Lessons 15-17 Flashcards
1
Q
digestive system
A
organ system that processes food, extract nutrients, and eliminates residue
2
Q
what are the five stages of digestion
A
- ingestion
- digestion
- absorption
- compaction
- defecation
3
Q
five stages of digestion: ingestion
A
selective intake of food
4
Q
five stages of digestion: digestion
A
mechanical and chemical breakdown of food into a form usable by the body
5
Q
five stages of digestion: absorption
A
uptake of nutrient molecules into the epithelial cells of the digestive tract and then into the blood and lymph
6
Q
five stages of digestion: compaction
A
absorbing water and consolidating the indigestible residue into feces
7
Q
five stages of digestion: defecation
A
elimination of feces
8
Q
mechanical digestion
A
physical breakdown of food into smaller particles
9
Q
what are two examples of mechanical digestion
A
- cutting and grinding action of the teeth
- churning action of stomach and small intestine
10
Q
what is the purpose of mechanical digestion
A
exposes more food surface to digestive enzymes
11
Q
chemical digestion
A
a series of hydrolysis reactions that breaks dietary macromolecules into their monomers
12
Q
what carries out chemical digestion
A
digestive nzymes produced by salivary glands, stomach, pancreas, and small intestine
13
Q
what are the four main breakdowns of that occur in chemical digestion
A
- polysaccharides to monosaccharides
- proteins into amino acids
- fats into monoglycerides and fatty acids
- nucleic acids into nucleotides
14
Q
what nutrients are ingested as usable material
A
- vitamins
- amino acids
- minerals
- cholesterol
- water
15
Q
what are the two subdivisions of the digestive system
A
- digestive tract
- accessory organs
16
Q
digestive tract
A
- 30ft long muscular tube extending from mouth to anus
- mouth, pharynx, esophagus, stomach, small and large intestine
17
Q
accessory organs of the digestive system
A
- teeth
- tongue
- salivary glands
- liver
- gallbladder
- pancreas
18
Q
what are the four layers of the digestive tract innermost to outermost?
A
- mucosa
- submucosa
- muscularis externa
- serosa
19
Q
what are the three layers of the mucosa?
A
- epithelium
- lamina propria
- muscularis mucosae
20
Q
what are the two layers of the muscularis external?
A
- inner circular layer
- outer longitudinal layer
21
Q
what are the two layers of the serosa?
A
- areolar tissue
- mesothelium
22
Q
mucosa of the digestive tract layers
A
lines the lumen
23
Q
the epithelium of the mucosa what kind of tissue for most of the digestive tract
A
simple columnar
24
Q
where is the mucosa not simple columnar tissue? what is it instead?
A
- mouth through esophagus and the lower anal canal
- stratified squamous
25
lamina propria of mucosa
loose connective tissue layer
26
muscularis mucosae of mucosa
- thin layer of smooth muscle
- improves efficiency of digestion and nutrient absorption
27
how does the muscularis mucosae improve digestion and nutrient absorption efficiency
tenses mucosa creating grooves and ridges that enhance surface area and contact with food
28
mucosa-associated lymphatic tissue
- abundant in the mucosa
- included lymphocytes and lymph nodes
29
submucosa of the digestive tract layers
- thicker layer of loose connective tissue
- contains blood and lymphatic vessels, a nerve plexus, and in some spots mucous secreting glands that dump lubricating mucus in the lumen
30
____ extends into the submucosa in some parts of the GI tract
MALT
31
inner circular smooth layer of the muscularis externa
- cells encircle tract
- responsible for the motility that propels food and residue through the tract
32
in some places the inner circular layer of the muscularis externa the layer thickens to form what?
valves that regulate the passage of material through the tract
33
serosa layer of the digestive tract is composed of
a thin layer of areolar tissue topped by simple squamous mesothelium
34
where does the serosa begin?
in the lower 3-4 cm of the esophagus and ends just before the rectum
35
some organs do not have serosa. what are they covered with instead?
adventitia
36
adventitia
fibrous connective tissue layer that binds and blends into adjacent organs
37
what parts of the digestive tract have adventitia rather than serosa
- pharynx
- most of the esophagus
- rectum
38
enteric plexus
nervous network in esophagus, stomach, and intestines that regulates digestive tract motility, secretion, and blood flow
39
innervation of the enteric plexus
- can function independently of CNS but it usually exerts influence on its action
- often considered part of ANS
- two networks of neurons
- sensory neurons included
40
what are the two networks of neurons that make up the enteric plexus
- submucosal plexus
- myenteric plexus
41
submucosal plexus
- found in submucosa
- controls glandular secretions of mucosa and movements of muscularis mucosae
42
myenteric plexus
- ganglia and nerve fibers between the two layers of the muscularis externa
- controls peristalsis and other contractions of muscularis externa
43
what do the sensory neurons in the enteric plexus do?
monitor tension in gut wall and conditions in lumen
44
mesentery
connective tissue sheet that suspends stomach and intestines from abdominal wall
45
the looseness of the mesentery allows for what to occur?
the stomach and intestines to undergo strenuous contractions with freedom of movement in the abdominal cavity
46
what are the functions of the mesentery (3)
- hold abdominal viscera in proper relationship to each other
- prevent intestines from becoming twisted and tangled by changes in body position and by their own contractions
- provide passage of blood/lymphatic vessels and nerves that supply the digestive tract
47
intraperitoneal
when an organ is enclosed by mesentery (serosa) on all sides
48
which organs are considered intraperitoneal?
