Module 13: The Digestive System Flashcards
(141 cards)
1
Q
Mastication
A
The process of chewing.
2
Q
Describe the physical changes food goes through in the body.
A
- Mastication breaks food down into smaller, more manageable chunks.
- The stomach churns and breaks food into smaller pieces.
- Food dissolves in the fluids of the digestive system, which separates molecules from each other.
3
Q
Digestion
A
The breakdown of food molecules into their individual components.
4
Q
Why must food be chemically broken down into smaller components?
A
The body cannot absorb food molecules through physical changes because they are still too big, so it must undergo further separation through digestion.
5
Q
What do proteins break down into?
A
They break down into individual amino acids.
6
Q
What do carbohydrates break down into?
A
Most of the carbohydrates you eat are disaccharides or polysaccharides, and these must be broken down into monosaccharides (simple sugars).
7
Q
What do fats break down into?
A
Fats break down into their constituent fatty acid molecules.
8
Q
What are the two parts of the digestive system?
A
The alimentary canal (the canal through which food travels on its way from the mouth to the anus) and the accessory organs.
9
Q
What is the role of the stomach in digestion?
A
The stomach churns and mixes food with digestive fluids. It temporarily stores the food, but once it has been thoroughly mixed, it sends the mixture, now called chyme, into the small intestine.
10
Q
What is the role of the small intestine in digestion?
A
In the small intestine, the food molecules are digested, and most of the nutrients are absorbed into the bloodstream through its lining.
11
Q
What is the role of the liver in digestion?
A
The liver stores nutrients, makes proteins for the blood such as fibrinogen and prothrombin, cleanses the blood of toxins and wastes, and produces a fluid called bile, which aids in the mechanical digestion of fats.
12
Q
What is the role of the gallbladder in digestion?
A
The gallbladder concentrates and stores bile from the liver. It releases this concentrated bile into the small intestine, where it aids in the digestion of fats coming from the stomach.
13
Q
What is the role of the pancreas in digestion?
A
The pancreas produces its own digestive juice, which is released into the small intestine to aid in the digestion of the food molecules.
14
Q
What is a possible role of the vermiform appendix in digestion?
A
It may be responsible for housing good bacteria, and if the biofilms are shed in the intestines, the good bacteria could emerge from the appendix and repopulate the lining of the intestine before more harmful bacteria could take hold.
15
Q
Biofilm
A
A delicate layer of beneficial microbes, mucus, and immune system molecules exist on what are known as biofilms in the intestines and appendix.
16
Q
What are the components of saliva?
A
Water (about 99%), mucus, amylase, lysozyme, and antibodies.
17
Q
What is the purpose of saliva?
A
Saliva dissolves food. Also, it is essential to the sense of taste. In order for the taste buds to function, the food you are eating must be dissolved in the the saliva so it can enter the taste pore of the taste bud.
18
Q
What is the role of mucus in saliva?
A
The mucus provides for lubrication so the food can travel more easily down the alimentary canal.
19
Q
What is the role of amylase in saliva?
A
Amylase is a digestive enzyme that helps to break down starch into maltose, which is a disaccharide.
20
Q
Name the three major pairs of salivary glands.
A
The parotid salivary glands, the sublingual salivary glands, and the submandibular salivary glands.
21
Q
Bolus
A
A soft lump of food that has been chewed.
22
Q
Deglutition
A
The act of swallowing.
23
Q
To make food go down the esophagus safely, what steps steps must happen automatically?
A
The airway must be closed off. Therefore, when you swallow, the soft palate rises up and closes off the nasal cavity, which opens into the upper part of the pharynx. At the same time, the larynx rises and the epiglottis drops, sealing off the larynx so that food cannot travel down into the trachea.
24
Q
What are the three stages of deglutition?
A
The voluntary oral stage, the pharyngeal stage, and the esophageal stage.
25
Summarize the voluntary oral stage of deglutition.
The bolus is pushed toward the back of the mouth by the tongue. As the bolus reaches the pharynx, the pharyngeal stage begins.
26
Summarize the pharyngeal stage of deglutition.
The soft palate lifts up and blocks the nasal cavity. At the same time, the larynx lifts up to meet the epiglottis, closing off the larynx and trachea below ti. The vocal folds also move together to form a tight seal in the trachea. Then, the pharyngeal muscles constrict to push the bolus toward the esophagus.
27
Summarize the esophageal stage of deglutition.
Rings of muscle contract and relax to push the bolus down the esophagus. This process is called peristalsis.
