Overview
This lecture covers the bones of the axial and appendicular skeletons, their functions, main anatomical structures, and important terminology, focusing on key bones, markings, and joints.
Skeleton Organization
- The human skeleton is divided into axial (central structures) and appendicular (girdles and limbs) parts.
- The skeleton includes bones, cartilage, and ligaments.
Axial Skeleton: Skull
- Axial skeleton has 80 bones: skull, vertebral column, and thoracic cage.
- Skull is divided into cranial bones (protect brain) and facial bones (form face structure).
- Cranial bones (8 total): 1 frontal, 1 occipital, 2 parietal, 2 temporal, 1 sphenoid (keystone), 1 ethmoid.
- Sutures are immovable joints in the skull (coronal, sagittal, lambdoid, squamous).
- Facial bones (14): include mandible (only movable skull bone), maxillae (keystone of facial bones), nasal, zygomatic, lacrimal, palatine, vomer, inferior nasal conchae.
- Orbits are formed by 7 bones; nasal cavity and septum involve ethmoid, vomer, cartilage, and others.
- Sinuses are air-filled cavities in frontal, sphenoid, ethmoid, and maxillary bones to lighten the skull.
Axial Skeleton: Vertebral Column
- Vertebral column sections: cervical (7), thoracic (12), lumbar (5), sacrum (5 fused), coccyx (3–5 fused).
- Normal curves: cervical/lumbar (concave), thoracic/sacral (convex).
- Abnormal curvatures: scoliosis (lateral), kyphosis (hunchback), lordosis (swayback).
- Intervertebral discs (fibrocartilage) allow movement and absorb shock.
- Key vertebrae: C1 (atlas, nod 'yes'), C2 (axis, shake 'no').
Axial Skeleton: Thoracic Cage
- Thoracic cage: sternum (manubrium, body, xiphoid process) and 12 rib pairs.
- Ribs: 1–7 are true ribs (direct cartilage attachment), 8–12 are false ribs, with 11–12 called floating ribs (no anterior attachment).
- Ribs articulate posteriorly with vertebrae and anteriorly with sternum or cartilage.
Appendicular Skeleton: Girdles and Limbs
- Pectoral girdle: clavicle and scapula, attaches upper limbs.
- Upper limb: humerus, radius (thumb side), ulna (pinky side), carpal (wrist, 8 bones), metacarpals (palm), phalanges (fingers).
- Pelvic girdle: two coxal bones and sacrum.
- Differences: female pelvis is wider and flatter for childbirth.
- Lower limb: femur (largest bone, thigh), tibia (shin, bears weight), fibula (lateral, supports ankle), tarsals (ankle, 7 bones), metatarsals (foot), phalanges (toes).
- Infant skeleton: fontanelles (soft spots), sutures close as child matures.
Key Terms & Definitions
- Axial skeleton — central part of skeleton (skull, vertebral column, thoracic cage).
- Appendicular skeleton — limbs and girdles attaching to axial skeleton.
- Suture — immovable joint between skull bones.
- Foramen — opening in a bone for nerves/blood vessels.
- Process — projection or bump on a bone for attachment.
- Articulation — where two bones meet/touch.
- Keystone bone — a bone that articulates with all others in a region (e.g., sphenoid in cranium, maxilla in face).
- Fontanelle — soft spot on baby’s skull where sutures haven’t fused.
- Intervertebral disc — fibrocartilage pad between vertebrae for cushioning.
Action Items / Next Steps
- Study and memorize names, locations, and key features of bones and bone markings discussed.
- Review diagrams in slides for visual identification.
- Prepare for the next chapter on joints (Chapter 8).