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My MCAT Biology > Excretory System > Flashcards

Excretory System Flashcards

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1
Q

Excretion

A

Disposal of waste products

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2
Q

Liver function in excretory system

A

Excretes wastes by chemically modifying them and releasing them into bile

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3
Q

What waste does the liver deal with specifically?

A

Hydrophobic/large waste which can’t be filtered by the kidney

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4
Q

Liver synthesizes

A

Urea and releases it into bloodstream

Urea: Carrier of excess nitrogen from protein breakdown because ammonia is toxic so must be converted into Urea

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5
Q

Large Intestine role in excretory system

A

Re-absorb wafter and ions from feces

Processes wastes already destined for excretion

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6
Q

Colon role in excretory system

A

Can excrete excess ions into the feces using active transport

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7
Q

Skin role in excretory system

A

Produces sweat (contains water, urea and ions)

Similar to urine, but not controlled by amount of waste needing to be excreted, controlled by sympathetic NS and temperature

–Secondary role

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8
Q

Kidney function in excretory system

A

Excretes hydrophilic wastes (i.e., sodium, bicarbonate, water)

Homeostatic role: Sensitive regulator that must keep concentrations at optimum levels as opposed to just dumping things

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9
Q

Roles of the kidney (3)

A
  1. excretion of hydrophilic waste
  2. Maintain constant solute concentration and pH
  3. Maintain constant fluid volume (BP & CO)
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10
Q

Kidney: filtration

A

Passing pressurized blood over a filter

Cells and proteins remain in the blood while wanter and small molecules are squeezed out into the renal tubule (filtrate) to be made into urine

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11
Q

Kidney: Selective reabsorption

A

Take back useful items from the renal tubule (water, glucose, AA)

Leave wastes and some water in the tubule

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12
Q

Kidney: Secretion

A

Adding substances to the filtrate in the renal tubule

INC rate of elimination from the blood

Most substances are added to the filtrate after filtration

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13
Q

Last step of urine formation: concentration and dilution

A

Selective reabsorption of water and decide to make concentrated urine or dilute urine

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14
Q

Renal Artery

A

Blood enters kidney from renal artery

Direct branch of the lower portion of the abdominal aorta

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15
Q

Renal Vein

A

Purified blood from kidney is returned to the circulatory system and empties into the inferior vena cava

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16
Q

Ureter

A

Urine leaves kidney through the ureter into the urinary bladder

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17
Q

Two sphincters controlling release of urine from the bladder:

A

Internal sphincter and external sphincter

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18
Q

Internal sphincter

A

Bladder reflexively contracts when the wall is stretched

Smooth muscle

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19
Q

External sphincter

A

Relaxed when the time is appropriate to pee

Skeletal muscle

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20
Q

Cortex and medulla of the kidney

A

Cortex: Outer region
Medulla: Inner region

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21
Q

Medullary pyramids of the kidney

A

Striations within the medulla due to collecting ducts

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22
Q

Papilla

A

Urine empties from the collecting ducts and leaves the medulla at the tip of a pyramid (papilla)

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23
Q

Calyx

A

Space that each papilla empties into

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24
Q

Renal pelvis

A

Urine collects here and empties into the ureter

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25
Q

Nephron contains two components:

  1. Capsule
  2. Renal tubule
A

Capsule: filtration takes place

RT: receives filtrate from capillaries and empties into a collecting duct which dumps urine into the renal pelvis

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26
Q

Blood vessels surrounding the nephrons: function

A

Carry arterial blood toward the capsule for filtration then surround the tubule to carry filtered blood and reabsorbed substances away from the tubule

27
Q

Blood from the renal artery flows into an ____ which branches into a ball of capillaries known as ____

A

Blood from the renal artery flows into an afferent arteriole which branches into a ball of capillaries known as glomerulus

28
Q

Blood from the renal artery flows into an afferent arteriole which branches into a ball of capillaries known as glomerulus, from there the blood flows into an ____

A

Efferent arteriole

29
Q

Constriction of the efferent arteriole results in

A

High pressure in the glomerulus which causes fluid (blood plasma) to leak out of the glomerular capillaries

30
Q

The fluid that leaks out of glomerulus when efferent arteriole constricts then

A

passes through a filter (glomerular basement)

31
Q

Glomerular basement

A

blood filter of leakage from glomerulus

32
Q

After blood filters through the glomerular basement it enters

A

Bowman’s capsule

33
Q

What substances DO NOT pass through the glomerulus basement / ARE NOT filtered, but rather remain in the blood in the glomerular capillaries and drain into the efferent arteriole?

