The document discusses renal physiology and the functions of the kidney. It covers the major topics of:
1. The functions of the kidney including regulating fluid balance, electrolyte balance, and excreting wastes.
2. The anatomy of the nephron and kidney including glomerular filtration, tubular reabsorption and secretion.
3. The processes involved in forming urine including filtration, reabsorption of water and electrolytes, and secretion of wastes - with most of the filtered materials being reabsorbed.
I am a medical student. I have one friend who is persuing his MBBS degree in Taishan Medical UNiversity. I got these notes from him.
These notes are by Dr. Bikesh, He is a famous lecturer of TMU.
These notes have helped me a lot and i also watch his lecture videos , which are great; highly simple and huge content.
I am uploading with Renal physiology. If you want some other topics i would upload for you.
"Let the Knowledge be spread" Dr. Bikesh
Tubular reabsorption (The Guyton and Hall physiology)Maryam Fida
It is the second step of urine formation.
It is defined as;
“ The process by which water and other substances are transported by renal tubules back to blood is called Tubular Reabsorption”.
Tubular reabsorption is highly selective.
Some substances like glucose and amino acids are completely absorbed from tubules. So, the urinary excretion is zero.
Ions such as Na+, Cl-, HCO3- are highly absorbed but rate of absorption and excretion varies, according to body needs.
Materials Not Reabsorbed
Nitrogenous waste products
Urea
Uric acid
Creatinine
Excess water
Reabsorption In Renal Tubule (The Guyton and Hall physiology)Maryam Fida
Features of PCTPCT have high capacity of active & passive re-absorption.
This is due to special cellular features of epithelial cells.
They have increased no. of mitochondria due to high metabolic activity.
brush border on luminal (apical) side.
Brush border contains protein carrier molecules to transport Na+ by co-transport mechanism with other substances (a.acids, glucose etc).
Additional sodium is transported by COUNTER-TRANSPORT that reabsorb sodium while secreting hydrogen.
About 65 % of filtered load of Na+ & water is reabsorbed in PCT.
A lower % age of Cl- is also absorbed.
In 1st half of PC tubules, Na+ is re-absorbed by co-transport along with glucose, a.acids and other solutes.
In 2nd half of PC tubules, mainly Na+ is reabsorbed with Cl- and some of glucose + a.acids remain un-absorbed.
2nd half of PCT has high conc of Cl- (140 mEq/L) as compared to 1st half (105 mEq/L).
Gastrointestinal hormomes & their role in secretomotor fuction of the gutRajesh Goit
This document discusses gastrointestinal hormones and their roles in regulating secretomotor function in the gut. It describes the various endocrine cells that secrete GI hormones, including enteroendocrine cells, enterochromaffin cells, and neuroendocrine cells. It provides details on major GI hormones like gastrin, cholecystokinin, secretin, glucagon, vasoactive intestinal peptide, glucose-dependent insulinotropic peptide, and somatostatin; describing where they are produced, their chemical structures, functions in regulating secretion and motility in the gut, and factors that stimulate or inhibit their secretion.
Renal tubular reabsorption, secretion, regulation & renal function testsDipti Magan
Renal tubular reabsorption and secretion involves the transport of substances across tubular epithelial cells. Substances may be reabsorbed from the tubular fluid back into the blood (reabsorption exceeds filtration) or secreted from the blood into the tubular fluid (secretion exceeds filtration). Clearance tests can measure glomerular filtration rate (GFR) and renal plasma flow. Substances like inulin that are freely filtered but not reabsorbed/secreted will have a clearance equal to GFR, while clearance of substances like para-aminohippuric acid (PAH) that are secreted can estimate renal plasma flow. Hormones and other factors regulate tubular transport and fluid/electroly
1. Renal blood flow is tightly regulated to maintain a constant rate of around 1200 mL/min despite wide changes in blood pressure, through mechanisms like autoregulation and tubuloglomerular feedback.
2. The kidneys receive a high blood flow of around 20-30% of cardiac output despite their small size, and oxygen consumption in the kidneys is very high, second only to the heart.
3. Blood enters the kidneys through the renal artery and is distributed through a branching network of arteries before entering the glomerular capillaries and surrounding the nephron tubules, with the renal veins collecting the blood and returning it to circulation.
This document discusses renal physiology, including renal blood flow, oxygen consumption, regulation of blood flow, glomerular filtration, and factors affecting glomerular filtration rate (GFR). Some key points:
- Renal blood flow is approximately 1/4 of cardiac output, or 1200 ml/min. Blood flow to the cortex is higher than to the medulla.
- Glomerular filtration is determined by the net filtration pressure and filtration coefficient. Forces increasing filtration are glomerular hydrostatic pressure and oncotic pressure in Bowman's space. Forces decreasing filtration are plasma oncotic pressure and hydrostatic pressure in Bowman's space.
- GFR is regulated through autoregulation mechanisms like tub
I am a medical student. I have one friend who is persuing his MBBS degree in Taishan Medical UNiversity. I got these notes from him.
These notes are by Dr. Bikesh, He is a famous lecturer of TMU.
These notes have helped me a lot and i also watch his lecture videos , which are great; highly simple and huge content.
I am uploading with Renal physiology. If you want some other topics i would upload for you.
"Let the Knowledge be spread" Dr. Bikesh
Tubular reabsorption (The Guyton and Hall physiology)Maryam Fida
It is the second step of urine formation.
It is defined as;
“ The process by which water and other substances are transported by renal tubules back to blood is called Tubular Reabsorption”.
Tubular reabsorption is highly selective.
Some substances like glucose and amino acids are completely absorbed from tubules. So, the urinary excretion is zero.
Ions such as Na+, Cl-, HCO3- are highly absorbed but rate of absorption and excretion varies, according to body needs.
Materials Not Reabsorbed
Nitrogenous waste products
Urea
Uric acid
Creatinine
Excess water
Reabsorption In Renal Tubule (The Guyton and Hall physiology)Maryam Fida
Features of PCTPCT have high capacity of active & passive re-absorption.
This is due to special cellular features of epithelial cells.
They have increased no. of mitochondria due to high metabolic activity.
brush border on luminal (apical) side.
Brush border contains protein carrier molecules to transport Na+ by co-transport mechanism with other substances (a.acids, glucose etc).
Additional sodium is transported by COUNTER-TRANSPORT that reabsorb sodium while secreting hydrogen.
About 65 % of filtered load of Na+ & water is reabsorbed in PCT.
A lower % age of Cl- is also absorbed.
In 1st half of PC tubules, Na+ is re-absorbed by co-transport along with glucose, a.acids and other solutes.
In 2nd half of PC tubules, mainly Na+ is reabsorbed with Cl- and some of glucose + a.acids remain un-absorbed.
2nd half of PCT has high conc of Cl- (140 mEq/L) as compared to 1st half (105 mEq/L).
Gastrointestinal hormomes & their role in secretomotor fuction of the gutRajesh Goit
This document discusses gastrointestinal hormones and their roles in regulating secretomotor function in the gut. It describes the various endocrine cells that secrete GI hormones, including enteroendocrine cells, enterochromaffin cells, and neuroendocrine cells. It provides details on major GI hormones like gastrin, cholecystokinin, secretin, glucagon, vasoactive intestinal peptide, glucose-dependent insulinotropic peptide, and somatostatin; describing where they are produced, their chemical structures, functions in regulating secretion and motility in the gut, and factors that stimulate or inhibit their secretion.
