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Physiology 2130 > Module 15 > Flashcards

Module 15 Flashcards

1
Q

State the overall function of the digestive system

A

Breaking down organic nutrients to be absorbed into the body (carbs, proteins, fats, water, vitamins, minerals)

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2
Q

List the anatomy of the digestive system, in order

A

Mouth, salivary glands, esophagus, stomach, liver, gallbladder, pancreas, small intestine, large intestine, rectum

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3
Q

Describe the basic function of the mouth

A

Break up food by chewing (mastication) and mix food with saliva

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4
Q

Describe the basic function of salivary glands

A

Produce saliva to moisten and begin digesting some food particles

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5
Q

Describe the basic function of the esophagus

A

A straight muscular tube connecting the mouth and pharynx to the stomach

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6
Q

Describe the basic function of the stomach

A

Store, mix, and digest some food and deliver food to the small intestine

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7
Q

Describe the basic function of the liver

A

Many functions, but for digestion specifically produces and stores bile

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8
Q

Describe the basic function of the gallbladder

A

Stores and concentrates bile produced by the liver

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9
Q

Describe the basic function of the pancreas

A

Secrete digestive enzymes, hormones, and bicarbonate

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10
Q

Describe the basic function of the small intestine

A

Allows digestion and absorption of most food particles

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11
Q

Describe the basic function of the large intestine

A

Stores and concentrates undigested material and absorbs salt and water

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12
Q

Describe the basic function of the rectum

A

Site where the defecation reflex is triggered

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13
Q

Describe secretion (digestion)

A

Release of digestive fluids into the lumen of the digestive tract; may include water, mucus, acid, electrolytes, enzymes, bile salts, and digestive enzymes

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14
Q

Define digestion

A

The process whereby food is broken down into smaller molecules by the digestive enzymes so they can be taken up by the body

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15
Q

Define absorption (digestion)

A

The process whereby small digested molecules are taken up by the circulatory system and distributed throughout the body

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16
Q

List the salivary glands

A

Parotid, sublingual, and submandibular

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17
Q

Describe saliva and its role in digestion

A

Mostly water with some ions and proteins
Up to 2L produced per day
Helps lubricate the bolus of food and begins digesting carbs with the enzyme amylase
Produced and secreted under control of the ANS

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18
Q

Describe the sequence of events involved with swallowing

A

Once bolus has been formed and lubricated with saliva, pushed to back of mouth by tongue to initiate swallow reflex
Uvula of soft palate closes nasopharynx
Larynx is lifted by muscles in neck, epiglottis bends over glottis, covering larynx
Bolus moves down esophagus through cardiac orifice into stomach by wave of smooth muscle contraction (peristalsis)

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19
Q

List the parts of the stomach

A

Fundus, body, antrum, cardiac orifice, pyloric sphincter, rugae

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20
Q

List the functions of the stomach

A

Liquefies, mixes, and stores bolus of food, creating chyme
Controls the release of chyme into the small intestine
Some digestion of proteins by pepsin
Absorption of alcohol and aspirin

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21
Q

List the secretions of the stomach

A

Mucus, HCl, pepsinogen, gastrin, intrinsic factor

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22
Q

Describe the function of mucus in the stomach and where it is secreted

A

Secreted by cells in body and antrum, protects lining of stomach from acidic environment

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23
Q

Describe the function of HCl in the stomach and where it is secreted

A

Secreted by cells in the stomach body, begins to denature complex protein and connective tissue molecules found in protein, kills bacteria and converts pepsinogen to pepsin

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24
Q

Describe the function of pepsinogen in the stomach and where it is produced

A

Produced by cells in the body of the stomach, when converted to pepsin by HCl begins to digest large protein molecules

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25
Q

Describe the function of gastrin in the stomach and where it is secreted

A

Secreted by cells in the antrum, it is a hormone that stimulates secretion of HCl

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26
Q

Describe the function of intrinsic factor in the stomach

A

Helps with absorption of vitamin B12

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27
Q

Describe the location and structure of the pancreas

A

Lies below the stomach, has exocrine and endocrine functions, main pancreatic duct that merges with common bile duct from liver and gallbladder before entering duodenum

28
Q

Describe the function of the pancreas in digestion

A

Produces and secretes amylase (carbs), trypsin, chymotrypsin, and proteases (proteins) and lipase (fat), also secretes bicarbonate into duodenum to neutralize acid

29
Q

List the three segments of the small intestine

A 
Duodenum (shortest)
Jejunum
Ileum (longest, 50% of small intestine)
30
Q

Describe the inner structure of the small intestine

A

Inner wall has large surface area with villi, containing capillary network and lymphatic lacteal, layer of epithelial cells covering villi, and microvilli that face into the lumen, creating a brush border

