Skeletal System

These flashcards cover the classification of bones by type and shape, the microscopic and macroscopic structure of bone tissue, bone cell types, processes of bone formation and growth, bone remodeling, common bone disorders like osteoporosis, and various types of fractures and their repair.

Axial Skeleton

The 80 bones along the central axis of the body, including the skull, vertebral column, and thoracic cage.

Appendicular Skeleton

The 126 bones of the limbs and the girdles that attach the limbs to the axial skeleton.

Diaphysis

The narrow, long central shaft of a long bone.

Epiphysis

The expanded ends of a long bone.

Long Bones

Bones found in the appendicular skeleton characterized by a long central shaft and expanded ends, such as the humerus and femur.

Short Bones

Box-shaped bones, such as the carpals (wrist bones) and tarsals (ankle bones).

Flat Bones

Bones with a broad surface, such as the sternum, scapula, ribs, and cranial bones.

Sesamoid Bone

A small, flat bone embedded within a tendon, like the patella (kneecap).

Irregular Bones

Bones with a complex shape that do not fit into other categories, such as vertebrae and temporal bones.

Osseous Tissue

The scientific term for bone tissue.

Osteon

The repeating ring-shaped structural and functional unit of compact bone.

Concentric Lamellae

Ring-shaped plates of osseous tissue found within an osteon.

Lacunae

Small spaces within the bone matrix where osteocytes are housed.

Osteocyte

Mature cells of bone, derived from osteoblasts, found within lacunae.

Osteoid

The organic matrix of bone, primarily collagen fibers, secreted by osteoblast cells before mineralization.

Hydroxyapatite

A calcium phosphate hydroxide salt that mineralizes osteoid and gives bone its hardness and rigidity.

Osteoblast

Bone-building cells that form the bone matrix by secreting osteoid.

Osteogenic Cell

Stem cells found in bone membranes that differentiate into osteoblasts.

Periosteum

A membrane covering the superficial surfaces of bones, containing osteogenic cells and blood vessels.

Endosteum

A membrane lining inner surfaces deep within bones, including canals and the medullary cavity, containing osteoclasts.

Osteoclast

Large cells that break down (resorb) bone matrix, releasing calcium, and are important for remodeling and fracture repair.

Compact Bone

A dense, smooth, solid superficial layer of bone tissue that provides strength and protection.

Central Canal

The canal within an osteon that contains blood vessels and nerves, running parallel to the long axis of the bone.

Perforating Canals (Volkmann's Canals)

Canals that run perpendicular to central canals, connecting blood vessels and nerves from the surface deep into the bone.

Medullary Cavity

The central space inside the diaphysis of long bones, filled with bone marrow.

Spongy Bone (Trabecular Bone)

Bone tissue found deep within bones, characterized by irregularly arranged struts of bone (trabeculae) with intervening spaces called trabecular cavities.

Trabeculae

The irregularly arranged branching struts or plates of bone found in spongy bone.

Articular Cartilage

Hyaline cartilage covering the articular surface of an epiphysis where a joint is formed.

Metaphysis

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

Epiphyseal Growth Plate (Epiphyseal Plate)

A layer of hyaline cartilage where longitudinal bone growth (interstitial growth) occurs during adolescence.

Epiphyseal Line

The remnant of a completely ossified epiphyseal growth plate, indicating the cessation of longitudinal bone growth in adults.

Ossification (Osteogenesis)

The process of bone formation where another tissue is replaced with osseous tissue.

Intramembranous Ossification

Bone formation occurring directly within a fibrous membrane, forming bones like the frontal bone and clavicle.

Endochondral Ossification

Bone formation occurring by replacing a hyaline cartilage model with osseous tissue, forming most long bones.

Primary Ossification Center

The first site of bone formation in endochondral ossification, located in the diaphysis.

Secondary Ossification Centers

Sites of bone formation in the epiphyses during endochondral ossification.

Longitudinal Bone Growth (Interstitial Growth)

The mechanism by which bones increase in length, occurring at the epiphyseal growth plates through chondrocyte division and ossification.

Appositional Bone Growth

The mechanism by which bones increase in width, involving osteoblasts producing new bone superficially and osteoclasts breaking down bone internally.

Growth Hormone

A hormone secreted by the anterior pituitary gland that stimulates both longitudinal and appositional bone growth.

Gigantism

A condition resulting from excessive growth hormone signaling during childhood, leading to abnormally increased height.

Acromegaly

A condition resulting from excessive growth hormone levels after epiphyseal plate closure, leading to stimulated appositional growth, particularly in the jaws and hands.

Bone Remodeling

A continuous process of bone formation by osteoblasts and bone resorption by osteoclasts, maintaining bone structure, repairing damage, and adapting to stress.

Wolff's Law

The principle that bone adapts and strengthens in areas that experience the most mechanical stress.

Osteoporosis

A reduction in bone mass and density, leading to fragile bones prone to fracturing, often due to osteoclast activity exceeding osteoblast activity.

Kyphosis (Hunchback)

An exaggerated thoracic spinal curvature, often seen in individuals with osteoporosis due to vertebral compression.

Vitamin D

Essential for the absorption of calcium from the diet, produced in the skin upon UVB exposure or obtained from fortified foods and supplements.

Rickets

A childhood disorder caused by insufficient calcium to strengthen bones, leading to weak and bending bones.

Simple (Closed) Fracture

A bone fracture that does not break through the surface of the skin.

Open (Compound) Fracture

A bone fracture where a bone fragment tears through the skin surface, carrying a higher risk of infection.

Transverse Fracture

A fracture where the break is 90 degrees relative to the length of the bone.

Spiral Fracture

A fracture caused by a twisting motion, pulling bone segments apart.

Comminuted Fracture

A fracture with several breaks, resulting in numerous small bone fragments between two larger pieces.

Impacted Fracture

A fracture where one bone fragment is driven forcefully into another.

Greenstick Fracture

A fracture where only one side of the bone is broken, and the other side bends, more common in children due to bone flexibility.

Compression Fracture

A fracture where the bone is crushed, typically affecting vertebrae and common in osteoporosis.

Avulsion Fracture

A fracture where a tendon or ligament tears a fragment of bone away from the main bone.

Fracture Hematoma

The initial blood clot formed at a fracture site to stabilize bone fragments, occurring immediately after the break.

Callus (Fracture Repair)

A mass of fibrous connective tissue and cartilage that forms to stabilize bone fragments during the early stages of fracture healing.

Hard Callus

The ossified callus, primarily made of spongy bone, formed during fracture repair after the initial soft callus.

Malunion

A condition where a fractured bone heals in an abnormal shape due to incorrect setting or alignment.

Bisphosphonates

A class of drugs (e.g., Fosamax, Boniva) used to inhibit osteoclast activity, often prescribed for osteoporosis.

Forteo

A form of parathyroid hormone that, when injected, paradoxically stimulates osteoblast activity and new bone formation.