Lectures 11 & 12 - The Kidneys

Question 0

What is the relationship between ECF volume, Na and Cl concentrations and blood pressure?

Answer 0

When the concentration of sodium and chloride ions are high rhis leads to an increase in the ECF volume and therefore an increase in blood pressure

Question 1

What are the kidneys primarily responsible for?

Answer 1

Maintaining the stability of the extracellular fluid volume, electrolyte composition and osmolarity

Question 2

What 2 substances do the kidneys produce?

Answer 2

Erythropoeitin

Renin

Question 3

What does the renal pelvis do?

Answer 3

It collects urine after it has formed

Question 4

What is the basic structural and functional unit of the kidney?

Answer 4

The nephron

Question 5

What are the two types of nephron?

Answer 5

Corticol nephrons

Juxtamedullary nephron

Question 6

What is the difference between the corticol nephrons and the juxtamedullary nephrons?

Answer 6

The corticol nephrons barely penetrate the medulla the juxtamedullary nephrons penetrate the medulla deeply

Question 7

What are the two components of each nephron?

Answer 7

The vascular component

The tubular component

Question 8

What are the 5 components of the tubular system of the nephron?

Answer 8

The bowman's capsule
The proximal tubule
The loop of henle
The distal tubule
The collecting duct

Question 9

What is the bowman’s capsules function?

Answer 9

It is where the glomerular filtrate is collected

Question 10

What is the function of the proximal tubule?

Answer 10

It has uncontrolled sodium reabsorption accounting for 67% of sodium reabsorption. It also reabsorbs amino acids, urea and glucose. It also secretes K and H

Question 11

What is the function of the loop of henle?

Answer 11

It establishes an osmotic gradient in the renal medulla that is impotwnt to produce urine of different concentrations

Question 12

What is the function of the distal tubule and the collecting duct?

Answer 12

It has variable controlled reabsorption of sodium and water and secretion of potassium and hydrogen, thus controlling the concentration of urine.

Question 13

What is the function of the afferent arteriole in the kidney?

Answer 13

It carries blood to the glomerulus

Question 14

What is the function of the glomerulus?

Answer 14

Ir is a mesh of capillaries that filters a protein-free plasma into the tubular component

Question 15

What is the function of the efferent arteriole in the kidney?

Answer 15

It carried blood from the glomerulus

Question 16

What is the function of the peritubular capillaries in the kidney?

Answer 16

It supplies the renal and makes exchanges with the tubular component

Question 17

What is the juxtaglomerular apparatus?

Answer 17

It produces substances involved in the control of kidney function

Question 18

What are the four basic renal processes?

Answer 18

Glomerular filtration
Tubular reabsorption
Tubular secretion
Urine excretion

Question 19

What is glomerular filtration?

Answer 19

Non-discrimination filtration of a protein-plasma free plasma from the glomerulus into the bowman’s capsule

Question 20

What is tubular reabsorption?

Answer 20

Selective movement of filtered substances from the tubukar lumen inti the peritubular capillaries

Question 21

What is tubular secretion?

Answer 21

Selective movement of non-filtered substances from the peritubular capillaries into the tubular limen

Question 22

What is urine excretion?

Answer 22

Creation of the medulla vertical osmotic gradient anything not reabsorbed is secreted in the urine

Question 23

Describe glomerular filtration

Answer 23

This is the first step in urine filtration. The afferent arteriole carries blood to the capillaries of the glomerulus, the pressure then forces the plasma from the capillaries into the bowmans capsule during this process most of the proteins are removed, the filtered plasma then enters the proximal tubule.

Question 24

Why does pressure build in the glomerulus?

Answer 24

The afferent arteriole is larger than the efferent arteriole

Question 25

What is the glomerular filtration rate?

