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BIOM 3200 > Digestive system > Flashcards

Digestive system Flashcards

1
Q

what is the average transit time in the large intestine

A

men and kinds - 33h
women - 47h
average - 40h

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2
Q

what is digestion

A

the breakdown of food molecules into their monomers by hydrolysis

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3
Q

what is absorption

A

process of how monomers are transported across the wall of the small intestine into the blood and lymph

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4
Q

what is metabolsim

A

the use of ingested food molecules in reactions of cell respiration to produce ATP

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5
Q

what is the alimentary canal

A
  • series of hollow organs joined in a long, twisting tube
  • oral cavity to anus
  • continuous with the environment on both ends
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6
Q

what are the accessory organs in the digestive system

A

teeth, tongue, salivary glands, liver, gallbladder, pancreas

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7
Q

what are the structures of the alimentary canal/digestive tract

A
  • mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus
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8
Q

what are the layers (tunics) of the alimentary canal

A

mucosa
submucosa
muscularis
serosa

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9
Q

mucosa layer

A

absorptive and secretory layer

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10
Q

submucosa layer

A

highly vascular layer of connective tissue

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11
Q

muscularis layer

A

responsible for contractions and peristaltic movements
(break and mix food with digestive enzymes)

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12
Q

serosa layer

A

connective tissue continuous with the mesentery and visceral peritoneum (connects digestive tissues to abdomen walls)

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13
Q

tongue structure

A
  • the tongue is converted in backward facing projections called filiform papillae
  • filiform papillae sense pressure
  • have a scaly appearance
  • papillae are constantly shedding this top layer of skin
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14
Q

cat tounge

A
  • hollow which allows them to secrete more saliva
  • helps cats cool down
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15
Q

what are the 3 pairs of salivary glands

A
  1. sublingual: under the tongue
  2. submandibular: under jaw
  3. parotid: posterior (close to ear) - largest pair
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16
Q

functions of salivary glands

A
  • lubrication of the mouth and throat
  • solubilization of dry food (taste)
  • oral hygiene - antimicrobial peptides attack pathogens in food
  • alkaline buffering - prevents demineralization of enamel (from acidic foods)
  • begins starch digestion (salivary amylase)
  • evaporative cooling
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17
Q

true or false: if you produce less saliva you have a greater chance of getting cavities

A

true

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18
Q

how do the teeth contribute to digestion

A

teeth are responsible for mastication (chewing and mixing food with saliva)

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19
Q

what are the jobs of the different types of teeth

A

incisors: rip and cut
canines: tear and pierce
premolars: grind and shear
molars: grind

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20
Q

true or false: the teeth are the softest structure in the body

A

false - are the hardest

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21
Q

tissues involved in deglutition (swallowing)

A
  • involves 25 pairs of muscles in the mouth, pharynx, larynx and esophagus
    striated muscles: mouth, pharynx and upper esophagus
    smooth muscles: lower esophagus
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22
Q

3 phases of deglutition (swallowing)

A
  1. oral phase: somatic - muscles of the tongue and mouth mix the food with saliva to create a bolus
  2. Pharyngeal phase: autonomic - nasal cavity and larynx are closed off
  3. Esophageal phase: autonomic - food bolus moved by peristaltic contractions
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23
Q

what is the esophagus

A
  • connects the pharynx to the stomach
  • 25cm long muscular tube, located behind the trachea
  • upper third = skeletal muscle
  • middle third = mix of skeletal and smooth muscle
  • lower third = smooth muscle
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24
Q

what is esophageal peristalsis

A

moving food in a wave-like muscular contraction through the esophagus

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25
Q

how do peristaltic contractions move food

A
  • move the bolus from the esophagus into the stomach
  • contractions progress from the superior end of the esophagus to the gastroesophageal junction at a rate of 2-4 cm/second
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26
Q

what is the esophageal hiatus

A
  • where the esophagus passes through the diaphragm
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27
Q

what is the lower esophageal sphincter

A
  • the terminal portion of the esophagus where the lumen is slightly narrowed due to the thickening of muscle fibres
  • sphincter relaxes = food enters the stomach
  • sphincter constricts = prevents regurgitation of stomach contents
    sphincter = misnomer
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28
Q

sphincter in rodants

A
  • known as a true sphincter
  • rodents cannot regurgitate because their sphincter prevents back flow
  • mouth gaping = nausea (might have eaten something toxic)
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29
Q

the stomach of ruminants

A

1st chamber: rumen - allows to breakdown of cellulose
2nd chamber: reticulum - regurgitates food back to the ruminants mouth, cud is chewed and re-swallowed
3rd chamber: omasum
4th chamber: abomasum

