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MCAT BIOLOGY FLASHCARDS > MCAT BIO CH. 10 PART 1 > Flashcards

MCAT BIO CH. 10 PART 1 Flashcards

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1
Q

What are the organs of the excretory system?

A
  1. Liver
  2. Colon
  3. Skin
  4. Kidneys
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2
Q

What is the liver responsible for?

A

Excreting many wastes by chemically modifying them and releasing them into bile

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3
Q

What type of products does the liver deal?

A

Hydrophobic or large waste products that cannot be filtered out by kidney

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4
Q

What can the kidney dissolve?

A

Eliminate small hydrophils dissolved in plasma

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5
Q

Which organ synthesizes urea?

A

The liver

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6
Q

Where does the liver excrete urea?

A

Into the bloodstream

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7
Q

What is urea?

A

A carrier of excess nitrogen resulting from protein breakdown

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8
Q

Why must free nitrogen be converted into urea?

A

Because free ammonia is toxic

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9
Q

What is the purpose of the large intestine?

A

Reabsorb water and ions from feces

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10
Q

What does the skin produce and how is it an excretory organ?

A

Produces sweat; excretory role is secondary as its used for temperature level

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11
Q

What is the purpose of kidneys?

A

Excretion of hydrophilic wastes

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12
Q

Which substances must be excreted in the urine?

A

Urea, sodium, bicarbonate and water

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13
Q

What is the role of the kidney based on its excretion?

A

Homeostasis

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14
Q

What are the excretory and homeostatic roles of the kidney?

A
  1. Excretion of hydrophilic wastes
  2. Maintenance of constant solute concentration and constant pH
  3. Maintenance of constant fluid volume
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15
Q

What is the first process of the kidney in keeping homeostasis?

A

Filtration

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16
Q

What is the filtration of the kidney?

A

Passage of pressurized mood over a filter

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17
Q

What does the kidney filter?

A

Cells and proteins remain in the blood; water and small molecules are squeezed out into the renal tubule

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18
Q

What is the fluid in the renal tubule of the filtration kidney called?

A

Filtrate

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19
Q

What is the second process of the kidney in keeping homeostasis?

A

Selective reabsorption

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20
Q

What happens during selective reabsorption of kidney homeostasis?

A

Take back useful items and leave wastes and some water in the tubule

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21
Q

What is the third process of the kidney in keeping homeostasis?

A

Secretion

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22
Q

What is secretion based on kidney homeostasis?

A

Involves addition of substances to the filtrate

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23
Q

What is the last step to urine formation?

A

Concentration and dilution

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24
Q

What is concentration and dilution based on urine formation?

A

Selective reabsorption of water

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25
Q

How does the blood enter the kidney?

A

Fro a large renal artery directly backed of the low protein of the abdominal aorta

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26
Q

How is purified blood return into the body from the kidney?

A

By the large renal vein which empties into the inferior vena cava

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27
Q

Through what does urine live each kidney and what does it empty in?

A

Urine leaves each kidney in a ureter and empties into the urinary bladder

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28
Q

What happens when the bladder becomes full?

A

Signals of urgency are sent to the brain

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29
Q

What are the two sphincters controlling the release of urine?

A

Internal sphincter and external sphincter

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30
Q

What is the internal sphincter based on bladder control, made of?

A

Made of smooth involuntary muscle

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31
Q

What is the external sphincter based on bladder control, made of?

A

Made of skeletal voluntary muscle

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32
Q

What is the name of the outside layer of the kidney? What about right underneath these layers?

A
  1. Cortex

2. Outer medulla and inner medulla

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33
Q

Why is there striation within the medulla pyramids?

A

Due to presence of many collecting duct

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34
Q

What are collecting ducts based on the kidney?

A

Urine empties from the collecting ducts and leaves the medulla at the tip of a pyramid known as a papilla

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35
Q

What does the papilla of the kidney empties?

A

Calyx

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36
Q

What does the calyx of the kidney converge into?

A

Renal pelvis

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37
Q

What does the renal pelvis of the kidney empties into?

A

Ureter

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38
Q

What is the functional unit of the kidney?

A

The nephron

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39
Q

What are the two components that consist of the nephron?

