digestion I Flashcards
(263 cards)
1
Q
2 general functions of the digestive system:
A
1) get in INTO the body
2) break it down
2
Q
nutrients are absorbed (macros, vitamins, minerals) into the body into ________
A
circulation
3
Q
mouth and anus are at the distal ends of the continuous tube; anything in the tube is considered ______ of the body
A
outside
4
Q
continuous muscular tube
A
alimentary canal
5
Q
ALONG alimentary canal; assist in digestion (ex: teeth, tongue, salivary glands, liver, pancreas)
A
accessory organs
6
Q
organs includes in the alimentary canal (7):
A
- mouth
- pharynx
- esophagus
- stomach
- small intestine
- large intestine
- anus
7
Q
accessory organs (5):
A
- teeth
- tongue
- salivary glands
- liver
- pancreas
8
Q
Functions/actions of the Digestive System (6):
A
- ingestion
- propulsion (deglutition and peristalsis)
- mechanical digestion (mastication, mixing, segmentation)
- chemical digestion
- absorption
- defecation
9
Q
function of the digestive system: bring food INTO the system
A
ingestion
10
Q
function of the digestive system: MOVE food through the system
A
propulsion
11
Q
types of propulsion (2):
A
- deglutition
- peristalsis
12
Q
type of propulsion: swallowing; voluntary; conscious control
A
deglutition
13
Q
types of propulsion: smooth muscle contractions; involuntary; subconscious, wave-like
A
peristalsis
14
Q
function of digestive system: physical breakdown of food; big pieces into small pieces; reduction of size of food but increase in SA of food so we can act on it more efficiently
A
mechanical digestion
15
Q
types of mechanical digestion (3):
A
- mastication
- mixing
- segmentation
16
Q
type of mechanical digestion: chewing
A
mastication
17
Q
type of mechanical digestion: the stirring of saliva, gastric juice, and other foods
A
mixing
18
Q
type of mechanical digestion: contraction and relaxation of of parts of tube; moves things through; mixing and propulsion occur
A
segmentation
19
Q
function of digestive system: enzymatic breakdown of food ingested INTO building blocks (ex: carb –> glucose, lipids –> fatty acids)
A
chemical digestion
20
Q
where does chemical digestion first start?
A
mouth (digesting STARCH)
21
Q
what is the first thing we digest?
A
starch
22
Q
function of the digestive system: mostly done by the large (and small) intestine
A
absorption
23
Q
function of the digestive system: elimination of wastes (“feces”)
A
defecation
24
Q
CONTROL components of the digestive system (3):
A
- sensors
- nerve plexuses
- hormones
25
stimuli that can activate Control components of digestive system (5):
- stretch (ex: walls of stomach causes release of dig. enzymes)
- osmolarity
- concentration gradients
- pH changes
- specific nutrients (ex: proteins, lipids)
26
type of control component of dig. system: detect certain stimuli; send nervous signals to nerve plexuses
sensors
27
type of control component of dig. system: branching network of nerves; composed of afferent and efferent fibers
nerve plexus
28
types of nerve plexuses (2):
intrinsic and extrinsic
29
type of nerve plexus: entirely WITHIN the gastrointestinal tract
intrinsic
30
type of nerve plexus: invovles things other than the digestive tract
extrinsic
31
type of control component of dig. system: chemical messengers; released or inhibited
hormones
32
two layered serous membrane that attaches to backwall to anchor organs; specific TYPE of peritoneum
mesentary
33
the serous membrane forming the lining of the abdominal cavity
peritoneum
34
2 layers of peritoneum:
- viceral
| - parietal
35
type of peritoneum: "belongs to the organ"
visceral peritoneum
36
type of peritoneum: "belongs to the cavity"
parietal peritoneum
37
organs behind the abdominal cavity
retroperitoneum organs
38
tunics of the peritoneum (4):
- mucosa
- submucosa
- muscularis externa
- serosa
39
tunic of peritoneum: most superifical; epithelial tissue; mucus membrane that keeps things MOIST
mucosa
40
tunic of peritoneum: composed of a top and bottom layer; top is made of epithelital tissue with NO blood vessels; bottom is made of dense irregular CT that goes to blood vessels
submucosa
41
tunic of peritoneum: smooth muscle; 2 layers that are INVOLUNTARY
muscularis externa
42
layer of muscularis externa: circular layer of muscle; changes diamter of lumen/tube when it contracts
top layer of muscularis externa
43
layer of muscularis externa: longitudinal layer; SHORTENS tube when it contracts
bottom layer of muscularis externa
44
tunic of peritoneum: deepest layer; "visceral peritoneum;" hormones; protective
serosa
45
in which tunic (and layer) of the peritoenum do blood vessels start to run through?
