Unit 3: Digestion, Absorption And Transport Flashcards
1
Q
How long is the gastrointestinal (GI) tract
A
26 feet long from mouth to anus
2
Q
What are the 2 principal organs in the GI tract?
A
Stomach (gastrus) and Intestines
3
Q
Where does mechanical and chemical digestion begin?
A
The mouth
4
Q
Define Digestion
A
The breakdown of food into absorbable forms through mechanical and chemical means.
5
Q
Explain Mechanical Digestion
A
- Produces physical changes in food
- Chewing/mixing of food with saliva; prepares the bolus for swallowing
- Bolus enters stomach and further mixing by muscle wall produces chyme
- Peristalsis and Segmentation continue mechanical digestion
6
Q
Explain Chemical Digestion
A
-Chemical breakdown of nutrients into basic absorbable units by the digestive enzymes secreted by specialized glands in the mouth, stomach, pancreas and epithelial cells of the small intestine.
7
Q
Define Gastrointestinal (GI) tract
A
A flexible muscular tube that extends from the mouth, through the esophagus, stomach, small intestine, large intestine, and rectum to the anus.
8
Q
Only when a nutrient or other substance finally penetrates the GI tract’s wall does it enter the body proper (digestion); many materials pass through the GI tract without being digested or absorbed. TRUE OR FALSE?
A
TRUE
9
Q
Explain the function of the mouth
A
- Process of digestion begins
- Process of mastication, blends food with saliva
- Taste buds detect 1 or more of the 4 basic taste sensations (Sweet, sour, bitter, salty)
- The tongue provides sensation and moves the food around the mouth
- Food is swallowed and passes through the pharynx (short tube shared by digestive and respiratory system)
- Epiglottis closes the air way
- Once swallowed food is called a bolus
10
Q
Explain Esophagus
A
- has a sphincter muscle at each end
- during swallowing the upper esophageal sphincter opens
- bolus slides down esophagus, which passes through a hole in the diaphragm to the stomach
- The lower esophageal sphincter at the entrance to the stomach closes behind the bolus to prevent it from reentering the esophagus
11
Q
Explain the Stomach
A
- Retains the bolus in its upper portion for a while
- Little by little the stomach transfers food to its lower portion
- Adds juices and grinds it to a semi-liquid mass called chyme
- Then bit by bit the stomach releases chyme through the pyloric sphincter, which opens to the small intestine then closes behind the chyme.
12
Q
Explain the Small Intestine
A
- At beginning of small intestine, chyme bypasses the opening from the common bile duct, which is dripping fluids from the gallbladder and pancreas.
- Chyme travels through the duodenum, jejunum and the ileum (3 meters of coiled tubing)
13
Q
Explain the Large Intestine (Colon)
A
- At the end of the small intestine (distal ileum), the remaining contents arrive at another sphincter (Ileocecal sphincter) located at the beginning (Cecum) of the large intestine in the lower right side of the abdomen
- Upon entering the colon contents pass another opening (should they enter they would end up in the appendix)
- As intestinal contents pass through the large intestine the colon withdraws water, leaving semi-solid waste
- The muscles of the rectum and anal canal hold back this waste until deification
- The rectal muscles relax and the 2 sphincter of the anus open
14
Q
Explain the flow of the Large intestine
A
Entrance to lower right side of abdomen Up right side of abdomen Across the front to the left side Down the left side Under the other intestines To the back
15
Q
Define Peristalsis
A
The entire inside wall of the GI tract is ringed with circular muscles. Surrounding these rings are longitudinal muscles. When the rings tighten the long muscles relax–the tube is constricted–when the rings relax the long muscles contract–the tube bulges. This occurs continuously and propels the intestinal contents along. The waves of contraction ripple along the GI tract
- 3/min in stomach
- 10/min when chyme reaches Small Intestine
- After a meal: slow and continuous
- GI tract empty: quiet except for periodic bursts
- *Small intestine is 2.5 times shorter alive than at death because of muscle relaxation**
16
Q
Explain the stomach Action
A
- thickest and strongest walls of the GI tract
- 3 layers of muscles (Longitudinal, circular, diagonal)
- Chyme is completed liquified with gastric juices
- Pyloric sphincter opens briefly, about 3 times/minute to allow small portions of chyme to pass through
17
Q
Define Segmentation
A
The circular muscles of the intestines rhythmically contract and squeeze their contents. These contractions, called segmentation, further break apart food particles in producing chyme and promoting close contact with the digestive juice and the absorbing cells of the intestinal walls.