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30
Q

3 main functions of the stomach

A
  1. storage of swallowed food and liquids: muscles of the cardiac and fundus relax to accept large food volumes
  2. mixes up food/liquid with digestive juices: in the lower pyloric region by muscles, begins protein digestion and acidity kills bacteria
  3. slowly empties contents (chyme) into the duodenum
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31
Q

musculature of the stomach

A
  • smooth muscle layers run longitudinal, circular and oblique
  • provides complex motility to mix and mechanically break up food in the stomach
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32
Q

main regions of the stomach (top to bottom)

A
  • cardiac region (fundus and body)
  • pyloric region (antrum to pyloric sphincter)
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33
Q

food movement through the stomach

A
  • food is delivered to the cardiac region of the stomach
  • chyme is churned and enters the duodenum through the pyloric sphincter
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34
Q

what are gastric pits

A
  • opening off of gastric glands, which are cells that line the folds into the stomach
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35
Q

What is the purpose of gastric glands

A
  • contain many types of cells to produce a specific secretion in the stomach
  • exocrine secretions of the gastric cells + large amount of water = gastric juice (highly acidic)
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36
Q

types of cells in the gastric glands of the stomach

A

mucous cells: secrete mucus
parietal cells: secrete HCl and intrinsic factor (bound to vit B12 - essential for life)
chief (zymogenic) cells: secrete pepsinogen

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37
Q

What do pepsinogen and HCl do in the stomach

A
  • in the presence of HCl, the inactive enzyme pepsinogen becomes pepsin (active)
  • pepsin can digest proteins into smaller polypeptides
  • the high [HCl] makes gastric juice very acidic and denatures protein to make them more digestible
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38
Q

why doesn’t the stomach digest itself

A

major barrier: adherent layer of gastric mucus on the epithelial surface
- epithelial surface has alkaline bicarbonate making pH at epithelial surface near neutral
- causes slow diffusion of pepsin to epithelial cells
- tight junctions between epithelial cells protect underlying tissues from acid/pepsin
- cell division replaces the entire gastric epithelium every 3 days

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39
Q

what are peptic ulcers

A

caused by erosion of the mucosa
- duodenal ulcers are caused by excessive gastric acid secretion
- peptic ulcers are caused by reduced barriers of self digestion

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40
Q

Helicobacter pylori

A

common bacteria that survives very acidic pH and cause digestion of protective barrier leading to peptic ulcers

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41
Q

regions of the small intestine

A

duodenum
- first 20-30cm, extends from pyloric sphincter
- mucous secretion, receives pancreatic secretions and bile from the liver
jejunum
- 1m in length, numerous folds and vili
Ileum
- last 2m, fewer folds and vili
- absorbs primarily bile salts, water and electrolytes
- contains Peter’s patches
- empties into the large intestine via ileocecal valve

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42
Q

types of folds in the small intestine

A
  • extensive folding increases surface area for absorption which increases rate of absorption
    plicae circulares: big folds created from mucosa and submucosa
    villi: microscopic folds of mucosa
    microvilli: foldings on apical plasma membrane of epithelial cells
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43
Q

which regions of the SI are certain particles absorbed in

A

duodenum and jejunum: carbs, lipids, AAs, Ca2+, iron
ileum: bile salts, Vit B12, H2O, electrolytes

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44
Q

characteristics of Villi

A
  • covered with columnar epithelial cells (enterocytes)
  • goblet cells in villi secrete mucus
  • epithelial cells at the tip of villi are continuously replaced
  • invaginations of villi form pouches = intestinal crypts
  • paneth cells at the base secrete antibacterial lysosomes and antimicrobial peptides (defensins) to protect against pathogenic bacteria while preserving commensal bacteria
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45
Q

characteristics of microvilli

A
  • formed by foldings at the apical surface of each epithelial PM
  • produce a brush border
  • contain wide diversity of enzymes for absorption and digestion
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46
Q