bottom layer of SUBMUCOSA
46
intrinsic nerve system =
enteric nervous system / "neurons"
47
types of enteric nerves (2):
- submucosal nerve plexus
| - myenteric nerve plexus
48
type of enteric nerve: detects stretch and pH; causes glandular action = SECRETION
submucosal nerve plexus
49
type of enteric nerve: between two layers of muscle in muscularis externa; caues muscular action = MOTILITY
myenteric nerve plexus
50
oral cavity =
buccal cavity
51
buccal (oral) cavity components (4):
- palate
- tongue (includes papillae)
- salivary glands
- teeth
52
buccal cavity component: only part of digestive system involved with INGESTION; also involved in propulsion; cheeks and lips cut off cavity; includes the roof and floor of mouth
palate
53
entry pathway of digestive system
buccal cavity
54
buccal cavity component: helps the palate; moves food around in oral cavity, mixing it; functions in swallowing
tongue
55
ball of food that moves through swallowing
bolus
56
small bumps located on the top and sides of your tongue
papillae
57
2 types of papillae:
- fungiform
| - filiform
58
type of papilae: has TASTE BUDS
fungiform papillae
59
type of papillae: gives mouth GRIP
filiform papillae
60
buccal cavity component: glands that make saliva
salivary glands
61
types of salivary glands (3):
- parotid gland
- sublingual gland
- submandular gland
62
type of salivary gland: sits under the ear; composed of "serous cells" that produce enzymes
parotid gland
63
type of salivary gland: made up of mucus cells
sublingual gland
64
type of salivary gland: made of mucus + enzyme cells
submandular gland
65
cleanses mouth; enzymes specific for starch; makes things BIOLOGICALLY ACTIVE
saliva
66
nothing is biologically active until it is in _______
solution
67
_________ nervous stimulation stimulates production of SALIVA and is brought to the brain by __________-
PARASYMPATHETIC
| chemoreceptors
68
components of saliva (6):
- water
- electrolytes
- amylase
- lysosomes
- IgA
- metabolic wastes
69
componet of saliva: 97-99% of saliva; MAJORITY of saliva
water
70
componet of saliva: ions
electrolytes
71
component of saliva: enzyme that breaks down starch (occurs in 2 places)
amylase
72
componet of saliva: includes urea and uric acid
metabolic wastes
73
pH range of saliva
6.5 -- 6.7
74
how many sets of teeth do we have over our lifetime?
2
75
type of set of teeth: 20; appear in segments; lose them as we age
primary (deduces, milk, baby) teeth
76
how many primary teeth do we have?
20
77
how many permanent teeth do we have?
32
78
type of set of teeth: not replaced; 32
permanent teeth
79
four TYPES of teeth:
- ensizers
- cuspid
- bicuspids
- molars
80
type of tooth: front 4; pull/cut food
ensizers
81
type of tooth: canine/fang; pierce food; 2
cuspid
82
type of tooth: 4 total; sheering/cutting
bicuspids
83
type of tooth: flat, grinding (used for plants originally); 6 total
molars
84
last tooth to come in
3rd molar (wisdom tooth/18 year molar)
85
overtime, the human jaw has become ______
smaller
86
region of tooth: above gum; covered by enamel
crown
87
region of tooth: transition part
neck
88
region of tooth: embedded in bone, into the jaw
root
89
part of tooth structure: only in the crown; protects teeth
enamel
90
part of tooth structure: deeper too enamel; in root + crown
dentine
91
part of tooth structure: soft tissue; extends to root canal; contains blood vessels and nerves
pulp
92
another name for your "gums"
gingiva
93
part of tooth structure: made of CT; "glues" tooth to socket
cementum
94
region of propulsion (its ONLY FUNCTION); has 3 portions
pharynx
95
which portion of the pharynx does food not pass?