A

Blood cells and plasma proteins do NOT get filtered

34
Q

Filtrate in the kidney’s tubule consists of:

Some of these substances must be returned to the bloodstream via

A

Water and small hydrophilic molecules (sugars, AA, urea)

Active transport extracted materials out of tubule and into blood stream

35
Q

Peri-tubular capillaries

A

Filtered blood transported out of tubule arrives here and is drained into venues that lead to renal vein

36
Q

Proximal convoluted tube (PCT) of the nephron

A

Location of most reabsorption of filtered blood (nearest the bowman’s capsule)

37
Q

All solute movement in the PCT is accompanied by ____

As a result:

A

Water movement

Water reabsorption occurs (70% of filtrate reabsorbed here)

38
Q

Distal convoluted tube (DCT) of the nephron

A

More regulated reabsorption via hormones

39
Q

Secretion in the kidney

A

Movement of substances into filtrate via active transport to increase removal from plasma

“Back up” to glomerulus that ensure everything that needs to get eliminated does get eliminated

40
Q

Most secretion occurs

A

in the DCT and collecting duct

41
Q

Secretion is the primary way that ___ and ____ are deposited into urine

A

drugs and toxins

42
Q

Distal nephron (includes collecting duct and DCT) function:

A

Adjustments made to urine to get correct volume and osmolarity

43
Q

Distal nephron is controlled by

A

ADH and aldosterone (hormones)

44
Q

Condition: dehydration

___ blood volume and ____ blood osmolarity

Function of the hormone ____:

A

Condition: dehydration

Low blood volume and High blood osmolarity

Function of the hormone ADH/vasopressin: Released by posterior pituitary to prevent water loss in urine by increasing water reabsorption in distal nephron (by making nephron permeable to water)

Water flows out of the distal nephron into kidney tissue to be returned into the blood

45
Q

Condition: After drinking a lot of water

___ blood volume and ____ blood osmolarity

Function of the hormone ____:

A

Condition: After drinking a lot of water

High blood volume and low blood osmolarity

need to deposit large volume of dilute urine

Function of the hormone ADH: not needed, collecting duct remains impermeable to water so water in filtrate remains in tubule and lost in urine (diuresed)

46
Q

Diuresis

A

Water loss in urine

prevented in dehydration, promoted during hydration

47
Q

Condition: BP Low

___ blood osmolarity

Function of the hormone ____:

A

Aldosterone released by adrenal cortex

Low blood osmolarity

Increased reabsorption of Na+ by distal nephron to increase osmolarity leading to increased thirst and water retention raising BP

48
Q

Condition: BP High

____ blood osmolarity

Function of the hormone ____:

A

High blood osmolarity

Function of the hormone Aldosterone: not released

Na+ is lost in urine and plasma osmolarity decreases with BP

49
Q

Triggers for release of aldosterone

A

Low BP, low blood osmolarity, low blood volume, and angiotensin II

50
Q

To INC BP:

  1. Aldosterone:
  2. ADH:
A
  1. Aldosterone causes Na+ absorption which increases plasma osmolarity
  2. ADH is secreted which results in increased water reabsorption and increased plasma volume
51
Q

PCT empties into the LOOP OF HENULE which is:

2 parts:

A

Loop that dips into the renal medulla (inner part of the kidney)

  • Descending limb of the loop of henule dips in (thin)
  • Ascending: heads out toward the cortex (thick and thin)
52
Q

Loop of henule is a countercurrent multiplier meaning:

A

Makes the medulla very salty, and this facilitates water reabsorption from the collecting duct

This is how kidney is capable of making urine with a much higher osmolarity than plasma

53
Q

Vasa Recta

A

Eager to reabsorb water released by the descending Loop of Henule because blood they contain is like coffee grinds which have been drained

Returns water reabsorbed by filtrate into the bloodstream

54
Q

How is the vasa recta performing countercurrent exchange?

A

The vasa recta are moving in opposite directions as the filtrate in the nephron

55
Q

Glomerular filtration rate (GFR) depends on

A

Pressure

56
Q

Juxtaglomerular apparatus (JGA)

A

Contact point between the afferent arteriole and the distal tubule

57
Q

At the JGA, cells at the afferent arteriole are called ____ and at the distant tubule are called _____

A

AA: juxtaglomerular (JG) cells
DT: macula densa

58
Q

JG cells are

A

Baroreceptors monitoring systemic BP

59
Q

When there is a decrease in BP, JG cells

A

secrete an enzyme called renin into bloodstream to catalyze conversion of angiotensinogen into angiotensin II by ACE in the lungs

ACT II is a powerful vasoconstrictor that immediately raises BP and stimulates release of aldosterone to INC BP by INC Na+ retention

60
Q

Macula dense cells are

A

Chemoreceptors that monitor filtrate osmolarity in distal tubule

61
Q

When filtrate osmolarity decreases, macula densa cells

A

stimulate JG cells to release renin

cause dilation of the afferent arteriole increasing blood flow to the glomerulus

62
Q

How does the kidney regulate pH?

A

When plasma pH too high: releases HCO3-

When plasma pH is too low: H+ is secreted

63
Q

What enzyme is involved in regulating pH in the kidney?

A

Carbonic anhydrase which catalyzes conversion of CO2 into carbonic acid which can dissociate into bicarbonate and a proton

64
Q

Changes in pH regulated by the kidney are fast or slow?

A

Slow

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