Support and movement

• True endoskeleton is restricted to vertebrates only
• Human skeleton weighs about 18% of body weight
• Longest and strongest bone is the Femur
• Smallest bone is the Auditory ossicles
• Weakest bone is the Clavicle
• Osteoblasts divide and form more osteoblasts
• Osteoblasts release liquid protein called collagen
• Osteoblasts differentiate into osteocytes when totally immersed in collagen
• Osteocytes deposit calcium on collagen
• Bone-eating cells are responsible for demineralisation of bones
• Bone-dissolving cells
• Outer layer of cartilage is Perichondrium
• Inner layer of cartilage is Endochondrium
• Vesicles containing chondrocyte are called Lacunae
• Blood vessels are only running outside cartilage, so transport of material takes place through diffusion
• Repairing process in cartilage is very slow
• Types of cartilage:

  • Hyaline cartilage: found at the end of long bones, nose, larynx, and trachea
  • Fibrocartilage: found in intervertebral discs and knee cartilage
  • Elastic cartilage: found in ear flaps and epiglottis
• Types of joints:

  • Fibrous joints: immovable or fixed, e.g., sutures in the skull
  • Cartilaginous joints: allow little movement, e.g., Costovertebral joints
  • Synovial joints: freely movable joints, e.g., ball and socket joint
• Disorders of the skeletal system:

  • Microcephaly: small-sized head, mental retardation
  • Cleft lip and palate: gap between side of upper lip and palate
  • Osteoporosis: postmenopausal, lower levels of estrogen, bones become porous and easily fracture
  • Rickets: deficiency of calcium and vitamin D
  • Osteomalacia: in adults, bones of hind limb become bow-like
• Injuries to joints:

  • Dislocation of joints affects tendons and ligaments
  • Sprain: injury of ligaments without dislocation
  • Fracture: breaking of bone, usually due to an injury
• Repair of fractured bone:

  1. Hematoma and clot formation
  2. Fibrocartilaginous callus formation
  3. Replacement of cartilaginous callus with bony callus
  4. Remodeling: callus gets hard and shapes up in line with bone
• Muscle is a contractile connective tissue that can reduce its length and regain its original length
• About 50% of body weight is due to muscles
• There are more than 600 muscles in our body
• Types of muscles:

  • Smooth
  • Cardiac
  • Skeletal
• Structure of skeletal muscles:

  • Epimysium (covering whole muscle)
  • Perimysium (covering fascicle)
  • Endomysium (covering muscle fibers)
• Structure of skeletal muscles:

  • Muscle cell: Muscle fiber (cylindrical, elongated)
  • Cell membrane: Sarcolemma
  • Cytoplasm: Sarcoplasm
  • Endoplasmic reticulum: Sarcoplasmic reticulum (stores calcium ions)
• Structure of skeletal muscles:

  • Myofibril structure
  • Invaginations of sarcolemma: T-tubules
  • Sarcolemma has nerve endings attached to it called neuromuscular junction
• Necessities of muscle contraction:

  • Neurotransmitter: Acetylcholine
  • Ca+2
  • Energy
• Respiration:

  • Creatine phosphate/Phosphocreatine
  • Aerobic respiration produces 36 ATP
  • Anaerobic respiration produces 2 ATP
• Antagonistic muscles are a pair of muscles producing opposite effects upon contraction
• Disorders of muscles:

  • Muscle fatigue: due to anaerobic respiration and accumulation of lactic acid
  • Cramp: muscle pull, muscle remains in a contracted state
  • Tetany: involuntary contractions of voluntary muscles
  • Tetanus: bacterial infection by Clostridium tetani
• All or none response: extent of muscle contraction depends on the number of motor units involved