Digestive System part 2 Flashcards
(117 cards)
1
Q
increase in salivation caused by
A
- parasympathetic stimulation of the facial and glossopharyngeal nerves to stimulate salivary glands to increase production
- cerebral cortex mediated salivation caused by sight, smell, sounds, memories of food, and tongue stimulation
2
Q
reduction in salivation caused by
A
sympathetic stimulation: dry mouth feeling stimulates desire for water (thirst)
3
Q
mechanical digestion in the mouth
A
mastication breaks food into pieces and mixes it with saliva to form bolus
4
Q
chemical digestion in the mouth
A
salivary amylase and lingual lipase at work here
5
Q
salivary amylase
A
begins starch digestion of polysaccharides to disaccharides
- is deactivated by stomach acid once swallowed
6
Q
lingual lipase
A
secreted by glands in the tongue but doesn’t do anything in the tongue
- is activated by stomach acids where it breaks down TG into FAs and glycerol
7
Q
where does the bolus travel between the mouth and esophagus?
A
through the pharynx
- deglutition begins here and is facilitated by saliva and mucus
8
Q
esophagus structure (layers)
A
mucosa: stratified squamous with mucous glands at terminal end
submucosa: mucous glands
muscularis: upper 1/3 is skeletal muscle, middle is mixed and lower 1/3 is smooth muscle, it forms sphincters on either end
adventitia: areolar CT that connects esophagus to other structures in mediastinum (only layer of GI sys w/o serosa)
9
Q
upper esophageal sphincter
A
consists of skeletal muscle, thus is under conscious control
10
Q
lower esophageal sphincter
A
consists of smooth muscle, movement of bolus signals opening to let contents into stomach
11
Q
what is the esophagus?
A
a collapsible muscular tube that lies post. to trachea
- it enters mediastinum ant. to vertebrae
- pierces diaphragm at esophageal hiatus
- ends at superior portion of the stomach
function: secrete mucous and transport food from mouth/pharynx to stomach
12
Q
3 stages of deglutition
A
- voluntary stage
- pharyngeal stage (involuntary)
- esophageal stage
13
Q
voluntary stage of swallowing
A
tongue moves upward into soft palate and bolus is pushed into oropharynx
14
Q
pharyngeal stage of swallowing
A
involuntary
- sensory nerves send signals to deglutition centre in brainstem (triggered by bolus entering esophagus)
- soft palate is lifted to close nasopharynx
- larynx lifts and epiglottis bends to cover glottis
15
Q
esophageal stage of swallowing
A
- when bolus enters esophagus the upper sphincter relaxes when the larynx is lifted
- peristalsis moves bolus through esoph.
- travel time is 4-8 sec for solids and 1 sec for liquid to move through esoph.
- lower sphincter relaxes when food approaches, allowing bolus to enter stomach
16
Q
peristalsis
A
circular fibers behind bolus contract, then longitudinal fibers in front of bolus shorten distance of travel
17
Q
4 main regions of the stomach
A
fundus
cardia
body
pyloric region
18
Q
fundus region of stomach
A
- most superior
- holding area for bolus up to one hour so salivary amylase is still active because bolus doesn’t contact gastric juices while it’s here
19
Q
cardia
A
region of stomach closest to esophageal sphincter opening
20
Q
body of stomach
A
largest region
- responsible for churning, mixing contents
21
Q
pyloric region of the stomach
A
has 3 parts
pyloric antrum: triangle shaped region, entrance to pyloric part
pyloric canal: leads to SI
pylorus: gateway controlled by pyloric sphincter (muscularis layer) to SI
22
Q
lesser curvature of the stomach
A
lesser omentum is an extension of serosa in regions of lesser curvature
23
Q
greater curvature of the stomach
A
more lateral side of the stomach
greater omentum begins here and does folding
24
Q
rugae of mucosa
A
found in the body of the stomach
- ridges that allow for expansion as the stomach fills
25
muscularis layer in the stomach
there are 3 layers rather than 2
- longitudinal, circular, oblique
- purpose is to liquify bolus and create even more peristaltic action to churn food
26
functions of the stomach
1. mix food, saliva, gastric juices to from chyme
2. serve as reservoir for food before SI
3. secrete gastric juice (HCl, pepsin, intrinsic factor, gastric lipase)
4. gastrin (hormone secreted by endocrine cells signals digestive processes)
27
gastric glands
columns of secretory cells at the base of projections in the lamina propria
28
gastric pits
narrow channels formed by gastric glands
29
what types of cells are found in the stomach
```
surface mucous cell
mucous neck cell
parietal cell
chief cell
G-cell
```
