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.
Each kidney contains over 1 million tiny structures called nephrons. Each nephron has a glomerulus, the site of blood filtration. The glomerulus is a network of capillaries surrounded by a cuplike structure, the glomerular capsule (or Bowman’s capsule). As blood flows through the glomerulus, blood pressure pushes water and solutes from the capillaries into the capsule through a filtration membrane. This glomerular filtration begins the urine formation process.Inside the glomerulus, blood pressure pushes fluid from capillaries into the glomerular capsule through a specialized layer of cells. This layer, the filtration membrane, allows water and small solutes to pass but blocks blood cells and large proteins. Those components remain in the bloodstream. The filtrate (the fluid that has passed through the membrane) flows from the glomerular capsule further into the nephron.The glomerulus filters water and small solutes out of the bloodstream. The resulting filtrate contains waste, but also other substances the body needs: essential ions, glucose, amino acids, and smaller proteins. When the filtrate exits the glomerulus, it flows into a duct in the nephron called the renal tubule. As it moves, the needed substances and some water are reabsorbed through the tube wall into adjacent capillaries. This reabsorption of vital nutrients from the filtrate is the second step in urine creation.The filtrate absorbed in the glomerulus flows through the renal tubule, where nutrients and water are reabsorbed into capillaries. At the same time, waste ions and hydrogen ions pass from the capillaries into the renal tubule. This process is called secretion. The secreted ions combine with the remaining filtrate and become urine. The urine flows out of the nephron tubule into a collecting duct. It passes out of the kidney through the renal pelvis, into the ureter, and down to the bladder.The nephrons of the kidneys process blood and create urine through a process of filtration, reabsorption, and secretion. Urine is about 95% water and 5% waste products. Nitrogenous wastes excreted in urine include urea, creatinine, ammonia, and uric acid. Ions such as sodium, potassium, hydrogen, and calcium are also excreted
Each kidney contains over 1 million tiny structures called nephrons. Each nephron has a glomerulus, the site of blood filtration. The glomerulus is a network of capillaries surrounded by a cuplike structure, the glomerular capsule (or Bowman’s capsule). As blood flows through the glomerulus, blood pressure pushes water and solutes from the capillaries into the capsule through a filtration membrane. This glomerular filtration begins the urine formation process.Inside the glomerulus, blood pressure pushes fluid from capillaries into the glomerular capsule through a specialized layer of cells. This layer, the filtration membrane, allows water and small solutes to pass but blocks blood cells and large proteins. Those components remain in the bloodstream. The filtrate (the fluid that has passed through the membrane) flows from the glomerular capsule further into the nephron.The glomerulus filters water and small solutes out of the bloodstream. The resulting filtrate contains waste, but also other substances the body needs: essential ions, glucose, amino acids, and smaller proteins. When the filtrate exits the glomerulus, it flows into a duct in the nephron called the renal tubule. As it moves, the needed substances and some water are reabsorbed through the tube wall into adjacent capillaries. This reabsorption of vital nutrients from the filtrate is the second step in urine creation.The filtrate absorbed in the glomerulus flows through the renal tubule, where nutrients and water are reabsorbed into capillaries. At the same time, waste ions and hydrogen ions pass from the capillaries into the renal tubule. This process is called secretion. The secreted ions combine with the remaining filtrate and become urine. The urine flows out of the nephron tubule into a collecting duct. It passes out of the kidney through the renal pelvis, into the ureter, and down to the bladder.The nephrons of the kidneys process blood and create urine through a process of filtration, reabsorption, and secretion. Urine is about 95% water and 5% waste products. Nitrogenous wastes excreted in urine include urea, creatinine, ammonia, and uric acid. Ions such as sodium, potassium, hydrogen, and calcium are also excreted
Juxtaglomerular apparatus (The Guyton and Hall physiology)Maryam Fida
JUXTAGLOMERULAR APPARATUS
Juxtaglomerular apparatus is a specialized organ situated near the glomerulus of each nephron (juxta = near).
1..MACULA DENSA
Macula densa is the end portion of thick ascending segment. It is situated between afferent and efferent arterioles of the same nephron. It is very close to afferent arteriole.
Macula densa is formed by tightly packed cuboidal epithelial cells.
2..EXTRAGLOMERULAR MESANGIAL CELLS
Extraglomerular mesangial cells are situated in the triangular region bound by afferent arteriole, efferent arteriole and macula densa. These cells are also called agranular cells, lacis cells or Goormaghtigh cells.
3. Glomerular Mesangial Cell
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.
The nephron is the microscopic structural and functional unit of the kidney. It is composed of a renal corpuscle and a renal tubule. The renal corpuscle consists of a tuft of capillaries called a glomerulus and an encompassing Bowman's capsule. The renal tubule extends from the capsule.