Renal tubular reabsorption, secretion, regulation & renal function testsDipti Magan
Renal tubular reabsorption and secretion involves the transport of substances across tubular epithelial cells. Substances may be reabsorbed from the tubular fluid back into the blood (reabsorption exceeds filtration) or secreted from the blood into the tubular fluid (secretion exceeds filtration). Clearance tests can measure glomerular filtration rate (GFR) and renal plasma flow. Substances like inulin that are freely filtered but not reabsorbed/secreted will have a clearance equal to GFR, while clearance of substances like para-aminohippuric acid (PAH) that are secreted can estimate renal plasma flow. Hormones and other factors regulate tubular transport and fluid/electroly
1. Renal blood flow is tightly regulated to maintain a constant rate of around 1200 mL/min despite wide changes in blood pressure, through mechanisms like autoregulation and tubuloglomerular feedback.
2. The kidneys receive a high blood flow of around 20-30% of cardiac output despite their small size, and oxygen consumption in the kidneys is very high, second only to the heart.
3. Blood enters the kidneys through the renal artery and is distributed through a branching network of arteries before entering the glomerular capillaries and surrounding the nephron tubules, with the renal veins collecting the blood and returning it to circulation.
This document discusses renal physiology, including renal blood flow, oxygen consumption, regulation of blood flow, glomerular filtration, and factors affecting glomerular filtration rate (GFR). Some key points:
- Renal blood flow is approximately 1/4 of cardiac output, or 1200 ml/min. Blood flow to the cortex is higher than to the medulla.
- Glomerular filtration is determined by the net filtration pressure and filtration coefficient. Forces increasing filtration are glomerular hydrostatic pressure and oncotic pressure in Bowman's space. Forces decreasing filtration are plasma oncotic pressure and hydrostatic pressure in Bowman's space.
- GFR is regulated through autoregulation mechanisms like tub
The document describes renal physiology and the processes of urine formation in the nephron. It discusses how solutes are transported across renal tubules through passive and active transport mechanisms. Key parts of the nephron, including the proximal tubule, loop of Henle, and collecting duct, reabsorb water and solutes like sodium, chloride, and glucose to varying degrees. The countercurrent multiplier system in the loop of Henle and transport of urea in the medullary interstitium allow the kidney to concentrate urine up to 1200-1400 mOsm/L.
Renal physiology, nephron structure, function,jga. hussein f. sakrHussein Sakr
The document provides an overview of renal physiology, including the anatomy, structure, function, and blood supply of the kidney. It describes the nephron as the functional unit of the kidney, composed of the renal corpuscle and renal tubules. There are two main types of nephrons - superficial cortical nephrons and juxtamedullary nephrons. The document also discusses the juxtaglomerular apparatus, which regulates renin release in response to changes in sodium concentration or blood pressure. Renin triggers the renin-angiotensin-aldosterone system, which functions to retain salt and water and constrict blood vessels.
The document summarizes the nervous and chemical mechanisms that regulate respiration. There are two main mechanisms:
1. The nervous mechanism involves respiratory centers in the medulla oblongata and pons that receive input from afferent nerves and control respiration through efferent nerves that stimulate the diaphragm and intercostal muscles.
2. The chemical mechanism senses changes in blood gases through central and peripheral chemoreceptors. Central chemoreceptors in the brain stem detect increased carbon dioxide, while peripheral chemoreceptors in the carotid and aortic arteries detect low oxygen levels. Both trigger the respiratory centers to increase breathing rate.
Countercurrent exchange is a mechanism where heat or chemicals are transferred between two flowing bodies moving in opposite directions, allowing for a maximum transfer. In the kidney, the countercurrent multiplier involves the reabsorption of sodium chloride along the Loop of Henle which adds to new sodium chloride, concentrating it in the medullary interstitium. Countercurrent exchange also occurs in the U-shaped vasa recta capillaries of the kidney, which helps concentrate solutes in the renal medulla through diffusion between blood and interstitial fluid flowing in opposite directions.
A comprehensive presentation on glomerular filtration rate (GFR) & renal blood flow and how these entities are impacted by intrinsic and extrinsic regulation.
This was presented by the author in the finals of the physiology seminar presentation in medical school.
The basics of autoregulation of Gloemrular filtration rate. This ppt deals with basic renal physiology, tubuloglomerular feedback, myogenic reflex, juxtaglomerular apparatus and renin angiotensin aldosterone system in brief. P.S.- The ppt has animations so kindly view in slide/presentation mode
This document provides an overview of tubular reabsorption in the kidney. It discusses the general principles of renal tubular transport, including transport across cell membranes and between epithelial cells. It describes transport across the different segments of the renal tubule, including the proximal tubule, Loop of Henle, distal tubule, and collecting duct. Key solutes discussed are sodium, chloride, potassium, bicarbonate, glucose and water. The mechanisms of action of diuretics and the renal handling of these solutes are also summarized.
The document summarizes the key structures and mechanisms involved in urine formation by the kidneys. The glomeruli, proximal canaliculi, and distal canaliculi are responsible for filtration, reabsorption, and secretion to form urine. Filtration occurs as blood is filtered in the glomeruli, producing primary urine. Most of the filtered substances are then reabsorbed back into the bloodstream in the canaliculi. Remaining substances and waste are excreted in the final urine output, with the kidneys processing around 180 L of blood filtrate per day.
Lect 3. (general principle of git motility)Ayub Abdi
The gastrointestinal smooth muscle functions as a syncytium, with individual fibers electrically connected through gap junctions. Electrical activity in the form of slow waves and spike potentials causes rhythmic contractions. Slow waves do not cause contraction directly but allow spike potentials to occur. Spike potentials cause entry of calcium ions, which bind to calmodulin and activate myosin to generate contraction. Tonic contraction is continuous and can be caused by repetitive spike potentials or other factors maintaining partial membrane depolarization.
This is a presentation about splanchinc circulation.
Done by year 3 medical students at the University of Science and Technology, Sana'a, Republic of Yemen.
Spring semester of 2010.
The document summarizes the histology of the lungs. It describes the conducting and respiratory portions of the respiratory system. In the conducting portion, it details the different cell types found in the trachea, bronchi, and bronchioles. It then discusses the respiratory portion including respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli. It notes that alveoli are lined by type I and type II alveolar cells and surrounded by capillaries, facilitating gas exchange.
Glomerular filtration rate and renal blood flow aaronpaulbaliga
This document provides an overview of renal physiology:
1. It describes the structure and function of the nephron, the basic functional unit of the kidney, and explains glomerular filtration and clearance.
2. Key concepts around glomerular filtration rate (GFR) are introduced, including how GFR is estimated and regulated through autoregulation.
3. The mechanisms of autoregulation, including myogenic and tubuloglomerular feedback responses, are summarized to maintain normal GFR and renal blood flow.
This document discusses cardiac output and the factors that affect it. It provides details on:
- Normal cardiac output values at rest and during activity.
- How the Frank-Starling mechanism and venous return primarily control cardiac output.
- Factors like metabolism, exercise, age, and body size that directly impact cardiac output.
- Pathologically high or low cardiac outputs and their underlying causes, including reduced peripheral resistance or issues with heart function.
- How cardiac output is measured and its relationship to venous return under normal conditions.
Renal blood flow (The Guyton and Hall physiology)Maryam Fida
In an average 70-kilogram man, the combined blood flow through both kidneys is about 1100 ml/min, or about 22 per cent of the cardiac output. Two kidneys makes about 0.4 % of total body weight but receive very high blood flow as compared with other body organ. The purpose of additional blood flow is to supply sufficient plasma for high rates of GF which is essential for regulating body fluid volumes & solute concentrations.