nasopharynx
96
propels food through; tube extends into trachea when bolus passes through
esophagus
97
2 sphincters of the esophagus:
- upper esophageal sphincter
| - gastroesophageal sphincter
98
constrictions in the esophagus that prevent food from going the wrong direction
esophageal sphincters (upper esophageal sphincter + gastroesophageal sphincter)
99
deglutition process (3):
1) food compacted into bolus
2) buccal phase (voluntary component)
3) pharyngeal-esophagus phase (involuntary component)
100
buccal phase (VOLUNTARY - 3):
1) tip of tongue is placed against hard palate
2) tongue contracts to force bolus into orophayrnx
3) bolus stimulates tactile (tought) receptors; sends signals to brain --> parasympathetic, autonmic signals
101
pharyngeal-esophageal phase (INVOLUNTARY - 3):
1) tactile (touch) receptors stimulate medulla and pons
2) motor impulses sent to muscles
3) peristalsis moves bolus toward stomach
102
hollow tube with a swelling; muscular storage; can contract in ALL directions; cardiac sphincter prevents back flow of food; pyloric sphincter controls release into small intestine
stomach
103
3 functions of the stomach:
- propulsion
- mechanical digestion
- chemical digestion
104
_____ digestion begins in the stomach
protein
105
what does the cardiac sphincter of the stomach do?
prevents backflow of food (back into the esophagus)
106
what does the pyloric sphincter of the stomach do?
contorls release of food into the small intestine
107
folds in the stomach; increase surface area; can flatten before ingestion of food
rugae
108
volume of stomach when you're NOT eating
50 mL
109
volume of stomach when you're eating:
400 mL or 4 L
110
types of stomach cells (5):
- goblet cells
- mucous neck cells
- parietal cells
- chief cells
- enteroendocrine cells
111
type of stomach cell: includes gastric pits and gastric glands (in base); secrete mucus in stomach
goblet cells
112
type of stomach cell: first cells; produce slightly acidic mucus
mucous neck cells
113
type of stomach cell: second cells (deeper); produce hydrochloric acid + intrinsic factor
parietal cells
114
acidic digestion component
hydrochloric acid
115
glycoprotein required by the small intestine to absorb B12 (which is required for RBC synthesis)
intrinsic factor
116
vitamin needed for erythropoeisis (RBC prod.) -- required for life
B12
117
type of stomach cell: produces pepsinogen
chief cells
118
INACTIVE form of enzyme that breaks down protein
pepsinogen
119
active form of pepsinogen
pepsin
120
what activate pepsinogen into pepsin?
hydrochloric acid
121
why is pepsinogen inactive?
so it doesnt digest the wall of the stomach
122
type of stomach cell: hormone-producing cells; produce GASTRIN
enteroendocrine cells
123
another name for enteroendocrine cells
G-cells (ones that produce gastrin)
124
hormone that regulates activity of other parts of the digestive tract other than the stomach (where it is produced)
`gastrin
125
in the stomach, the bolus is liquified and turned into _______
chyme
126
how does the stomach liquify the bolus into chyme?
through the secretion of gastric juice
127
types of stomach action (2):
1) secretes gastric juice
| 2) muscular contractions
128
phases of Gastric Secretion (3):
- cephaic (relex) phase
- gastric phase
- inestinal phase
129
gastric secretion phase: conditioned/acquired reflex (learned); when you think about foods you like (or begin eating them), our stomach becomes active BEFORE FOOD ARRIVES; long reflex -- involves brain
cephalic (reflex) phase
130
gastric secretion phase: food arrives in stomach; could be both stimuli (synergenic effect) or one (either by stretch or by pH)
gastric phase
131
grastric phase STRETCH stimuli pathway (4):
1) stretch (in wall)
2) autonomic signal, parasympathetic signal to brain
3) release of acetylcholine
4) gastric glands start to secrete
132
gastric phase pH stimuli pathway (3):
- increase of pH through the arrival of saliva (above 2) OR presence of protein
- G cells are stimulated to produce gastrin
- glands secrete
133
the gastric phase has a _____ _____ _____
negative feedback loop
134
gastric secretion phase: food enter small intestine; 2 parts; chyme trickles out very slowly (3mL @ a time)
intestinal phase
135
2 parts of the intesteinal phase:
- excitatory
| - inhibitory
136
part of intestinal phase: stimulates stomach to INCERASE activity
excitatory
137
part of intestinal phase: slows down digestion of contents so you don't digest your stomach
inhibitory
138
"Interograstric Reflex" pathway of the intestinal phase (4):
- stretch of intestine
- decrease in stomach activity
- sympathetic activity
- pyoric sphincter SHUTS
139
barrier that prvents us from digesting our own stomach
mucosal barrier
140
components of mucosal barrier (4):
- bicarbonate rich mucus
- tight junctions in mucosal epithelium
- HCl-impermable plasma membranes in gastric gland cells
- undifferentitated stem cells at junction of gastric pits and gastric galnds
141
component of mucosal barrier: buffers pH @ lining of wall
bicarbonate-rich mucus
142
component of mucosal barrier: doesnt allow acid to get through; impermeable
tight junctions in mucosal epithelium
143
component of mucosal barrier: allows enzymes to go to gastric pits, but not the other way around
HCl-impermeable plasma membranes in gastric gland cells
144
component of mucosal barrier: constantly replaces cells (any type)
undifferentiated stem cells at junction of gastric pits and gastric glands
145
entire lining of stomach is repelaced every ___-____ days
3-6 days
146
what can occur if the stomach lining is not replaced every 3-6 days?
