Human Skeleton Overview

Overview

This lecture covers the structure and classification of the human skeleton, highlighting major bones and their groupings, as well as key differences between adults and babies.

Human Skeleton Overview

• Adults have 206 bones; babies start with 270 bones that fuse as they grow.
• The skeleton is divided into two main zones: axial and appendicular skeletons.

Axial Skeleton

• The axial skeleton includes the skull, vertebral column, and rib cage.
• The cranium surrounds and protects the brain.
• The mandible (jawbone) enables mouth movement for talking.
• Ossicles (malleus, incus, stapes) are three tiny bones in the ear that amplify sound.
• The rib cage protects the lungs and heart, with 12 ribs on each side and the sternum in front.
• The vertebral column consists of cervical (neck), thoracic (chest), lumbar (lower back), sacral (pelvic), and coccyx (tailbone) vertebrae.
• Five sacral vertebrae fuse to form the sacrum; the coccyx is the remnant tailbone.

Appendicular Skeleton

• The appendicular skeleton contains 126 bones in the shoulders, arms, hips, and legs.
• The scapula (shoulder blade) and clavicle (collarbone) form the shoulder.
• The arm contains the humerus (upper arm), ulna, and radius (forearm).
• Each hand and wrist contain 54 bones: carpals (wrist), metacarpals (palm), and phalanges (fingers).
• Phalanges are divided into proximal, intermediate, and distal segments.
• The hip bone is made up of the ilium, ischium, and pubis.
• The leg consists of the femur (thigh), patella (kneecap), tibia, and fibula (lower leg).
• Each foot and ankle have 52 bones: tarsals (ankle), metatarsals (foot), and phalanges (toes).

Key Terms & Definitions

• Axial skeleton — Central part of skeleton, includes skull, spine, and rib cage.
• Appendicular skeleton — Bones of the limbs and girdles connecting them to the axial skeleton.
• Cranium — The part of the skull enclosing the brain.
• Mandible — Lower jawbone.
• Ossicles — Three small ear bones: malleus, incus, stapes.
• Vertebrae — Individual bones forming the spine.
• Scapula — Shoulder blade.
• Clavicle — Collarbone.
• Humerus — Bone of the upper arm.
• Ulna/Radius — Forearm bones.
• Carpals — Wrist bones.
• Phalanges — Finger and toe bones.
• Ilium, Ischium, Pubis — Three parts of the hip bone.
• Femur — Thigh bone.
• Patella — Kneecap.
• Tibia/Fibula — Bones of the lower leg.
• Tarsals — Ankle bones.
• Metatarsals — Foot bones.

Action Items / Next Steps

• Review diagrams of the axial and appendicular skeletons and locate each named bone.
• Memorize the number of bones in major body regions for exam preparation.