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HUMAN PHYSIOLOGY > GASTROINTESTINAL > Flashcards

GASTROINTESTINAL Flashcards

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1
Q

Primary Function of the Digestive System

A

Transfer nutrients, water, and electrolytes from ingested food into body’s internal environment

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2
Q

Name the 4 functions that the Digestive System performs

A
  1. Motility
  2. Secretion
  3. Digestion
  4. Absorption
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3
Q

What muscle covers the GI tract besides at the mouth and anus?

A

Smooth Muscle

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4
Q

What muscle is is at your mouth and anus?

A

Skeletal muscle

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5
Q

What contractions do all gut SM experience?

A

Phasic

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6
Q

Name the 2 types of Phasic contractions

A

Propulsive movements regulate the speed in which the content passes through the particular portion of the GI
Mixing movements which facilitates digestion and absorption

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7
Q

T or F: The GI smooth muscle has a constant tone and constant pressure on the gut content

A

TRUE

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8
Q

Where are secretions released in the GI tract?

A

Digestive tract Lumen

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9
Q

Keep in mind –>

A

Secretions (enzymes for digestion) are released on neural or hormonal stimulation
Normally they are reabsorbed back into the blood after digestion

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10
Q

What is the biochemical breakdown of structurally complex foodstuffs into smaller, absorbable units?

A

Digestion

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11
Q

Digestion occurs via ______

A

Hydrolysis (water breaking)

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12
Q

T or F: Each macromolecule has a specific route or mechanism for absorption

A

TRUE

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13
Q

What does most absorption occur?

A

In the small intestines

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14
Q

Small units resulting from digestion, along with water, vitamins, and electrolytes are transferred from the _____ _____ _____ into the ____ or _____

A

Digestive tract lumen

Blood or Lymph

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15
Q

What does the digestive system consist of?

A

GI Tract
Salivary Gland
Exocrine pancreas
Biliary System - Liver and Gallbladder

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16
Q

What does the GI tract consist of?

A 
ALL CONSIDERED EXTERNAL Mouth 
Pharynx
Esophagus
Stomach
Small Intestine (Duodenum, Jejunum, Ileum)
Large Intestine (Cecum, Appendix, Colon)
Rectum 
Anus
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17
Q

Name the 4 major tissue layers of the GI tract

A

Mucosa - inner greatly increases absorptive area bc its highly folded
Submucosa - thick connective tissue, provides elasticity
Musculares Externa - thick smooth muscle
Serosa - outer lubricates and prevents friction bw digestive organs

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18
Q

What layer of the Gi tract is connective tissue?

A

Submucosa

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19
Q

Which layer of the GI tract lubricates and prevents friction?

A

Serosa

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20
Q

Which layer of the GI tract folds and create absorptive area?

A

Mucosa

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21
Q

Which layer of the Gi tract contains major smooth muscle?

A

Muscularis externa

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22
Q

Name the 4 factors involved in regulating function of the digestive system

A
  1. Autonomous smooth muscle function
  2. Intrinsic nerve plexus
  3. Extrinsic nerves
  4. GI hormones
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23
Q

Autonomous smooth muscle produce slow-wave potentials continuously with _______ cells. This is referred to as ___________

A

autorythmic

BER - Basic electrical rhythm

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24
Q

What is BER of the Digestive system?

A

Basic Electrical Rhythm- an autonomic smooth muscle function that produces slow-wave potentials with auto rhythmic cells that are produced by pacemaker cells (interstitial cells of Cajal)