Characteristics of the renal blood flow:
1, High blood flow. 1100 ml/min, or 22 percent of the cardiac output. 94% to the cortex.
2, Two capillary beds
High hydrostatic pressure in glomerular capillary (about 60 mmHg) and low hydrostatic pressure in peritubular capillaries (about 13 mmHg)
Blood flow to renal medulla is supplied by vasa recta.
Blood flow in vasa recta of medulla is very low as compared to blood flow in cortex.
Blood flow in renal medulla is 1-2 % of total renal blood flow.
Vasa recta are important to form concentrated urine.
Gfr(glomerulur) filtration rate and its regulationsaif khan
The kidneys are located in the abdominal cavity, with the left kidney slightly higher than the right. Each kidney contains approximately 1 million nephrons, the functional units that filter blood. The glomerulus is a ball of capillaries in each nephron that filters about 3-4 liters of blood per minute, producing 125 ml of filtrate per minute called glomerular filtration. Filtration occurs through endothelial cells in capillaries, the basement membrane, and epithelial cells lining Bowman's capsule. Key factors in filtration include hydrostatic and oncotic pressures between the glomerulus and Bowman's capsule, maintaining a net filtration pressure of 8 mmHg for fluid to pass from the glomerulus
EVENTS OF URINE FORMATION (The Guyton and Hall physiology)Maryam Fida
FILTRATION.
REABSORPTION
SECRETION
FILTRATION is the function of the glomerulus.
Reabsorption and secretion are the functions of tubular portion of nephron.
It is the first process of urine formation.
DEFINITION
“ The process by which the blood that passes through glomerular capillaries is filtered Formed by three layers.
Glomerular capillary membrane.
Basement membrane
visceral layer of Bowman’s capsule.
Glomerular Filtration Rate (GFR)
“The rate at which plasma is filtered into Bowman's capsule.
The units of filtration are a volume filtered per unit time, e.g. ml/min or liters/day.
Normal Value is 125ml/min or 180 liters/day.
99% of filtrate is reabsorbed, 1 to 2 L is excreted as urine.
The document summarizes the juxtaglomerular apparatus (JGA) and tubuloglomerular feedback mechanism. The JGA is located near the glomerulus and is formed by macula densa cells, extraglomerular mesangial cells, and juxtaglomerular cells. The primary function of the JGA is secretion of hormones like renin and prostaglandins. The tubuloglomerular feedback mechanism regulates glomerular filtration rate through detection of NaCl concentration by the macula densa cells, which signals the release of adenosine to constrict or dilate the afferent arteriole accordingly.
The document discusses the physiology of the kidneys, describing their role in maintaining homeostasis through functions like regulating water balance and electrolyte concentrations, as well as their internal structure including nephrons and the processes of glomerular filtration, reabsorption of water and salts, and production of urine. Key concepts covered include kidney anatomy, the roles of different kidney structures like the nephron and collecting duct, and physiological mechanisms involved in filtration, reabsorption, and regulation of fluids and electrolytes.
This document provides information on the structure and function of the kidney and renal circulation. It discusses the basic anatomy of the nephron and its parts including the glomerulus, proximal convoluted tubule, loop of Henle, distal convoluted tubule and collecting duct. It also describes the juxtaglomerular apparatus and its role in regulating blood pressure via the renin-angiotensin system. Regarding renal circulation, it notes the kidney receives a high blood flow and has a unique portal system, as well as features like autoregulation and high oxygen consumption.
The countercurrent mechanism in the kidney produces a hyperosmotic renal medullary interstitium through three key processes: 1) the countercurrent multiplier effect of the thick ascending loop of Henle which repetitively reabsorbs sodium chloride, 2) active transport of ions from the collecting ducts into the medullary interstitium, and 3) facilitated diffusion of urea from the inner medullary collecting ducts into the medullary interstitium. This hyperosmotic interstitium is maintained by the countercurrent exchange function of the vasa recta blood vessels.
The document summarizes key functions and processes of the kidneys. The kidneys maintain water and electrolyte balance, acid-base balance, excrete wastes and foreign substances, produce hormones, and more. The functional unit is the nephron, which filters blood and modifies the filtrate through reabsorption and secretion to form urine. Glomerular filtration occurs through specialized capillaries, with the filtrate entering Bowman's capsule. Tubular reabsorption and secretion then alter the filtrate composition as it passes through the nephron tubule.
The document provides an overview of kidney anatomy and physiology. It discusses the gross external anatomy of the kidney including its location, layers of surrounding tissue, and vasculature. It then describes the internal anatomy including the functional unit of the kidney called the nephron. Key processes of urine formation are summarized such as glomerular filtration, tubular reabsorption and secretion. Specific examples of substance handling by the kidney like glucose, sodium, and water are outlined. Mechanisms of renal regulation including autoregulation and the roles of the renin-angiotensin-aldosterone system are briefly explained.
The document describes renal physiology and the processes of urine formation in the nephron. It discusses how solutes are transported across renal tubules through passive and active transport mechanisms. Key parts of the nephron, including the proximal tubule, loop of Henle, and collecting duct, reabsorb water and solutes like sodium, chloride, and glucose to varying degrees. The countercurrent multiplier system in the loop of Henle and transport of urea in the medullary interstitium allow the kidney to concentrate urine up to 1200-1400 mOsm/L.
Renal physiology, nephron structure, function,jga. hussein f. sakrHussein Sakr
The document provides an overview of renal physiology, including the anatomy, structure, function, and blood supply of the kidney. It describes the nephron as the functional unit of the kidney, composed of the renal corpuscle and renal tubules. There are two main types of nephrons - superficial cortical nephrons and juxtamedullary nephrons. The document also discusses the juxtaglomerular apparatus, which regulates renin release in response to changes in sodium concentration or blood pressure. Renin triggers the renin-angiotensin-aldosterone system, which functions to retain salt and water and constrict blood vessels.
The document summarizes the nervous and chemical mechanisms that regulate respiration. There are two main mechanisms:
1. The nervous mechanism involves respiratory centers in the medulla oblongata and pons that receive input from afferent nerves and control respiration through efferent nerves that stimulate the diaphragm and intercostal muscles.
2. The chemical mechanism senses changes in blood gases through central and peripheral chemoreceptors. Central chemoreceptors in the brain stem detect increased carbon dioxide, while peripheral chemoreceptors in the carotid and aortic arteries detect low oxygen levels. Both trigger the respiratory centers to increase breathing rate.
Countercurrent exchange is a mechanism where heat or chemicals are transferred between two flowing bodies moving in opposite directions, allowing for a maximum transfer. In the kidney, the countercurrent multiplier involves the reabsorption of sodium chloride along the Loop of Henle which adds to new sodium chloride, concentrating it in the medullary interstitium. Countercurrent exchange also occurs in the U-shaped vasa recta capillaries of the kidney, which helps concentrate solutes in the renal medulla through diffusion between blood and interstitial fluid flowing in opposite directions.
A comprehensive presentation on glomerular filtration rate (GFR) & renal blood flow and how these entities are impacted by intrinsic and extrinsic regulation.
This was presented by the author in the finals of the physiology seminar presentation in medical school.
The basics of autoregulation of Gloemrular filtration rate. This ppt deals with basic renal physiology, tubuloglomerular feedback, myogenic reflex, juxtaglomerular apparatus and renin angiotensin aldosterone system in brief. P.S.- The ppt has animations so kindly view in slide/presentation mode
This document provides an overview of tubular reabsorption in the kidney. It discusses the general principles of renal tubular transport, including transport across cell membranes and between epithelial cells. It describes transport across the different segments of the renal tubule, including the proximal tubule, Loop of Henle, distal tubule, and collecting duct. Key solutes discussed are sodium, chloride, potassium, bicarbonate, glucose and water. The mechanisms of action of diuretics and the renal handling of these solutes are also summarized.