Brush border enzymes

A
  • remain attached to the PM other their active sites exposed to the chyme (in the lumen)
  • examples of brush border enzymes are surcease, maltase, lactase, aminopeptidase, and enterokinase
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47
Q

how does food enter into the large intestine

A
  • chyme enters through the ileum into the cecum (blind pouch)
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48
Q

structure of the large intestine

A
  • covered by columnar epithelial cells and goblet cells, but no villi present
  • external layer of smooth muscle (taenia coli)
  • formation of haustra (pouches)
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49
Q

function of the large intestine

A
  • little to no digestive function
  • absorbs water, electrolytes and vitamins
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50
Q

microbiota of the large intestine

A
  • has several thousand microorganisms
  • composed of anaerobic bacteria
  • commensal bacteria
  • bacteria digest dietary fibre into monosaccharides and SCFA
51
Q

what consequence for the large intestine might antibiotics pose

A

antibiotics may cause diarrhea by reducing the commensal bacteria population and thus SCFA production for water reabsorption

52
Q

body fat % and intestinal microbiota

A
  • obese subjects have less diversity and different relative abundance of particular microbes
  • microbiota of obese subjects is more populated with bacteria that promote adipose storage and deficient in those that metabolize fiber
53
Q

what is the appendix

A
  • a small component of the colon
  • contains numerous lymphoid nodules and may house a population of commensal bacteria that helps to replenish a normal microbiota
54
Q

what is appendicitis

A
  • inflammation of the appendix
  • causes pain in the lower right quadrant of the abdomen and nausea
  • a ruptured appendix can cause inflammation in the surrounding peritoneal membranes - peritonitis
  • can cause circulatory shock and death
55
Q

why do wombats poop cubes

A
  • the wombats intestine is 10x the length of their body
  • the digestive process is 4x longer than humans so they can extract all possible nutritional conent
  • they extract all water, so their faces is extremely dry
  • cubes formed within the last 17% of the colon
56
Q

how muscles in wombat colons give their poop a cube shape

A
  • azimuthal contractions of an elastic ring composed of stiff and soft regions
  • increased stiffness ratio and higher Reynolds number yield shapes that are more square
  • the corners arise from faster contraction in the stiff regions and relatively slower movement in the centre of the soft regions
57
Q

what are sinusoids

A
  • large capillary spaces that separate hepatic plates
  • much more permeable than other capillaries
  • contain Kupffer cells (liver-specific macrophages)
58
Q

how is the liver able to regenerate itself

A
  • if 2/3 of a rodents liver is removed the remaining tissue can regenerate to its original mass in one week
  • hepatocytes in damaged liver convert to stem-like “progenitor” cells
  • then proliferate and differentiate back to hepatocytes
59
Q

what is the hepatic portal system

A
  • system of blood vessels that delivers digestion products to and from the liver
  • capillary to vein to capillary to vein
60
Q

Path of the hepatic portal system

A
  • digestion products absorbed into blood capillaries of the intestine first get delivered to the liver via the hepatic portal vein
  • blood then passes through downstream liver capillaries and enters general circulation via the hepatic vein
61
Q

what does the hepatic artery do

A

delivers blood from the heart to the liver

62
Q

what does the hepatic portal vein do

A
  • delivers blood to the liver from blood capillaries in the intestine
  • also drains capillaries of the pancreas, gallbladder and spleen
63
Q

what are portal lobules of the liver

A
  • hepatic plates arranged into functional units, gets blood from the hepatic portal vein to the inferior vena cava
  • the central vein is present in the middle of each lobule
  • blood branches from the hepatic portal vein and hepatic artery open into sinusoids
  • blood mixes and then enters the central vein
  • central veins converge to form the hepatic vein and go to the inferior vena cava
64
Q

functions of the liver

A
  • detoxication of blood
  • carbohydrate metabolism
  • lipid metabolism
  • protein synthesis
  • secretion of bile*
  • storage of molecules
65
Q

how does bile from the liver get to the gallbladder for storage and then released to the small intestine

A
  • Bile is produced by hepatocytes and secreted into bile canaliculi within each hepatic plate
  • Bile canaliculi drain into bile ductules present in each portal lobule
  • bile then drains into hepatic ducts
  • the right and left hepatic ducts meet up with the cystic duct from the gallbladder and together form a common bile duct which then goes to the intestines
66
Q

what is a trigger for bile release

A

a fatty meal reaching the duodenum
- bile salts in the intestines will form micelles around big pieces of fat to help break them down

