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Flashcards in Chapter 10 - Homeostasis Deck (63)
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1

What are the main functions if the excretory system?
(4)

Regulate...

1. Blood pressure
2. Blood osmolarity
3. Acid-base balance
4. Removal of nitrogenous wastes

2

What do AFFERENT and EFFERENT arterioles do?

Afferent arteriole: goes from the artery through the medulla and to the cortex

Efferent arteriole: lead blood away from AFFERENT arterioles to the second capillary bed.

3

What structures does the blood pass through in the kidneys / to get through the nephron?

Renal artery
Afferent arteriole
Glomerulus / Bowman's capsule
(First capillary bed)
Efferent arteriole
(Second capillary bed) - "vasa recta"
Proximal convoluted tubule
Loop of henle
Distal convoluted tubule
Collecting duct

4

What is the vasa recta?

The capillaries that surround the loop of henle (second capillary bed)

5

What is the DETRUSOR muscle?

Muscle associated with the internal urethral sphincter

Stretch receptors detect bladder is full
Parasympathetic neurons fire
Detrusor muscle CONTRACTS
Internal sphincter relaxes

6

Micturition reflex

The contraction of the DETRUSOR muscle leads to the relaxation of the internal urethral sphincter

7

How does one urinate?

Voluntary control of external urethral sphincter

Urination is facilitated by the contraction of abdominal musculature, which creates pressure in the abdominal cavity and hence pressure on the bladder --> increases urinary flow rate

8

What is the MAIN role of the kidneys?

To regulate blood volume and osmolarity

9

What are the the main functions of the kidneys:

1. Filtration
2. Secretion
3. Reabsorption

10

What is a portal system?

Consists of two capillary beds through which blood must travel before returning to the heart

11

What are the three main portal systems in the body?

1. Kidney portal system
2. Hypophyseal postal system (connects hypothalamus and ant pituitary)
3. Hepatic portal system (connects the gut tube and the liver)

11

WHAT IS (brief) filtration, secretion, and re absorption:

FILTRATION: movement of SOLUTES from the blood to the filtrate at Bowman's capsule

SECRETION: movement of SOLUTES from blood to filtrate anywhere but the capsule

REABSORPTION: movement of SOLUTES from filtrate BACK TO BLOOD

12

How is the glomerulus like a sieve?

Small molecules dissolved in the blood will pass through the tiny pores
(Glucose)

Large molecules will not, and be removed into the urine
(Blood cells, proteins)

**Blood cells or proteins found in the urine indicate a problem with the glomerulus

13

What are Starling forces?

Results in the movement of fluid into Bowman's space

Account for the pressure differential between the blood and Bowman's space

(Account for both HYDROSTATIC and ONCOTIC pressure differences)

14

Hydrostatic pressure versus osmolarity in the glomerulus / Bowman's space

Hydrostatic pressure: higher pressure in the glomerulus so fluid wants to move to Bowman's space

Osmotic pressure: higher concentration of solutes in the glomerulus so fluid would want to move TO the glomerulus

BUT HYDROSTATIC PRESSURE IS MUCH GREATER

15

Usually, fluid flows from glomerulus to Bowman's space. What might cause de-arrangement of this?

Obstructed ureter (ie kidney stone)

16

How much (volume) of blood is filtered by the kidneys?

180 liters per day is filtered

This is about 36 times the amount of blood we have (4.7-5 L)

Aka, our entire volume of blood is filtered approx every 40 mins

17

What substances are typically reabsorbed from the filtrate?

Glucose
Amino acids
Vitamins

ALSO A LOT OF WATER, ie ADH and aldosterone can alter quantity of water re absorbed at the kidney to maintain blood pressure

18

What substances are typically "waste" and not re absorbed?

Hydrogen ions
Potassium ions
Ammonia / urea

"HUNK"

H+
Urea
NH2
K+

19

What happens at the PROXIMAL CONVOLUTED TUBULE?

(Closest to the capsule)

REABSORPTION
Of the things the body wants to keep
-glucose
-amino acids
-water soluble vitamins
-salts
-WATER

SECRETION
From the blood into the filtrate
-hydrogen
-potassium
-ammonia and urea

20

What is the interstitium?

What happens to solutes that end up here?

The connective tissue that surrounds the nephron

Solutes here are picked up by the vasa recta and hence returned to the blood

21

What happens at the DESCENDING LOOP OF HENLE?

Only permeable to water

Goes deep into the medulla, which has INCREASING osmolarity

Water flows out from the filtrate to the medulla (aka the interstitium) and goes to the vasa recta to go back into the blood

22

How can the kidneys change osmolarity in the medulla?

Why?

The medulla can be isotonic with blood (when the body wants to excrete water)

The medulla can be up to four times as concentrated (when it wants to conserve water and maximize reabsorption)

In order to get maximum reabsorption and conserve water

23

What is the COUNTER-CURRENT MULTIPLIER SYSTEM?

The flow of filtrate through the loop of henle is in the opposite direction as the flow of blood in the vasa recta.

This is to prevent equilibrium (if they both were going in the same direction) and allows max reabsorption of water!

24

What happens at the ASCENDING LOOP OF HENLE?

Only permeable to SALTS

Due to high concentrations of salt at the medulla and decrease as the loop goes up, salt moves out from the filtrate as it goes up.

25

Comment on the thickness of the loop of henle

Thickens as the ASCENDING loop moves to the outer medulla.

The loop itself not thicker but cells around it are larger and contain a lot f MITOCHONDRIA to actively transport sodium and chloride.

26

What is the diluting segment of the loop?

The thick portion

So much Na and Cl is re absorbed that the filtrate (urine) is more dilated than the blood!

This is the only place that this may happen

This is useful when over hydrated and needing to get rid of water

27

Filtrate at the beginning at the loop is isotonic to the interstitium. How does it compare at the end?

It is a bit more diluted (lower osmolarity than the interstitium)

28

What happens at the DISTAL CONVOLUTED TUBULE?

ALDOSTERONE can act on the DCT

Promotes reabsorption of sodium, and water tends to follow

Also, more waste secretion (like the PCT)

29

What happens at the COLLECTING DUCT?

Final concentration of urine.

Both ADH and aldosterone act here.

More permeable duct: more water and salt can be re absorbed, creating a very concentrated urine
*ADH and aldosterone encourage this

Less permeable duct: nothing passes easily, water and sodium stays in the collecting duct and is excrete in urine. This happens when the body is well hydrated.