The document summarizes the key structures and mechanisms involved in urine formation by the kidneys. The glomeruli, proximal canaliculi, and distal canaliculi are responsible for filtration, reabsorption, and secretion to form urine. Filtration occurs as blood is filtered in the glomeruli, producing primary urine. Most of the filtered substances are then reabsorbed back into the bloodstream in the canaliculi. Remaining substances and waste are excreted in the final urine output, with the kidneys processing around 180 L of blood filtrate per day.
Lect 3. (general principle of git motility)Ayub Abdi
The gastrointestinal smooth muscle functions as a syncytium, with individual fibers electrically connected through gap junctions. Electrical activity in the form of slow waves and spike potentials causes rhythmic contractions. Slow waves do not cause contraction directly but allow spike potentials to occur. Spike potentials cause entry of calcium ions, which bind to calmodulin and activate myosin to generate contraction. Tonic contraction is continuous and can be caused by repetitive spike potentials or other factors maintaining partial membrane depolarization.
This is a presentation about splanchinc circulation.
Done by year 3 medical students at the University of Science and Technology, Sana'a, Republic of Yemen.
Spring semester of 2010.
The document summarizes the histology of the lungs. It describes the conducting and respiratory portions of the respiratory system. In the conducting portion, it details the different cell types found in the trachea, bronchi, and bronchioles. It then discusses the respiratory portion including respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli. It notes that alveoli are lined by type I and type II alveolar cells and surrounded by capillaries, facilitating gas exchange.
Glomerular filtration rate and renal blood flow aaronpaulbaliga
This document provides an overview of renal physiology:
1. It describes the structure and function of the nephron, the basic functional unit of the kidney, and explains glomerular filtration and clearance.
2. Key concepts around glomerular filtration rate (GFR) are introduced, including how GFR is estimated and regulated through autoregulation.
3. The mechanisms of autoregulation, including myogenic and tubuloglomerular feedback responses, are summarized to maintain normal GFR and renal blood flow.
This document discusses cardiac output and the factors that affect it. It provides details on:
- Normal cardiac output values at rest and during activity.
- How the Frank-Starling mechanism and venous return primarily control cardiac output.
- Factors like metabolism, exercise, age, and body size that directly impact cardiac output.
- Pathologically high or low cardiac outputs and their underlying causes, including reduced peripheral resistance or issues with heart function.
- How cardiac output is measured and its relationship to venous return under normal conditions.
Renal blood flow (The Guyton and Hall physiology)Maryam Fida
In an average 70-kilogram man, the combined blood flow through both kidneys is about 1100 ml/min, or about 22 per cent of the cardiac output. Two kidneys makes about 0.4 % of total body weight but receive very high blood flow as compared with other body organ. The purpose of additional blood flow is to supply sufficient plasma for high rates of GF which is essential for regulating body fluid volumes & solute concentrations.
Characteristics of the renal blood flow:
1, High blood flow. 1100 ml/min, or 22 percent of the cardiac output. 94% to the cortex.
2, Two capillary beds
High hydrostatic pressure in glomerular capillary (about 60 mmHg) and low hydrostatic pressure in peritubular capillaries (about 13 mmHg)
Blood flow to renal medulla is supplied by vasa recta.
Blood flow in vasa recta of medulla is very low as compared to blood flow in cortex.
Blood flow in renal medulla is 1-2 % of total renal blood flow.
Vasa recta are important to form concentrated urine.
Gfr(glomerulur) filtration rate and its regulationsaif khan
The kidneys are located in the abdominal cavity, with the left kidney slightly higher than the right. Each kidney contains approximately 1 million nephrons, the functional units that filter blood. The glomerulus is a ball of capillaries in each nephron that filters about 3-4 liters of blood per minute, producing 125 ml of filtrate per minute called glomerular filtration. Filtration occurs through endothelial cells in capillaries, the basement membrane, and epithelial cells lining Bowman's capsule. Key factors in filtration include hydrostatic and oncotic pressures between the glomerulus and Bowman's capsule, maintaining a net filtration pressure of 8 mmHg for fluid to pass from the glomerulus
EVENTS OF URINE FORMATION (The Guyton and Hall physiology)Maryam Fida
FILTRATION.
REABSORPTION
SECRETION
FILTRATION is the function of the glomerulus.
Reabsorption and secretion are the functions of tubular portion of nephron.
It is the first process of urine formation.
DEFINITION
“ The process by which the blood that passes through glomerular capillaries is filtered Formed by three layers.
Glomerular capillary membrane.
Basement membrane
visceral layer of Bowman’s capsule.
Glomerular Filtration Rate (GFR)
“The rate at which plasma is filtered into Bowman's capsule.
The units of filtration are a volume filtered per unit time, e.g. ml/min or liters/day.
Normal Value is 125ml/min or 180 liters/day.
99% of filtrate is reabsorbed, 1 to 2 L is excreted as urine.
The document summarizes the juxtaglomerular apparatus (JGA) and tubuloglomerular feedback mechanism. The JGA is located near the glomerulus and is formed by macula densa cells, extraglomerular mesangial cells, and juxtaglomerular cells. The primary function of the JGA is secretion of hormones like renin and prostaglandins. The tubuloglomerular feedback mechanism regulates glomerular filtration rate through detection of NaCl concentration by the macula densa cells, which signals the release of adenosine to constrict or dilate the afferent arteriole accordingly.
The document discusses the physiology of the kidneys, describing their role in maintaining homeostasis through functions like regulating water balance and electrolyte concentrations, as well as their internal structure including nephrons and the processes of glomerular filtration, reabsorption of water and salts, and production of urine. Key concepts covered include kidney anatomy, the roles of different kidney structures like the nephron and collecting duct, and physiological mechanisms involved in filtration, reabsorption, and regulation of fluids and electrolytes.
This document provides information on the structure and function of the kidney and renal circulation. It discusses the basic anatomy of the nephron and its parts including the glomerulus, proximal convoluted tubule, loop of Henle, distal convoluted tubule and collecting duct. It also describes the juxtaglomerular apparatus and its role in regulating blood pressure via the renin-angiotensin system. Regarding renal circulation, it notes the kidney receives a high blood flow and has a unique portal system, as well as features like autoregulation and high oxygen consumption.
The countercurrent mechanism in the kidney produces a hyperosmotic renal medullary interstitium through three key processes: 1) the countercurrent multiplier effect of the thick ascending loop of Henle which repetitively reabsorbs sodium chloride, 2) active transport of ions from the collecting ducts into the medullary interstitium, and 3) facilitated diffusion of urea from the inner medullary collecting ducts into the medullary interstitium. This hyperosmotic interstitium is maintained by the countercurrent exchange function of the vasa recta blood vessels.
The document summarizes key functions and processes of the kidneys. The kidneys maintain water and electrolyte balance, acid-base balance, excrete wastes and foreign substances, produce hormones, and more. The functional unit is the nephron, which filters blood and modifies the filtrate through reabsorption and secretion to form urine. Glomerular filtration occurs through specialized capillaries, with the filtrate entering Bowman's capsule. Tubular reabsorption and secretion then alter the filtrate composition as it passes through the nephron tubule.
