NEPHRON Structure & Function Made Easy - Human Excretory System Simple Explanation.

Structure of a nephron

Nephrons are microscopic structures located in the kidney.
The kidney has two regions: the outer cortex and the inner medulla.
The structure of a nephron can be divided into two major portions: the Bowman's capsule and the renal tubule.

"Nephrons are microscopic structures located in the kidney."

Bowman's capsule and glomerulus

The Bowman's capsule is a cup-like structure at one end of the nephron.
The space inside the Bowman's capsule is known as the Bowman's space.
The Bowman's capsule encloses a cluster of blood vessels called the glomerulus.
The glomerulus greatly increases the surface area for filtration.

"The Bowman's capsule is a cup-like structure at one end of the nephron."

Renal tubules

The renal tubules are long and folded tube-like structures that emerge from the Bowman's capsule and end in the duct system of the kidney.
The renal tubules are divided into three main parts: the proximal convoluted tubule, the loop of Henle, and the distal convoluted tubule.
The distal convoluted tubule drains into the collecting duct, which ultimately leads to the renal pelvis and the ureter.

"The renal tubules are long and folded tube-like structures that emerge from the Bowman's capsule and end in the duct system of the kidney."

Function of a nephron

The nephron uses four main mechanisms to convert blood into urine: filtration, reabsorption, secretion, and excretion.
Filtration occurs at the level of the renal corpuscle, where the glomerulus filters impure blood.
Reabsorption and secretion occur in different parts of the renal tubules.

"The nephron uses four main mechanisms to convert blood into urine: filtration, reabsorption, secretion, and excretion."

Structure of the Bowman's Capsule

The wall of the Bowman's capsule contains a special type of cells called podocytes.
Between the podocytes, there are small gaps known as filtration slits.
These three layers (endothelial cells, basement membrane, and podocytes) form the glomerular filtration barrier.

"The wall of the Bowman's capsule contains a special type of cells called podocytes and between these podocytes we have small gaps known as the filtration slits."

Glomerular Filtration Barrier

The glomerular filtration barrier acts as a filter paper, filtering out impure plasma from the blood.
The glomerular filtration barrier allows water and solutes to be filtered out of the blood plasma and into the Bowman's space.
Only about 1/5 of the plasma is filtered in the glomerulus, while the rest passes into the efferent arteriole.
Red blood cells and larger molecules like proteins do not get filtered.

"The glomerular filtration barrier acts like a filter paper, filtering out impure plasma from the blood, and allows water and solutes to be filtered out into the Bowman's space."

Blood Pressure and Filtration

Glomerular blood pressure provides the driving force for water and solutes to be filtered out of the blood plasma and into the Bowman's capsule.
The diameter of the afferent and efferent blood vessels is different, resulting in increased pressure inside the glomerulus.
The kidneys can adjust the rate of glomerular filtration by adjusting the pressure inside the glomerulus.

"The glomerular blood pressure provides the driving force for filtration by pushing water and solutes out of the blood plasma into the Bowman's capsule."

Formation of Glomerular Filtrate

The plasma that gets filtered into the Bowman's space is known as the glomerular filtrate.
The glomerular filtrate moves into the renal tubules for further processing to form urine.
The proximal convoluted tubule reabsorbs approximately two-thirds of the filtered salts and water, as well as all glucose and amino acids.

"The plasma that gets filtered into the Bowman's space is known as the glomerular filtrate, which moves into the renal tubules for further processing to form urine."

Reabsorption in Renal Tubules

The whole length of the renal tubule is surrounded by peritubular capillaries.
Reabsorption occurs in the renal tubules, where important substances are passed back into the blood circulation.
About 70% of sodium chloride, 70% of water, and more than 95% of glucose and amino acids get reabsorbed in the proximal convoluted tubule.
The loop of Henle has a major role in the concentration of urine.

"Reabsorption occurs in the renal tubules, where important substances are passed back into the blood circulation."

Secretion and Urine Formation

Secretion is the opposite of reabsorption, where waste ions and hydrogen ions pass from the capillaries into the renal tubules.
Secretion is the final step in the formation of urine, where waste substances harmful to the body are actively removed from the blood.
The major substances secreted into the distal convoluted tubules include hydrogen ions, potassium ions, and ammonium ions.
The urine in each collecting duct is drained into the renal pelvis, connected to the ureters, and eventually to the urinary bladder.

"Secretion is the final step in the formation of urine, where waste substances harmful to the body are actively removed from the blood."

Concentration of Urine

The collecting duct plays a crucial role in determining whether urine should be concentrated or diluted.
The collecting duct extends back into the medulla, which contains a higher concentration of salts compared to the cortex.
Antidiuretic hormone acts on the collecting ducts to regulate the concentration of urine.

"The collecting duct plays a crucial role in determining whether urine should be concentrated or diluted."

##rethra and Other Organs of Human Excretion

The video mentioned that there is more to learn about the urethra and other organs involved in the process of human excretion.
This suggests that the video will provide further information and details about these topics.

"Now to learn more about the urethra and all the other organs of human excretion."