Bones of the Upper Limb & Pectoral Girdle 💪

  • Pectoral girdle connects arms to the body. Each half has:
    • 🔹 Clavicle (collar bone): Long, slender, curved bone
    • 🔹 Scapula: Large triangular flat bone between ribs 2-7. Features:
      • → Spine ridge → Acromion (clavicle attaches here)
      • → Glenoid cavity (socket for humerus)
  • Arm bones (see Figure 17.9):
    • Humerus (upper arm)
    • Radius & Ulna (forearm)
    • Carpals (8 wrist bones)
    • Metacarpals (5 palm bones)
    • Phalanges (14 finger bones)

Bones of the Lower Limb & Pelvic Girdle 🦵

  • Pelvic girdle has two coxal bones (each fused from 3 bones):
    • Ilium + Ischium + Pubis
    • 🔹 Meet at pubic symphysis (fibrous cartilage joint)
    • 🔹 Acetabulum: Cup-like cavity where thigh bone attaches
  • Leg bones (see Figure 17.10):
    • Femur (longest bone!)
    • Tibia & Fibula
    • Patella (knee cap, covers knee ventrally)
    • Tarsals (7 ankle bones)
    • Metatarsals (5 foot bones)
    • Phalanges (14 toe bones)

Joints: Where Movement Happens! 🏃‍♂️

Joints are contact points between bones/cartilage. Muscles use joints as fulcrums to move bones.

3 Joint Types:

  1. Fibrous Joints:
    • ❌ No movement allowed!
    • Example: Skull sutures (dense fibrous tissue)
  2. Cartilaginous Joints:
    • 🔄 Limited movement
    • Example: Between vertebrae (joined by cartilage)
  3. Synovial Joints (most movable!):
    • 💧 Have fluid-filled cavity for smooth movement
    • Examples:
      • → Ball & socket: Shoulder (humerus + pectoral girdle)
      • → Hinge: Knee
      • → Pivot: Neck (atlas + axis vertebrae)
      • → Gliding: Between carpals
      • → Saddle: Thumb (carpal + metacarpal)

Muscle & Skeleton Disorders ⚠️

  • Myasthenia gravis: Autoimmune → muscle fatigue/paralysis
  • Muscular dystrophy: Genetic → progressive muscle damage
  • Tetany: Low Ca++ → muscle spasms
  • Arthritis: Joint inflammation
  • Osteoporosis: Low bone mass → fractures (common in low estrogen)
  • Gout: Uric acid crystals → joint inflammation

Key Takeaways for NEET! 📌

  1. Joint Types: Fibrous (immovable), Cartilaginous (limited), Synovial (movable).
  2. Synovial Joints: Ball-socket (shoulder), Hinge (knee), Pivot (neck), Gliding (wrists), Saddle (thumb).
  3. Disorders: Myasthenia gravis (autoimmune), Tetany (low Ca++), Osteoporosis (bone loss), Gout (uric acid).
  4. Girdle Differences: Pectoral = clavicle+scapula; Pelvic = fused ilium/ischium/pubis.
  5. Bone Counts: Carpals (8), Tarsals (7), Metacarpals/metatarsals (5 each), Phalanges (14 per limb).

Keep revising – you’ve got this! 🌟