18
Q
Explain the importance of sphincter contractions
A
- Movement of GI tract at a controlled pace
- Act as safety device
19
Q
List in order the parts of the GI tract
A
- Lumen
- Mouth
- Pharynx
- Epiglottis
- Esophagus
- Esophageal sphincter
- Stomach
- Pyloric sphincter
- Small intestine
- Gallbladder
- Pancreas
- Duodenum
- Jejunum
- Ileum
- Ileocecal sphincter
- Large intestine
- Ascending colon
- Transverse colon
- Descending colon
- Sigmoid colon
- Appendix
- Rectum
- Anus
20
Q
Review picture that shows Digestive tract
A
Computer
21
Q
Define Lumen
A
The space within a vessel, such as the intestine
22
Q
Define Mouth
A
The oral cavity containing the tongue and teeth
23
Q
Define Pharynx
A
The passageway leading from the nose and mouth to the larynx and esophagus, respectively
24
Q
Define Epiglottis
A
Cartilage in the throat that guards the entrance to the trachea and prevents fluid or food from entering it when swallowing
25
Define Esophagus
The food pipe; the muscular conduit from the mouth to the stomach
26
Define Sphincter
A circular muscle surrounding, and able to close, a body opening. Sphincters are found at specific points along the GI tract and regulate the flow of food particles
27
Define Esophageal Sphincter
A sphincter muscle at the upper and lower end of the esophagus. The lower esophageal sphincter is also called the cardiac sphincter because of its proximity to the heart
28
Define Stomach
A muscular, elastic, saclike portion of the digestive tract that grinds and churns swallowed food, mixing it with acid and enzymes to form chyme
29
Define Pyloric Sphincter
The circular muscle that separates the stomach from the small intestine and regulates the flow of partially digested food into the small intestine; also called Pyloric or pyloric valve
30
Define Small Intestine
3-metre length of small-diameter intestine that extends from the pyloric sphincter to the Ileocecal sphincter and is the major site of digestion of food and absorption of nutrients. It's segments are the duodenum, jejunum, and ileum
31
Define Gallbladder
The organ that stores and concentrates bile. When it receives the signal that fat is present in the duodenum, the gallbladder contracts and squirts bile through the bile duct into the duodenum
32
Define Pancreas
A gland that secretes digestive enzymes and juices into the duodenum. Also secretes hormones into the blood that help maintain glucose homeostasis.
33
Define Duodenum
The top portion of the small intestine (about 12-fingers breadth long)
34
Define Jejunum
The first 2/5 of the small intestine beyond the duodenum
35
Define Ileum
The last segment of the small intestine, accounting for about 1/2 the length of the small intestine
36
Define Ileocecal Sphincter
The sphincter separating the small and large intestines
37
Define Large Intestine (Colon)
About 1.5 meters of large-diameter intestine; the lower portion of the intestine that completes the digestive process. It's segments are the ascending colon, transverse colon, the defending colon, and the sigmoid colon.