67
Q

what are the major constituents of bile

A
  • bile acids/salts*
  • bilirubin
  • phospholipids
  • cholesterol
  • inorganic ions
68
Q

formation of primary and secondary bile acids and salts

A
  • cholesterol in the liver is used to produce primary bile acids
  • primary bile acids get conjugated = bile salts
  • bile salts are stored in the gallbladder or go to the small intestine
  • intestinal microbiota convert primary bile acids to secondary bile acids
  • small portions of secondary bile acids are excreted into feces and most get reabsorbed through the portal system
69
Q

what are bile salts

A
  • primary bile acids that get conjugated to AAs in the liver OR secondary acids that get re-conjugated
  • they are amphipathic - the AA portion is hydrophilic
70
Q

true or false: 95% of bile acids are recycled?

A

true - in the intestines microbiota can unconjugate bile salts to make bile acids that enter enterohepatic circulation

71
Q

What is the gallbladder

A
  • Sac-like organ attached to the interior surface of the liver
  • stores and concentrates bile from the liver
72
Q

how does the gallbladder release stored bile

A
  • contraction of the muscularis layer ejects bile through the cystic duct into the common bile duct which guest to the duodenum
73
Q

how does bile enter the gallbladder for storage

A
  • when the small intestine is empty the sphincter of the ampulla at the end of the common bile duct closes - this forces bile to move up the cystic duct and enter the gallbladder
74
Q

what are gallstones

A
  • form when bile stored in the gallbladder hardens into mineral deposit
  • may be due to too much cholesterol, bile salts or bilirubin
  • may block hepatic, cystic or common bile ducts
  • may use shock waves to break up stones or perform a cholecystectomy
75
Q

what is the exocrine function of the pancreas

A
  • secretes pancreatic juice through the pancreatic duct into the duodenum for digestion
76
Q

what are pancreatic acini

A

exocrine secretory units within the pancreatic lowest
- each one consists of a single layer of epithelial cells surrounding a lumen which secretes juice

77
Q

difference between the endocrine and exocrine portions of the pancreas

A

endocrine: includes pancreatic islets
exocrine: includes pancreatic acini

78
Q

what is pancreatic juice

A

a mixture od bicarbonate and many other digestive enzymes including…
amylase: digests starch
trypsin: digests proteins
lipase: digests triglycerides

79
Q

example of how digestion requires pancreatic enzymes PLUS brush border enzymes

A
  • the inactive form of trypsin (pancreatic enzyme) is activated at the brush border by the enzyme enterokinase
  • trypsin is a protease that can then activate other pancreatic enzymes
80
Q

time-restricted eating: mice experiment

A
  • mice were given a high-fat diet - one group had access 8hr/day and one 24hr/day
  • 24hr mice weighed 38% more than the 8hr mice after 4 months
  • 24hr mice had 4x body fat
  • TRF also protected them against diabetes, liver diseases and inflammation
81
Q

benefits of time-restricted eating

A
  • reduced total cholesterol and LDL levels, increased HDL
  • increased insulin sensitivity
  • reduced inflammation
82
Q

current hypothesis about TRE

A

eating for 12-15 hr a day may disrupt circadian rhythm and can increase risk of CV disease, cancer and diabetes
- known as chrononutrition

83
Q

negative impacts of time restricted eating

A
  • irritability
  • increase feeling of hunger and thought of food
  • bingeing during eating windows
  • difficulty concentrating
  • fatigue
84
Q

what determines the caloric value of food

A
  • carbs (50%)
  • protein (16%)
  • fat (makes up the rest)
85
Q

what is required of macromolecules for absorption

A
  • requires for food molecules to be hydrolyzed into their free monomers (except for cholesterol)
86
Q

common carbohydrates

A
  • most carbs are ingested as starch which are long polysaccharide chains of glucose
  • most commonly ingested sugars are sucrose and lactose
87
Q

steps in chemical digestion of carbohydrates

A
  • starch (polysaccharides) are digested by salivary and pancreatic amylases
  • disaccharides are digested by brush border enzymes
88
Q

carbohydrate brush border enzymes

A

Lactase: cleaves lactose –> glucose and galactose
Sucrase: cleaves sucrose –> fructose and glucose
Maltase: cleaves maltose –> multiple glucose
a-dexrrinase (glucoamylase): cleaves small glucose polymers

