Chapter 26: The Urinary System

Question 1

Functions of the urinary system

Answer 1

• excretion of waste
• regulate water content (maintain 0.3M osmolarity)
• regulate blood pH

Question 2

The kidneys are retroperitoneal, what does this mean?

Answer 2

They are covered by parietal peritoneum on the anterior (front) surface, and held against the dorsal body wall on the posterior (back) surface

Question 3

What are the 3 layers of tissue covering the kidneys?

Answer 3

Outermost

1. Renal Fascia - dense irregular CT binds kidney to dorsal body wall.
2. Adipose capsule - fatty tissue for protection.
3. Renal capsule - dense irregular CT that maintains kidney shape and absorbs shock

Innermost

Question 4

What is the functional unit of the kidney?

Answer 4

The nephron

Question 5

What are the organs of the urinary system?

Answer 5

• 2 kidneys
• 2 ureters
• 1 urinary bladder
• 1 urethra

Question 6

What vessels does the hilus region contain?

Answer 6

• the ureter
• a renal artery (supplied blood to kidney)
• a renal vein (takes blood away from kidney)

Question 7

What are the 2 types of nephrons, what regions are they located in, and what percentage of all nephrons are in each region?

Answer 7

Cortical nephrons - nephrons found in the cortex of kidney (85% of all nephrons)

Juxta-medullary nephrons - located closer to the medulla region of the kidney (15% of all nephrons)

Question 8

Which type of nephron has a longer loop of Henle? What is this significant?

Answer 8

Juxta-medullary nephron have longer loops of henle.

They reach to the renal pyramids of the medulla, and are able to maintain a salt gradient to help the body conserve water

Question 9

What are the 2 parts of the nephron and what does each part contain?

Answer 9

Renal Corpuscle - contains the glomerulus and bowman’s capsule

Renal Tubule - contains the proximal/distal convoluted tubules, loop of henle, the descending/ascending limbs, and the collecting duct

Question 10

Pathway of urine production and flow

Answer 10

Glomerulus -> bowman’s capsule -> proximal convoluted tubule -> loop of Henle -> distal convoluted tubule -> collecting duct -> papillary duct -> minor calyx -> major calyx -> renal pelvis -> ureter -> urinary bladder -> urethra

Question 11

What many ml of blood per minute does the renal artery deliver to both kidneys

Answer 11

Approx. 1200 ml/min

Question 12

Pathway of blood supply to the kidneys

Answer 12

Renal artery -> Afferent arterioles -> Glomerular capillaries -> Efferent arterioles -> Renal vein

Question 13

What are the 3 steps to urine formations?

Answer 13

1. Glomerular filtration
2. Tubular reabsorption
3. Tubular secretion

Question 14

Glomerular filtration

Answer 14

Filters substances from the glomerulus to the bowman’s capsule based on size

Note: only small molecules can pass through
Ex. Water, urea, Na, Cl

Question 15

What 3 things make up the the filtration membrane for glomerular filtration?

Answer 15

Closest to glomerulus

1. Glomerular endothelial cell pores
2. Glomerular basement membrane
3. Podocyte filtration slits (of bowman’s capsule)
   Closest to bowman’s capsule

Question 16

Why is the blood pressure in the glomerulus so high?

Answer 16

Since the efferent arteriole is smaller in diameter that the afferent arteriole
(more is coming in than being taken out)

This causes the blood pressure to increase to 55mmHg, where in the other capillaries it is only 18mmHg

Question 17

What are the 3 pressures that affect glomerular filtration called? Do they promote or oppose filtration?

Answer 17

Promotes filtration out of glomerulus into bowman’s capsule :
Glomerular blood hydrostatic pressure

Opposes filtration, wants fluid to move back into glomerulus:
Capsular hydrostatic pressure
Blood colloid osmotic pressure

Question 18

What is the formula to find the Net Filtration Pressure?

Answer 18

GBHP - (CHP + BCOP)

Basically saying:
Promotes - (oppose + oppose) = net filtration pressure

Question 19

How much of the filtrate will be reabsorbed?

Answer 19

99%

We filter 180 L per day, but only produce about 1-2 L of urine per day, the rest of filtrate is reabsorbed.

Question 20

Tubular reabsorption

Answer 20

A process that removes certain substances (such as Na and glucose) from the filtrate and returns them to the blood (body reabsorbs what it needs).

Usually occurs in the proximal convoluted tubule.

Question 21

What are the 2 routes of tubular reabsorption?

Answer 21

1. Trascellular route - ACTIVE process that requires energy to transport substances through the membrane of tubule, then uses and NA/K pump.
2. Paracellular route - PASSIVE process where substances freely move into the tubule without the use of energy.

Question 22

Tubular secretion

Answer 22

Remove certain substances from the blood and add it to the filtrate.

Usually occurs in the proximal and distal convoluted tubules.

Question 23

What is the function of ureters, and what are they lined with?

Answer 23

Function:
Transports urine from the renal pelvis to the urinary bladder

Lined with transitional epithelium

Question 24

What is the function of the urinary bladder? What is it lined with and what is its muscle layer called?

Answer 24

Function:
Temporary storage of of urine with a capacity of about 500ml

Lined with transitional epithelium. Muscle layer is called the detrusor muscle

Question 25

What is the function of the urethra? How long is it for males and females?

Answer 25

Function:
Brings urine from the urinary bladder out to be expelled.

Females: approx. 4cm long
Males: approx. 20cm long

Question 26

What is micturition? How does it work?

Answer 26

The action of urinating

When the bladder is at about 200-400ml full it stretches the bladder wall and stimulates receptors that send an impulse to the spinal cord up to the pons.
When you voluntarily attempt to to urinate, the pons sends impulses to contract the detrusor muscle of the bladder to release the urine

Question 27

Antidiuretic hormone location and function

Answer 27

Location:
Made in hypothalamus, stored in posterior pituitary gland.

Function:
Increases water reabsorption so that there is less urine volume and more urine concentrate

Question 28

Aldosterone hormone location and function

Answer 28

Location:
Cortex of adrenal gland

Function:
Increase the reabsorption of Na, Cl, and water out of the filtrate and into the blood, and secretion of K out of the blood into the filtrate

Question 29

Which is smaller, the efferent or efferent arteriole?

Answer 29

Efferent arteriole is smaller (causes high BP in glomerulus since more goes in than out)