Date: Monday, January 12th 2015.Topic: Substances expelled by

Organisms.Objective: To learn about substances that organisms

expel.

Air Exhalation and gas exchange.

The main reason for exhalation is to rid the body of carbon dioxide, which is the waste product of gas exchange in humans. Air is brought in the body through inhalation. During this process air is taken in through the lungs. In order for the lungs to expel air the diaphragm relaxes, which pushes up on the lungs. The air then flows through the trachea then through the larynx and pharynx to the nasal cavity and oral cavity where it is expelled out of the body.

Urine Urine is a liquid by-product of the body

secreted by the kidneys through a process called urination and excreted through the urethra.

Cellular metabolism generates numerous by-products. These by-products are eventually expelled from the body during urination, the primary method for excreting water-soluble chemicals from the body.

Feces Feces are also known as excrement, is waste

product from an organism's digestive tract expelled from the body during a process called defecation.

Defecation is the final act of digestion, by which organisms eliminate solid, semisolid, and/or liquid waste material from the digestive tract.

Humans expel feces with a frequency varying from a few times daily to a few times weekly.

Waves of muscular contraction (known as peristalsis) in the walls of the colon move fecal matter through the digestive tract towards the rectum.