- stomach
- liver
- jejunum and ileum of small intestine
- appendix, cecum, transverse, and sigmoid colon of large intestine
49
retroperitoneal
- when an organ lias against the posterior body wall and is covered by peritoneum on its anterior side only
- considered outside the peritoneal cavity
50
what organs are considered retroperitoneal?
- duodenum
- pancreas
- ascending colon, descending colon, and rectum of large intestine
51
what controls the motility and secretion of the digestive tract? (3)
neural, hormonal, and paracrine mechanisms
52
neural controls of the digestive tract (2)
- short (myenteric) reflexes
- long (vagovagal) reflexes
53
short (myenteric) reflexes
- stretch or chemical stim acts through myenteric plexus
- stims peristatic contractions of swallowing
54
long (vagovagal) reflexes
parasympathetic stim of digestive motility and secretion
55
what are two hormones secreted in the blood that stimulate parts of the digestive tract?
- gastrin
- secretin
56
paracrine secretions stimulate
nearby target cells
57
the mouth is aka (2)
- the oral cavity
- buccal cavity
58
functions of the mouth (4)
- ingestion
- taste and other sensory responses to food
- chewing and chemical digestion
- swallowing, speech, and respiration
59
functions of the cheek and lips (3)
- retain food and push it between the teeth
- involved in speech
- essential for sucking and blowing actions (suckling)
60
tongue
muscular, bulky, but agile and sensitive organ of the mouth
61
functions of the tongue
- manipulate food between teeth
- senses taste and texture of food
62
lingual papillae
bumps and projections that are the sites of most taste buds
63
body of the tongue
- anterior two-thirds of tongue
- occupies the oral cavity
64
root of the tongue
- posterior one third of the tongue
- occupies the oropharynx
65
vallate papillae
a v-shaped row of papillae that mark the boundary between the body and root of the tongue
66
intrinsic muscles of the tongue
- entirely contained in tongue
- produce subtle tongue movements of speech
67
extrinsic muscles of tongue
- with attachments outside of tongue
- produce stronger movements of food manipulation
68
lingual glands
- serous and mucous glands within tongue amid the extrinsic muscles
- secrete a portion of the saliva
69
lingual tonsils contained where?
in the root of the tongue
70
the palate functions (2)
- separates oral cavity from nasal cavity
- makes it possible to breathe while chewing food
71
hard palate
anterior portion that is supported by the palatine processes of the maxillae and the palatine bones
72
palatine rugae
transverse ridges that help the tongue hold and manipulate food
73
soft palate
posterior to hard palate with more spongy texture
74
uvula
- conical medial projection visible at the rear of the mouth
- helps retain food in the mouth until one is ready to swallow
75
how many adult teeth are there?
32
76
teeth are collectively called
the dentition
77
functions of the teeth (4)
- function to break food into smaller pieces
- makes food easier to swallow
- exposes more surface area for action of digestive enzymes
- speedy chemical digestion
78
mastication
- breaks food into smaller pieces to be swallowed and exposes more surface to digestive enzymes
- first step in mechanical digestion
79
how does mastication occur? (3)
- food stims oral receptors that trigger an involuntary chewing reflex
- tongue and other muscles in oral cavity manipulate food
- masseter and temporalis elevate the lower teeth to crush food
80
functions of saliva (6)
- moistens mouth
- begins starch and fat digestion
- cleanses teeth
- inhibits bacterial growth
- dissolves molecules so they can stim the taste buds
- moistens food and binds it together into a soft mass to aid in swallowing
81
saliva is a _____ solution of _____ water
- hypotonic
- 97-99.5%
82
what is the pH of saliva?
6.8-7
83
what are the solutes found in saliva? (6)
- mucus
- electrolytes
- lysozymes
- IgA
- salivary amylase
- lingual lipase
84
mucus in saliva
binds and lubricates a mass of food and aids in swallowing
85
electrolytes of saliva
slats of Na+, K+, Cl-, phosphate, and bicarbonate
86
lysozymes of saliva
enzyme that kills bacteria
87
IgA of saliva
antimicrobial antibody
88
salivary amylase of saliva
enzyme that begins starch digestion in the mouth
89
lingual lipase of saliva
enzyme that begins fat digestion in the mouth (mainly after food is swallowed)
90
what are the two types of salivary glands
- intrinsic (minor) salivary glands
- extrinsic (major) salivary glands
91
intrinsic (minor) salivary glands
- small glands dispersed amid other oral tissues
- secrete saliva at constant rate whether eating or not
92
extrinsic (major) salivary glands
three pairs of larger, more discrete organs connected to oral cavity by ducts
93
what are the three major salivary glands?
- parotid glands
- submandibular glands
- sublingual glands
94
parotid glands are located where?
beneath the skin anterior to the earlobe
95
submandibular glands are located where?
halfway along the body of the mandible
96
sublingual glands are located where?
in the floor of the mouth
97
the sublingual glands have several ducts that empty where?
posterior to the papilla of the submandibular duct
98
extrinsic salivary glands secrete about ___ of saliva a day
1-1.5 liters
99
______ respond to signals generated by presence of food
salivary nuclei in medulla oblongata and pons
100
salivary nuclei are excited by what?
tactile, pressure, and taste receptors
101
salivary nuclei receive input from higher brain centers. explain why.
odor, sight, or thought of food stims salivation
102
salivary glands send signals by way of what kind of fibers via what two nerves.
