bones and joints

• Skeletal System

  Bones and Joints
• Functions of Bone and Skeletal System

  • Support
  • Protection
  • Assistance in Movement
  • Mineral Homeostasis
  • Blood Cell Production
  • Triglyceride Storage
• Metaphyses

  Contains an epiphyseal (growth) plate, a layer of hyaline cartilage that allows the diaphysis of the bone to grow in length
• Articular cartilage

  Covers part of the epiphysis where the bone forms an articulation (joint) with another bone, reduces friction and absorbs shock at freely movable joints
• Periosteum

  Tough connective tissue sheath surrounds the bone surface wherever it is not covered by articular cartilage
• Bone tissue

  • Matrix is 15% water, 30% collagen fibers and 55% crystallised mineral salts
  • Most abundant mineral salt is calcium phosphate
  • Deposited in the framework formed by the collagen fibres, as they crystallize the tissue hardens - calcification
  • Hardness due to crystallized inorganic mineral salts, flexibility due to collagen fibres
  • 4 types of cells in bone tissue
• Sections through the diaphysis of a long bone, from the surrounding periosteum on the right, to compact bone in the middle, to spongy bone and the medullary cavity on the left. The inset at the upper right shows an osteocyte in a bone lacuna.
• Factors affecting bone growth

  • Minerals
  • Vitamins
  • Hormones
• Calcium homeostasis

  • Release of calcium from bone matrix and retention of calcium by the kidneys are the two main ways that blood calcium level can be increased
  • Bone helps buffer calcium levels by releasing Ca2+ (osteoclasts) and absorbing Ca2+ (osteoblasts)
• Parathyroid Hormone (PTH)

  Secreted by parathyroid glands, ↑ blood Ca2+ via negative feedback
• Calcitonin (CT)

  Secreted by parafollicular cells of thyroid, ↓ blood Ca2+ by inhibiting osteoclast activity and enhancing osteoblast activity
• Calcitrol

  Is active form of Vitamin D and ↑ Ca2+ absorption from food in gut to ↑ blood Ca2+
• Divisions of the Skeletal System

  • Axial skeleton
  • Appendicular skeleton
• Axial skeleton

  Consists of bones arranged along the longitudinal axis of the body, composed of 80 bones
• Appendicular skeleton

  Consists of 126 bones in the upper and lower extremities (limbs), pectoral (shoulder) and pelvic (hip) girdles
• Together, the bones, muscles, and joints form an integrated system called the musculoskeletal system
• The branch of medical science concerned with the prevention or correction of disorders of the musculoskeletal system is called orthopedics
• Types of Bones

  • Long
  • Short
  • Flat
  • Irregular
  • Sesamoid
• Skull

  Composed of 22 bones, consists of the cranial bones (cranium) and the facial bones (face)
• General Features of the Skull

  • Forms the large cranial cavity and smaller cavities (nasal, eye sockets)
  • Certain skull bones contain mucous membrane lined cavities called paranasal sinuses
  • The only moveable bone of the skull, other than the ear ossicles within the temporal bones, is the mandible
  • Immovable joints called sutures hold the skull bones together
• General Functions of the Skull

  • Protecting and stabilising the position of the brain, blood vessels and nerves
  • Site of attachment for muscles that move the head and generate facial expressions
  • Support for the entrances to the digestive and respiratory systems and special sense organs
  • Supports the tongue, providing attachment sites for some tongue muscles and for muscles of the neck and pharynx
  • Helps to keep the larynx (voice box) open at all times
• The hyoid bone is examined at post mortem if strangulation suspected
• Vertebral Column

  26 vertebrae, Five vertebral regions: 7 cervical, 12 thoracic, 5 lumbar, 1 sacrum (5 fused), 1 coccyx (4 fused)
• Intervertebral Discs

  Absorb vertical shock, Permit various movements of the vertebral column, Fibrocartilaginous ring with a pulpy center
• Normal Curves of the Vertebral Column

  Primary curves (thoracic and sacral) formed during foetal development, Secondary curves (cervical and lumbar) formed when infant raises head at 4 months and sits up & begins to walk at 1 year
• Spinal Deformities

  • Scoliosis (lateral bending)
  • Kyphosis (exaggerated thoracic curve)
  • Lordosis (exaggeration of lumbar curve)
• Sternum

  Located in the center of the thoracic wall
• Ribs

  Twelve pairs of ribs, give structural support to the sides of the thoracic cavity, Costal cartilages contribute to the elasticity of the thoracic cage
• Pectoral Girdle

  Attaches the bones of the upper limbs to the axial skeleton
• Pelvic Girdle

  Consists of two hip bones which join the sacrum posteriorly and meet anteriorly at the pubic symphysis, Allows attachment the bones of the lower limbs to the axial skeleton
• Male versus Female Pelves

  Differences in shape and size
• Types of Synovial Joints

  • Planar Joints (Intertarsal joints)
  • Hinge Joints (knee/elbow)
  • Pivot Joints
  • Condyloid Joints (wrist)
  • Saddle Joints (Thumb)
  • Ball-and-Socket Joints (shoulder/hip)
• You should now be familiar with: Structure and function of bone, Histology of bone tissue, Types of bones, Divisions of the skeletal system, Types of joints