Renal Physiology I ( Lecture 50 - 53 ) Flashcards
What is the balance concept
input = output
What are the 5 functions of the kidney
- Regulation of water, inorganic ions balance, and acid base balance
- Removal of metabolic waste product from the blood and excretion in the urine
- Removal of foreign chemical from the blood and their excretion in the urine
- Gluconeogenesis
- Production of hormones / enzymes
Explain the first 3 functions of the kidney
- Regulation of water, inorganic ion balance, and acid base balance is the MAJOR renal function of the kidney. It is done through excreting water and inorganic electrolytes in amounts sufficient to reach homeostasis
- Metabolic waste includes urea from protein, uric acid from nucleotides, and end products of hemoglobin breakdown
- Examples of foreign chemical substance include saccharin and benzoate
Explain Gluconegenesis
The generation of glucose from AA and other precursors, which is then released into the blood. Most glucoeogenesis happens in the blood, however, during fasting kidneys can supple ~20% as much glucose as the liver.
Explain the production of hormones and enzymes
- Erythropoietin – this controls the erythrocyte production which is related to RBC production in the bone marrow
- Renin – an enzymes that controls the formation of angiotensin which can influence blood pressure and sodium balance
- 1,25- dihydroxyvitamin D, which is made in the kidneys can influence calcium production
(T/F) kidneys can only process blood by removing substances
False
A lot of times kidneys remove substance, however, in a few cases, there can also be adding of substance
The ____ are the site of urine formation
kidneys
The kidneys are paired organs that like outside the ______ cavity in the ______. One one each side of the ______.
abdominal (peritoneal)
posterior abdominal wall
vertebral column
What is the function or ureters
Carry urine from kidneys to bladder
function of bladder
stores urine until voided from body
function of urethra
carries urine from bladder to outside of the body
2 major regions revealed from bisection of a kidney
inner renal medula
outer renal cortex
Kidneys receive ______ of cardiac output. This shows that one of the traits critical to renal function is _____.
20-25%
high rate of blood flow
Blood flow in the kidney is supplied by the _____ and _____. Function ?
renal arteries and veins
Renal arteries branch off the abdominal aorta and supply blood to the kidnesy
Renal veins carry blood from the kidneys to the inferior vena cava
What are nephrons
Nephrons are located at the renal cortex and is the basic structural and function unit of the kidney that acts to filter blood.
What are the 2 types of nephrons in the kidney
cortical nephrons and juxtamedullary nephrons
compare and contrast the 2 types of nephrons in the kidney
Both cortical and juxtamedullary nephrons produce urine
Cortical nephrons contain 80 - 85% of nephrons. They have a short loop of henle
Juxtamedullary nephrons have a long loop of henle which extends to the medulla. Only about 15% of nephrons are in this category and they maintain an osmotic gradient that is required to produce concentrated urine.
The _____ is the site of ultrafiltration.
outer renal cortex
Each kidney has about _____ nephrons
1 million
(T/F) Both types of nephrons help maintain osmotic gradient
False
Although both types of nephrons produce urine. Only the juxtamedullary nephrons helps maintain osmotic gradient which is essential for urine production.
What is the renal corpuscle
The renal corpuscle is the site of initial filtration site responsible for urine formation.
The separation of a cell and protein-free filtrate from plasma
The renal corpuscle consists of what two compartments.
What are their functions ?
Glomerulus and bowman’s capsule
The glomerulus is the compact region of interconnected capillaries that act as a network of filtration
The bowman’s capsule is the outer area of the glomerulus that receives filtrate and inflows into the renal tubules. It is like a balloon, fluid-filled capsule
Explain the 3 layers of filtration barrier within the renal corpuscle
- There is the capillary endothelium of the glomerular capillaries. It has large holes / windows called fenestrae.
- Above that, there is the basement membrane that is a gel-liked acellular meshwork filled with glycoproteins and proteoglycans.
- Resting on the basement membrane is the capsular epithelial cells called podocytes. These podocytes extend foot process to the basement membrane and intertwine with them.