- autonomic fiber
- facial and glossopharyngeal nerves
103
parasympathetic fibers of the salivary nuclei
stim the glands to produce an abundance of thin, enzyme-rich saliva
104
sympathetic fibers of salivary nuclei
stims the glands to produce less, and thicker saliva with more mucus
105
pharynx
- muscular funnel connecting oral cavity to esophagus and nasal cavity to larynx
- where digestive and respiratory tracts intersect
106
what are the two layers of muscle within the pharynx
- deep longitudinal skeletal muscle
- superficial circular skeletal muscle
107
what is the function of the superficial circular muscle layer of the pharynx
forms the pharyngeal constrictors that force food downward during swallowing
108
how many pharyngeal constrictors are there and what are they called?
- 3
- superior, middle, inferior
109
when not swallowing what is the inferior constrictor doing? this constrictor is aka
- contracted to exclude air from the esophagus
- upper esophageal sphincter
110
esophagus
straight muscular tube 25-30 cm long between pharynx and stomach
111
the esophagus extends from
pharynx to cardiac orifice of stomach passing through esophageal hiatus in diaphragm
112
lower esophageal sphincter (LES)
- inferior end of esophagus
- prevents stomach contents from regurgitating into the esophagus and protects esophageal mucosa form erosive stomach acid
113
heartburn
burning sensation produced by acid reflux into the esophagus
114
deglutition
- complex action involving over 22 muscles in the mouth, pharynx, and esophagus
- swallowing
- coordinated by swallowing center
115
swallowing center
- pair of nuclei in medulla oblongata
- communicates with muscles of the pharynx and esophagus
116
what are the three phases of swallowing
- oral phase
- pharyngeal phase
- esophageal phase
117
oral phase of swallowing
- voluntary control
- tongue forms food bolus by pressing food into hard palate and the pushes it into laryngopharnyx
118
pharyngeal phase of swallowing
- involuntary control
- palate, tongue, vocal cords, and epiglottis block the oral and nasal cavities and airway while pharyngeal constrictors push the bolus into the esophagus
119
what is the role of the epiglottis in the oral phase of swallowing
it tips posteriorly to allow food to go into the laryngopharynx without traveling into the larynx
120
what is the purpose of the pharyngeal phase of swallowing
prevents food and drink from reentering mouth or entering the nasal cavity
121
esophageal phase of swallowing
peristalsis drives bolus downward and relaxation of the lower esophageal sphincter admits it into the stomach
122
peristalsis
circular muscle constricts above bolus, relaxes below bolus
123
when food and liquid is swallowed upright what happens
drops through esophagus by gravity faster than peristalsis can keep up with it
124
stomach
muscular sac in upper left abdominal cavity immediately inferior to diaphragm
125
functions of the stomach
- food storage
- mechanically breaks up food particles, liquefies the food, and begins chemical digestion of proteins and fat
126
chyme
- the result of the stomach breaking down materials
- acidic, soupy mixture of semi-digested food that passes on to the small intestine
127
what are the four regions of the stomach
- cardiac part
- fundic region (fundus)
- body
- pyloric part
128
cardiac part of stomach
- small area within about 3 cm of the cardiac orifice
- entry point of material from esophagus
129
fundic regions (fundus) of the stomach
dome superior to the esophageal attachment
130
body of the stomach
makes up greatest part of distal to cardiac orifice
131
pyloric part of stomach
- narrower pouch at inferior end
- subdivided into the antrum and the pyloric canal that terminates at the pylorus
132
pylorus
narrow passage to duodenum
133
pyloric sphincter
- ring of smooth muscle around pylorus
- regulates the passage of chyme into the duodenum
134
describe the mucosa of the stomach
- covered with simple columnar epithelium
- apical region are filler with mucin
135
how does mucin become mucus
swells with water
136
what do the mucosa and the submucosa look like when the stomach is full? empty?
- flat when full
- have longitudinal gastric rugae
137
the muscularis externa of the stomach has ___ layers. everywhere else has ___ layers.
- three
- two
138
what are the three layers of the muscularis externa in the stomach
- outer longitudinal
- middle circular
- inner oblique
139
what cell types can be found in the stomach mucosa?
- mucous cells
- regenerative (stem) cells
- parietal cells
- chiefs cells
- enteroendocrine cells
140
mucous cells in stomach
secrete mucus
141
regenerative (stem) cells of stomach
divide rapidly and produce continual supply of new cells to replace cells that die
142
parietal cells of stomach
secrete hydrochloric acid, intrinsic factor, and ghrelin
143
ghrelin
stimulates hunger feeling
144
chief cells of the stomach
- most numerous cell type
- secrete gastric lipase and pepsinogen
145
enteroendocrine cells of stomach
secrete hormones and paracrine messengers that regulate digestion
146
gastric pits of the gastric mucosa
depressions in gastric mucosa lined with the same columnar epithelium as the surface
147
gastric juice
- 2-3L per day produced by the gastric glands
- mainly a mixture of water, HCl and pepsin
148
functions of the HCl (3)
- activates pepsin and lingual lipase
- breaks up connective tissues and plant cell walls helping to liquify food and form chyme
- contributes to innate immunity by destroying most ingested pathogens
149
pepsin
- released by chief cells as the inactive form pepsinogen
- digests dietary proteins into shorter peptides
150
how is pepsin activated
HCl removes some of the amino acids from pepsinogen to form pepsin
151
autocatalytic effect in pepsin
as some pepsin is formed it converts more pepsinogen into more pepsin
152
the digestion of proteins is incomplete in the stomach. where does it finish?
in the small intestine
153
gastric lipase
- released from chief cells
- plays a minor role with lingual lipase in the digestion of dietary fats
- digests 10-15% of dietary fats in stomach
154
where is most all fat digested?