Juxtaglomerular apparatus (The Guyton and Hall physiology)Maryam Fida
JUXTAGLOMERULAR APPARATUS
Juxtaglomerular apparatus is a specialized organ situated near the glomerulus of each nephron (juxta = near).
1..MACULA DENSA
Macula densa is the end portion of thick ascending segment. It is situated between afferent and efferent arterioles of the same nephron. It is very close to afferent arteriole.
Macula densa is formed by tightly packed cuboidal epithelial cells.
2..EXTRAGLOMERULAR MESANGIAL CELLS
Extraglomerular mesangial cells are situated in the triangular region bound by afferent arteriole, efferent arteriole and macula densa. These cells are also called agranular cells, lacis cells or Goormaghtigh cells.
3. Glomerular Mesangial Cell
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.
The nephron is the microscopic structural and functional unit of the kidney. It is composed of a renal corpuscle and a renal tubule. The renal corpuscle consists of a tuft of capillaries called a glomerulus and an encompassing Bowman's capsule. The renal tubule extends from the capsule.
The main function of the kidney is excretion of water soluble waste products from our body.
Derangement of any of these function would result in either decreased excretion of waste products and hence their accumulation in the body or loss of some vital nutrient from the body.
Biotin (vitamin b7) biological functions, clinical indications and its techn...rohini sane
An illustrative presentation on Biotin (Vitamin B7), clinical indications and technological applications for Medical, Dental, Pharmacology & Biotechnology students to facilitate easy- learning.
An illustrative and lucid presentation on Scurvy (deficiency of vitamin C) for Medical, Dental, Pharmacology & Biotechnology students to facilitate easy- learning.
An illustrative presentation on Vitamin C (Ascorbic acid) and Scurvy for Medical, Dental, Pharmacology & Biotechnology students to facilitate easy- learning.
An illustrative presentation on Microscopic examination of Urine for Medical, Dental, Pharmacology and Biotechnology students to facilitate easy- learning and self-study..
Urinalysis for detection of abnormal constituentsrohini sane
An illustrative presentation on Urinalysis for detection of abnormal constituents for medical ,dental , pharmacology and biotechnology students to facilitate easy-learning.
Urinalysis for detection of normal inorganic and organic constituentsrohini sane
An illustrative presentation on urinalysis for detection of normal inorganic and organic constituents for medical, dental , pharmacology and biotechnology students to facilitate easy-learning.
Biochemical kidney function tests with their clinical applicationsrohini sane
An illustrative presentation on Biochemical kidney function tests with their clinical applications for medical ,dental, pharmacology and biotechnology student to facilitate easy-learning.
A comprehensive presentation on Total parenteral nutrition(TPN) to facilitate easy -learning for medical , dental , pharmacology and biotechnology students.
Nutritional management of clinical disordersrohini sane
A lucid presentation Nutritional management of clinical disorders to facilitate easy-learning for medical , dental , pharmacology and biotechnology students.
Nutritional importance of vitamins and mineralsrohini sane
A lucid presentation on Nutritional importance of vitamins and minerals for medical , dental , pharmacology and biotechnology students to facilitate easy-learning.
A lucid presentation on Basal metabolic rate ( BMR) and nutrition for medical ,dental ,pharmacology and biotechnology students to facilitate easy-learning.
Physical activity of the human body and nutritionrohini sane
A lucid presentation on Physical activity of the human body and Nutrition for medical ,dental ,pharmacology and biotechnology students for easy learning.
These simplified slides by Dr. Sidra Arshad present an overview of the non-respiratory functions of the respiratory tract.
Learning objectives:
1. Enlist the non-respiratory functions of the respiratory tract
2. Briefly explain how these functions are carried out
3. Discuss the significance of dead space
4. Differentiate between minute ventilation and alveolar ventilation
5. Describe the cough and sneeze reflexes
Study Resources:
1. Chapter 39, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 34, Ganong’s Review of Medical Physiology, 26th edition
3. Chapter 17, Human Physiology by Lauralee Sherwood, 9th edition
4. Non-respiratory functions of the lungs https://academic.oup.com/bjaed/article/13/3/98/278874
- Video recording of this lecture in English language: https://youtu.be/lK81BzxMqdo
- Video recording of this lecture in Arabic language: https://youtu.be/Ve4P0COk9OI
- Link to download the book free: https://nephrotube.blogspot.com/p/nephrotube-nephrology-books.html
- Link to NephroTube website: www.NephroTube.com
- Link to NephroTube social media accounts: https://nephrotube.blogspot.com/p/join-nephrotube-on-social-media.html
Ozempic: Preoperative Management of Patients on GLP-1 Receptor Agonists Saeid Safari
Preoperative Management of Patients on GLP-1 Receptor Agonists like Ozempic and Semiglutide
ASA GUIDELINE
NYSORA Guideline
2 Case Reports of Gastric Ultrasound
Prix Galien International 2024 Forum ProgramLevi Shapiro
June 20, 2024, Prix Galien International and Jerusalem Ethics Forum in ROME. Detailed agenda including panels:
- ADVANCES IN CARDIOLOGY: A NEW PARADIGM IS COMING
- WOMEN’S HEALTH: FERTILITY PRESERVATION
- WHAT’S NEW IN THE TREATMENT OF INFECTIOUS,
ONCOLOGICAL AND INFLAMMATORY SKIN DISEASES?
