Body systems understanding the human body.

Nervous System

Principle parts: The CNS (brain and spinal cord), peripheral nervous system ( nerves which originate from the spinal cord).

Primary function: To collect information, interpret it and produce output or action.

Circulatory System

Principle parts: Heart, blood vessels, blood

Primary function: responsible for the flow of blood, nutrients and gases.

Digestive System

Principle parts: Mouth, salivary glands, pharynx, esophagus, stomach, small intestine, large intestine, rectum

Primary function: Breakdown of food and its absorption.

Skeletal System

Principle parts: Bones, cartilage, ligaments

Primary function: To provide support and movement of the body.

Excretory system

Principle parts: Kidneys, liver, large intestine, Ureter, Urethra, urinary bladder

Primary function: To get rid of waste materials of the body.

Endocrine System

Principle parts: Pituitary, hypothalamus, thyroid, adrenals, ovaries, testes, parathyroids

Primary function: Regulate the activities of cells or organs, sexual development, production of various hormones.

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.