A
  1. Capsule

2. Renal tubule

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40
Q

What is the capsule used as?

A

Rounded region surrounding the capillaries where filtration takes place

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41
Q

Where does the renal tubule of the kidney receive filtrate from? Where does it empty?

A

Receives from the capillaries in the capsule and empties into a collecting duct

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42
Q

Why do blood vessels surround the nephron?

A

To carry filtered blood and reabsorbed substances away from the tubule

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43
Q

What are the two important arterioles for filtration of blood through the kidney?

A

Afferent arteriole and efferent arteriole

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44
Q

What happens when the blood flows through the renal artery (it goes into which vessel and then what)?

A

Goes through afferent arteriole, glomerulus and then efferent arteriole

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45
Q

What is the glomerulus?

A

Ball of capillaries

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46
Q

What happens to the fluid in the glomerulus?

A

Efferent squeezes, resulting in high pressure, causing fluid to leak out of the glomerular capillaries

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47
Q

When the fluid leaks from the glomerular capillaries, what does it go through?

A

Passes through the glomerular basement membrane and enters the the Bowman’s capsule

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48
Q

During selective reabsorption, the filtrate in the tubule consists of what?

A

Water and small hydrophilic molecules such as sugars, amino acids and urea

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49
Q

What happens to substances that are in the tubule that must be returned to the blood stream during selective reabsorption?

A

Extracted from the tubule, often via active transport, and picked up by peritubular capillaries

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50
Q

What is the proximal convoluted tubule?

A

The tubule nearest to Bowman’s capsule where a lot of the reabsorption occurs

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51
Q

Along with solute movement in the proximal convoluted tubule, what else follow?

A

Water; a lot of water reabsorption occurs in that region

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52
Q

What is the two types of convoluted tubules based on selective reabsorption?

A
  1. Proximal convoluted tubule

2. Distal convoluted tubule

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53
Q

What is secretion based on kidney filtration?

A

Movement of substances into the filtrate usually via active transport

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54
Q

Why is secretion considered a back-up plan?

A

Not everything that needs to be removed from the blood gets filtered out at the glomerulus

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55
Q

Where does most of the secretion occur?

A

In the DCT and collecting duct

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56
Q

Where does the adjutants are made to the urine volume and osmolarity before being discarded in the ureter?

A

In the distal nephron

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57
Q

What does the distal nephron section include?

A

DCT and collecting duct

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58
Q

What is the distal nephron behavior controlled by?

A

ADH and Aldosterone

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59
Q

How is the volume of fluid and the solute concentration when the body is dehydrated?

A

Volume of fluid in blood is low and the solute concentration is high

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60
Q

What happens when the body is dehydrated; what hormone is released to assure you maintain enough water?

A

Antidiuretic hormone; vasopressin or ADH

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61
Q

What released ADH?

A

Posterior pituitary

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62
Q

What is diuresis?

A

Water loss in urine

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63
Q

What does ADH prevent?

A

Diuresis

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64
Q

How does ADH prevent diuresis?

A

Increases water reabsorption in the distal nephron

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65
Q

How does the ADH increase water reabsorption in the distal nephron?

A

Makes it permeable to water

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66
Q

What happens if there isn’t any ADH; how does it prevent water reabsorption in the distal nephron?

A

Without ADH, it’s impermeable to water

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67
Q

What happens when water is reabsorbed in the filtrate by the distal nephron?

A

Water flows out of the filtrate into the tissue of the kidney, picked up by the peritubular capillaries and returned to the blood

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68
Q

Why does water tend to flow out of the tubule and into the tissue of the kidney when ADH is present?

A

Because renal medulla has a very high osmolarity which causes water to exit the tubule by osmosis

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69
Q

Why does alcohol cause people to diurese?

A

It inhibits ADH secretion by the posterior pituitary

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70
Q

When is aldosterone released?

A

When the blood pressure is low

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71
Q

What released aldosterone hormone?

A

Adrenal cortex

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72
Q

What does aldosterone do?

A

Increases reabsorption of Na+ by the distal nephron

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73
Q

Why does increasing the absorption of sodium by the distal nephron help the blood pressure?