31
Q

Describe the functions of the small intestine in detail

A

Almost all digestion and absorption (duodenum and jejunum)
Digestion of chyme using digestive enzymes (from pancreas and epithelial cells) and bile (from liver for fats)
Large surface area good for absorption and motility (moving food through digestive tract)

32
Q

List the building blocks of carbohydrates

A

Monosaccharides (glucose, fructose, galactose) can form disaccharides (sucrose, maltose, lactose) or longer polysaccharides

33
Q

Describe carbohydrate digestion

A

Carbs must be broken down into monosaccharides to be absorbed
Digestion in mouth by amylase (to smaller polysaccharides and maltose)
Once in stomach, carb digestion stops in acidic environment
In duodenum, amylase starts digestion again (into disaccharides)
Each disaccharide requires specific enzyme to break down into monosaccharides

34
Q

Describe lactose intolerance

A 
People who don't produce lactase, cannot break down lactose (disaccharide) into monosaccharides
Causes diarrhea (from lactose in digestive tract) and gas, bloating, and cramps (from bacteria feeding on it)
Treated with synthetic lactase
35
Q

Describe carbohydrate absorption

A

Similar to glucose reabsorption in kidneys
Na+/K+ pump creates [ ] gradient, which powers Na+/glucose co-transporter (secondary active transport) on luminal side of cell, moves glucose into cell, then glucose diffuses out through basal side by facilitated diffusion

36
Q

List building blocks of proteins

A 
20 amino acids
11 nonessential (can be produced in the body)
9 essential (must come from diet)
37
Q

Describe protein digestion

A

Must be broken down into amino acids for absorption
Digestion begins in stomach when HCl converts pepsinogen to pepsin
HCl helps uncoil long proteins so pepsin can digest into smaller polypeptide chains
In small intestine, pancreatic enzymes trypsin and chymotrypsin continue digestion
Proteases from pancreas digest proteins into amino acids (endopeptidases and exopeptidases)

38
Q

Describe protein absorption

A

Can absorb single amino acids and small polypeptides
Uses secondary active transport, requiring Na+ [ ] gradient and Na+/amino acid co-transporter
Remaining small peptides absorbed by endocytosis

39
Q

Describe the structure of fats and lipids

A

Triglycerides (glycerol with three fatty acid chains)
Cholesterol
Long fatty acid chains
Phospholipids (glycerol, two fatty acid chains, and phosphate group)
Not water soluble so don’t mix with water

40
Q

Describe the breakdown of fatty acids

A

Emulsification (churning of the stomach to break up large drops of fat into small drops of fat)
Important because lipid digesting enzymes cannot work on large drops, only small ones, so need to stay emulsified

41
Q

Describe where bile is produced and stored

A

Produced in the liver

Transported to gallbladder for storage and concentration

42
Q

Describe the functions of bile

A

Not a digestive enzyme
Released during digestion into duodenum
Bile salts keep lipid droplets emulsified so they can’t form large droplets

43
Q

Describe colipase and its function

A

Secreted by pancreas
Not a digestive enzyme, a protein that allows lipase to get access to lipid interior of fat droplet when surrounded by bile salt

44
Q

Describe fat digestion

A

Fat droplets after emulsification and bile salt attachment contain different types of lipids
Pancreatic lipase removes fatty acid chains from glycerol, making droplets smaller
Droplets get small enough, become micelles (single layer of bile surrounding small lipid droplet)

45
Q

Describe fat absorption

A 
Fatty acids and monoglycerides diffuse through membrane of epithelial cells in small intestine
Cholesterol is transported into cells by active transport
Enter smooth ER to combine and form chylomicrons, which are packaged into secretory vesicles by golgi apparatus to leave cell
Enter lacteals (lymphatic system) then drain into circulatory system
46
Q

Describe the absorption of vitamins

A

Depends on water or lipid soluble
Lipid soluble are absorbed like fats
Water soluble are absorbed by carrier-mediated mechanisms (absorption similar to sugar and amino acids)

47
Q

List amounts of water absorbed in different sections of the digestive system

A

Duodenum and jejunum: 44%
Ileum: 38%
Large intestine: 1.5%
Remaining excreted

48
Q

Describe water absorption

A

Similar to in kidneys
As molecules of glucose, amino acids and lipids are absorbed, osmotic gradient builds across intestinal epithelial cells
Cells develop high solute concentration, causing water to flow in by osmosis
As solutes move out into circulation, water flows out by osmosis into blood