89
Q

digestion of carbs by a-amylase (ptyalin)

A
  • digestion begins in the mouth with salivary amylase
  • ptyalin hydrolyzes starch into maltose and other short glucose polymers
  • ptyalin is inactivated by stomach pH and the rest of complex carbs get digested by pancreatic amylase
90
Q

digestion of carbs by pancreatic amylase

A
  • digestion of carbs mainly occurs in the duodenum by pancreatic amylase
  • pancreatic amylase is more potent that the salivary source
  • it cleaves straight chains of starch to produce maltose, maltose, and short, branched oligosaccharides
91
Q

how long does it take to hydrolyze all carbs into small glucose polymers

A

30 minutes

92
Q

digestion pathway of carbs

A

mouth: salivary amylase
duodenum: pancreatic amylase
rest of the SI: dextrinase and glucoamylase
brush border: lactase, maltase, sucrase

93
Q

Carbohydrate absorption at the small intestine

A
  • disaccharides are hydrolyzed to their monosaccharides by brush border enzymes on microvilli
  • the monosaccharides formed are lactose, glucose and fructose
94
Q

absorption of specific monosaccharides

A
  • glucose is co-transported with 2 Na+ into the epithelial cell cytoplasm (secondary active transport)
  • glucose moves through the GLUT transporter (facilitated diffusion) across the basolateral membrane into the capillary
  • fructose can be directly absorbed - doesn’t need a transporter
95
Q

post-absorptive events of glucose: after a meal

A
  • blood leaving the villi of the SI drain into blood vessels that lead directly to the liver via the hepatic portal vein
  • a rise in blood glucose causes insulin release from the endocrine pancreas
  • results in an increased uptake of glucose by the liker and skeletal muscle
96
Q

what is glycogenesis

A
  • ## the formation of glycogen from glucose for storage
97
Q

post-absorptive events of glucose: in between meals

A
  • in between meals blood glucose levels decrease
  • causes the release of glucagon from the endocrine pancreas which stimulates glycogen breakdown in the liver = GLYCOGENOLYSIS
98
Q

what is glycogenolysis

A

generates free glucose from glycogen that can be released into the blood

99
Q

what is glycemic index

A
  • the rate at which food makes your blood sugar rose
  • high = blood sugar rises quickly after a meal
  • can be seen as the area under the 2h blood glucose response curve after ingestion
100
Q

which food have high medium and low GL

A

high = rice and donut
medium = whole wheat bread and mango
low = banana and soy protein shake

101
Q

what is the AUC test food/AUC standard (glucose

A

GI =100
- average GI calculated from multiple subjects

102
Q

high glycemic index

A
  • blood sugar rises quickly after a meal
  • carbohydrates break down quickly and are rapidly released into blood stream
103
Q

what is cholesterol

A
  • cholesterol is essential for the functioning of all animal cells - a component of cell membranes
  • it is a precursor for the synthesis of steroid hormones
  • it is the base substrate for the synthesis of bile acids and vitamins D3
104
Q

post-absorptive events of cholesterol

A
  • a small molecule that is absorbed from food without being digested
  • most blood cholesterol is produced in the liver, only 20% comes from diet
  • can directly pass through microvilli into intestinal epithelial cells where it is incorporated into chylomicrons which enter lymphatic vessels
  • will drain into the venous circulation and go to the liver
105
Q

how is cholesterol transported in the blood

A
  • in the blood cholesterol is associated with lipoproteins
  • cholesterol produced in the liver is transported to organs and blood vessels via LDLs
  • elevated LDL-cholesterol levels mean lipids can’t deposit in arterial vessel walls = atherosclerosis
  • excess cholesterol is returned to the liver attached ti HDLs
  • HDLs bind to receptors in blood vessels and take up free cholesterol (protection against atherosclerosis
106
Q

what are the 3 major lipid groups in out diet

A
  • triglycerides, phospholipids and sterols (such as cholesterol)
107
Q

digestion of lipids

A
  • up to 30% of fat digestion occurs in the mouth and stomach by lingual and gastric lipase
  • majority of fat is digested in the small intestine by pancreatic lipase
  • the arrival of lipids in the duodenum stimulates the secretion of bile to help with emulsification
108
Q

