Name: how kidneys keep gfr stable
Uploaded: 2024-12-20T14:49:30.000Z
Duration: 1 min 28 s
Channel: JoVE

K12 Standards

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Ohio’s Learning Standards and Model Curriculum

9-12

Human Anatomy and Physiology

Absorption And Excretion

Urinary System

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Glomerular Filtration Rate and its Regulation

The glomerular filtration rate or GFR is the volume of filtrate formed per minute by the glomeruli.
Any changes in the local blood pressure and flow can affect the GFR; the kidneys adapt to maintain a constant GFR.&#160;&#160;
This autoregulation involves two intrinsic mechanisms.
In the myogenic mechanism, smooth muscle in afferent arterioles contracts when blood pressure rises, reducing the glomerular blood flow and GFR.
Increased sodium levels in the filtrate detected by the macula densa cells initiate the tubuloglomerular feedback mechanism.
It triggers a signaling mechanism for vasoconstriction in afferent arterioles, reducing glomerular blood flow and GFR to maintain homeostasis.
However, under very low systemic blood pressure, extrinsic controls take over, including hormonal and neuronal mechanisms.
The sympathetic nervous system releases norepinephrine, which constricts the efferent and afferent arterioles, decreasing GFR.
The hormone angiotensin-II balances vasoconstriction in the afferent and efferent arterioles to maintain GFR.
In contrast, atrial natriuretic peptide triggers the dilation of afferent arterioles and the constriction of efferent arterioles, raising GFR.

glomerular filtration rate and its regulation

The Glomerular Filtration Rate (GFR) is a measure of kidney function, reflecting the volume of filtrate formed per minute in the kidneys. On average, GFR is approximately 125 mL/min in males and 105 mL/min in females. Maintaining a relatively constant GFR is essential for the kidneys to effectively regulate body fluid homeostasis and maintain extracellular stability.
GFR regulation involves two primary intrinsic controls: the myogenic and tubuloglomerular feedback mechanisms.
The myogenic mechanism responds to fluctuations in systemic blood pressure. When this pressure increases, the afferent arterioles constrict, restricting blood flow into the glomerulus and maintaining an optimal GFR. Decreased systemic blood pressure leads to arteriole dilation and increased glomerular hydrostatic pressure.
The macula densa cells of the juxtaglomerular complex control the tubuloglomerular feedback mechanism. These cells respond to high sodium chloride (NaCl) levels in the filtrate due to increased GFR. The macula densa cells release vasoconstrictor chemicals that constrict the afferent arteriole, reducing blood flow into the glomerulus and decreasing the net filtration pressure (NFP) and GFR.
However, these intrinsic controls cannot manage extremely low systemic blood pressure. Under such circumstances, extrinsic controls like neural and hormonal mechanisms take over. The sympathetic nervous system controls constricting the afferent arterioles when blood pressure falls, thereby decreasing GFR and restoring normal blood volume and blood pressure. Two key hormones, Angiotensin II and Atrial Natriuretic Peptide (ANP), also regulate GFR. Angiotensin II reduces GFR by narrowing arterioles and reducing renal blood flow. Angiotensin II also stimulates aldosterone release, promoting sodium and water retention to restore blood volume. In contrast, ANP enhances sodium excretion (natriuresis) and water loss, reducing systemic blood pressure and volume. while ANP increases GFR by relaxing glomerular mesangial cells and increasing the capillary surface area available for filtration.

The glomerular filtration rate or GFR is the volume of filtrate formed per minute by the glomeruli.
Any changes in the local blood pressure and flow can ...

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Anatomy and Physiology

Unit 1

The Urinary System

KEY TERMS AND CONCEPTS

how kidneys keep gfr stable

Glomerular filtration rate, or GFR, is a key measure of kidney function. It shows how much filtrate the kidneys form each minute. Average GFR is about 125 mL/min in males and 105 mL/min in females.

Keeping GFR steady helps the kidneys control body fluid balance and maintain extracellular stability. The body uses intrinsic controls first. These include the myogenic mechanism and tubuloglomerular feedback.

The myogenic mechanism responds to changes in systemic blood pressure. When blood pressure rises, the afferent arterioles constrict. This limits blood flow into the glomerulus and helps keep GFR near normal. When blood pressure falls, the arterioles dilate and glomerular hydrostatic pressure increases.

Tubuloglomerular feedback depends on the macula densa cells in the juxtaglomerular complex. These cells detect high sodium chloride, or NaCl, in the filtrate when GFR is too high. They release vasoconstrictor chemicals that narrow the afferent arteriole. This lowers blood flow into the glomerulus and decreases net filtration pressure, or NFP, and GFR.

