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Anatomy of the Renal and Urinary System

Updated: Jul 18, 2021

This post will cover the Renal System: Basic Anatomy. Let's start with the Function of the Renal System.

The purpose of the renal system is to remove waste from the body, regulate acid base balance and regulate fluid and electrolyte balance. Renin is an important hormone that regulates blood pressure and erythropoietin to stimulate the bone marrow to produce red blood cells.

Renal System Structures

The renal system consists of two kidneys, two urethras, one bladder and one urethra. The kidneys excrete waste products that the nephron removes from the blood, along with other fluids that produce formed urine. Urine passes through the ureters to the urinary bladder. As the bladder fills, nerves in the bladder relax further down. A voluntary stimulus then occurs in the urine that passes into the urethra and is expelled from the body.


What's very important to know is that inside the kidneys are nephrons. Nephrons filter out wastes, fluids, electrolytes, acids and bases. Without this, our bodies would accumulate toxins and fluids which makes us sick. On the top of the kidneys are the Adrenal glands which influence blood pressure, sodium and water retention.


Without balance in our bodies, we would not be able to live. Our bodies are very smart and know when something is out of balance. One of the most important concepts to understand is that the renal system has many functions when it comes to homeostasis because it is a selective filtering system. With the renal system there is a homeostasis of sodium, potassium and water.

Homeostasis of Water

Anti diuretic hormone is responsible for the re absorption of water by the kidneys. The secretion of ADH is stimulated by dehydration or high sodium intake and by a decrease in blood volume.

Homeostasis of Sodium

When the amount of sodium increases, extra water is retained to preserve osmotic pressure. An increase in sodium and water produces an increase in blood volume and blood pressure. When this happens, normally the glomerular filtration increases, returning the blood pressure to normal. Renin also responds when there is a decline in extracellular fluid volume.

Homeostasis of Potassium

Aldosterone is stimulated to reabsorb sodium and secrete potassium. Potassium regulates the muscles for important organs such as the heart.


We mentioned the two hormones Renin and Antidiuretic hormones. Another hormonal function includes secretion of Erythropoietin. Erythropoietin increases the RBC in the bone marrow in response to low arterial blood gas.

When our bodies aren’t having enough oxygen in the body, there is a threat of cell and tissue death. So once our bodies detect this, erythropoietin activates to give our cells more oxygen.

Risk Factors

Now that we know the most important topics on anatomy and physiology, let's talk about risk factors that are always very important to know for exams.

Risk factors are important because our goal is to help educate patients on prevention as they are more prone to having a renal disease. Risk factors also help determine the possible treatments.

Risk Factors Associated with Renal Disorders are chemical or environmental toxin exposure, contact sports, diabetes mellitus, family history of renal disease, urinary tract infections and hypertension. The two most common risk factors of renal disease are hypertension and type two diabetes also known as diabetes mellitus.

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