The lungs and respiratory system allow oxygen in the air to be taken into the body, while also letting the body get rid of carbon dioxide in the air breathed out. When you breathe in, the diaphragm moves downward toward the abdomen, and the rib muscles pull the ribs upward and outward. This makes the chest cavity bigger and pulls air through the nose or mouth into the lungs. In exhalation, the diaphragm moves upward and the chest wall muscles relax, causing the chest cavity to get smaller and push air out of respiratory system through the nose or mouth.
Every few seconds, with each inhalation, air fills a large portion of the millions of alveoli. In a process called diffusion, oxygen moves from the alveoli to the blood through the capillaries tiny blood vessels lining the alveolar walls. Once in the bloodstream, oxygen gets picked up by the hemoglobin in red blood cells.
This oxygen-rich blood then flows back to the heart, which pumps it through the arteries to oxygen-hungry tissues throughout the body.
In the tiny capillaries of the body tissues, oxygen is freed from the hemoglobin and moves into the cells. Carbon dioxide, made by the cells as they do their work, moves out of the cells into the capillaries, where most of it dissolves in the plasma of the blood.
Blood rich in carbon dioxide then returns to the heart via the veins. Solid trash and recyclables may go to the curb in a trash can, or in a recycling bin for pick up and transport to a landfill or recycling centre.
Like a busy home, your body also produces a lot of wastes that must be eliminated. Like a home, the way your body gets rid of wastes depends on the nature of the waste products. Some human body wastes are gases, some are solids, and some are in a liquid state.
Getting rid of body wastes is called excretion, and there are a number of different organs of excretion in the human body. Excretion is the process of removing wastes and excess water from the body. It is an essential process in all living things, and it is one of the major ways the human body maintains homeostasis.
It also helps prevent damage to the body. Wastes include by-products of metabolism — some of which are toxic — and other non-useful materials, such as used up and broken down components. Some of the specific waste products that must be excreted from the body include carbon dioxide from cellular respiration , ammonia and urea from protein catabolism, and uric acid from nucleic acid catabolism. Organs of excretion include the skin , liver , large intestine , lungs , and kidneys see Figure Together, these organs make up the excretory system.
Figure They include the skin, liver, large intestine, lungs, and kidneys. The skin is part of the integumentary system, but it also plays a role in excretion through the production of sweat by sweat glands in the dermis. Although the main role of sweat production is to cool the body and maintain temperature homeostasis , sweating also eliminates excess water and salts, as well as a small amount of urea. When sweating is copious, as in Figure The liver shown in Figure In addition to all of these functions, the liver is a very important organ of excretion.
The liver breaks down many substances in the blood, including toxins. For example, the liver transforms ammonia — a poisonous by-product of protein catabolism — into urea , which is filtered from the blood by the kidneys and excreted in urine. The liver also excretes in its bile the protein bilirubin , a byproduct of hemoglobin catabolism that forms when red blood cells die. Bile travels to the small intestine and is then excreted in feces by the large intestine.
The large intestine is an important part of the digestive system and the final organ in the gastrointestinal tract. As an organ of excretion, its main function is to eliminate solid wastes that remain after the digestion of food and the extraction of water from indigestible matter in food waste. All vertebrate animals produce nitrogen waste in one form or another. The type of waste that is produced depends on where and how the animal lives.
Read on to find out more! Jerboas are desert mammals. In urination, Hormone control over excretion occurs in the distal tubules of the kidneys as directed by the hypothalamus. Most mammals excrete nitrogenous wastes in the form of urea , an ancestral trait.
Birds excrete their nitrogenous wastes as uric acid in the form of a paste. This is metabolically more expensive, but allows more efficient water retention and it can be stored more easily in the egg. Many avian species, especially seabirds , can also excrete salt via specialized nasal salt glands, the saline solution leaving through nostrils in the beak.
Perspiration is another excretory process which removes salts and water, although the primary purpose is cooling. In insects , a system involving Malpighian tubules is utilized to excrete metabolic waste. Metabolic waste diffuses or is actively transported into the tubule, which transports the wastes to the intestines. The metabolic waste is then released from the body along with fecal stuffs.
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