Intrinsic control cannot handle extremely low systemic blood pressure. In that case, extrinsic controls take over. The sympathetic nervous system constricts the afferent arterioles when blood pressure drops, which lowers GFR and helps restore blood volume and blood pressure.

Hormones also regulate GFR. Angiotensin II lowers GFR by narrowing arterioles and reducing renal blood flow. It also stimulates aldosterone release, which promotes sodium and water retention to help restore blood volume. Atrial Natriuretic Peptide, or ANP, has the opposite effect. It increases sodium excretion, called natriuresis, and water loss, which lowers blood pressure and volume. ANP also raises GFR by relaxing glomerular mesangial cells and increasing the capillary surface area available for filtration.

How Kidneys Keep GFR Stable

introduction to urinary system

Urinary System: Organs and Key Functions

The urinary system includes two kidneys, two ureters, the urinary bladder, and the urethra. Together, these organs remove wastes from the blood and help keep body conditions stable. The kidneys are bean-shaped and sit in the retroperitoneal space on either side of the vertebral column, between T12 and L3. They are partly protected by the rib cage and cushioned by perirenal fat. The kidneys make urine and also help control blood pressure, electrolyte levels, and hormone production. Each ureter...

external anatomy of the kidney

Kidney Structure, Position, and Coverings

The kidneys are a pair of bean-shaped organs that help keep the body healthy. They filter waste from the blood, help regulate blood pressure, maintain electrolyte balance, and support red blood cell production. The kidneys sit in the retroperitoneal space, which means behind the abdominal lining, on either side of the vertebral column. The 11th and 12th ribs protect them from behind. The right kidney lies slightly lower than the left because the liver is above it. In adults, the kidneys are...

internal anatomy of the kidney

Kidney Cortex, Medulla, and Pelvis

The kidney is a vital organ that helps maintain homeostasis and overall health. It sits against the posterior abdominal wall, behind the abdominal cavity on either side of the spine. The kidneys are retroperitoneal organs. They are found roughly between the twelfth thoracic vertebra and the third lumbar vertebra, and each one is usually 10-12 cm long, 5-6 cm wide, 3-4 cm thick, and about 150 grams. The outer region of the kidney is the renal cortex. It is a light-colored layer that surrounds...

blood and nerve supply to the kidney

Kidney Blood Vessels and Nerve Control

The kidneys rely on a strong network of blood vessels and nerves to filter blood and keep body fluids balanced. They remove waste, regulate electrolytes, and depend on steady circulation to do this work. Their nerve supply also helps control filtration, urine flow, and blood pressure. Blood reaches each kidney through the renal arteries, which branch off the abdominal aorta. These arteries enter the kidney at the hilum, the notch on the medial side of each kidney. Inside the kidney, each renal...

nephrons

Kidney Nephron Structure and Function

Kidneys contain millions of nephrons, the working units that filter blood and form urine. Each nephron has two main parts. The renal corpuscle filters blood plasma, and the renal tubule processes the glomerular filtrate. The renal corpuscle is made of the glomerulus and Bowman&amp;#39;s capsule. The glomerulus is a capillary network, and Bowman&amp;#39;s capsule is a double-walled epithelial structure around it. Blood plasma is filtered in Bowman&amp;#39;s capsule, and the filtered fluid then...

renal corpuscle

Kidney Filtration in the Renal Corpuscle

The renal corpuscle begins kidney filtration in the nephron. It includes the glomerulus and Bowman’s capsule, two microscopic structures that work together to help make urine. The glomerulus filters blood, and Bowman’s capsule collects the fluid that passes through. The glomerulus is a tiny tuft of capillaries at the start of the nephron. It sits inside Bowman’s capsule and gets blood from an afferent arteriole. Blood leaves through an efferent arteriole. This setup is unusual because the...

renal tubule and collecting duct

How Nephrons Reclaim Water and Salts

The renal tubule reclaims useful substances and helps the body manage water, salts, and pH. It has three main parts: the proximal convoluted tubule, the Loop of Henle, and the distal convoluted tubule. These segments work with the collecting duct to form urine and keep internal conditions stable. The proximal convoluted tubule, or PCT, is the first segment and extends from Bowman’s capsule around the glomerulus. Its coiled shape and microvilli, which are tiny membrane folds, increase surface...

