Homeostasis: An Overview of the Nutrients and Transport Functions

For a living thing to maintain homeostasis, each cell must be supplied with food, water, oxygen, and must be constantly free of toxic metabolic wastes. Therefore, the human being is composed of intricate body systems that allow these cells to function. By working together, they carry out the life processes of nutrition, transportation, respiration, regulation, reproduction, and locomotion. The systems are made up organ systems, which are made of many organs, which are made of tissues, which are finally made of cells.

In order for nutrition, the function in which we obtain materials for energy, growth and repair, and other life functions, we have the digestive system. In this, food materials are broken down into molecular products chemically and mechanically. First, the food is ingested through the oral cavity, breaking it down mechanically by chewing and chemically by saliva, an enzyme. Next, the food is swallowed by peristalsis, a wave of muscular contractions, in the esophagus, a tube that connects the oral cavity to the stomach. The stomach is a muscular organ used to liquefy and further digest foods. The stomach is lined with digestive enzymes and hydrochloric acid that make up gastric fluid. This gastric fluid works best in an acidic condition. Liquefied and digested food then enters the small intestine. Enzymes, such as protease, lipase, maltese, and sucrase are used to complete digestion. The lining of the small intestine, villi, is used to absorb end products of digestion. Villi contain capillaries and lacteals, extensions of the lymphatic system that dissolve and distribute nutrients. Materials that have not been digested go to the large intestine. These materials, normally being liquid, are solidified into feces, which are stored in the rectum. The feces pass out of the body through peristaltic contractions. There are other organs that aid this process, known as accessory organs. The liver produces bile, which is important in the digestion of fats. The gallbladder stores this bile. The pancreas manufactures and stores digestive enzymes. The biggest mechanism of digestion is hydrolysis, which adds water in order to break down a molecule

Transport, the function which humans beings absorb and distribute materials necessary to maintain life, is carried out through the circulatory system, a series of vessels and organs designed to transport fluids throughout the body. One example is arteries, relatively thick-walled blood vessels that contain cardiac muscle tissues, enabling blood flow by rhythmic contractions called pulse. Arteries send blood away from the heart. Veins are thin-walled blood vessels that bring blood toward the heart, containing one-way valves that aid the forward movement of blood. Capillaries are microscopic blood vessels that are one cell thick. Branching from arteries, they carry oxygen-rich blood to tissues. Lymph vessels form a branching series of microscopic vessels containing lymph. They carry lymph to and from body tissues and also contain valves. Places where lymph vessels become enlarged are known as lymph nodes, containing white blood cells that destroy bacteria in the lymph. The heart is a muscular pump with four chambers. The atria receive blood from veins, and the ventricles that force blood through arteries to other organs. The blood circulation can be traced from its entry of blood without oxygen into the right atrium from the vena cava, a vein. The blood passes through the right ventricle, where strong muscular contractions force the blood through pulmonary arteries into the lungs. Gas exchange occurs in capillaries, which removes CO2 from the blood. The blood with oxygen returns through the left atrium into the left ventricle, sending blood out through the aorta. This leads to capillaries where wastes are absorbed in the blood, and eventually it flows back to vena cava. The circulation of blood through the lungs is pulmonary circulation, and circulation through the organs is systemic circulation. The movement of blood through vessels is coronary circulation.

In summary, the functions of nutrient and transport are integral in order to maintain homeostasis, or keep the internal systems of the body constant.

Sources: Biology, 7th Ed. by Campbell