Anatomy

Question 1

What are the types of collagen?

Answer 1

• Type I: Bone, tendon, skin (OI, Ehlers-Danlos)
• Type II: Hyaline cartilage (chondrodysplasia)
• Type IV: Basement membrane (Alport syndrome)

OI: Osteogenesis imperfecta; GAG: Glycosaminoglycan.

Question 2

What is the structure of collagen?

Answer 2

Triple helix (Gly-X-Y repeats), crosslinked by lysyl oxidase.

The structure is critical for its tensile strength.

Question 3

What vitamin is required for collagen synthesis?

Answer 3

Vitamin C.

Hydroxylation defects can lead to scurvy.

Question 4

What role do elastin and fibrillin play in the body?

Answer 4

Stretch/recoil in ligaments, aorta, skin.

Diseases related to these proteins include Marfan’s syndrome and cutis laxa.

Question 5

What is aggrecan?

Answer 5

Major proteoglycan in cartilage with a ‘bottle brush’ structure.

It plays a key role in cartilage hydration and resilience.

Question 6

What is the function of hyaluronic acid?

Answer 6

Non-sulfated GAG; contributes to synovial fluid viscosity.

It helps in lubrication and shock absorption in joints.

Question 7

What are the two main types of joints?

Answer 7

• Synarthroses: Immovable (skull sutures)
• Diarthroses: Synovial joints (knee, hip)

Each joint type serves different functions in mobility.

Question 8

What is the composition of articular cartilage?

Answer 8

• Type II collagen (60% dry weight)
• Aggrecan
• Water (80%)

This composition is vital for the cartilage’s mechanical properties.

Question 9

What are the zones of articular cartilage?

Answer 9

• Superficial: Lubricin (boundary lubrication)
• Middle: High PG/water content (shock absorption)
• Deep: Radial collagen fibers (anchors to bone)

Each zone has distinct functions and structural characteristics.

Question 10

What is the role of the synovium?

Answer 10

• Type A cells: Phagocytic
• Type B cells: Hyaluronic acid production

The synovium is crucial for joint health and function.

Question 11

How is normal synovial fluid characterized?

Answer 11

WBC <200/mm³, glucose ≈ serum, viscosity (string sign).

These parameters help assess joint health.

Question 12

What are the two main types of bone?

Answer 12

• Cortical: 80% skeleton (long bone shafts)
• Cancellous: Vertebrae/pelvis (osteoporosis-prone)

The distribution of these types affects bone strength and health.

Question 13

What is the Wnt/β-catenin pathway’s role in bone biology?

Answer 13

Osteoblast activation (↑ bone mass).

Inhibitors like sclerostin and Dkk-1 are targets for osteoporosis treatment.

Question 14

What does the RANK/RANKL/OPG pathway regulate?

Answer 14

Osteoclast differentiation.

RANKL from osteoblasts/T cells activates osteoclasts; OPG blocks RANKL.

Question 15

What distinguishes Type 1 muscle fibers?

Answer 15

Slow-twitch, oxidative (endurance).

These fibers are more fatigue-resistant and are utilized in prolonged activities.

Question 16

What distinguishes Type 2b muscle fibers?

Answer 16

Fast-twitch, glycolytic (sprinters).

These fibers are designed for short bursts of power and speed.

Question 17

What triggers muscle contraction?

Answer 17

Ca²⁺ release → actin-myosin crosslinking → sarcomere shortening.

This process is essential for muscle function.

Question 18

What are common collagen disorders?

Answer 18

• Osteogenesis imperfecta (Type I)
• Ehlers-Danlos syndrome (Types I/III)
• Alport syndrome (Type IV)

These disorders affect connective tissue integrity and function.

Question 19

What enzymes are involved in cartilage degradation?

Answer 19

• MMPs (collagenases)
• Aggrecanases (ADAMTS-4/5)

These enzymes are often elevated in osteoarthritis.

Question 20

What is osteoporosis associated with?

Answer 20

Wnt/RANKL dysregulation.

This condition leads to increased fracture risk due to decreased bone density.

Question 21

What is Paget’s disease characterized by?

Answer 21

↑ osteoclast activity.

Bisphosphonates are often used to target RANKL in treatment.