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HAN 202 > Chapter 23 Digestive System > Flashcards

Chapter 23 Digestive System Flashcards

1
Q

digestion

A
  • to obtain energy for ATP production through food sources
  • raw material needed for building and repair
  • needs to be converted to cellular level
  • mechanical and chemical digestion
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2
Q

two groups of organs

A
  • alimentary canal

- accessory digestive organs

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3
Q

alimentary canal (gastrointestinal or GI tract)

A
  • digests and absorbs food

- mouth, pharynx, esophagus, stomach, small intestine, and large intestine

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4
Q

accessory digestive organs

A
  • teeth, tongue, gallbladder
  • digestive glands:
  • salivary glands
  • liver
  • pancreas
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5
Q

digestive processes

A
    1. ingestion- eating
    1. propulsion- swallowing, peristalsis
    1. peristalsis- mechanical digestion
    1. chemical digestion- enzymes
    1. absorption
    1. defecation
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6
Q

teeth: accessory digestive organs

A
  • teeth do much of mechanical work of digestion
  • human teeth include sharp incisors and cuspids which tear and grasp food
  • molar crush and grind
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7
Q

tongue: accessory digestive organs

A
  • -positioning and mixing of food
  • formation of the bolus
  • initiation of swallowing, speech, and taste
  • surface bears papillae for friction, licking, taste buds, secretes lingual lipase
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8
Q

salivary glands

A
  • intrinsic glands- are scattered in the oral mucosa -> keeps mouth moist
  • extrinsic- produce majority of saliva
  • functions:
  • cleanses the mouth
  • moistens and dissolves food chemicals
  • contains enzymes (salivary amylase) that begin the chemical breakdown of starch
  • contains chemicals (IgA antibodies and defenses) that protects against microorganisms
  • the brain stem sends impulses along parasympathetic fibers to activation secretions
  • sympathetic NS inhibits saliva production
  • ex. sublingual, submaxillary, parotid glands
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9
Q

digestive processes: mouth

A
  • ingestion
  • mechanical digestion- mastication is partly voluntary, partly reflexive
  • chemical digestion- salivary amylase and lingual lipase
  • absorption- only certain medications (blood vessels under the tongue) -> no nutrients
  • propulsion- deglutition (swallowing)
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10
Q

pharynx

A
  • oropharynx and laryngopharynx (nasopharynx no digestive role)
  • allow passage of food, fluids, and air
  • skeletal muscle layers: inner longitudinal, outer pharyngeal constrictors
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11
Q

histology of the alimentary canal

A
  • four basic layers (tunics) - from esophagus to anal canal
  • from inner to outer
  • mucosa- secretes mucous, enzymes and hormones, absorption and protection
  • submucosa- houses vessels, nerves and lymph vessels, made up of CT
  • muscularis externa- 2 layers of smooth MM (circular/longitudinal), responsible for segmentation and peristalsis
  • serosa- outermost layer, made up of CT
  • exception: in esophagus the adventia replaces the serosa layer
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12
Q

mucosa lauer

A
  • epithelium
  • lamina propria
  • muscularis mucosae
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13
Q

muscularis externa

A
  • longitudinal muscle

- circular muscle

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14
Q

serosa

A
  • epithelium

- connective tissue

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15
Q

esophagus

A
  • flat muscular tube from laryngopharynx to stomach
  • bolus of food (aided by mucous) travels through esophagus by smooth MM contractions- perstalsis
  • joins stomach at the cardiac orifice
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16
Q

deglutition (swallowing): buccal and pharyngeal-esophagus phase

A
  • involves the tongue, soft palate, pharynx, esophagus, and 22 muscles groups
  • buccal phase- voluntary contraction of the tongue, forces bolus into oropharynx
  • pharyngeal-esophageal phase:
  • involuntary
  • control center in the medulla and lower pons
  • all routes are blocked, soft palate blocks nasopharynx, epiglottis covers trachea
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17
Q

two enzymes in the mouth

A
  • lingual lipase

- amylase

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18
Q

peristalsis

A
  • peristalsis- adjacent segments of alimentary
  • tract organs alternately contract and relax
  • which moves food along the tract distally
  • video-fluoroscopy- examines how well a person carries out peristalsis
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19
Q

stomach: gross anatomy

A
  • cardial region (cardia)- surrounds the cardiac orifice
  • fundus- dome-shaped region beneath the diaphragm
  • body- midportion
  • pyloric region- pylorus is continuous with the duodenum through the pyloric valve (sphincter)
  • greater curvature- convex lateral surface
  • lesser curvature- concave medial surface
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20
Q

muscularis externa: stomach layer

A

-longitudinal layer
-circular layer
-oblique layer**
3!!!

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21
Q

pyloric sphincter

A
  • between duodenum and stomach

- bottom of stomach

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22
Q

stomach: microscopic anatomy

A
  • mucosa (lining of the stomach)
  • produces mucus which traps bicarbonate-rich fluid beneath it
  • gastric pits lead into gastric glands (produce stomach secretions)
  • enzymes in the pits to aid in digestion
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23
Q

gastric glands: cell types

A
  • cell types:
  • mucous neck cells- secrete thin acidic mucus
  • parietal cells- secrete HCl and intrinsic factor
  • chief cells- pepsinogen
  • enteroendocrine cells (g cells)- gastrin
  • 3 liters of gastric juice daily
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24
Q

gastric gland secretions

A
  • glands in the fundus and body produce most of the gastric juice
  • parietal cell secretions
  • HCl- pH 1.5-3.5- denatures protein in food, activates pepsin, and kills many bacteria
  • intrinsic factor- protein required for absorption of vitamin B12 in small intestine
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25
Q

chief cell secretions: gastric gland secretion

A
  • produce pepsinogen
  • activated to pepsin by HCl and by pepsin itself (positive feedback mechanism)
  • secrete lipases (fat digestion
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26
Q

enteroendocrine cells: gastric gland secretions

A
  • lower portion of gastric pit
  • paracrine (act locally)- serotonin and histamine
  • hormones- somatostatin and gastrin (g cells) (regulates secretions and mobility)
  • gastric secretion is controlled by both neural and normal mechanisms*
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27
Q

mucosal barrier

A
  • layer of bicarbonate rich mucus
  • tight junctions between epithelial cells
  • damaged epithelial cells are quickly replaced by division of stem cells
  • peptic or gastric ulcers: erosion of the stomach wall- most are caused by H pylori bacteria (imbalance)
  • stomach enzymes are strong enough to digest the stomach -> ulcers
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28
Q

why does your mouth suddenly go dry when you are about to deliver a presentation to a large crowd

A
  • parasympathetic activity stimulates salivation
  • parasympathetic activity inhibits salivation
  • sympathetic activity stimulates salivation
  • sympathetic activity inhibits salivation**
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29
Q

all of the following are part of the alimentary canal EXCEPT

A
  • pharynx
  • esophagus
  • small intestine
  • liver **
  • mouth
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30
Q

___ involves over 22 muscles groups and includes the buccal phase and the pharyngeal esophageal phase

A
  • mastication
  • bolus formation
  • deglutition**
  • peristalsis
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31
Q

digestive processes in the stomach

A
  • physical digestion (3 layers of muscle)
  • denaturation of proteins (HCl)
  • enzymatic digestion of proteins by pepsin
  • secretes intrinsic factor required for absorption of vitamin B12
  • lack of intrinsic factor -> pernicious anemia
  • delivers chyme (product of its activity) to the small intestine
  • bolus -> chyme
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32
Q

neural reflex pathways

A
  • control of digestive activity are both intrinsic and extrinsic
  • cephalic phase- initiated by stimuli arising inside or outside the GI tract and involved CNS centers
  • gastric phase- mediated inside GI tract by local stimuli (local distention, pH, presence of substrates)
  • 3-4 hours after food enters stomach
  • intestinal phase- controls rate of emptying into intestines
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33
Q

nerve response

A
  • cephalic phase
  • external stimuli
  • CNS and extrinsic autonomic nerves activate
  • local (intrinsic) nerve plexus
  • effectors- smooth muscle or glands
  • response- change in contractile or secretory activity
  • vagus nerve stimulation
  • gastric phase- stomach distension -> stretch receptors, g-cells -> gastrin
  • intestinal phase- negative feedback with too much coming in from the stomach
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34
Q

