Excretory system in Mammals - SS2 Biology Lesson Note

The excretory system in mammals, including humans, consists of several organs that work together to remove waste products and maintain the balance of fluids and ions in the body. The primary organs of the excretory system in mammals are the kidneys, ureters, bladder, and urethra. Here is an overview of the excretory system in mammals:

1. Kidneys:

·         The kidneys are bean-shaped organs located in the abdominal cavity, one on each side of the spine.

·         They serve as the main filtration and excretory organs in mammals.

·         The functional unit of the kidney is called the nephron, which is responsible for filtering waste products and maintaining fluid balance.

·         Each kidney contains millions of nephrons, consisting of a renal corpuscle (glomerulus and Bowman's capsule) and a renal tubule.

·         The nephrons filter blood, reabsorb useful substances (such as water, glucose, and ions), and excrete waste products to form urine.

2. Ureters:

·         The ureters are muscular tubes that connect each kidney to the urinary bladder.

·         They transport urine from the kidneys to the bladder through peristaltic contractions.

3. Urinary Bladder:

·         The urinary bladder is a hollow, muscular organ that stores urine until it is eliminated from the body.

·         The bladder expands as it fills with urine and contracts during urination to expel urine through the urethra.

4. Urethra:

·         The urethra is a tube that carries urine from the bladder to the exterior of the body during the process of urination.

·         In males, the urethra also serves as a passageway for semen during ejaculation.

5. Other Components:

·         The excretory system in mammals also includes accessory structures such as the renal arteries and veins, which supply and drain blood from the kidneys.

·         Hormones, such as antidiuretic hormone (ADH) and aldosterone, play a role in regulating fluid balance and the reabsorption of water and ions in the kidneys.

(geeksforgeeks.com)

The excretory system in mammals helps regulate the concentration of waste products, electrolytes, and water in the body. It is responsible for the production and elimination of urine, which contains metabolic waste products, excess water, and various dissolved substances. This system plays a crucial role in maintaining homeostasis and ensuring the proper functioning of the body.

STRUCTURE OF THE KIDNEY

The kidney is a vital organ of the excretory system in mammals, including humans. It plays a crucial role in filtering waste products from the blood, regulating fluid and electrolyte balance, and producing urine. The structure of the kidney can be divided into several main components:

1. Renal Cortex:

·         The renal cortex is the outermost region of the kidney.

·         It appears granular in texture and contains millions of functional units called nephrons.

2. Renal Medulla:

·         The renal medulla is the inner region of the kidney, located deep within the renal cortex.

·         It consists of triangular structures called renal pyramids.

·         Each pyramid contains tiny tubules called collecting ducts that transport urine towards the renal pelvis.

3. Renal Pelvis:

·         The renal pelvis is a funnel-shaped structure at the innermost part of the kidney.

·         It collects urine from the renal pyramids and transports it to the ureter.

4. Nephrons:

·         Nephrons are the functional units of the kidney responsible for filtering blood and producing urine.

·         Each kidney contains millions of nephrons.

·         Each nephron consists of a renal corpuscle and a renal tubule.

   a. Renal Corpuscle:

·         The renal corpuscle is the initial filtering component of the nephron.

·         It consists of the glomerulus and Bowman's capsule.

·         The glomerulus is a network of tiny blood vessels called capillaries, where filtration occurs.

·         Bowman's capsule surrounds the glomerulus and collects the filtrate.

   b. Renal Tubule:

·         The renal tubule is a long, twisted tube attached to Bowman's capsule.

·         It has several segments, including the proximal convoluted tubule, loop of Henle, and distal convoluted tubule.

·         The renal tubule reabsorbs water, electrolytes, and other essential substances from the filtrate back into the bloodstream.

·         It also secretes additional waste products and substances into the filtrate.

·         The collecting duct receives urine from multiple nephrons and carries it towards the renal pelvis.

5. Renal Arteries and Veins:

·         The renal arteries supply oxygenated blood to the kidneys.

·         Inside the kidney, the arteries branch into smaller arterioles, which eventually form the glomerular capillaries within the renal corpuscles.

·         After filtration, the blood leaves the kidneys through the renal veins, carrying waste products and filtered substances.

The intricate structure of the kidney allows for efficient filtration and regulation of fluid and electrolyte balance. The nephrons within the kidney perform the essential task of filtering blood and producing urine, while the renal cortex, medulla, and pelvis provide structural support and transportation of urine.

(news-medical.net)