The Nephron
9.2.3.2.6 explain how the processes of filtration and reabsorption in the mammalian nephron regulate body fluid composition
Nephrons are the functional unit of the kidney, with 1 000 000 nephron in each kidney.Each nephron consists of a glomerulus (a bundle of tiny capillaries) and a system of tubules.
Nephrons are the functional unit of the kidney, with 1 000 000 nephron in each kidney.Each nephron consists of a glomerulus (a bundle of tiny capillaries) and a system of tubules.
The nephron is a regulatory unit in the body; regulating the body fluid composition through filtering and reabsorbing materials as the waste products move through the system of tubules.
When the waste products are first filtered out in the glomerulus by the glomerular filtration membrane, many essential nutrients and substances also pass through this membrane. For this reason, the blood capillaries exist in a tight network around the tubules so that active reabsorption can take place.
Certain substances and materials like salts, water, potassium and carbonic acid are reabsorbed out of the proximal tube into the capillaries but are absorbed out again in proportions at the distal tubes. The body controls the levels of substances being actively reabsorbed or remaining in the nephron tubules to regulate the body fluid composition.
When the waste products are first filtered out in the glomerulus by the glomerular filtration membrane, many essential nutrients and substances also pass through this membrane. For this reason, the blood capillaries exist in a tight network around the tubules so that active reabsorption can take place.
Certain substances and materials like salts, water, potassium and carbonic acid are reabsorbed out of the proximal tube into the capillaries but are absorbed out again in proportions at the distal tubes. The body controls the levels of substances being actively reabsorbed or remaining in the nephron tubules to regulate the body fluid composition.
Glomerulus
The glomerulus is a collection capillaries, incased in a capsule called Bowman's capsule. The space inside the capsule and surrounding the glomerulus is called Bowman's space.
Plasma-like fluid is filtered by diffusion from the capillary blood into the Bowman’s space.
The glomerulus is a collection capillaries, incased in a capsule called Bowman's capsule. The space inside the capsule and surrounding the glomerulus is called Bowman's space.
Plasma-like fluid is filtered by diffusion from the capillary blood into the Bowman’s space.
The Nephron Tubules
This filtrate enters the tubule system of the nephron. In these tubules, some substances are added to the filtrate as part of the urine formation and some substances are reabsorbed out of the filtrate and back into the blood.
The tubules are divided into 4 segments. The filtrate passes through each of these segments before reaching the ureter.
The video below is a very helpful resource to understand the function and structure of the nephron:
This filtrate enters the tubule system of the nephron. In these tubules, some substances are added to the filtrate as part of the urine formation and some substances are reabsorbed out of the filtrate and back into the blood.
The tubules are divided into 4 segments. The filtrate passes through each of these segments before reaching the ureter.
- Proximal convoluted tubule – highly coiled, drains Bowman’s capsule and where almost complete absorption of nutritionally important substances takes place.
- The loop of Henle – thin loop-like long structure, reabsorbs water and ions from the urine and plays a role in the concentration of urine.
- Distal convoluted tubule – regulates potassium, sodium and pH and where further dilution of the urine takes place.
- Collecting tubule – joins with several tubules to collect the filtrate and where final sodium regulation takes place.
The video below is a very helpful resource to understand the function and structure of the nephron: