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Biology MCAT > Excretory System > Flashcards

Excretory System Flashcards

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1
Q

What are Kidneys?

A

Kidneys are organs that filter our blood and send that filtrate out through the ureters to the bladder.

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2
Q

What are ureters?

A

Ureters are tubes that extend from the kidney. They carry the filtrate of the kidneys to the urinary bladder.

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3
Q

What are the two divisions of the Kidney?

A
  1. The Cortex 2. The Medulla
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4
Q

What is the urinary bladder?

A

The Urinary bladder is a large sac that holds urine for storage. It is fed by the ureters and it feeds into the urethra.

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5
Q

What is the urethra?

A

The urethra is a tube that extends from the bladder and empties into the outside world. Urine stored in the bladder is sent through the urethra so it can be excreted.

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6
Q

What is the hilum?

A

The hilum is a large slit in the kidney where the ureter and blood vessels enter the kidney.

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7
Q

Describe the portal system in the kidney?

A

The renal portal system consists of the following two capillary beds in series. The first capillary bed is the glomerulus in the bowman’s capsule. Instead of returning to venous circulation, blood leaves the glomerulus in the bowman’s capsule and enters the capillary bed surrounding the loop of henle known as the vasa recta.

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8
Q

What is an afferent arteriole, in the context of the kidney?

A

The afferent arterioles are the arterioles moving blood away from the heart and towards the kidney (specifically, the capillary bed known as the glomerulus)

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9
Q

What is an efferent arteriole, in the context of the kidney?

A

The efferent arterioles are the arterioles moving blood away from the glomerulus and towards the loop of henle.

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10
Q

What is the glomerulus?

A

The glomerulus is the convoluted capillary bed that can be found in the bowman’s capsule of the nephron. It has pores in it that allow small things in the blood to leave, but big things to stay.

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11
Q

What is the basic functional unit of the kidney?

A

The nephron

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12
Q

What are the structures of the Nephron, in order?

A

1.Glomerulus/Bowman’s capsule
2. Proximal Convoluted Tubule
3. Descending limb of the loop of Henle
4. Ascending limb of the loop of Henle
5. Distal Convuluted Tubule
6. Collecting Duct MNEMONIC: Bad Penguins Do Act Depressed and Cold

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13
Q

What is the bowman’s capsule?

A

The bowman’s capsule is a cuplike structure that takes the filtrate from the glomerulus and sends it through the loop of Henle, starting with the Proximal Convuluted Tubule

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14
Q

How many sphincter’s does the urinary bladder have?

A
  1. An internal sphincter and an external sphincter.
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15
Q

The internal sphincter of the bladder is made of [smooth or skeletal?] muscle

A

The internal sphincter of the bladder is made of smooth muscle And is therefore under autonomic control!

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16
Q

The external sphincter of the bladder is made of [smooth or skeletal?] muscle

A

The external sphincter of the bladder is made of skeletal muscle And is therefore under voluntary control!

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17
Q

What are three processes by which the Kidney filters the blood and maintains blood concentration and volume?

A
  1. Filtration 2. Secretion 3. Reabsorption
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18
Q

What is filtration?

A

Filtration is the passive process by which things that are small enough to pass through the glomerular pores are pushed into the bowman’s capsule by the pressure differential. This is caused by Starling forces, just like in the capillaries.

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19
Q

What kinds of things can make it through the glomerular pores and what kinds of things can’t?

A
  1. Can - small things like glucose, water, electrolytes, fatty acids, single amino acids, etc. 2. Can’t - big things like cells, polypeptide chains, etc.
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20
Q

Filtration is a [active or passive] process

A

Filtration is a passive process

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21
Q

What is Secretion?

A

Secretion is when the body either actively or passively transports waste products into the nephron that were too big to pass through the glomerular pores.

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22
Q

What determines the activty of secretion and reabsorption in the nephron?

A

The composition of solutes in the blood at the time. For example, a high protein diet will result in a lot of Ammonia in the blood. Ammonia will be converted into a lot of Urea in the liver which will get secreted into the urine.

