Wednesday, May 4, 2011

Your thirst and hunger centers tell you that you are dehydrated and hungry. You decide a cold water and chicken wings will satisfy such desires. You need to reach for your frosty beverage on the counter directly in front of you. Your starting point should be anatomical position. Specify the movements, muscles, bones, and joints involved in reaching for the glass and bringing it to your mouth.

The upper arm is moved by the muscles of the shoulder girdle; the lower arm is moved by muscles of the upper arm; and the fingers are moved by muscles of the lower arm. Raising the arm from the anatomic position to reach a glass on the table is a gliding movement at the synovial shoulder joint. This is extension and abduction. The bone of the upper arm – the humerus, articulates with the scapula at the shoulder joint. Muscles of the thorax and shoulder move the humerus: the deltoid contracts and pulls the deltoid tuberosity of the humerus, then the trapezius muscle further lifts the arm; teres major and latissimus dorsi contract pulling the intertubercular groove of the humerus. The shoulder ball-and-socket joint extends. Humerus articulates with radius and ulna at elbow joint. To extend the arm at the elbow joint, triceps brachii contracts, biceps brachii relaxes, to pull the tuberosity of the radius, and supinator muscle pulls the surface of the radius: This supinates the hinge synovial elbow joint. To reach the glass on the table in front, pronator teres and quadratus contract, and the hand executes a pronation movement: the palm moves from anterior to posterior facing position. Extensor digitorum contracts to extend the phalanges of the fingers. To grab the glass, thenar and hypothenar muscles contract to pull the metacarpals and phalanges that flex at the carpometacarpal ellipsoidal joints, which work quite similar to a ball-and-socket joint, allowing angular motion in two planes – along or across the length of an oval. The thumb moves in opposition to grasp the glass. To bring the glass to the mouth, while the metacarpals and phalanges remained flexed to hold the glass, to flex the arm at the elbow joint, biceps brachii contract and triceps brachii relax, while muscles of the thorax and shoulder move the humerus.


Coleman, D. (Director). (2005). Anatomy for beginners: Lesson 3, Digestion. (Reality TV Show). United Kingdom.

Tortora, G.J., Derrickson B. (2010).  Introduction to the Human Body:  The Essentials of Anatomy and Physiology (8th Ed.).  Hoboken, NJ: John Wiley & Sons, Inc. 

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