38
Define Appendix
A narrow blind sac extending from the beginning of the colon that contains lymph cells
39
Define Rectum
The muscular terminal part of the intestine, extending from the sigmoid colon to the anus
40
Define Anus
The terminal outlet of the GI tract
41
Define Monosaccharide
A single-sugar molecule (glucose, fructose)
42
Define Disaccharide
A pair of monosaccharides linked together (maltose)
43
Define Polysaccharide
Numerous (up to thousands) monosaccharides linked together (starch)
44
Define Disaccharidase
Enzyme involved in hydrolysis (breaking down) a specific disaccharide into its monosaccharide components
45
Define Amino Acid
The building blocks of protein
46
Define Dipeptide
2 amino acids bonded together
47
Define Tripeptide
3 amino acids bonded together
48
Define Polypeptide
Many (10 or more) amino acids bonded together; polypeptides form proteins
49
Define Fatty Acid
The building blocks of fats
50
Define Glycerol
The "backbone" to which fatty acids are attached to produce a triglyceride
51
Define Monoglyceride
A molecule of glycerol with one fatty acid attached
52
Define Diglyceride
A molecule of glycerol and 2 fatty acids attached
53
Define Triglyceride
A molecule of glycerol with 3 fatty acids attached; the most predominant form of fat in the diet and in the body
54
Define Emulsified Fat
Fat droplets dispersed and stabilized in a watery solution with the help of emulsifiers (bile)
55
Define Carbohydrase
An enzyme that hydrolysis carbohydrates
56
Define Lipase
An enzyme that hydrolysis lipids
57
Define Protease
An enzyme that hydrolysis proteins
58
Define Digestive Enzymes
Proteins found in digestive juices that act on food substances, causing them to breakdown into simpler compounds
59
Define Hydrolysis
A chemical reaction in which one molecule is split into two with a hydrogen atom (H) added to one and a hydroxyl group (OH) to the other (from H2O)
60
Define enzyme
A protein that facilitates a chemical reaction. As a catalyst it remains unchanged
61
Define Gland
Cells or groups of cells that secrete materials for special use
Exocrine (secreting materials out--into digestive tract/onto skin)
Endocrine (secreting materials in--into the blood)
62
Define Salivary glands
Exocrine glands that secrete saliva into the mouth
63
Define Saliva
Principal enzyme begins carbohydrate digestion
Includes water, salts, mucus, enzymes
Protects teeth, mouth, esophagus, stomach from damage
64
Define Gastric glands
Exocrine glands in the stomach wall that secrete gastric juice
65
Define Gastric Juice
Primarily protein digestion
Includes water, enzymes and hydrochloric acid
Strong acidity of stomach prevents bacterial growth and kills bacteria that enter the body with food. To protect themselves the cells of the stomach wall secrete mucus.
66
Define Hydrochloric Acid
An acid comprised of hydrogen and chloride atoms (HCl) that is normally produced by the gastric glands
67
Define Mucus
A slippery substance secreted by the cells of the GI lining that protects cells from exposure to gastric juices. The lining of the GI tract with its coat of mucus is a mucous membrane.
68
Define Liver
The organ that produces bile
69
Define Bile
An emulsifier that prepares fats and oils for digestion; an exocrine secretion made by the liver, stored in the gallbladder, and released into the small intestine (duodenum) when needed.
Not an enzyme!
70
Define Emulsifier
A substance with both water-soluble and fat-soluble portions that promotes the mixing of oils and fats in a watery solution
71
Define Pancreatic Juices
The exocrine secretion of the pancreas that contains both enzymes for digestion of carbohydrate, proteins, fat and bicarbonate a neutralizing agent. The juice flows from the pancreas to the small intestine through the pancreatic duct. (Pancreas also has an endocrine function: secretion of insulin and other hormones)
72
Define Bicarbonate
An alkaline compound with the formula HCO3- that is secreted from the pancreas as part of pancreatic juice. (Also produced in cell fluids from the dissociation of carbonic acid to help maintain the body's acid-base balance). Bicarbonate neutralizes the stomach acid so the chyme is neutral or slightly alkaline. The enzymes of the intestine and the pancreas work best in this environment
73
Explain the Final Stages of digestion
The 3 energy-yielding nutrients are digested and ready to be absorbed. Some vitamins and minerals are altered slightly but most are absorbed as they are. Undigested residues such as fibre continue through the digestive tract carrying some minerals, bile acids, additives and contaminants out of the body. Also remains water accounting for the consistency of stools. By the time the contents of the GI tract reach the end of the small intestine only water, dissolved slats, body secretions and undigested materials remain and enter the large intestine. In the colon, intestinal bacteria ferment some fibres, producing water, gas and small fragments of fat that provide energy for the cells of the colon. The colon itself retrieves all materials that the body can recycle (water and dissolved salts)
74
From the Salivary glands what is the digestive secretion and its major action?