49
Q

Describe the absorption of ions

A

Na+ is same as in kidney, help from Na+/K+ pump on basal lateral surface of intestinal cells, establishes [ ] gradient, then Na+ moves into cells down [ ] gradient, and along with carbs and amino acids in co-transporters
K+ absorbed passively by diffusion

50
Q

List the parts of the large intestine

A

Ileocecal valve, cecum, appendix, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anus

51
Q

Describe the functions of the large intestine

A

Absorb water and electrolytes
Store and concentrate feces
Na+ absorbed by active transport, water by osmosis
Most absorption in first half
Secretes mucus to protect lining from chemical and mechanical damage and to lubricate feces
Some K+ and bicarbonate secreted into colon
Little digestion of polysaccharides by bacteria, absorbed by passive diffusion and causing gas and vitamin K production

52
Q

Describe the purpose enteric nervous system

A

Both branches of the ANS (PSYN and SYN) can influence activity of the digestive tract by altering activity of nerves in the ENS
Nerves affect smooth muscle activity, enzyme-secreting cells, endocrine cells, and blood vessels

53
Q

Describe how the enteric nervous system functions

A

Two reflex loops
Long loop travels through CNS
Short loop travels locally within digestive system

54
Q

Describe the short loop of the ENS

A

Begins by a mechanical distension of digestive tract or chemical change like pH or osmolarity
Changes detected by sensors of ENS that initiate reflex
Reflex activates effector organs, like secretory cells or smooth muscle, causing release of enzymes or altering motility

55
Q

Describe the long loop of the ENS

A

Include input from higher brain centers
Stimulus could be sight or smell of food
Signals sent through PSYN to ENS to alter digestive function - enzyme release and gastric motility

56
Q

Define motility (digestion)

A

The muscular contractions of the stomach that mix food and propel it through the digestive tract
Needs regulation to ensure digestion and absorption is completed

57
Q

Describe how motility is regulated

A 
Interstitial cells (specialized smooth muscle cells) surrounding the digestive tract act like pacemaker cells of the heart
Alter their membrane potentials, producing BERs, whose frequency determines number of waves (3/min in stomach, 12/min in duodenum)
58
Q

Describe how BERs regulate gastric motility

A

Can alter their membrane potentials, don’t cause muscle contraction often because don’t often reach threshold
Spread through gap junctions
Reaching threshold requires additional stimulus (mechanical, nervous, or hormonal) to fire action potentials and cause smooth muscle contraction

59
Q

List the hormones of the intestine

A

Secretin, CCK, and glucose-dependent insulinotropic peptide

60
Q

Describe the function of secretin in the intestine

A

Released in response to presence of acid in intestine
Inhibits emptying from stomach
Causes release of pancreatic bicarbonate and bile from liver
Results: bicarbonate neutralizes stomach acid so digestive enzymes in intestines can function

61
Q

Describe the function of CCK in the intestine

A

Released in presence of fats
Slows emptying of stomach
Stimulates pancreas to release digestive enzymes
Causes gallbladder to contract and release bile

62
Q

Describe the function of glucose-dependent insulinotropic peptide in the intestine

A

Secreted in response to glucose and amino acids
Stimulates release of insulin
May inhibit emptying of stomach

63
Q

Describe the function of gastrin (hormone) in the stomach

A

Secreted by G cells (in antrum) in response to presence of proteins, mechanical distension, and stimulation from PSYN
Primary function: cause secretion of HCl to convert pepsinogen to pepsin

64
Q

List the three phases of gastric acid secretion

A 
Cephalic phase (brain)
Gastric phase (stomach)
Intestinal phase (intestine)
65
Q

Describe the cephalic phase

A

Increased gastric acid secretion initiated in response to sight, smell, taste, or chewing food (triggers PSYN)
Anticipatory response, activates long loop reflex of ENS
Causes parietal cells to release HCl
Causes G cells to release gastrin
Stomach motility increases

66
Q

Describe the gastric phase

A

Begins once food is swallowed
Stimulus is presence of food in stomach that distends walls (mechanical) and presence of amino acids (chemical) from protein breakdown
Triggers short loop reflex in ENS
Causes release of HCl, gastrin, and pepsinogen
Increases gastric motility

67
Q

Describe the intestinal phase

A

Food leaves stomach and enters intestine
Carefully regulated
Stimulus is presence of glucose, fat, and acidic chyme in intestine
Decreases motility and inhibits stomach secretions
Performed by ENS and hormones secretin, CCK, and glucose-dependent insulinotropic peptide

Physiology 2130 (16 decks)

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