ulcers and bleeding
147
components of gastric FILLING (2):
- receptive relaxation
| - adaptive relaxation
148
component of gastric filling: stomach enlarges BEFORE food arrives bc it knows its coming
receptive relaxation
149
component of gastric filling: rugae start to flatten (greater stomach volume); NO stretch occurs; no stretch occurs until 1L of food is in stomach
adaptive relaxation
150
NO stretch occurs in the stomach until ____ of food arrives in the stomach
1 L
151
gastric contraction involves a ______ ______ ______
basic electrical rhythm
152
basic electrical rhythm of the stomach =
3 pulses / min
153
"pace-maker cells" of the stomach; involved in the basic electrical rhythm/contractions;
interstitial cells of Cajal
154
perform propusal movements and the MAJORITY of stomach contraction; have autorhythmic cells that depolarize
longitudinal muscles
155
interstitial cells of Cajal are located in the _________ layer of the stomach
longitudinal (muscular layer)
156
for every stomach contraction, there is an increase in _______
pressure
157
gastric contraction: ____ mL of chyme is pushed into the duodenum, then ____ mL goes back into the stomach when it is relaxed
30 mL
| 27 mL
158
why does gastric contraction only push 3 mL of chyme per minute into the small intestine (2)?
- slow process increases efficiency of digestion -- more absorption
- prevents a big wave of pH change from entering small intestine
159
gastric contraction: anything that involves ______ ______ increase the # of contractions/RATE
hydrochloric acid
160
gastric emptying process (6):
1) chyme enters duodenum
2) stretch and chemoreceptors are activated in small intestine
3) enterogastric or enterogastrone (hormone in small intestine) reflexes initiated (inhibits gastric secretion)
4) gastric activity reduced
5) pyloric contractions reduced
6) duodenal filling stopped
161
gastric emptying is completed ____ hours after your meal
4 hours
162
when something in your stomach causes excessive stretch or irritation; stimulates diaphragm and abdominal muscles to contract
emisis/vomiting/regurgitation/"reverse peristalsis"
163
other names for vomiting:
- emisis
- regurgitation
- "reverse peristalsis" (but not)
164
major digestive organ; digests EVERY macromolecule and finishes it here; organ of absorption, chemical digestion, and propulsion
small intestine
165
functions of small intestine (3):
- absorption
- chemical digestion
- propulsion
166
how long is the small intestine when were alive? and dead?
