Answer 5

Axial and appendicular

Question 6

What is the axial skeleton?

Answer 6

skull, vertebral column, Sternum & Ribs

Question 7

What is the appendicular skeleton?

Answer 7

Bones of upper and lower limbs

Question 8

Describe the vertebral column

Answer 8

has 32-33 vertebrae, divided into:

1) Cervical (neck): 7 cervical vertebrae.
2) Thoracic (chest): 12 thoracic vertebrae.
3) Lumbar (low back): 5 lumbar vertebrae.
4) Sacrum: 5 fused sacral vertebrae.
5) Coccyx (tail): 3-4 fused coccygeal vertebra

Question 9

What is the function of the thoracic cage?

Answer 9

It protects heart & lungs & allows breathing

Question 10

What does the thoracic cage consist of?

Answer 10

1) Sternum: anteriorly.
2) Ribs: 12 pairs laterally.
3) 12 Thoracic vertebrae: posteriorly.

Question 11

Compare between the upper limb and lower limb

Answer 11

Question 12

What is the mechanism of formation of intramembranous bones?

Answer 12

The condensed mesenchymal tissue → undergoes bone formation directly

Question 13

What are examples of intramembranous bones?

Answer 13

 shaft of clavicle

 skull cap

 Bones of face.

Question 14

What is the mechanism of formation of intra-cartilaginous bones?

Answer 14

• The condensed mesenchymal tissue → chondrification first to form a cartilaginous model
• Then bone is deposited in this model

Question 15

What are examples of intra-cartilaginous bones?

Answer 15

All bones of limbs except shaft of clavicle.

Question 16

Compare between cancellous (spongy) bones and compact bones

Answer 16

Question 17

What are bones classified into according to ossification?

Answer 17

Intramembranous and intra-cartilaginous bones

Question 18

What are bones classified into according to structure?

Answer 18

Cancellous (spongy) and compact

Question 19

What are bones classified into according to shape and give examples for each one?

Answer 19

Question 20

What are the parts of a long bone?

Answer 20

A long bone consists of 2 ends & a shaft.

Question 21

What is (epiphysis)?

Answer 21

The end of long bone.

Question 22

What is the epiphyseal Cartilage?

Answer 22

• a hyaline cartilaginous plate separate the end from
  the shaft
• It is the site of growth in length of bone.
• It ossifies at a certain age forming epiphyseal
  line.

Question 23

What is the diaphysis and what is it composed of?

Answer 23

• The shaft of long bone
• Composed of:
   a cylinder of compact bone with a cavity
   Medullary cavity contains bone marrow.
   Bone marrow occupies the marrow cavity in long & short bones & cancellous bone in flat & irregular bones:
• At birth, marrow is red & hematopoietic.
• At 7 years of age, yellow marrow begins to appear in distal bones of limbs.

Question 24

What is the metaphysis?

Answer 24

Wide expanded end of shaft close to epiphyseal cartilage.

Question 25

What is the periosteum and what is its function?

Answer 25

• A fibrous membrane covering Shaft.

- responsible for growth of bone in thickness

Question 26

What is the blood supply of long bones?

Answer 26

Nutrient artery: Passes through nutrient canal

Periosteal arteries

Metaphyseal arteries

Epiphyseal arteries

NB. The epiphyseal plate is avascular (= doesn`t have blood supply) & is supplied by diffusion.

Question 27

❖ A 67-year-old woman presented to the emergency department with 4-month history of worsening lower back pain.

❖ There was no history of trauma or falls.

❖ She completed her investigations with serology and radiology.

Answer 27

❖ Based on the mentioned history and investigations, the patient was diagnosed with severe osteoporosis.

Question 28

What are the main cells responsible for bone formation and resorption?

Answer 28

• osteoblast cell is responsible for bone formation
• while osteoclast is responsible for bone resorption

Question 29

What are the two main hormones responsible for calcium deposition and removal from bones?

Answer 29

• calcitonin is responsible for calcium deposition in bone
• while parathormone is responsible for mobilization of calcium from bone