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Malika Biology MCAT > Chapter 10 - Excretory System > Flashcards

Chapter 10 - Excretory System Flashcards

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1
Q

What are the main functions of the excretory system?

A

Regulating blood pressure, regulating blood osmolarity, regulating systemic HCO3- concentration, and removal of nitrogenous wastes (urea, ammonia)

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2
Q

How do the kidneys specifically regulate/maintain systemic HCO3- concentration?

A

By reabsorbing most of the HCO3- back into the blood at the PCT and by excreting acid…
How is acid exactly excreted by the kidneys?
1) Excretion in the form of a buffer w/ phosphate (not directly just H+ protons)
2) MAIN method - excretion of ammonium (NH4+)

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3
Q

Example: If a patient is found to have acidemia, how do we expect the kidneys to respond to maintain pH homeostasis?

A

The kidneys will increase reabsorption of HCO3- at the PCT.

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4
Q

The kidneys outer most layer is called the ______.

A

Cortex

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5
Q

The kidneys inner layer is called the ______

A

Medulla

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6
Q

What is the renal pelvis?

A

It is the widest part of the ureter that sits at the base of the kidneys and it is where all the urine empties into.

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7
Q

What is the portal system?

A

It is two capillary beds in series, through which blood must travel before returning to the heart. There are three major portal systems in the body.

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8
Q

Describe the portal system in the kidneys.

A

The afferent arterioles branch out from the renal artery and enter the cortex where they connect to glomeruli (a bunch of capillaries). Once blood is filtered in the glomeruli, it exits via the efferent arteriole which then branches of into more capillaries that surround the loop of Henle.

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9
Q

What is a glomerulus?

A

It is a tuft of capillary beds located in the Bowmans capsule. It is the site where a glomerular filtration occurs (filtration of blood).

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10
Q

What is filtration?

A

The process of filtering out fluid from the blood in the glomeruli which travels to the bowman’s capsule and into the proximal convoluted tubule of the nephron.

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11
Q

The glomeruli is unable to filter our what two things? Why?

A

Cells and proteins because they are too large to pass through the glomeruli capillaries, so they remain in the blood and flow out of the efferent arteriole.

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12
Q

What is the name of the fluid that collects in the Bowmans capsule due to filtration?

A

Filtrate

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13
Q

What causes the movement of fluid from the glomeruli into the Bowmans capsule?

A

Starling forces - the hydrostatic pressure in the glomerulus is significantly higher than that in the Bowmans capsule which causes the fluid to be pushed out and moved into the Bowmans capsule

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14
Q

What is secretion?

A

It is the process of moving byproducts and waste such as urea, H ions, excess K+, acids other bases from the blood to the filtrate in the nephron tubule. This allows for waste products to get excreted in the urine.

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15
Q

What is reabsorption and it’s purpose?

A

Reabsorption is the movement of solutes from the filtrate to the blood. The purpose is if some substances are in the filtrate, they may be taken back into the blood for use by the body. These include electrolytes, glucose, amino acids, vitamins.

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16
Q

When blood osmolarity is low, water reabsorption (increases/decreases) and solute reabsorption (increases/decreases).

A

Decreases, increases

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17
Q

When blood osmolarity is high, water reabsorption (increases/decreases) and solute reabsorption (increases/decreases)

A

Increases, decreases

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18
Q

The kidneys can also maintain acid-base balance in the blood. What is the mechanism by which they respond to high blood pH? What is the mechanism by which they respond to low blood pH?

A

For high blood pH, the kidneys increase the reabsorption of H+ ions and excrete more bicarbonate ions.
For low blood pH, the kidneys excrete more H+ ions and reabsorb more bicarbonate ions.

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19
Q

Name the different parts of the nephron

A

Bowman’s capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule, collecting duct

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20
Q

Mnemonic for the major waste products secreted in the urine

A

Dump the HUNK:
H+ ions
Urea
NH3
K+

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21
Q

What occurs in the proximal convoluted tubule?

A

-reabsorption of almost 100% of amino acids, glucose, water-soluble vitamins, salts, and water through mechanisms of passive and active transport
-reabsorption of 85% of HCO3-
-Secretion of waste products like H+ ions, urea, NH3, K+

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22
Q

The loop of Henle is divided into the…

A

Descending limb and ascending limb

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23
Q

The loop of Henle descends into the _________.

A

Medulla of the kidney

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24
Q

What is the difference between the descending limb, and the ascending limb of the loop of Henle?

A

The descending limb is permeable to water, so all the focus is on the maximal reabsorption of water back into the blood through aquaporin channels, especially if person is dehydrated.
The ascending limb is impermeable to water, but permeable to salts (Na and Cl) which allows the urine to also become more dilute as NaCl leaves the tubule. In the thin part of the ascending limb, NaCl is passively diffuses while in the thick part of the ascending limb, NaCl is actively transported.

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25
Q

What occurs in the distal convoluted tubule?

A

This portion of the nephron responds to the hormone aldosterone, which adds Na channels to promote NaCl reabsorption in response to low blood pressure/volume. K+ and H+ are selectively secreted into the filtrate, when pH is too acidic.

26
Q

What is the responsibility of the collecting duct?

A

The main responsibility is to respond to the hormone: ADH/also known as vasopressin according to the body’s blood pressure & blood osmolarity.
It has the ability to hold aquaporin channels in its membrane for additional reabsorption of water.

27
Q

If a person is well hydrated, the urine will be more (concentrated/dilute).

A

Dilute

28
Q

If a person is dehydrated, their urine will be (concentrated/dilute).

A

Concentrated

29
Q

Define GFR and how to calculate it.