alive: 8-13 ft
dead: 20 ft
167
the small intestine runs from the _____ _____ to the beginning of the large intestine which is known as the ______ _______
pyloric sphincter
| ilocecal valve
168
subdivision/segments of the small intestine (in order - 3):
- duodenum
- jejunum
- ileum
169
subdivision of the small intestine: first 10 inches
duodenum
170
located in the duodenum; way for secretions from the liver and pancreas to be inserted into the small intestine
hepatopancreatic ampulla
171
subdivision of the small intestine: middle 8 feet
jejunum
172
subdivision of the small intestine: rremaining segment; has "ileocecal valve" (regulates empying of small intestine)
ilieum
173
located in the ileum; regulates empying of small intestine
iliocecal valve
174
structural modifications of the small intestine (4):
- length
- plicae circulares
- villi
- microvilli
175
structural modification of the small intestine: gives it high SA = 206m; medication is bigger than the large intestine
length
176
length of small intestine
206 m
177
structural modification of the small intestine: folds in small intestine that increase SA; part of mucosa + submucosa lining; makes fluid SPIRAL down (slows it down and increases contraction of wall); spiral
plicae circulares
178
structural modification of the small intestine: within mucosa; finger-like projections; increase SA (and increase contraction of chyme)
villi
179
structural modification of the small intestine: modified plasma membrane of villi; increase SA
microvilli
180
lining of small intestine = "_____ _____"
brush board
181
acidic liquid produced by the small intestine; stimulated by the arrival of acidic gastric juice; shuts off pepsin
intestinal juice
182
intestinal juice shuts off _____
pepsin
183
digestive organ that processes blood; breaks down hemoglobin with bile as a by product
liver
184
NOT any enzyme (not catabolic); causes digestion of FAT; an emulsifier; increases SA of fat
bile
185
bile components (7):
- water
- bile salts
- bile pigments (bilirubin --> urobilinogen)
- cholesterol
- neutral fats
- phospholipids
- electrolytes
186
bile component: MAJORITY of bile
water
187
bile component: perfrom emulsification
bile salts *
188
bile component: green; is broken down into different ones
bile pigments
189
bile pigments: HEMOGLOBIN is broken down into ________, which is then converted to ________
bilirubin ---> urobilinogen
190
bile pigment that is brown -- aka way poop is brown
urobilinogen
191
FOUR lobes of the liver:
- right
- left
- caudate
- quadrate
192
separates left and right lobes of the liver
falsiform ligament
193
ducts of the liver (2):
- common hepatic duct
| - bile duct
194
liver duct: connects to hepatopancreatic ampulla (usually closed)
cmmon hepatic duct
195
bile goes into the gallbladder through the _____ duct
cystic duct
196
order of ducts in which bile travels to get to the duodenum (5):
- common hepatic duct
---- cystic duct
common bile duct
---- pancreatic duct
hepatopancreatic duct
* --- means it joins it
197
function is to STORE and CONCENTRATE bile; acclaims/absorbs water to concentrate bile
gallladder
198
if the gallbladder concentrates bile too much, it can lead to ______
gallstones
199
bile storage process (3):
1) the heptopancreatic sphincter is CLOSED when not digesting (most of the time)
2) liver continually produces bile
3) bile backs up cystic duct
200
bile release process (3):
1) fatty chyme entering duodenum stimulates production of cholecystokinin (CCK) by intestine (allows release of bile)
2) CKK causes PARAsympathetic impulses to promote gallbladder contraction
3) CCK also relaxes hepatopancreatic sphincter -- opens it
201
CCK =
cholecystokinin
202
produces pancreatic juice
pancreas
203
pathway of pancreatic juice (3):
- main pancreatic duct
- bile duct
- hepatopancreatic ampulla
204
components of pancreatic juice (3):
- water
- enzymes
- bicarbonate
205
comment of pancreatic juice: majority of juice
water
206
comment of pancreatic juice: used for every macromolecule; produced by EXOCRINE cells in pancreas
enzymes
207
_______ cells in pancreas produce enzymes in pancreatic juice
exocrine
208
component of pancreatic juice: secreated by cells that makeup pancreatic duct; pH is above 8 so it neutralizes chyme so enzymes do not get denatured
bicarbonate
209
enzymes that break down proteins (issue); activated in the DUODENUM
protease enzymes
210
protease enzymes (active forms):
- trypsin
- carboxypeptidase
- chymotrypsin
211
activates trypsinogen to its active form -- trypsin; producated by brush-boarder of small intestine
enterokinase
212
activatation pathway of trypsin =
enterokinase activates trypsinogen (inactive) to TRANSFORM into trypsin
213
inactive form of trypsin
trypsinogen
214
activatation pathway of carboxypeptidase =
trypsin activates Preocarboxypeptidase (sec. by pancrease) into its active form -- carboxypeptidase
215
inactive form of carboxypeptidase; secreted by the pancrease
procarboxypeptidase
216
activatation pathway of chymotrypsin =
trypsin actives chymotrypsinogen which becomes chymotrypsin
217
inactive form of chymotrypsin
chymotrypinsogen
218
enzyme that breaks down starch
amylase
219
enzyme that breaks down fat
lipase
220
enzyme that breaks down nucleic acids
nucleases
221
CONTROLS of pancreatic secretion:
- secretin
- CCK
- paraympathetic impulses
222
pancreatic secretion is controlled by both ______ and ______
hormones and nerves
223
control of pancreatic secretion: stimulate pancreatic duct cells to produce bicarbonate; decreases acidicty of chyme
secretin
224
control of pancreatic secretion: homone; stimulates production of enzymes by exocrine cells
CCK
225
control of pancreatic secretion: stimulates exocine OR duct cells to start producing and secreting
parasympathetic impulses
226
components involved in the EMPYTING of the small intestine (3):
- gastroileal reflex
- gastrin
- pressure
227
linkage between activity of stomach and ileocecal valve; causes segmentation contractions in small intestine for EMPYTING (mixing and propels food forward slowly)
gastroileal reflex
228
activate stomach + small intestine to EMPTY; released by endocrine cells; relaxes ilioccal valve -- open now
gastrin
229
empyting of small intestine component; chyme stretches and caues this which causes iliocecal valve to CLOSE
pressure
230
chyme going through the small intestine is _____
hyptotonic (lower osmotic pressure)
231
length of large intestine =
9 ft (shorter than small intestine)
232
functions of large intestine (3):
- absorption (mostly water)
- propulsion
- elimination
233
where does digestion primarily occur?