The document provides an overview of kidney anatomy and physiology. It discusses the gross external anatomy of the kidney including its location, layers of surrounding tissue, and vasculature. It then describes the internal anatomy including the functional unit of the kidney called the nephron. Key processes of urine formation are summarized such as glomerular filtration, tubular reabsorption and secretion. Specific examples of substance handling by the kidney like glucose, sodium, and water are outlined. Mechanisms of renal regulation including autoregulation and the roles of the renin-angiotensin-aldosterone system are briefly explained.
Physiology of urine formation and kidney function test swati mamDr Praman Kushwah
The document discusses the physiology of urine formation and relevant kidney functions. It covers:
1. The kidneys filter plasma and remove substances at variable rates depending on body needs. Their main functions include waste excretion, fluid and electrolyte balance, and blood pressure regulation.
2. Urine is formed through glomerular filtration, tubular reabsorption of useful substances back into blood, and tubular secretion of other substances into urine.
3. Glomerular filtration rate (GFR) is the best test to assess kidney function and is used to diagnose and monitor kidney disease. A normal GFR depends on renal blood flow and pressure.
The document provides an overview of the urinary system and kidney anatomy and physiology. It discusses the key functions of the urinary system including excretion of wastes and regulation of water, electrolytes, and acid-base balance. It describes the anatomy of the kidneys, nephrons, blood supply, and details of glomerular filtration, tubular reabsorption and secretion processes. Intrinsic and extrinsic controls maintain glomerular filtration rate and blood pressure homeostasis.
This document discusses glomerular filtration and the glomerular filtration rate (GFR). It defines glomerular filtration as the process where plasma filters through the glomerular capillaries into Bowman's capsule, the first step in urine formation. The GFR is the rate at which plasma is filtered and is an important measurement of kidney function. Normal GFR is about 125 mL/min. The kidneys filter the plasma around 60 times per day. Renal blood flow to the kidneys is high at around 1200 mL/min and is regulated by the afferent and efferent arterioles. Glomerular filtration is governed by the filtration coefficient and Starling forces of hydrostatic and oncotic pressures
This document discusses glomerular filtration and the glomerular filtration rate (GFR). It notes that glomerular filtration is the first step in urine formation where plasma filters through the glomerular capillaries into Bowman's capsule. The GFR is the rate at which plasma is filtered by the kidney glomeruli and is an important measurement of kidney function. The GFR is regulated by factors like renal blood flow, glomerular pressure, and the filtration coefficient which depends on capillary permeability and the size of the capillary bed. Changes in various physiological conditions can impact the GFR.
The kidneys perform several important functions including filtering the blood to remove waste and regulate fluid levels. The functional unit of the kidney is the nephron, which contains a glomerulus that filters blood and tubules that modify the filtrate. Urine is formed through glomerular filtration, tubular reabsorption of useful substances back into blood, and tubular secretion of wastes into urine. Precise regulation of filtration, reabsorption and secretion allows the kidneys to maintain fluid and electrolyte balance.
The urinary system filters wastes from the blood and regulates fluid balance. The kidneys contain nephrons which filter blood to form urine. Urine passes from nephrons to the bladder through ureters for storage and eventual elimination. Key functions of the kidneys include filtering wastes, regulating fluid and electrolyte balance, and producing hormones. Urine is formed through glomerular filtration, tubular reabsorption and secretion, and concentration in the collecting duct.
The document provides an introduction to the excretory system, focusing on the anatomy and functions of the kidney. It discusses the following key points:
1. The kidneys regulate homeostasis through fluid balance, electrolyte balance, acid-base balance, and blood pressure regulation. They also excrete metabolic waste and secrete important hormones and vitamins.
2. Each kidney contains around 1 million nephrons, each with a glomerulus for blood filtration and a tubule for reabsorption and secretion.
3. Glomerular filtration occurs through small pores in the filtration membrane, allowing filtration of plasma while retaining blood cells and proteins. Around 180L of filtrate is produced per day through this process.
The document discusses renal physiology, specifically kidney function and structure. It covers 4 main points:
1. The kidneys regulate water and electrolyte balance, excrete waste, and secrete hormones like erythropoietin and renin.
2. The functional unit of the kidney is the nephron, which filters blood in the glomerulus and reabsorbs and secretes solutes along the renal tubule.
3. Glomerular filtration and tubular reabsorption and secretion precisely regulate urine composition to maintain homeostasis.
4. Kidney blood flow is regulated through autoregulation, neural, and hormonal mechanisms like the renin-angiotensin system to control
The document discusses the major functions and physiological anatomy of the kidney. It notes that the kidney's main regulatory functions include excretion of waste, water/electrolyte balance, blood pressure regulation, and acid-base balance. The functional unit of the kidney is the nephron, which filters blood to form urine via glomerular filtration, tubular reabsorption, and tubular secretion. Glomerular filtration is driven by hydrostatic and oncotic pressures across the glomerular membrane, resulting in an ultrafiltrate that is further processed as it passes through the nephron tubules to form the final urine.
The nephron is the basic functional unit of the kidneys that filters blood to form urine. Each nephron contains a glomerulus for blood filtration and a tubule that modifies the filtrate. There are two types of nephrons - cortical and juxtamedullary. The glomerular capillary membrane filters fluid which passes through the tubule and is further processed, regulated and concentrated to form urine through selective reabsorption and secretion processes along the tubule. The kidneys regulate fluid and electrolyte balance and excrete wastes through precisely controlling glomerular filtration rate and the reabsorption of useful solutes back into the bloodstream from the filtrate in the tubule.
The kidneys are a pair of highly vascular organs located in the lower back that filter waste from the blood and regulate fluid balance. They each contain around 1-1.5 million nephrons, the functional units of the kidney. The kidneys receive a high blood flow and precisely regulate glomerular filtration rate, reabsorption, and secretion to produce urine with the proper electrolyte and water content. Various tests can evaluate renal function by measuring glomerular filtration rate, tubular handling, or the levels of substances such as creatinine, urea, and electrolytes. Acute kidney injury is characterized by a sudden deterioration of renal function over hours to days that impairs waste excretion and fluid/electro
The kidneys perform four main functions: 1) maintaining water, electrolyte, and acid-base balance; 2) excreting waste products; 3) producing hormones; and 4) participating in metabolism. The kidneys filter the blood to form urine via glomerular filtration in the nephrons. Most filtered materials are reabsorbed, while wastes are excreted. Tubular reabsorption is regulated to maintain homeostasis and is achieved through passive diffusion, active transport, and carrier proteins. The glomerular filtration rate indicates kidney function by measuring the volume of filtrate formed per minute.
The document summarizes the mechanism of urine formation, which involves three major processes: 1) Glomerular filtration, where plasma is ultra-filtered in the glomerulus. Filtration is governed by the filtration coefficient and Starling forces. 2) Tubular reabsorption, where essential substances like glucose and amino acids are selectively reabsorbed in the tubules. 3) Tubular secretion, where unwanted substances are transported from blood into the tubules and excreted in urine. Urine passes through the nephrons, collecting ducts, renal pelvis, ureters and bladder before exiting the body.
The nephron is the functional unit of the kidney that filters blood to form urine. Glomerular filtration occurs as blood plasma passes through the glomerular membrane into Bowman's capsule. The glomerular filtration rate (GFR) is determined by the net filtration pressure across the membrane. GFR is regulated by the constriction and dilation of the afferent and efferent arterioles, which alter glomerular capillary hydrostatic pressure. Factors such as sympathetic stimulation, angiotensin II, blood pressure, protein intake, and blood glucose levels can impact GFR through their effects on renal blood flow and arteriolar resistance.