- ARTIFICIAL INTELLIGENCE AND ETHICS
- GENE THERAPY
- BEYOND BORDERS: GLOBAL INITIATIVES FOR DEMOCRATIZING LIFE SCIENCE TECHNOLOGIES AND PROMOTING ACCESS TO HEALTHCARE
- ETHICAL CHALLENGES IN LIFE SCIENCES
- Prix Galien International Awards Ceremony
Explore natural remedies for syphilis treatment in Singapore. Discover alternative therapies, herbal remedies, and lifestyle changes that may complement conventional treatments. Learn about holistic approaches to managing syphilis symptoms and supporting overall health.
Ethanol (CH3CH2OH), or beverage alcohol, is a two-carbon alcohol
that is rapidly distributed in the body and brain. Ethanol alters many
neurochemical systems and has rewarding and addictive properties. It
is the oldest recreational drug and likely contributes to more morbidity,
mortality, and public health costs than all illicit drugs combined. The
5th edition of the Diagnostic and Statistical Manual of Mental Disorders
(DSM-5) integrates alcohol abuse and alcohol dependence into a single
disorder called alcohol use disorder (AUD), with mild, moderate,
and severe subclassifications (American Psychiatric Association, 2013).
In the DSM-5, all types of substance abuse and dependence have been
combined into a single substance use disorder (SUD) on a continuum
from mild to severe. A diagnosis of AUD requires that at least two of
the 11 DSM-5 behaviors be present within a 12-month period (mild
AUD: 2–3 criteria; moderate AUD: 4–5 criteria; severe AUD: 6–11 criteria).
The four main behavioral effects of AUD are impaired control over
drinking, negative social consequences, risky use, and altered physiological
effects (tolerance, withdrawal). This chapter presents an overview
of the prevalence and harmful consequences of AUD in the U.S.,
the systemic nature of the disease, neurocircuitry and stages of AUD,
comorbidities, fetal alcohol spectrum disorders, genetic risk factors, and
pharmacotherapies for AUD.
HOT NEW PRODUCT! BIG SALES FAST SHIPPING NOW FROM CHINA!! EU KU DB BK substit...GL Anaacs
Contact us if you are interested:
Email / Skype : kefaya1771@gmail.com
Threema: PXHY5PDH
New BATCH Ku !!! MUCH IN DEMAND FAST SALE EVERY BATCH HAPPY GOOD EFFECT BIG BATCH !
Contact me on Threema or skype to start big business!!
Hot-sale products:
NEW HOT EUTYLONE WHITE CRYSTAL!!
5cl-adba precursor (semi finished )
5cl-adba raw materials
ADBB precursor (semi finished )
ADBB raw materials
APVP powder
5fadb/4f-adb
Jwh018 / Jwh210
Eutylone crystal
Protonitazene (hydrochloride) CAS: 119276-01-6
Flubrotizolam CAS: 57801-95-3
Metonitazene CAS: 14680-51-4
Payment terms: Western Union,MoneyGram,Bitcoin or USDT.
Deliver Time: Usually 7-15days
Shipping method: FedEx, TNT, DHL,UPS etc.Our deliveries are 100% safe, fast, reliable and discreet.
Samples will be sent for your evaluation!If you are interested in, please contact me, let's talk details.
We specializes in exporting high quality Research chemical, medical intermediate, Pharmaceutical chemicals and so on. Products are exported to USA, Canada, France, Korea, Japan,Russia, Southeast Asia and other countries.
Tom Selleck Health: A Comprehensive Look at the Iconic Actor’s Wellness Journeygreendigital
Tom Selleck, an enduring figure in Hollywood. has captivated audiences for decades with his rugged charm, iconic moustache. and memorable roles in television and film. From his breakout role as Thomas Magnum in Magnum P.I. to his current portrayal of Frank Reagan in Blue Bloods. Selleck's career has spanned over 50 years. But beyond his professional achievements. fans have often been curious about Tom Selleck Health. especially as he has aged in the public eye.
Follow us on: Pinterest
Introduction
Many have been interested in Tom Selleck health. not only because of his enduring presence on screen but also because of the challenges. and lifestyle choices he has faced and made over the years. This article delves into the various aspects of Tom Selleck health. exploring his fitness regimen, diet, mental health. and the challenges he has encountered as he ages. We'll look at how he maintains his well-being. the health issues he has faced, and his approach to ageing .