30
surface mucous cell
found in stomach
secretes slightly alkaline mucus to protect cells from stomach acid
- does the same thing as mucous neck cells
31
parietal cell
found in stomach
| secretes HCl and intrinsic factor
32
mucous neck cell
found in stomach
secretes slightly alkaline mucus to protect cells from stomach acid
- does the same thing as surface mucous cell
33
chief cell
found in stomach
| secretes pepsinogen and gastric lipase
34
G-cell
a type of enteroendocrine cell found in stomach
typically found in pyloric antrum region of stomach
- secretes the hormone gastrin into the blood supply which controls digestion inn other regions of the GI tract
35
mechanical digestion in the stomach
- fundus stores bolus up to 1 hr
- peristaltic waves start as soon as bolus enters and are coordinated with contractions that mix the bolus with gastric juices (occur every 15-25 seconds)
- body of stomach responsible for vigorous mixing via propulsion and retropulsion
36
propulsion
pushing fluids ands bolus towards pyloric region
37
retropulsion
large particles that haven't been broken down yet get pushed back to the body of the stomach for further breakdown
38
gastric emptying
- pyloric sphincter slightly open to allow small amounts of chyme to enter the small intestine
- at any time there is 3ml passing through
39
chemical digestion in the stomach
enzymes involved: HCl, pepsin, pepsinogen, gastric lipase and lingual lipase
- further protection by mucus produced by surface mucous cells and mucous neck cells
40
absorption in the stomach
very minimal
| - water, ions, alcohol, drugs (ex. aspirin)
41
HCl
denatures proteins
kills microbes
- activates pepsinogen
42
pepsinogen
the inactive form of pepsin, activated by HCl
| it's inactive to keep it from digesting the chief cells it's released from
43
pepsin
digests proteins in low pH regions
| - optimal pH of 2
44
gastric lipase in the stomach
has limited role in digestion of lipids in the stomach because its optimal pH is 5-6
45
lingual lipase in the stomach
becomes active in high acid env't of stomach and helps break down TG
46
HCl production in the stomach
H+ comes from dissociated bicarbonate ions
- the HCO3- goes into the blood supply creating an alkaline tide, which changes the blood pH slightly
Cl- enters parietal cell by way of an antiporter from the chloride shift and Cl- is secreted into the stomach env't
HCl is formed in the stomach and not in the cell so it doesn't damage the cell it's coming from
47
when and where do the pancreas and liver add their secretions?
they add their secretions at the beginning of the small intestine
48
pancreatic duct
tube that runs through the pancreas and collects pancreatic juice
- splits into accessory duct and hepatopancreatic duct
49
hepatopancreatic ampulla
where the common bile duct (liver) and other part of pancreatic duct join to add secretions to SI
- opening controlled by a sphincter
50
what types of cells are found in the pancreas?
```
acini cells
islet cells (Islets of Langerhans)
```
51
acini cells
exocrine glands
99% of pancreatic cells
- produce and secrete pancreatic juice, digestive enzymes and secrete it into the pancreatic duct
- surround islet cells
52
islet cells
```
Islets of Langerhans
1% of pancreatic cells
- endocrine cells that secrete hormones into blood capillaries
ex. insulin is secreted by beta cells
glucagon is secreted by alpha cells
```
53
pancreatic juice
composed of water, digestive enzymes and sodium bicarbonate
54
sodium bicarbonate
deactivates pepsin
makes pancreatic juice alkaline (pH 7-8)
serves as a buffer for acidic contents entering the SI
55
enzymes present in pancreatic juice
```
pancreatic amylase - starch
pancreatic lipase - main breaks down TG
proteases: trypsinogen -> trypsin
- chymotrypsin
- carboxypeptidase
- elastase
ribonuclease
deoxyribonuclease
```
56
trypsinogen
protease present in pancreatic juice activated by enterokinase (a brush border enzyme of duodenum)
- forms trypsin, the active form that activates chymotrypsinogen, procarboxypeptidase, and proelastase
57
functions of the liver
```
bile production
storage
detoxification
phagocytosis
activates vitamin D
metabolism of CHO, PRO, lipids
```
58
storage in the liver
CHO and lipids as energy
fat soluble vitamins: A, D, E, K, B12
minerals: copper, iron
59
detoxification in the liver
drugs, alcohol, hormones (thyroid and estrogen)
| - things that aren't found normally in the body and are broken down so they aren't toxic
60
major duodenal papilla
ridge in SI where ducts empty (hepatopancreatic ampulla empties here)
