Lecture Exam 4 Flashcards
(245 cards)
1
Q
Nutrient undergo what before absorption?
A
digestion
2
Q
What two things aid digestion & absorption?
A
motility & secretion
3
Q
Where does absorption occur?
A
GI lumen
4
Q
Where does secretion occur?
A
endocrine & exocrine glands
5
Q
Path of the GI tract
A
- mouth
- pharynx
- esophagus
- stomach
- small intestine
- colon
- rectum
- anus
6
Q
What do hepatocytes in the liver secrete?
A
bile
7
Q
What are the 2 main functions of the liver?
A
remove old RBC’s (catalyzes Hb & generates bilirubin)
eliminates wastes & toxins
8
Q
What stores bile?
A
gallbladder
makes bile more concentrated & ejects it into the small intestine when needed
9
Q
What transports bile from the liver or gallbladder to the duodenum for digestion?
A
common bile duct
10
Q
The common bile duct joins with the pancreatic duct to form what?
A
ampulla of Vater
11
Q
What regulates flow from the pancreas & gallbladder to the duodenum?
A
sphincter of oddi
12
Q
Materials to make bile are taken up from blood in the what?
A
sinusoids
(similar to capillaries)
13
Q
What drain into the bile ducts?
A
canaliculi
14
Q
What do the bile ducts drain into?
A
common hepatic duct
15
Q
What are the most common forms of carbohydrates?
A
disaccharides or polysaccharides
16
Q
In order for carbohydrates to be absorbed, what form must they be in?
A
monosaccharide
(glucose, galactose, fructose)
17
Q
What digests starch (carbohydrates)?
A
amylase
(salivary or pancreatic)
18
Q
What are the 2 ways glucose & galactose (monosaccharides carbohydrates) are absorbed?
A
apical membrane: secondary active transport
basolateral membrane: facilitated diffusion
19
Q
How is fructose (monosaccharide carbohydrate) absorbed?
A
apical & basolateral membrane: facilitated diffusion
20
Q
In order for proteins (peptides) to be absorbed, what forms must they be in?
A
amino acids
dipeptides
tripeptides
21
Q
What proteases break down proteins (peptides) for digestion?
A
endopeptidases
exopeptidases
zymogens
22
Q
What is the FIRST site of protein digestion?
A
gastric pits in the stomach
23
Q
What enzyme does the stomach lumen secrete?
A
pepsin
24
Q
What does pepsin do?
A
breaks down peptides (proteins) into a form that the body can digest
25
What is pepsinogen?
the inactive form of pepsin
26
What cells in the stomach secrete pepsinogen?
chief cells
27
What cells in the stomach secrete acid in order to activate pepsinogen?
(acid activates pepsinogen into pepsin)
parietal cells
28
How are amino acids (form of proteins) absorbed?
apical membrane: facilitated diffusion or Na+ linked secondary active transport
basolateral membrane: facilitated diffusion
29
How are dipeptides & tripe-tides (form of proteins) absorbed?
apical membrane: active transport
basolateral membrane: broken down into amino acids & use facilitated diffusion
30
What is the most common form of lipids in a typical diet?
triglycerides
31
Typical diet contains how many g of lipids a day?
50 g of lipids a day
32
Typical diet contains how many g of proteins a day?
125 g of proteins a day
33
Typical diet contains how many g of carbohydrates a day?
500 g of carbs a day
34
What do lipases do?
break down triglycerides into monoglycerides
digest lipids
35
What are the 4 events that are ESSENTIAL for digestion & absorption of lipids?
1. secretion of bile & lipases
2. emulsification
3. enzymatic hydrolysis
4. micelle formation
36
What secretes lipases?
pancreas
37
What form should lipids be in for absorption?
micelle
38
What are the 3 functions of bile salts?