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23
Q

What is Reabsorption?

A

Sometimes useful molecules are small enough to pass through the glomerulus e.g. Sugar and Amino Acids. These are important building materials for the body, and the body wants to keep them in the blood not urinate them out. Reabsorption then, is the process by which the body actively transports important solutes that have been filtered or secreted into the urine back into the blood.

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24
Q

What are the kidney’s two main goals in filtering the blood?

A
  1. Keep what the body needs (sugars, amino acids, sometimes water etc.) 2. Lose what the body doesn’t need (waste products, sometimes water, etc.)
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25
Q

What occurs in the Proximal Convoluted Tubule?

A

In the Proximal Convuluted Tubule the useful molecules that passed through the glomerular pores are reabsorbed (amino acids, glucose, vitamins, majority of salts, and water) into the vasa recta. Also in the PCT, a number of waste products are secreted from the blood into the PCT for excretion (H+, K+, Urea, NH3, etc.)

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26
Q

What are the major waste productes excreted in the urine?

A

H+ ions, Urea, NH3, and K+ MNEMONIC: DUMP the HUNK

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27
Q

What happens as you get deeper into the kidney?

A

As you move deeper into the kidney, the concentration of solutes in the interstitium increases. This is so that the interstitium stays isotonic with the loops of henle and there isn’t a rush of water into (explosion!) the loops or out of (collapse!) the loops.

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28
Q

What is the interstitium?

A

The interstitium is the area surrounding the nephron that it exchanges solutes with.

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29
Q

The concentration of the filtrate changes dramatically as it moves through the nephron. What prevents water from rushing into the nephron and bursting it when the filtrate is very concentrated, and what prevents water from rushing out of the nephrone and collapsing it when the filtrate is very dilute?

A

The concentration of solutes in the interstitium changes depending on the location of the nephron. Therefore, those places in the nephron that have very concentrated filtrate are surrounded by a concentrated, isotonic interstitium. The places in the nephron that have very dilute filtrate are surrounded by a dilute, isotonic interstitium.

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30
Q

What does it mean to be isotonic?

A

An isotonic solution is a solution that is as concentrated as the interior of the cell/tubule/etc. Isotonic solutions lose as much water to their surroundings as they gain, resulting in no net change in the amount of water inside or outside the cell.

31
Q

What does it mean to be in a hypotonic solution?

A

Hypotonic solutions are less concentrated than the interior of the cell/tubule/etc in question. Water follows the concentration of solutes and rushes into the cells, causing them to swell with water and potentially burst.

32
Q

What does it mean to be Hypertonic?

A

A Hyper tonic solution is a solution that is more concentrated than the interior of the cell/tubule/etc. Water follows the concentration of solutes and rushes out of the cell, causing it to dry out and shrivel.

33
Q

What happens in the descending loop of Henle?

A

The descending loop of Henle is only permeable to water. As it descends into the medulla, the concentration of the interstitium increases, which favors the outflow of water. This is exactly what the descending loop of Henle does, remove water from the filtrate. Note, if the body has a lot of water and does not need to reabsorb it, the interstitium’s concentration will change to reduce the outflow of water from the filtrate back into the blood.

34
Q

What happens in the ascending loop of Henle?

A

The ascending loop of Henle is only permeable to salts, and is impermeable to water. As the ascending loop ascends, the interstitium becomes less and less concentrated, favoring the removal of salts from the filtrate and back into the interstitium (and blood).

35
Q

What is the Diluting Segment of the Nephron?

A

The Diluting segment is the thicker part of the ascending loop of henle near the top of its ascension. If for some reason the ascending loop of Henle was not able to reabsorb enough salts passively, this last segment of the loop of henle will actively transport out salts to further dilute the urine. Note, that because this is an active process, it won’t stop when the interstitium and the filtrate equilibrate. Energy can keep being spent to make it so that salts go against the concentration gradient into the filtrate. This means that the Diluting Segment is the only structure in the kidney that can make filtrate even more dilute then blood itself.

