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psl201: physiology > 4 week 20 > Flashcards

4 week 20 Flashcards

1
Q

what are the 4 key processes of the GI system?

A
  1. motility
  2. digestion
  3. absorption
  4. secretion
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2
Q

does food enter the pharynx or esophagus first?

A

pharynx

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3
Q

mucosa components (3)

A
  1. epithelial lining: contains absorptive, exocrine and endocrine cells
  2. lamina propria: connective tissue with small blood vessels, lymphatic vessels, nerves, lymphoid tissue
  3. muscularis mucosae: thin smooth muscle for mixing luminal
    contents
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4
Q

submucosa components (3)

A
  1. thick layer of connective tissue that is distensible and elastic
  2. contains large blood vessels and lymphatic vessels
  3. submucosal plexus
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5
Q

muscularis externa components (2)

A
  1. smooth muscle: mixing luminal contents and moving it down the digestive tract (inner circular layer: changes diameter, outer longitudinal layer: changes length)
  2. myenteric plexus
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6
Q

serosa components (3)

A
  1. inner layer: connective tissue
  2. outer layer: epithelial tissue (mesothelium)
  3. mesothelium is continuous with mesenteries, which are continuous with peritoneum
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7
Q

diff bw upper and lower esophageal sphincters?

A
  • upper = skeletal muscle
  • lower = smooth muscle
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8
Q

what are the 4 parts of the stomach?

A
  1. fundum
  2. body
  3. antrum
  4. pylorus
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9
Q

functions of the…
a) rugae
b) chief cells
c) parietal cells
d) neck cells

A

a) ruggae: flatten to accommodate food
b) chief cells: secrete pepsinogen
c) parietal cells: secrete HCl
d) neck cells: secrete mucus

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10
Q

the stomach slowly empties chyme into the ____

A

small intestine

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11
Q

what are the secretions of the stomach? (5)

A
  1. pepsinogen: secreted by chief cells (precursor for pepsin which digests proteins)
  2. hydrogen ions: secreted by parietal cells (maintain acidity)
  3. intrinsic factor: secreted by parietal cells (necessary for absorption of vitamin B12)
  4. mucus: secreted from neck cells and cells on stomach surface (protects the stomach lining)
  5. gastrin (hormone): secreted from G cells
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12
Q

3 layers of the small intestine?

A
  1. duodenum
  2. jejunum
  3. ileum
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13
Q

what are villi? lacteals?

A
  • villi: projections in small intestine that increase absorption
  • lacteals: projections in villi that allow lymphatic drainage
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14
Q

functions of small intestine? (4)

A
  • digestion of all types of nutrients
  • main site of absorption of nutrients
  • segmentation (mixes contents) and peristalsis (moving contents towards colon)
  • releases hormones that regulate gastrointestinal activity and metabolism
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15
Q

how does food travel through the large intestine?

A

cecum -> ascending -> transverse -> descending colon

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16
Q

colon functions? (3)

A
  • concentration of wastes into feces
  • absorption of water
  • storage of feces until defectaion
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17
Q

diff bw internal and external anal spinchter?

A
  • internal = smooth muscle
  • external = skeletal muscle
  • relaxation of both sphincters necessary for defecation
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18
Q

ACCESSORY GLANDS: products are secreted via ___ into the lumen of the GI tract

A

ducts

19
Q

which ions is saliva rich in? (1) what else does saliva contain? (3)

A
  • bicarbonate ions
  • mucus, salivary amylase (for carb digestion), lysozyme
20
Q

PANCREAS: what do the following structures do…
a) duct cells
b) islet cells
c) acinar cells

A

a) secrete bicarbonate-rich fluid
b) secrete hormones
c) secrete enzymes

21
Q

where does the pancreatic duct lead to?

A

to the duodenum (sphincter of oddi is there + controls entry of bile)

22
Q

what is the pancreatic juice composed of? (4)

A
  • bicarbonate (neutralizes chyme)
  • pancreatic amylase and lipases
  • proteases
  • nucleases
23
Q

functions of liver? (3)

A
  • removal of old RBC
  • secretes bile (bile salts and waste products e.g. bilirubin)
  • processes and stores nutrients
24
Q

describe how bile is made and where it travels (4)

A
  • hepatocytes make bile
  • secrete bile into bile canaliculi
  • canaliculi drain into bile ducts
  • bile ducts drain into common hepatic duct
25
Q
  1. materials absorbed in the small intestine and colon travel to ___ first via the hepatic portal vein
  2. materials in the hepatic portal vein and are taken up by ___ or continue to the rest of the body via the ____.
A
  1. liver
  2. hepatocytes, hepatic vein
26
Q

what does the gallbladder store?

