Skeletal System

Axial Skeleton

The portion of the skeleton that forms the body's longitudinal axis; includes the skull, vertebral column, and thoracic cage.

Appendicular Skeleton

The portion of the skeleton that includes the limbs and the pectoral and pelvic girdles.

Function of Bones -Support

Forms the body's framework and supports soft organs.

Function of Bones: Protection

Protects vital organs such as the brain, heart, and lungs.

Function of Bones: Movement

Bones act as levers for muscles to produce movement.

Function of Bones:Storage

Stores calcium, phosphorus, and fat (yellow marrow).

Function of Bones:Blood Cell Formation

Hematopoiesis; blood cells are produced in bone marrow.

Hematopoiesis

The process of blood cell formation.

Compact Bone

Dense, smooth, and homogeneous bone tissue.

Spongy Bone

Lightweight bone made of trabeculae (needle-like structures) with open spaces.

Long Bone

Longer than wide; mostly compact bone; found in limbs.

Short Bone

Cube-shaped bones composed mostly of spongy bone.

Flat Bone

Thin bones with spongy bone sandwiched between compact bone

Irregular Bone

Bones with complex shapes that don't fit other categories.

Diaphysis

The shaft of a long bone.

Epiphysis

The ends of a long bone containing spongy bone.

Periosteum

Tough connective tissue covering the outside of bone.

Sharpey's Fibers

Fibers that anchor the periosteum to the bone.

Articular Cartilage

Hyaline cartilage covering the ends of bones at joints.

Epiphyseal Plate

Growth plate responsible for bone lengthening during childhood.

Epiphyseal Line

Adult remnant of the epiphyseal plate.

Endosteum

Membrane lining the medullary cavity.

Medullary Cavity

Central cavity of a long bone containing marrow.

Yellow Marrow

Fat storage found in the medullary cavity of adults.

Red Marrow

Site of blood cell production.

Osteocyte

Mature bone cell found in lacunae.

Lacuna

Small cavity that houses an osteocyte.

Haversian Canal

Central canal containing blood vessels and nerves.

Osteon

Structural unit of compact bone.

Canaliculi

Tiny canals connecting osteocytes for nutrient exchange.

Volkmann's Canals

Perforating canals connecting Haversian canals.

Ossification

The process of bone formation.

Osteoblast

Bone-building cell.

Osteoclast

Bone-destroying cell responsible for bone resorption.

Bone Remodeling

The continuous process of bone breakdown and formation.

Parathyroid Hormone (PTH)

Hormone that stimulates osteoclasts to raise blood calcium.

Hypercalcemia

Excess calcium in the blood.

Closed Fracture

A fracture where the skin remains intact.

Open Fracture

A fracture where the bone breaks through the skin.

Reduction

Realignment of fractured bone ends.

Bone Healing Phase 1

Hematoma formation.

Bone Healing Phase 2

Fibrocartilage callus formation.

Bone Healing Phase 3

Bony callus formation.

Bone Healing Phase 4

Bone remodeling.

Hematoma

A blood-filled swelling at a fracture site.

Fibrocartilage Callus

Temporary repair tissue that stabilizes a fracture.

Bony Callus

Spongy bone replacing the fibrocartilage callus.

Axial Skeleton Divisions

Skull, vertebral column, and thoracic cage.

Cranium

Protects the brain.

Facial Bones

Hold eyes in position and provide attachment for facial muscles.

Sutures

Immovable joints between skull bones.

Mandible

The only freely movable bone of the skull.

Number of Cranial Bones

8.

Number of Facial Bones

14.

Paranasal Sinuses

Hollow spaces that lighten the skull and amplify voice.

Hyoid Bone

Only bone that does not articulate with another bone.

Function of Hyoid Bone

Supports the tongue and aids in swallowing and speech.

Vertebral Column Function

Supports the body and protects the spinal cord.

Number of Vertebrae (Adult)

26 vertebral bones.

Cervical Vertebrae

7 vertebrae in the neck.

Thoracic Vertebrae

12 vertebrae in the chest.

Lumbar Vertebrae

5 vertebrae in the lower back.

Sacrum

Fused bone formed from 5 vertebrae.

Coccyx

Fused bone formed from 3-5 vertebrae.

Primary Curvatures

Thoracic and sacral curves present at birth.

Secondary Curvatures

Cervical and lumbar curves that develop after birth.

Body (Centrum)

Weight-bearing portion of a vertebra.

Vertebral Foramen

Opening through which the spinal cord passes.

Spinous Process

Posterior projection for muscle attachment.

Transverse Process

Lateral projections for muscle and ligament attachment.

Thoracic Cage

Consists of sternum, ribs, and thoracic vertebrae.

True Ribs

Pairs 1-7; directly attach to the sternum.

False Ribs

Pairs 8-12; indirectly or do not attach to the sternum.

Floating Ribs

Pairs 11-12; no anterior attachment.

Sternum Parts

Manubrium, body, xiphoid process.

Intervertebral Disc

Cartilage cushion between vertebrae.

Annulus Fibrosus

Tough outer ring of an intervertebral disc.

Nucleus Pulposus

Gel-like center of an intervertebral disc.

Disc Herniation

Protrusion of the nucleus pulposus through the annulus fibrosus.

Pectoral Girdle

Consists of the clavicle and scapula.

Clavicle

Collarbone connecting the upper limb to the trunk.

Scapula

Shoulder blade.

Humerus

Bone of the upper arm.

Ulna

Medial forearm bone in anatomical position.

Radius

Lateral forearm bone in anatomical position.

Carpals

8 wrist bones.

Metacarpals

5 palm bones.

Phalanges (Hand)

14 bones in each hand.

Pelvic Girdle

Formed by two coxal bones and the sacrum.

Coxal Bone

Composed of the ilium, ischium, and pubis.

Pelvis

Two coxal bones, sacrum, and coccyx.

Function of Pelvis

Supports body weight and protects pelvic organs.

Female Pelvis

Larger inlet, wider outlet, broader pubic arch.

Femur

The longest, heaviest, and strongest bone in the body.

Acetabulum

Hip socket where the femur articulates.

Tibia

Larger, medial lower leg bone.

Fibula

Smaller, lateral lower leg bone.

Medial Malleolus

Inner ankle projection on the tibia.

Lateral Malleolus

Outer ankle projection on the fibula.

Tarsals

7 ankle bones.