Chapter 6 Flashcards
(112 cards)
1
Q
5 major organs involved with digestion
A
the liver, gallbladder, pancreas, spleen, and stomach
2
Q
Gastrointestinal Tract (GIT), other names:
A
alimentary tract or gut
3
Q
continuous muscular tube that winds through the body from the mouth to the anus
A
GIT
4
Q
Organs of the GIT
A
mouth, pharynx, esophagus, stomach, small intestines, large intestines, and anus
5
Q
Accessory organs of GIT
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teeth, tongue, gallbladder, salivary glands, liver, and pancreas
6
Q
Food becomes less complex as it
A
goes through the GIT
7
Q
activity of the GIT is controlled by
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chemical and mechanical stimuli
8
Q
chemical stimuli
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pH levels or presence of certain substrates
9
Q
mechanical stimuli
A
stretching of organs as digesta passes through
10
Q
different mechano- and chemoreceptors are activated, glands within the GIT are either inhibited or activated resulting
A
in increase of digestive juices into the lumen or hormones into the blood
11
Q
Smooth muscles are stimulated to
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contract, thus mixing luminal contents (digesta and juices) and moving them through the GIT
12
Q
gut’s brain
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GIT’s nerve plexus, called enteric nervous system located in the walls of the GIT
13
Q
Intrinsic nerve plexus
A
enteric nervous system
14
Q
the intrinsic nerve plexus communicates with
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the extrinsic nerve plexus, which is outside of the GIT and relays those signals to the central nervous system
15
Q
Vagus nerve, pelvic nerves and sympathetic pathways
A
provide connections between the two plexus (intrinsic and extrinsic nerve plexus)
16
Q
2 common NT that help facilitate signals during different types of autonomic responses
A
Acetylcholine relays parasympathetic signals, while epinephrine relays sympathetic signals
17
Q
if the vagus nerve or sympathetic signals were severed, could the GIT function?
A
Yes because of “gut’s brain”
18
Q
if the enteric nervous system were severed, would the GIT function?
A
the GIT would be in a lot of trouble
19
Q
Gastric secretion, 3 phases:
A
phase 1: cephalic
phase 2: gastric
phase 3: intestinal
20
Q
Cephalic phase
A
condition response, which means that it is an automatic response to certain triggers
21
Q
examples of the cephalic phase
A
aroma, taste, sight, and even thoughts revolving food could, begins before food is ingested
22
Q
primer stage that prepares stomach for the incoming digesta
A
cephalic phase
23
Q
What is going on during the cephalic phase?
A
olfactory receptors and taste buds send sensory input to the hypothalamus, which then stimulates vagal nuclei of the medulla oblongata within the brain, less than 50% of the total response of gastric secretion
24
Q
during depression
A
patients are not hungry and have a suppressed appetite, which inhibits cerebral cortex function related to stimulating the parasympathetic centers
25
Gastric phase
at least 50% of the total response, it can last from 3-4 hours
26
Gastric phase stimulus
stomach distension and the presence of food chemicals, & rising pH within the stomach
27
Stomach distension activates activate stretch receptors
which then signals the medulla to send parasympathetic signals via the vagus nerve to the stomach
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The presence of food stimulus
G cells present in the stomach to release gastrin in the blood
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An important hormone that stimulates gastric function
Gastrin
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if pH becomes too excessive (pH<2)
the G cells are inhibited from releasing gastrin
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too much acidity can cause
damage to the GIT, it is important that the body regulate the acidity produced within the stomach
32
Emotional stress (any stress) can
inhibit gastric secretions because of the subsequent increased sympathetic stimulation that would override the parasympathetic stimulation
33
Intestinal phase is made up of:
stimulatory and inhibitory components
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"off switch" phase needed to inhibit gastric secretions
intestinal phase
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as digesta leaves the stomach and enters the duodenum of the small intestines
there is an initial increase in stomach secretions
36
nutrients
lipids, carbohydrates and proteins
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as nutrients enter the duodenum
intestinal cells release gastrin, G cells in the stomach are stimulated in the same way to release gastrin (from G cells)
38
Intestinal gastrin
will increase gastric secretions and gut motility, but short-lived
39
as duodenum stretches
enterogastrones are released in response to the duodenal destension and these hormones initiate the inhibitory component, thus triggering the enterogastric relfex
40
the same stimulus for a brief increase in gastric secretion is also the same stimulus that begins inhibiting the gastric secretions by
inhibiting vagal nuceli in the medulla (which sends parasympathetic signals) and inhibiting the pyloric sphincter, which simulate enterogastric reflex.