36
Q

What happens in the Distal Convoluted Tubule?

A

The DCT responds to Aldosterone, which promotes sodium Reabsorption. Sodium reabsorption will also lead to an increase in water reabsorption (because water follows the sodium molecules, i.e. osmosis/osmotic pressure). The DCT is also a site of waste product secretion, like the PCT.

37
Q

What happens in the Collecting Duct?

A

In the collecting duct, the final concentratin of the urine is altered. This occurs because the collecting duct’s permability to water can be modified by Aldosterone or ADH. The amount to which the collecting duct is permeable to water will determine the urine’s final concentration.

38
Q

As the permeability of the collecting duct increases, it is easier for water to be reabsorbed. This causes the urine to become [more or less concentrated?]

A

As the permeability of the collecting duct increases, it is easier for water to be reabsorbed. This causes the urine to become more Reabsorption is the movement of things from the urine to the blood. If water is moving from the urine into the blood, there is less water in the urine, i.e. more concentrated urine.

39
Q

What exactly does Aldosterone do to the DCT to exert its effects?

A

Aldosterone puts Sodium Potassium Pumps in the membrane of the DCT. This causes 2 Potassium’s to enter the DCT, 3 Sodiums to leave, and water to follow the sodium out of the DCT (net osmotic pressure outwards).

40
Q

Aldosterone acts on the [DCT or PCT?]

A

Aldosterone acts on the DCT Mnemonic: Damnit Aldosterone

41
Q

What exactly does ADH do to the collecting duct to exert its effects?

A

ADH punches holes in the membrane of the collecting duct through which water can pass. Therefore, as ADH increases, the amount of these holes increases, and more water passes from the urine back into the blood.

42
Q

How are the ways ADH and Aldosterone affect the reabsorption from the kidney different?

A

ADH moves water alone from the collecting duct to the blood. This water increases the blood volume, but dilutes the concentration of the blood. Aldosterone moves sodium ions from the DCT into the blood, and then water follows these ions. This water increases the blood volume and the sodium ions maintain the concentration of the blood.

43
Q

How do the kidneys affect the body’s maintenance of blood pH?

A

The kidneys can selectively secrete Hydrogen Ions or Bicarbonate ions, altering the equilibrium of the bicarbonate buffer equation and thereby affecting our blood pH.

44
Q

How do the kidneys affect blood pressure?

A

The kidneys control the amount of water and salts reabsorbed into the blood. As the amount of water in the blood goes up, the blood pressure goes up.

45
Q

What are the three layers of the skin?

A
  1. Hypodermis 2. Dermis 3. Epidermis
46
Q

What are the 5 layers of the epidermis from deepest to superficial.

A
  1. Stratum Basale 2. Stratum Spinosum 3. Stratum Granulosum 4. Stratum Lucidum 5. Stratum Corneum MNEMONIC: Big Spiders Grab Little Children
47
Q

What is the function of the Stratum Basale?

A

The Stratum Basale contains stem cells and is repsonsible for the creation of Keratinocytes, the predominant cells of the skin that produce Keratin. The Stratum Basale also houses the melanocytes.

48
Q

What is the function of the Stratum Spinosum?

A

In the Stratum Spinosum, skin cells become connected to one another. This is also the laayer that houses Langerhans cells.

49
Q

What is the function of the Stratum Granulosum?

A

In the Stratum Granulosum, the keratinocytes die and lose their nuclei.

50
Q

What is the function of the Stratum Lucidum?

A

The stratum Lucidum is an optional skin layer that is only present in thick hairless skin (like the skin on the plams or the soles of the feet). It is nearly transparent and tough.

51
Q

What is the function of the Stratum Corneum?

A

The Stratum Corneum consists of several dozen layers of flattened dead keratinocytes. The keratinocytes at this point are basically just sacs of keratin. These sacs form a barrier that prevents invasion by pathogens and loss of water.