emulsification of lipids

A
  • emulsification is when bile salt micelles are secreted into the duodenum from the gallbladder and liver
  • bile salts act as detergents to break up fat droplets into smaller emulsification droplets
  • NOT chemical digestion
  • the smaller emulsification droplets presents a greater surface area for enzymatic action
109
Q

how does Colipase work I lipid digestion

A
  • ## colipase is secreted by the pancreas and coats emulsification droplets and anchors pancreatic lipase to them
110
Q

hydrolysis of tryglycerides

A

lipase cleaves triglycerides into 2 FFAs and a monoglyceride

111
Q

phospholipase A

A
  • digests phospholipids
112
Q

how do lipids get to the BBM

A
  • free fatty acids and monoglycerides are incorporated into micelles of bile salts
  • they move to the brush border where they will be absorbed
113
Q

3 steps in lipid digestion in the SI

A
  • emulsification of fat droplets by bile salts
  • hydrolysis of triglycerides in emulsified fat droplets into fatty acid and monoglycerides
  • dissolving of fatty acids and monoglycerides into micelles to produce mixed micelles
114
Q

absorption of lipids

A

once we get to the brush border…
- fatty acids and monoglycerides can leave the micelles and enter the intestinal epithelial cells
- triglycerides are resynthesized by fatty acids and monoglycerides
- triglycerides combine with phospholipids, cholesterol and protein to form small particles = chylomicrons
- chylomicrons are secreted by exocytosis, enter lacteals (lymphocytes) and go into the venous circulation

115
Q

transport of lipids in the blood

A
  • chylomicrons acquire a protein called ApoE which allows binding to receptors on the PM of endothelial cells in muscles and adipose tissue
  • triglycerides of chylomicrons are digested by lipoprotein lipase on the PM of these cells
  • after the triglycerides are broken up the remnant particle containing cholesterol is released and travels back to the liver
116
Q

what is the fate of digested triglycerides of chylomicrons

A
  • releases free FAs that can enter tissues
  • heart and skeletal muscles use for energy
  • stored in adipose tissue
117
Q

digestion of proteins in the stomach

A
  • protein digestion begins in the stomach
  • high [HCl] makes gastric juice very acidic, thereby denaturing digestible proteins to make them more digestible
  • pepsin is a protease that digests proteins into short-chain polypeptides
  • this helps produce a more homogenous chyme
118
Q

digestion of proteins in the small intestine

A
  • major protein digestion happens in the duodenum and jejunum
  • trypsin, chymotrypsin and elastase are pancreatic juice enzymes that cleave peptide bonds in the interior of polypeptide chains = endopeptidases
  • carboxypeptidase and amino peptidase cleave the ends of polypeptide chains
119
Q

exopeptidases

A

carboxyl peptidase: pancreatic juice enzyme, removes AAs from the c-terminal end
aminopeptidase: brush border enzyme, removes AAs from the N-terminal end

120
Q

absorption of proteins

A
  • results in amino acids, dipeptides and tripeptides
  • free AAs are absorbed across the BBM by different secondary active transport carriers
  • di and tripeptides enter epithelial cells by a single membrane carrier and are hydrolyzed into free AAs in the cytoplasm
  • free AAs enter interstitial fluid by facilitated diffusion, then travel through capillary blood and the hepatic portal vein to get to the liver
121
Q

absorption of proteins: adults vs babies

A
  • in adults only free AAs will enter the hepatic portal vein
  • newborns can absorb a substantial amount of undigested protein - allows them to absorb antibodies from mom through breast milk (passive immunity)
122
Q

absorption of minerats

A

calcium
- absorption by active, carrier-dependent process and passive, paracellular process in the small and large intestine
- active process is vitamin D-dependent (PTH)
Iron ions
- absorbed in the duodenum
- most easily absorbed when bound to heme
K+, Mg2+ and phosphate
- direct absorption through the intestinal mucosa

123
Q

absorption of fat soluble vitamins

A
  • occurs mainly be passive diffusion in the jejunum and ileum
  • absorbed with dietary lipids (Vits A, E, D, K)
124
Q

absorption of water soluble vitamins

A
  • include Vit C and the B vitamins - diffuse into the blood, except for B12
  • B12 combines with intrinsic factor produced by the stomach, which the intestine absorbs by endocytosis
  • water-soluble vitamins pass into urine when their concentration in plasma exceeds the renal capacity for reabsorption

BIOM 3200 (7 decks)

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