1. emulsify lipid
2. form micelle
3. remove waste products
39
What molecules within the fat droplet can lipases act on?
only molecules near the edge of fat droplet
40
Describe absorption of monoglycerides & fatty acids
1. micelle absorbed by simple diffusion
2. enter smooth ER, reform triglyceride
3. enter Golgi, packaged into chylomicrons
4. exocytosis
5. chylomicrons enter lymphatic system
41
How are vitamins A, D, E, & K (fat-soluble) absorbed?
vitamins dissolve in lipids & are absorbed with them
42
What do water-soluble vitamins need in order to be absorbed?
special transport proteins
43
Vitamin B12 must be bound to what in order to be absorbed?
an intrinsic factor
44
Where is sodium absorbed?
actively absorbed in jejunum, ileum, & colon
45
How is chloride absorbed?
passively follows sodium absorption
46
How is potassium absorbed?
passively absorbed
47
How are bicarbonate ions absorbed in the jejunum?
passively absorbed
48
In the ileum & colon, how are bicarbonate ions secreted?
secreted in exchange for chloride ions
49
Where is calcium absorbed?
actively absorbed in duodenum & jejunum
50
What does calcium require for absorption?
vitamin D
increases concentration of calcium-binding protein thus increases calcium absorption
51
Describe the process of calcium absorption
1. calcium binds to calcium-binding protein
2. transported into epithelial cells
3. transported out across basolateral membrane by Ca2+ pump
52
What secretes transferrin & where is it secreted?
secreted by enterocytes into lumen of the small intestine
53
What does transferrin do?
binds iron for transport through blood or into cells
54
Describe process of iron absorption
1. transferrin binds iron
2. complex binds receptor
3. taken into cells by receptor-mediated endocytosis
55
Iron is stored as what in enterocytes?
ferritin
56
Is water absorption active or passive?
passive
57
Where is water absorbed?
small intestine & colon
58
What does the hepatic artery do?
supplies O2 to the liver
59
What does the hepatic PORTAL vein do?
delivers nutrients from mesenteric veins to the liver
60
What does the hepatic vein do?
delivers nutrients from the liver to the heart
61
Where are GI hormones secreted?
from endocrine cells in the stomach & small intestine
62
Where is gastrin secreted & what does it do?
secreted in stomach
stimulates gastric secretions
63
Where is cholecystokinin (CCK) secreted & what does it do?
secreted in duodenum & jejunum
stimulates pancreatic enzyme secretion
stimulates bile secretion
stimulates gallbladder contraction
inhibits gastric secretion
64
Where is secretin secreted & what does it do?
secreted in duodenum & jejunum
stimulates pancreatic bicarbonate secretion
inhibits gastric secretion
65
Where is GIP secreted & what does it do?
secreted in duodenum & jejunum
stimulates insulin secretion by pancreas
inhibits gastric secretion
66
The hormone leptin is release from what?
adipose (fat) cells
67
When leptin (hormone) is released, what does it cause?
an increase in metabolism
a decrease in hunger
68
What hormone regulates food intake?
leptin
69
When orexigenic factors are released, what does it cause?
an increase in hunger
a decrease in metabolism
70
Satiety factors (fullness) causes the release of what?
alphaMSH
CART
71
Orexigenic factors (hunger) causes the release of what?
NPY
AgRP
ghrelin (produced in stomach when its empty)
72
What 2 enzymes are present in saliva?
salivary amylase (carb digestion)
lysozyme (anti-bacterial)
73
Characteristics of saliva
rich in bicarbonate ions
contains mucus
has enzymes present
74
What kind of saliva is produced under parasympathetic activation?
watery saliva
75
What kind of saliva is produced under sympathetic activation?
thick, protein-rich saliva
76
Where are gastric pits located?
in stomach lining
77
What is the first place of digestion for lipids & carbohydrates?
the mouth
78
Acid (HCl) & pepsinogen secretion in the stomach is regulated by what?
parasympathetic nervous system
79
What cephalic phase stimuli activate PNS & increase acid, pepsinogen, & gastrin secretion?
sight, smell or taste of food
chewing & swallowing
80
Where does cephalic phase stimuli originate?
in the head
requires CNS input
81
Where does gastric phase stimuli originate?
in stomach
82
Where does intestinal phase stimuli originate?
in small intestine
83
What gastric phase stimuli increase acid, pepsinogen, & gastrin secretion?
proteins & digestion products being in the stomach
dissension of stomach
84
What inhibits secretion in the gastric phase (stomach)?
exit of food
increased acidity in stomach
85
What portion of the pancreas produces pancreatic juice?
exocrine portion
86
What cells secrete pancreatic juice?
acinar & duct cells
87
What are the primary stimulants of pancreatic juice & bile secretion?