Early Life and Career
Childhood and Athletic Beginnings
Tom Selleck was born on January 29, 1945, in Detroit, Michigan, and grew up in Sherman Oaks, California. From an early age, he was involved in sports, particularly basketball. which played a significant role in his physical development. His athletic pursuits continued into college. where he attended the University of Southern California (USC) on a basketball scholarship. This early involvement in sports laid a strong foundation for his physical health and disciplined lifestyle.
Transition to Acting
Selleck's transition from an athlete to an actor came with its physical demands. His first significant role in "Magnum P.I." required him to perform various stunts and maintain a fit appearance. This role, which he played from 1980 to 1988. necessitated a rigorous fitness routine to meet the show's demands. setting the stage for his long-term commitment to health and wellness.
Fitness Regimen
Workout Routine
Tom Selleck health and fitness regimen has evolved. adapting to his changing roles and age. During his "Magnum, P.I." days. Selleck's workouts were intense and focused on building and maintaining muscle mass. His routine included weightlifting, cardiovascular exercises. and specific training for the stunts he performed on the show.
Selleck adjusted his fitness routine as he aged to suit his body's needs. Today, his workouts focus on maintaining flexibility, strength, and cardiovascular health. He incorporates low-impact exercises such as swimming, walking, and light weightlifting. This balanced approach helps him stay fit without putting undue strain on his joints and muscles.
Importance of Flexibility and Mobility
In recent years, Selleck has emphasized the importance of flexibility and mobility in his fitness regimen. Understanding the natural decline in muscle mass and joint flexibility with age. he includes stretching and yoga in his routine. These practices help prevent injuries, improve posture, and maintain mobilit
2. Nephron as the functional unit of kidney
• Nephron is the functional unit of the kidney.
• Each Kidney is composed of approximately one million nephrons.
• Nephron is made of a renal capsule and renal tubule.
• The renal capsule contains a thin walled sac-like structure called the Bowman's
capsule into which the afferent arterioles from renal artery form a capillary
network called glomerulus.
• Each renal tubule consists of Proximal convoluted tubule (PCT) which dips into
the renal medulla to form the Loop of Henle. The tubule reenters the renal
cortex to form the Distal convoluted tubule (DCT). Several DCTs merge to form
a Collecting duct.
• Several Collecting tubules join and open into renal pelvis . The juxtaglomerular
apparatus present between the DCT and afferent arterioles secretes renin.
3. Diagrammatic representation of Nephron
The glomerulus has a semipermeable membrane through which substances (except cells
and large molecular size plasma proteins) are filtered into Bowman ‘s capsule at a rate
( 120ml/minute).This is known as Glomerular filtration rate(GFR).
4. Functions of components of Nephron of kidney
❖Proximalconvolutedtubules(PCT):80%saltandwaterareabsorbedfromglomerular
filtrateinproximalconvolutedtubule.Allfilteredglucoseandaminoacidsarereabsorbedin
here.Lowmolecularweightproteins,urea,potassium,magnesiumandcalciumare
reabsorbedtovaryingextent.
❖LoopofHenle:
▪ ThedescendingloopofHenleishighlypermeabletowater.Passivereabsorptionofwater
occursleavinghighlyconcentratedurineatthebottomofloop.
▪ TheascendingloopofHenle(dilutingsegment)isrelativelyimpermeabletopassageof
waterbutactivelyabsorbsNa+andCl- ions.
❖Distalconvolutedtubule(DCT):asmallfractionoffilteredsodium,chlorideandwateris
reabsorbedinDCT, whichrespondstoADH,sothatitswaterpermeabilityishighinthe
presenceofhormoneandlowinitsabsence.
❖Collectingtubule:ADHcontrolsthewaterpermeabilityofthecollectingtubulethroughout
itslength.
6. Functions of kidney
❖Functions of kidney :
1. Excretion of metabolite waste products : the end products of protein and nucleic acid
metabolism and metabolites of xenobiotics are eliminated from the body. (effect on
blood pressure and heart) e.g. urea, creatinine, creatine , uric acid , sulphate and
phosphates
2. Maintain fluid and electrolyte homoeostasis :the kidney is largely responsible for the
regulation of water, electrolyte ,acid -base balance(maintenance of pH) in the body e.g.
glucose , amino acids etc.
3. Endocrine Function: The kidneys also function as Endocrine organs by producing
hormones:
a) Renin
b) Erythropoietin (effect on RBC synthesis)
c) 1,25 Dihydroxycholecalciferol= Calcitriol (activation of Vitamin D –effects on bones)
d) Prostaglandins (PGA 2 PGE 2 ,PGF 2 )
e) Bradykinin and Kallidin
4. Participates metabolism by retaining substances vital to body: The kidneys reabsorb and
retain several substances of biochemical importance in the body . e.g. Glucose ,amino acids .
