Skeletal System

Question 1

Explain the functions of Bones.

Answer 1

Bone function

• Support
• Protection
• Assist in movements
• Mineral homeostasis
• Blood cell production
  
  • Homepoiesis in red bone marrow

Question 2

Explain the structure of long bones.

Answer 2

Long bones

• Parts of a long bone
  
  • Diaphysis: Shaft of long bone; made up mostly of compact bone
  • Epiphysis: Broad end of long bone; mostly spongy bone
  • Metaphysis: Growth area between Diaphysis and Epiphysis
  • Articular cartilage: Hyaline cartilage at joint.
  • Periosteum: Fibrous covering over most of bone
  • Medullary cavity: (Marrow) with fat and blood cells
  • Endosteum: Membrane lining medullary cavity

Question 3

Explain the microscopic structure of bone.

Answer 3

Microscopic Structure of Bone

• Matrix
  
  • 25% water, 25% collagen fibers, 50% mineral salts
• Cells
  
  • Osteogenic cells in periosteum ->
  • Osteoblasts
    
    • Secrete collagen fibers
    • Build matrix and become trapped in lacunae
    • Become ->
  • Osteocytes that maintain bone
  • Osteoclasts are formed from monocytes
    
    • Digest bone matrix for normal bone turnover

Question 4

Which cells are found in bone tissue?

Answer 4

Cells in bone tissue

1. Osteogenic cell
2. Osteoblast
3. Osteocyte
4. Osteoclast

Question 5

Explain the Compact bone structure.

Answer 5

Compact Bone Structure

• Canaliculi (“little canals”)
  
  • Contain extensions of osteocytes
  • Permit flow of ECF between central canal and lacunae
• Compact bone is covered by Periosteum
• Perforating (Volkmann’s) canals
  
  • Carry blood and lymphatic vessels and nerves from Periosteum
  • They supply central (Haversian) canals and also bone marrow

Question 6

Explain the structure of Spongy bone.

Answer 6

Spongy bone

• Not arranged in osteons
• Irregular latticework of trabeculae
  
  • These contain lacunae with osteocytes and canaliculi
• Spaces between trabeculae may contain red bone marrow
• Spongy bone is lighter than compact bone, so reduces weight of skeleton

Question 7

Explain Ossification

Answer 7

Bone formation

• Known as ossification
• Timeline
  
  • Initial bone development in embryo and fetus
  • Growth of bone into adulthood
  • Remodeling: Replacement of bone
  • Repair if fractures occur
• Mesenchyme (early connective tissue) model
  
  • This initial “skeleton” model will be replaced by bone tissue beginning at 6 weeks of embyronic life

Question 8

Explain Growth in Length.

Answer 8

Growth in Length.

• Chondrocytes divide and grow more cartilage on epiphysal side of the epiphyseal plate
• Chondrocytes on the diaphyseal side die and are replaced by bone
• Therefore bone grows from the diaphyseal side towards epiphyseal side
• Growth in length stops between 18-25 years; cartilage in epiphyseal plate is completely replaced by bone (epiphyseal line).

Question 9

Bones of skull (anterior).

Answer 9

Bones of skull (anterior view).

Question 10

Bones of Skull right lateral view.

Answer 10

Bones of Skull right lateral view.

Question 11

Explain the functions of the Vertebrae.

Answer 11

Vertebrae - Functions

• Encloses spinal cord
• Supports head
• Point of attachement for muscles of back, ribs and pelvic girdle

Question 12

List the regions of the Vertebrae

Answer 12

Vertebrae - Regions

• 7 cervical
• 12 thoracic
• 5 lumbar
• 1 sacrum and 1 coccyx

Question 13

What is Disc herniation?

Answer 13

Disc herniation

Question 14

Where are the Sacrum and Coccyx located?

Answer 14

Sacrum and Coccyx

Question 15

Skeletal structure of Thorax.

Answer 15

Skeletal structure of Thorax.

Question 16

Where are Right Ulna and Radius located?

Answer 16

Right Ulna and Radius

Question 17

Where is Right Femur located?

Answer 17

Right Femur

Question 18

Explain different types of fractures.

Answer 18

Types of Fractures

• Partial: Incomplete break (crack)
• Complete: bone broken in two or more pieces
• Closed (simple): not through skin
• Open (compound): broken ends break skin

Question 19

Explain Remodeling and Repair.

Answer 19

Remodelin and Repair.

• Remodeling in response to use
  
  • Resorption by osteoclasts and
  • Deposition by osteoblasts
• Repair after fracture
  
  • Dead tissue removed
  • Chondroblasts -> fibrocartilage -> spongy bone deposited by osteoblasts -> remodeled to compact bone

Question 20

Treatment of Fractures?

Answer 20

Treatment of Fractures

• Conservative
• Surgical - oestosynthesis
  
  • Plates
  • Screws
  • Nails
  • Ex-fix

Question 21

Which is the standard treatment of Fractures?

Answer 21

Treatment Fractures

• Standard=conservative (children!)
  
  • Reduction of bone ends
  • Immobilisation in a plaster cast including joints above and below the fracture
  • Time to heal!
• Traction

Question 22

Explain the Negative Feedback Loop in bone remodeling.

Answer 22

Negative Feedback Loop

• Blood levels of Ca²⁺ controlled
• Negative feedback loops
• Parathyroid hormones (PTH) -> increases osteoclast activity + decreases loss of Ca²⁺ in urine
• Calcitonin -> decreases osteoclast activity

Question 23

What are the effect of Exercise on Bone tissue?

Answer 23

Exercise and Bone tissue

• Bone strengthened in response to use
• Bone reabsorbed during disuse;
  
  • During prolonged bed rest
  • Fracture with cast/immobiliser
  • Astronauts without gravity

Question 24

How does aging effect the skeletal system?

Answer 24

Aging and skeletal system

• Birth through adolescence: more bone formed than lost
• Young adults: gain and loss about equal
• As levels of sex steroids decline with age:
  bone resorption > bone formation
• Bones become brittle and lose calcium

Osteoporosis = Disease where decreased bone strength increase the risk of fracture. More common amongst elderly.