physiology of urine formation

How the Kidneys Make Urine

The kidneys make urine through a careful process that helps keep body fluids stable. This process supports homeostasis, which means the body keeps its internal conditions balanced. The kidneys remove wastes and extra substances from the blood and turn them into urine. The first stage is glomerular filtration. Each kidney has about 1 million nephrons, which are the functional units that filter blood. At the center of each nephron is the glomerulus, a network of tiny capillaries where filtration...

glomerular filtration

Selective Kidney Filtration Membrane

The selective kidney filtration membrane filters blood in the renal system. It is made of glomerular capillaries and podocytes. Together, these structures form a barrier that lets water and small solutes pass while keeping most plasma proteins and blood cells in the bloodstream. The filtration process depends on three layers. The first is the glomerular endothelial cells, which line the capillaries. These cells have large pores called fenestrations. The fenestrations let blood plasma solutes...

glomerular filtration: net filtration pressure

glomerular-filtration-net-filtration-pressure

Kidney Filtration Forces in the Glomerulus

Kidney filtration in the glomerulus depends on the balance of three pressures. These forces control how much blood plasma moves from the glomerulus into the capsular space. The process is driven by glomerular blood hydrostatic pressure, or GBHP, and opposed by capsular hydrostatic pressure, or CHP, and blood colloid osmotic pressure, or BCOP. GBHP is the pressure of blood inside the glomerular capillaries. It averages about 55 mmHg and pushes water and dissolved solutes through the filtration...

Glomerular filtration rate, or GFR, is a key measure of kidney function. It shows how much filtrate the kidneys form each minute. Average GFR is about 125 mL/min in males and 105 mL/min in females. Keeping GFR steady helps the kidneys control body fluid balance and maintain extracellular stability. The body uses intrinsic controls first. These include the myogenic mechanism and tubuloglomerular feedback. The myogenic mechanism responds to changes in systemic blood pressure. When blood...

tubular reabsorption and secretion

Kidney Tubule Transport in the Nephron

Kidney tubule transport in the nephron changes the fluid that leaves the glomerulus. Once this fluid enters the proximal convoluted tubule, it is called filtrate. Its composition shifts as the tubule reabsorbs useful substances and secretes unwanted ones. Tubular reabsorption is a selective process that begins in the proximal tubules. Substances can move by the transcellular route, which passes through the tubule cell and into the peritubular capillaries, or by the paracellular route, which...

reabsorption and secretion in the pct

PCT Transport of Glucose, Water, and Ions

The proximal convoluted tubule, or PCT, is a major site where filtered water, ions, glucose, and amino acids are moved back into the body. It works in the kidney’s filtration system after the glomeruli produce the filtered fluid. Most of the filtered water and many solutes are reabsorbed here. Sodium ion transport drives much of this reabsorption. The PCT uses symport, which moves substances in the same direction, and antiport, which moves substances in opposite directions. One key example is...

reabsorption and secretion in the loop of henle

reabsorption-and-secretion-in-the-loop-of-henle

Ion Movement in the Loop of Henle

The loop of Henle controls ion movement in the nephron. In the thick ascending limb, cells use Na+–K+–2Cl− symporters on the apical membrane to take up one sodium ion, one potassium ion, and two chloride ions from the tubular fluid. After entry into the cell, sodium ions are pumped into the interstitial fluid at the base and sides of the cell. They then diffuse into the vasa recta, the tiny blood vessels that help carry substances away. Chloride ions leave through leakage channels in the...

reabsorption and secretion in the dct and collecting duct

reabsorption-and-secretion-in-the-dct-and-collecting-duct

How ADH Changes Kidney Water Reabsorption

The early distal convoluted tubule, or DCT, reabsorbs water and salts as filtrate moves through the kidney. It handles about 10 to 15% of filtered water and about 5 to 10% of filtered sodium and chloride. This part of the tubule uses Na+-Cl- symporters on the apical membrane, sodium-potassium pumps, and chloride leakage channels on the basolateral membrane. The early DCT is also a place where parathyroid hormone, or PTH, can increase calcium reabsorption when the body needs it. Farther along,...

urine: physical and chemical properties

Urine Color, Smell, and pH

Urine is mostly water, but its color, smell, pH, and specific gravity can reveal useful health clues. It is about 95% water and 5% solutes. The main solute is urea, which forms when amino acids are broken down. Other important waste products include uric acid, from nucleic acid metabolism, and creatinine, from creatine phosphate breakdown in skeletal muscle tissue. Urine also contains many dissolved ions and small molecules. These include sodium, chloride, potassium, phosphate, sulfate,...

