AP skeletal system

• what does the skeletal system provide ?

  protection, support, movement
• how many bones are there ?

  it depends on age ,

  350 in infants

  214 in adults

  
• bones in the human body

  
• the skeleton is divided into two parts :

  axial and appendicular
• axial


  the 80 bones

  
• appendicular skeleton


  134 bones

  
• what are joints ?


  where two or more bones meet
• what are joints held by?

  ligaments
• what is joint movement controlled by?

  muscles and tendons
• what are the three types of joints ?

  fibrous, cartilaginous, synovial

  
• firbous joints


  - immovable-sutures- found in pelvis and skull-syndesmosis- found in distal tibia and fibula
• cartilaginous joints


  semi-movable joints joined by cartilage

  
• synovial joints


  freely movable joints
• types of bone


  long, short, flat, irregular, sesamoid

  
• long bones


  UEx - Upper extremity

  LEx- Lower extremity

  these include

  - tibia

  - femur

  - ulna

  - metatarsals

  - phalanges ( both foot and hand )

  - metacarpals

  - clavicles

  - Humerus

  - Rduis

  
• Short bones


  Numerous bones in the wrist and ankles

  - Carpals

  - tarsals

  
• Flat bones


  - rib cage

  - skull

  - scapula

  - pelvis

  
• irregular bones


  vertebrae and facial bones and heel

  
• sesamoid bones


  free floating bones in certain tendons such as the patella and in the foot and hand

  
• what are the functions of bones ?

  support, protection, framework, movement, storage, blood cell formation
• function of bones : protection


  bones provide vital organs such as the brain , heard and lungs by bones like the skull and rib cage

  the axial skeleton bones surrounds and protects these organs
• function of the bone : Framework

  muscles and organs are attached and supported by the skeleton
• function of bone: Movement


  - the muscular system works with the skeletal system to enable movement

  - the perpendicular skeleton provides movement

  - muscles attach to bones through tendons

  - where muscles pull on bone they form lumps ( tibial tuberosity)
• function of bone : storage of minerals and nutrients

  - calcium is important sustenance in the body -controlled at 2.4mmol/L- the body needs to control calcium at tight levels because its involved inskeletal , smooth and cardiac muscle contractionandblood clottingand transmission ofnerve impulses- bones serve as large reservoirs ,99% of calcium is stored in the bones and teeth and 1% is stored inthe extracellular fluid
• Calcium homestasis is regulated by three hormones

  - calcitonin - removes Ca out of the blood

  - Parathyroid hormone - puts Ca into the blood

  - Vitamin D - absorbed Ca
• Calcitonin and PTH


  - low blood calcium levels triggers PTH to act on osetoblasts to reabsorb bone to release calcium

  - high calcium levels triggers release of calcitonin fromparafollicular cells to act on osteoclasts to build bone

  
• Vitamin D


  - increases calcium absorption
• structure of long bones : Epiphysis


  - found at the end of bones

  - made of spongy ( cancellous bone

  - contain red marrow - red marrow is responsible for the synthesis of red , white blood cells and platelets

  
• structure of long bone : Diaphysis


  - shaft of a long bone

  - made of compact bone - coats the entire bone

  - Contains yellow marrow

  
• structure of bone : Metaphysis


  - region between epiphysis and diaphysis- where theepiphysial plateis

  
• structure of bone : Periosteum

  - covers the entire bone except the joints

  
• structure of bone : cartilage

  - tough and smooth and provides a reduces friction surface when movement
• structure of bone : blood supply


  - bone has very good blood supply

  - the diaphysis has a single nutrient artery bringing the blood to it

  - there are 2 epiphysial arteries , two at the top and two at the bottom

  
• structure of bone : Nerve supply


  - bone is highly sensitive

  - nerve supply enters bone with the nutrient artery and then branches of making a network

  
• properties of bone


  - bone must be hard but lightweight

  - bone must be flexible but rigid

  bone must be adaptable - must be able to build and release calcium

  - bone is turned over every 7-8 years

  
• bone : hard but lightweight

  two types of bone :

  - compact ( cortical bone )

  - spongy ( cancellous bone)
• compact bone


  - makes up 80% of the bone mass- mature adult compact bone is made ofstrong lamellar bone ( rings of the bone)- these rings create cylindrical structures calledosteons-osteonsare the basic structural unit of compact bone- osteons consists of concentric layers of lamellae ( thin layer membrane ) surronding a centralhaversian canelthat contains blood vessels

  
• Cavities between the lamellar where osteocytes sit are called :

  Lacunae

  
• spongy bone


  - spongy bones from a hollow network of bones called turbeculae- these contain the red marrow- the red marrow is the site of Haematopoiesos ( production of blood cells)- turbeculae being hollow makes the bone lightweight- it also provides a large surface area
• flexible but rigid


  - bone is a type ofconnective tissue- made of 30% flexible organic matter- made of 70% rigid non-organic matterhence why its both flexible and rigid