Transcript “Dem Bones” are Machines

Gordon Engle
Tim Evans
Sandra Thompson
August 4, 1999
“Dem Bones” are Levers
Classes of levers
 Radius and ulna are levers
 Force is applied by muscles

Classes of levers
– First class levers have the fulcrum between
the weight and the force.
– The ulna is a first class lever.
Classes of levers
– Second class levers have the weight
between the fulcrum and the force.
– Where is an example of a second class
lever in the body?
Classes of levers
– Third class levers have the force between
the fulcrum and the weight.
– The radius is a third class lever.
The force is applied by
muscles.

In the arm the biceps brachii and the
triceps brachii work in opposition to
each other to flex and extend the
forearm.
Biceps brachii

The origin is the name for the
attachment to the bone that doesn’t
move.
– Long head is attached to the supraglenoid
tubercle and glenohumeral labrum.
– Short head is attached to the tip of the
coracoid process of the scapula.
Biceps brachii

The insertion is the name for the
attachment to the bone that does
move.
– Radial tuberosity
– Bicipital aponeurosis
Triceps brachii

Origin
– Long head attaches to the infraglenoid
tubercle of the scapula.
– Lateral head attaches to the upper half of
the posterior surface of the shaft of the
humerus, and the upper part of the lateral
intermuscular septum.
– Medial head attaches to the posterior shaft
of the humerus and lateral intermuscular
septum
Triceps brachii

Insertion
– Posterior surface of the olecranon process
of the ulna
– Deep fascia of the antebrachium
“Dem Bones” are Levers
Classes of levers
 Radius and ulna are levers
 Force is applied by muscles
