Skeletal System

• it consist of three main types of tissues;
• muscles
• bones
• cartilage

Functions of the skeletal system

• protection
• Support
• Muscle attachment
• movement
• storage of calcium
• blood cells formation

Main types of skeletal system;

• exoskeleton in insects
• its functions include support, attachment of muscle for movement, protection and prevent water loss
• endoskeletons in vertebrates(eg humans)

• its functions include support, protection and movement

 

Skeleton of Humans

• it is divided into three parts:
• Axial skeleton-skull, back bone and ribs
• Appendicular skeleton-limbs
• Girdles-hip and shoulder girder

Bones

Pectoral girdle- shoulder

CONSIST OF;

• Shoulder
• a triangular, flat bone witha shallow cavity on narrower end. It joins the arm tto the axial skeleton.
• The collar bone

• it prevents the shoulder from bending inward.
• Arm – upper and lower arm
• Ulna and radius

• ulna is longer and thicker than radius
• has cavity where part of humorous fitted to make a hinge joint
• ulna has an extended bone
• Humorous

• A long bone with a rounded head-epiphysis and a long central shaft-endophysis
• Shallow cavity

• lose attachment oof the shoulder bone with the back side of ribs

 

Joints

Is a connection between two or more joints. They provide articulation between bones making movement possible.

Types of joints

Gliding joint

• e.g joints which occur between the vertebrate wrists and ankles
• the ends of the bones that make the joint are covered with cartilage
• they are held together by tough ligaments

 

Synovial joint

• it is enclosed by fibrous capsule lined by synovial membrane which secretes synovial fluid into the synovial cavity
• the synovial fluid lubricates the joint
• they include hinge and ball and socket joints

 

Hinge joint

• eg knee joint
• it allows movement in one plane, ball and socket joint
• eg hip joint;
• it allows rotation in all directions

ELBOW

Role of muscles in movement of human arm

Muscles that bring about movement are antagonistic i.e when one set contracts the other relaxes

• Movement of the hinge joint of an arm
• moving arm upwards(biceps flexor) muscle contract whilst triceps muscle relax
• straightening the arm, biceps muscle relaxes whilst the triceps(extensor) muscle contract

 

Antagonistic muscle of human forelimb

 

• the biceps muscles of the forelimb act as flexors while the triceps muscle act as extensors
• the biceps has its points of origin on the scapula and the point of insertion on the radius
• the triceps has its point of origin on the scapula and humorous and is inserted on the ulna
• when the muscles contract, the limb act as a lever with the pivot at the joint
• contraction of biceps muscles bends the arms while contractions of triceps extend the arm