52
Q

What are fingernails and hair made of?

A

Fingernails and hair are made of keratin and are produced by specialized skin cells.

53
Q

What is a melanocyte?

A

A melanocyte is another type of cell found in the epidermis. It is derived from Neural Crest cells and is found in the stratum Basale. These cells produce melanin, which pigments the skin to protect DNA from ultraviolet radiation.

54
Q

What is a Langerhan’s cell?

A

A langerhan’s cell is just the name for a specialized macrophage found in the skin. These cells reside in the stratum spinosum.

55
Q

What is the Dermis?

A

The Dermis is the layer of skin underneath the epidermis.

56
Q

What are the two layers of the Dermis?

A
  1. Papillary Layer 2. Reticular Layer
57
Q

Describe the papillary layer of the dermis

A

The papillary layer is the upper layer of the dermis and it is composed of loose connective tissue.

58
Q

Describe the reticular layer of the dermis

A

The reticular layer is the deeper and more dense layer in the dermis. This is where sweatglands, blood vessels, and hair follicles reside originate from.

59
Q

What are the 5 types of sensory neurons found in skin?

A
  1. Merkel Cells 2. Meissner’s Corpuscles 3. Ruffini Endings 4. Pacinian Corpuscles 5. Free nerve endings
60
Q

What are Merkel Cells?

A

Merkel cells are sensory neurons present at the epidermal-dermal junction. These cells are responsible for deep pressure and texture sensation on the skin.

61
Q

What are Meissner’s Corpuscles?

A

Meissner’s Corupsucles are sensory neurons in the dermis that respond to light touch.

62
Q

What are Ruffini Endings?

A

Ruffini endings are sensory neurons in the dermis that are responsible for stretch sensation.

63
Q

What are Pacinian corpuscles?

A

Pacinian corpuscles are sensory neurons found in the dermis that are responsible for deep pressure and vibration sensation.

64
Q

What do the free nerve endings in our skin allow us to feel?

A

Pain

65
Q

What is the hypodermis?

A

The hypodermis is a layer of connective tissue that connects the skin to the rest of the body. This layer contains fat and fibrous tissue.

66
Q

What are the four ways the skin can thermoregulate the body?

A
  1. Sweating
  2. Piloerection
  3. Vasodilation
  4. Vasoconstriction
67
Q

How does sweating cool us down?

A
  1. Sweating causes water to appear on the surface of our skin.
  2. The water, now in contact with the hot skin, enters into thermal exchange, with heat going from the skin to the water.
  3. The water gets so hot that it evaporates, which also sucks heat from the skin.
68
Q

What is unique about the way sweat glands are innervated?

A

Unlike all other postganglionic sympathetic neurons, the sweat gland postganglionic neurons are cholinergic (acetylcholine). This is unique because every other postganglionic sympathetic neuron is noradrenergic (norepinephrine).

69
Q

How does vasodilation help cool the body?

A

In vasodilation, the arteries open up which brings a lot of blood to the skin. This moves more of the total heat in the body to the skin where it can dump its heat into boiling the sweat on the surface of the skin.

70
Q

What causes arrector pili muscles to contract?

A

Cold conditions.

71
Q

What are arrector pili?

A

Arrector piili are muscles that cause the hairs of the skin to stand up.

72
Q

How does our hair standing on end heat us up?

A

When our hair stands straight up, it helps to trap a layer of heated air near the skin.

73
Q

How does vasoconstriction keep us warm?

A

Vasoconstriction tightens the arteries, meaning less blood is at the surface of the skin where it will dump all its heat into the cold air.

74
Q

What is the difference between white fat and brown fat?

A

White fat helps is permanent fat that helps insulate the body. Brown fat is semi-temporary fat (we lose most of it as we grow out of infancy) that is purposefully energy inefficient so it loses a lot of chemical energy in the form of heat. This helps keep the body warm.

Biology MCAT (12 decks)

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