Chapter 10.1

Question 1

What does the excretory system consist of

Answer 1

-it consists of kidneys, ureters, bladder and urethra

Question 2

What is the difference between the cortex and the medulla of the kidneys

Answer 2

Cortex
->kidney’s outermost layer

Medulla
->it sits within the cortex

Question 3

Where do the renal artery, renal vein and ureter enter/exit from

Answer 3

-they enter/exit from the renal hilum

Question 4

Describe the movement of blood through the kidneys

Answer 4

• renal artery branches out
• > passes through the medulla
• > enter the cortex as afferent arterioles
• > then the afferent arteriole enters capillaries known as the glomeruli
• after blood passes through glomerulus
• > then it goes to the efferent arterioles

Question 5

What is the vasa recta

Answer 5

-they are capillaries that surround the loop of Henle

Question 6

What is the glomerulus surrounded by

Answer 6

-it is surrounded by the Bowman’s capsule

Question 7

What is the muscle lining the bladder referred to as? What kind of autonomic signalling causes it to contract

Answer 7

• it is referred to as the detrusor muscle

- >parasympathetic activity causes the detrusor muscle to contract

Question 8

What are the two sphincters that regulate the urination of an individual

Answer 8

Internal urethral sphincter

• > consists of smooth muscle
• > contracted in normal state
• > it is under involuntary control

External urethral sphincter

• > consists of skeletal muscle
• > under voluntary control

Question 9

What is the micturition reflex function

Answer 9

• this is when the detrusor muscles contract
• > internal sphincter then relaxes and allows an individual to urinate if they choose to relax the external sphincter
• urination itself is caused by the contraction of the abdominal musculature
• > which increases pressure within the abdominal cavity
• > resulting in compression of the bladder and increased urine flow rate

Question 10

Describe filtration in terms of movement of fluid between the glomerulus and the Bowman’s capsule

Answer 10

• blood that passes through the glomerulus is filtered as fluid into the Bowman’s space
• > collected fluid is known as filtrate

Question 11

What regulates movement of fluid into the Bowman’s capsule

Answer 11

-it is regulated by Starling forces

Question 12

Describe the Starling forces in the Bowman’s capsule in comparison to the glomerulus

Answer 12

Glomerulus

• > hydrostatic pressure here is significantly higher than the Bowman’s capsule
• > which causes fluid to move into the nephron

Bowman’s

• > the osmolarity of blood is higher than that of the Bowman’s space
• > resulting in pressure oppposing the movement of fluid into the nephron
• note however, that hydrostatic pressure of the glomerulus is much larger than the oncotic pressure of the blood
• > so blood still flows into the nephron

Question 13

Compare the filtrate that moves from the Bowman’s to glomerulus to that of blood

Answer 13

• filtrate is similar in composition to blood
• > but does not contain cells or proteins due to the filter’s ability to select based on size

-note that the filtrate is isotonic to the blood

Question 14

How does the body get rid of ammonia

Answer 14

• the liver converts ammonia to urea
• > urea is a neutral compound
• > it travels to the kidney and is secreted into the nephron for excretion with the urine

Question 15

Describe what happens in the proximal convoluted tubule

Answer 15

• amino acids, glucose, vitamins and majority of salts are reabsorbed along with water
• > almost 70% of filtered sodium will be reabsorbed here

-note waste like hydrogen ions, potassium ions, ammonia and urea also enter the PCT(HUNK)

Question 16

Describe what happens in the descending loop of Henle

Answer 16

• this section dives deep into the medulla
• the descending limb is permeable only to water
• > therefore, the medulla has an ever increasing osmolarity as it travels deeper into the medulla
• note that as the descending limb goes deeper into the medulla
• > there is an increasing interstitial concentration
• > which favours the outflow of water from the descending limb

Question 17

How does the countercurrent multiplier system work? What is its function

Answer 17

• it is created by the vasa recta and nephron
• the flow filtrate in the loop of Henle is in the opposite direction from the flow of blood through the vasa recta
• > if the two flowed in the same direction, equilibrium would be reached quickly
• by having the two flow in opposite directions, the filtrate is exposed to hypotonic blood(great amount of solutes)
• > so water flows out

Question 18

Describe what happens in the ascending loop of Henle

Answer 18

• only salts here can leave the nephron
• > while water cannot leave(non-permeable to water)

-the filtrate becomes hypotonic compared to the interstitium

Question 19

What are the characteristics of the diluting segment of the loop of Henle

Answer 19

• here the loop of Henle becomes thicker
• > the cells lining the tube become larger
• > these cells contain large amount of mitochondria
• > allowing for the reabsorption of sodium and chloride by active transport

Question 20

What is the general characteristic of the distal convoluted tubule? What hormone does it respond to?

Answer 20

• site of waste production
• DCT also responds to aldosterone
• > aldosterone promotes the reabsorption of sodium
• > making water follow in the path of the sodium

Question 21

What are the general characteristics of the collecting duct? What hormone does it respond to?

Answer 21

• it is the part of the nephron that can change its permeability
• > as permeability increases, its water reabsorption increases well
• > resulting in further concentration of the urine
• note both ADH and aldosterone interact with the collecting duct
• > allows for greater water retention and more concentrated urine output

Question 22

How is aldosterone released? Describe the initial mechanisms behind this process.

Answer 22

• aldosterone is a hormone that responds to decreased blood pressure
• decreased blood pressure stimulates release of renin from the juxtaglomerular cells
• > renin then cleaves angiotensionogen
• > when then forms angiotensin 1
• > angiotensin 1 then is converted to angiotensin 2 using the angiotensin-converting enzyme
• > this last step promotes the release of aldosterone from the adrenal cortex

Question 23

How does ADH impact the pressure in the blood

Answer 23

• it directly alters the permeability of the collecting duct

- >allows more water to be reabsorbed by making cell junctions of the duct leaky

Question 24

What can inhibit ADH release?

Answer 24

-caffeine can inhibit ADH release and lead to the frequent excretion of dilute urine

Question 25

How can the cardiovascular system maintain blood pressure through vasodilation or vasoconstriction

Answer 25

• it can constrict the afferent arterioles
• leading to lower blood pressure reaching the glomeruli
• > this vasoconstriction leads to renin release, which again helps to increase blood pressure