CCK & secretin
88
CCK stimulates what kind of cells?
acinar cells
to contract gallbladder & eject bile into duodenum
89
Secretin stimulates what kind of cells?
duct cells
to secrete more bile
90
What is the function of GI motility?
mix & propel GI tract contents
91
GI motility is due primarily to contractions of the what?
muscularis externa (outer muscle layers)
92
What does peristalsis do?
propels contents forwards
93
What does segmentation do?
mixes contents
94
Define segmentation
type of motility of the small intestine
alternating contractions between intestinal segments
95
Define bolus
chewed food + saliva
96
Process of swallowing reflex
1. bolus arrives at inferior esophagus
2. lower esophageal sphincter relaxes
3. bolus enters stomach
97
What initiates the swallowing reflex?
tongue moving bolus to pharynx
98
What factors affect the gastric emptying rate?
volume of chyme in the stomach
strength of gastric peristalsis
99
Secretion of what increases the force of gastric motility?
gastrin
100
Secretion of what decreases the force of gastric motility?
CCK
secretin
GIP
101
What cephalic phase (head) stimuli increase gastric motility?
anger, aggression
102
What cephalic phase (head) stimuli inhibit gastric motility?
pain, fear, depression
103
What gastric phase (stomach) stimuli increase gastric motility?
distension of stomach
104
What intestinal phase (intestine) stimuli inhibits gastric motility?
distension of duodenum
105
Gastric means...
of the stomach
106
What increases motility in the small intestine?
distension
107
Define intestino-intestinal reflex
injury or severe stress that inhibits intestinal contractions
108
Define oleo-gastric reflex
distension of ileum inhibits gastric motility
109
Define gastro-ileal reflex
presence of chyme in stomach increases motility in ileum
110
In the colon, what mixes contents?
haustrations
111
In the colon, what propels bolus towards rectum?
mass movement
112
Define colono-colonic reflex
distension of colon in one area causes relaxation of other areas
113
Define gastro-colic reflex
food in stomach increases colonic motility
114
What enzyme turns dextrins into glucose?
dextrinase
115
What enzyme turns polysaccharides into glucose?
glucoamylase
116
What enzyme turns sucrose into fructose & glucose?
sucrase
117
What enzyme turns lactose into galactose & glucose?
lactase
118
What enzyme turns maltose into 2 glucose?
maltase
119
What are the functions of the urinary system?
regulate plasma ionic composition
regulate plasma volume
regulate plasma osmolarity
regulate plasma pH
remove waste products from plasma
secrete erythropoietin & renin
activate vitamin D3 & calcitrol
120
What is the functional unit of the kidney?
nephron
121
What 2 things make up the nephron?
renal corpuscle & renal tubules
122
What 2 things make up the renal corpuscle?
glomerulus
glomerular (Bowmans) capsule
123
What is the glomerulus?
the capillary network for filtration
124
What does the glomerular (Bowmans) capsule do?
receives the filtrate & inflow to renal tubules
125
What are the 4 renal tubules?
proximal tubule
loop of henle
distal convoluted tubule
collecting duct
126
What 2 things make up the proximal tubule?
proximal convoluted tubule
proximal straight tubule
127
What 3 things make up the loop of henle?
descending limb
thin ascending limb
thick ascending limb
128
What makes up the distal convoluted tubule?
connecting tubule
129
What makes up the cortical nephron?
short loop of henle
130
What makes up the juxtamedullary nephron?
long loop of henle
131
What is responsible for the medullary osmotic gradient?
juxtamedullary nephron
132
What 2 nephron produce urine?
cortical & juxtamedullary nephron
133
Define filtration
flow of protein free plasma from glomerular capillaries into the bowmans capsule
134
Define reabsorption
selective transport of solute & water from renal tubule to interstitial fluid
135
Define secretion
selective transport of solute & water from interstitial fluid into renal tubule
136
What are the 3 barriers that filtrate must cross to enter the capsule?
capillary endothelial layer
surrounding epithelial layer (podocytes)
basement membrane
137
Define filtration fraction
fraction of blood filtered by the kidneys
GFR/renal plasma flow (found as %)
138
What starling forces FAVOR filtration?
glomerular capillary hydrostatic pressure (60 mmHg)
bowmans capsular oncotic pressure (0 mm Hg)
139
What starling forces OPPOSE filtration?
bowmans capsular hydrostatic pressure (15 mm Hg)
glomerular oncotic pressure (29 mm Hg)
140
The kidneys account for how much of cardiac output at rest?
20%
141
What is typical renal blood flow amount?
625 ml/min
142
What is typical GFR amount?
125 ml/min or 180 L/day
143
What is typical filtration rate amount?
3 L/day
144
Define filtered load
amount of a substance filtered by the kidneys
145
How many liters of urine is excreted per day?