28
Peristalsis
The process of contraction and relaxation of circular smooth muscle that pushes food through the alimentary canal.
29
How is peristalsis controlled?
The reflex is initiated by the bolus. The pressure of the bolus at the pharynx sends a message to the pons and medulla oblongata.
30
What are the two main functions of the stomach?
It acts as a storage chamber and can expand considerably without much increase in pressure, and it acidifies the food entering it.
31
What two things does acidifying the food in the stomach do?
First, it kills most bacteria and other microorganisms that may be in the food. Second, the enzymes within the stomach that are used to digest proteins work better at an acidic pH so acidifying the food enhances the digestion of proteins.
32
What are the four main regions of the stomach?
The cardiac region, the fundus, the body, and the pylorus.
33
Visceral peritoneum (the serosa)
The outer layer of the stomach made of a thin layer of connective tissue and a thin layer of simple squamous epithelium.
34
What three layers of smooth muscle make up the muscularis?
The longitudinal muscularis, the circular muscularis, and the oblique muscularis.
35
The submucosa
A layer of connective tissue that contains blood vessels and nerves that loosely binds the muscularis to the mucosa.
36
Gastric juice
The acidic secretions of the stomach.
37
Why doesn't the strong acid in the stomach hurt it?
Cells near the top of the gastric pits secrete an enormous amount of mucus, so much that the gastric juice never actually touches the tissues of the stomach.
38
What is the acid in gastric juice called?
Hydrochloric acid (HCl).
39
Pepsin
An enzyme activated by the acid in gastric juice which breaks proteins down into smaller chains of amino acids called peptides.
40
Why do the gastric glands make pepsinogen?
This chemical, when mixed with HCl and other pepsin molecules, can be converted into pepsin. A cell cannot make active enzyme (pepsin) because it would break down its own proteins, so instead, it makes pepsinogen.
41
What role does intrinsic factor play in gastric juice?
Without intrinsic factor, the body could not absorb vitamin B12. IF binds to B12 in order for it to be absorbed later on by the small intestine.
42
Adventitia
A thin layer of loose connective tissue that binds an organ to surrounding tissues or organs.
43
How does the stomach make chyme?
It mixes the boluses with gastric juice to form chyme. The smooth muscle of the stomach contracts and relaxes in a rhythmic pattern to form mixing waves. These waves blend the boluses with the gastric juice to make chyme. As the liquefied food mixes with the gastric juice, it also mixes with pepsin so that the proteins can be broken down into peptides.
44
How is peristalsis different from mixing waves in the stomach?
Peristalsis forces the chyme down the stomach into the pylorus, but peristaltic waves are weak. The mixing waves swish the chyme back and forth in the stomach while slow, weak peristaltic waves push the chyme through the pyloric sphincter into the small intestine.
45
Explain the process of vomiting.
When the lining of the alimentary canal becomes irritated, action potentials travel to the medulla oblongata, which initiates the vomit reflex. The larynx elevates; the soft palate closes off the nasal cavity; the upper and lower esophageal sphincters open; and the diaphragm and abdominal muscles contract strongly. This compresses the stomach and forces the contents of it to travel back up the esophagus and out the mouth.
46
What does the hormone gastrin do?
Secreted by the stomach, it increases lower esophageal sphincter tone. This makes the sphincter contract more strongly and avoid having gastric juice back up into the esophagus, which causes gastroesophageal reflux, or heartburn. It also decreases the pyloric tone, which increases the rate at which the stomach empties. It increases the rate of secretion from the gastric pits and the rate of mixing waves of the stomach.
47
What are the three main functions of the small intestine?
1. To mix and propel the chyme.
2. To digest the food.
3. To absorb the nutrients.
48
What are the three regions of the small intestine?
The duodenum, the jejunum, and the ileum.
49
How are the layers of the small intestine different from the stomach?
They are the same except the small intestine has no oblique muscularis and the duodenum has adventitia instead of serosa.
50
What is the purpose of intestinal villi?
They increase the amount of intestinal surface that comes into contact with the food, speeding up the absorption process.
51
Microvilli
Microscopic extensions of the cell membrane that cover the epithelial cells of the villi.
52
Where do fatty acids (the components of fats) go after being absorbed by the villi of the small intestine?
They do not enter the blood capillaries. Instead, lacteals carry fat-soluble nutrients to the blood by making them part of the lymph. When lymph ultimately gets returned to the bloodstream, the fat-soluble nutrients enter the circulatory system as well.
53
Lumen
The space in the center of a tube.
