6-10

Diaphysis

Shaft of a long bone; contains the medullary cavity.

Epiphysis

The ends of a long bone; contain mostly spongy bone.

Periosteum

Outer connective tissue membrane covering bone; contains blood vessels and nerves.

Perforating fibers

Collagen fibers that anchor the periosteum to the bone matrix.

Medullary cavity

Hollow cavity inside the diaphysis that contains bone marrow.

Endosteum

Membrane lining the medullary cavity and other internal bone surfaces.

Articular cartilage

Hyaline cartilage covering the ends of bones at joints; reduces friction.

Compact bone

Hard, dense outer bone that resists compression, bending, and twisting.

Spongy bone

Inner honeycomb-like bone that resists forces from many directions and provides space for marrow.

Epiphyseal plate

Growth plate made of hyaline cartilage where a long bone grows in length.

Epiphyseal line

Remnant of the epiphyseal plate after longitudinal growth stops.

Red bone marrow

Produces blood cells; site of hematopoiesis.

Yellow bone marrow

Contains adipocytes and stores fat.

Long bone

Longer than wide; examples include the femur and other limb bones.

Short bone

Roughly cube-shaped; examples include wrist and ankle bones.

Flat bone

Thin and broad; examples include skull bones and pelvic bones.

Irregular bone

Has an irregular shape; example: vertebra.

Sesamoid bone

Small, flat, oval bone located within a tendon; example: patella.

Osteoblast

Builds new bone.

Osteocyte

Mature bone cell that maintains bone tissue.

Osteoclast

Breaks down/resorbs bone.

Osteon

Basic structural unit of compact bone; also called a Haversian system.

Central canal

Center of an osteon; contains blood vessels and nerves.

Concentric lamellae

Rings of bone surrounding the central canal.

Lacunae

Small spaces between lamellae that contain osteocytes.

Canaliculi

Tiny canals connecting lacunae and allowing osteocytes to communicate.

Perforating canals

Canals that connect neighboring central canals and carry blood vessels.

Trabeculae

Branching ribs/plates of spongy bone.

Compact bone histology

Recognized by circular osteons with central canals and concentric lamellae.

Spongy bone histology

Recognized by branching trabeculae and open spaces; no central canals.

Longitudinal growth

Growth that increases bone length; occurs at the epiphyseal plate.

Appositional growth

Growth that increases bone width/thickness.

Zone of reserve cartilage

Zone of the epiphyseal plate containing cells not directly involved in active growth.

Zone of proliferation

Zone where chondrocytes actively divide.

Zone of hypertrophy and maturation

Zone where chondrocytes enlarge and mature.

Zone of calcification

Zone containing dead chondrocytes and calcified cartilage.

Zone of ossification

Zone where osteoblasts build bone on the calcified cartilage.

Osteoporosis

A condition in which bone resorption exceeds bone formation, causing decreased bone mass and weaker bones.

Bone remodeling

Continuous process of bone formation and bone resorption.

Osteoporosis mechanism

Osteoclast activity/bone resorption becomes greater than osteoblast activity/bone formation.

Fetal skull

Skull with membranous areas where ossification is incomplete.

Fontanels

Soft spots in a fetal skull that allow flexibility during birth and remain until about 18–24 months.

Anterior fontanel

Fontanel between the developing frontal and parietal bones.

Posterior fontanel

Fontanel between the developing parietal and occipital bones.

Sphenoid fontanels

Fontanels located near the temples where the sphenoid meets other cranial bones.

Mastoid fontanels

Fontanels at the junction of the lambdoid and squamous sutures.

Adult vs fetal skull

Fetal skull has fontanels and incomplete ossification; adult skull has completed ossification and fused sutures.

Cervical curvature

Normal spinal curvature that is concave.

Thoracic curvature

Normal spinal curvature that is convex.

Lumbar curvature

Normal spinal curvature that is concave.

Sacral curvature

Normal spinal curvature that is convex.

Primary spinal curvatures

Thoracic and sacral curvatures; present during the fetal period.

Secondary spinal curvatures

Cervical and lumbar curvatures; develop after the fetal period.

Scoliosis

Abnormal lateral spinal curvature that may appear C- or S-shaped.

Lordosis

Exaggerated cervical and lumbar curvatures; commonly called swayback.

Kyphosis

Abnormally exaggerated thoracic curvature.

Fibrous joint

Joint where bones are connected by dense connective tissue.

Cartilaginous joint

Joint where bones are connected by cartilage.

Synovial joint

Joint with a joint cavity that allows substantial movement.

Synarthrosis

Functionally immovable joint.

Amphiarthrosis

Functionally slightly movable joint.

Diarthrosis

Functionally freely movable joint.

Plane joint

Nonaxial synovial joint; flat surfaces glide against each other.

Hinge joint

Uniaxial joint allowing mainly flexion and extension.

Pivot joint

Uniaxial joint allowing rotation around an axis.

Condylar/ellipsoid joint

Biaxial joint with an oval convex surface fitting into a shallow concave surface.

Saddle joint

Biaxial joint where both articulating surfaces have convex and concave regions.

Ball-and-socket joint

Multiaxial joint where a ball-shaped surface fits into a socket.

Flexion

Movement that decreases the angle between bones.

Extension

Movement that increases the angle between bones.

Hyperextension

Extension beyond the anatomical position.

Abduction

Movement away from the body's midline.

Adduction

Movement toward the body's midline.

Circumduction

Circular movement combining flexion, extension, abduction, and adduction.

Rotation

Movement in which a bone rotates around its longitudinal axis.

Supination

Rotation of the forearm so the palm faces anteriorly.

Pronation

Rotation of the forearm so the palm faces posteriorly.

Dorsiflexion

Movement that brings the top of the foot toward the shin.

Plantarflexion

Movement that points the foot downward.

Inversion

Turning the sole of the foot medially.

Eversion

Turning the sole of the foot laterally.

Opposition

Movement of the thumb toward the fingers.

Reposition

Movement returning the thumb from opposition.

Elevation

Raising a body part.

Depression

Lowering a body part.

Articular capsule

Double-layered capsule surrounding a synovial joint.

Fibrous layer

Outer layer of the articular capsule made of dense irregular connective tissue.

Synovial membrane

Inner layer of the articular capsule that secretes synovial fluid.

Synovial fluid

Lubricates the joint, provides nutrients, removes wastes, and absorbs shock.

Articular cartilage

Hyaline cartilage covering exposed articulating bone surfaces.

Ligament

Connects bone to bone and helps stabilize joints.

Tendon

Connects muscle to bone.

Bursa

Synovial-fluid-filled structure that reduces friction.

Muscle fiber

A skeletal muscle cell.

Endomysium

Connective tissue surrounding an individual muscle fiber.

Fascicle

Bundle of muscle fibers surrounded by perimysium.

Perimysium

Connective tissue surrounding a fascicle.

Epimysium

Connective tissue surrounding the entire muscle.

Fascia

Most superficial connective tissue surrounding muscle.

Tendon

Structure connecting muscle to bone or another structure.