The Skeletal System - Bones & Joints PDF

THE SKELETAL SYSTEM - Bones & Joints Dr. P. De Gabriele MD MMCFD DipWH(ICGP) The Skeleton Axial skeleton – the bones that form the longitudinal axis of the body Appendicular skeleton – the bones of the limbs and girdles Joints Cartilages Ligaments FUNCTIONS OF BONES...

THE SKELETAL SYSTEM - Bones & Joints Dr. P. De Gabriele MD MMCFD DipWH(ICGP) The Skeleton Axial skeleton – the bones that form the longitudinal axis of the body Appendicular skeleton – the bones of the limbs and girdles Joints Cartilages Ligaments FUNCTIONS OF BONES SUPPORT – all soft organs – The bones of the legs support the body trunk when we stand. – The rib cage supports the thoracic wall. PROTECTION – Bones protect soft body organs. MOVEMENT – Skeletal muscles are attached to bones by tendons that act as levers to move the body and its parts. STORAGE – Fat is stored in the internal cavities of bones. – A store for minerals such as calcium and phosphorus. BLOOD CELL FORMATION – Red cell formation occurs within the marrow cavities of certain bones. CLASSIFICATION OF BONES Compact bone – dense tissue and looks smooth and homogeneous Spongy bone – made up of small needlelike pieces of bone and lots of open space CLASSIFICATION OF BONES Long Bones – A shaft with heads at both ends made up mostly of compact bone e.g. Bones of the limbs except ankle and wrist bones Short Bones – Cube-shaped and contain mostly spongy bone e.g. Bones of the wrist and ankle Flat Bones – Thin, flattened and usually curved. They have 2 layers of compact bone sandwiching a layer of spongy bone between them. e.g. Most bones of the skull, the ribs and the sternum Irregular Bones – Any bones which do not fit the above descriptions e.g. Vertebrae, Hip Bones  LONG BONES (1) Diaphysis – the shaft of a long bone – It makes up most of the bone’s length. – It is composed of compact bone. – It is covered and protected by a fibrous connective tissue membrane – the periosteum. – Hundreds of connective tissue fibres, called perforating or Sharpey’s fibres, secure the periosteum to the underlying bone. Epiphyses – the ends of the long bone – Each epiphysis consists of a thin layer of compact bone enclosing an area filled with spongy bone. – Articular cartilage covers its external surface. Epiphyseal line – a remnant of the epiphyseal plate found in young, growing bone Medullary cavity – a storage area for adipose tissue – It is called the yellow marrow. – In infants, this area forms red blood cells and red marrow is found there.  LONG BONES (2) Basic unit of compact bone is the osteon (Haversian system) Each osteon consists of: Lamellae – concentric rings of hard, intercellular substance Lacunae – small spaces between lamellae that contain osteocytes Canaliculi – radiating minute canals that provide numerous routes so that nutrients can reach the osteocytes and wastes can be removed from them Central (Haversian) canal – contains blood vessels and nerves Bone Formation, Growth & Remodelling In an embryo, the skeleton is primarily made of hyaline cartilage. In a young child, most of the cartilage has been replaced by bone except in isolated areas – the bridge of the nose – parts of the ribs – The articular cartilages remain for life reducing friction at joint surfaces. – The epiphyseal plates provide for longitudinal growth of the long bones during childhood. Bone Formation, Growth & Remodelling The process of bone formation is called ossification. It is made up of 2 phases: – Osteoblasts completely cover the hyaline cartilage with bone matrix. – The enclosed cartilage model is digested away, opening up a medullary cavity within the newly formed bone. Bone Formation Bone Remodeling Essential if bones are to retain normal proportions and strength during long- bone growth Crucial so that bones become thicker and form large projections to increase their strength in areas where bulky muscles are attached BONE FRACTURES Bone breakages are called fractures. A fracture in which the bone breaks cleanly but does not penetrate the skin is a closed fracture. When the skin is penetrated, the fracture is open or compound. Types of Fractures Fracture Healing FUNCTIONS OF JOINTS They hold the bones together securely. They give the rigid skeleton mobility. Functional Classification of Joints Synarthroses – immovable joints Amphiarthroses – slightly movable joints Diarthroses – freely movable joints Structural Classification of Joints Fibrous Joints – immovable joints Cartilaginous Joints Synovial Joints - freely movable joints FIBROUS JOINTS In these joints, the bones are united by fibrous tissue. – Sutures of the skull. In sutures, the irregular edges of the bones interlock and are bound tightly together by connective tissue fibres, allowing essentially no movement to occur. CARTILAGINOUS JOINTS In these joints, the bones are connected by cartilage. – Pubic symphysis – Intervertebral joints. SYNOVIAL JOINTS Articular Cartilage Fibrous articular capsule Joint cavity Reinforcing ligaments