Digestion/Hormones Flashcards
(110 cards)
1
Q
What do salivary glands secrete?
A
Salivary glands secrete amylase that mixes with food.
Amylase breaks down starch
2
Q
what is one advantage of extracellular digestion?
A
can ingest larger food items
3
Q
what type of digestive system do most animals have?
A
a one-way alimentary canal
4
Q
what are the advantages of an alimentary canal?
A
make the whole digestive process more efficient; because not as much energy needs to be used –> the ability to ingest more food even when not done digesting what was previously eaten
5
Q
what are the organs of the digestive system?
A
mouth, esophagus, stomach, small intestine, large intestine, rectum, anus
6
Q
what are the accessory organs of the digestive system?
A
salivary glands, liver, gallbladder, pancreas
7
Q
where are nucleic acids digested?
A
small intestine
8
Q
how does the mouth contribute to the initiation of digestion?
A
salivary glands release water and glycoproteins called mucins to form mucus. the combination of water and mucus makes food soft and slippery enough to be swallowed
9
Q
what is the function of the esophagus?
A
to propel food to the stomach by peristalsis
10
Q
peristalsis
A
waves of muscle contractions that move food through alimentary canal
11
Q
peritoneum
A
sac that surrounds all organs in abdominal cavity
12
Q
`function of mouth
A
mechanically digests food (mastication), chemically digests food (via enzymes from salivary glands), and transports food via swallowing
13
Q
function of the stomach in digestion
A
store food, chemically digest food via enzyme activity, mechanically digest food via churning (can also absorb LIMITED nutrients including alcohol, caffeine, and aspirin)
14
Q
basic function of small intestine
A
chemically digests food via enzymes from pancreas and bile salts from gallbadder, transports food via peristalsis, absorbs nutrients
15
Q
basic function of large intestine
A
absorbs water
16
Q
basic function of pancreas
A
secretes enzymes into small intestines for break down of food
17
Q
basic function of liver in digestion (what does it secrete)
A
the liver synthesizes bile salts and secretes them as bile
18
Q
how do we avoid food going down the trachea?
A
Food is kept out of the trachea: larynx is constricted, rises up and forward, becomes covered by epiglottis
19
Q
how does the upper and lower part of the esophagus differ?
A
Upper part of the esophagus is skeletal muscle; lower part has circular and longitudinal layers of smooth muscle.
20
Q
what happens when food reaches the lower part of the esophagus?
A
As food reaches the smooth muscle, the esophagus contracts and pushes the food toward the stomach.
21
Q
How do nerves coordinate the muscles of the esophagus?
A
Contraction is preceded by an anticipatory wave of relaxation
As an area contracts, the region below it relaxes so food does not move upwards
As food moves down, it causes the next region to contract
22
Q
What is the role of the lower esophageal sphincter?
A
Prevents food from moving backward into the esophagus.
23
Q
What is the role of the pyloric sphincter?
A
The pyloric sphincter controls the passage of food into the intestine.
24
Q
What types of cells line the walls of gastric pits in the stomach?
A
Parietal cells, chief cells, and mucus-secreting cells (goblet cells) that protect the stomach.
25
What do G cells secrete?
G cells secrete gastrin
26
What is the role of parietal cells?
The parietal cells can create a tremendous H+ concentration difference by actively transporting H+ ions produced through the catalytic action of carbonic anhydrase into the lumen of the gastric pit.
27
What is the role of carbonic anhydrase in digestion?
Carbonic anhydrase catalyzes the formation of H2CO3 from CO2, which dissociates into HCO3– and H+.
28
What is the role of the proton pump in digestion?
Proton pump exchanges H+ ions for K+ in the lumen of the gastric pits.
29
What is a gastric pit?
The epithelium of the stomach forms gastric pits. Different types of cells are at different locations down the pits.
30
What are the function of the folds in the stomach?
to allow for expansion
31
what is the pH of the gastric juice in the stomach?
32
What is a lumen, in biology?
In biology, a lumen is the inside space of a tubular structure, such as an artery or intestine.
33
what are the three main elements of the gastric juice in the stomach?
1. HCl (helps convert pepsinogen into pepsin, disrupts the ECF of food, and kills bacteria)
2. pepsinogen (precursor for pespsin which digests proteins)
3. mucus (lubrication and protection)
34
why does the stomach not digest itself?
goblet cells secrete mucous that provides a protective coating for walls of gastric pits and stomach; also, the epithelial cells of the stomach regenerate constantly.
35
Location and function of chief cells
Chief cells are located at the base of gastric pits.
They are responsible for production of pepsinogen.
36
What is pepsinogen?
An inactive precursor of pepsin, which degrades proteins.
