skeletal system

What does the appendicular skeleton include?

Limbs, pectoral girdle (shoulders), pelvic girdle (hips), and clavicle

What is the extracellular matrix of bone composed of?

45% organic material and 55% crystallized mineral salts

What are the main mineral components of bone?

Calcium phosphate and calcium carbonate, along with other ions like magnesium, fluoride, and sulfate

What are the two main types of bone tissue?

Compact bone and spongy bone

Where is compact bone found?

Beneath the periosteum of all bones

What are osteons?

Repeating structural units of compact bone, consisting of concentric lamellae around a central Haversian canal

What are the two principal divisions of the skeletal system?

Axial and Appendicular

How many bones are in the axial division?

About 80 bones

What does the axial skeleton include?

Head, neck, trunk (ribs + sternum), vertebral column, sacrum

How many bones are in the appendicular division?

About 126 bones

What is spongy bone characterized by?

Lamellae arranged in regular patterns of thin columns (trabecular) with spaces filled with red/yellow bone marrow

What is the function of spongy bone?

To diffuse stress and aid in the transfer of force through the body

What is the periosteum?

A rigid wrapping that covers bones, except in areas covered by cartilage

What is the diaphysis of a bone?

The long middle sheath of the bone

What is the medullary cavity?

A central cavity in long bones that acts as a highway for blood vessels

What role do osteoblasts play in bone health?

They initiate the calcification process

What role do osteoclasts play in bone health?

They break down the extracellular matrix via enzymes and acids

What is the nutrient artery?

The main blood vessel that supplies the bone, passing through compact bone at the diaphysis

What are periosteal arteries?

Arteries that perforate the exterior of compact bone and invade the extracellular matrix

What is the significance of the periosteum in bone repair?

It is capable of laying down more bone and is highly vascular

What type of nerves supply the periosteum?

Sensory nerves that carry pain fibers, making the periosteum sensitive to tearing and tension

How long can bone formation take?

Up to 20 years

What is the appearance of spongy bone?

It looks like a honeycomb structure

What is the role of red bone marrow?

It is involved in blood cell production and is highly vascularized

What is articular cartilage?

Cartilage that covers the surfaces of bones at joints

What is the role of osteoblasts?

Osteoblasts initiate the calcification process and secrete the extracellular matrix of bone.

What is the function of osteoclasts?

Osteoclasts break down the extracellular matrix via enzymes and acids.

Why are both osteoblasts and osteoclasts important?

Both are needed for healthy bone growth and maintenance, as bone is always remodeling.

What is intramembranous ossification?

A process where mesenchyme transforms directly into bone without a cartilage stage.

What is endochondral ossification?

A process where mesenchyme develops into cartilage, which is then replaced by bone.

What occurs at the ossification center during bone development?

Mesenchymal cells cluster and differentiate, leading to the secretion of the extracellular matrix by osteoblasts.

What is the primary ossification center?

The location where bone tissue forms and replaces cartilage in the diaphysis region.

What happens to the cartilage model during bone growth?

The cartilage hypertrophies and calcifies, allowing for the formation of the primary ossification center.

What is the significance of the epiphyseal plate?

It allows for longitudinal bone growth from the diaphyseal side during development.

What happens when the epiphyseal plate closes?

Closure occurs in adulthood, ceasing further lengthening of the bone.

What are the four zones of the epiphyseal plate?

1. Zone of resting cartilage, 2. Zone of proliferation, 3. Zone of hypertrophy, 4. Zone of calcification.

What role do chondrocytes play in bone growth?

Chondrocytes form cartilage, undergo interstitial growth, and replace cells that die at the diaphyseal side.

What is bone resorption?

The removal of minerals and collagen fibers from bone, primarily by osteoclasts.

What stimulates the activity of osteoblasts?

Vitamin A stimulates osteoblast activity.

What hormonal changes affect bone growth during adolescence?

Insulin-like growth factors are important during childhood, while sex hormones play a key role during puberty.

How does bone mass change from birth to middle age?

More bone tissue is produced than lost during childhood, but in middle age, bone resorption outpaces deposition.

What causes loss of bone mass in middle age?

A decrease in sex hormones leads to demineralization and loss of calcium and other minerals.

What are bone markings?

Features on bones where tendons, ligaments, and arteries attach or pass through.

How do forces exerted by muscles affect bone structure?

They influence the development of bone markings, leading to holes and divots in the bone.

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