Structure:
Two kidneys, located in the lower back on either side of the spine
Each kidney contains about 1 million nephrons, the functional units of the kidney
Nephrons consist of a glomerulus (a cluster of blood vessels) and a tubule (a narrow tube)
Functions:
Filter waste and excess fluids from the blood
Regulate salts, sodium, potassium, calcium
Maintain acid-base balance
Produce hormones that help control blood pressure, produce red blood cells, and maintain strong bones
Remove drugs and toxins from the body
Interesting facts:
The kidneys filter about 200 quarts of blood daily!
They regulate blood pressure by controlling fluid levels and blood vessel constriction/dilation
Our kidneys can survive with just 20-30% of their original function, which is why many people can donate a kidney and still lead healthy lives
part of kidny
The kidney is made up of several parts that work together to filter waste and excess fluids from the blood. Here are the main parts of the kidney:
1. Nephrons:
The functional units of the kidney, responsible for filtering waste and excess fluids from the blood. Each kidney contains about 1 million nephrons!
2. Glomerulus:
A cluster of blood vessels in each nephron that filters waste and excess fluids from the blood.
3. Tubule:
A narrow tube in each nephron that collects the filtered fluid and adjusts the levels of water, electrolytes, and other substances.
4. Renal cortex: The outer layer of the kidney, containing the nephrons and other blood vessels.
5.Renal medulla:
The inner layer of the kidney, containing the renal pyramids and the collecting ducts.
6. Renal pyramids: Triangular structures in the renal medulla that collect the filtered fluid from the nephrons.
7. Collecting ducts:
Tubes that collect the fluid from the renal pyramids and transport it to the ureters.
8. Ureters:
Tubes that carry the filtered fluid (now called urine) from the kidneys to the bladder.
9. Renal artery: The blood vessel that supplies oxygenated blood to the kidney.
10. Renal vein: The blood vessel that carries filtered blood away from the kidney.
structure of nephron
Nephrons are the functional units of the kidney, responsible for filtering waste and excess fluids from the blood. Each nephron consists of:
1. Glomerulus:
- A cluster of blood vessels (capillaries) surrounded by the Bowman's capsule.
Filters waste and excess fluids from the blood.
2. Bowman's Capsule:
A double-walled sac that surrounds the glomerulus.
Collects the filtered fluid (filtrate).
3. Proximal Convoluted Tubule (PCT):
The first part of the tubule that receives the filtrate.
- Reabsorbs water, electrolytes, and nutrients back into the blood.
4. Loop of Henle:
A U-shaped structure that continues from the PCT.
Concentrates the filtrate by reabsorbing more water and electrolytes.
5. Distal Convoluted Tubule (DCT):
The final part of the tubule.
Regulates the amount of water and electrolytes in the filtrate.
6. Collecting Duct:
Receives the filtrate from multiple nephrons.
Regulates water reabsorption and electrolyte balance.
7. Macula Densa:
A specialized region in the DCT that senses changes in sodium levels.
Helps regulate blood pressure.
The nephron's structure allows for efficient filtration, reabsorption, and secretion of substances, enabling the kidney to regulate fluid balance, electrolyte levels, and blood pressure.
structure of glomerulus
The glomerulus is a crucial component of the nephron, responsible for filtering waste and excess fluids from the blood. Its structure is designed for efficient filtration:
1. Capillary Tuft:
A cluster of 20-40 capillaries that branch off from the afferent arteriole.
2. Bowman's Capsule:
A double-walled sac that surrounds the capillary tuft.
Inner Layer (Visceral Layer): Forms the inner wall of the capsule, in contact with the capillaries.
Outer Layer (Parietal Layer):
Forms the outer wall of the capsule, in contact with the Bowman's space.
3. Glomerular Basement Membrane (GBM):
A thin, specialized membrane between the capillaries and the Bowman's capsule.
4. Podocytes:
Specialized cells that form the visceral layer of the Bowman's capsule.
Foot Processes: Podocyte extensions that interdigitate with neighboring podo cytes, forming a filtration barrier.
5.Slit Diaphragm:
A thin membrane that bridges the gap between adjacent podocyte foot processes.
6.Mesangium: A region between the capillaries and the Bowman's capsule, containing mesangial cells and matrix.
The glomerulus acts as a filter, allowing water, ions, and small molecules to pass through while retaining larger particles, such as proteins and blood cells. The unique structure of the glomerulus enables this selective filtration.
structure of tubule
The tubule is a long, narrow structure in the nephron that processes the filtrate from the glomerulus. Its structure is designed for reabsorption, secretion, and concentration of substances:
1. Proximal Convoluted Tubule (PCT):
Wide diameter
Simple cuboidal epithelium
Many microvilli (brush border) for increased surface area
- Reabsorbs water, electrolytes, glucose, amino acids, and other nutrients
2. Loop of Henle:
U-shaped structure
Descending limb: water reabsorption
Ascending limb: electrolyte reabsorption
Thin walls, simple squamous epithelium
3. Distal Convoluted Tubule (DCT)_:
Narrower diameter
Simple cuboidal epithelium
Fewer microvilli
Regulates electrolyte balance, water reabsorption, and acid-base balance
4. Collecting Duct:
Wide diameter
Simple columnar epithelium
Regulates water reabsorption, electrolyte balance, and acid-base balance
Receives filtrate from multiple nephrons
The tubule's structure allows for:
Reabsorption of essential substances
Secretion of waste and excess substances
Concentration of the filtrate
Regulation of electrolyte and water balance
structure of cortex
The renal cortex is the outer layer of the kidney, responsible for filtering waste and excess fluids from the blood. Its structure is organized into functional units called nephrons:
1. Nephrons: The functional units of the kidney, consisting of:
- Glomerulus (filtration)
Tubules (reabsorption, secretion, and concentration)
2. Renal Columns:
Groups of nephrons that extend from the cortex into the medulla.
