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Summary The Excretory System
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A summary on the Excretory System
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Overview of the Excretory SystemThe excretory system helps maintain homeostasis by regulating various variables
affected by everyday activities. For example:
● The pH of your blood can be changed by the foods you consume.
● Exercise-induced perspiration can alter the osmotic pressure of your blood.
● Stress can impact the hormones that target cells in the kidneys.
The excretory system plays a crucial role in restoring these variables to a normal range.
Functions of the Excretory System
Excretion is the process of separating and eliminating wastes from body fluids. The
excretory system primarily excretes metabolic wastes dissolved in solution. It
accomplishes this by producing urine in the kidneys and expelling it from the body.
The excretory system serves four main functions:
1. Excretion of metabolic waste: This includes nitrogenous wastes such as
ammonia, urea, and uric acid.
2. Maintenance of water-salt balance: It regulates blood pressure and also controls
the levels of potassium (K+), bicarbonate (HCO3-), and calcium (Ca2+).
3. Maintenance of acid-base balance: The system helps maintain the blood pH (7.4)
by excreting hydrogen ions ([H+]) and reabsorbing bicarbonate ions ([HCO3-]).
4. Secretion of hormones: The excretory system secretes hormones such as
calcitriol (active form of vitamin D that promotes calcium absorption) and
erythropoietin (stimulates red blood cell production in response to increased
oxygen demands).
Organs of the Excretory System
The main organ of the excretory system is the kidney. Here's an overview of how it
functions:
● Unfiltered blood enters the kidney through the renal arteries.
● Filtered blood is returned to the heart via the renal veins.
● Waste materials are filtered out and collected in the kidney's ducts, then
transported to the bladder through the ureters.
● When approximately 400ml of urine is stored in the bladder, receptors are
activated, sending a signal to the brain, resulting in urination.
The Kidneys
Each kidney consists of three regions:
● Renal Cortex: The outer layer that encircles the kidney.
● Renal Medulla: The inner layer with shaped tissue masses.
● Renal Pelvis: A hollow space that is continuous with the ureter.
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