formation of dilute urine

How Kidneys Excrete Excess Water

The kidneys excrete excess water by making dilute urine, especially during high fluid intake. This process depends mainly on juxtamedullary nephrons, which help the body keep fluid balance by adjusting how much water and ions stay in the filtrate. As filtrate moves through the proximal convoluted tubule (PCT), its osmolarity stays isosmotic with the renal cortex. Osmolarity means the concentration of dissolved particles in a fluid. In the PCT, water and solutes are reabsorbed together, so the...

formation of concentrated urine

Kidney Loop Mechanisms for Urine Concentration

Kidney loop mechanisms help the body conserve water by making urine more concentrated. A steep solute gradient forms in the kidney medulla, the inner region of the kidney. This medullary osmotic gradient runs from the renal cortex down through the medulla. Juxtamedullary nephrons build and maintain this gradient. Their loops extend deep into the medulla, where countercurrent mechanisms work. Countercurrent multiplication happens when the descending and ascending limbs of the nephron loop...

renal clearance

Measuring Kidney Function with Clearance

Kidney function can be measured by looking at glomerular filtration rate, or GFR. GFR shows how efficiently the glomeruli filter blood. Renal clearance is one common way to estimate this rate using substances such as inulin or creatinine. Renal clearance means the volume of plasma that is cleared of a specific substance in a set time. To measure it, urine is collected during each bladder voiding over a 24-hour period. A single blood sample is taken at the end of that interval. The clearance...

ureters

Urine Flow Through the Ureters

The ureters are retroperitoneal tubes that carry urine from each kidney to the urinary bladder. They lie on either side of the vertebral column. These tubes have thick walls and are about 25 to 30 cm long. At the renal pelvis, the ureter is about 10 mm wide. It then narrows to about 1 mm as it enters the back wall of the bladder at an angle. The ureteric orifices are slit-like, and this shape helps prevent urine from flowing backward toward the kidneys when the bladder contracts. Each ureter...

urinary bladder

Bladder Structure and Urine Storage

The urinary bladder is a hollow, muscular sac that stores urine before it leaves the body. It can hold about 600 mL of urine before micturition, or urination. The bladder sits behind the pubic symphysis in the pelvic floor and is retroperitoneal, meaning it lies behind the lining of the abdominal cavity. Its position changes slightly by sex. In males, the bladder lies in front of the rectum. In females, it is located anterior to the vagina and uterus. The bottom of the bladder has a...

the micturition reflex

Bladder Filling and Urine Release

Urination depends on the bladder, its detrusor muscle, and two sphincters working together. The detrusor muscle is the smooth muscle in the bladder wall. The two sphincters help keep urine in the bladder until it is time to empty it. As urine builds up, the bladder wall stretches. That stretch activates the urine storage reflex. This reflex is controlled by the sacral spinal segments and the pontine storage center. During storage, sympathetic signals make the detrusor muscle relax and the...

urethra

Urine Flow Through the Urethra

The urethra is the tube that carries urine out of the body. It runs from the bladder to the external opening, where urine leaves the urinary system. Its main job is to release urine, but its structure and role are not the same in males and females. In females, the urethra is short. It measures about 3–4 cm and opens in front of the vaginal opening. In males, the urethra is longer and passes through the penis. It has two jobs in males. It carries urine and also helps eject semen. The male...

dialysis

Dialysis for Kidney Failure Support

Dialysis helps support people with renal failure when the kidneys can no longer filter waste from the blood well. Renal failure can be acute renal failure (ARF), which begins suddenly, or chronic renal failure (CRF), which develops slowly over time. Acute kidney injury may come from pre-renal causes such as hypovolemia or shock, intrinsic renal causes such as acute tubular necrosis, or post-renal causes such as urinary obstruction. Chronic renal failure is often linked to diabetes mellitus and...

disorders of the urinary system

Common Urinary Tract Problems and Their Effects

The urinary system removes waste and extra fluid from the body. Several urinary tract problems can disrupt this process. These problems may result from infections, stress, age, congenital abnormalities, or lifestyle factors. Urinary tract infections, or UTIs, are among the most common disorders. Bacteria enter the urethra and may spread to the bladder, causing cystitis. If the infection moves up to the renal pelvis, it becomes pyelonephritis. UTIs are usually treated with antibiotics, but...

key terms and concepts

Learn how the kidneys keep glomerular filtration rate stable with myogenic control, tubuloglomerular feedback, sympathetic nerves, Angiotensin II, and ANP.

How Kidneys Keep GFR Stable | JoVE K12

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Digestive System

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Respiratory System

How Kidneys Keep GFR Stable

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