37
What is the role of pepsinogen in the stomach?
to become pepsin, an enzyme that breaks down proteins
38
Gastrin
released by the stomach into the blood
39
Cholecystokinin
in the small intestine, causes gallbladder to release bile, stimulates pancreas, slows stomach
40
Secretin
in the duodenum, causes pancreas to secrete bicarbonate buffer
41
Why is it recommended to ingest bismuth to prevent/help with gastric ulcers?
Because it is a strong base which neutralizes HCl thus reducing the effects of the ulcer
42
salivary amylase
starch -> maltose (disaccharide)
43
pepsin
proteins -> peptides; autocatalysis
44
important digestive enzymes from pancreas
pancreatic amylase, lipase, nuclease, trypsin
45
important digestive enzymes in small intestine
enterokinase, nuclease, maltase, lactase, sucrase
46
pancreatic amylase
starch -> maltose
47
lipase
fats -> fatty acids and glycerol
48
nuclease
nucleic acids -> nucleotides
49
trypsin
proteins -> peptides; zymogen activation
50
enterokinase
trypsinogen -> trypsin
51
nuclease
nucleic acids -> nucleotides
52
maltase
maltose -> glucose
53
lactase
lactose -> galactose and glucose
54
sucrase
sucrose -> fructose and glucose
55
How does pepsinogen become pepsin?
The low pH of the stomach converts pepsinogen to the active form (pepsin).
56
autocatalysis.
Newly active pepsin activates other pepsinogen molecules
57
What are ulcers?
Ulcers are sites of damage to the stomach lining
58
How does one get ulcers?
Stress and lifestyles that lead to excess stomach secretions, especially HCl, were
thought to be main culprits.
Warren and Marshall noted that ulcer patients were infected with a bacterium, which they later showed was H. pylori.
59
What is H. pylori?
A bacterium that survives in the stomach by an enzyme reaction that neutralizes acid.
Antibiotics are able to cure ulcers caused by H.pylori.
60
Where does most chemical digestion occur?
Most chemical digestion occurs in the small intestine
61
How does food arrive at the small intestine?
The stomach walls contract and move chyme to the bottom of the stomach
The stomach releases contents to the small intestine in spurts of small volumes of fluid.
62
What is chyme?
Chyme is an acidic mixture of gastric juice and partly digested food
63
What is the barrier from the stomach to the small intestine?
The pyloric sphincter; it allows small amounts to enter the small intestine.
64
What are the three sections of the small intestine? (in order)
1) Duodenum
2) Jejunum
3) ileum
65
Duodenum
the initial section of the small intestine and the site of most digestion
66
Jejunum and ileum
carry out ~ 90% of all the absorption of nutrients
67
Ducts of the gallbladder and pancreas
Bile produced in the liver leaves the liver via the hepatic duct.
Branching off this duct is the gallbladder, which stores bile.
Below the gallbladder, the hepatic duct is called the common bile duct and is joined by the pancreatic duct before entering the duodenum.
68
What signals the gallbladder to release bile?
Fat signals the gallbladder (via cholecystokinin, (CCK)) to release bile by contracting;
before it reaches the duodenum, bile is joined by digestive juices delivered by the pancreatic duct.
69
what are lipases?
Bile contains salts that emulsify fats and expose them to lipases—enzymes that digest fats.
70
what are micelles?
Micelles are small lipid particles that result from the action of bile salts.
71
What happens to the products of fat digestion?
The products of fat digestion are absorbed by intestinal mucosal cells, where they are resynthesized into triglycerides and exported to lymphatic vessels.
72
Exocrine functions
Exocrine functions include secretions through the pancreatic duct to the gut lumen, via the common bile duct.
73
Endocrine functions
Endocrine functions include release of hormones (insulin, glucagon) that maintain blood glucose homeostasis
74
How are zymogens related to the pancreas?
The pancreas secretes enzymes as zymogens.
One zymogen is activated by enterokinase in the duodenum—produces active trypsin that can activate other zymogens.
75
What are duct cells, where are they located?
Located in the pancreas, duct cells secretes HCO3– to neutralize chyme in intestine.
76
Do paracrines and autocrines enter the blood?
Paracrines and autocrines do not enter the blood. Paracrines simply diffuse to nearby cells, and autocrines influence the same cells that release them
77
What are hormones in animals?
Animal hormones are signaling molecules that are released
| into the circulatory system
78
what allows bile salts to emulsify lipids?
they have a non-polar and polar region that can pull apart the lipid globule and contain it in smaller chunks as it moves through the body
79
how are fats absorbed? where do they enter?
absorbed by diffusion because they are non-polar and can permeate the phospholipid bilayer; they enter the lymphatic system
80
three classes of animal hormones
1) peptides/proteins
2) steroid hormones
3) amine hormones
81
steroidal hormones
Steroid hormones are modified from cholesterol molecules.
| They include the corticosteroids produced by the adrenal gland and the sex steroids produced primarily by the gonads
82
Peptides/proteins class of hormone
The largest hormone molecules are peptides and proteins. This class includes insulin and growth hormone.