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25
Are the BER electric potentials action potentials?
NO - they don't cause muscle contractions
26
Instead of creating a muscle contraction, autonomous smooth muscle BER initiates _______________
Rhythmic wavelike fluctuations of the membrane potential closer or further to threshold
27
Which layer of the GI tract holds the nerve network "submucosal plexus"?
Submucosa
28
Which layer of the GI tract holds the nerve network "myenteric plexus"?
Muscularis Externa
29
What does the intrinsic nerve plexus contain?
Submucosal plexus | Myenteric plexus
30
What is the intrinsic nerve plexus (submucosal & myenteric) also called?
Enteric Nervous System
31
What does the extrinsic nerves of the GI include?
Fibers of the autonomic nervous system outside of the GI innervate various digestive organs.
32
What do the extrinsic nerves influence?
- Motility - Secretion - Can act directly on the plexuses
33
Parasympathetic extrinsic nerves are mediated by the _____ nerve and ____ motility and digestive enzyme secretion
Vagus | Increases
34
Acetylcholine is a _______
Neurotransmitter
35
What neurotransmitter acts on cholinergic muscarinic receptors?
Acetylcholine
36
What receptors accept Acetylcholine?
Cholinergic muscarinic receptors
37
Acetylcholine is part of the _______ nervous system
Parasympathetic | Autonomic
38
``` Acetylcholine is known to _______ _______ _______ _______ ```
Contract smooth muscle Dilate blood vessels Increase body secretions Slow heart rate
39
Endocrine glands located in the ______ releases hormones that are carried via blood to other areas of the GI
Mucosa
40
Receptor activation alters the digestive activity through ________ and _________
Neural reflexes | Hormonal Pathways
41
Salvia is composed of
99. 5% H2O | 0. 5% electrolytes and protein (amylase, mucus, lysozyme)
42
What does salivary amylase begin digesting first?
Carbohydrates
43
In salvia _____ destroys bacteria
Lysozyme
44
What are the functions of saliva?
Solvent for molecules that stimulate taste buds Aids in speech Helps to keep the mouth and teeth clean Facilitates swallowing by moistening food Mucus provides lubrication
45
Describe the simple salivary reflex
- >Chemo/Mechanoreceptors respond to food - > Salivary center stimulated in brainstem - > Extrinsic signal sent to salivary glands
46
Describe the conditioned/acquired salivary reflex
Occurs without oral stimulation (ex. Pavlov's dog)
47
Parasympathetic stimulation produces ______ saliva
Abundant, loose
48
Sympathetic stimulation produces ______ saliva
Thick, dry
49
T or F: the mouth does not absorb nutrients and or do much digestion (just a little bit of carbs)
TRUE
50
What is the name of the ball that induces swelling?
Bolus
51
Swallowing is initiated when a bolus is voluntarily forced to the rear of the mouth and pressure stimulates the ______ to signal the swelling center in the _______
Pharyngeal pressure receptors | Brainstem medulla
52
T or F: Swallowing is an all-or-none response
TRUE
53
During swallowing the epiglottis moves down to block the _____
trachea
54
The swallowing center stimulates _______ waves that force the blue ahead of it to continue moving
Peristaltic waves
55
What are the ring-like contractions of smooth muscle that moves progressively forward moving the blue in front of it into the relaxed portion called?
Peristalsis
56
Name the 3 sections of the stomach
1. Fundus (top) 2. Body 3. Antrum (bottom) (Fun Bods Anthem)
57
What are the purposes of the stomach (3)
1. Store ingested food until it can be emptied into small intestine 2. Secretes hydrochloric acid (HCl) and enzymes that begin protein digestion 3. Mixing movements convert pulverized food to chyme
58
What serves as barrier between stomach and upper part of small intestine?
Pyloric sphincter
59
What are the 4 main functions of the stomach?
1. Filling (receptive relaxation) 2. Storage (body) 3. Mixing (antrum) 4. Emptying (duodenum)
60
What is the BER of stomach?
Basal Electrical Rhythm
61
What type of cells generate slow wave potentials in the stomach?
Interstitial cells of cajal *(imagine the stomach mixing making the sound cajal-cajal-cajal-cajal)
62
Where are the interstitial cells of Cajal located in the stomach?
Upper fundus *(fun to mix slow waves)
63
What way to the slow wave potentials of the cells of Cajal move?
sweep down into the antrum and pyloric sphincter at about 3/min *(sweep down anthem gets a py)
64
Describe the BER of the stomach
interstitial cells of cajal generate slow wave potentials that sweep down the antrum and pyloric sphincter at about 3/min