The nephron is the functional unit of the kidney, which filters blood to form urine. The nephron contains a glomerulus that filters the blood and a renal tubule that reabsorbs most of the filtered water and solutes. Key functions of the nephron include filtering the blood at the glomerulus and reabsorbing various substances like water, glucose, amino acids, salts, and urea along different portions of the renal tubule under hormonal control. The kidney plays an important role in regulating fluid and electrolyte balance, excreting wastes, and producing hormones.
The renal system is composed of kidneys, renal pelvises, ureters, urinary bladder, and urethra. The nephron is the functional unit of the kidney, containing a renal corpuscle and renal tubules. Urine is formed via glomerular filtration, tubular reabsorption, and tubular excretion. Glucose is completely reabsorbed in the proximal convoluted tubule via secondary active transport with sodium. The maximum renal threshold for glucose reabsorption is 225 mg/dL, above which glucosuria occurs.
The kidneys are bean-shaped organs located in the posterior abdominal cavity that filter blood and produce urine. The kidneys contain millions of nephrons, which are the functional units that filter blood to form urine. During filtration, water and soluble waste products pass from blood into Bowman's capsule, while proteins and other large molecules are retained. As the filtrate passes through the nephron's tubule, certain substances are reabsorbed back into blood while others are actively secreted into the tubule from surrounding blood vessels. This finely tuned process of filtration, reabsorption and secretion produces urine with the proper concentration of waste products and electrolytes for excretion from the body.
Khushi Saini, An Intern from The Sparks Foundationkhushisaini0924
This is my first task as an Talent Acquisition(Human resources) Intern in The Sparks Foundation on Recruitment, article and posts.
I invitr everyone to look into my work and provide me a quick feedback.
Section 79(A) of Maharashtra Societies act 1860ManmohanJindal1
Lot of redevelopment projects are going on, where law and procedures are not followed , causing harm to the members of the society . This PPT is useful for every citizen living in society Building
6. • The renal artery --
segmental arteries --
interlobar arteries
that communicate
with one another via
arcuate arteries.
• The arcuate arteries
give off branches
called interlobular
arteries that extend
into the cortex.
• Venous return of
blood is via similarly
named veins.
7. • The interlobular
arteries --afferent
arterioles --
glomerulus - efferent
arterioles --capillary
network surrounding
the tubule system of
the nephron.
• The interlobular veins
are then the collecting
vessel of the nephron
capillary system.
8. Characteristics of the renal
blood flow:
1, high blood flow. 1200
ml/min, or 21 percent of the
cardiac output. 94% to the
cortex
2, Two capillary beds
High hydrostatic pressure in
glomerular capillary (about
60 mmHg) and low
hydrostatic pressure in
peritubular capillaries (about
13 mmHg)
9. 1.Nephron and
Collecting Duct
Nephron: The functional
unit of the kidney
Each kidney is made up of
about 1.3 million
nephrons
Each nephrons has two
major components:
1) A glomerulus
2) A long tube
10. The Nephron
Blood flow -
afferent arteriole
efferent arteriole
Peritubular capillaries
vasa recta
•Structure of nephron
–glomerulus
–proximal
convoluted
tubule (pct)
–loop of Henle
•descending
limb
•ascending
limb
–distal
convoluted
tubule
•many nephrons
connect to collecting
duct
12. Anatomy of Kidney
Cortical nephron – glomeruli in outer cortex & short
loops of Henle that extend only short distance into
medulla-- blood flow through cortex is rapid – majority
of nephrons are cortical – cortical interstitial fluid 300
mOsmolar
Juxtamedullary nephron – glomeruli in inner part of
cortex & long loops of Henle which extend deeply
into medulla.– blood flow through vasa recta in medulla
is slow – medullary interstitial fluid is hyperosmotic –
this nephron maintains osmolality in addition to filtering
blood and maintaining acid-base balance
15. 2. The juxtaglomerular apparatus
Including macula densa, extraglumerular mesangial cells, and
juxtaglomerular (granular cells) cells
16. Functions of the Nephron
Filtration
Reabsorption Secretion
Excretion
17. How the nephrons function
• Four Main Processes:
– Filtration
– Reabsorbtion
– Secretion
– Excretion
18. • Functions of the Kidney:
– Filtration:
–First step in urine formation
–Bulk transport of fluid from blood to
kidney tubule
» Isosmotic filtrate
» Blood cells and proteins don’t filter
–Result of hydraulic pressure
–GFR = 180 L/day
19. • Functions of the Kidney:
– Reabsorbtion:
• Process of returning filtered material to
bloodstream
• 99% of what is filtered
• May involve transport protein(s)
• Normally glucose is totally reabsorbed
20. • Functions of the Kidney:
– Secretion:
– Material added to lumen of kidney from blood
– Active transport (usually) of toxins and foreign
substances
» Drugs e.g. Penicillin
21. • Functions of the Kidney:
– Excretion:
– Loss of fluid from body in form of urine
Amount = Amount + Amount -- Amount
of Solute Filtered Secreted Reabsorbed
Excreted
22. Glomerular Filtration
Glomerular membrane
Glomerular filtration rate (GFR)
Determinants of GFR
Renal Blood flow (RBF) and GFR
Autoregulation of blood flow and glomerular filtration
23. – blood enters glomerular capillary
– filters out of renal corpuscle
• large proteins and cells stay behind
• everything else is filtered into nephron
• glomerular filtrate
– plasma like fluid in glomerulus
Glomerular filtration
Occurs as fluids move
across the glomerular
capillary in response
to glomerular
hydrostatic pressure
24. Factors that determine the
glumerular filterability
1.Molecular weight
2.Charges of the molecule
25. Filtration Membrane
–One layer of glomerular capillary cells
–Basement membrane(lamina densa)
–One layer of cells in Bowman’s capsule: Podocytes have
foot like projections(pedicels) with filtration slits in between
C: capillary
BM: basal
membrane
P podocytes
FS: filtration
slit
26. Constituent Mol. Wt. Filteration
ratio
Urea 60 1.00
Glucose 180 1.00
Inulin 5,500 1.00
Myoglobin 17,000 0.75
Hemoglobin 64,000 0.03
Serum albumin 69,000 0.01
Filterablility of plasma constituents vs. water
31. • Amount of filtrate produced in the kidneys
each minute. 125mL/min = 180L/day
• Factors that alter filtration pressure change
GFR. These include:
– Increased renal blood flow -- Increased GFR
– Decreased plasma protein -- Increased GFR. Causes
edema.