response of the stomach filling

A
  • stretches to accommodate incoming food
  • reflex-mediated receptive relaxation- coordinated by the swallowing center of the brain stem
  • gastric accommodation- plasticity (stress-relaxation response) of smooth muscle, can stretch without contracting
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35
Q

intestinal phase- stimulatory and inhibitory

A
  • stimulatory- brief filling of initial part of small intestine of partially digested food
  • inhibitory- enterogastric reflex- a trio of reflexes that puts brakes on gastric activity to protect small intestine from excessive acidity
  • dumping syndrome- seen in stomach volume reduction surgeries (nausea/vomiting)
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36
Q

gastric contractile acitivty

A
  • -peristaltic waves move towards the pylorus
  • basic electrical rhythm (BER) initiated by pacemaker cells (cells of cajal)
  • distension (stretch receptors) and gastrin increase force of contraction (peristalsis)
  • most vigorous near the pylorus
  • chyme is either:
  • delivered in about 3 ml spurts to the duodenum (small amount but continuous)
  • forced backward into the stomach
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37
Q

stomach steps

A
    1. propulsion- peristaltic waves move from the fundus towards the pylorus
    1. grinding- the most vigorous peristalsis and mixing action occur close to the pylorus
    1. retropulsion- the pyloric end of the stomach acts as a pump that delivers small amount of chyme into the duodenum, simultaneously forcing most of its contained material backward into the stomach
38
Q

negative feedback

A
  • as activity increases contractile force and rate of stomach emptying decline
  • duodenal stimuli decline
39
Q

vomiting (emesis)

A
  • protective reflex
  • removes toxic material from GI tract before being absorbed
  • triggered by extreme stretching of stomach or irritant such as bacteria, excessive alcohol, spicy foods and certain drugs
  • vomiting reflex located in medulla (emetic center)
  • prior nausea, diaphragm and abdominal muscles contract increasing intra-abdominal pressure, gastroesophageal sphincter relaxes, contents are forced out of stomach
40
Q

the ___ cells are responsible for HCl production

A
  • goblet-
  • mucous
  • parietal**- intrinsic
  • chief- lipase, pepsinogen
41
Q

stimuli that regulate gastrointestinal tract activity are generated by ____

A
  • the CNS
  • chemoreceptors in the gut
  • the enteric nerve plexus
  • all of the above**
  • B and C only
42
Q

phases of deglutition

A
  • buccal- voluntary

- pharyngeal-esophageal- involuntary

43
Q

glands of the stomach

A
  • mucous
  • parietal
  • chief
  • goblet
44
Q

neural reflex pathways

A
  • cephalic
  • gastric
  • intestinal
45
Q

small intestine: gross anatomy

A
  • major organ of digestion and absorption
  • 2-4 m long; from pyloric sphincter to ileocecal valve (6-7 m long in cadaver- height of 2 story building)
  • subdivisions:
  • duodenum- chemical digestion
  • jejunum- absorption
  • ileum- vitamin absorption
46
Q

duodenum

A
  • chemical digestion
  • the bile duct and main pancreatic duct
  • join at the hepatopancreatic ampulla
  • enter the duodenum at the major duodenal papilla
  • hepatopancreatic sphincter controls entry of bile and pancreatic juice
47
Q

jejunum

A

-absorption

48
Q

ileum

A

-vitamin absorption

49
Q

structural modifications of small intestine

A
  • increase surface area of proximal part for nutrient absorption
  • circular folds
  • villi- >villus epithelium
  • microvilli
50
Q

circular folds

A

force chyme to slowly spiral through lumen

51
Q

villi

A
  • motile fingerlike extensions
  • villus epithelium:
  • simple columnar absorptive cells (enterocytes)
  • goblet cells
52
Q

microvilli

A
  • projections (brush border) of absorptive cells
  • brush border enzymes (further breakdown of proteins and carbohydrates)
  • immunoprotective- protect against pathogens
53
Q