61
lobes of the liver
2 lobes, the right is larger than the left
62
gallbladder layers
mucosa: simple columnar epithelium - rugae allow for distention
no submucosa
muscularis layer is a single layer of smooth muscle with fibers that run in all directions
serosa or visceral peritoneum
63
function of gallbladder
store and concentrate bile by removing water and ions (makes 10x more concentrated)
64
filling the gallbladder
when bile travels down common bile duct, it its sphincter is closed at the hepatopancreatic ampulla, the bile travels back into the gallbladder and fills it
65
bile
produced by hepatocytes
800-1000mL/day
- brownish-yellow or olive green colour depending on concentration level
pH 7.6 to 8.6 - helps make chyme less acidic
- excretory function: bilirubin and broken down drugs and alcohol
- digestive function: emulsifies fat for digestion
66
components of bile
- water
- cholesterol
- bile salts (Na and K salts) for emulsification of fat globules and lipid absorption
- bilirubin (bile pigment from heme broken down into iron and bilirubin from Hgb) forms stercobilin in intestine and gives feces brown colour
67
blood supply to the liver
- hepatic artery delivers oxygenated blood
- hepatic portal vein carries deoxygenated blood but has nutrients (also for detoxification)
- hepatic vein carries deoxygenated/detoxified blood back to the heart
68
how is the liver tissue organized in general
3 dimensional hexagonal arrangements of hepatocytes
69
hepatic laminae
sheets of hepatocytes
70
hepatic sinusoids
lined w endothelial cells (something like capillaries) located b/w hepatic laminae
- connect and mix blood from hepatic artery and hepatic portal vein which exits the central vein
71
central vein (liver)
joins together veins to lead blood to the inferior vena cava and to the heart
72
portal triad (liver)
composed of a bile duct, branch of the hepatic artery and branch of hepatic portal vein, loc towards the outside of hexagon shaped organized hepatocytes
73
bile canaliculi
small canals that run b/w each hepatocyte that lead to bile ducts
- bile travels toward the triad on the outside of the hexagon shaped arrangements
74
kupffer cells
aka stellate reticuloendothelial cell, found in the liver
- digests foreign material that has gotten as far as the liver
breaks down worn out red and white blood cells
75
bile flow
```
right and left hepatic duct
common hepatic duct
also from cystic duct (from gallbladder)
common bile duct (joins w hepatopancreatic duct/ampulla)
duodenum
```
76
blood flow in the liver
```
hepatic artery and hepatic portal vein drain to
hepatic sinusoids to
central vein to
hepatic vein to
inferior vena cava to the heart
```
77
carbohydrate metabolism in the liver
- maintenance of blood glucose levels
- glycogen storage/glucose release
- gluconeogenesis
- convert fructose and galactose into glucose
78
lipid metabolism in the liver
- TG storage/FA release
| - synthesis of lipoprteins (HDL/LDL) and cholesterol
79
protein metabolism in the liver
deamination: detoxifiying AAs
| - also produces plasma proteins, albumin and fibrinogen
80
gluconeogenesis
building glucose from metabolic byproducts
| - uses some amino acids (ex. alanine), glycerol, lactate
81
deamination
detoxifying amino acids by removing NH2 (the amino group) from the AA to use what's left for energy
- NH2 is converted to NH3 (ammonia which is toxic) which is converted into urea for excretion by the kidneys
82
small intestine
3 metres long (6.5 after death), 2.5 cm diameter, large surface area for absorption
3 parts: duodenum, jejenum, ileum
83
duodenum
25 cm long
C-shaped
retroperitoneal
84
jejenum
1 m long
| lots of absorption here
85
ileum
2 m long
| connects to large intestine at ileocecal sphincter (since opening to LI is cecum)
86
circular folds
fingerlike projections in submucosa that form a spiralling pattern, that chyme spins around and keeps contact w the walls
- highly vascularized layer in submucosa for absorption
87
villi
fingerlike projections in lamina propria layer of mucosa with different types of cells
- highly vascularized w blood capillaries and lacteals
88
lacteal
extension of lymphatic vessels in villi
89
microvilli
make fuzzy border that contain brush border enzymes which help breakdown food more
- gives fuzzy look to inside of SI and increases surface area for absorption
90
types of cells in mucosa layers of small intestine
absorptive cells
goblet cells
enteroendocrine cells
paneth cells
91
absorptive cells
found in small intestine, absorb nutrients and contain enzymes for digestion produced by intestines
