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
2
Q
two groups of organs
A
- alimentary canal
- accessory digestive organs
3
Q
alimentary canal (gastrointestinal or GI tract)
A
- digests and absorbs food
- mouth, pharynx, esophagus, stomach, small intestine, and large intestine
4
Q
accessory digestive organs
A
- teeth, tongue, gallbladder
- digestive glands:
- salivary glands
- liver
- pancreas
5
Q
digestive processes
A
- ingestion- eating
- propulsion- swallowing, peristalsis
- peristalsis- mechanical digestion
- chemical digestion- enzymes
- absorption
- defecation
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
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
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
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)
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
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
12
Q
mucosa lauer
A
- epithelium
- lamina propria
- muscularis mucosae
13
Q
muscularis externa
A
- longitudinal muscle
- circular muscle
14
Q
serosa
A
- epithelium
- connective tissue
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
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
17
Q
two enzymes in the mouth
A
- lingual lipase
- amylase
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
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
20
Q
muscularis externa: stomach layer
A
-longitudinal layer
-circular layer
-oblique layer**
3!!!
21
Q
pyloric sphincter
A
- between duodenum and stomach
- bottom of stomach
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
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
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
25
chief cell secretions: gastric gland secretion
- produce pepsinogen
- activated to pepsin by HCl and by pepsin itself (positive feedback mechanism)
- secrete lipases (fat digestion
26
enteroendocrine cells: gastric gland secretions
- 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*
27
mucosal barrier
- 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
28
why does your mouth suddenly go dry when you are about to deliver a presentation to a large crowd
- parasympathetic activity stimulates salivation
- parasympathetic activity inhibits salivation
- sympathetic activity stimulates salivation
- sympathetic activity inhibits salivation**
29
all of the following are part of the alimentary canal EXCEPT
- pharynx
- esophagus
- small intestine
- liver **
- mouth
30
___ involves over 22 muscles groups and includes the buccal phase and the pharyngeal esophageal phase
- mastication
- bolus formation
- deglutition**
- peristalsis
31
digestive processes in the stomach
- 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
32
neural reflex pathways
- 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
33
nerve response
- 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
34
response of the stomach filling
- 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
35
intestinal phase- stimulatory and inhibitory
- 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)
36
gastric contractile acitivty
- -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
37
stomach steps
- 1. propulsion- peristaltic waves move from the fundus towards the pylorus
- 2. grinding- the most vigorous peristalsis and mixing action occur close to the pylorus
- 3. 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
negative feedback
- as activity increases contractile force and rate of stomach emptying decline
- duodenal stimuli decline
39
vomiting (emesis)
- 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
the ___ cells are responsible for HCl production
- goblet-
- mucous
- parietal****- intrinsic
- chief- lipase, pepsinogen
41
stimuli that regulate gastrointestinal tract activity are generated by ____
- the CNS
- chemoreceptors in the gut
- the enteric nerve plexus
- all of the above****
- B and C only
42
phases of deglutition
- buccal- voluntary
| - pharyngeal-esophageal- involuntary
43
glands of the stomach
- mucous
- parietal
- chief
- goblet
44
neural reflex pathways
- cephalic
- gastric
- intestinal
45
small intestine: gross anatomy
- 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
duodenum
- 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
jejunum
-absorption
48
ileum
-vitamin absorption
49
structural modifications of small intestine
- increase surface area of proximal part for nutrient absorption
- circular folds
- villi- >villus epithelium
- microvilli
50
circular folds
force chyme to slowly spiral through lumen
51
villi
- motile fingerlike extensions
- villus epithelium:
- simple columnar absorptive cells (enterocytes)
- goblet cells
52
microvilli
- projections (brush border) of absorptive cells
- brush border enzymes (further breakdown of proteins and carbohydrates)
- immunoprotective- protect against pathogens
53
intestinal crypts
