Human Anatomy & Physiology I: The Skeletal System

Flashcards covering bone classification, anatomy, physiology, histology, growth, and the skeletal system's axial, appendicular, and joint components.

Hematopoiesis

The formation of blood cells in red bone marrow.

Long bone

A bone greater in length than width, such as the femur or humerus.

Short bone

A bone where the length nearly equals the width, such as carpals or tarsals.

Flat bone

Bones with thin surfaces that may be slightly curved, such as cranial bones.

Irregular bone

Bones with elaborate or complex shapes, such as vertebrae or the sphenoid.

Diaphysis

The elongated, usually cylindrical shaft of a long bone that provides leverage and weight support.

Epiphysis

The end of a long bone, composed of an outer thin layer of compact bone and an inner region of spongy bone.

Metaphysis

The region of a long bone located between the diaphysis and the epiphysis.

Epiphyseal plate

A thin layer of hyaline cartilage within the metaphysis of a growing bone that provides for lengthwise bone growth.

Periosteum

A tough fibrous layer of dense irregular connective tissue that covers the external surface of bone.

Endosteum

A thin layer of connective tissue containing osteoprogenitor cells and osteoblasts that covers internal bone surfaces.

Red bone marrow

Hematopoietic tissue located in spongy bone and the medullary cavity of children; in adults, it is found in the axial skeleton and proximal epiphyses of the humerus and femur.

Yellow bone marrow

A fatty substance resulting from red bone marrow degeneration as children mature, which may convert back to red bone marrow during severe anemia.

Osteoid

The organic component of the bone matrix produced by osteoblasts, containing collagen protein and semisolid ground substance.

Osteocytes

Mature bone cells derived from osteoblasts that live inside lacunae and detect stress on the bone to trigger new formation.

Osteoblasts

Cells formed from osteoprogenitor stem cells that synthesize and secrete osteoid.

Osteoclasts

Large, multinucleated, phagocytic cells involved in bone resorption or the breakdown of bone.

Osteon (Haversian system)

The basic functional and structural unit of mature compact bone, appearing like a tree trunk.

Lamellae

Concentric rings of bone connective tissue that surround the central canal in an osteon.

Lacunae

Tiny spaces between lamellae where osteocytes reside.

Canaliculi

Tiny channels that connect lacunae and allow osteocytes to communicate and share nutrients.

Intramembranous ossification

A process where bone forms directly from mesenchyme without a cartilage stage, producing flat bones of the skull.

Endochondral ossification

A process where bone replaces a hyaline cartilage model, starting with a cartilage skeleton.

Interstitial growth

Bone growth in length occurring at the epiphyseal plate in the metaphysis.

Appositional growth

Bone growth in width occurring at the periosteum.

Parathyroid hormone (PTH)

A hormone released in response to low blood calcium that increases osteoclast activity and bone resorption.

Calcitonin

A hormone released in response to high blood calcium that decreases osteoclast activity and encourages calcium storage in bone.

Axial skeleton

The 80 bones comprising the skull, thoracic cage, and vertebral column used for support and protection.

Appendicular skeleton

The 126 bones of the limbs and girdles, including the pectoral and pelvic girdles, primarily used for movement.

Atlas (C1)

The first cervical vertebra that supports the head and allows for the head-nodding 'YES' motion.

Axis (C2)

The second cervical vertebra that features the dens (odontoid process) and allows for the 'NO' motion.

Synarthrosis

A functional classification of joints that are immovable, such as sutures of the skull.

Amphiarthrosis

A functional classification of joints that are slightly mobile, such as symphysis joints.

Diarthrosis

A functional classification of joints that are freely mobile; all of which are synovial joints.

Gomphosis

A fibrous synarthrosis joint where a tooth is held in a socket by a periodontal ligament.

Syndesmosis

A fibrous amphiarthrosis joint where bones are joined by an interosseous membrane, such as between the radius and ulna.

Synchondrosis

A cartilaginous synarthrosis joint joined by hyaline cartilage.

Symphysis

A cartilaginous amphiarthrosis joint featuring a fibrocartilage pad that acts as a shock absorber.

Flexion

A movement that decreases the angle between bones, moving them closer together.

Abduction

A movement that moves a bone away from the midline of the body.

Pronation

Medial rotation of the forearm where the palm faces posteriorly.

Supination

Lateral rotation of the forearm where the palm faces anteriorly.