Skeletal System

Divisions of the Skeleton

• Axial skeleton consists of 74 bones that form the upright axis of the body and 6 tiny middle ear bones

• Appendicular skeleton consists of 126 bones that form the shoulder girdles, arms, wrists, and hands and the hip girdles, legs, ankles and feet.

Axial Skeleton

The Skull

• 28 irregularly shaped bones

• Two major divisions– Cranium (brain case)

• 8 bones• All cranial bones are unpaired except for the

parietal and temporal bones

– Face• 14 bones • All of the face bones are paired except the mandible

and vomer

Hyoid Bone

• Single U-shaped bone in neck

• Just above the voice box

• Only bone in the body that does not articulate with any other bones

Vertebral Column

• Longitudinal axis of the skeleton

• 24 vertebrae, sacrum and coccyx

• Forward, backward and sideways movement

Vertebral Column

• 7 Cervical vertebrae (neck)

• 12 Thoracic vertebrae

• 5 Lumbar vertebrae (small of the back)

• Sacrum (5 separate vertebrae that are fused in adults)

• Coccyx (4 or 5 fused vertebrae)

Atlas and Axis

Atlas• First cervical

vertebrae

• Supports the skull

Axis• Second cervical

vertebrae

• Dens joins axis to atlas

•Atlas and axis allow the head to turn from side to side

Sternum

• Consists of three bones– Manubrium – Body – Xiphoid Process

Ribs

• Protect the vital organs of the torso

• Ribs one through seven connect directly to the sternum (true ribs)

• Ribs eight through 10 connect to costal cartilage (false ribs)

• Ribs 11 and 12 only connect to the back (floating ribs)

Ribs and Sternum

Appendicular Skeleton

Shoulder Girdle (Pectoral Girdle)

Bones of the Arm (Anterior View)

Bones of the Arm (Posterior View)

Bones of the Hand

The Pelvic Girdle

• Supports the trunk and attaches the lower extremities

• In early life each coxal bone is made up of three separate bones which later fuse to form one large bone– Ilium – Ischium– Pubis

Right Coxal Bone

The Female

Pelvis

• Male Pelvis is deep and funnel shaped with a narrow subpubic angle

• Female pelvis is shallow, broad, and flaring with a wider subpubic angle

The Foot

Bone Fractures

• Partial or complete break in the continuity of a bone

• Open fracture (compound fracture) the broken bone projects through the skin

• Closed fracture (simple fracture) does not break the skin

Bone Fractures

Abnormal Spine Curvatures

Curvatures

• a. Lordosis – “sway back”

• b. Kyphosis – “rounded back”

• c. Scoliosis - “ lateral – sideways”

Spine Curvature

• Convex through the thoracic region

• Concave through the lumbar region

• scoliosis