54
Mucous goblet cells
Exocrine glands which secrete mucus. This mucus protects the tissue of the intestine from the chyme, as well as from the digestive enzymes. These cells can be found all over the small intestine.
55
Why do the duodenal glands secrete an alkaline (basic) mucus?
The chyme has just come from the stomach and is very acidic. The alkaline mucus helps to neutralize the acidity of the chyme.
56
What secretes secretin, and where is it secreted?
The duodenum secretes secretin. Instead of being secreted into the lumen like exocrine secretions, it is secreted into the blood capillaries within the wall of the duodenum.
57
What is the function of secretin, and what controls it?
The acidity of the chyme controls the secretion of secretin. The more acidic the chyme, the more secretin is released. This hormone inhibits the secretion of gastric juice, and it increases the secretions of substances that reduce the acidity of chyme.
58
What is the function of the hormone cholecystokinin?
It is secreted by the endocrine glands of the small intestine, especially in response to fatty chyme. This hormone causes the gallbladder to contract and push bile into the intestine. It inhibits gastric emptying and increases the secretion of digestive enzymes from the pancreas.
59
What is the function of the intestinal hormone gastric inhibitory peptide (GIP)?
This hormone reduces the activity of the stomach.
60
What are the major digestive enzymes in intestinal juice?
Maltase, sucrase, lactase, peptidase, and enterkinase.
61
Explain the breakdown of maltose.
Maltase is the enzyme that breaks down maltose. Maltose is a disaccharide with two glucose molecules bonded together. Maltase breaks up the maltose into two glucose molecules, each of which can be transported across the simple columnar epithelium of the intestinal villi.
62
Explain the breakdown of sucrose.
The enzyme sucrase breaks down sucrose. Sucrose is a disaccharide made of two different monosaccharides: glucose and fructose. Sucrase breaks sucrose down into glucose and fructose, both of which can be absorbed by the intestinal villi.
63
Explain the breakdown of lactose.
The enzyme lactase breaks down lactose. Lactose is a disaccharide, which is made up of one glucose and one galactose. Lactase breaks lactose down into glucose and galactose.
64
Inducible enzyme
An enzyme, that if not stimulated by a sugar for it to break down, eventually stops being produced by the body.
65
What is the function of peptidase?
It breaks down peptides into individual amino acids, which are then small enough to be absorbed.
66
What is the function of enterokinase?
This enzyme does not digest food molecules. Instead, it activates trypsinogen into trypsin.
67
Where does trypsinogen come from?
It is secreted from the pancreas, and it is inactive.
68
What three parts is the large intestine split into?
The cecum, the colon, and the rectum.
69
What does the ileocecal sphincter do?
It connects the small intestine to the large intestine and regulates the amount of chyme leaving the small intestine.
70
The ascending colon
The portion of the colon in which chyme travels upwards.
71
The transverse colon
The portion of the colon in which chyme travels from the right side of the body to the left side at the level of the waist.
72
Descending colon
The portion of the colon in which the feces travels down to the rectum.
73
What is the main job of the colon?
Its main role is to take the liquid chyme coming from the small intestine and to form the feces, which are then eliminated through defecation. The colon also absorbs a large amount of water into the blood by osmosis through its walls.
74
What causes the osmosis of water through the walls of the large intestine?
Sodium ions are actively transported through the wall of the large intestine and into the bloodstream. As a result, the water follows by osmosis.
75
What chemical is responsible for the brown color of feces, and how is it made?
Bilirubin, a chemical produced in the liver, is converted to urobilinogen in the colon. Urobilinogen is responsible for the the brown color of feces.
76
What produces the strong odor associated with feces?
The bacterial breakdown of certain amino acids that are not absorbed in the small intestine results in chemicals that produce the odor.
77
How is flatus produced?
Carbohydrates that could not be broken down into monosaccharides in the small intestine are broken down by the bacteria in the colon. This produces the gas known as flatus.
78
Crypts
Glands in the large intestine that contain goblet cells which produce mucus. This mucus lines the walls of the large intestine, protecting it from acid. It also helps bind the feces together. In addition, the crypts in the large intestine secrete biocarbonate, which is a weak base that neutralizes the acid produced by bacteria.
79
What is the liver's main job in terms of digestion?
The production of bile.
80
What supplies the liver with oxygen?
A large artery called the hepatic artery.
81
Why does the liver need two vessels to bring it blood?
The hepatic artery brings oxygenated blood from the heart to supply the cells of the liver with oxygen. The hepatic portal vein brings blood from the small intestine, stomach, spleen, and large intestine. This blood contains many nutrients so the liver can process them.
