The human rib cage consists of 12 pairs (24 ribs total): True ribs (1-7): 7 pairs - directly attached to sternum via costal cartilage. False ribs (8-10): 3 pairs - attached to the cartilage of the 7th rib (not directly to sternum). Floating ribs (11-12): 2 pairs - not attached to sternum at all. The rib cage protects the heart, lungs, and major blood vessels and assists in breathing.

Osteology is the scientific study of bones and the skeletal system. Related terms: Arthrology = study of joints, Myology = study of muscles, Orthopaedics = medical specialty dealing with bone and joint disorders, Rheumatology = study of joint and autoimmune diseases, Osteitis = inflammation of bone. Osteology is important in anatomy, anthropology, forensic science, and palaeontology.

Bones are primarily composed of Calcium phosphate in the form of Hydroxyapatite [Ca10(PO4)6(OH)2], which gives bones their hardness and rigidity. Bone composition: Inorganic (mineral) component = ~65-70% (mainly hydroxyapatite). Organic component = ~30-35% (mainly collagen fibres - Type I collagen) that provide flexibility and tensile strength. The combination of hard minerals and flexible collagen makes bone both strong and slightly flexible.

Red Bone Marrow is the site of haematopoiesis - the production of all blood cells including RBCs, WBCs, and platelets. In adults, red bone marrow is found in flat bones such as the sternum, ribs, skull, pelvis, and vertebrae, and at the ends (epiphyses) of long bones. Yellow Bone Marrow (found in the shaft of long bones) is primarily a fat storage tissue but can convert to red marrow during severe blood loss.

The knee joint is a hinge joint - it allows movement in one plane only (flexion and extension), like the hinge of a door. Types of synovial joints: Ball and socket (Hip, Shoulder - movement in all directions), Hinge (Knee, Elbow, Ankle - flexion/extension only), Pivot (Neck atlas-axis - rotation only), Gliding (Wrist carpal bones - sliding movement), Saddle (Thumb carpometacarpal - biaxial movement), Condyloid (Wrist joint - biaxial movement).

The hip joint is a ball and socket joint - the rounded head of the femur (ball) fits into the cup-shaped acetabulum of the pelvis (socket). This joint allows movement in all directions - flexion, extension, abduction, adduction, and rotation. The shoulder joint is also a ball and socket joint and is the most mobile joint in the body. Ball and socket joints are multiaxial joints.

Cartilage is a smooth, flexible connective tissue that reduces friction between articulating bone surfaces in joints, acts as a shock absorber (especially in the knee - meniscus), provides smooth surface for joint movement, and forms the growth plate (epiphyseal plate) in children. Types: Hyaline (joint surfaces, trachea), Fibrocartilage (intervertebral discs, knee meniscus), Elastic (ear, epiglottis). Cartilage has no blood supply - heals very slowly when damaged.

Ligaments are tough, fibrous connective tissue bands that connect bone to bone at joints, providing stability and limiting excessive movement. They are composed mainly of collagen fibres. Ligament = Bone to Bone (mnemonic: Ligament = Locks bones together). Tendon = Muscle to Bone (mnemonic: Tendon = connects muscle To bone). Cartilage = Cushions between bones. Ligament injuries (sprains) are common in the knee and ankle joints.

The Appendicular Skeleton (126 bones) consists of: Pectoral (shoulder) girdle = Clavicle + Scapula (x2 each) = 4 bones. Upper limbs = Humerus, Radius, Ulna, 27 hand bones (x2) = 60 bones. Pelvic girdle = Hip bones (x2, each formed by Ilium+Ischium+Pubis) = 2 bones. Lower limbs = Femur, Patella, Tibia, Fibula, 26 foot bones (x2) = 60 bones. Total = 4 + 60 + 2 + 60 = 126 bones.

Scoliosis is an abnormal lateral (sideways) curvature of the spine, often S-shaped or C-shaped when viewed from behind. Types: Idiopathic scoliosis (most common, cause unknown - typically appears during adolescence), Congenital scoliosis (present at birth), and Neuromuscular scoliosis (due to muscle/nerve conditions). Other spinal deformities: Kyphosis = excessive forward rounding of upper back (hunchback), Lordosis = excessive inward curve of lower back (swayback). Severe scoliosis may require bracing or surgery.