A

Increased plasma osmolarity, leading to increased thirst and water retention which raises the blood pressure

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74
Q

ADH and Aldosterone work together to:…..?

A

Increase blood pressure

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75
Q

Where are the bowman’s capsule and proximal convoluted tubule located?

A

In the renal cortex, the outer layer of the kidney

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76
Q

Where does the proximal convoluted tubule empty in?

A

The loop of Henle

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77
Q

What is the loop of Henle?

A

Long loop that digs down into the renal medulla

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78
Q

What is the renal medulla?

A

The inner part of the kidney

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79
Q

What are the two parts to the loop of Henle?

A

Descending and ascending limb of the loop of Henle

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80
Q

The descending limb of the loop of Henle is the part that….?

A

Heads into the medulla

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81
Q

The ascending limp of the loop of Henle is the part that….?

A

Heads back out towards the cortex

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82
Q

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

A

Thin descending limb and thick and thick parts to the ascending limb

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83
Q

What is the structural difference between thick and thin walls of the limbs of the loop of Henle?

A

Thin are squamous epithelial cells, not very metabolically active; thick means cuboidal which are large thick cells that are busily performing active transport

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84
Q

What happens when the fluid further continues down the loop of Henle?

A

Becomes the distal convoluted tubule

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85
Q

What does the DCT dump into?

A

Collecting duct

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86
Q

What example has countercurrent multiplier?

A

Loop of Henle

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87
Q

Why is the loop of Henley considered a countercurrent multiplier?

A

Ascending and descending limbs go in opposite directions and have different permeabilities

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88
Q

What is the permeability of the descending limb of the loop of Henle?

A

Permeable to water but not to ions

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89
Q

What happens when water goes through the descending limb of the loop of Henle?

A

Water exists the descending limb and flows into the high-osmolarity medullary interstitium

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90
Q

What happens to the filtrate when the water escapes the descending limb of Henle?

A

Becomes concentrated

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91
Q

What is the permeability of the ascending limb of the loop of Henle?

A

Not permeable to water but passively loses ions from the high-osmolarity filtrate into the renal medullary interstitium

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92
Q

What is the purpose of the thick ascending limb in the loop of Henle?

A

Actively transport salt out of the filtrate into the medullary interstitium and the medullary interstitium becomes very salty

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93
Q

Why is it important that the medullary interstitium becomes very salty from the ascending limb losing ions?

A

Medulla will suck water out of the collecting duct by osmosis whenever it is permeable to water

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94
Q

What is the vasa recta connected to?

A

Branches of efferent arterioles

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95
Q

What does the loop of the vasa recta help with?

A

Helps to maintain the high concentration of salt in the medulla

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96
Q

Where is the ascending portion of the vasa recta?

A

Near the descending limb of the loop of Henle; carry of the water that leaves the descending limb

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97
Q

What does the vasa recta do to the water it absorbs?

A

Return to the bloodstream any water that is reabsorbed from the filtrate

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98
Q

Which part of the kidney undergoes countercurrent exchange?

A

Vasa recta

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99
Q

How is the vasa recta an example of countercurrent exchange?

A

The blood in the vasa recta moves in the opposite direction of the filtrate in the nephron `

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100
Q

What is the glomerular filtration rate dependent on directly? What organ assists with that?

A

Pressure; the kidney has built-in mechanism to help regulate systemic and local (glomerular) blood pressure

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101
Q

What is the juxtaglomerular apparatus?

A

A specialized contact point between the afferent arteriole and distal tubule

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102
Q

At the juxtaglomerular apparatus, what are the cells called?

A

Juxtaglomerular cells

103
Q

What are the names of the cells in the distal tube called?

A

Macula densa

104
Q

What is the purpose of the juxtaglomerular cells?

A

Are baroreceptors that monitor systemic blood pressure

105
Q

What happens when there is a decrease in blood pressure?

A

The JG cells secrete an enzyme called renin into the bloodstream

106
Q

What does the enzyme renin do, based on assistance with blood pressure?

A

Catalyzes conversion of angiotensinogen into angiotensin I

107
Q

What happens to angiotensinogen I; does it maintain its same form during assistance with blood pressure?

