Bones, Osteoporosis, and Bone Health (Video Notes)

The skeleton is made up of bones that provide support and shape to the body.
They protect soft internal organs such as the brain and heart from injury.
Together with muscles, strong bones enable the body to move freely.
Bones have a solid outer surface called compact bone.
The inner bone is called spongy bone because it is less dense than compact bone and has many small holes like a sponge.

Outer surface: compact bone (dense and strong).
Inner structure: spongy bone (less dense with holes; contributes to lightness and housing marrow).

Osteoclasts: cells that break down bone tissue (bone resorption).
Osteoblasts: cells that make new bone tissue, using minerals from the blood such as calcium and phosphate.
Hormonal regulation: hormones such as estrogen, growth hormone, and testosterone help keep the number and activity of osteoblasts higher than osteoclasts, so more bone is made than removed.
Mechanical/physical influence: physical forces and pressure during exercise help bones grow stronger and denser.
Combined effect: these processes allow bones to grow strong in children and young adults.

Peak bone mass: the strongest, most dense bones are achieved in the 30s (peak bone mass).
After peak bone mass, osteoclasts gradually remove more bone than osteoblasts make (bone loss accelerates with age).
Osteoporosis: a condition that leads to weakened bones, making them easier to break.
Healthy bone condition: dense enough to support and protect the body and handle stresses of movement and minor injuries.
Osteoporosis in contrast: abnormally thin bones with larger holes in the spongy bone.

Primary osteoporosis: usually related to older age and reduced estrogen in women.
Secondary osteoporosis: affects both children and adults; related to other diseases or conditions (e.g., cancer, hormone problems, or use of certain medications).
Risk emphasis: a person has greater risk for either type if they don’t develop enough bone mass during growth from childhood to adulthood.

Family history of osteoporosis.
Being white or Asian.
Being female.
Poor diet.
Medications such as steroids or certain seizure medicines.
Lack of physical activity and weight-bearing exercise.
Lifestyle behaviors such as smoking and heavy alcohol use.
Greater risk for osteoporosis if there is abnormal bone loss after age 30; some bone loss is normal after this age, but risk factors can make osteoporosis more likely with aging.
Increased bone loss after menopause is common due to changes in hormones.

After menopause, ovaries stop making estrogen.
The drop in estrogen makes osteoclasts more active than osteoblasts.
Bones may break or fracture easily because they cannot withstand normal physical strain and pressure.
Common fracture locations in osteoporosis: wrists, spine, and hips.

Building strong healthy bones through a diet rich in calcium and vitamins and regular exercise can help prevent and treat osteoporosis.
Regular physical activity and weight-bearing exercises are emphasized as protective strategies.

Bisphosphonates (listed as biphosphonates in the transcript): commonly used to slow bone resorption by acting on osteoclasts.
Denosumab: targets osteoclast activity to reduce bone loss.
SERMs (Selective Estrogen Receptor Modulators): affect estrogen pathways to influence bone remodeling.
Calcitonin: hormone therapy affecting bone resorption.
Parathyroid hormone: acts on osteoblasts to promote bone formation.
Calcium and vitamin D: foods or supplements recommended to support bone health.
Overall framing: most medications for osteoporosis act on osteoclasts; parathyroid hormone acts on osteoblasts; nutrition supports both processes.

Food or supplements containing calcium and vitamin D are recommended for osteoporosis management.
Adequate calcium and vitamin D intake supports bone mineralization and maintenance.

Understanding bone remodeling balance helps explain why aging increases fracture risk and how lifestyle choices affect bone health.
Menopause is a critical period for bone loss due to estrogen decline; monitoring bone density and addressing risk factors is important.
Prevention focuses on early bone mass accrual in youth, ongoing physical activity, and nutrition to support peak bone mass and slow loss later in life.
Treatment options provide strategies to reduce fracture risk and maintain daily function through pharmacologic and nutritional means.

Bone health intersects with endocrinology (hormone regulation), orthopedics (fracture risk and healing), nutrition (calcium and vitamin D), and public health (prevalence of osteoporosis and prevention strategies).
The balance of bone formation and resorption is a dynamic example of tissue homeostasis regulated by cells, hormones, and mechanical forces.