small intestine
155
intrinsic factor
- glycoprotein secreted by parietal cells
- essential to absorption of B12 by small intestine
156
how does intrinsic factor help in the absorption of B12?
binds B12 and then intestinal cells absorb this complex by receptor-mediated endocytosis
157
B12 is needed to synthesize
hemoglobin
158
pernicious anemia
anemia caused by a deficiency of B12
159
____ is the only indispensable function of the stomach
secretion of intrinsic factor
160
will digestion continue if the stomach is removed?
yes but B12 supplements will be needed
161
most of the chemical messengers that are released by cells in the gastric and pyloric glands are...
hormones that enter blood and stim distant cells
162
gut brain peptide
- peptides produced in both the digestive tract and the CNS
- most of the hormones that enter blood as chemical messengers
163
what are the gut-brain peptides? (6)
- substance P
- vasoactive peptide (VIP)
- secretin
- gastric inhibitory peptide (GIP)
- cholecystokinin (CCK)
- neuropeptide Y (NPY)
164
what is the mechanism of gastric motility (4)
- food stims mechanoreceptors in pharynx and transmits signals in medulla during swallowing
- swallowing center of medulla signals stomach to relax
- vagus nerve relays message form medulla and activates receptive-relaxation response in stomach
- soon rhythm of peristalsis starts in stomach
165
what controls peristalsis in stomach
enteric pacemaker cells in longitudinal layer of muscularis externa
166
describe peristalsis in the stomach
- ring of constriction every 20 sec and becomes stronger contraction at pyloric part
- eventually very strong after 30 min
167
what is the function of peristalsis in the stomach
churn the food to mix it with gastric juice
168
____ acts as a pump that breaks up semi-digested food and prepares it for the intestine
thick muscularis of antrum
169
only about ___ of chyme is released into the duodenum at a time
3 ml
170
why is there such a small amount of chyme released into the duodenum
- neutralize the stomach acid
- digest nutrients little by little
171
if duodenum is overfilled what happens?
gastric motility is inhibited
172
a typical meal emptied form stomach in ___
4 hours
173
what can cause a meal to empty from the stomach quicker? slower?
- less time if meal is more liquid
- a high fat meal can take as long as 6 hours
174
vomiting
- forceful ejection of stomach and intestinal contents form the mouth
- usually preceded by nausea and retching
175
retching
thoracic expansion and abdominal contraction creating a pressure difference that dilates the esophagus and forced open the upper esophageal sphincter
176
vomiting involves the ___ in the medulla
emetic center
177
emetic center
- in the medulla
- integrates strong abdominal contractions combined with reverse peristalsis of gastric antrum and duodenum
178
vomiting is indued by (4)
- overstretching of stomach or duodenum
- chemical irritants such as alcohol and bacterial toxins
- visceral trauma
- intense pain or psychological and sensory stim
179
____ and ____ partially digest protein and lesser amounts of starch and fat in the stomach
salivary and gastric enzyme
180
most digestion and nearly all absorption occurs where in the body?
small intestine
181
while the stomach does not absorb significant amounts of nutrients what does it absorb?
aspirin and some lipid-soluble drugs
182
alcohol is absorbed mainly by
small intestine
183
what does the intoxicating feeling of alcohol consumption depend on?
how rapidly the stomach is emptied
184
what three ways is the stomach protected from the acidic environment it creates
- mucous coat
- tight junctions
- epithelial cell replacement
185
mucous coat as a way to protect the stomach
thick highly alkaline mucus resists action of acid and enzymes
186
tight junctions as a way to protect the stomach
- between epithelial cells
- prevent gastric juice from seeping between them and digesting deeper tissue
187
epithelial cell replacement as a way to protect the stomach
- cells live only 3-6 days
- sloughed off in chyme and digested with food
- replaced rapidly by cell division in gastric pits
188
what happens if the protective measures of the stomach are broken down
inflammation and peptic ulcer
189
gastritis
inflammation of the stomach and can lead to peptic ulcer
190
peptic ulcer
pepsin and HCl eroding the stomach wall
191
most ulcers are caused by
acid resistant bacteria helicobacter pylori
192
ulcers causes by H pylori can be treated with
antibiotic and pepto
193
risk factors for ulcer development
- psychological factors
- hypersecretion of acid
- smoking
- use of aspirin and other nonmedical anti-inflammatory drugs
194
when there is a hypersecretion of acid in the stomach to cause ulcers ___ is sometimes involved
pepsin
195
gastric secretion and motility are regulated by
nervous and endocrine system
196
gastric secretion and motility increase ____
when food is eaten
197
what are the three phases of gastric activity
- cephalic phase
- gastric phase
- intestinal phase
198
cephalic phase of gastric activity
- stomach being controlled by brain
- vagus nerve stims gastric secretion even before food is swallowed (smell, thought, sight)
199
gastric phase of gastric activity
- stomach controlling itself
- food stretches stomach and activates myenteric and vagovagal reflexes which stims gastric secretion
200
intestinal phase of gastric activity
- stomach being controlled by small intestine
- intestinal gastrin briefly stims stomach but then secretin CCK, and enterogastric reflex inhibit gastric secretion/motility
201
___ and ___ also stim acid and enzyme secretion in the gastric phase of gastric activity
histamine and gastrin
202
___ suppresses gastric activity while ____ of the stomach is now inhibited
- sympathetic nerve fibers
- vagal (parasympathetic) stim
203
what is the nervous system work of the cephalic phase?