41
enterogastric reflex
A nervous reflex whereby stretching of the wall of the duodenum results in inhibition of gastric motility and reduced rate of emptying of the stomach. It is a feedback mechanism to regulate the rate at which partially digested food (chyme) leaves the stomach and enters the small intestine
42
Cells in the stomach
mucous neck cells, parietal cells, chief cells, and enteroendocrine cells
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gastric glands
location of cells
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gastric pits
location of gastric glands, mucosa layer of the gastric tissues
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mucous neck cells
secrete mucous and help coat and protect the stomach lining from its acidic contents
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parietal cells
secrete HCl acid as well as intrinsic factor
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HCl acid
important for breakdown of foodstuffs
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intrinsic factor
is required for vitamin B12 absorption in the small intestines
49
Vitamin B12
cannot be synthesized de novo in the body, yet it is still needed for brain and nervous system maintenance as well as red blood cell formation.
50
cheif cells
produce lipases and pepsinogen, an inactive form of pepsin
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Lipases
breakdown fats
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pepsinogen
breaks down proteins once it it has been activated by HCl acid into pepsin
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enteroendocrine cells
releases hormones such as gastrin, somatostatin, and serotonin
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different regions of stomach
fundus, cardia, body, pylorus
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cardiac glands
located within the cardiac region where digesta enters the stomach from the esophagus, are important for mucus secretion
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cardiac region contain
mucus neck cells as well as some endocrine cells
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fundic glands
found in both the fundus and body, are important for HCl acid and pepsinogen production because the bulk of digesta break down would be occurring in the central portion
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fundus and body region contain
parietal cells and cheif cells, mucous cells and endocrine cells
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pyloric glands
concentrated near where the digesta exits the stomach and enters the duodenum, contain mucus neck cells and G cells primarily
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gastrin stimulates
HCl secretion in the stomach and muscular contractions of the small intestines, its released from G cells
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Lysozymes
released from the epithelial cells of the pylorus and is important because of its antimicrobial activity
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2 acts of defense in the GIT
HCl acid and lysozyme
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histamine
can act as a NT, & is released from enterochromaffin-like cells activate the parietal cells to release HCl
64
Serotonin
causes contraction of the stomach muscle, which aids in digestion
65
Somatostatin
stimulated by sympathetic nerve fibers, inhibits secretions of the stomach, pancreas, small intestines, and gallbladder
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major inhibitor of gastrin and histamine
somatostatin
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a paracrine in the stomach
somatostatin, because it signals cells in proximity
68
Liver
metabolism and regulation, produces bil
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bile
alkaline substance that emulsify fats, digestion of lipids in the small intestine
70
metabolic role of the liver
it receives venous blood from the intestines carrying absorbed nutrients and thus, the liver can metabolize those nutrients.