1.5 L
146
What percentage of filtered fluid is reabsorbed?
99%
147
A small increase in GFR causes a large increase in what?
large increase in volume of fluid filtered & excreted
148
How does increasing mean arterial pressure affect GFR?
increase in MAP increases GFR
149
What happens during myogenic (intrinsic) regulation of GFR?
1. an increase in pressure activates mechanoreceptors
2. smooth muscle contracts
3. decrease in radius, increase in resistance
4. GFR increase
150
How does tubuloglomerular feedback affect intrinsic regulation of GFR?
macula densa cella secrete paracrine factors when flow increases
this causes smooth muscle to contract, increasing resistance, & increasing GFR
151
How does extrinsic control directly effect GFR?
decreases in BP decreased filtration pressure thus decreases GFR
152
How does extrinsic control indirectly affect GFR?
decreases in BP decreases blood volume, decreases MAP, decreases GFR
153
Where does the majority of solute reabsorption occur?
proximal tubule (PCT)
154
Where is reabsorption regulated?
distal tubule (DCT) & collecting ducts
155
Where is reabsorption unregulated?
proximal tubule (PCT)
156
What are the 2 barriers for reabsorption & secretion?
epithelial cells of renal tubules
endothelial cells of capillaries
157
How are solutes reabsorbed?
through active & passive reabsorption
158
How is water reabsorbed?
through osmosis, it follows the solute
159
Define transport maximum
the rate of transport when carriers are SATURATED
160
Define renal threshold
solute concentration in the plasma when carriers are saturated & the solute first appears in the urine
161
Why is there no glucose in the urine of healthy patients?
because 100% of glucose will be reabsorbed
162
Where is glucose freely filtered?
glomerulus
163
Where is glucose actively reabsorbed?
proximal tubules (unregulated)
164
During secretion what direction does solute move?
peritubular capillaries into tubules
165
What are secreted substances?
potassium
hydrogen
choline
creatinine
penicillin
166
Where does water conservation happen?
nephron loop
167
Why is the proximal tubule the mass reabsorber & nonregulated?
it has leaky junctions & a large surface area
168
Why do the distal tubule & collecting ducts have regulated reabsorption & secretion?
they have tight junctions that limit paracellular transport
169
Define excretion rate
amount of a solute exerted in the urine over time
170
What does the amount of solute excreted depend on?
filtered load
secretion rate
reabsorption rate
171
If the amount of solute excreted per minute is less than the filtered load, the solute was...
reabsorbed
172
If the amount of solute excreted per minute is greater than the filtered load, the solute was...
secreted
173
Define clearance
the volume of plasma from which a substance has been completely removed
174
What is the clearance of inulin?
125 mL/min
175
What does the clearance of inulin tell us?
tells us about the clearance of a substance that is freely filtered
this is the GFR value
176
What is at the clearance of glucose?
0 ml/min
177
What is renal blood flow value?
1136 ml/min
178
If clearance is GREATER than GFR, the solute was what?
solute was secreted
179
If clearance is LESS than GFR, the solute was what?
solute was reabsorbed
180
Where is urine formed?
in the renal tubules
181
What give control over urination?
sphincters
182
What is the flow of urine?
kidney, ureters, bladder
183
Define balance
solutes & water enter & exit plasma at the same rate
quantity stays the same
184
Define positive balance
solute or water ENTERS plasma faster than it exits
quantity INCREASES
185
Define negative balance
solute or water EXITS plasma faster than it enters
quantity decreases
186
Regulation of renal excretion depends on what 2 things?
the late distal tubule & collecting ducts
187
What cells in the late distal tubule & collecting ducts regulate balance of water & electrolytes?
principal cells
188
What cells in the late distal tubule & collecting ducts regulate acid-base balance?
intercalated cells
189
What establishes the medullary osmotic gradient?
water reabsorption in the proximal tubule
190
Define normovolemia
normal blood volume
191
Define hypervolemia
high blood volume
192
Define hypovolemia
low blood volume
193
What is the osmolarity of body fluids?
300 mOsm
194
What organ alters osmolarity of extracellular fluid?
kidneys
195
Is water reabsorption an active or passive process?
passive
happens through osmosis
196
Where is 70% of filtered water reabsorbed?
proximal tubules
197
Where is 20% of filtered water reabsorbed?
distal tubules
198
What hormones regulate water reabsorption in the distal tubules?
