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MCAT Biochem > Renal and Digestive System > Flashcards

Renal and Digestive System Flashcards

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1
Q

Colon Function

A

Eliminates solid waste, material that was eaten but not absorbed

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2
Q

Liver function

A

Eliminates hydrophobic waste
Material that was eaten and absorbed in the blood, but too hydrophobic to dissolve in the plasma
- Alcohol, acetaminophen

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3
Q

Kidney Functions

A

Eliminates hydrophilic waste
Material that was eaten, absorbed in the blood, and dissolved in the plasma

  1. Regulates blood pressure
  2. Regulates ion balance
  3. Regulates water balance
  4. Regulates pH
  5. Secretes EPO (Erythropoietin), EPO stimulates red blood cell formation
  6. Activates vitamin D
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4
Q

What are the kidneys sensitive to and what is their response?

A

The functions of the kidney require active transport. Active transport required ATP, which requires oxygen.
Thus, the kidneys are sensitive to drops in oxygen. If oxygen levels drop, the kidneys secrete EPO to stimulate RBC formation to supply oxygen to the system.

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5
Q

Internal Urinary sphincter

A

Made of smooth muscle
Under involuntary control
If relaxed, urine will flow to the external urinary sphincter
- This is where we feel the urge to urinate

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6
Q

External urinary sphincter

A

Skeletal muscle

Under voluntary control

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7
Q

Bladder function

A

Urine storage

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8
Q

Ureter function

A

Tube that drains from the kidney to the bladder

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9
Q

Flow from the kidney

A

Kidney -> ureter -> bladder -> internal sphincter -> external sphincter -> out through the urethra

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10
Q

Nephron

A

Functional unit of the kidney

All modifications to urine happen at the nephron

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11
Q

3 processes the of the nephron to produce urine

A
  1. Filtration - moves a substance across a membrane using pressure
    (Moves blood plasma across capillary walls utilizing blood pressure)
  2. Reabsorption - move a substance from the filtrate into the blood.
  3. Secretion - moves a substance from the blood to the filtrate
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12
Q

What is always secreted?

A

Drugs, toxins, and creatinine

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13
Q

What is always reabsorbed?

A

Glucose, amino acids, and water

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14
Q

Ions

A

Can be secreted or absorbed
Typically reabsorb sodium and bicarbonate
Typically secrete potassium and H+

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15
Q

Creatinine Function

A

Creatinine is a metabolic product of muscle function, which is constantly occurring in the body
Is a measure of kidney function.

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16
Q

Glomulerus Function

A

Filtration

Can’t filter proteins

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17
Q

Afferent vs Efferent arteriole

A

Afferent approaches the glomerulus
Efferent exits the glomerulus (Is very high in protein because they can’t be filtered)
We can dilate the afferent while constricting the efferent, increasing blood flow in and increasing volume and pressure in the capillary bed.

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18
Q

Proximal tubule function

A

Most reabsorption and secretion occurs here
Most water, glucose, and amino acids are reabsorbed here
Roughly isotonic to plasma at this point

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19
Q

Loop of Henle function

A

Sets up the concentration gradient in the medulla

Osmolarity increases the deeper in the medulla you go (Increased salt concentration)

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20
Q

Descending Loop of Henle

A

Permeable to water, but impermeable to salt (Loses water)

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21
Q

Ascending Loop of Henle

A

Permeable to salt, but impermeable to water
Sodium is actively transported at the top of the loop into the surrounding tissue, drawing water out of the descending loop
Sodium is passively transported out at the bottom of the loop

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22
Q

Distal Tubule Function

A

Specialized reabsorption and secretion

Sodium reabsorption here is regulated by aldosterone

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23
Q

Calcium reabsorption is regulated by what two hormones

A

Calcitonin and Parathyroid hormone

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24
Q

Collecting Duct Function

A

Regulates water reabsorption

Do we want to retain or pee it out

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25
Q

ADH Function

A

Anti-diuretic hormone
If ADH is present, the walls of the collecting duct are permeable to water and water will be reabsorbed
If ADH isn’t present, the walls of the collecting duct aren’t permeable and water will be subsequently urinated

26
Q

Dehydration/Hydration and ADH

A

If dehydrated, increase ADH to promote water reabsorption

Alcohol and caffeine are diuretics - they inhibit ADH, forcing you to urinate even if you’re dehydrated

27
Q

Renin-Angiotensin system

A

How BP is regulated by the kidney

If blood pressure falls, the kidney secretes renin
Renin is an enzyme that converts inactive angiotensinogen into angiotensin 1 (active)
Angiotensin 1 is converted to angiotensin 2 by ACE (angiotensin converting enzyme)
Angiotensin 2 causes systemic vasoconstriction and increased aldosterone release

28
Q

Angiotensin 2 Functions

A

When active, it causes systemic vasoconstriction (which increases blood pressure) and releases aldosterone
Aldosterone increases sodium reabsorption by the distal tubule
More sodium = increased osmolarity, triggering the release of ADH
ADH causes increased water reabsorption, which increases blood volume, and increases blood pressure

29
Q

Juxtaglomerular Apparatus

A

The contact point between the afferent arteriole and the distal tubule

30
Q

The afferent arteriole is what kind of receptor, and what does it do

A

Baroreceptors, which monitor blood pressure

If blood pressure falls, the baroreceptors release renin

31
Q

The distule tubule contains what kind of receptors and what is their function

A

Chemoreceptors, detecting changes in osmolarity
Decreased osmolarity:
1. Stimulates afferent arteriole to release renin
2. Directly dilates the afferent arteriole (Increasing volume and BP in the capillaries)

32
Q

What happens when blood pressure is high?