71
the liver uses what to make bile?
cholesterol, triglycerides, phospholipids, electrolytes, bile salts, and bile pigments
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where is bile stored?
the gallbladder until needed
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Bile salts and phospholipids
are the only 2 substances of bile that specifically act on fat emulsification
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when bile is needed what hormone is released?
cholecystokinin (CCK), it stimulates gallbladder contraction and sphincter of Oddi relaxation in order to released the bile into the duodenum
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bile patheway
traverses through the Small Intestines, it can;
- -exit the body via fecal matter
- -be recycled by being reabsorbed in the ileum
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enterohepatic circulation
recycled by being reabsorbed in the ileum in a process
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if bile is recycled
the bile salts can be recirculated 2, or even 3 times during each meal
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Pancreas
conjunction with insulin, the hormone released after consuming a meal that helps regulate our glucose levels
79
pancreatic juice
water, enzymes, and electrolytes
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pancreas alkaline
pH 8, helps balance the more acidic secretions exiting the stomach
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hormones acting on the pancreas?
secretin and CCK, stimulate pancreatic juice secretions
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vagal stimulation in pancreas
initiate pancreatic juice release
83
during which phases would you suspect the greatest vagal stimulation on the pancreas to occur?
cephalic and gastric phase require vagal stimulation of the pancreas
84
the pancreas releases enzymes that
can breakdown every type of foodstuffs; amylases, lipases, nucleases, and proteases
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amylases
break down starch
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lipases
break down fats
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nucleases
break down nucleic acids
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proteases
break down protein
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trypsin
is a protease released into the duodenum via the pancreatic duct through the ampulla of Vater
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zymogen
released in inactive form
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trypsinogen
inactive form of trypsin, once its released into the duodenum it comes into contact with the enteropeptidases of the brush border to be converted into its active form trypsin
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trypsin can activate
its own and other inactive forms and proteases like; chymotrypsinogen and procarboxypeptidase into active forms chymotrypsin and carboxypeptidase
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bile from the gallbladder
joins the pancreatic juices prior to entry into the duodenum.
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Upon hormonal stimulation of CCK
the gallbladder contracts and releases bile into the cystic duct, the cystic duct joins the common hepatic duct to form the common bile duct, then going into the pancreas
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bile is NOT released in the
pancreatic tissues, it joins the pancreatic duct
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CCK also stimulates enzyme secretion
from the pancrease
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Secretin
hormone that initiates bicarbonate is released from the pancreas
98
joining of the pancreatic duct and common bile duct
both bile and pancreatic juices are released together into the duodenum.
99
The enterogastrones, or intestinal hormones, that are released during the enterogastric reflex, include;
secretin, CCK, and vasoactive intestinal peptide (VIP), and are released in response to the presence of lipids, the promote secretions of the pancreas & gallbladder as well as inhibition
100
why is inhibition important in enterogastric reflex
because now that acidic chyme is entering the small intestines at a steady pace, we no longer need gastric secretions, nor would it be wise to have continued acidic secretions that could overload the small intestines
101
brush border
a densely packed layer of microvilli and enzymes that aid in completing the digestion of carbohydrates and proteins
102
intestinal glands secrete
approximately 1-2 L of intestinal juice per day, which aid in promoting the slightly alkaline environment (7.4-7.8 pH) of the intestines
103
intestinal juice
contains large
| amounts of water and some mucus, but poor concentrations of enzymes
104
trigger for intestinal juice secretion
is acidic chyme
105
As the digesta traverses through the
| small intestines
the foodstuffs become broken down and their nutrient values absorbed through the enterocytes and into the blood stream.
106
vasculature that carry nutrients to the liver
superior and inferior mesenteric veins
107
appendix
contains masses of lymphoid tissues that aid in immunity and contain bacteria which help recolonize the gut when needed.
108
Large intestines
absorb water, temporarily store residual digesta (~12-24 hours) before expelling it as fecal matter
109
bacterial flora in large intestines
result in the synthesis of B complex vitamins and vitamin K, & fermentation of indigestible carbohydrates (e.g. cellulose).
110
epiploic appendages
fatty “tags” that attach to the colon, and are especially concentrated in the distal regions of the colon.
-help cushion the colon, play a role in regulating metabolism, and may even carry some immune function
111
haustra
“bulges” in the colon that help to swish the residual digesta around to help reabsorb water and any last nutrients that may be present
112
teniae coli
longitudinal muscles that run along the midline of the colon and are especially prominent in the
transverse colon, help form haustra by its contraction