82
Describe the structure of a lobule, a division of liver tissue.
A lobule is hexagonal with a portal triad at each corner. A central vein runs through the center of each lobule, which joins other veins in the liver, eventually forming hepatic veins which join together and empty into the inferior vena cava. The hepatocytes radiate outward from the central vein.
83
What three parts make up a portal triad?
Two blood vessels, one that branches from the hepatic portal vein, and one that branches from the hepatic artery. It also contains a bile duct.
84
What direction does blood flow in a lobule?
Blood flows from the edge of the lobule (the portal triads) to the center of the lobule (the central vein).
85
What direction does bile flow in a lobule?
Bile flows from inside the lobule (the hepatocytes) to the edge of the lobule (the portal triad).
86
Describe the basic pathway bile takes.
The hepatocytes of the liver produce and secrete it, it collects in the common hepatic duct, and is sent to the gallbladder.
87
What does it mean for bile to emulsify fats?
Chemicals within the bile, called bile salts, interact with large drops of lipids and separate them into smaller drops. The enzymes that digest fats are water-soluble, so they can only interact at the surface of a droplet of fat. The smaller the droplets, the more surface that is exposed to the digestive enzymes. This speeds up the rate at which fats can be digested.
88
Describe an example of the storage function of the liver.
If there is too much glucose in the blood, the hepatocytes can absorb it and convert it into glycogen, a polysaccharide.
89
Nutrient interconversion
The process by which hepatocytes can convert certain types of nutrients to other types of nutrients. It is a way the liver processes the nutrients that come from the intestines.
90
Name some examples of nutrient interconversion.
The liver can change the monosaccharides fructose and galactose into glucose. Additionally, the hepatocytes can combine nutrients into more useful molecules. Phospholipids, for example, are produced in the liver from fats and other chemicals absorbed in the digestion process.
91
What does the synthesis function of the liver accomplish?
The liver is one of the body's main chemical manufacturing facilities. The liver produces prothrombin, fibrinogen, and many blood coagulation factors.
92
What functions of the liver are accomplished by the hepatocytes?
Bile production, storage, nutrient interconversion, and synthesis.
93
How does the liver engage in phagocytosis?
The hepatic sinusoids contain phagocytic cells. These white blood cells help the spleen destroy worn-out erythrocytes and remove worn-out white blood cells, bacteria, and other debris from the blood.
94
How does the liver detoxify the blood?
Many of the body's natural processes result in byproducts that would be toxic to the body if they were allowed to accumulate. For example, ammonia is a byproduct of the breakdown of amino acids and would be toxic in large amounts. The liver converts ammonia to urea, which is not as toxic.
95
What happens to many of the substances in the blood removed by the hepatocytes?
They are integrated into the bile.
96
How is bile concentrated in the gallbladder?
Salt is actively transported across the inner wall of the gallbladder, and water follows by osmosis. This concentrates the bile, making it more potent.
97
How do gallstones form?
Gallstones are mostly cholesterol. The gallbladder removes water from the bile, which contains cholesterol. If enough water is removed from the bile, the cholesterol will fail to remain liquefied and will solidify into a gallstone.
98
What does the pancreas secrete through the pancreatic duct?
Pancreatic juice.
99
What does pancreatic juice do?
The pH of this juice is generally basic because it contains bicarbonate. This ion helps neutralize the acidity of the chyme coming from the stomach. Pancreatic juice is the fourth basic secretion that neutralizes acid chyme.
100
What three enzymes in the pancreatic juice are used to digest proteins?
Trypsinogen, chymotrypsinogen, and procarboxypeptidase.
101
How is trypsinogen activated in the small intestine, and what does it become?
Trypsinogen is activated into trypsin by enterokinase and other trypsin molecules.
102
How is chymotrypsinogen activated in the small intestine, and what does it become?
Chymotrypsinogen is activated into chymotrypsin by trypsin.
103
How is procarboxypeptidase activated in the small intestine, and what does it become?
Procarboxypeptidase is activated into peptidase by trypsin.
104
What is the role of amylase in the pancreatic juice?
Amylase breaks down polysaccharides into maltose. Maltose is then digested into the glucose molecules by maltase from the intestinal gland.
105
What is the role of lipase in the pancreatic juice?
Lipase breaks down triglycerides into fatty acids.
106
Why do people with chronic pancreatic disease often have the most difficulty with digesting lipids?
The mouth, stomach, and small intestine contain enzymes that digest protein and carbohydrates, but only the pancreas produces enough lipase to digest fat.