3. Renal Pyramids:
Triangular structures in the renal columns, containing the nephrons.
4. Medullary Rays:
Extensions of the renal pyramids into the medulla, containing collecting ducts.
5.Cortical Nephrons:
Nephrons located in the renal cortex, filtering blood from the renal artery.
6. Juxtaglomerular Apparatus:
Specialized cells near the glomerulus, regulating blood pressure and electrolyte balance.
7. Interstitium:
Connective tissue surrounding the nephrons, containing blood vessels, nerves, and lymphatics.
The renal cortex is responsible for:
Filtering waste and excess fluids from the blood
Reabsorbing water, electrolytes, and nutrients
Secreting waste and excess substances
- Regulating blood pressure and electrolyte balance.
structure of medulla
The renal medulla is the inner layer of the kidney, responsible for concentrating the filtrate from the nephrons. Its structure is organized into:
1. Renal Pyramids:
Triangular structures containing the collecting ducts and nephron loops.
2. Medullary Rays:
Extensions of the renal pyramids, containing collecting ducts and nephron loops.
3. Collecting Ducts:
Tubules that receive filtrate from multiple nephrons and concentrate it.
4. Papillary Ducts:
The final part of the collecting ducts, emptying into the renal pelvis.
5. Interstitium:
Connective tissue surrounding the collecting ducts and nephron loops.
6. Vasa Recta:
Blood vessels that supply the renal medulla.
7. Nephron Loops:
Loops of Henle and distal convoluted tubules that concentrate the filtrate.
The renal medulla is responsible for:
Concentrating the filtrate through countercurrent multiplication
Regulating water and electrolyte balance
Producing a concentrated urine.
The unique structure of the renal medulla allows for efficient concentration of the filtrate, enabling the kidney to regulate fluid balance and blood pressure.
structure of pyramids
The renal pyramids are triangular structures in the renal medulla, responsible for concentrating the filtrate from the nephrons. Each pyramid has:
1. Base:
The widest part, facing the renal cortex.
2. Apex:
The narrowest part, pointing towards the renal pelvis.
3. Medullary Rays:
Extensions of the pyramid, containing collecting ducts and nephron loops.
4. Collecting Ducts
Tubules that receive filtrate from multiple nephrons and concentrate it.
5. Papillary Ducts:
The final part of the collecting ducts, emptying into the renal pelvis.
6. Nephron Loops:
Loops of Henle and distal convoluted tubules that concentrate the filtrate.
7. Interstitium:
Connective tissue surrounding the collecting ducts and nephron loops.
The renal pyramids are organized into:
1. Outer Zone:
The outermost part, containing the base of the pyramid.
2. Inner Zone:
The innermost part, containing the apex of the pyramid.
The renal pyramids are responsible for:
Concentrating the filtrate through countercurrent multiplication
Regulating water and electrolyte balance
Producing a concentrated urine
The unique structure of the renal pyramids allows for efficient concentration of the filtrate, enabling the kidney to regulate fluid balance and blood pressure.
structure of collecting duct
The collecting duct is a tubule that receives the concentrated filtrate from the nephron loops and papillary ducts, and further regulates water and electrolyte balance. Its structure includes:
1. Cortical Collecting Ducts:
Located in the renal cortex, receiving filtrate from cortical nephrons.
2. Medullary Collecting Ducts:
Located in the renal medulla, receiving filtrate from medullary nephrons.
3. Papillary Collecting Ducts:
Located in the renal pyramids, receiving filtrate from papillary ducts.
4. Simple Cuboidal Epithelium:
The lining of the collecting duct, composed of simple cuboidal cells.
5. Tight Junctions:
Connections between cells, forming a impermeable barrier.
6. Aquaporin-2 (AQP2):
Water channels in the cells, regulating water reabsorption.
7. Vasopressin Receptors (V2R):
Receptors that respond to antidiuretic hormone (ADH), regulating water reabsorption.
The collecting duct is responsible for:
Regulating water reabsorption
Regulating electrolyte balance
Producing a concentrated or dilute urine, depending on the body's needs
The unique structure of the collecting duct allows for precise regulation of water and electrolyte balance, enabling the kidney to maintain fluid homeostasis.
structure of urethra
The ureters are muscular tubes that transport urine from the kidneys to the bladder. Their structure includes:
1. Muscular Layer:
A thick layer of smooth muscle cells that contract to propel urine.
2. Inner Layer (Mucosa):
A lining of transitional epithelium, allowing for stretching and compression.
3. Lamina Propria:
A layer of connective tissue beneath the mucosa.
4. Deterior Layer:
A layer of smooth muscle cells that helps to move urine.
5. Adventitia: A layer of connective tissue surrounding the ureter.
6. Ureteric Orifice: The opening of the ureter into the bladder.
The ureters are responsible for:
Transporting urine from the kidneys to the bladder
Preventing backflow of urine through the ureteric orifice
Regulating urine flow through peristalsis (muscular contractions)
The unique structure of the ureters allows for efficient transportation of urine, enabling the urinary system to maintain proper fluid balance and remove waste.
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