Organ/gland: Salivary glands
Target organ: Mouth
Secretion: Saliva
Action: Fluid eases swallowing; Salivary enzymes breaks down some carbohydrate
Class of Enzyme: Amylase
Digestive Action: Starch --> smaller polysaccharides and maltose
75
From the gastric glands explain the digestive secretions and their major actions
Organ/gland: Gastric glands
Target organ: Stomach
Secretion: Gastric Juice
Action: Fluid mixes with bolus; hydrochloric acid uncoils (denatures) proteins; enzymes digest proteins; mucus protects stomach cells
Class of Enzyme: Protease (Pepsin) Protein --> smaller polypeptides
Lipase (Triglycerides --> diglycerides and fatty acids)
76
From the Pancreas explain the digestive secretions and their major actions
Organ/gland: Pancreas
Target organ: Small intestine
Secretion: Pancreatic Juice
Action: Bicarbonate neutralizes acidic gastric juices; pancreatic enzymes digest carbohydrates, fats and proteins
Class of Enzyme:
1. Amylase (starch/polysaccharides --> maltose)
2. Protease (trypsin) (Polypeptides --> dipeptides, tripeptides and free amino acids
3. Lipase (Emulsified fat --> monoglycerides, glycerol and free fatty acids
4. Disaccharidase (Disaccharides --> monosaccharides)
77
From the liver explain the digestive secretions and their major actions
Organ/gland: Liver
Target organ: Gallbladder
Secretion: Bile
Action: Bile is stored until needed
78
From the gallbladder explain the digestive secretions and their major actions
Organ/gland: Gallbladder
Target organ: Small Intestine
Secretion: Bile
Action: Bile emulsifies fat so that enzymes can have access to digest it
79
From the Intestinal crypts explain the digestive secretions and their major actions
Organ/gland: Intestinal crypts (glands)
Target organ: Small Intestine
Secretion: Intestinal Juice
Action: Intestinal enzymes digest carbohydrate, fat and protein fragments; mucus protects the Intestinal wall
80
Explain the action of Hydrochloric Acid
Produced in the stomach
Creates acidic conditions needed by enzyme pepsin
Strong acid kills most bacteria
To protect stomach from auto-digestion by gastric juice mucus is secreted to coat the wall and lubricate the food
81
Define Absorption
The passage of simple nutrients, produced by digestion, through epithelial cells of the small intestine into the bloodstream or lymphatic system.
Carbohydrates, fats and proteins are broken down into the basic unit to be absorbed
Vitamins, minerals, water and alcohol are absorbed without being changed
82
Where does absorption occur?
Mainly the absorptive surface of the small intestine.
Structural features of the mucosa (inner lining of intestine) made up of numerous villi and microvilli that can recognize, select, and regulate the absorption of the nutrients your body needs.
83
Define Villi
Fingerlike projections from the folds of the inner surface of the small intestine. Composed of hundred of intestinal (absorptive) cells.
In constant motion (lined with thin sheet of muscle)
84
Explain Crypt glands
In the crevices between the villi
| Tubular glands that secrete intestinal juices
85
What do goblet cells do?
Secrete mucus
86
Define microvilli
Microscopic hairs covering the intestinal cells of the villi.
Inside the microvilli (and the membrane) lie hundreds of different kinds of enzymes and "pumps" which recognize and act on different nutrients. Equipped to handle all kinds and combinations of food
87
How does the absorption of nutrients into intestinal cells occur?
1. Simple diffusion
2. Facilitated Diffusion
3. Active Transport
4. Endocytosis (sometimes)
88
Explain Simple Diffusion
Some nutrients (water and small lipids) sew absorbed by crossing the intestinal cells freely
89
Explain Facilitated Diffusion
Some nutrients (water-soluble vitamins) are absorbed by using a specific carrier to transport them from one side to the other or the carrier changes the cell membrane so the nutrients can pass through
90
Explain Active Transport
Some nutrients (glucose and amino acids) must be absorbed actively. They move against the concentration gradient and so require energy
91
Explain Endocytosis
Cell membrane engulfs the molecule, forming a sac that separates from the membrane and moves into the cell
92
Importance of Specialized cells in the GI tract
Successive portions of the intestinal tract are specialized to absorb different nutrients. Nutrients ready for absorption are absorbed at the top, those that take longer are absorbed further down. If an absorptive function becomes dysfunctional the diet can be adjusted accordingly
93
The myth of food combining is false (Eating certain foods together is more than the digestive system can handle)
Combining foods can enhance each other;s use by the body. Example: Vitamin C in citrus fruit can enhance the absorption of iron from a meal of beans or rice etc. Mutually beneficial
94
Preparing Nutrients for Transport
Once a nutrients has passed the absorptive cell it enters the bloodstream or lymphatic system.