A

bile

27
Q

what carbs are polysaccharides (3)? disaccharides (3)?

A
  • polysaccharides: starch, glycogen, cellulose (fiber)
  • disaccharides: sucrose (gl + f), lactose (gl + ga), maltose (gl + gl)
28
Q

brush border enzymes of the small intestine complete carbohydrate digestion. what are the 5 enzymes?

A
  1. dextrinase: limit dextrins → glucose
  2. glucoamylase: polysaccharides → glucose
  3. sucrase: sucrose → fructose + glucose
  4. lactase: lactose → galactose + glucose
  5. maltase: maltose → 2 glucose
29
Q

describe how the absorption of monosaccharides occurs in small intestine

A
  • maltase breaks maltose into 2 glucose
  • glucose + galactose use sodium symporters (sodium goes down gradient, glucose + galactose go against)
  • fructose uses glut 5 transporter (facilitated diffusion) into apical membrane… exits cells into blood via glut 2
  • NaK ATPase keeps sodium balance
30
Q

PROTEASES: what do endopeptidases vs exopeptidases do?

A
  • endo = breaks into two
  • exo = breaks one pieces off the end
31
Q

where are proteases? (3)

A
  • stomach
  • pancreas (trypsin, chymotrypsin, carboxypeptidase)
  • brush border (aminopeptidase, enterokinase)
32
Q

protein digestion begins in the stomach. describe this process.

A
  • pepsin starts breaking proteins down (acid cleaves pepsinogen to get pepsin)
  • positive feedback loop
33
Q

amino acid and di- and tripeptide absorption occurs in the ___. how does this occur?

A
  • small intestine
  • symporters bring them in
  • within the cell, peptidases cleave di and tri into singles
  • amino acid transporter transports them out of cells and into blood
  • NaK ATPase provides gradient for this to be possible
34
Q

T or F: lipids mix with stomach or intestinal contents

A

false

35
Q

where does most fat digestion occur? how?

A
  • small intestine
  • bile salts emulsify fat (breaks fat globules into smaller ones)
  • increases the surface area for further digestion by pancreatic lipase
36
Q

what are bile salts?

A
  • synthesized in liver from cholesterol
  • hydrophilic and hydrophobic
37
Q

how do fatty acids and monoglycerides get into the enterocyte? (2)

A
  1. diffuse into cell
  2. FA transporter
38
Q

what happens after the fatty acids and monoglycerides get into the enterocyte? (4)

A
  1. they synthesize new triglycerides in smooth endoplasmic reticulum
  2. triglycerides combine with other lipids and proteins in the golgi apparatus to form chylomicrons
  3. chylomicrons leave the enterocyte via exocytosis and enter the lacteal
  4. chylomicrons travel via the lymphatics to the blood stream (can then be acted on by lipases, taken up by liver)
39
Q

what is enterohepatic circulation? (3)

A
  • bile salts initially made by liver
  • stored in and released from gallbladder
  • travel thru duodenum + ileum + capillaries
  • end up in hepatic portal vein and travel back to liver
40
Q

how are vitamins absorbed?

A
  • fat soluble vitamins (ADEK): absorbed with lipids
  • water soluble vitamins: require special transport proteins
  • vitamin B12: absorbed in ileum only if bound to intrinsic factor
41
Q

how are minerals absorbed?

A
  • sodium: transporters, channels (mainly NaK ATPase)
  • chloride: passively follows sodium
  • potassium: passively absorbed mainly via paracellular route
  • bicarbonate: passively absorbed in jejunum, secreted in exchange for chloride ions in ileum and colon
42
Q

how are calcium and iron absorbed?

A
  • CALCIUM
  • mostly via paracellular route (NONREGULATED)
  • also have calcium channels directly into cell
  • cytosolic calcium levels influenced by calbindin (increases drive for calcium to enter cell) (REGULATED)
  • calcium can exit cell via calcium ATPase
  • …
  • IRON
  • transported in via symporter (DMT1)
  • when iron is high, hepcidin is released which decreases ferroportin transporters to stop iron absorption
43
Q

how is water absorbed?

A

passively (follows absorption of solutes by osmosis mainly via a paracellular route)

psl201: physiology (21 decks)

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