8. The Formation of urine
• Three steps of formation of urine:
1. Glomerular filtration
2. Tubular reabsorption
3. Tubular secretion
9. Glomerular filtration: various ways
Complete
reabsorption
Partial reabsorption
by diffusion
No reabsorption and
no secretion
Secretion
Reference D.N. Baron
Schematic diagram
11. Endocrine Functions of the kidney
Renin: a proteolytic enzyme produced in the juxtaglomerular apparatus of the kidney . It
stimulates the formation of Angiotensin II which in turn leads to Aldosterone production.
Angiotensin II and Aldosterone are the hormones involved in the regulation of electrolyte
balance . Angiotensin II is a powerful vasoconstrictor, that increases blood pressure and
causes contraction of smooth muscles.
Erythropoietin : a peptide hormone stimulates erythropoiesis in bone marrow (hemoglobin
synthesis) .
1,25 Dihydroxycholecalciferol (Calcitriol ): 1-hydroxylation occurs in kidney to form the
biochemically active form of vitamin D (Calcitriol). It regulates calcium absorption from the
gut and homeostasis.
Prostaglandins (PGA 2 PGE 2 ,PGF 2 ): are produced by renal medulla induce relaxation of
smooth muscles, vasodilatation, decrease in renal pressure, increase in renal blood flow and
excretion of sodium.
Bradykinin and Kallidin: peptide hormones produced by the kidney. They are a powerful
vasodilators that influence reabsorption of sodium and water. Bradykinin stimulates synthesis
of renal Prostaglandins .Kinins also play a role in blood coagulation increase renal blood flow
and exhibit antihypertensive effect .
❖Kidney possess receptors for hormones parathyroid hormone and ADH.
❖Kidney possess sites of inactivation of hormones such as insulin ,glucagon.
14. Glomerular filtration
❖Glomerular filtration:
➢Glomerular filtration is Passive process that results in the formation of ultrafiltrate of
blood .This process occurs when blood is perfused through Bowman’s capsule .
➢Volume of blood passing through the kidneys = 1200ml/every minute(650ml plasma)
: the renal flow blood .
➢Glomerular filtration rate (GFR ): 120 -125 ml blood (one tenth)filtered by the
Glomerulus of kidneys every minute.
➢With normal Glomerular filtration rate (GFR)of 120 -125 ml/ minute , 175 -180 L of
the Glomerular filtrate is formed per day in an adult ,out of which only 1.5 L is
excreted as urine. Thus more than 99% of Glomerular filtrate is reabsorbed by the
kidneys.
➢All the (unbound) constituents of plasma ,with molecular weight less than 68000
Dalton are passed into filtrate . Therefore the Glomerular filtrate is almost similar in
composition to plasma . It is a protein free and cell free filtrate of whole blood but
contains essential metabolites such as glucose and amino acids as well as waste
products (urea , uric acid and creatinine). Albuminuria is considered as earliest
manifestation of kidney dysfunction.
15. Factors affecting Glomerular filtration
❖ Factors affecting Glomerular filtration:
A. Renal blood flow
B. Passage of macromolecules is based on their Shape ,charge and size of molecules
to be filtered : anionic derivatives ,globular molecules of molecular weight >
68000 Dalton are retained . The sieves of glomeruli are such that hemoglobin
(molecular weight 67000) is filtered and passed into urine , while albumin is
retained in the blood .Therefore ,the earliest manifestation of abnormal renal
function is appearance of albumin in urine.
C. Molecules less than 5KD such as glucose ,creatinine , urea and electrolytes are
freely filtered by glomeruli.
D. The low molecular weight proteins are freely filtered by glomeruli ,reabsorbed
and catabolized by renal tubular cells.
E. The normal urinary protein excretion < 150 mg /24 hr.(made up of mostly Tamm
horsefall glycoprotein) .
16. Tests for measuring Glomerular filtration
1. Creatinine clearance Test
2. Urea clearance Tests
17. Glomerular filtration rate (GFR )
❖A decease in the renal function is due to the loss of functional nephrons , rather
than a decease in the function of individual nephron .
❖Glomerular filtration rate (GFR) : provides the most useful index for the assessment
of the severity of renal damage.
❖Glomerular filtration rate (GFR) is the product of filtration rate in single nephron
and number of nephrons in both kidneys .
❖Factors affecting Glomerular filtration rate (GFR):
1. Age( kidney function decline with age e.g. at 70 yr. of age , GFR < 60 ml/min in 25%
elders)
2. Sex
3. body size
4. Protein intake
5. Pregnancy
❖Normal Glomerular filtration rate (GFR )= 120- 130ml/mt/1.73 M2
❖Substantial kidney damage occurs before GFR is deceased .