A

Converted into angiotensin II by angiotensin-converting enzyme (ACE) in the lungs

108
Q

What is angiotensin II and why does it help with low blood pressure?

A

Powerful vasoconstrictor that immediately raises blood pressure

109
Q

What other hormone can angiotensin II trigger and how?

A

Stimulates the release of aldosterone which helps raise blood pressure by increasing sodium retention

110
Q

What are the purpose of the macula densa cells in the distal tube?

A

Chemoreceptors and monitor filtrate osmolarity in the distal tubule

111
Q

What happens when filtrate osmolarity decreases based on renal regulation?

A

The macula dense cells stimulate JG cells to release renn

112
Q

What effects can macula densa cells have on vessels itself?

A

Causes a direct dilation of the afferent arteriole, increasing blood flow to the glomerulus

113
Q

What organ is essential for maintenance of constant blood pH, based on renal regulation?

A

The kidney

114
Q

How does the kidney regulate blood pH?

A
  1. pH too high - HCO3 is excreted in the urine

2. pH too low - H+ is excreted

115
Q

What enzyme is involved in the release of HCO3 and H+ based on kidney regulating blood pH?

A

Carbonic anhydrase

116
Q

Where is carbonic anhydrase found?

A

In epithelial cells throughout the nephron, except squamous cells

117
Q

What does carbonic anhydrase convert?

A

Conversion of CO2 into carbonic acid H2CO3 which dissociates into bicarbonate plus a proton

118
Q

Based on renal regulation, which molecule is usually excreted and absorbed by the kidney?

A

Protons are secreted and bicarbonate are reabsorbed, amounts adjusted to adjust pH

119
Q

What is the problem with renal regulation of pH?

A

Slow

120
Q

What organ is important in blood pH regulation and how?

A

Lungs; exhaling excess CO2, lung removes an acid H2CO3 from the blood and raises the PH

121
Q

What is aldosterone based on its molecule? (Not a peptide hormone but….?)

A

A steroid

122
Q

What is the hormone made by the kidney?

A

Erythrpoietin EPO

123
Q

From where is aldosterone released?

A

Adrenal cortex

124
Q

From where is ADH released?

A

Posterior pituitary

125
Q

From where is calcitonin released?

A

C cells

126
Q

From where is parathyroid hormone released?

A

Parathyroid

127
Q

From where is EP released?

A

Kidney - erythropoietin

128
Q

What does aldosterone do and how?

A

Increase blood pressure; increased sodium reabsorption and K+ secretion

129
Q

What does ADH do?

A

Increased water reabsorption and plasma volume

130
Q

How does ADH increase water reabsorption and plasma volume?

A

Increases permeability of water in epithelial cells of the distal nephron; water flows out of filtrate and into medley interstitium - the vasa recta returns this water to the blood stream

131
Q

What does calcitonin do and how?

A

Causes Ca2+ to be removed from he blood by deposition in the bone, reduced absorption by the gut or excretion in the urine when Ca2+ serum is too high

132
Q

What does parathyroid do and how?

A

Opposite of that of calcitonin, increased Ca2+ serum

133
Q

What does kidney do and how?

A

Increases synthesis of red blood cells in the bone marrow when blood oxygen content falls

134
Q

What is the role of vitamins in food?

A

Serve a catalytic role as enemy cofactors or prosthetic groups

135
Q

What is the secondary function from the digestive system?

A

Protection from disease

136
Q

Where is digestion accomplished?

A

Gastrointestinal tract (GI/ Digestive tract, alimentary canal or gut

137
Q

The GI tract muscular tube from the mouth to the anus is derived from what?

A

Gastrulation during embryogenesis

138
Q

What is the inside of the gut called?

A

GI lumen

139
Q

What is the lining of the GI lumen composed with?

A

Epithelial cells

140
Q

What are epithelial cells attached to?

A

Basement membrane

141
Q

What is the apical surface of the epithelial cells?

A

The surface of the epithelial cell which faces into the lumen

142
Q

What do the apical surface of epithelial cells have in the small intestine that increases surface area?

A

Microvilli

143
Q

How are apical surface of epithelial cells operated from extracellular environment?