65
Contractions are ____ as you move down the stomach
stronger because muscle is thicker
66
Most mixing takes place in the
antrum
67
The contractions/waves of the stomach are called
Peristaltic contractions/waves (smooth muscle contractitions
68
How is the gastric mixing of the chyme performed?
When the peristaltic contraction reaches a tightly closed pyloric sphincter the chyme is propelled forward and hits the closed sphincter and is then tossed back into the antrum with each peristaltic contraction
69
How is gastric emptying performed?
In upper fundus a peristaltic contraction originates and sweeps down towards the pyloric sphincter. Contraction becomes stronger in antrum. Strong antral peristaltic contraptions propels the chyme forward. Small portion of chyme makes it through partially opened sphincter into the duodenum (denim pants) Stronger contraction = more chyme emptied
70
Name the 3 types of gastric secretory cells that make "gastric juice"
Mucous cells Chief cells Parietal cells (oxyntic)
71
Which gastric juice cell are lined in gastric pits and secrete thin, watery alkaline mucus? What does this do?
Mucous cells protects against acid injury
72
Which gastric juice cell secretes pepsinogen, an enzyme precursor? What does this do?
Chief cells *(the chief has Pepsi coming out of his noggin) begins protein digestion
73
Which gastric juice cell secretes HCl and intrinsic factor?
Parietal cells (oxyntic) HCL - denatures proteins intrinsic factor - absorb B12
74
Which gastric juice cell secretes an intrinsic factor which is important for B12 absorption and RBC production?
Parietal cels (oxyntic) *(intrinsic factor - the parents give you B12 vitamins)
75
Parietal cells secrete HCl which activates ____ and does what?
Activates enzyme pepsin and provides acid medium for pepsin activity Denatures protein Along with salivary lysozyme it kills most microorganisms ingested with food
76
How does HCl via parietal cells denature proteins?
HCl decreases the pH Extreme pH change within lumen Increase in H concentration = lower pH H+ is actively pumped into the lumen via primary active transport Cl- is pumped out via secondary active transport Proteins become peptide fragments
77
How do Parietal cells secrete HCl?
-H+ within the parietal cells is secreted by H+/K+ ATPase pump in the luminal membrane •The K+ passively leaks back in via K+ leak channels •Carbonic anyhdrase facilitates intracellular reaction to form bicarb (HCO3-) that diffuses into the plasma in exchange for Cl-. •Meanwhile, the blood leaving the stomach is high in bicarb and is alkalinic. - "alkaline tide"
78
Pepsinogen is the ____ enzyme produced by ___ cells
inactive | Chief
79
What is autocatalytic activity?
Pepsinogen is secreted HCl cleaves a small portion off to make it active for pepsin Once activated, pepsin activates pepsinogen
80
SOOOO..... THIS WHOLE PROCESS EXPLAINED IS THE AUTOCATALYTIC ACTIVITY
Parietal cells secrete HCl by H/K ATPase pump in luminal membrane Alkaline tide takes place Chief cells secrete inactive pepsinogen HCl cleaves a small portion Pepsin is activated and creates acid medium for activity Activated pepsin activates pepsinogen Protein digestion now begins
81
3 WAYS Gastric secretion is REDUCED all brought about by emptying the stomach
1. Decreased presence of protein (major) 2. Empty stomach 3. Decreased motility (fat, acid, hypertonicity, gastric digestion)
82
Food buffers much of the change in pH from the HCl so ___ food = __ buffer = __ pH
^ food = ^ buffer = ^ pH
83
Gastric emptying is mainly mediated by the ________
duodenum
84
4 Factors in the stomach that regulate gastric emptying
FAT: increased fat in stomach = decreased gastric emptying ACID: un-neutrilized acid in duodenum inhibits gastric emptying HYPERTONICITY: when osmolality of duodenal contents rise = inhibited gastric emptying DISTENTION: increased chyme in duodenum inhibits gastric emptying
85
Things that inhibit or decrease gastric emptying | all in duodenum
``` increased fat un-neutralized acid high osmolality too much chyme hormones decreasing contractions (Secretin and CCK) ```
86
Collectively these inhibitors of gastric emptying trigger (2)
``` Neural response (enterogastric reflex) Hormonal response (enterogastrones) ```
87
The pancreas is a mixture of ___ and ___ tissue
exocrine | endocrine
88
What is the endocrine function of the pancreas? What does it include?
Islets of Langerhans | - secretes insulin and glucagon
89
What does the islets of langerhans secrete?
Insulin and glucagon
90
