The Excretory System

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The Excretory System

The importance of the excretory system

The excretory system involves a process which removes unwanted products from the body's chemistry. In general, excretion is the process of separating wastes from the body fluids and eliminating them. Examples include the removal of carbon dioxide in the air we exhale, and unwanted nitrogen in sweat, nails and hair.

Explain the various methods of excretion in the human body

There are four (4) organ systems which are responsible for excretion:

The respiratory system helps to excrete carbon dioxide, water, and other gases when we breathe. The integumentary system also excretes some water in addition to inorganic salts, lactic acid, and urea in the sweat. The digestive system not only eliminates food residue (which is not a process of excretion) but also excretes water, salts, carbon dioxide, lipids, bile pigments, and cholesterol. The urinary system, we will place most of our emphasis on this organ system. It excretes a wide variety of metabolic wastes, toxins, drugs, salts, water, hormones, and hydrogen.

State the position, structure and function of the large intestine as part of the excretory system

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The large intestine (or large bowel) is the part of the digestive system where waste products from the food you eat are collected and processed into faeces. The large intestine is about 1.5 m long and consists of the caecum, appendix, colon and rectum, which are distributed in the abdominal cavity.

The large intestine performs the following functions:
• reabsorbs water and maintains the fluid balance of the body • absorbs certain vitamins
• processes undigested material (fibre)
• stores waste before it is eliminated.

State the position, structure and function of the urinary system

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The urinary system removes a type of waste called urea from your blood. Urea is produced when foods containing protein, such as meat, poultry, and certain vegetables, are broken down in the body. Urea is carried in the bloodstream to the kidneys. Once the blood enters the kidneys the filtering process begins. Water and other substances, such as amino acids, glucose and waste products (urea and uric acid) are removed from the blood. This process is performed by microscopic structured within the kidneys known as nephrons. Each kidney contains over one million nephrons. The filtered blood moves through tiny blood vessels called capillaries, in the nephrons and exits the kidneys through the Renal Vein. The substances which are extracted from the blood during the filtering process move through a tube in the nephron, called the renal tubule. (The two kidneys contain about 16 km of tubules.) Those substances which are useful to the body, such as water, salt, glucose and amino acids are reabsorbed into the blood through the capillaries. Just enough water and salt are reabsorbed to give the blood its correct composition. The unwanted substances, such as urea, uric acid, excess water and salt remain in the renal tubule and eventually pass into the ureters. (The ureters are approximately 25 to 30 cm (10 to 12 in) long and about 0.5 cm (0.2 in) in diameter.) The waste products form what is known as urine. It moves along the ureters into the bladder where it is eventually expelled from the body, via the urethra.

The urinary excretory system performs one of the most important operations in which the kidneys play a significant role. Should the kidney not be able to perform this critical function, the results would be contamination of the blood.

State the position and importance/ function of the kidneys, detailing their blood supply

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There are two kidneys, one on either side of the spine under the lower ribs. They are pink in colour and shaped like kidney beans. Each kidney is about the size of your clenched fist. The Kidney is the main part of the excretory system it filters all of the blood that comes...
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