- sensory and mental inputs converge on hypothalamus
- hypothalamus relays signals to medulla
- vagus nerve fibers from medulla stim enteric nervous system to stomach stim gastric secretion
204
40% of stomach acid secretion occurs in _____ of gastric activity
cephalic phase
205
____ of gastric secretion and ___ of acid secretion occur in the gastric phase of gastric activity
- two thirds
- one third
206
what are the enzymes released during the gastric phase of gastric activity?
- pepsinogen
- intrinsic factor
207
what are the two ways ingested food stims gastric activity?
- by stretching the stomach
- by increasing the pH of the inside of the stomach
208
gastric secretion is stim by three chemicals
- acetylcholine
- histamine
- gastrin
209
acetylcholine is released by what?
secreted by parasym nerve fibers of both reflexes
210
histamine is released by what?
a paracrine secretion from enteroendocrine cells in the gastric glands
211
gastrin is released by what?
a hormone produced by the enteroendocrine G cells in pyloric glands
212
ACh, histamine, and gastrin stim what cells to release what?
- parietal cells
- secrete HCl and intrinsic factor
213
gastrin and ACh stim what cells to release what?
- chiefs cells
- secrete pepsinogen
214
what is the role of the duodenum in the intestinal phase of gastric activity
- duodenum responds to arriving chyme and moderates gastric activity through hormones and nervous reflexes
- initially enhances gastric secretion but soon inhibits it
215
how does the duodenum inhibit gastric secretion? (3)
- stretching of duodenum accentuates vagovagal reflex that stim stomach
- peptides and amino acids in chyme stim G cells of duodenum to secrete intestinal gastrin
- soon acids and fats trigger enterogastric reflex
216
enterogastric reflex
duodenum sends inhibitory signals to stomach by way of enteric nervous system
217
duodenum signals medulla to ___ and stim sympathetic neurons to ____
- inhibit vagal nuclei
- slow stomach activity
218
what happens when duodenum inhibit vagal nuclei
reduces vagal stim of stomach
219
what happens when duodenum stim sympathetic neurons
sends inhibitory signals to stomach
220
chyme also stims duodenal enteroendocrine cells to release the hormones ___ and ____
- secretin
- cholecystokinin
221
what do secretin and cholecystokinin do? (2)
- stim the pancreas to release pancreatic fluid and gallbladder to release bile to suppress gastric secretion
- decreases gastrin secretion and pyloric sphincter contracts tightly to limit chyme entrance to duodenum
222
glucose-dependent insulinotropic peptide (GIP) (3)
- aka gastrin inhibiting peptide
- secreted by enteroendocrine cells
- stimulates insulin secretion in preparation for processing nutrients about to be absorbed by small intestine
223
liver
- reddish-brown gland located immediately inferior to the diaphragm
- largest gland weighing about 3 lbs
224
what is the only function of the liver that contributes to the digestive system?
secretion of bile
225
the gallbladder adhere to a depression on the ____ of the liver
inferior surface
226
hepatocytes
cells in the lobules of the liver
227
what do hepatocytes do after a meal?
absorb glucose, amino acids, iron, vitamin, and other nutrients from blood for metabolism or storage
228
what do hepatocytes do between meals?
break down stored glycogen and release glucose into the blood
229
hepatocytes remove and degrade what four things?
- hormones
- toxins
- drugs
- bile pigments
230
hepatocyte secrete what into the blood? (5)
albumin, lipoproteins, clotting factors, angiotensinogen, and other products
231
the liver receives a mixture of ___ blood and ___ blood
- nutrient-laden venous blood
- freshly oxygenated arterial blood
232
where does nutrient-laden venous blood from for the liver?
the intestines
233
where does freshly oxygenated blood come from for the liver?
celiac trunk
234
after filtering through the liver, blood does what?
leaves the liver through the hepatic veins and drains into inferior vena cava
235
bile canaliculi
narrow channels into which the liver secretes bile which then drains into the right and left hepatic ducts
236
common hepatic duct
formed form convergence of right and left hepatic ducts on inferior side of liver
237
cystic duct
- joins the common hepatic duct
- the cystic duct leads to the gallbladder
238
bile duct
- formed from the union of cystic and common hepatic ducts
- descends toward the duodenum
239
near duodenum the bile duct joins duct of pancreas where it forms the ____ (two words)
hepatopancreatic ampulla
240
hepatopancreatic sphincter
regulates passage of bile and pancreatic juice into duodenum from ampulla
241
between meals what happens to the hepatopancreatic sphincter do?
sphincter closes and prevents the release of bile into the intestines
242
when does the hepatopancreatic sphincter open?
when cholecytokinin (CCK) is released by enteroendocrine cells from the duodenum during a meal
243
gallbladder
pear-shaped sac on underside of liver that stores and concentrates bile by absorbing water and electrolytes
244
bile
fluid secreted by the liver containing minerals, cholesterol, neutral fats, phospholipids, bile pigments, and bile acids
245
pigments and color of bile
- yellow-green color when secreted by liver
- becomes intense green when concentrated in gallbladder
246
bilirubin
primary bile pigments from hemoglobin decomposition
247
bacteria in the intestine metabolize bilirubin into _____
urobilinogen
248
about half of urobilinogen is converted to ____ and the other half is converted to ____
- urobilin (yellow in color)
- stercobilin
249
what converts urobilinogen to urobilin? where does it go after this?
- kidneys
- excreted into urine
250
where does urobilinogen get converted to stercobilin? what is it responsible for?
