The Human Skeleton: A Dynamic System

Flashcards covering key concepts about the human skeleton, its functions, structure, and dynamic processes.

What is the common view of bones in the human skeleton?

Bones are seen as static structural rods that hold the body up.

What dynamic role does the human skeleton play beyond just support?

The skeleton actively influences our chemistry and responds to physical activity.

What three main types of cartilage are described?

Hyaline cartilage, elastic cartilage, and fibrocartilage.

Where is hyaline cartilage commonly found?

It forms articular surfaces of joints and connects ribs to the sternum.

What does elastic cartilage provide?

Maximum flexibility, found in structures like the external ear and epiglottis.

Where is fibrocartilage located, and what is its key characteristic?

It is found in intervertebral discs and menisci in the knee, known for its tensile strength.

What are the seven vital functions of the skeleton?

Support, protection, movement, electrolyte balance, acid-base balance, blood formation, hormone secretion.

How does the skeleton regulate electrolyte balance?

By managing calcium and phosphate levels, releasing calcium when needed.

What role do bones play in acid-base balance?

Bones release minerals to buffer blood against pH changes.

What is hematopoiesis?

The formation of blood cells in the red marrow of bones.

What is the main role of hormones secreted by bones?

They influence insulin action and the body's stress response.

How are bones categorized by shape?

Into long bones, short bones, flat bones, and irregular bones.

What is an example of a long bone?

The femur or humerus.

Where are short bones primarily found?

In the wrist and ankle.

What are sesamoid bones?

Small bones embedded within tendons, such as the kneecap.

What is the primary function of flat bones?

Protection, as seen in skull bones and the sternum.

What tells the structural story of a bone?

Bone markings, including projections, smooth surfaces, and depressions.

What do projections on bones indicate?

Areas built for stress where muscles or ligaments attach.

What is the function of smooth surfaces on bones?

They facilitate movement at joints.

What do depressions and passages in bones allow for?

Safe passage for blood vessels and nerves.

What are osteogenic cells?

Stem cells that can differentiate into various bone cell types.

What is the role of osteoblasts?

They are the builders that secrete the bone matrix.

What do osteocytes do?

They maintain and monitor the bone matrix.

What is the role of osteoclasts?

They break down or resorb bone matrix.

Why is the breakdown of bone necessary?

For bone growth, remodeling, and calcium release.

What is compact bone characterized by?

A dense and smooth outer layer organized into structural units called osteons.

What is spongy bone also known as?

Cancellous bone.

How does spongy bone differ in texture compared to compact bone?

It is porous and consists of trabeculae.

How frequently does spongy bone remodel?

Every three to four years.

What structural unit is found in compact bone?

The osteon or Haversian system.

What is the central canal's function in an osteon?

It carries nerves and blood vessels deep into the bone.

What are Volkmann's canals?

Crosswise passages that connect central canals to the bone surface.

How do osteocytes get their nutrients?

Through canaliculi that connect them to the central canal.

What is the composition of bone?

A composite material made of organic components like collagen and inorganic mineral salts.

What is ossification?

The process of bone formation.

What is intramembranous ossification?

Bone develops directly from a fibrous membrane.

What bones are formed through intramembranous ossification?

Most flat bones, such as most skull bones and clavicles.

What is endochondral ossification?

Bone forms by replacing cartilaginous models.

What bones are primarily formed through endochondral ossification?

Almost all bones below the skull, excluding clavicles.

What is interstitial growth?

Growth in length of long bones at the epiphyseal plate.

What drives appositional growth?

Osteoblasts adding new bone material beneath the periosteum.

What hormones influence postnatal bone growth?

Growth hormone, testosterone, and estrogen.

What is the role of parathyroid hormone (PTH)?

It controls calcium release from bones.

How does the body respond to low blood calcium levels?

PTH activates osteoclasts to resorb bone and release calcium.

What is Wolff's Law?

Bone grows or remodels in response to mechanical stress.

What happens to bones under reduced mechanical stress?

Bone mass is lost due to reduced building signals.

What are the four stages of bone healing?

Hematoma formation, fibrocartilaginous callus formation, bony callus formation, and remodeling.

What is the fibrocartilaginous callus?

Temporary structure that stabilizes a fracture before bony union.

How long does it take for a bony callus to form after a fracture?

Approximately eight weeks.

What is osteoporosis?

A condition where bone resorption outpaces bone formation, leading to reduced bone mass.

Who is most at risk for osteoporosis?

Postmenopausal older women due to drop in estrogen levels.

What preventive measure is emphasized for bone health?

Weight-bearing exercise throughout life.

How does the skeleton function dynamically?

It's a constantly recycling mineral vault, responding to internal and external signals.