A

The atria detect the heart stretch
The right atrium releases ANP (Atrial Natriuretic Peptide)
ANP is a vasodilator and inhibits the release of renin and aldosterone

33
Q

How is pH regulated by the kidney?

A

Renal regulation of blood pH is slow

Carbonic anhydrase is an enzyme that increases the rate of carbonic acid formation, which dissociates into bicarbonate

34
Q

Bicarbonate buffer system

A

CO2 + H2O H2CO3 H+ + HCO3-

35
Q

What happens when blood pH is too acidic/basic?

A

Acidic: Increase bicarbonate reabsorption and increase H+ secretion
Basic - Decrease bicarbonate reabsorption and decrease H+ secretion

36
Q

What is the Alimentary Canal?

A

Muscular tube, mouth to anus

37
Q

What are the accessory organs?

A

Organs with a digestive role, but are not part of the Alimentary Canal
Liver, Gallbladder, Pancreas, and the Salivary glands

38
Q

Liver digestive function

A

Produces bile, which breaks down fats for easier digestion

39
Q

Bile function

A

Bile is an amphipathic molecule that breaks down fats for easier digestion

40
Q

Gallblader Function

A

Stores and concentrates the bile produced by the liver

No gallbladder = can’t eat a lot of fat because it won’t be broken down as effectively

41
Q

Pancreas Functions

A

Secretes insulin and glucagon
Major source of digestive enzymes (Proteases, lipases, amylases, and nucleases)
Releases bicarbonate to optimize the function of its enzymes

42
Q

Amylase function

A

Breaks down starch

43
Q

Nuclease function

A

Breaks down nucleic acids

44
Q

Alimentary Canal wall components

A

Mucosa - epithelial tissue attached to the lumen
Submucosa - connective tissue that contains the blood vessels and nerves that supply the digestive tract
Circular muscle - runs around the circumference of the tube (composes sphincters)
Longitudinal muscle - runs along the length of the tube
Serosa - connective tissue that forms the perineal membrane

45
Q

Peristalsis

A

Involuntary contraction and relaxation of circular and longitudinal muscles that work together to move food down the digestive tract

46
Q

Mouth (Function, structure, exocrine and endocrine functions)

A

Functions - grind food, moisten food, and begin starch digestion
Structure - teeth, tongue, and salivary glands
Exocrine - secretes saliva (mostly water, mucus, and enzymes), lysozymes that kill bacteria, and amylase
No endocrine function

47
Q

Esophagus (Function, structure, exocrine and endocrine functions)

A

Function - tube that brings food down to the stomach
Structure - starts as skeletal muscle and transitions to smooth muscle
Cardiac sphincter is at the bottom of the esophagus to prevent stomach contents from refluxing back up
No exocrine or endocrine function

48
Q

Stomach (Function, structure, exocrine and endocrine functions)

A

Very limited digestion and absorption - main job is to serve as a storage tank for food
Composed of gastric glands and the pyloric sphincter
Exocrine - mucous cells, parietal cells, and chief cells
Endocrine - secretes Gastrin, which is produced by G cells

49
Q

Gastric glands

A

In the stomach
Mucous cells - secrete mucous
Parietal cells - secrete HCl
Chief cells - secrete pepsinogen (innate immunity)

50
Q

Pepsinogen

A

Produced by the chief cells within the stomach. Initially inactive, as it moves up the pit the parietal cells dump HCl on them which activate them.
Are proteases that provide innate immunity by reducing infection

51
Q

Pyloric sphincter

A

Sphincter of the stomach that regulates entry into the small intestine

52
Q

Gastrin

A

Produced by G-cells in the stomach
Gastrin increases the productivity of the gastric glands
Operate under negative feedback by pH
Eat a meal, increasing gastrin secretion, stimulating the gastric glands, lowering the pH, inhibiting further gastrin release

53
Q

Small Intestine (Function, structure, exocrine and endocrine functions)

A

Where most digestion/absorption is performed

Duodenum (5%) Jejunum (40%) Ileum (55%)

See a huge increase in surface area to increase digestion via mucosa, plicae, villus, microvilli (brush border)

Produces enterokinase (Enteropeptidase) and brush border enzymes (Disaccharides, dipeptidases)

Endocrine - Produces enterogastrone, CCK, and Secretin

54
Q

Enterokinase Function

A

An enzyme of the small intestine

Activates trypsinogen, a pancreatic protease that sets off a chain of enzyme activation

55
Q

Brush Border enzymes

A

Enzymes of the small intestine
The last step in digestion
Disaccharidases and dipeptidases that break molecules into monomers

56
Q

Trypsinogen

A

Activated by enterokinase

A pancreatic protease that cleaves enzymes, setting off a chain of enzyme activation

57
Q

Enterogastrone

A

Produced by the small intestine

Released when food is in the intestine, reduces stomach motility

58
Q

Secretin

A

Produced by the small intestin

Stimulates the pancreas to release bicarbonate and is triggered by low pH

59
Q

CCK (Cholecystokinin)

A

Produced by the small intestine
Increases bile release from the liver and gallbladder
Triggered by fats and proteins

60
Q

Large Intestine (function, structures, endocrine and exocrine function)

A

Function - reabsorbs water and stores feces (No digestion)
Contain colonic bacteria that secrete vitamin K and reduce the growth of pathogens
Ileocecal valve and internal/external anal sphincters
No exocrine or endocrine function

61
Q

Ileocecal valve

A

Found between the small and large intestine

Is usually closed, relaxes when we eat a big meal to clear room in the small intestine. Initiates defecation reflex

MCAT Biochem (2 decks)

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