Veins, arteries and lymphatic vessels are provided to the villi
95
Entering the bloodstream
Water-soluble nutrients including smaller products of fat digestion are released directly into the bloodstream and guided to the lover where their fate/destination are determined
96
Entering the lymphatic system
The larger fats and fat-soluble vitamins (insoluble in water--blood is mostly water) are assembled by the intestinal cells into larger molecules. Larger molecules cluster together with special proteins forming chylomicrons.
Chylomicrons cannot pass into the blood capillaries and so are released into the lymphatic system
Move through the lymph, bypassing the liver, and entering the bloodstream at a point near the heart
97
Water soluble nutrients such as monosaccharides, amino acids, short and medium-chain fatty acids (14 or fewer carbons), water-soluble vitamins and minerals are transported where and how?
Released directly into the blood stream via the capillaries and then transported by the PORTAL VIEN to the liver
98
Fatty acids with long hydrocarbon chains (16 or more carbons), and fat-soluble vitamins are transported where and how?
They cluster together in the intestinal cells to form large fat molecules to which special protein carriers are attached forming a lipoprotein complex called a CHYLOMICRON. CHYLOMICRON are then taken up by the lymphatic system and transported through the lymph spaces to the thoracic duct (terminates in a vein that leads to the heart) then enter the bloodstream
99
Define the Hepatic Portal Vein
Blood leaving the digestive system goes through the hepatic portal vein to the liver. It branches into a network of large capillaries so every liver cell has access to blood
100
Define Hepatic Vein
Blood leaving the liver collects in the hepatic vein, which returns blood to the heart
101
What is the route of blood through the digestive system?
Heart --> arteries --> capillaries (in intestines) --> hepatic portal vein --> capillaries (in liver) --> hepatic vein --> heart
102
What does the Lymphatic system do?
Provides a one-way route for fluid from the tissue spaces to enter the blood. Lymphatic system has no pump; instead lymph circulates between the cells and collects into tiny vessels. Fluid moves as muscles contract and create pressure. Allows nutrients to bypass the liver
103
Where does the lymph collect mainly?
The thoracic duct opens into the left subclavian vein where lymph enters the bloodstream
104
What are Lacteals?
The lymphatic vessels of the intestine that take up nutrients and pass them to the lymph circulation
105
Explain Choking
Food slips into the trachea and completely blocks air passageways. Especially a risk with small children
106
Explain Flatulence
Flatulence is gas. Foods rich in carbohydrates generally cause it. Normal occurrence for people (99 percent of gases expelled are odourless--nitrogen, oxygen, hydrogen, methane, carbon dioxide). May need medical treatment for painful bloating caused by disease
107
Explain Gastroesophageal Reflux
Heartburn. Gastric juices enter the esophagus through the lower esophageal sphincter. To prevent, eat less at a sitting, chew thoroughly, eat slowly--causes indigestion and upsets the normal peristalsis. Take antacids and acid controllers occasionally (could mask or cause problems). Repeated exposure of esophagus to acid could cause condition known as Barrett's esophagus--increase the risk of cancer in throat and esophagus.
108
Explain Ulcers
Ulcers are lesions (sores) and peptic ulcers are lesions in the lining of the stomach (gastric ulcer) or duodenum (duodenal ulcers). Lining is left unprotected from gastric juices--painful and can cause internal bleeding. If GI bleeding is excessive, iron deficiency could result. Caused by:
1. Infection with H. pylori bacteria--antibiotics
2. Use of anti-inflammatory drugs (aspirin, ibuprofen etc.)--discontinue use
3. Disorders that cause excessive gastric acid secretion--medical professional
Avoid food that causes indigestion/pain, avoid coffee and caffeine and alcohol
109
Explain Vomitting
Muscular contractions extend beyond stomach and carry contents of duodenum and its green bile into the stomach then up the esophagus. Not normally cause for alarm, rest and drink small amounts of liquid. If persists seek medical attention. Self-induced vomiting (Bulimia Nervosa) can cause erosion/infection of teeth, gums, pharynx, esophagus, salivary glands. Eyes become red from pressure of vomiting. Esophagus and stomach can rip and tear
110
Explain Diarrhea
Frequent, loose, watery stool. Contents have moved through intestines too quickly for fluid absorption. Compared to vomiting that looses acidic fluids, diarrhea looses neutral fluids (important for replacement). Could be caused by food, medication, disorders of the GI tract (IBS, Celiac disease, Crohn's disease etc.)
