Multicellular Organisms: Regulation of the Internal Environment

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I had a nasty experience the last time I visited a hospital for a medical check-up, I saw a patient suffering from kidney disease, he was brought to the hospital for medical attention. Seeing the man laying on the sick bed, dying, I began to think about what would have been the causes of this deadly disease, is the disease curable or not? To get answers to my questions, I decided to make some finding. After my findings, I got reasonable answers to my questions and I decided to share it with you through this post.

Hope you find this post interesting

By BruceBlaus - Own work, CC BY-SA 4.0,

The cells of a multi-cellular organism are bathed in body fluids such as blood, lymph, and inter-cellular tissue fluid. These fluids make up the internal environment of the organism. The internal environment must be kept fairly constant for the health, growth and efficient functioning of the body cells. Maintaining a steady internal environment is known as homeostasis.

These conditions include temperature, PH (hydrogen ion concentration), osmotic pressure and concentrations of dissolved substances in the body fluids such as carbon dioxide, oxygen, urea, food substances (glucose, amino acids, etc).

HOMEOSTATIC PROCESSES

The control mechanisms are often used to detect and adjust the change in the internal environment of an organism. Usually, sensory detectors recognize a change in a given condition and stimulate the relevant body parts involved in control. These parts receive the signals, interpret them and send out instructions to the appropriate organs or glands to react and restore to the normal state.

There are many parts of the body that are involved in homeostasis, body parts such as the kidneys, liver, skin, and hormones (substances secreted by endocrine glands). Although these organs and hormones play an important role in homeostasis, the brain has overall control over the homeostatic processes in the body.

Kidneys help to regulate the internal environment. There are so many functions of the kidneys which are, kidney remove nitrogenous wastes which are the excretory function, and also maintain water to the salt ratio in the body system (sodium, potassium and chloride ions) which are the osmoregulatory function. The regulation mechanisms which maintain the water, salts and PH balance of the blood occur at the distal tubules and collecting ducts.

By Kes47 (?) - File:Illu capillary microcirculation.jpg, Public Domain,

Water Balance

When we drink a lot of water on a cold day, we excrete a large amount of dilute urine. On hot days we lose a lot of water from the body through sweating and excrete a small amount of concentrated urine. The kidneys regulate the excreted waste from the urine through the osmotic pressure so as to keep the blood constant.

The solute concentration of blood rises by intake of too many salts, reduction in fluid intake and loosing of body fluid through profuse sweating, which therefore resulted in an increase in osmotic pressure. This is detected by osmoreceptors in the hypothalamus in the brain. Immediately, they send a nerve impulse to stimulate the release of an anti-diuretic hormone (ADH) from the posterior pituitary gland, that is when we will begin to feel thirsty.

ADH is released to the kidney through blood where it causes an increased reabsorption of water by the tubules into the bloodstream. It does this by increasing the permeability of the distal tubules and the collecting ducts to water. The urine becomes concentrated as it volume decreases, while the blood becomes diluted, and its osmotic pressure decreases.

This process goes on until the osmotic pressure reaches its normal level. When the osmoreceptors detect a normal osmotic pressure, the stop stimulating the pituitary gland, and the secretion of ADH decreases or ceases. Less water is reabsorbed by the kidneys and the urine produced is of low concentration. The blood volume is also kept constant by this process.

Thirst is also a sensation that indicates the need for water intake to regulate the osmotic pressure of blood. Keeping the osmotic pressure constant is an example of a homeostatic process. This control mechanism is known as a negative feedback mechanism.

Polycystic kidneys

Diseases of the Kidney

There are more than a million urinary tubules in each adult human kidney. These filter the body's blood completely every 45 minutes excreting its urea and regulating its water, salt, and acid content. In a healthy adult, one kidney can cope amply with these functions. The kidneys, however, can be damaged by diseases, poisons, and physical injury. Thus it is a great asset to have two of these extremely vital organs.

Glomerular nephritis, is the kidney condition that occurs in children and adolescents, usually after a bacterial (streptococuus*) infection, like a sore throat, in some other part of the body. The glomeruli become inflamed, increasing the porosity of the membranes. This allows proteins and red blood cells to leak into the glomerular filtrate. Large numbers of white blood cells and dead tissue cells collect in the inflamed glomeruli, sometimes totally blocking the blood flow.

The Effects of Kidney Diseases

There are so many effects of kidney diseases due to impaired function. These are manifested by the following signs and symptoms; High blood urea levelthis happens which kidney function is reduced by at least 50 percent. Presence of proteins and blood cells in urine is due to theincreased porosity of membranes in the glomeruli and Bowman's capsule. Impaired ability to produce sufficient urineis occurs when the glomerular filtration rate is reduced, and when the tubules are blocked or damaged.

By OpenStax College - Autonomic Reflexes and Homeostasis , CC BY 3.0,

Kidney stones are stony masses of minerals and organic matter that form in kidneys. They are produced when mineral salts in urine come out of solution as solid crystals. This may occur when the intake of water is low; the salt intake is high, or the urine is abnormally acidic or alkaline.

Kidney stones vary in size from tiny sand-like grains or large masses which can completely fill the renal pelvis. Large stones may block the flow of urine and cause infections to begin. The pressure that builds up causes severe pain and damages the kidney tubules. Kidney stones may be dissolved by medicine. Large stones may have to be removed surgically.

CONCLUSION
The homeostatic is the internal environment must be kept fairly constant for the health, growth and efficient functioning of the body cells. These conditions include temperature, PH (hydrogen ion concentration), osmotic pressure and concentrations of dissolved substances in the body fluids such as carbon dioxide, oxygen, urea, food substances (glucose, amino acids, etc).

kidneys regulate the excreted waste from the urine through the osmotic pressure so as to keep the blood constant.
These also filter the body's blood completely every 45 minutes excreting its urea and regulating its water, salt and acid content. Kidney failure occurs at the advanced stage of certain kidney diseases like chronic nephritis when this happens, the patient can only be kept alive by dialysis or kidney transplant.