A

Separated from the remainder of the cell surface by tight junctions

144
Q

What is the basolateral surface?

A

The side and bottom of an epithelial cell form, the surface opposite the lumen

145
Q

What is mostly responsible for the secretory activity of the GI tract?

A

Specialized epithelial cells

146
Q

What is the GI muscle known as and why?

A

Smooth muscle because of its smooth microscopic appearance

147
Q

Which organs have striated muscles?

A

Skeletal and cardiac muscle

148
Q

What are the names of the two layers of smooth muscle lining the gut?

A

The longitudinal layer and the circular layer

149
Q

What is the GI motility?

A

The rhythmic contraction of GI smooth muscle

150
Q

What does it mean when said that GI smooth muscle has automaticity?

A

It contracts periodically without external stimulation due to spontaneous depolarization

151
Q

What does it mean when said that GI smooth muscle has functional syncytium?

A

When one cell has an action potential and contracts, the impulse spreads to neighboring cells

152
Q

What does it mean when said that GI smooth muscle has an enteric nervous system?

A

The GI tract contains its own massive nervous system; controls GI motility

153
Q

How can GI motility be influenced?

A

Increased or decreased by hormonal input

154
Q

How does the parasympathetic nervous system stimulate motility?

A

Cause sphincters to relax, allowing food to pass; sympathetic does the opposite

155
Q

What is the purpose of the GI motility?

A
  1. Mixing of food

2. Movement of food down the gut

156
Q

How is mixing of food accomplished by GI motility?

A

Disordered contractions of GI smooth muscles

157
Q

How is movement of food down the GI tract accomplished by GI motility?

A

Orderly form of contraction known as peristalsis

158
Q

What is peristalsis?

A

Orderly form of contraction

159
Q

How does peristalsis keep food separate?

A

Prevents food further down from mixing backwards

160
Q

After peristalsis, which muscle contracts? What happens?

A

Longitudinal muscle; shortening of the gut so that it is pulled over the food like sock - food moves forward

161
Q

What is a bolus?

A

Ball of food moving through the GI tract

162
Q

What is the enteric nervous system?

A

Branch of the autonomic nervous system that helps to control digestion via innervation of the GI tract, pancreas and gall bladder

163
Q

What does the enteric nervous system help with?

A

Regulate blood flow, gut movements, exchange of fluid from the gut to and from its lumen

164
Q

How would the parasympathetic and sympathetic nervous systems have effects on the enteric nervous system?

A

Para: Stimulates enteric branch and stimulate digestion
Symp: Inhibit enteric branch

165
Q

What are the networks of the enteric nervous system?

A

Myentric plexus and submucosal plexus

166
Q

Where is the myentric plexus located?

A

Between the circular and longitudinal muscle layers

167
Q

What does the myentric plexus help with?

A

Helps regulate gut motility

168
Q

Where is the submucosal plexus located?

A

Found in the submucosa

169
Q

What does the submucosal plexus help with?

A

Regulate enzyme secretion, blood flow and ion/water balance in the lumen

170
Q

What are the two types of GI secretion?

A
  1. Endocrine

2. Exocrine

171
Q

What is endocrine secretion?

A

Secrete products into ducts that drain into the GI lumen

172
Q

What is exocrine secretion?

A

Ductless glands and secretions are picked up by capillaries and enter bloodstream

173
Q

Where are acini located?

A

In the exocrine glands

174
Q

What are acini?

A

Specialized epithelial cells

175
Q

What is the purpose of acini cells?

A

Secrete products which pass into ducts

176
Q

What are the primary organs involved in exocrine secretion?

A

Liver, gallbladder, pancreas, epithelial cells

177
Q

How is the epithelial cells also included in exocrine secretion?

A

Release secretion directly into the gut lumen

178
Q

What are important examples of epithelial cells that are considered exocrine glands?

A
  1. Gastric glands in the soma

2. Goblet cells

179
Q

What is the role of goblet cells?

A

Secrete mucus

180
Q

What do the gastric glands secrete?

A

Acid and pepsinogen

181
Q

What is pepsinogen?

A

A protease zymogen

182
Q

Where can goblet cells be found?

A

Along the entire GI tract

183
Q

What is a mucus membrane?