107
What is the role of nucleases (enzymes) produced and secreted by the pancreas?
Nucleases break down nucleic acids, which are huge molecules.
108
Macronutrients
The nutrients the body needs in large amounts: carbohydrates, fats, and proteins.
109
Micronutrients
The nutrients the body needs in small amounts, such as vitamins and minerals.
110
Carbohydrates
Carbon-, hydrogen-, and oxygen-based molecules that the body can use as energy sources as well as for other purposes.
111
Why is fiber beneficial to the body, even though it cannot be digested?
Fiber stimulates the intestines by stretching them, which causes the intestinal walls to reflexively contract. This moves the chyme or feces along, which is beneficial because feces contains wastes that need to be removed.
112
Lipids
Oil-soluble molecules made up largely of carbon and hydrogen molecules with oxygen in smaller proportions.
113
Triglycerides
The most common class of lipids in the human body. They are composed of three fatty acid chains bound together in a long E shape by a three-carbon molecule called glycerol. The triglyceride is a compact way of storing fuel for later energy use in the mitochondria of cells.
114
Why is cholesterol an important nutrient?
It is a chemical precursor of the sex hormones estrogen, progesterone, and testosterone, as well as the hormones of the adrenal cortex, including aldosterone. It also maintains the correct level of rigidity in the cell's plasma membrane.
115
Phospholipids
The major components of a cell's plasma membrane. They are not triglycerides; they have only two fatty acid molecules, not three. In place of the third, phospholipids have a phosphate group. This gives it its characteristic of two oil-soluble tails and a water-soluble head formed by the phosphate group.
116
What are the two essential fatty acids?
Linoleic acid (also called the omega-6 essential fatty acid) and alpha linolenic acid (also called the omega-3 essential fatty acid).
117
What do the essential fatty acids do?
They form prostaglandins. The alpha linolenic acid is the precursor of "good" prostaglandins and prevents the "bad" prostaglandins from forming. In addition, essential fatty acids give the right amount of flexibility to a cell's plasma membrane. They also help usher in oxygen through the cell membrane.
118
Essential amino acids
The 9 (out of 20) amino acids in the proteins of the human body that cannot be synthesized by the body. The only way to get them is to eat proteins that contain them.
119
A complete protein
A protein that contains all 9 of the essential amino acids.
120
Vitamins
Highly complex organic molecules that our bodies must have but cannot synthesize.
121
What is the function of vitamins?
Vitamins act mainly as regulators of the chemical processes that occur in the body. Many are coenzymes, which enable cellular enzymes to do their job
122
Which vitamins are fat-soluble?
A, D, E, and K.
123
Which vitamins are water soluble?
C, the B group (B1, B2, B3, B5, B6, B12), biotin, folic acid, and pantothenic acid.
124
What is the role of Vitamin A in the body?
Acts as a component of the process that allows the eyes to detect light and maintains the cells that protect the body, such as skin cells.
125
What does Vitamin D do?
It allows calcium that you eat and drink to be absorbed from the small intestine.
126
What does Vitamin E do?
It is an antioxidant, which means it helps protect important chemicals (such as the essential fatty acids) from being destroyed through oxidation.
127
What do the B vitamins, folic acid, and biotin do?
They are involved in the mitochondria's production of energy from food molecules, and they are involved in cell division.
128
What does Vitamin C do?
It helps to build collagen in bones and teeth and supports the immune processes that help us fight disease.
129
What does Vitamin K do?
It aids in the synthesis of many blood clotting factors.
130
Minerals
Inorganic substances that the body needs to function properly.
131
Which minerals does the body need the most?
Calcium, magnesium, phosphorus, iron, iodine, sodium, chloride, zinc, copper, sulfide, selenium, and potassium.
132
Which minerals make up the bulk minerals?
Calcium, phosphorus, and magnesium.
133
Which minerals make up the trace minerals?
Iron, iodine, sodium, chloride, zinc, copper, sulfide, selenium, and potassium.
134
What is iodine necessary for?
The thyroid gland requires iodine.
135
What is sodium necessary for?
Nerve conduction and water balance.
136
What is chloride necessary for?
The pH balance of the blood and gastric juice production.
137
What is zinc necessary for?
It is used in many enzyme systems and in carbon dioxide transport.
138
What is sulfur necessary for?
It is a component of many of the hormones and proteins the body makes.
139
What is copper necessary for?
Hemoglobin production.
140
What is selenium necessary for?
The production of many enzymes in the body.
141
What is potassium necessary for?
Proper muscle function.