18. Conditions associated with decreased Glomerular filtration rate (GFR )
❖Decreased GFR observed in :
a. Blood pressure < 60 mm
b. Renal calculi*
c. Enlarged prostrate *
d. Old age
*causes for obstruction to the renal flow
20. Calculation of Estimated Glomerular filtration rate (eGFR )
Cockcroft–Gault equation for Estimated Glomerular filtration rate (eGFR ) :
Ccr = (140 –age in years) x weight in kg /72 x serum creatinine
( x 0.85 in female) assuming that they have 15 % less muscle mass.
❖Estimated Glomerular filtration rate (eGFR )in ml /min / 1.73 m2 : 186 x (serum
creatinine /88.4) – 1.154 x (age) – 0.203 x 0.742 (if female)
❖Estimated Glomerular filtration rate (using both equations) can be used for staging
patients with chronic kidney disease neither in healthy individuals nor in children
and obese . –Modification of Diet in Renal Disease –MDRD
• Estimated Glomerular filtration rate (eGFR ) eliminates the need for timed urine
collection.
• It allows a technique of estimating creatinine clearance and thereby GFR using
serum creatinine levels.
• Accuracy of serum creatinine estimation is a major deciding factor in both
equations.
26. Tubular functions of Kidney
❖When the glomerular filtrate is formed, it contains all the crystalloids of
plasma .
❖Tubular functions of Kidney include Reabsorption or Secretion of solutes and
Reabsorption of water from glomerular filtrate in the proximal convoluted
tubule(PCT).
❖All filtered glucose and amino acids are absorbed in PCT.
❖The descending loop of Henle is highly permeable to water .Passive
reabsorption of water occurs leaving highly concentrated urine at the bottom
of loop.
❖The ascending loop of Henle (diluting segment) is relatively impermeable to
passage of water but actively absorbs Na+ and Cl- ions.
❖Low molecular weight proteins ,urea ,potassium , magnesium and calcium are
reabsorbed to varying extent.
27. Biochemical Tests measuring tubular functions
1. Determination of specific gravity ,concentrating and diluting ability of
kidney
2. Determination of serum and urine osmolarity
3. Determination urine ammonia
4. Phenolsulphonaphthalein (PSP)Test
28. Renal Tubular reabsorption
❖Tubular reabsorption : is an active process.
• The renal Tubules(Proximal convoluted tubule-PCT, Distal convoluted tubule -
DCT , Collecting tubules) retain water and most of the soluble constituents of
Glomerular filtrate by reabsorption(active or passive process) .
• A small fraction of filtered sodium , chloride and water is reabsorbed in the
distal tubule which responds to antidiuretics hormone (ADH) ,so that its water
permeability is high in the presence of hormone and low in its absence.
• ADH controls the water permeability of the collecting tubule throughout its
length of collecting tubule.
• The excreted urine has an entirely different composition compared to
Glomerular filtrate from which it is derived .
29. Renal threshold substances
• Renal threshold substances : there are certain substances in the blood whose
excretion in urine is dependent on their blood concentration. Such substances
are referred as Renal threshold substances.
• At normal concentration in the blood , they are completely reabsorbed by
kidneys, with a result that their excretion in urine is almost negligible.
• But when the blood levels are elevated ,the tubular reabsorption capacity is
saturated ,so that excess will be excreted in urine.
• High threshold substances : they are reabsorbed efficiently by kidneys (e.g .
Glucose, Amino acids)
• Low threshold substances : they are not reabsorbed or reabsorbed slightly by
kidneys (e.g. Creatinine, Urea , Uric acid) .
30. Threshold value-Plasma levels of common substances excreted in urine
Substance Threshold value plasma levels
Glucose 180mg/dl
Lactate 60 mg/dl
Bicarbonate 28 mequ /L
Calcium 10mg/dl
The Renal Threshold of substance is the Plasma levels above which compound is excreted
in urine.
31. Role of proximal convoluted tubule (PCT) in Renal Tubular functions
Reabsorption in proximal convoluted tubule of
99 % water ( obligatory )
Uric acid (obligatory)
Sodium -Na ⁺ (85% reabsorption)
Chloride- Cl- (85% reabsorption)
Bicarbonates (85% reabsorption)
Potassium- K ⁺ (100% reabsorption)
Glucose (100% reabsorption)
Amino acids (100% reabsorption)
Urea/phosphates - PO ⁻⁴ / Calcium Ca 2+ : are partially absorbed
Secretion in proximal convoluted tubule of : H⁺ ,acids , bases, NH4⁺ , Diodrast, PAH
32. Role of loop of Henle in Tubular functions of kidney
Reabsorption of ions in loop of Henle include :
Sodium -Na ⁺
Chloride- Cl-
Calcium – Ca2+
Magnesium - Mg2+
33. Role of distal convoluted tubule (DCT) in Tubular functions
Reabsorption in distal convoluted tubule include:
water (facultative)
Sodium -Na ⁺
Chloride- Cl-
Secretion in proximal convoluted tubule of : H⁺ , Potassium- K ⁺ , NH4⁺ , Uric acid
34. Tubular reabsorption Function of kidney
❖Reabsorption of water:
• More than 99 % of water (187.5 liters/day) is reabsorbed by counter
current multiplication or counter current exchange .