A

Any body surface covered in mucus

184
Q

Whenever a meal is to be digested, it must be dissolved in…

A

Water

185
Q

What is endocrine secretion accomplished by?

A

Specialized organs (the pancreas) and by cells in the wall of the gut

186
Q

What are the two principal cell types in the pancreas?

A
  1. Pancreatic acinar cells (Exocrine cells)

2. Islets of Langerhans (Endocrine cells)

187
Q

What is the role of the mouth in the GI tract?

A

Fragmentation, lubrication and some enzymatic digestion

188
Q

How is fragmentation of the mouth accomplished?

A

Mastication (chewing), Incisors for cutting, capsids for tearing and molars for grinding

189
Q

What does saliva accomplish?

A

Some digestion and lubrication

190
Q

What does saliva contain that hydrolyzes starch and breaks it into fragments?

A

Salivary amylase (ptyalin)

191
Q

What is salivary amylase (ptyalin)?

A

Hydrolyzes starch and breaking it into fragments

192
Q

What is the smallest fragment yielded by salivary amylase?

A

Disaccharide; monosaccharide digestion occurs at intestinal brush border

193
Q

What is the purpose of lingual lipase in saliva?

A

Fat digestion

194
Q

Which enzyme assists with protein digestion in saliva?

A

Trick question: no protein digestion occurs in he mouth

195
Q

What is the purpose of lysozyme in saliva?

A

Attacking bacterial cell walls; mouth participates in innate immunity

196
Q

Why can’t carbohydrates be absorbed in the mouth?

A

Absorption requires special transmembrane transporters located on the intestinal brush border

197
Q

The pharynx contains the openings of two tubes; what are they?

A
  1. Trachea

2. Esophagus

198
Q

What is the structure of the trachea and what does it do?

A

Cartilage-lined tube at the front of the neck which conveys air to and from the lungs

199
Q

What is the structure of the esophagus and what does it do?

A

Muscular tube behind the trachea which conveys food and drink from the pharynx to the stomach

200
Q

What is the epiglottis?

A

Flat cartilaginous flap that excludes solids and liquids from entering the trachea

201
Q

What are the muscular rings regulating movement of food through the esophagus?

A
  1. Upper esophageal sphincter

2. Lower esophageal sphincter

202
Q

What is the cardiac sphincter also known as?

A

Lower esophageal sphincter

203
Q

What is the purpose of the lower esophageal sphincter?

A

Prevent reflux from he stomach into the esophagus

204
Q

What are the three purposes of the stomach?

A

Partial digestion of food, regulated release of food into the small intestine and destruction of microorganisms

205
Q

What is the acidity of the GI?

A

Gastric pH is about 2 due to the secretion of HCl by partial cells located in the gastric mucosa

206
Q

What are the effects of low gastric pH?

A
  1. Destruction of microorganism 2. Acid-catalyzed hydrolysis of many dietary proteins 3. Conversion of pepsinogen to pepsin
207
Q

What cells release pepsin?

A

Chief cells in the stomach wall

208
Q

What does pepsin catalyze?

A

Catalyzes proteolysis - protein breakdown

209
Q

Pepsin is secreted as what initially?

A

Pepsinogen, an inactive precursor that must be converted to the active form (pepsin)

210
Q

The inactive precursor form is known as…in the GI tract

A

Zymogen

211
Q

Most zymogens are activated by…?

A

Proteolysis - cleavage of protein at a specific site that activates it

212
Q

Pepsinogen is unique as it is….

A

Activated by acidic proteolysis instead of proteolytic cleavagge by another enzyme

213
Q

What is chyme?

A

Food mixed with gastric secretions

214
Q

What is the purpose of the pyloric sphincter?

A

Prevents the passage of food from the stomach into the duodenum

215
Q

When is the opening of the pyloric sphincter inhibited?

A

When the small intestine already has a large load of chyme

216
Q

What happens when there is excess acidity in the duodenum or stretching there?

A

Inhibits stomach emptying by causing pyloric sphincter to contract

217
Q

What is the main hormone responsible for the duodenum and stomach sphincters response?

A

Cholecystokinin

218
Q

What releases gastrin hormone?