What is the exocrine function of the pancreas?
secretes pancreatic juice
91
What does pancreatic juice consist of?
Pancreatic enzymes actively secreted by Acinar cells (cck goes here) Aqueous alkaline solution activity secreted by duct cells that line pancreatic ducts (secretin goes here)
92
What cells actively secrete pancreatic enzymes?
Acinar cells
93
What cells secrete alkaline solution in the pancreas?
Duct cells
94
Exocrine secretion is regulated by the hormones:
Secretin (pH) | CCK (fat)
95
Acinar cells secrete what 3 different enzymes?
1. Proteolytic - digest protein 2. Pancreatic amylase - CHO digestion - converts polysaccharides into the disaccharide amylase 3. Pancreatic lipase - fat digestion
96
What is the only enzyme created throughout the entire digestive system that can digest fat?
PANCREATIC LIPASE secreted by Acinar cells
97
Exocrine function is mainly regulated by _______ mechanisms
hormonal
98
Name 3 gastrointestinal hormones
1. Gastrin 2. Secretin 3. CCK
99
Gastrin is secreted by ___ cells in duodenal mucosa
G cells
100
What stimulates the released of Gastrin?
Stimulated by presence of protein in stomach and secreted by G cells (inhibited by acid) Gastrin influences the responsiveness of the smooth muscle during segmentation contractions
101
What are the fns. of Gastrin?
Increases secretion of HCl and pepsinogen Enhances gastric motility and induces mass movements in colon Helps maintain well-developed digestive tract lining
102
Secretin is produced by ___ cells in duodenal mucosa
S cells
103
What stimulates the released of Secretin?
Stimulated by the presence of acid in duodenum
104
What are the functions of Secretin?
Inhibits gastric emptying to prevent acid entering Inhibits gastric secretion - reduce acid produced Stimulates pancreatic ducts cells to produce large NaHCO3 secretion
105
CCK is produced by ___ cells
I cells
106
What are the functions of CCK?
Inhibits gastric motility and secretion Stimulates pancreatic ells to increase secretion of pancreatic enzymes Causes contraction of gallbladder and relax of sphincter of Oddi Regulator of food intake
107
Describe a path of secretin
Acid in duodenal lumen Secretin released from Mucosa to Pancreatic ducts cells Increased secretion of NaHCO3 into lumen acid neutralized
108
Describe a path of CCK
Fat and protein in duodenal lumen CCK released from mucosa to Pancreatic Acinar cells increased secretion of pancreatic enzymes into lumen digestion of fats and proteins
109
SECRETIN - (acid) NEUTRALIZES CCK - (fat or protein) DIGESTS
TRIGGER HORMONE RELEASED TRANSPORT TO DUCT OR ACINAR CELL NEUTRALIZATION/DIGESTION
110
What is the largest and most important metabolic organ in the body?
Liver
111
What is the liver's importance to the digestive system?
secretion of bile salts
112
Biliary system includes:
Liver Gallbladder Associated ducts
113
What is the name of a liver cell?
Hepatocyte ***anything hepato- relates to the liver
114
____ artery supplies O2 and nutrients for the hepatocyte and venous blood enters via the ____
Hepatic artery Hepatic portal vein
115
What is the name of the capillary network in the liver?
Liver sinusoids
116
At each of the 6 corners of the function hexagonal units (lobules) organizing the liver there are 3 vessels. What are they?
Branch of Hepatic artery Branch of Hepatic portal vein Bile duct
117
What is actively secreted by the liver and actively diverted to gallbladder between meals?
BILE
118
Where is bile stored and concentrated?
Gallbladder
119
What does bile consist of ?
Bile salts Cholesterol Lecithin Bilirubin
120
After a meal bile ___
enter duodenum
121
___% of bile salt are reabsorbed by the terminal ileum
95%
122
Reabsorbed bile salts are recycled by the ________
enterohepatic circulation
123
Bile salts aid in ____ digestion and absorption
FAT
124
A bile salt molecule contains a _____-soluble part and a negatively charged ____-soluble part
Lipid-soluble | (-) water-soluble
125
Bile salts act as emulsifiers by helping create ____ | an emulsifier is a water-loving head and oil-loving tail
micelles bile converts large fat globules into a lipid emulsion consisting of many small droplets
126
What is the name of waste product excreted in bile?
Bilirubin | this is the yellow pigment that gives bile a yellow color
127
What is bilirubin derived from?
the breakdown of RBC red blood cells break down to for bilirubin (the bile is rubbin' the red blood cells)
128
More bilirubin production than excretion accumulates and causes ______
Jaundice
129
What are the causes of Jaundice?