– Hemorrhage -- Decreased capillary BP -- Decreased
GFR
Glomerular filtration rate (GFR)
32. GFR regulation : Adjusting blood
flow
• GFR is regulated using three mechanisms
1. Renal Autoregulation
2. Neural regulation
3. Hormonal regulation
All three mechanism adjust renal blood pressure
and resulting blood flow
37. 2. Neural regulation of GFR
• Sympathetic nerve fibers innervate afferent and
efferent arteriole
• Normally sympathetic stimulation is low but can
increase during hemorrhage and exercise
• Vasoconstriction occurs as a result which
conserves blood volume(hemorrhage)and permits
greater blood flow to other body parts(exercise)
38. 3. Hormonal regulation of GFR
• Several hormones contribute to GFR regulation
• Angiotensin II. Produced by Renin, released by
JGA cells is a potent vasoconstrictor. Reduces
GFR
• ANP(released by atria when stretched) increases
GFR by increasing capillary surface area
available for filtration
• NO
• Endothelin
• Prostaglandin E2
39. Renal Clearance
Volume of plasma cleared of a substance by the kidney per minute
Clearance of substance Y is the vol of plasma that would have to be
cleared of substance Y appearing in urine per unit time
i.e Plasma X Vol of plasma =Urine X Vol of urine
conc cleared per min Con per min
PY X CY = VY X V
Where:-
PY=Conc of subst Y in plasma
VY=“ ” ” ” ” urine
CY=Vol of plasma cleared of subst Y per min or clearance of subst Y
V= Vol of urine per min
Therefore:- CY = VY X V
PY
40. Renal handling of inulin
Amount filtered = Amount excreted
Pin x GFR Uin x V
41. Qualities of agents to measure GFR
Inulin: (Polysaccharide from Dahalia plant)
• Freely filterable at glomerulus
• Does not bind to plasma proteins
• Biologically inert
• Non-toxic, neither synthesized nor metabolized in
kidney
• Neither absorbed nor secreted
• Does not alter renal function
• Can be accurately quantified
• Low concentrations are enough (10-20 mg/100 ml
plasma)
42. Creatinine:
End product of muscle creatine metabolism
Used in clinical setting to measure GFR but less
accurate than inulin method
Small amount secrete from the tubule
Qualities of agents to measure GFR
50. Secondary active transport
Na+
glucose
Na+
H+
out in out in
co-transport counter-transport
(symport) (antiport)
Co-transporters will move one
moiety, e.g. glucose, in the same
direction as the Na+.
Counter-transporters will move
one moiety, e.g. H+, in the
opposite direction to the Na+.
Tubular
lumen
Tubular Cell
Interstitial
Fluid
Tubular
lumen
Tubular Cell
Interstitial
Fluid
51. Pinocytosis:
Some parts of the tubule, especially the
proximal tubule, reabsorb large molecules
such as proteins by pinocytosis.
53. 1. Transportation of Sodium, Water and
Chloride
(1)Sodium, water and chloride reabsorption in
proximal tubule
Proximal tubule, including the proximal convoluted
tubule and thick descending segment of the loop
54. Reabsorb about 65 percent of the filtered sodium, chloride, bicarbonate,
and potassium and essentially al the filtered glucose and amino acids.
Secrete organic acids, bases, and hydrogen ions into the tubular lumen.
55. The sodium-potassium ATPase: major force for reabsorption
of sodium, chloride and water
In the first half of the proximal tubule, sodium is reabsorbed
by co-transport along with glucose, amino acids, and other
solutes.
In the second half of the proximal tubule, sodium reabsorbed
mainly with chloride ions.
Sodium, water and chloride reabsorption in
proximal tubule
56. The second half of the proximal tubule has a relatively high
concentration of chloride (around 140mEq/L) compared with
the early proximal tubule (about 105 mEq/L)
In the second half of the proximal tubule, the higher chloride
concentration favors the diffusion of this ion from the tubule
lumen through the intercellular junctions into the renal
interstitial fluid.
Sodium, water and chloride reabsorption in
proximal tubule
57. (2) Sodium and water transport in the loop
of Henle
The loop of Henle consists of three functionally
distinct segments:
the thin descending segment,
the thin ascending segment,
and the thick ascending segment.
58. High permeable to water
and moderately permeable
to most solutes
but has few mitochondria
and little or no active
reabsorption.
Reabsorbs about 25% of the
filtered loads of sodium,
chloride, and potassium, as
well as large amounts of
calcium, bicarbonate, and
magnesium.
This segment also secretes
hydrogen ions into the
tubule
60. 2. Glucose Reabsorption
Glucose is reabsorbed along with Na+ in the early
portion of the proximal tubule.
Glucose is typical of substances removed from the
urine by secondary active transport.
Essentially all of the glucose is reabsorbed, and no
more than a few milligrams appear in the urine per 24
hours.
61. The amount reabsorbed is proportionate to the amount
filtered and hence to the plasma glucose level (PG)
times the GFR up to the transport maximum (TmG);
But when the TmG is exceed, the amount of glucose in
the urine rises
The TmG is about 375 mg/min in men and 300 mg/min
in women.
62. GLUCOSE REABSORPTION HAS A
TUBULAR MAXIMUM
Renal threshold (300mg/100 ml)
Plasma Concentration of Glucose
Glucose
Reabsorbed
mg/min
Filtered Excreted
Reabsorbed
63. The renal threshold for glucose is the plasma level at
which the glucose first appears in the urine.
One would predict that the renal threshold would be
about 300 mg/dl – ie, 375 mg/min (TmG) divided by
125 mL/min (GFR).
However, the actual renal threshold is about 200
mg/dL of arterial plasma, which corresponds to a
venous level of about 180 mg/dL.
64. Top: Relationship
between the plasma
level (P) and excretion
(UV) of glucose and
inulin
Bottom: Relationship
between the plasma
glucose level (PG) and
amount of glucose
reabsorbed (TG).
65. 3. Hydrogen Secretion and Bicarbonate
Reabsorption.
(1)Hydrogen secretion through secondary Active
Transport.
Mainly at the proximal tubules, loop of Henle, and
early distal tubule ;
More than 90 percent of the bicarbonate is reabsorbed
(passively ) in this manner .
67. (2) Primary Active Transport
Beginning in the late distal tubules and continuing
through the reminder of the tubular system
It occurs at the luminal membrane of the tubular cell
Hydrogen ions are transported directly by a specific
protein, a hydrogen-transporting ATPase (proton
pump).
69. Hydrogen Secretion—through proton pump:
accounts for only about 5 percent of the total hydrogen
ion secreted
Important in forming a maximally acidic urine.
Hydrogen ion concentration can be increased as much
as 900-fold in the collecting tubules.
Decreases the pH of the tubular fluid to about 4.5,
which is the lower limit of pH that can be achieved in
normal kidneys.
70. 4. Excretion of Excess Hydrogen Ions and
Generation of New Bicarbonate by the
Ammonia Buffer System
72. For each molecule of glutamine metabolized in the
proximal tubules, two NH4
+ ions are secreted into the
urine and two HCO3
- ions are reabsorbed into the
blood.
The HCO3
- generated by this process constitutes new
bicarbonate.
74. Renal ammonium-ammonia buffer system is subject to
physiological control.
An increase in extracellular fluid hydrogen ion
concentration stimulates renal glutamine metabolism
and, therefore, increase the formation of NH4
+ and
new bicarbonate to be used in hydrogen ion buffering;
a decrease in hydrogen ion concentration has the
opposite effect.
75. with chronic acidosis, the dominant mechanism by
which acid is eliminated of NH4
+.
This also provides the most important mechanism for
generating new bicarbonate during chronic acidosis.
77. Mechanisms of potassium secretion and sodium reabsorption
by the principle cells of the late distal and collecting tubules.
78. 6. Control of Calcium Excretion by the Kidneys
(1)Calcium is both filtered and reabsorbed in the kidneys but
not secreted
(2)Only about 50 per cent of the plasma calcium is ionized,
with the remainder being bound to the plasma proteins.
(3)Calcium excretion is adjusted to meet the body’s needs.
(4)Parathyroid hormone (PTH) increases calcium reabsorption
in the thick ascending lops of Henle and distal tubules, and
reduces urinary excretion of calcium
80. Section 4. Urine Concentration and Dilution
Importance:
When there is excess water in the body and body fluid
osmolarity is reduced, the kidney can excrete urine with an
osmolarity as low as 50 mOsm/liter, a concentration that is
only about one sixth the osmolarity of normal extracellular
fluid.
Conversely, when there is a deficient of water and
extracellular fluids osmolarity is high, the kidney can excrete
urine with a concentration of about 1200 to 1400 mOsm/liter.
