Structure, Function, Growth and Pathology of Bone

What bones comprise the axial skeleton?

the bones of the skull, thorax, and vertebral column, forming the longitudinal axis of the body

What bones comprise the appendicular skeleton?

What are the main functions of the skeletal system?

Provides support, mineral storage (especially calcium and phosphate), blood cell production, protection of organs, and leverage for movement

What is the epiphysis of a long bone?

The expanded end of a long bone composed mostly of spongy (trabecular) bone, covered by a thin layer of compact bone, which helps resist forces and transfer weight to joints.

What is the metaphysis and its role?

A narrow zone connecting the epiphysis to the diaphysis, important during bone growth as it contains the epiphyseal (growth) plate in growing bones

Describe the diaphysis of a long bone.

The long tubular shaft of the bone, primarily composed of compact bone and housing the medullary (marrow) cavity.

What is the medullary cavity?

The hollow central space inside the diaphysis which contains bone marrow—red marrow for blood cell production and yellow marrow for fat storage.

What is the periosteum and its functions?

A dense fibrous membrane covering the outer surface of bones (except at joints), providing isolation, a pathway for blood vessels and nerves, and supporting bone growth and repair.

Name the four types of bone cells and their primary functions.

Osteocytes (maintain bone matrix), osteoblasts (form new bone matrix), osteoprogenitor cells (stem cells that create osteoblasts), and osteoclasts (resorb and remodel bone).

What is osteoid?

The organic, unmineralized matrix produced by osteoblasts, mainly composed of collagen fibers, which later calcifies to become bone

What minerals primarily compose the inorganic bone matrix?

Calcium phosphate forming hydroxyapatite crystals, along with calcium carbonate, sodium, magnesium, and fluoride ions provide hardness.

How does spongy bone differ from compact bone?

Spongy bone consists of trabeculae forming an open lattice, lacks osteons, has no central canals, and reduces bone weight while distributing stress multidirectionally.

What is appositional bone growth?

Growth in bone diameter where osteoblasts add new layers beneath the periosteum and osteoclasts resorb bone from the medullary cavity to enlarge it

What hormones regulate blood calcium levels?

Parathyroid hormone (increases blood calcium) and calcitonin (decreases blood calcium).

How does parathyroid hormone maintain calcium homeostasis

Stimulates osteoclasts to release calcium from bone, enhances intestinal calcium absorption via calcitriol, and reduces calcium excretion by the kidneys

What conditions cause abnormal bone growth?

Pituitary growth failure (short bones), achondroplasia (slow cartilage growth), Marfan syndrome (long limbs), gigantism, acromegaly, and fibrodysplasia ossificans progressiva (ectopic bone formation).

What are common types of bone fractures?

Closed/simple, open/compound, transverse, spiral, displaced, nondisplaced, compression, greenstick, comminuted, epiphyseal, Pott, and Colles fractures

Describe the stages of fracture repair.

Hematoma formation, internal and external callus formation (cartilage and spongy bone), replacement of cartilage by bone, and remodeling to restore bone shape and strength.

What is the difference between closed (simple) and open (compound) fractures?

Closed fractures do not break the skin, while open fractures protrude through the skin and pose higher risk of infection and bleeding

What is a greenstick fracture?

An incomplete fracture typical in children where one side of the bone breaks and the other side bends.

What occurs during remodeling in bone tissue?

Older bone matrix is resorbed by osteoclasts and replaced with new matrix by osteoblasts, maintaining bone strength and mineral balance

Describe the role of calcium in physiology beyond the skeletal system.

Calcium is vital for muscle contraction, nerve impulse transmission, blood clotting, and cell signaling.

What is fibrodysplasia ossificans progressiva (FOP)?

A rare genetic disorder causing bone formation in soft tissues like skeletal muscles, leading to heterotopic bone growth.

What happens to bone growth and epiphyseal cartilage at puberty?

Hormones accelerate growth and ultimately replace epiphyseal cartilage with bone, leading to closure of the growth plate.