- intestine
- the brown color in feces
251
bile enters the gallbladder by
filling the bile duct then overflowing into the gallbladder
252
the liver secreted how much bile daily?
500-1000 mL
253
what happens to 80% of bile acids?
reabsorbed in the ileum and retuned to the liver where hepatocytes absorb and resecrete them
254
what happens to 20% of bile acids?
excreted in feces
255
feces is the body's only way for eliminating what?
excess cholesterol
256
the liver synthesizes new bile acids from what?
cholesterol
257
gallstones (3)
- hard messes in either the gallbladder or bile duct
- composed of cholesterol, calcium carbonate, and bilirubin
- usually removed by laparoscopic surgery
258
cholelithiasis
- presence of gallstones
- can occur when cholesterol becomes too concentrated, precipitates as crystals that grow in size
259
cholelithiasis is most common in what people?
obese women over 40
260
a painful obstruction of the bile ducts can result in what?
- jaundice
- poor fat digestion
- impaired absorption of fat-soluble vitamins
261
pancreas
- flattened songy retroperitoneal gland posterior to greater curvature of stomach
- measures 12-15 cm long, 2.5 cm thick
262
the pancreas is both an ___ and ____ gland
endocrine and exocrine
263
endocrine portion of the pancreas
- pancreatic islets that secrete insulin and glucagon
- concentrated in the tail of the gland
264
exocrine portion of the pancreas
99% of pancreas that secretes 1200-1500 mL of pancreatic juice per day
265
what two ducts are apart of the pancreatic duct system
- pancreatic duct
- accessory pancreatic duct
266
pancreatic duct
- runs lengthwise through middle of the gland
- joins bile duct at the hepatopancreatic ampulla
267
hepatopancreatic sphincter controls the release of both ___ into the duodenum
bile and pancreatic juice
268
accessory pancreatic duct
- smaller duct that branches from the main pancreatic duct
- bypasses the sphincter and allows pancreatic juice to be released into duodenum even when bile is not
269
pancreatic juice
alkaline mixture of water, enzymes, zymogens, sodium bicarbonate, and other electrolytes
270
____ secrete the enzymes and zymogens of pancreatic juice
acini
271
___ secrete the sodium bicarbonate of pancreatic juice
ducts
272
what is the purpose of bicarbonate in pancreatic juice?
buffers HCl arriving from the stomach raising the pH to 7
273
what are the pancreatic zymogens
- trypsinogen
- chymotrypsinogen
- procarboxypeptidase
274
trypsinogen
- secreted into intestinal lumen to be converted to trypsin
- autocatalytic
- also converted to chymotrypsin and carboxypeptidase
275
what converts trypsinogen and trypsin?
enteropeptidase
276
enteropeptidase is secreted by
brush border of duodenum
277
what makes trypsin autocatalytic
converts trypsinogen into still more trypsin
278
what are the pancreatic enzymes (not the zymogens) (4)
- pancreatic amylase
- pancreatic lipase
- ribonuclease
- deoxyribonuclease
279
pancreatic amylase
digests starch
280
pancreatic lipase
digests fats
281
ribonuclease and deoxyribonuclease
digests RNA and DNA
282
when do the pancreatic enzymes become fully active
when exposed to bile or ions in intestinal lumen
283
what are the three stimuli that are responsible for the release of pancreatic juice and bile
- ACh (acetylcholine)
- CCK (cholecystokinin)
- secretin
284
acetylcholine as stimuli responsible for the release of pancreatic juice and bile
- stims acini to secrete enzymes during cephalic phase fo gastric control even before food is swallowed
- enzymes remain in acini and ducts until chyme enters the duodenum
285
where does acetylcholine come from to stim release of pancreatic juice and bile?
from the vagus and enteric nerves
286
cholecystokinin as stimuli responsible for the release of pancreatic juice and bile
- stim pancreatic acini to secrete enzymes
- strongly stims gallbladder
- induced contraction of gallbladder and relaxation of hepatopancreatic sphincter to discharge bile and pancreatic juice into duodenum
287
where does cholecystokinin come from to stim release of pancreatic juice and bile?
secreted by mucosa of duodenum in response to arrival of fats in small intestine
288
where does secretin come from to stim release of pancreatic juice and bile?
released from duodenum in response to acidic chyme arriving from the stomach
289
secretin as stimuli responsible for the release of pancreatic juice and bile
- stims ducts of both liver and pancreas to secrete more sodium bicarbonate
- raises pH to the level required for activity of the pancreatic and intestinal digestive enzymes
290
____ is the site of nearly all chemical digestion and nutrient absorption
small intestine
291
what are the dimensions of the small intestine?
5 meters long 2.5 cm wide
292
what is the blood flow out of the small intestine?
- drained by mesenteric veins
- converge to superior mesenteric vein
- joins splenic vein
- flows into hepatic portal system to the liver with its nutrients load
293
what are the three regions of the small intestine
- duodenum
- jejunum
- ileum
294
duodenum of the small intestine (3)
- first 25 cm (10 in)
- begins at pyloric valve
- most is retroperitoneal
295
functions of the duodenum (5)
- receives stomach contents, pancreatic juice, and bile
- neutralizes stomach acid
- emulsifiers fats
- inactivates pepsin
- pancreatic enzymes take over chemical digestion
296
jejunum of the small intestine
- first 40% of small intestine beyond duodenum
- 1-7 meters
- has large, tall, closely spaced circular folds
- wall is relatively thick and muscular
- rich in blood supply so red in color
297
what is the function of the jejunum
- most digestion and nutrient absorption occur here
- final digestion and absorption of carbs, lipids, proteins, and nucleic acids
298
ileum of the small intestine
- forms last 60% of the post duodenal small intestine
- about 1.6-2.7 meters
- thinner, less muscular, less vascular, and paler pink in color than jejunum
299
aggregated lymphoid nodules
- prominent lymphatic nodules in clusters on the side opposite the mesenteric attachment
- visible naked eye
- become larger near large intestine
300
ileocecal junction
- end of the small intestine
- where the ileum joins the cecum of the large intestine
301
the tissues in the small intestine are similar to that of the ___ and ___
esophagus and stomach
302
the lumen of the small intestine is made of what kind of tissue
simple columnar epithelium
303
what are the two layers of the muscularis externa in the small intestine?