A

GFR is the volume of glomerular filtrate formed per minute.

(Glomerular Hydrostatic Pressure - Bowman’s Hydrostatic pressure) - Glomerular Oncotic Pressure

30
Q

How can GFR be manipulated?

A

Increase GFR by:
CEDA
1. Constriction of efferent arteriole
2. Dilation of afferent arteriole
Decrease GFR by:
CADE
1. Constriction of afferent arteriole
2. Dilation of efferent arteriole

31
Q

Relationship between blood pressure, GFR, and reabsorption

A

BP and GFR are directly proportional: if BP increases, GFR increases
BP&GFR are inversely proportional to reabsorption in the kidneys: If BP is high –> GFR is high –> reabsorption decreases

*As filtration increases, filtrate passes by more quickly in the tubule, which means solutes have less time to be reabsorbed (decreasing reabsorption) –> leads to increased urinary volume

32
Q

What are the three layers of the skin?

A

Hypodermis (subcutaneous) layer, dermis, and epidermis

33
Q

The epidermis is is subdivided into five layers:

A

Mnemonic: Come, Let’s Get Sun Burned

Stratum corneum
Stratum lucidum
Stratum granulosum
Stratum spinosum
Stratum basale

34
Q

What are the main cells of the epidermis (of which the skin is made of)?

A

Keratinocytes

35
Q

What are calluses?

A

Areas of excessive deposition of keratin due to repeated strain and friction in the area

36
Q

Function of the stratum basale

A

Deepest layer of the epidermis which houses stem cells responsible for creating keratinocytes and neural crest cells responsible for creating melanocytes.

37
Q

What is the function of melanocytes?

A

They are cells which produce melanin which is a pigment that serves to protect the skin from DNA damage caused by UV radiation.
All people have melanocytes, but the degree of their activity varies (how much melanin is actually produced).

38
Q

What are the defining features of the stratum spinosum?

A

This is where the keratinocytes become connected physically to one another. This is also the site of Langerhans cells which are macrophage immune cells that present antigens to T cells to activate the immune system.

39
Q

What is the defining feature of the stratum granulosum?

A

This is the epidermal layer where the keratinocytes start to come up and die; they lose their nuclei.

40
Q

What is the defining feature of the stratum lucidum?

A

It is the epidermal layer which is only present in areas of the body with thick hairless skin, such as the soles of our feet or palms.

41
Q

What is the defining feature of the stratum corneum?

A

It is the upper most epidermal layer which contains many dead flattened keratinocytes, which form a protective barrier known as our skin.

42
Q

What is the hypodermis?

A

It is the layer of connective tissue below the dermis that connects the skin to the rest of the body. It contains mostly fat and fibrous tissue.

43
Q

Most sensory receptors are located in what layer of the skin?

A

Dermis

44
Q

What is the name of the sensory receptors that are responsible for light touch?

A

Meissner’s corpuscle

45
Q

What are the sensory receptors responsible for detecting stretch?

A

Ruffini endings
(Ruffini is an Italian guy who STRETCHES his homemade pasta)

46
Q

Merkel’s discs are responsible for detecting…

A

Deep pressure and texture sensation

47
Q

Which sensory receptor detects deep pressure and vibration?

A

Pacinian corpuscles
(Famous violinist Paganini used vibrato on the violin which produces a vibrating noise in different notes )

48
Q

Thermoregulation is achieved by different mechanisms such as…

A

Sweating, piloerection, vasodilation, vasoconstriction, and shivering

49
Q

What part of the nervous system controls sweating?

A

The sympathetic division of the autonomic nervous system

50
Q

Postganglionic sympathetic neurons which innervate the sweat glands are (cholinergic/adrenergic).

A

Cholinergic meaning they release acetylcholine.
(Keep in mind usually all postganglionic sympathetic neurons are noradrenergic except those innervating sweat glands)

51
Q

How does sweating allow the body to cool down?

A

As water molecules are released from the body this allows them to undergo a phase change through evaporation thus at the same time allowing the skin to give off heat.

52
Q

What kinds of things are located in the dermis layer of skin?

A

Blood vessels, hair follicles, sebaceous glands (oil), sudoriferous glands (sweat), sensory receptors, and nerve endings

53
Q

Blood vessels near the skin ______ to release heat and _______ to retain heat.

A

dilate, constrict

54
Q

How do we get “goosebumps” and why?

A

Goosebumps are caused by the contraction of arrector pili muscles which causes the erection of hair follicles that traps a layer air next to the skin

55
Q

Which factor determines if cells in parts of the body are endocrine vs. exocrine glands?

A

Exocrine glands include cells which secrete a substance (such as a hormone) into an external environment. This substance can either be secreted directly onto the epithelial surface or through a duct/tract that is eventually secreted outside of the body.

56
Q

What regions of the body contain exocrine glands?

A

Digestive tract, respiratory tract, stomach, nasal passageways, skin, pancreas, breasts, eyes, liver

57
Q

As the filtrate goes down the descending limb it has a higher/lower osmolarity than the medulla.

A

Higher because water leaves the tubule as you go down the descending limb

58
Q

As the filtrate goes up the ascending limb the osmolarity in the tubule (increases/decreases).

A

Decreases because Na actively leaves the tubule to be reabsorbed.

59
Q

Angiotensin II, a hormone secreted by the liver has two mechanisms by which it controls blood pressure. What are they?

A
  1. Immediate function is vasoconstriction to increase BP.
  2. More long term function is to stimulate production/release of aldosterone to increase blood pressure and blood volume.
60
Q

All of the glands of the body except ____________ are innervated by the parasympathetic nervous system.

A

Sweat glands

Malika Biology MCAT (12 decks)

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