intestinal crypts

A
  • intestinal crypt epithelium (like gastric pits)
  • secretory cells- product intestinal juice (peptidase, maltase, lactase, sucrase)
  • enteroendocrine cells- (not to be confused with enteroendocrine of stomach) -> secretin and cholecystokinin (CCK)
  • lymphocytes- t cells that release cytokines that kill infected cells
  • Paneth cells- secrete antimicrobial agents (defensins and lysozyme)
  • stem cells- dividing cells which become specialized
54
Q

liver

A
  • largest gland in the body (3 ibs)
  • four lobes
  • functions:
  • stores glycogen and vitamins (fat soluble)
  • detox of ammonia
  • produces bile
  • exceptional regenerative capacity of liver, can regenerate to former size in 6-12 months
  • this is why live donor transplants are a viable option
55
Q

bile

A
  • missing ingredient to attack fatty foods, contains:
  • bile salts- cholesterol derivatives that function in fat emulsification and absorption
  • bilirubin- waste product from heme
  • facilitate fat and cholesterol absorption
56
Q

the gallbladder

A
  • thin walled muscular green sac on the ventral surface of the liver
  • stores and concentrates bile
  • releases bile via the cystic duct, which flow into the bile duct
  • bile extracts cholesterol from body, if too much cholesterol it crystallizes forming gallstones
57
Q

pancreas

A
  • endocrine function- secrete insulin and glucagon
  • exocrine function:
  • secrete pancreatic juice
  • pancreatic juice consisting of enzymes for digestion (digests carbohydrates, fats, proteins)
  • pancreatic juice consisting of bicarbonate ions (neutralizes chyme)
58
Q

pancreatic juice

A
  • watery alkaline solution (pH 8) neutralizes chyme
  • electrolytes (primarily HCO3-)
  • enzymes:
  • proteases (trypsin)- proteins
  • amylase- COH
  • lipase- lipids
  • nucleases- nucleic acids
59
Q

mouth enzymes

A
  • salivary amylase

- starches to disaccharides

60
Q

stomach enzyme: pepsin

A

-proteins to peptides

61
Q

small intestine (from pancreas) enzymes

A
  • amylase- continued breakdown of starch
  • trypsin- continued breakdown of protein
  • lipase- continued breakdown of fat
62
Q

small intestine enzymes

A
  • maltase, sucrase, lactase- disaccharides to monosaccharides
  • peptidase- dipeptides to amino acids
63
Q

regulation of bile and pancreatic secretions

A
  • chyme entering duodenum releases: secretin and cholecystokinin (CCK)
  • CCK- induces secretion of pancreatic juice (enzymes) and causes gallbladder to contract
  • secretin- secretion of watery bicarbonate rich pancreatic juice
  • bile secretion is stimulated by bile salts
64
Q

regulation of bile and pancreatic secretion steps

A
  • chyme entering duodenum causes release of cholecystokinin (CCK) and secretin from duodenal enteroendocrine cells
    1. CCK and secretin enter the bloodstream
    1. CCK induces secretion of enzyme rich pancreatic juice. secretin causes secretion of HCO3- rich pancreatic juice
    1. bile salts and to a lesser extent secretion transported via bloodstream stimulate liver to produce bile more rapidly
    1. CCK (via bloodstream) causes gallbladder to contract and hepatopancreatic sphincter to relax; bile enters duodenum
    1. during cephalic and gastric phases, vagal nerve stimulation causes weak contractions of gallbladder
65
Q

motility of the small intestine: segmentation

A
  • segmentation (massaging) after a meal
  • mixes and moves contents slowly and steadily toward the ileocecal valve
  • intensity is altered by long and short reflexes
66
Q

motility of the small intestine: peristalsis

A
  • between meals
  • occurs late in intestinal phase after absorption has occurs
  • meal remnants, bacteria, and debris are moved to the large intestine
67
Q

subdivisions of the small intestine

A
  • duodenum
  • jejunum
  • ileum
68
Q

this substance secreted by the pancreas helps neutralize chyme

A
  • chymotrypsin
  • bile
  • trypsin
  • bicarbonate***- alkaline
  • CCK
69
Q

which of the following enzymes digests lipids

A
  • amylase
  • lactase
  • pepsin
  • bile**
  • none of the above* - lipase
70
Q

large intestine (colon)