- thick inner circular layer
- thin outer longitudinal layer
304
where are the jejunum and the ileum of the small intestine? what does that mean?
- intraperitoneal
- covered with serosa
305
what are the three types of internal folds in the small intestine?
- circular folds
- villi
- microvilli
306
circular folds increase the surface area in the small intestine by a factor of
2-3
307
villi increase the surface area of the small intestine by a factor of
10
308
microvilli increase the surface area of the small intestine by a factor of
20
309
circular folds of the small intestine
- transverse to spiral ridges up to 1 cm high
- largest folds of the intestinal wall
310
the circular folds of the small intestine involve only the ____ and ____
mucosa and submucosa
311
where can you find circular folds of the small intestine?
duodenum to middle of ileum
312
why are there no circular folds in the distal portion of the ileum in the small intestine
because most nutrient reabsorption is complete by this point
313
what is the function of the circular folds of the small intestine
- cause chyme to flow in a spiral path causing contact with mucosa
- promote more thorough mixing and nutrient absorption
314
villi of the small intestine
- projections 0.5-1 mm high with tongue-to-fingerlike shapes
- make mucosa look fuzzy
- covered with two types of epithelial cells
315
what are the two types of epithelial cells that cover the villi small intestine?
- absorptive cells (enterocytes)
- goblet cells
316
what is the purpose of the two types of epithelial cells that cover the villi of the small intestine
secrete mucus
317
the epithelia of villi are joined by tight junctions to do what?
prevent digestive enzymes from seeping between them
318
the core of the villus in the small intestine is filled with what?
areolar tissue of lamina propria
319
what can be found in the areolar tissue of the lamina propria inside the villus of the small intestine?
- arteriole
- bloo capillaries
- venule
- lacteal
320
lacteal of small intestine
lymphatic capillaries in the small intestine villi that absorb most lipids and fats
321
____ absorbs most nutrients in the small intestine
blood capillaries in the villi
322
microvilli of the small intestine
- small plasma membrane extensions that form a fuzzy brush border on apical surface of each enterocyte
- about 1 um high
323
what is the function of microvilli in the small intestine
increase absorptive surface area and contain brush border enzymes
324
brush border enzymes
- contained in plasma membrane of microvilli
- carry out some of the final stages of enzymatic digestion
- not released into the lumen
325
contact digestion
chyme must contact the brush border for digestion to occur
326
____ ensures contact with the mucosa of the small intestine
intestinal churning of chyme
327
duodenal glands
- in submucosa of duodenum
- secrete an abundance of bicarbonate rich mucus
328
what is the function of the bicarbonate released by duodenal glands
- neutralize stomach acid and shield the mucosa from its erosive effects
- mucus contains signaling molecules that influence immune cells to tolerate food antigens and beneficial bacteria
329
what is the function of the lymphocytes found throughout the lamina propria and submucosa of the small intestine?
intercept pathogens before they can invade bloodstream
330
intestinal crypts
- between bases of the villi
- pores that open into tubular glands on the floor of the small intestine
- can extend as far as the muscularis mucosae
331
how much intestinal juice do intestinal crypts secrete per day?
1-2 liters
332
what triggers intestinal crypts to release intestinal juice?
- acid
- hypertonic chyme
- digestion of intestine
333
what is the pH of intestinal juice secreted by intestinal crypts? what is in it?
- 7.4-7.8
- water, mucus, little enzymes
334
most enzymes found in the small intestine are found where?
the brush border and pancreatic juice
335
what are the three functions of the contractions of the small intestine?
- mix chyme with intestinal juice, bile, and pancreatic juice
- churn chyme and bring it in contact with the mucosa for contact digestion and nutrient absorption
- to mose residue towards large intestine
336
what is the function of mixing chyme with intestinal juices, bile, and pancreatic juice?
- to neutralize acid
- digest nutrients more effectively
337
segmentation
- movement in which stationary ring-like constrictions appear in several places along the intestine
- most common intestinal contraction
- kneads and churns the intestinal contents
338
when do segmentation rings releax?
as new constrictions form elsewhere
339
what controls the rhytm of segmentation in the small intestine?
enteric pacemaker cells in the muscularis externa
340
describe the segmentation contractions in the duodenum and ileum
- contracts about 12x per minute in the duodenum
- 8-9x per min in the ileum
341
what happens to the small intestine contractions when nutrients have been absorbed?
segmentation declines and peristalsis begins
342
peristalsis
- rhythmic contractions that moves remaining contents of small intestine toward colon
- wave travels 10-70cm and dies out followed by another wave starting a little further down the tract
343
migrating motor complex
- successive overlapping waves of contraction
- milk chyme towards colon over a period of 2 hours
344
food in the stomach triggers ___ that enhances segmentation in the ileum and relaxes the ileal papilla
gastroileal reflex
345
what happens to the ileal papilla when there is food in the stomach?
releases material from small intestine to large intestine
346
what vitamins are fat soluble?