duodenum of small intestine
234
the jejunum is healvily involved with _______
enzymes
235
what does the ileum of the small intestine do?
just absorbs bile salts
236
bends in large intestine; allows gases to pass faster than solids
rectal valves
237
subdivision/segments of the LARGE intestine (in order - 5):
- cecum
- ascending colon
- transverse colon
- descending colon
- sigmoid colon
238
segment of large intestine: has an evolutionaly relic known as the abbermifa appendice (aka appendix); serves as a hideout for microbiome/bacteria; TRACT
cecum
239
the appendice probably once used to digest ______
cellulose
240
segment of the large intestine: goes into the rectal canal + anus
sigmoid colon
241
anus has _____ sphincters
2 (internal and exertnal)
242
anus sphincter: smooth muscle; involuntary
internal anal sphincter
243
anus sphincter: skeletal muscle; voluntary (for about 70 years...)
external anal sphincter
244
most common blockage of the appendix
seeds + gum*
245
2nd most common blockage of the appendix
opiates
246
sac-like puckerings of the large intestine
haustra
247
bands of smooth muscle from musculera that wraps around large intestine that form puckerings
taenia coli
248
what are feces made of (4)?
- undigested food residue (ex: cellulose)
- sloughed off epithelial cells (from mucosal layer of ileum + large intestine)
- bacteria (from microbiota)
- little bit of water
249
if too much or too little water is in feces, what happens?
either diarhhea or constipation
250
fat that accumulates on large instestine; doesnt appear to have a function
epiploic appendages
251
not here for us; warm, moist, dark environments and food allow them to thrive; do not benefit us dietarily -- but do benefit us in other ways
intestinal bacteria
252
functions of intetinal bacteria (3):
- ferment indigestible carbohydrates
- synthesize B vitamins
- synthesize vitamin K
253
when intestinal bacteria ferment indigestible carbohydrates, it produces a gas. when mixed with ______ _____, it is a very smelly fat.
dimethyl sulfide
254
some of the B vitamins produced by intetinal bacteria are absorbed by the ____ _____
large intestine
255
what vitamin is required to make RBCs?
B12
256
vitmamin used by the liver to make clotting proteins; synthesized by intestinal bacteria
vitamin K
257
we usually do not get enough of vitamin ____ or ____ from our diet so intestinal bacteria help us out with that by synthesizing them
B or K
258
motility components of large intestine:
- haustral contractions
| - mass movements
259
motility component of large intestine: moves feces along SLOWLY; occur every 30 minutes; form of segmentation
haustral contractions
260
motility component of large intestine: occur 3-4 times a day; typically triggered after a meal
mass movements
261
haustral contractions occur every _____ ____
30 min.
262
mass movments usually occur ___-___ a day
3-4 (apparently)
263
defecation reflex (4):
1) mass movements cause stretch on wall of large intestine
2) stretch triggers parasympathetic stimulation of sigmoid colon and rectum, and inhibits anal sphincters (both sets are relaxed and open during defecation -- except external may be constricted and closed for a short per. of time)
3) external anal sphincter under voluntary control
4) Valsalva's manueuver assists emptying (aka you pushing)