Filtration slits are present between foot adjacent foot processes which allows filtrates to travel through the bowman’s space once they are through the capillary endothelial cells and basement membrane.
Explain the process from the bowman’s capsule to the renal pelvis
Filtered fluid enters the proximal tubule from the bowman’s capsule into the loop of henle. Throughout the length, the tubule is made of a single layer of epithelial cells resting on the basement membrane.
The structural characteristics of the tubules vary from section to section but one common characteristic is the tight junctions from adjacent cells.
From the Bowman capsule, each nephron is separated from each other. This separation ends when it reaches the renal pelvis and merges.
Each nephron has ____ arteriole(s) and ____ sets of capillaries
2 arterioles and 2 sets of capillaries.
Explain the blood flow including keywords arteriole
efferent arteriole peritubular capillaries veins afferent arterioles glomerular capillaries
- Blood enters the glomerular capillaries from the afferent arterioles.
- They combine to another set of arterioles called the efferent arterioles.
- The efferent arterioles of the CORTICAL nephron subdivides into peritubular capillaries which is profusely distributed in the tubules.
- The peritubular capillaries then rejoin to form veins that leave the kidneys.
What are the peritubular capillaries
The peritubular capillaries are “divided” capillaries that branch from the efferent arterioles. They are distributed within the tubules and join together to form veins.
The arrangement of the blood vessels in the nephron allows fluid to be filtered out of the blood at _______ and ________ at the ________.
glomerular capillaries
reabsorbed
peritubular capillaries
The ______ are the only capillaries of the body that are the only capillaries in the body that are _______, which are the _______ .
This trait allows _______ pressure in the capillary bed to be very ______ and it ________ into the ______.
Most of the filtrate is ______ in the _____ and returns to the blood through the ______.
glomerular capillaries / fed and drained by an arteriole / afferent and efferent arterioles
blood pressure / high / forces fluid and solutes out of the blood into the Bowman’s capsule
reabsorbed // renal tubule cells/ peritubular capillaries
What gives rise to the looping vasa recta
efferent arterioles of the juxtamedullary nephrons
What is the vasa recta and its significance
They are the peritubular capillaries that dip into the medula and go back to the cortex which forms hairpin loops. This is significant as the hairpin structure is important for concentrated urine.
What is fenestrae
These are the “windows” located at the capillary endothelium.
(T/F) Structure of the epithelial cells of renal tubules vary.
True.
Structures may vary segment to segment but all have tight junctions between adjacent cells
From the renal pelvis, what happens to urine
Urine flows from the ureters to the bladder.
Name the sequence form Bowman’s capsule to renal pelvis (6)
Bowman's capsule proximal tubule loop of henle distal tubule collecting duct renal pelvis
The urinary excretion of a substance depends on its ____, ____, and _____
Explain
filtration/ reabsorption / secretion
A. Glomerular filtration : filtration from the glomerulus to the bowman’s capsule
B. Reabsorption: from the tubules to the interstitial fluid outside of the tubules and enter the peritubular capillaries
C. Secretion: From the peritubular capillaries to the renal tubules. Substances excreted to urine from body.
D. Excretion: From the tubules out of the body (urine)
Glomerular filtration is a ______ (active / passive) process in which ________ force the fluids and solutes through the membrane
passive
hydrostatic
Why are the glomeruli in the kidney a more efficient filter that other capillary beds
They have a larger surface area and are very permeable to water and solutes
There is a higher glomerular pressure (~ 55mm Hg) therefore produce 180L per day vs 3-4 L per day from other capillary beds. There are Starling forces of osmotic and hydrostatic across the glomerular capillary.
Filtration across the glomerular capillaries is determined by _______.
opposing Starling forces
Starling forces that favor glomerular filtration are
Glomerular capillary hydrostatic Pressure (PGC)
– it is higher due to the resistant of efferent arterioles
– 60 mm Hg
Bowman’s capsule oncotic pressure ( Pi BC)
– 00 mm Hg
– It is low due to the lack of protein in the filtrate
Starling forces that oppose filtration at the glomerulus are
Glomerular capillary oncotic pressure ( PI GC)
- 29 mm Hg
- It is higher that more capillary beds due to the plasma proteins in the smaller volume of plasma
Bowman’s capsule of hydrostatic pressure (P BC)
- 15 mm Hg
- it is relatively high compared to systemic capillaries doe the the large volume of filtrate in an closed space
The net glomerular filtration pressure is __
16 mm Hg
(T/F) Glomerular filtration rate (GFR) can not be changed
False
It is subject to physiological change and can be changed through hormones and and neural input
Constriction of efferent arterioles causes ______
Name location/ change in pressure / and change in GFR
increase in hydrostatic pressure in the glomerular capillaries
This causes an increase in GFR
Constriction of afferent arterioles causes _____
Name location/ change in pressure / and change in GFR
decrease in hydrostatic pressure in the glomerular capillaries
A decrease in GFR
Filtered quantities of a substance are usually ______ amounts of substance in the body. ex?
larger
body contains 40 L of water but filters 180 L of water
Reabsorption of waste product, such as _____, is relatively ____, so that ______
urea
incomplete
excreted to the urine
Reabsorption of most useful plasma components are relatively _______. Ex?
complete
water and glucose
Reabsorbed substances have to pass through ____ (#) barriers, which are ___
2
tubule epithelium and capillary endothelium
goes fro epithelial cell linings in the tubules and has to pass through tight junctions. At last needs to cross capillary endothelium
(T/F) Transport for reabsorption can only be active
false
it can be both active and passive ( with or without ATP )
What is tubular secretion important for
- disposing of drugs and drug metabolites
- eliminating undesired process
- remove excess K+
- controlling blood pH
Under normal conditions losses of salt and water ______. This is the result of _______
equals gains
This is the result of urinary loss regulation
2 generalizations of NA and water reabsorption
- Na reabsorption is an active process that occurs in all tubular segments except the descending limb of the Loop of Henle.
- Water reabsorption is by osmosis and is dependent upon Na+ reabsorption
(T/F) Na+ reabsorption is a passive process
FALSE
it is an active process
(T/F) Water reabsorption by osmosis is independent
False
it is dependent upon Na+ reabsorption
Na+ is ______ transported across the ______ of the ________ establishing an osmotic gradient for water reabsorption
Explain
actively
basolateral membrane
renal tubule cells
Active transport of Na out of the renal tubule epithelial cells keeps the intracellular Na+ concentration to be lower than the renal tubule fluid.
This forms a concentration gradient causing movement of the Na+ from the lumen of the renal tubule into the renal tubule epithelial cells
Explain the cellular mechanisms of water and urea reabsorption
The active reabsorption of Na+ and other solutes creates an osmotic gradient , which leads water to follow the solutes
The reabsorption of water creates a concentration gradient for permeating solutes such as urea to move from the tubular fluid into the plasma in the peritubular capillaries
Water permeability varies from tubular segments which depends on _______
Aquaporins (water channels)
AQP are highly expressed in the ______ of the ______ , which results in _________ (sth to do with permeability)
This results in …
proximal tubule of the nephron
high water permeability
This results in water to be reabsorbed almost as rapidly as Na+
Which tubular segments have water permeability under physiological control
cortical and medulla collecting ducts
Peptide hormone ______ or (…) is released from the ______ and stimulates the insertion of _______ into the membranes of the renal tubular cells in a ______ manner.
Vasopressin (ADH)
posterior pituitary gland
Aquaporin (AQP2) water channels
PKA-dependent
AQP2 is absent in the _______ unless ______ is active
collecting duct
Vasopressin
Which segment does Na reabsorption not occur in
descending limb of the loop of Henle
A large volume of dilute urine is produced when
plasma vasopressin is concentration is low which hence causes water reabsorption by the collecting ducts to be low.