- 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
liver
- 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
bile
- 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
the gallbladder
- 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
pancreas
- 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
pancreatic juice
- watery alkaline solution (pH 8) neutralizes chyme
- electrolytes (primarily HCO3-)
- enzymes:
- proteases (trypsin)- proteins
- amylase- COH
- lipase- lipids
- nucleases- nucleic acids
59
mouth enzymes
- salivary amylase
| - starches to disaccharides
60
stomach enzyme: pepsin
-proteins to peptides
61
small intestine (from pancreas) enzymes
- amylase- continued breakdown of starch
- trypsin- continued breakdown of protein
- lipase- continued breakdown of fat
62
small intestine enzymes
- maltase, sucrase, lactase- disaccharides to monosaccharides
- peptidase- dipeptides to amino acids
63
regulation of bile and pancreatic secretions
- 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
regulation of bile and pancreatic secretion steps
- chyme entering duodenum causes release of cholecystokinin (CCK) and secretin from duodenal enteroendocrine cells
- 2. CCK and secretin enter the bloodstream
- 3. CCK induces secretion of enzyme rich pancreatic juice. secretin causes secretion of HCO3- rich pancreatic juice
- 4. bile salts and to a lesser extent secretion transported via bloodstream stimulate liver to produce bile more rapidly
- 5. CCK (via bloodstream) causes gallbladder to contract and hepatopancreatic sphincter to relax; bile enters duodenum
- 6. during cephalic and gastric phases, vagal nerve stimulation causes weak contractions of gallbladder
65
motility of the small intestine: segmentation
- 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
motility of the small intestine: peristalsis
- between meals
- occurs late in intestinal phase after absorption has occurs
- meal remnants, bacteria, and debris are moved to the large intestine
67
subdivisions of the small intestine
- duodenum
- jejunum
- ileum
68
this substance secreted by the pancreas helps neutralize chyme
- chymotrypsin
- bile
- trypsin
- bicarbonate***- alkaline
- CCK
69
which of the following enzymes digests lipids
- amylase
- lactase
- pepsin
- bile**
- none of the above* - lipase
70
large intestine (colon)
- 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
teniae coli
- large intestine
| - three bands of longitudinal smooth muscle in the muscularis
72
haustra
- large intestine
| - pocketlike sacs caused by the tone of the teniae coli
73
epiploic appendages
- large intestine
| - fat filled pouches which hang from large intestine
74
mesenteries of abdominal digestive organs
- omentum
- mesocolon
- mesentery
- membrane sheets that anchor the digestive tract
75
regions of large intestine
- cecum- pouch with attached appendix
- colon- ascending, transverse, descending, sigmoid
- rectum
- anal canal
76
rectum
- three rectal valves stop feces from being passes with gas
| - goblet cells- produce mucus
77
anal canal
- the last segment of the large intestine
| - superficial venous plexuses -> hemorrhoids
78
sphincters
- internal anal sphincter- smooth muscle- involuntary
| - external anal sphincter- skeletal muscle- voluntary
79
bacterial flora
- 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
functions of the large intestine
- 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
haustral contractions
- slow segmenting movements
| - occur every 30 min, move material from one haustrum to the next
82
mass movement
- slow intense peristalsis movements, 3-4/day
- usually after eating
- bulk fiber in diet strengthens colon contractions (diverticulosis)
83
defecation
- 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
chemical digestion and absorption of carbohydrates
- digestive enzymes:
- salivary amylase, pancreatic amylase, and brush border enzymes (dextrinase, glucoamylase, lactase, maltase, and sucrase)
85
lactose intolerant
- the undigested disaccharides create osmotic gradient that prevents water from being absorbed -> diarrhea
- treatment- add lactase enzyme
86
chemical digestion and absorption of proteins
- enzymes: pepsin in the stomach
- pancreatic proteases- trypsin, chymotrypsin, and carboxypeptidase
- brush border enzymes -aminopeptidases, carboxypeptidases, and dipeptidases
87
chemical digestion and absorption of lipids
- pre-treatment- emulsification by bile salts
- enzymes- pancreatic lipase
- absorption of glycerol and short chain fatty acids
88
malabsorption of nutrients
- 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
why is the small intestine well adapted for nutrient absorption
- 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
in terms of gastrointestinal function, the large intestines greatest contribution is
- 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