ADH (vasopressin) and aldosterone
199
When being reabsorbed, water follows what?
the solute
this is why it is passive
200
What establishes the osmotic gradient for water reabsorption?
Na+ being actively transported across the basolateral membrane
201
What establishes the medullary osmotic gradient?
the countercurrent multiplier
202
The medullary osmotic gradient is dependent on what?
the loop of henle
203
What part of the loop of henle is permeable to water & has NO transport of Na+, Cl-, or K+?
the descending loop
204
What part of the loop of henle is impermeable to water & has active transport of Na+, Cl-, and K+?
the ascending loop
205
Where is 10% of filtered water reabsorbed?
collecting ducts
206
What hormone regulates water reabsorption in the collecting ducts?
ADH
207
Water reabsorption in the distal tubule & collecting duct is dependent on what?
the medullary osmotic gradient that is established by the countercurrent multiplier & epithelium permeability to water
208
What is water permeability dependent on?
water channels (aquaporins)
209
Where is aquaporin 3 always present?
in basolateral membrane
210
Aquaporin 2 is present where & under what conditions?
present in apical membrane only when ADH is present in blood
211
How does ADH affect water reabsorption?
it promotes water reabsorption & reduces urine volume
it stimulates insertion of aquaporin 2
212
Where is ADH secreted from?
posterior pituitary (after stimulation from hypothalamus)
213
How does increased extracellular fluid osmolarity affect ADH?
it increases ADH
214
How does decreased baroreceptor activity affect ADH?
it increases ADH
215
If blood pressure drops below 80 mmHg what happens to GFR, water filtered, & water excretion?
decrease in GFR
decrease in amount of water filtered
decrease in water excretion
216
If blood pressure increases to more than 180 mmHg what happens to GFR, water filtered, & water excretion?
increase in GFR
increase in amount of water filtered
decrease in water excretion
217
Define hypernatremia
high plasma sodium
218
Define hyponatremia
low plasma sodium
219
What is the primary solute in extracellular fluid?
sodium
220
Sodium is critical for what 2 things?
normal osmotic pressure
function of excitable cells
221
What does aldosterone do?
it increases sodium reabsorption
222
How does aldosterone increase sodium reabsorption?
it acts on principal cells of distal tubules & collecting ducts to increase the number of Na/K pumps on the basolaterla membrane and Na+, K+ channels on the apical membrane
223
What organ secretes angiotensinogen?
the liver
224
What turns angiotensinogen into angiotensin 1?
renin
225
What turns angiotensin 1 into angiotensin 2?
ACE
226
What stimulates aldosterone production?
angiotensin 2
227
What 3 factors increase renin release?
1. decrease in BP in afferent arteriole
2. increase in renal sympathetic nerve activity
3. decreased Na+ and Cl-
228
What cells secrete ANP (atrial natriuretic peptide)?
atrial cells
229
ANP is secreted in response to what?
atrial wall stretch
patients with heart failure will show high levels of ANP
230
An increase in ANP causes what chain of events?
increase in afferent arteriole radius
decrease of efferent arteriole radius
increase in glomerular pressure
increase in GFR
increase in Na+ EXCRETION
increased urine volume
231
Where is K+ freely filtered?
glomerulus
232
Where is K+ reabsorbed?
proximal & tubules
233
Where is K+ secreted?
distal tubules & collecting ducts
234
Which hormone affects K+ secretion?
aldosterone
an increase in aldosterone release = an increase in K+ secretion
235
Define hypercalcemia
high plasma calcium
236
Define hypocalcemia
low plasma calcium
237
Why is calcium balance critical?
it triggered exocytosis, secretion, and muscle contraction
238
Where is the majority of calcium reabsorbed?
in the proximal tubules
239
Where is the rest of calcium reabsorbed?
loop of henle & distal tubules
240
Reabsorption of Ca2+ in the loop of henle & distal tubules is regulated by what 2 hormones?
parathyroid hormone (PTH)
calcitonin
241
How does parathyroid hormone (PTH) affect [Ca2+]?
it increases Ca2+ reabsorption thus increasing plasma [Ca2+]
242
How does calcitonin affect [Ca2+]?
it decreases plasma [Ca2+]
243
How does a decrease in blood pressure & blood volume affect ADH?
it increases its secretion
244
Where is aldosterone secreted?
adrenal gland
245
How does a decreased in blood pressure and blood volume affect ADH?
it increases its secretion
