Open In App

Human Excretory System

Improve
Improve
Like Article
Like
Save
Share
Report

The human excretory system, also known as the urinary system, comprises kidneys, ureters, bladder, and urethra. The human excretory system filters waste products and excess substances from the bloodstream, resulting in the formation of urine, which is held temporarily within the bladder until it is eliminated. In addition to waste elimination, the excretory system plays a vital role in regulating electrolyte levels, blood pressure, and the body’s acid-base balance. It also carries out the production of hormones like erythropoietin, which stimulates the production of red blood cells.

Human Excretory System

The excretion process in humans is a physiological process essential for maintaining internal equilibrium and eliminating body waste products. The primary organs responsible for excretion are the kidneys. It perform blood filtration through numerous microscopic units known as nephrons, facilitating the removal of waste substances such as creatinine and urea while reabsorbing essential elements like glucose and electrolytes. The resulting waste fluid is transformed into urine, which is subsequently transfered through the ureters to the bladder, where it is temporarily stored. As the bladder reaches its capacity, urination occurs, expelling urine through the urethra out of the body.

Excretory System Organs

The human excretory system, is responsible for eliminating waste products and maintains the body’s electrolyte and fluid balance. The excretory organs responsible for carrying out excretion of the waste products are as follows:

  • Pair of Kidneys
  • Pair of Ureters
  • Urinary Bladder
  • Urethra

Kidneys

Kidneys are bean shaped organs which filter blood to remove waste products and excess substances, such as urea, creatinine, and excess salts. They also regulate blood pressure and the concentration of ions in the blood. The normal size of a kidney is 10-12 cm, the width of 5-7 cm, and the weight is approx. 120-170g. Kidneys have a hard outer layer. This is known as the Capsule. The Capsule can further be divided into two major parts:

Anatomy of Kidney

  • Cortex: The renal cortex is the outermost layer of the kidney. It contains the glomeruli, which are clusters of tiny blood vessels responsible for initial blood filtration. Blood is filtered here to remove waste products, electrolytes, and excess water, forming an ultra filtrate that enters the nephrons. The renal cortex contains the proximal and distal convoluted tubules, which are parts of the nephrons involved in reabsorption and secretion of substances.
  • Medulla: The renal medulla is the inner part of the kidney. It contains renal pyramids, which are cone-shaped and have tubules that carry urine from the cortex to the renal pelvis. Each pyramid has a papilla at its tip, where urine is collected and delivered to the minor calyces. The medulla plays a vital role in concentrating urine.

Structure of Kidney

The overview of the basic structure of the kidney explained below:

Capsule

The outermost layer of the kidney is known as the capsule. It is hard in nature made up of stromal cells surrounded by connective tissue. It plays an important role in the development of kidneys.

Nephron

The nephron is the functional unit of the Kidney. The Nephron is the small functional structure that produces Urine in humans. The Urines which are being produced by the Nephrons are being excreted outside of the body. The structure of the Nephrons can be divided into two parts as follows:

Renal Corpuscles

It consists of blood vessels & different layers. It forms the part of cortex region of the kidney, where urine formation takes place. It consists of:

  1. Glomerulus: The glomerulus is a tuft of capillaries surrounded by the Bowman’s capsule. The blood pressure forces water, ions, and small solutes out of the blood and into the Bowman’s capsule to form the filtrate.
  2. Bowman’s Capsule: The Bowman’s capsule is a cup-shaped structure that surrounds the glomerulus. It collects the filtrate formed during blood filtration and transfers it to the renal tubules.

Structure of Nephron

Renal Tubules

The renal tubule is a long, convoluted tube connected to the Bowman’s capsule, where resorption and secretion of filtrate take place. The renal tubule is divided into several parts:

  1. Proximal Convoluted Tubule (PCT): The PCT forms the first part of the nephron and is located near the Bowman’s capsule. It carries out the reabsorption of essential substances such as water, glucose, amino acids, and ions into the bloodstream from the filtrate.
  2. The Henle’s Loop: It is the middle part of the Nephrons and is U shaped. It is divided into a descending limb and an ascending limb. It maintains the concentration gradient.
  3. Distal Convoluted Tubule (DCT): This is the last part of the Nephron. After Henle’s Loop, this structure is present. It regulates the body’s acid-base balance and electrolyte levels.
  4. Collecting Duct: After passing through the DCT, the filtrate becomes urine and enters the collecting duct.

Types of Nephron

Depending upon the size, location & availability, the Nephrons are divided into two groups. They are:

  • Cortical Nephrons: This is the most common type of nephron. This type has very small Nephrons. It is located primarily in the outer region of the renal cortex. Cortical nephrons play an important role in the reabsorption of water, ions, and essential substances from the filtrate, regulate blood pressure, and maintain body’s internal environment.
  • Juxtamedullary Nephrons: It consists of long loops of Henle that extend deep into the medulla. The long loops of Henle in juxtamedullary nephrons create and maintain the concentration gradient in the medulla. This concentration gradient enables the kidneys to produce concentrated urine, helping conserve water and maintain proper hydration. I

Ureters

Ureters connect the kidneys to the bladder, allowing the flow of urine from the kidneys to be stored in the bladder. They play a vital role in urinary excretion by transporting urine, which contains waste products and excess substances, away from the kidneys. Each human has two ureters, one for each kidney, and they vary in length but are typically about 25-30 cm long.

Urinary Bladder

This is the sac-like organ present in the human body. This helps to store the urine inside of it for a while. The capacity of the bladder is 500ml of urine. The bladder can be divided into two parts, they are the upper part & lower part. In the lower part, there is the neck. From the neck, the Urethra is attached to this area. The bladder is situated in the pelvic cavity of the human body.

