Lecture 11: Bones

Explain the basic properties and functions of muscles

Muscles are responsible for movement, stability and heat production in the body and play a role in maintaining posture and stabilising joints.

• Skeletal muscle: voluntary control, attached to bones, responsible for movement

• Cardiac muscle: involuntary, found in the heart, responsible for pumping blood

• Smooth muscle: involuntary, found in organs like intestines and blood vessels, control functions like digestion and blood flow

What does muscle function depend on?

Muscle function depends on ability to contract and respond to nerve impulses.

Describe bone remodelling/turnover

Bone remodelling is the continuous process of bone resorption and formation, important for maintaining bone strength and mineral balance

Why is bone remodelling/turnover important?

Crucial for:

• maintaining bone strength

• repairing damage

• regulating calcium levels in the blood

It ensures bones remain healthy and can adapt to mechanical stresses.#

How is bone remodelling/turnover achieved?

Occurs through a balance between bone resorption (breakdown) by osteoclasts and bone formation by osteoblasts.

• Influenced by hormones (e.g., parathyroid hormone, oestrogen) and mechanical stress

Understanding of different bone cells

• Osteoblasts: build new bone by producing collagen and mineralising the matrix

• Osteoclasts: break down bone tissue to release minerals and remodel bone

• Osteocytes: mature bone cells embedded in the bone matrix, helping regulate mineral homeostasis

• Bone lining cells: cover bone surfaces and regulate calcium exchange

Describe how bones grow/develop

Occurs through:

• Endochondral ossification (long bones): a cartilage model is gradually replaced by bone

• Intramembranous ossification (flat bones)

Factors influencing bone development include:

• Genetics: determines potential growth

• Hormones: growth hormone, thyroid hormone, and sex hormones regulate bone growth

• Nutrition: calcium, vitamin D, and protein are essential for bone formation

Cause of osteoporosis

• Imbalance between bone resorption and formation, leading to weak bones.

• Hormonal changes (e.g., estrogen decline in menopause).

• Nutritional deficiencies (e.g., low calcium and vitamin D).

• Lack of mechanical stress on bones

Risk factors of osteoporosis

• Aging (bone mass decreases with age)

• Gender (women at higher risk, especially postmenopausal)

• Family history

• Lifestyle factors (smoking, excessive alcohol intake, poor diet)

• Medical conditions (e.g. rheumatoid arthritis)

Lifestyle to prevent or slow osteoporosis progression

• Adequate calcium and vitamin D intake

• Avoiding smoking and excessive alcohol

• Engaging in regular physical activity

Role of exercise in osteoporosis

Weight-bearing and resistance exercises help maintain bone density, such as walking, running, and strength training stimulate bone formation and reduce the risk of fracture