Skeletal System

• Functions:

  • Framework and support: the skeleton provides a scaffold to support the weight of the rest of the body.
  • Movement: Muscles are attached to the skeleton. When they contract, movement takes place. Articulation (bone meets bone - joint) allows varying degrees of movement.
  • Protection of vital organs: the skull encloses the brain, the vertebrae enclose the spinal cord, the heart and lungs are protected by the ribcage.
  • Storage: fat stored in yellow marrow and mineral salts stored in matric
  • Red blood cell production - in red marrow.
• Bones

  • 206 bones in the human body
  • Appendicular bones make up the upper and lower limbs and pectoral and pelvic girdle.
  • Axial bones line around the central axis of the body.
  • Main support for upright posture
  • Protects central nervous system and organs in thorax
  • Skull, vertebrae, ribs and sternum.
• Bone


  A connective tissue
• Osteocytes


  • Bone cells
  • Surrounded by a matrix of calcium and other organic salts
• Microscopic Structure - Compact Bone

  • Compact bone consist of many similar units called Osteons/Haversian systems
  • Central canal - center of each osteon. Contains a blood capillary, nerve and lymph capillary.
  • Lamellae - concentric layers of bony matrix
  • Lacunae - spaces between lamellae
  • Osteocyte - bone cells in each lacunae
  • Canaliculi - tiny canals running between lacunae. They are connected to enable exchange of materials between cells
• Types of bone cells

  • Osteoblasts - build matrix
  • Osteoclasts - break down bone when the body needs more organic salts
• Microscopic Structure - Spongy Bone

  • Irregular arrangement of thin bony plates called trabeculae.
  • Osteocytes occupy spaces in trabeculae
  • Nerves and blood vessels passes through irregular spaces in the matrix.
• Diaphysis


  Shaft/main portion of the long bone
• Cartilage

  • Connective tissue
  • Matrix called chondrin with collagen fibres embedded
  • Chondroblast (cartilage cells) is spaces in the matrix
  • They produce matrix until they are surrounded by it. Cells are then mature and known as chrondocytes
• Epiphysis


  Enlarged ends covered by articular cartilage
• Cartilage Types

  • Hyaline - many closely packed collagen fibres that are very fine.
  • Strength and flexibility
  • Trachea and bronchi
  • Elastic - contains elastic fibres and collagen fibres that are not so tightly packed.
  • Flexibility and elastic
  • Outer ear
  • Fibrocartilage - parallel bundles of thick collagen fibres loosely packed.
  • Can be compressed and able to withstand heavy pressure
  • Invertebral discs and knee joint.
• Articular cartilage


  Covers bone that is articulating with another bone in a joint
• Compact bone


  Hollow cylinder
• Blood supply

  • Perichondrium - Fibrous membrane of connective tissue that covers the external surface of cartilage (except on articular surfaces). 
  • Contains blood vessels
  • Cartilage itself does not contain blood vessels so nutrient diffuse through the matrix.
• Osteoporosis

  • Loss of bone mass to impair normal functioning
  • Bone density decreases and risk of fractures increase
  • Prevention
  • Adequate calcium and vitamin D intake.
  • Exercise
  • Treatment
  • Lifestyle changes (increase calcium, vitamin D and exercise)
  • Quit smoking
  • Medication
  • Weight bearing exercise.
• Yellow bone marrow cavity

  Fat storage site
• Osteoarthritis

  • Gradual change in joints over time
  • Cartilage deteriorates so bone surfaces aren't protected.
  • Bones wear away and growths may form, limiting joint mobility 
  • Caused by ageing, joint irritation and wear/abrasion
  • Symptoms - pain and stiffness in joints
  • Treatment
  • Medication to relieve pain
  • Physiotherapy to strengthen muscles
  • Surgery/joint replacements.