• Reabsorption of water from distal convoluted tubule (DCT) and
collecting ducts is facilitated by the pituitary hormone ADH.
❖Reabsorption of sodium: by symport and antiport system.
❖Reabsorption of potassium: occurs in the proximal convoluted
tubule (PCT).
• Reabsorption of urates: occurs in the proximal convoluted tubule
(PCT) by both active and passive transport.
36. Renal Tubular reabsorption of water
• More than 99% of water entering in Renal Tubules is reabsorbed .
❖Reabsorption of water in the PCT :
1. About 80% of water is reabsorbed .
2. Water is reabsorbed by passive transport as a solvent for actively reabsorbed sodium,
chloride , bicarbonate ions and glucose (obligatory Reabsorption –water has to move
along with solutes to maintain osmalality).
3. Tubular filtrate is isosmotic with plasma.
❖Reabsorption of water in the descending limb :
1. Tubular filtrate is hyperosmotic with plasma.
2. Water without solute is lost . This is termed as counter current multiplication .
3. Counter current multiplication :
a. Functions in absence of antidiuretic hormone( ADH)
b. is an active process that creates high medullary osmality in the Renal medulla and
produces dilute urine .
❖Reabsorption of water in the ascending limb :
a. sodium chloride is lost without water .
b. Tubular filtrate is hypoosmotic with plasma.
37. Flow rates of Renal Tubular reabsorption of water
Water reaches Flow rate Osmolarity
Proximal convoluted tubules 125 ml /min sodium, chloride ,
bicarbonate ions and glucose
are absorbed. Water has to
move along with solutes to
maintain osmality-
obligatory Reabsorption
Loop of Henle 25 ml/min Sodium is reabsorbed, Water
reabsorption is less. Urine is
hypotonic.
Distal tubules 16 ml/min Water reabsorbed under
influence of ADH –facultative
reabsorption
Collecting tubules 1 ml/min Urine is hypertonic.
38. Countercurrentmechanismof RenalTubularreabsorptionofwater
❖Reabsorption of water in the DCT and the collecting duct :
1. Water without solute is reabsorbed along the gradient created by counter
current multiplication .
2. This is termed as counter current exchange .
3. Counter current exchange :
a. is facilitated by antidiuretic hormone(ADH). ADH secretion in turn, is
controlled by hypothalamic osmoreceptors. The osmolality of plasma is the
stimulus for modulating ADH secretion.
b. concentrates the urine.
39. Factors influencing ADH secretion
❖Factors influencing ADH secretion include :
• Osmotic pressure of the blood: Osmoreceptors in the hypothalamus that are
sensitive to changes in the Osmotic pressure of the blood influence the
synthesis and secretion of ADH.
• Blood volume: volume receptors in the carotid sinus and left atrium
influence ADH secretion.
• An increase in Osmotic pressure of the blood or decrease in blood volume
stimulates ADH secretion.
40. Osmoreceptors in the hypothalamus
Osmoreceptors in the hypothalamus that are sensitive to changes in the Osmotic pressure of
the blood influence the synthesis and secretion of ADH.
41. Renal Tubular reabsorption of sodium
• Tubular reabsorption of sodium occurs in Proximal convoluted tubule-PCT by two
types of cotransport systems.
❖Symport system :which involves cotransport of sodium along with other substances
such as glucose ,amino acids and phosphates .It is catalyzed by Na+ _ K + ATP ase
present in basolateral plasma membrane of the epithelial cells .
• This creates sodium gradient that accomplishes active transport of sodium out of
the cell while potassium enters the cell.
• There is passive transport of equivalent amount of chloride to maintain electrical
neutrality.
• The net effect is the reabsorption of sodium chloride along with glucose and amino
acids etc.
❖Antiport system : involve exchange of sodium (reabsorbed) for another cation such
as H + as in Na+ -H +. This also achieves a net reabsorption of bicarbonate. When
hydrogen ions are to be conserved ,sodium to potassium exchange occurs .
42. Symport system for Renal Tubular reabsorption of sodium
Symportsystem:whichinvolvescotransportofsodiumalongwithothersubstancessuchasglucose,amino
acidsandphosphates.Itis iscatalyzedbyNa+ –K+ ATPase presentinbasolateralplasmamembraneofthe
epithelialcells.
43. Renal Tubular reabsorption of Glucose
• Normally Glucose is reabsorbed completely .
• The maximum rate at which Glucose is reabsorbed , referred as the Tubular
maximum for glucose(TmG)= 350 mg/min.
• When blood Glucose exceeds renal threshold for Glucose which is 10mmols/L
or (180mg/dl) , glucose spills over into the urine (glycosuria) .
• Water is excreted as a solvent for glucose (osmotic diuresis).
