Skeleton + Muscles

• Functions of Skeleton: 1. Support: gives shape + provides framework to support weight of the body

  
  

  2. Attachment: provides point of attachment for muscles + tendons

  
  

  3. Movement: when these muscles contract, they allow movement

  
  

  4. Protection: of vital body organs; cranium + brain, rib cage + lungs

  
  

  5. Storage: for minerals, salts and fats.

  - Calcium, Phosphorus, Sodium and Potassium

  Can be released and distributed to other parts

  of body when needed (i.e. pregnancy)

  
  

  6. RBC production: in RBM of spongy bone

  - Red bone marrow contains blood stem cells

  which can differentiate into blood cells.
• Divisions of Skeleton (2)

  - axial

  - appendicular
• Axial Skeleton Contains (3): - Bones of skull: cranium, face, mandible

  - Vertebrae: cervical, thoracic, lumbar, sacrum, coccyx

  - Ribs + Sternum
• Appendicular Skeleton Contains (4): - Upper limbs - Humerus, Ulna, Radius, Carpals,

  Metacarpals & Phalanges

  - Lower limb - Femur, Patella, Tibia, Fibula, Tarsals,

  Metatarsals & Phalanges

  - Pectoral (shoulder) girdle - Clavicle & Scapula

  - Pelvic (hip) girdle - Pelvis
• Types of Bones (5): - Long: longer than they are wide

  eg. all limb bones - phalanges

  
  

  - Short: cube-shaped

  eg. carpals + tarsals

  
  

  - Flat: thin and flat, often curved

  eg. cranium, sternum, scapula, ribs

  
  

  - Irregular: complicated shapes

  eg. vertebrae and coccyx

  
  

  - Sesamoid: embedded within a muscle or tendon

  eg. patella
• Parts of the Spine (5): cervical, thoracic, lumbar, sacrum, coccyx
• Vertebral body


  weight bearing component of vertebrae
• Vertebral Arch: helps form an enclosed hole (foremen magnum), the spinal cord
• Transverse Process: point of attachment for muscles that help move the vertebrae as well as ligaments that stabilise the vertebral column
• Spinous Process: point of attachment for muscles that help move the vertebrae as well as ligaments that stabilise the vertebral column
• Atlas (C1): the first cervical vertebrae

  - holds up the world

  - carries your head
• Axis (C2): the second cervical vertebrae

  - forms the pivot upon which the first vertebra (Atlas - carries the head) rotates
• Cervical vertebrae: lightest in the spine; allow for neck's flexibility and head's range of motion

  - 7 vertebrae
• Thoracic vertebrae: middle segment of the spine; form part of the thoracic cage

  - 12 vertebrae
• Lumbar vertebrae: lower back region; weight bearing of upper body

  - 5 vertebrae
• Bones of the Pelvis (4): - Iliac crest

  - Ilium

  - Pubis

  - Ischium
• Rib Cage (function): protects internal thoracic organs + role in ventilation; moving during chest expansion to enable lung inflation
• Types of Ribs (3): - True ribs (1-7): articulate (join) with the sternum via their own piece of costal cartilage

  - False ribs (8-10): share a single piece of costal cartilage

  - Floating ribs (11-12): have no articulation with the sternum
• Bones of Skull (9): Consists of 22 bones in most adults; come together via cranial sutures

  - Nasal, Frontal, Parietal, Occipital, Temporal, Sphenoid, Zygomatic, Maxilla, Mandible
• Structure of a Long Bone (8): epiphysis, diaphysis, compact bone, spongy bone, medullary cavity, periosteum, articular cartilage, epiphyseal lines
• Epiphysis (2): - Enlarged ends of bones

  - Compact bone of outside surrounding spongy bone
• Diaphysis (2): - Main shaft of bone

  - Hollow cylinder of compact bone surrounding a cavity
• Compact Bone (3): - Outside 'border' of a bone

  - Very dense + rigid, filled with tiny holes that hold blood vessels

  - Protects spongy bone and bone marrow
• Spongy Bone: - On inside of compact bone

  - More porous than compact bone + has large spaces filled with RBM, where RBC production takes place (flat + long bones)
• Medullary Cavity


  Filled with Yellow Bone marrow (fat/lipid storage)
• Periosteum: dense, white, fibrous covering on outside of bone for strength + rigidity; richly supplied with blood vessels and nerves
• Epiphyseal Lines


  bone growth areas in children
• Microscopic Structure of Bone (2): Bone is a CONNECTIVE TISSUE

  - cells are separated from each other by large amounts of non-cellular material called MATRIX

  
  

  - Inorganic salts are deposited in the matrix of bones which increase strength and rigidity
• Osteon: structural unit of compact bone

  - run parallel to the long axis of the bone to give its strength
• Central canal: centre channel of each osteon

  - Contains blood capillaries, nerves and lymph
• Lamellae


  concentric layers of bony matrix which surround canal
• Lacunae


  small spaces in the matrix between lamellae
• Canaliculi


  tiny canals that run between Lacunae
• Osteocyte: a bone cell which occupies each Lacunae; projections enter the canaliculi and make contact with other bone cells so materials can be passed from cell → cell
• Trabeculae: irregular, thin, bony plates; found in spongy bone

  - Lamellae not arranged in concentric layers → they are irregular

  - Osteocytes still found in Lacunae

  - Nerves and blood vessels pass through irregular spaces in the matrix
• Ossification


  process of bone formation
• Process of Bone Growth (4): - Cartilage undergoes calcification through the deposition of calcium salts

  - Cartilage cells die → replaced by osteoblasts; promoting more deposition of calcium salts

  - Osteoblasts mature into osteocytes

  - Bone formation continues until only a small band of cartilage remains; remnants of area this are known as epiphyseal lines, when the bone stops growing
• Bone cells responsible for regulation of Calcium Concentration (2): - Osteoblasts

  - Osteoclasts
• Osteoblasts: form bone by promoting deposition of calcium salts into matrix (absorbing calcium = lowering blood calcium levels)
• Osteoclasts: reabsorb bone by secreting enzymes that dissolve the matrix, which release the stored minerals (releasing calcium into the bloodstream).