- enzymes produced from these cells get stuck in brush border on microvilli on top of these cells
- found on top of villus and are mixed throughout also
92
enteroendocrine cells of the small intestine
secrete hormones secretin and cholecystokinin
93
paneth cells
```
found in small intestine on villi
secrete lysozyme (regulates microbial nature inside digestive tract)
also capable of phagocytosis
```
94
intestinal juice
secreted by intestinal glands in mucosal layer by absorptive cells
1-2 L secreted/day
pH 7.6 which is more optimal for enzymes in this region
- consists of water, mucus, and bicarbonate ions
95
brush border enzymes
enzymes released from absorptive cells don't get released into lumen, but get embedded into brush border of microvilli membranes instead
- last chance for breakdown into absorbable components
96
what enzymes are a part of the brush border enzymes
CARB ENZYMES: alpha dextrinase, maltase, sucrase, lactase
PROTEIN ENZYMES: aminopeptidase, dipeptidase
NUCLEOTIDE ENZYMES: nuleosidases, phosphatases
97
types of mechanical digestion in the SI
segmentation
| migrating motility complex
98
segmentation
local mixing of chyme with intestinal juices and swishing back and forth
- triggered by distention of walls of small intestine. when volume of chyme decreases again, then segmentation stops
99
migrating motility complex
squeezing one end of small intestine from stomach to ileum with both types of muscles and peristaltic movement
- takes 1.5 to 2 hours and is thought to cause stomach rumbling sounds when hungry
100
how long does chyme stay in the small intestine?
3-5 hours in total
101
where does absorption occur?
90% small intestine
| 10& stomach and large intestine
102
what is the absorbable unit of carbs in the small intestine?
monosaccharides: glucose, fructose, galactose
103
what is the absorbable unit of lipids in the small intestine?
free fatty acids, glycerol and monoglycerides
104
what is the absorbable unit of proteins in the small intestine?
primarily single amino acids, dipeptides and tripeptides
105
glucose and galactose absorption in the small intestine
- pass through apical surface by secondary active transport using Na+ conc. gradient
- glucose and galactose compete for the same protein channel
- cross basolateral surface by way of facilitated diffusion
106
fructose absorption in the small intestine
passes through apical and basolateral surfaces via facilitated diffusion
107
amino acid absorption in the small intestine
- pass through apical surface via active transport or secondary active transport with Na+
- pass through basolateral surface via simple diffusion
108
dipeptide and tripeptide absorption in the small intestine
- pass through apical surface by way of secondary active transport with H+
- pass through basolateral surface via simple diffusion
109
small short chain FAs (10-12C) absorption in the small intestine
- simply diffuse through apical and basolateral surfaces
110
long chain fatty acids (>12C) and monoglycerides
- bile salts surround long chain FAs and form a micelle which picks up and drops off into other side of apical cell surface by simple diffusion
- TG are surrounded by chylomicrons (proteins that are too big to enter capillaries) so they enter the lymphatic system through a lacteal of a villus
- then travel through thoracic duct (central lymphatic vessel) to junction of left internal jugular and subclavian veins
111
emphysema
- when alveolar surface walls on inside start to breakdown and you end up with balloon lungs instead of bunches of grapes for lungs
- a types of COPD usually caused by external env'tal factors, characterized by difficulty breathing, shortness of breath
112
COPD
chronic obstructive pulmonary disorder
113
pulmonary function tests
FEV1: forced expiratory volume in 1 second
FVC: forced vital capacity
114
hallmark test for emphysema
FEV1 bc if it's low relative to your vital capacity, it signals that you can't exhale fast enough
- shows a decrease in the elastic recoil of the lungs due to loss of elastic fibers
- air becomes trapped in lungs and gets "stale" which gives feelings of shortness of breath
115
treatment options for emphysema
bronchodilators
inhaled steroids
oxygen therapy
116
bronchodilators as treatment for emphysema
drugs that help relieve coughing, shortness of breath and breathing problems by relaxing constricted airways
117
inhaled steroids as treatment for emphysema
corticosteroid drugs inhaled as aerosol spray to decrease inflammation and may help relieve shortness of breath