44. Renal Tubular reabsorption of Calcium
❖Tubular reabsorption of Calcium :
• About 90% of Calcium is reabsorbed from the glomerular filtrate.
• Regulation of calcium balance is achieved at the distal convoluted tubule .
• Factors regulating calcium reabsorption: parathyroid hormone and vitamin D.
45. Renal Tubular reabsorption of Uric Acid
• Uric Acid is completely reabsorbed in Proximal convoluted tubule-PCT, by both
active and passive mediated process .
• There is an active secretion of Uric Acid in the tubules . About 85% of the
excreted Uric Acid is derived by tubular secretion.
• The drug ,probenecid is secreted by the tubules and competes with Uric Acid
for reabsorption . Since probenecid increases Uric Acid excretion ,it is
uricosuric.
46. Renal Tubular reabsorption of Urea
• Urea is freely filtered by the glomerulus ,but about the 40% is reabsorbed
actively by the tubules.
• Rate of reabsorption of Urea varies inversely with tubular flow and accounts for
the elevation of blood urea when renal function is low.
• Concentration of Urea in urine = 70x concentration of Urea in plasma
• Urea forms 80% of total urinary solutes .
• Urine is roughly a 2 % solution of Urea.
47. Renal Tubular reabsorption of Potassium
• 70% of potassium in glomerular filtrate is reabsorbed by Proximal convoluted
tubule-PCT.
• Net secretion of potassium at the distal tubules ,in exchange for sodium
reabsorption , under the effect of aldosterone.
• However when H + concertation is increased, H + ions are exchanged for
sodium instead of potassium.
48. Mechanism of action of diuretics :1
Diuretics Mechanism of action of diuretics Site of action
Mannitol Osmotic diuretics act by interfering with reabsorption
of solutes so that more water is obligatory excreted
along with the solutes .
PCT
Acetazolamide A carbonic anhydrase inhibitor-the dissociation of
H2CO3 to H2O and CO2 is inhibited →decreased
reabsorption of bicarbonate ,sodium and water .
PCT
Thiazide decreased reabsorption of sodium and more water is
excreted obligatorily .
DCT
Frusemide Inhibits reabsorption of chloride , sodium and water
(chances for potassium depletion) .
Ascending limp of
loop of Henle
Spironolactone
(K+ sparing )
Aldosterone antagonist DCT
51. Reabsorption ,secretion and excretion of substances by kidney
Parameter Reabsorption Secretion Excretion/relative
concentration
Creatinine Nil Nil GF = URINE
Uric acid 70 % by proximal
convoluted tubules
(PCT)
by distal convoluted
tubules( DCT)
GF URINE
Urea 40 % by PCT Nil GF > URINE
Sodium ( Na ⁺) Partial Nil GF > URINE
Glucose Complete Nil GF >> URINE
Amino acids Complete Nil GF >> URINE
52. Tubular maximum
• Tubular maximum (Tm): is used to indicate maximum capacity of kidneys to
absorb a particular substance .
• e.g. Tubular maximum for glucose (TmG) : 350 mg/min
53. Defects in Renal Tubular reabsorption
• Renal glycosuria in which glucose appears in urine despite of normal plasma
glucose levels .
• Vitamin D resistant rickets : in which phosphates reabsorption is defective .
• De Toni Fanconi syndrome: is associated with glycosuria, phosphaturia and
Renal Tubular acidosis.
• Renal Amino aciduria : as in Fanconi syndrome and cystinosis .
55. Tubular secretion in kidney
❖Tubular secretion in kidney :
❖substances actively secreted by renal tubular cells include:
a) Endogenous substances( e.g. hippuric acid ,bile salts ,urates)
b) Exogenous substances( e.g. diuretics , salicylates ,p- amino Hippurate,
penicillin )
❖ Creatinine : is secreted when plasma levels increase above normal levels .
❖Potassium : is secreted in the DCT in exchange for sodium reabsorbed.
❖Aldosterone favors sodium reabsorption and excretion of Potassium.
❖Primary aldosteronism (excessive Aldosterone) : there is excessive excretion
of Potassium and retention of sodium.
❖Addison’s disease (deficiency of Aldosterone) : sodium excreted and
Potassium retained in excess .
58. Tubular secretory mass in kidney
• Tubular secretory mass : mass of functioning Tubular mass can be assessed
by measuring the tubular maximum for PAH(Tm PAH).
Tm = UV/P X GFR
For PAH ,the Tm is 76 mg/minute.
59. Tubular Dysfunctions of Kidney
❖In Tubular Dysfunctions of Kidney:
1. Urine volume increases
2. Urine concentration decreases
3. Specific gravity decreases
4. Serum uric acid increases (uric acid excretion decreases)
5. Acidification of urine decreases
6. Amino aciduria present
7. Serum phosphate decreases
8. Urine dilution test abnormal