1. Prehepatic - excess breakdown of RBC 2. Hepatic - can't deal with min amount of bilirubin 3. Post hepatic - bile duct is obstructed (these mean before, in, and after the liver)
130
Where is the site where most digestion takes place?
Small intestine
131
What are the 3 segments of the small intestine?
Duodenum (top) Jejunum Ileum (near waist)
132
Motility of the small intestine includes
Segmentation | Migrating motility complex
133
What is the primary method of motility in the small intestine?
Segmentation
134
What is segmentation?
Ringlike contractions along small intestine in segments. Contracted segments relay and contract within seconds These actions mix chyme throughout the small intestine lumen
135
What is segmentation imitate by?
Pacemaker cells in small intestine which produce BER
136
What does the circular smooth muscle respond to?
Distension of intesting Gastrin - proteins Extrinsic nerve activity
137
What is the usual transit time in the small intestine?
3-5 hours
138
The frequency of the pacemaker firing is greater in the ____
duodenum 12 min (d) 9 min (i)
139
What is the migrating motility complex? (MMC) - general
sweeps intestine clean between meals
140
When does the Migrating motility complex (MMC) replace Segmentation?
after absorption and the end of a meal
141
What is the MMC? -physiological
weak repetitive peristaltic wave that travels short distances and then dies
142
What hormone is MMC regulated by?
Motolin | just got done eating moto, with Lin
143
When is Motolin secreted?
unfed-not eating states
144
Small intestine enzymes are not digestive enzymes. They complete digestion with the ________ _________
Brushborder Membrane
145
Digestion is also due to _____ enzymes that function in the small intestine
Pancreatic
146
On the brush border membrane in the small intestine there are microvilli which contain what 3 categories of integral proteins? (these proteins fn. as enzymes)
1. Enterokinases - (Trypsinogen - protein digestion) 2. Disaccharideases - (carbs to mono/disaccharides) 3. Aminopeptidases - (protein to AA)
147
____ ____ is required for the B12 and bile salts reabsorption
Terminal ileum
148
Mucous lining is well adapted for absorption because of _____ and _____
huge surface area (highly folded with vili surface with microvilli) specialized transport cells
149
Between the vili in the small intestine there are small invagination called the ____ of ________
Crypts of Leiberkuhn
150
What do theCrypts of Leiberkuhn do?
Secrete water and electrolytes Generation of new cells Migrate up vili and slough off
151
How are epithelial cells in the intestine designed for absorption?
Na+ is low inside of cell and is pumped out of the basolateral membrane via Na+/K+ ATPase pump Carbs and proteins absorbed by 2ndary active transport and enter blood Carbs/proteins absorbed via Na+ dependent symporter
152
Polysaccharides are broken down into _______ and then ________ (CARBS)
Disaccharides then Monosaccharides | glycogen -- v:amylse--> maltose -- v:maltase --> glucose
153
Examples of Disaccharides
Maltose Sucrose Lactose
154
Examples of Monosaccharides
Glucose Galactose Fructose
155
Explain the breakdown of Polysaccharides
- poly broke down to diasac. - then broke down to monosac. on brush border membrane - then absorbed by 2ndary active trans. Na+ and SGLT on luminal membrane - then monos leave cell via facilitated diffusion
156
How are proteins absorbed?
in form of AA and absorbed via Na+ symporters (like glucose) small protein fragments enter via active transport each AA has a specific symporter
157
What is primarily a drying a storage organ?
Large intestine (colon, cecum, appendix, rectum)
158
Contents of the large intestine include:
Indigestible food unabsorbed biliary components remaining fluid
159
What does the colon do? (top of the large intestine)
Extracts more water and salt from contents
160
What are the longitudinal bands of muscle in the large intestine?
Taeniae coli
161
In the large intestine what are the pouches or sacs that actively change location as a result of contraction of circular smooth muscle layer?
Haustra
162
What is the main motility of the large intestine?
Haustral contrations - autonomous rhythmicity of colon smooth muscle
163
INNATE IMMUNITY Inflammation - increased blood flow tissues repair Interferon - interfere with replication Natural Killer cellls - blows up cancer and viruses Complentary - inflammation secretes plasma proteins which create a cascade effect and creates holes in the cell which destroys the cell
Innate immunity

HUMAN PHYSIOLOGY (3 decks)

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