A
  • shorter but wider than small intestine
  • major digestive function is to absorb remaining water
  • stores indigestible food
  • houses good bacteria
  • no digestive enzymes, minimal absorption
  • takes 12-24 hours to move through large intestine
71
Q

teniae coli

A
  • large intestine

- three bands of longitudinal smooth muscle in the muscularis

72
Q

haustra

A
  • large intestine

- pocketlike sacs caused by the tone of the teniae coli

73
Q

epiploic appendages

A
  • large intestine

- fat filled pouches which hang from large intestine

74
Q

mesenteries of abdominal digestive organs

A
  • omentum
  • mesocolon
  • mesentery
  • membrane sheets that anchor the digestive tract
75
Q

regions of large intestine

A
  • cecum- pouch with attached appendix
  • colon- ascending, transverse, descending, sigmoid
  • rectum
  • anal canal
76
Q

rectum

A
  • three rectal valves stop feces from being passes with gas

- goblet cells- produce mucus

77
Q

anal canal

A
  • the last segment of the large intestine

- superficial venous plexuses -> hemorrhoids

78
Q

sphincters

A
  • internal anal sphincter- smooth muscle- involuntary

- external anal sphincter- skeletal muscle- voluntary

79
Q

bacterial flora

A
  • located in colon
  • ferment indigestible carbohydrates
  • release irritating acids and gases
  • 500 ml of gas is produced each day, more with carbohydrate rich food (Beans)
  • synthesize B complex vitamins and vitamin K (needed by the liver to produce clotting proteins
80
Q

functions of the large intestine

A
  • vitamins, water, and electrolytes are reclaimed
  • major function is propulsion of faces towards the anus
  • colon is not essential for life bc everything is already digested and absorbed
81
Q

haustral contractions

A
  • slow segmenting movements

- occur every 30 min, move material from one haustrum to the next

82
Q

mass movement

A
  • slow intense peristalsis movements, 3-4/day
  • usually after eating
  • bulk fiber in diet strengthens colon contractions (diverticulosis)
83
Q

defecation

A
  • mass movements force feces into rectum
  • distension initiates spinal defecation reflex
  • parasympathetic signals:
  • stimulate contraction of the sigmoid colon and rectum
  • relax the internal anal sphincter
  • conscious control allows relaxation of external anal sphincter
84
Q

chemical digestion and absorption of carbohydrates

A
  • digestive enzymes:
  • salivary amylase, pancreatic amylase, and brush border enzymes (dextrinase, glucoamylase, lactase, maltase, and sucrase)
85
Q

lactose intolerant

A
  • the undigested disaccharides create osmotic gradient that prevents water from being absorbed -> diarrhea
  • treatment- add lactase enzyme
86
Q

chemical digestion and absorption of proteins

A
  • enzymes: pepsin in the stomach
  • pancreatic proteases- trypsin, chymotrypsin, and carboxypeptidase
  • brush border enzymes -aminopeptidases, carboxypeptidases, and dipeptidases
87
Q

chemical digestion and absorption of lipids

A
  • pre-treatment- emulsification by bile salts
  • enzymes- pancreatic lipase
  • absorption of glycerol and short chain fatty acids
88
Q

malabsorption of nutrients

A
  • gluten sensitive enteropathy (celiac disease)
  • gluten damages the intestinal villi and brush border
  • results in bloating, diarrhea, pain and malnutrition
  • treated by eliminating gluten from the diet (all grains but rice and corn)
89
Q

why is the small intestine well adapted for nutrient absorption

A
  • alkaline secretion from the stomach are neutralized in the duodenum
  • bile is released from the duodenum to promote liver and pancreatic secretion
  • large surface are due to the presence of the villi, and microvilli
  • due to the 3 muscular walls for grinding
  • all of the above
90
Q

in terms of gastrointestinal function, the large intestines greatest contribution is

A
  • exposing the chyme to the rich assortment of pancreatic enzymes through the process of segmentation
  • absorption of all primary nutrients
  • absorption of water
  • regulation of gastric motility
  • all of the above

HAN 202 (16 decks)

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