Musculoskeletal System

• Musculo-skeletal


  • Muscles
  • Skeleton

  
• Components of the skeletal system

  • Bones
  • Joints
  • Articulating cartilages
  • Ligaments
  • Skeletal muscle
  • Tendons
  • Ligaments
• Skeletal system


  • Axial skeleton
  • Appendicular skeleton

  
• Axial skeleton


  Includes the skull, vertebral column & thoracic cage

  
• Appendicular skeleton


  The upper & lower limb bones including those forming the pectoral and pelvic girdle

  
• Bone


  • Living tissue, most modified form of connective tissue that makes up most of the skeleton
  • Provides support for the body & its cavities
  • Provides protection of vital organs
  • Provides mechanical basis for movement
  • Stores salts
  • Supplier of new blood cells
• Bone tissue


  • Organic component (1/3)
  • Inorganic component (2/3)
  • Organic gives bone elasticity
  • Inorganic gives bone rigidity
• Bone cells


  • Osteoblasts
  • Osteocytes
  • Osteoclasts
• Osteoblasts


  • Lay down bone and form the bone matrix
  • Deposit inorganic salts & osteoid in bone tissue
• Osteocytes


  Mature bone cells that monitor & maintain the bone tissue
• Osteoclasts


  • Reabsorb bone (a process that continues lifelong)
  • Breakdown bone releasing calcium & phosphates
• Compact (cortical) bone


  • Outer dense layer which gives bone its smooth, white & solid appearance
  • Covered in dense CT called Periosteum (outer) and Endosteum on its inner surface
  • Makes up about 80% of the body bone mass
  • Composed of parallel tube-shaped units called osteons (Haversian systems)
• Spongy (cancellous) bone


  • Deep airy layer of bone which is highly vascularised
  • Highly vascularized and more metabolically active
  • Found within the ends of long bones and in the vertebrae
  • Central part houses the bone marrow, which is the site of haematopoiesis in the adults
• Classification of bones by

  • Location
  • Method of development (ossification)
  • Shape

  
• Ossification


  • The process or development of bone tissue
  • Begins before birth (in utero) and is not complete until about the 21st year of life
  • Mesenchyme develops from mesoderm & they form the embryonic skeleton
  • Cartilaginous models develop from the mesenchyme skeleton & then ossify into bone
  • Osteoblasts converge on the 'models' to ignite the ossification process
• Intramembranous ossification


  • Mesenchymal models of bone undergoes ossification without an intermediate cartilage model being formed
  • Usually flat bones
  • Ossification usually begins around the 6th to 8th week gestation period
• Endochondral ossification


  • Cartilaginous (hyaline) models of bone formed from mesenchyme undergoes ossification
  • The model then ossifies starting in the centre of the shaft (the PRIMARY OSSIFICATION CENTRE – POC) @ 8th week gestation period
  • Ossification proceeds proximally and distally, until by birth, the shaft is ossified while the extremities are cartilaginous
  • After birth, the extremities ossify (the SECONDARY OSSIFICATION CENTRE – POC)
• Classification of bones by shape

  • Long bones
  • Short bones
  • Flat bones
  • Irregular bones
  • Sesamoid bones

  
• Long bones


  • Tubular in shape
  • Composed mostly of compact bone which is thick in the shaft (cortex) & thinner in the extremities
  • Spongy bone and bony marrow fill the ends/extremities of the bones
  • Have a diaphysis (shaft) and two epiphyses (extremities)
• Short bones


  • Roughly cuboid or round in shape
  • Contain a thin layer of compact bone surrounding the spongy bone
• Flat bones


  • Mostly thin, flattened and usually curved
  • Contain two parallel layers of compact bones surrounding a layer of spongy bone
• Irregular bones


  • Do not fit into any of the other categories
  • Generally, irregular bones contain foramina through which soft tissue and neurovascular structures pass
• Sesamoid bones


  • Small, rounded unique types of bones that are embedded in muscle tendons where the tendon passes over a joint
  • The largest sesamoid bone in the body is the patella
• Blood supply to bones

  • Periosteal artery
  • Nutrient artery
  • Methaphyseal artery
  • Epiphysial artery
• Hematopoiesis


  • The production of all of the cellular components of blood and blood plasma
  • Occurs during embryonic development and throughout adulthood to produce and replenish the blood system
  • Most blood cells are produced within the marrow of the bone – there are 2 types: RED MARROW & YELLOW MARROW
• Red marrow


  Responsible for blood cell production
• Yellow marrow


  Composed mostly of fat and resides in the hollow centers of long bones, such as thigh bones
• At birth = all marrow is red – produces more blood
• Adults = red and yellow marrow is equal
• Red marrow bones = spine, sternum, ribs, pelvis (high concentrations)
• Production: red blood cells = 200 billion; white blood cells = 10 billion; platelets = 400 billion each day
• Fracture


  • A breakage in bone due to injury/stress or disease
  • Can be simple, compound, comminute, incomplete
• Cartilage


  • Flexible connective tissue found in multiple organ systems of the body
  • Composed of specialized cells called chondrocytes, collagen fibres & abundant ground substance rich in proteoglycan and elastin fibres
• Types of cartilage


  • Hyaline cartilage
  • Elastic cartilage
  • Fibro cartilage
• Hyaline cartilage


  Most abundant of the cartilages and is found in joints, as well as the nose, larynx, trachea and ribs
• Elastic cartilage


  Similar to hyaline but contains more elastic fibres. Found in the epiglottis
• Fibro cartilage


  Composed of collagen fibre type I and ground substance. Found in intervertebral discs & pubic symphysis
• Joint


  • A connection or union of 2 or more bones or cartilages
  • The study of joints is known as ARTHROLOGY
• Classification of joints


  • To be covered later
• Fracture


  Breakage in bone due to injury/stress or disease