Urethra

The primary function of the urethra is to carry urine from the bladder to the outside of the body during urination. In males, the urethra also serves as the passageway for semen during ejaculation, as it extends through the penis. In females, its sole function is urine elimination. The urethra is equipped with muscular sphincters that allow voluntary control over the release of urine, facilitating the regulation of bladder emptying.

Diagram of Human Excretory System

The diagram of human excretory system is as follows:

Diagram of Human Excretory System

Mechanism of the Excretion in Humans

Excretion is a multistage process. Every part of the Nephrons contributes to the mechanism. The Excretion process is a combination of three sub-processes. These subprocesses are Filtration, Re-Absorption & Secretion. These sub-processes are performed by the different parts of the Nephrons.

Urine Formation

Urine formation is a complex physiological process in the kidneys. The process takes place as follows:

  • Blood is filtered in nephrons, removing small molecules like water, ions, glucose, urea, and creatinine.
  • Reabsorption of essential substances (e.g., glucose, ions) back into the bloodstream occurs.
  • Active secretion of substances (e.g., hydrogen ions) into renal tubules aids waste removal.
  • Filtrate undergoes further modification, transforming into urine.
  • Urine comprises water, urea, creatinine, excess ions, and waste products.
  • Concentration of urine adjusts based on body hydration needs.
  • Formed urine travels from kidneys to the bladder via ureters.
  • Bladder stores urine until the micturition reflex signals elimination.
  • Bladder contracts, urinary sphincters relax, allowing urine to exit through the urethra.
  • Urine formation regulates waste removal, water balance, and internal homeostasis.

Functions of Human Excretory System

The main function of the excretory system is to produce urine or waste material. The process of the production of the water material is mainly inside the kidney. The functions of Human Excretory System is as follows:

  • Removes metabolic waste products like urea and creatinine from the body.
  • Regulates water levels by adjusting urine concentration.
  • Maintains proper levels of ions like sodium, potassium, and calcium.
  • Controls blood pressure through the renin-angiotensin-aldosterone system.
  • Helps maintain the body’s pH levels within a narrow range.
  • Produces erythropoietin to stimulate red blood cell production.
  • Clears drugs and toxins from the bloodstream.
  • Adjusts urine concentration to match hydration levels.
  • Filters the blood to remove waste products and excess substances.
  • Temporarily stores urine in the bladder and expels it through the urethra during urination.

Disorder of Human Excretory System

Following are the disorders which are related to the human excretory system are:

  • Kidney Stones: Hard deposits of minerals that can block the urinary tract, causing intense pain.
  • Urinary Tract Infections (UTIs): Bacterial infections affecting the bladder (cystitis) or kidneys (pyelonephritis).
  • Chronic Kidney Disease (CKD): Gradual loss of kidney function, often linked to conditions like diabetes and hypertension.
  • Renal Failure: Complete loss of kidney function, requiring dialysis or transplantation for survival.
  • Glomerulonephritis: Inflammation of the kidney’s filtration units, leading to protein and blood in the urine.

Disorder of Human Excretory System

Dialysis Process

The dialysis process is explained as follows:

Process of Dialysis

Dialysis is a medical treatment for individuals with kidney failure. Two primary types of dialysis are: hemodialysis and peritoneal dialysis. Hemodialysis uses a machine to filter blood outside the body. Blood is drawn from a vascular access and returned cleansed. Peritoneal dialysis uses the abdomen’s lining as a natural filter. A sterile solution is introduced into the abdominal cavity. Waste and excess fluids diffuse into the solution. The used solution is drained and replaced regularly. Dialysis is done multiple times weekly (hemodialysis) or daily (peritoneal). It helps manage kidney failure but is not a cure, often necessitating a lifelong commitment.

Importance of Human Excretory System

  • It eliminates metabolic waste products, such as urea and creatinine, from the body, preventing their harmful buildup.
  • The excretory system helps control blood pressure by regulating the volume of blood and sodium levels through the release of renin and aldosterone.
  • It maintains the balance of electrolytes like sodium, potassium, and calcium, which is essential for nerve and muscle function.
  • The system regulates the body’s pH levels by excreting excess hydrogen ions and reabsorbing bicarbonate ions.
  • The kidneys filter and purify around 180 liters of blood daily, removing toxins and excess substances.
  • It controls the amount of water in the body by adjusting urine concentration, preventing dehydration or overhydration.
  • The kidneys release erythropoietin, a hormone that stimulates red blood cell production in response to low oxygen levels.
  • It aids in detoxifying the body by filtering out drugs, chemicals, and toxins.
  • The kidneys convert vitamin D into its active form, necessary for calcium absorption and bone health.

FAQs on Human Excretion System

1. How does urine formation occur in the kidneys?

Answer:

Urine formation involves filtration, reabsorption, and secretion processes in the nephrons of the kidneys. Filtration separates waste from the blood, reabsorption reclaims essential substances, and secretion adds additional waste products to the urine.

2. What are the 4 excretory systems of the body?

Answer:

The excretory system consist of these four main parts: A pair of kidneys, a pair of ureters, a urinary bladder, a urethra.

3. What are the organs present in the excretory system?

Answer:

The organs are the kidneys, ureters, bladder, and urethra. The kidneys filter waste from the blood, and the ureters transport urine to the bladder, where it’s stored until elimination through the urethra.

4. What is the function of the kidneys?

Answer:

Kidneys filter the blood, removing waste products, excess ions, and excess water to form urine. They also play a role in regulating blood pressure and producing hormones like erythropoietin.

5. How much urine does the average person produce in a day?

Answer:

On average, a person produces about 1 to 2 liters of urine per day, but this can vary depending on fluid intake, diet, and individual factors.



Last Updated : 12 Jan, 2024
Like Article
Save Article
Previous
Next
Share your thoughts in the comments
Similar Reads