Answer 25

125ml/min

Question 26

To be reabsorbed a substance needs to cross

Answer 26

``` The luminal membrane The cytosol of the tubular cells The basolateral membrane of the tubular cells The interstitial fluids The capillary wall ```

Question 27

Where does active sodium reabsorption take place?

Answer 27

Throughout most of the tubule except the descending limb of the loop of henle. The majority of this takes place in the proximal tubule

Question 28

How is sodium reabsorbed?

Answer 28

A sodium potassium pump located on the basolateral membrane of the tubular cell creates a sodium gradient allowing sodium to flow down the concentration gradient through a channel into the tubular cell then, it is pumped into the interstitial fluid then it diffuses through the capillary wall.

Question 29

How is sodium reabsorption controlled?

Answer 29

It is subject to hormonal control and is inversely dependent on the amount of sodium in the body fluids.

Question 30

What are the two key components in the RAA system?

Answer 30

The juxtaglomerular apparatus | The granular cells

Question 31

What do granular cells do in the renin-angiotension- aldosterone system?

Answer 31

It secretes renin when there is a fall in blood pressure of concentration of sodium chloride

Question 32

Describe the process of the RAA system

Answer 32

Stimuli is detected by the juxtaglomerular apparatus, this could be low sodium chloride concentrwtion, decrease in ecf or decrease in blood pressure. In response renin is secreted by the kidneys, this leads to a production of angiotension in the blood. This causes aldosterone secretion by the adrenal cortex which causes sodium reabsorption by the kidneys which causes water reabsorption in the interstitial space. This corrects the original stimuli.

Question 33

What is the function of tubular secretion?

Answer 33

It is a supplemental mechanism that hastens elimination of these compounds from the body.

Question 34

What are the three things secreted into the tubules?

Answer 34

Hydrogen ions Potassium ions Organic ions

Question 35

What is the function of proton secretion into the tubules?

Answer 35

Regulation of the acid-base balance in the body

Question 36

What is the function of potassium ion secretion into the tubules?

Answer 36

It is attached to sodium reabsorption

Question 37

What is the function of organic secretion into the tubules?

Answer 37

Elimination of foreign compounds and blood borne chemical messengers

Question 38

What is the highest possible concentration of urine excreted from the human body?

Answer 38

1200mosm/l

Question 39

What is the most dilute urine concentration possible?

Answer 39

100msom/l

Question 40

What is responsible for urine concentration?

Answer 40

The vertical osmotic gradient in the renal medulla established by the loop of henle

Question 41

How is the medullary vertical osmotic gradient established?

Answer 41

The descending limb is highly permeable to water and the ascending limb is highly permeable to sodium and chloride ions.

Question 42

What is the purpose of countercurrent multiplication?

Answer 42

The fluid which enters the distal portion of the tubule is hypotonic, it allows the excretion of urine more dilute than normal body fluids. It is also used by collecting ducts to reabsorb water in the body and concentrate the tubular fluid to produce more concentrated urine than normal body fluids when dehydrated

Question 43

Outline the mechanism of vasopressin

Answer 43

When Vasopressin reaches the kidneys it enters the peritubular capillaries to enter the interstitial fluid and acts on its receptor located on the basolateral membrane of the tubular cells. Activation of this receptor leads to the addition of aquaporins on the luminal membrane meaning more water is reabsorbed.

Question 44

How would you form concentrated urine?

Answer 44

Vasopressin is present leading to vast amounts of aquaporins

Question 45

How would you form dilute urine?

Answer 45

Ensure no vasopressin is present therefore making the distal and collecting tubules impermeable to water

Question 46

Where is vasopressin produced?

Answer 46

It is produced by the hypothalmus and secreted by the posterior pituitary gland

Question 47

Why does alcohol make you pee alot?

Answer 47

Alcohol inhibits the secretion of vasopressin causing dehydration

Question 48

What is an adaptation in animals who live in arid environments?

Answer 48

They have longer nephrons enabling steeper concentration gradients

Question 49

What are the sphincters of the bladder?

Answer 49

The internal sphincter which is made of smooth muscle | The external sphincter which is made of skeletal muscle

Question 50

Outline the micurition reflex

Answer 50

It is initiated when stretch receptors within the bladder wall are stimulated. Stretch receptors trigger impulses into the spinal cord which in return will stimulate the parasympathetic supply to the bladder and inhibit the motor neurone supply to the external sphincter, Parasympathetic innervation causes the bladder to contract. However there is a voluntary component. Perception of bladder fullness appears before the external sphincter relaxes by reflex.