- A
- D
- E
- K
347
if fat-soluble vitamins are ingested with fat-containing food what happens?
they are not absorbed at all and passed in the feces and wasted
348
what are the water-soluble vitamins?
- B complex
- C
349
how is vitamin C absorbed in the body
simple diffusion in the stomach
350
how is B12 absorbed in the body?
intrinsic factor in the stomach
351
where does mineral absorption occur?
all along the small intestine
352
describe iron and calcium absorption in the small intestine.
- absorbed as needed
- most absorbed calcium is from meat and diary
- dietary fat slows calcium absorption
353
parathyroid hormone
- secreted in response to a drop in blood calcium levels to increase calcium absorption in duodenum
- stims kidney to synthesize vitamin D from precursors made by epidermis and liver
354
the digestive tract receives about ____ water a day
nine liters
355
water is absorbed by ___
osmosis
356
osmosis in the body
water follows the absorption of salts and organic nutrients
357
diarrhea
- occurs when large intestine absorbs too little water
- feces passes through too quickly if intestine is irritated
- contains high concentration of solute
358
lactose intolerance
- small intestine lack lactose to break down lactose
- excess lactose in the feces with diarrhea
359
describe the dimensions of the large intestines
1.5 meters long and 6.5 cm diameter
360
appendix
- attached to lower end of cecum in large intestine
- densely populated with lymphocytes and is significant source of immune cells
361
colon
portion of large intestine between ileocecal junction and rectum
362
what are the four portions of the colon
- ascending
- descending
- transverse
- sigmoid
363
what three portions of the colon frame the small intestine
- ascending
- desceinding
- transverse
364
sigmoid colon
S shaped portion leading down into pelvic cavity
365
rectum
- portion ending at anal canal
- has three curves and three infoldings
366
anal canal
- final 3 cm of the large intestine
- large hemorrhoidal veins
367
hemorrhoidal veins
- form superficial plexus in anal columns and around orifice
- lack valves and are subject to distension
368
hemorrhoids
permanently distended veins that protrude into anal canal or bulge outside the anus
369
what differentiates the muscularis externa of the colon from other organs with the same layer of muscle?
- taenia coli
- haustra
- in rectum and anal canal longitudinal muscle is continuous sheet with no haustra
370
taenia coli
longitudinal fibers concentrated in three thickened ribbon like strips
371
haustra
pouches in the colon caused by the muscle tone of the taenia coli
372
what two sphincters regulate the anus
- internal anal sphincter
- external anal sphincter
373
internal anal sphincter
smooth muscle of muscularis externa
374
external anal sphincter
skeletal muscle of pelvic diaphragm
375
large intestine mucosa (5)
- simple columnar epithelium in all regions except lower half of anal canal
- no circular folds or villi
- intestinal crypts are deeper than in small intestine
- greater amount of goblet cells
- lots of lymphoid tissue in lamina propria and submucosa
376
what is the purpose of there being an abundance of lymphoid tissue in the large intestine
provides protection from large population of bacteria in large intestine
377
gut microbiome
- microbiota
- more than 1000 species of bacteria, yeasts, viruses and other microbes that populate the large intestine
378
what do bacteria in the gut microbiome do?
- digests cellulose, pectin, and other carbohydrates for which our cells lack enzymes
- help in the synthesis of vitamins K and B
379
flatus
intestinal gas that is expelled
380
an average person produces ____ per day
500 mL
381
what is in flatus
- hydrogen sulfide
- indole
- skatol
382
____ produces odor in flatus
skatol
383
the large intestine takes how many hours to reduce food residue to feces
36-48 hours
384
how does the large intestine change food residue to feces
does not chemically change the residue but reabsorbs water and electrolytes
385
food residue spends the most amount of time in which part of the colon?
transverse colon
386
feces is how much water and how much solid?
75% water and 25% solid
387
what is in the solids of feces? (percentages too) (4)
- 30% bacteria
- 30% undigested fiber
- 10-12% fat
- small amounts of mucus, proteins, salts, digestive secretions, and sloughed epithelial cells
388
colonic motility includes what two things?
- haustral contractions
- mass movements
389
haustral contractions of colonic movement
- occur every 30 min
- distension of a haustrum stims it to contract
390
what is the purpose of haustral contractions of colonic motility
churns and mixes residue promoting water and salt absorption
391
mass movement of colonic movement
- stronger contractions that occur one to three times a day
- triggered by gastrocolic and duodenal reflexes
- filling of the stomach and duodenum stims motility of the colon
392
what is the purpose of mass movement of colonic motility
move residue several cm
393
the stretching of the rectum stims what two defecation reflexes?
- intrinsic defecation reflex
- parasympathetic defecation reflex
394
how does the intrinsic defecation reflex work
stretching signals travel through plexus to the muscularis causing it to contract and the internal sphincter to relax
395
parasympathetic defecation reflex involves the
the spinal cord
396
the intrinsic defecation reflex works with what to produce its response?
works entirely within myenteric plexus to produce relatively weak response
397
how does the parasympathetic reflex work?
- stretching of rectum sends sensory signals to spinal cord
- pelvic nerves return signals intensifying peristalsis and relaxing the internal anal sphincter
398
defecation occurs only if ___ and ___ are voluntarily relaxed
- external anal sphincter
- puborectalis muscles
399
Valsalva maneuver
abdominal contractions increase abdominal pressure and compress rectum to assist in defecation
