Chapter 7: Skeletal System

Mineral storage

Bones store minerals like calcium and help maintain homeostasis through regulated secretion.

Hematopoiesis

Blood formation; stem cells in red marrow produce erythrocytes, leukocytes, and thrombocytes.

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___% of bone is organic; includes ECM (collagen) and living cells, providing flexibility.

65

__% of bone is inorganic; mineral salts that provide strength and durability.

Ossification

The process by which cartilage is replaced by minerals to form bone.

Fontanel

The soft spot on a baby's head where ossification is incomplete.

Diaphysis

The hollow shaft of a long bone composed of compact bone.

Epiphysis

The rounded end of a long bone containing spongy bone and red marrow.

Medullary canal (cavity)

The hollow area within the diaphysis containing yellow marrow.

Endosteum

The lining of the medullary canal that maintains its structure.

Yellow marrow

Fat cells, blood vessels, and stem cells that form leukocytes.

Haversian canals

Small canals in compact bone that supply nutrients to osteocytes.

Periosteum

The fibrous outer covering of bone involved in repair, growth, and nutrition.

Articular cartilage

Hyaline cartilage at bone ends that provides smooth movement and shock absorption.

Axial skeleton

Includes the skull, vertebral column, and thoracic cage.

Cranium

Flat bones that protect and support the brain, eyes, ears, nose, and mouth.

Suture

Connective tissue bands that hold infant cranial bones together.

Frontal bone

part of cranium that forms forehead

Temporal bones

parts of cranium forming sides of head

Parietal bone

part of cranium forming top of head

Occipital bones

part of cranium forming back of head

Ethmoid

Bone between the eyes inside the socket.

Sphenoid

Temple bone that connects with all other cranial bones.

Nasal bones

Two bones forming the bridge of the nose.

Vomer

Bone forming the lower nasal septum.

Inferior concha

Side walls of the nasal cavity.

Maxillae

Upper jaw bones.

Lacrimals

Bones containing the tear ducts.

Zygomatics

Cheekbones.

Palatines

Bones forming the roof of the mouth.

Mandible

The lower jaw; only movable facial bone.

Paranasal sinuses

Air spaces in facial bones lined with mucous membranes.

Vertebral column

Irregular bones protecting the spinal cord and supporting the head and ribs.

Intervertebral discs

Fibrocartilage discs that cushion vertebrae and thin with age.

Cervical vertebrae (C1–C7)

Neck vertebrae; C1 (atlas) allows nodding, C2 (axis) allows rotation.

Thoracic vertebrae (T1–T12)

Articulate with ribs and curve posteriorly.

Lumbar vertebrae (L1–L5)

Support body weight and curve anteriorly.

Sacrum

Five fused vertebrae that articulate with the hips.

Coccyx

The tailbone, formed by four fused vertebrae.

Vertebral body

The main weight-bearing portion of a vertebra.

Vertebral foramen

The hole in a vertebra through which the spinal cord passes.

Transverse processes

Wing-like projections on a vertebra opposite the body.

Spinal process

Posterior bony projection above the foramen.

Articular processes

Projections below the spinal process that allow articulation with adjacent vertebrae.

True ribs

First seven pairs of ribs attached directly to the sternum via costal cartilage.

False ribs

Ribs 8–10 that attach to the 7th rib’s cartilage.

Floating ribs

Last two ribs with no anterior attachment.

Sternum

Breastbone made of the manubrium, body, and xiphoid process.

Manubrium

Upper part of the sternum that connects to the clavicles.

Xiphoid process

The lower cartilage portion of the sternum.

Hyoid bone

U-shaped bone in the neck that anchors the tongue.

Appendicular skeleton

Includes girdles and limbs (upper and lower appendages).

Clavicle

Collarbone; connects scapulae to sternum and braces shoulders.

Scapula

Shoulder blade; provides attachment for arm muscles.

Humerus

Upper arm bone that articulates with the scapula.

Radius

Forearm bone on the thumb side; allows rotation.

Ulna

Forearm bone on the pinky side with the olecranon (elbow).

Carpals

Eight wrist bones in two rows allowing flexibility.

Metacarpals

Palm bones; thumb metacarpal allows opposability.

Phalanges (hand)

Finger bones; three per finger, two in thumb.

Ilium

Upper, blade-like part of the hipbone.

Ischium

Rounded lower back portion of the hipbone.

Pubis

Front portion of the hipbone that joins at the symphysis pubis.

Symphysis pubis

Midline joint where pubic bones fuse.

Sacroiliac joint (SI)

Joint between the sacrum and ilium that helps with standing posture.

Obturator foramen

Large opening between pubis and ischium.

Acetabulum

Hip socket formed by fusion of ilium, ischium, and pubis.

Femur

Thigh bone; the longest and strongest bone.

Tibia

The larger, medial lower leg bone (shinbone).

Fibula

The slender lateral lower leg bone.

Patella

Kneecap; a sesamoid bone embedded in muscle.

Tarsals

Seven ankle bones including the calcaneus (heel bone).

Talus

Ankle bone that articulates with the tibia and fibula.

Metatarsals

Foot bones forming longitudinal and transverse arches.

Flat feet

Condition where foot arches collapse, causing pain.

Phalanges (foot)

Toe bones; three per toe, two in great toe.

Diarthrosis

Freely movable joint, also known as a synovial joint.

Bursa

A fluid-filled sac near joints; reduces friction and may become inflamed (bursitis).

Ball and socket joints

Joints with full range of motion (e.g., shoulder, hip).

Hinge joints

Joints that move in one direction (e.g., elbow, knee).

Pivot joints

Joints that allow rotation (e.g., radius and ulna).

Gliding joints

Joints where flat bones slide over each other (e.g., spine).

Condyloid joints

Joints that allow movement in two directions (e.g., fingers).

Saddle joints

Joints that allow movement in multiple directions (e.g., thumb base).

Amphiarthrosis

A partially movable joint (e.g., pubic symphysis).

Synarthrosis

An immovable joint (e.g., cranial sutures).

Flexion

Bending a joint to decrease the angle between bones.

Extension

Straightening a joint to increase the angle between bones.

Abduction

Movement away from the midline of the body.

Adduction

Movement toward the midline of the body.

Rotation

Circular movement around an axis; includes pronation and supination.

Circumduction

A combination of flexion, extension, abduction, and adduction.

Greenstick fracture

Incomplete fracture common in children.

Closed (simple) fracture

A complete fracture that does not break the skin.

Open (compound) fracture

A fracture where bone pierces the skin.

Comminuted fracture

Bone is shattered into multiple fragments.

Impacted fracture

One bone fragment is driven into another.

Spiral fracture

Caused by a twisting force.

Colles’ fracture

A specific wrist fracture.

Closed reduction

Non-surgical alignment of bone using manipulation and a cast or splint.