A

G cells

219
Q

What does gastrin stimulate?

A

Stimulates acid and pepsin secretion and gastric motility

220
Q

What stimulates gastrin secretion?

A

Food in the stomach and by parasympathetic stimulation

221
Q

What molecule responds to stomach stretching and gastrin secretion?

A

histamine

222
Q

What does histamine do when the gastrin secretion is stimulated?

A

Binds to parietal cells to stimulate acid release

223
Q

What does the inhibition of histamine cause based on gastrin secretion?

A

Results in less gastric activity and allows for ulcers to heal

224
Q

What are the three parts of the small intestine?

A

Duodenum, jejunum and ileum

225
Q

What is the key feature that allows the small intestine to accomplish absorption?

A

Its large surface area

226
Q

What features allows for the small intestine to have such a large surface area?

A
  1. Length
  2. Villi
  3. Microvili
227
Q

What are villi?

A

Macroscopic projections in the wall of the small intestines

228
Q

What are microvilli?

A

Microvilli foldings of the cell membrane of individual intestinal epithelial cells

229
Q

What is the brush border?

A

The lumenal surface of the small intestine

230
Q

What important structures does the intestinal villus contain?

A
  1. Capillaries
  2. Laceals
  3. Peyer’s patches
231
Q

What does the capillaries do in the intestinal villus?

A

Absorb dietary monosaccharides and amino acids; merge to form the large hepatic portal vein

232
Q

What are lacteals?

A

Small lymphatic vessels

233
Q

What do lacteals do?

A

Absorb dietary fats

234
Q

What do the lacteals merge into?

A

Merge to form large lymphatic vessels

235
Q

What are Peyer’s patches and where are they located?

A

Collections of lymphocytes dotting the villi that monitor GI content and confer immunity to gut pathogens and toxins

236
Q

What are the two ducts that the duodenum empties into?

A
  1. Pancreatic duct

2. Common bile duct

237
Q

What is the pancreatic duct lead to?

A

Delivers the exocrine secretions of the pancreas (digestive enzymes and bicarbonate)

238
Q

What is the common bile duct deliver?

A

Bile

239
Q

What is bile?

A

Green fluid containing bile acids, made from cholesterol in the liver and are normally absorbed and recycled

240
Q

Where are bile stored?

A

Stored in the gallbladder until it is needed

241
Q

What is the function of bile?

A
  1. Excretion of waste products by the liver

2. Digestion of fats

242
Q

How does the bile duct and the pancreatic duct empty into the duodenum?

A

Via the same orifice, known as the sphincter of Oddi

243
Q

What does duodenal enterokinase cause?

A

Activates the pancreatic zymogen trypsinogen to trypsin

244
Q

What are brush border enzymes?

A

Does their work inside or on the surface of the brush border epithelial cells

245
Q

What is the role of the brush border enzymes?

A

To hydrolyze the smallest carbohydrates and proteins into monosaccharides and amino acids

246
Q

What are the main duodenal hormones?

A
  1. Cholecystokinin 2. Secretin 3. Enterogastrone
247
Q

When is cholecystokinin (CCK) secreted?

A

In response to fats in the duodenum

248
Q

What does the CCK cause cholecystokinin?

A

Causes the pancreas to secrete digestive enzymes, stimulates gallbladder contraction and decreases gastric motility

249
Q

How does the CCK stimulation helps with dealing with fats in the duodenum?

A

By digesting them and preventing further stomach emptying

250
Q

Duodenal hormones are released in response to what?

A

Response to acid in the duodenum and causes the pancreas to release large amounts of high pH aqueous buffers

251
Q

What pH aqueous buffer does the pancreas release in response to a stimulation of duodenal hormones?

A

HCO3- in water

252
Q

What does releasing HCO3 in water cause, based on pancreatic stimulation?

A

It neutralizes HCL released b the stomach

253
Q

How must the pH of the duodenal must be kept?

A

Must be kept neutral or even slightly basic for pancreatic digestive enzymes function

254
Q

What does enterogastrone do and what is it?

A

It is a duodenal hormone and it decreases stomach emptying

MCAT BIOLOGY FLASHCARDS (23 decks)

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