81. The basic requirements for forming a
concentrated or diluted urine
(1) the controlled secretion of antidiuretic hormone (ADH),
which regulates the permeability of the distal tubules and
collecting ducts to water;
(2) a high osmolarity of the renal medullary interstitial fluid,
which provides the osmotic gradient necessary for water
reabsorption to occur in the presence of high level of ADH.
82.
83. I The Counter-Current Mechanism
Produces a Hyperosmotic Renal
Medullary Interstitium
90. The vasa
recta trap
salt and urea
within the
interstitial
fluid but
transport
water out of
the renal
medulla
91. III. Role of the Distal Tubule and
Collecting Ducts in Forming
Concentrated or Diluted urine
92. Figure 26.15a, b
The Effects of ADH on the distal collecting
duct and Collecting Ducts
93. The Role of ADH
• There is a high osmolarity of the renal medullary interstitial
fluid, which provides the osmotic gradient necessary for
water reabsorption to occur.
• Whether the water actually leaves the collecting duct (by
osmosis) is determined by the hormone ADH (anti-diuretic
hormone)
• Osmoreceptors in the hypothalamus detect the low levels of
water (high osmolarity), so the hypothalamus sends an
impulse to the pituitary gland which releases ADH into the
bloodstream.
• ADH makes the wall of the collecting duct more permeable
to water.
• Therefore, when ADH is present more water is reabsorbed
and less is excreted.
94. Water reabsorption - 1
Obligatory water reabsorption:
• Using sodium and other solutes.
• Water follows solute to the interstitial fluid
(transcellular and paracellular pathway).
• Largely influenced by sodium reabsorption
96. Facultative (selective) water reabsorption:
• Occurs mostly in collecting ducts
• Through the water poles (channel)
• Regulated by the ADH
Water reabsorption - 2
100. Regulation of the Urine Formation
I. Autoregulation of the renal
reabsorption
101. Solute Diuresis
• = osmotic diuresis
• large amounts of a poorly reabsorbed solute
such as glucose, mannitol, or urea
102. Osmotic Diuresis
Normal Person
Water restricted
Normal person Mannitol Infusion
Water Restricted
Urine Flow Low
Uosm 1200
Urine Flow High
Uosm 400
H20
H20
H20
H20
H20
H20
Cortex
Medulla
M
Na
Na
Na
Na
Na
M M M
M
M
M
M
M
M
Na
104. 2. Glomerulotubular Balance
Concept: The constant fraction (about 65% - 70%) of the
filtered Na+ and water are reabsorbed in the proximal tubular,
despite variation of GFR.
Importance: To prevent overloading of the distal tubular
segments when GFR increases.
Glomerulotubular balance acts as a second line of defense to
buffer the effect of spontaneous changes in GFR on urine
output.
(The first line of defense discussed above includes the renal
autoregulatory mechanism, especially tubuloglomerular
feedback, that help to prevent changes)
105. Glomerulotubular balance:
Mechanisms
GFR increase independent of the GPF -- The peritubular
capillary colloid osmotic pressure increase and the
hydrostatic pressure decrease – The reabsorption of water in
proximal tubule increase
107. INNERVATION OF THE KIDNEY
Nerves from the renal plexus (sympathetic nerve)
of the autonomic nervous system enter kidney at
the hilusinnervate smooth muscle of afferent &
efferent arteriolesregulates blood pressure &
distribution throughout kidney
Effect: (1) Reduce the GPF and GFR and through
contracting the afferent and efferent artery (α
receptor)
(2) Increase the Na+ reabsorption in the proximal
tubules (β receptor)
(3) Increase the release of renin (β receptor)
108. Nerve reflex:
1. Cardiopulmonary reflex and Baroreceptor Reflex
2. Renorenal reflex
Sensory nerves located in the renal pelvic wall are
activated by stretch of the renal pelvic wall, which may
occur during diuresis or ureteral spasm/occlusion.
Activation of these nerves leads to an increase in
afferent renal nerve activity, which causes a decrease in
efferent renal nerve activity and an increase in urine flow
rate and urinary sodium excretion.
This is called a renorenal reflex response.
109. The series of mechanisms leading to activation of renal
mechanosensory nerves include:
Increased renal pelvic pressure increases the release of
bradykinin which activates protein kinase C which in turn
results in renal pelvic release of PGE2 via activation of
COX-2.
PGE2 increases the release of substance P via
activation of N-type calcium channels in the renal pelvic
wall.
111. • Retention of Water is controlled by ADH:
– Anti Diuretic Hormone
–ADH Release Is Controlled By:
• Decrease in Blood Volume
• Decrease in Blood Pressure
• Increase in extracellular fluid (ECF)
Osmolarity
113. 2. Aldosterone
• Sodium Balance Is Controlled By Aldosterone
– Aldosterone:
• Steroid hormone
• Synthesized in Adrenal Cortex
• Causes reabsorbtion of Na+ in DCT & CD
–Also, K+ secretion
114. • Effect of Aldeosterone:
The primary site of aldosterone action is on the
principal cells of the cortical collecting duct.
The net effect of aldosterone is to make the kidneys
retain Na+ and water reabsorption and K+ secretion.
The mechanism is by stimulating the Na+ - K+ ATPase
pump on the basolateral side of the cortical
collecting tubule membrane.
Aldosterone also increases the Na+ permeability of the
luminal side of the membrane.
115.
116. Rennin-Angiotensin-Aldosterone System
Fall in NaCl, extracellular fluid volume, arterial blood pressure
Juxtaglomerular
Apparatus
Renin
Liver
Angiotensinogen
+
Angiotensin I Angiotensin II Aldosterone
Lungs
Converting
Enzyme
Adrenal
Cortex
Increased
Sodium
Reabsorption
Helps
Correct
Angioten
sinase A
Angiotension III
117. Regulation of the Renin Secretion:
Renal Mechanism:
1) Tension of the afferent artery (stretch receptor)
2) Macula densa (content of the Na+ ion in the distal
convoluted tubuyle)
Nervous Mechanism:
Sympathetic nerve
Humoral Mechanism:
E, NE, PGE2, PGI2
118. 3. Atrial natriuretic peptide(ANP)
• ANP is released by atrium in response to atrial
stretching due to increased blood volume
• ANP inhibits Na+ and water reabsorption, also
inhibits ADH secretion
• Thus promotes increased sodium excretion
(natriuresis) and water excretion (diuresis) in urine
120. IV Micturition
Once urine enters the renal pelvis, it flows through the ureters and enters
the bladder, where urine is stored.
Micturition is the process of emptying the urinary bladder.
Two processes are involved:
(1) The bladder fills progressively until the tension in its wall reses
above a threshold level, and then
(2) A nervous reflex called the micturition reflex occurs that empties the
bladder.
The micturition reflex is an automatic spinal cord reflex; however, it can
be inhibited or facilitated by centers in the brainstem and cerebral
cortex.
122. •1) APs generated by stretch receptors
•2) reflex arc generates APs that
•3) stimulate smooth muscle lining bladder
•4) relax internal urethral sphincter (IUS)
•5) stretch receptors also send APs to Pons
•6) if it is o.k. to urinate
–APs from Pons excite smooth muscle of bladder and relax
IUS
–relax external urethral sphincter
•7) if not o.k.
–APs from Pons keep
EUS contracted
stretch
receptors
123. • Decline in the number of functional nephrons
• Reduction of GFR
• Reduced sensitivity to ADH
• Problems with the micturition reflex
Changes with aging include: