Renal Physiology I ( Lecture 50 - 53 )

Question 1

What is the balance concept

Answer 1

input = output

Question 2

What are the 5 functions of the kidney

Answer 2

1. Regulation of water, inorganic ions balance, and acid base balance
2. Removal of metabolic waste product from the blood and excretion in the urine
3. Removal of foreign chemical from the blood and their excretion in the urine
4. Gluconeogenesis
5. Production of hormones / enzymes

Question 3

Explain the first 3 functions of the kidney

Answer 3

1. 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
2. Metabolic waste includes urea from protein, uric acid from nucleotides, and end products of hemoglobin breakdown
3. Examples of foreign chemical substance include saccharin and benzoate

Question 4

Explain Gluconegenesis

Answer 4

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.

Question 5

Explain the production of hormones and enzymes

Answer 5

1. Erythropoietin – this controls the erythrocyte production which is related to RBC production in the bone marrow
2. Renin – an enzymes that controls the formation of angiotensin which can influence blood pressure and sodium balance
3. 1,25- dihydroxyvitamin D, which is made in the kidneys can influence calcium production

Question 6

(T/F) kidneys can only process blood by removing substances

Answer 6

False

A lot of times kidneys remove substance, however, in a few cases, there can also be adding of substance

Question 7

The ____ are the site of urine formation

Answer 7

kidneys

Question 8

The kidneys are paired organs that like outside the ______ cavity in the ______. One one each side of the ______.

Answer 8

abdominal (peritoneal)
posterior abdominal wall
vertebral column

Question 9

What is the function or ureters

Answer 9

Carry urine from kidneys to bladder

Question 10

function of bladder

Answer 10

stores urine until voided from body

Question 11

function of urethra

Answer 11

carries urine from bladder to outside of the body

Question 12

2 major regions revealed from bisection of a kidney

Answer 12

inner renal medula

outer renal cortex

Question 13

Kidneys receive ______ of cardiac output. This shows that one of the traits critical to renal function is _____.

Answer 13

20-25%

high rate of blood flow

Question 14

Blood flow in the kidney is supplied by the _____ and _____. Function ?

Answer 14

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

Question 15

What are nephrons

Answer 15

Nephrons are located at the renal cortex and is the basic structural and function unit of the kidney that acts to filter blood.

Question 16

What are the 2 types of nephrons in the kidney

Answer 16

cortical nephrons and juxtamedullary nephrons

Question 17

compare and contrast the 2 types of nephrons in the kidney

Answer 17

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.

Question 18

The _____ is the site of ultrafiltration.

Answer 18

outer renal cortex

Question 19

Each kidney has about _____ nephrons

Answer 19

1 million

Question 20

(T/F) Both types of nephrons help maintain osmotic gradient

Answer 20

False
Although both types of nephrons produce urine. Only the juxtamedullary nephrons helps maintain osmotic gradient which is essential for urine production.

Question 21

What is the renal corpuscle

Answer 21

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

Question 22

The renal corpuscle consists of what two compartments.

What are their functions ?

Answer 22

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

Question 23

Explain the 3 layers of filtration barrier within the renal corpuscle

Answer 23

1. There is the capillary endothelium of the glomerular capillaries. It has large holes / windows called fenestrae.
2. Above that, there is the basement membrane that is a gel-liked acellular meshwork filled with glycoproteins and proteoglycans.
3. 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.

Question 24

Explain the process from the bowman’s capsule to the renal pelvis

Answer 24

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.

Question 25

Each nephron has ____ arteriole(s) and ____ sets of capillaries

Answer 25

2 arterioles and 2 sets of capillaries.

Question 26

Explain the blood flow including keywords arteriole ``` efferent arteriole peritubular capillaries veins afferent arterioles glomerular capillaries ```

Answer 26

1. Blood enters the glomerular capillaries from the afferent arterioles. 2. They combine to another set of arterioles called the efferent arterioles. 3. The efferent arterioles of the CORTICAL nephron subdivides into peritubular capillaries which is profusely distributed in the tubules. 4. The peritubular capillaries then rejoin to form veins that leave the kidneys.

Question 27

What are the peritubular capillaries

Answer 27

The peritubular capillaries are "divided" capillaries that branch from the efferent arterioles. They are distributed within the tubules and join together to form veins.

Question 28

The arrangement of the blood vessels in the nephron allows fluid to be filtered out of the blood at _______ and ________ at the ________.

Answer 28

glomerular capillaries reabsorbed peritubular capillaries

Question 29

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 ______.

Answer 29

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

Question 30

What gives rise to the looping vasa recta

Answer 30

efferent arterioles of the juxtamedullary nephrons

Question 31

What is the vasa recta and its significance

Answer 31

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.

Question 32

What is fenestrae

Answer 32

These are the "windows" located at the capillary endothelium.

Question 33

(T/F) Structure of the epithelial cells of renal tubules vary.

Answer 33

True. | Structures may vary segment to segment but all have tight junctions between adjacent cells

Question 34

From the renal pelvis, what happens to urine

Answer 34

Urine flows from the ureters to the bladder.

Question 35

Name the sequence form Bowman's capsule to renal pelvis (6)

Answer 35

``` Bowman's capsule proximal tubule loop of henle distal tubule collecting duct renal pelvis ```

Question 36

The urinary excretion of a substance depends on its ____, ____, and _____ Explain

Answer 36

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)

Question 37

Glomerular filtration is a ______ (active / passive) process in which ________ force the fluids and solutes through the membrane

Answer 37

passive | hydrostatic

Question 38

Why are the glomeruli in the kidney a more efficient filter that other capillary beds

Answer 38

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.

Question 39

Filtration across the glomerular capillaries is determined by _______.

Answer 39

opposing Starling forces

Question 40

Starling forces that favor glomerular filtration are

Answer 40

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

Question 41

Starling forces that oppose filtration at the glomerulus are

Answer 41

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

Question 42

The net glomerular filtration pressure is __

Answer 42

16 mm Hg

Question 43

(T/F) Glomerular filtration rate (GFR) can not be changed

Answer 43

False | It is subject to physiological change and can be changed through hormones and and neural input

Question 44

Constriction of efferent arterioles causes ______ | Name location/ change in pressure / and change in GFR

Answer 44

increase in hydrostatic pressure in the glomerular capillaries This causes an increase in GFR

Question 45

Constriction of afferent arterioles causes _____ | Name location/ change in pressure / and change in GFR

Answer 45

decrease in hydrostatic pressure in the glomerular capillaries A decrease in GFR

Question 46

Filtered quantities of a substance are usually ______ amounts of substance in the body. ex?

Answer 46

larger | body contains 40 L of water but filters 180 L of water

Question 47

Reabsorption of waste product, such as _____, is relatively ____, so that ______

Answer 47

urea incomplete excreted to the urine

Question 48

Reabsorption of most useful plasma components are relatively _______. Ex?

Answer 48

complete | water and glucose

Question 49

Reabsorbed substances have to pass through ____ (#) barriers, which are ___

Answer 49

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

Question 50

(T/F) Transport for reabsorption can only be active

Answer 50

false | it can be both active and passive ( with or without ATP )

Question 51

What is tubular secretion important for

Answer 51

1. disposing of drugs and drug metabolites 2. eliminating undesired process 3. remove excess K+ 4. controlling blood pH

Question 52

Under normal conditions losses of salt and water ______. This is the result of _______

Answer 52

equals gains | This is the result of urinary loss regulation

Question 53

2 generalizations of NA and water reabsorption

Answer 53

1. Na reabsorption is an active process that occurs in all tubular segments except the descending limb of the Loop of Henle. 2. Water reabsorption is by osmosis and is dependent upon Na+ reabsorption

Question 54

(T/F) Na+ reabsorption is a passive process

Answer 54

FALSE | it is an active process

Question 55

(T/F) Water reabsorption by osmosis is independent

Answer 55

False | it is dependent upon Na+ reabsorption

Question 56

Na+ is ______ transported across the ______ of the ________ establishing an osmotic gradient for water reabsorption Explain

Answer 56

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

Question 57

Explain the cellular mechanisms of water and urea reabsorption

Answer 57

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

Question 58

Water permeability varies from tubular segments which depends on _______

Answer 58

Aquaporins (water channels)

Question 59

AQP are highly expressed in the ______ of the ______ , which results in _________ (sth to do with permeability) This results in ...

Answer 59

proximal tubule of the nephron high water permeability This results in water to be reabsorbed almost as rapidly as Na+

Question 60

Which tubular segments have water permeability under physiological control

Answer 60

cortical and medulla collecting ducts

Question 61

Peptide hormone ______ or (...) is released from the ______ and stimulates the insertion of _______ into the membranes of the renal tubular cells in a ______ manner.

Answer 61

Vasopressin (ADH) posterior pituitary gland Aquaporin (AQP2) water channels PKA-dependent

Question 62

AQP2 is absent in the _______ unless ______ is active

Answer 62

collecting duct | Vasopressin

Question 63

Which segment does Na reabsorption not occur in

Answer 63

descending limb of the loop of Henle

Question 64

A large volume of dilute urine is produced when

Answer 64

plasma vasopressin is concentration is low which hence causes water reabsorption by the collecting ducts to be low.