83
Steroid hormone properties
```
Steroid hormones are
lipophilic (hydrophobic),
and most can cross the
plasma membrane to
bind to intracellular receptors
```
84
Amine hormones
Amine hormones are tiny molecules synthesized from a single amino acid. Both epinephrine and thyroxine are synthesized from tyrosine units, but thyroxine is lipid-soluble and epinephrine is water-soluble.
Their modes of release and transport and the locations of their receptors differ accordingly.
85
GLUT transporters
Class I GLUT transporters are tissue-specific in their expression. GLUT 4 is expressed in skeletal muscles, GLUT 2 in liver cells. These are bidirectional transporters that move monosaccharides in or out of cell passively.
86
Endocrine function of pancreas
Insulin triggers glucose uptake by cells throughout the body
87
In regards to glucose, what is the absorptive period?
Insulin is released by the pancreas during the absorptive period, when blood glucose rises.
Insulin promotes uptake and utilization or storage of glucose.
GLUT transporters are inserted in especially large numbers in plasma membranes of skeletal muscle, adipose tissue, and in the liver.
88
post-absoptive period
Blood glucose falls in the postabsorptive period.
Insulin release is lower and glucose uptake is slowed.
If glucose level is very low, glucagon is released and causes the liver to break down glycogen and begin gluconeogenesis.
89
neurons depend mainly on ___
Neurons: depend mainly on glucose (not fatty acids) for energy-production
90
sodium-potassium pump overview (digestion)
The activity of the sodium-potassium pump drives uptake of nutrients, and consequently, osmotic absorption of water into the interstitial fluid
91
what is solvent drag?
Water moving through spaces between cells can carry small nutrients— this is called solvent drag.
92
how do nutrients enter mucosal cells?
Na+ and other ions enter mucosal cells passively (but are indirectly energy-dependent; need energy to drive the sodium-potassium pump).
Symporters combine nutrient molecules with Na+ as it diffuses in—molecules hitchhike.
93
What role does water play in nutrient absorption via symporters?
Nutrient build up in interstitial space drives
| osmotic absorption of water from intestinal lumen.
94
why are lipoproteins necessary for transport of lipids
You would get a huge glob of lipids if lipids were simply released into the bloodstream
95
After they enter the intestinal cells, how are fats trasported?
After they are packed in the ER, lipoproteins are exocytosed through the basolateral membrane into the lymphatic vessel
96
What kind of particles are LDL and HDL?
LDL and HDL are also lipid-protein particles
97
Where does blood from the digestive tract go?
Blood leaving the digestive tract goes to the liver via the hepatic portal vein
No direct connection from gut to major vein or arteries, it goes through the hepatic portal vein
98
Where does the hepatic vein drain to?
The hepatic vein drains blood from the liver to the vena cava and the general circulation.
99
Function of liver cells
Liver cells detoxify plant chemicals, drugs, alcohol, and other substances that could be harmful to the body.
Liver cells absorb nutrients and store them (e.g. sugars, amino acids, iron, vitamins such as D and A) or convert them for special use (e.g. cholesterol, bile salts, LDL and HDL).
The liver can interconvert fuel molecules.
100
Gluconeogenesis
Gluconeogenesis is the conversion of amino acids and other molecules into glucose.
101
The liver can convert amino acids into _______.
The liver can convert amino acids into acetyl groups.
102
Functions of colon (large intestine)
The colon absorbs water and ions, and produces feces by absorption of water from the undigested waste.
Bacterial fermentation produces useful byproducts (vitamin K, beneficial fatty acids)
103
Too much water absorption in the colon leads to what?
Too little water absorption?
Too much water absorption in the colon leads to constipation; too little leads to diarrhea.
104
LDL (low-density lipoprotein) function and characteristics
LDL has much more lipids in it, which is why it’s less dense than HDL
LDL is used as a means of delivering lipids to the rest of the body. Not the same thing as cholesterol, but it does include cholesterol
105
HDL (high-density lipoprotein) function and characteristics
HDL has less lipids in it and more proteins, which is why it’s more dense than LDL
HDL'S job is to remove cholesterol and other lipids from other parts of the body – removal of surplus lipids so that they can be returned to the liver.
106
Where is LDL and HDL made?
Both are made by the liver.
107
What do high HDL levels mean?
High HDL levels means that the body can remove surplus lipids effectively.
108
What do high LDL levels mean?
High LDL levels make people more susceptible to heart disease – Fatty plaques in arteries are caused by arterial walls absorbing excess lipids.
109
How do plaques lead to heart disease?
- Plaques make the arterial walls less flexible by making them stiff, this causes high blood pressure.
- In addition, when blood clots arise in a narrow lumen (caused by plaques) it leads to a heart attack
110
How do saturated fats affect lipoprotein levels?
Saturated fats bump up LDL to HDL ratios in people
