Chapter 2 book notes Flashcards
1
Q
gastrointestinal (GI) tract:
A
-flexible muscular tube extending from the mouth to the anus.
-digestive tract
2
Q
What organs make up the GI tract?
A
-mouth(teeth & tongue)
-pharynx
-epiglottis
-esophagus
-stomach
-small intestine
-large intestine (colon)
-rectum
-anus
3
Q
Mouth (teeth & tongue) function:
A
-chews and mixes food with saliva
4
Q
Pharynx function:
A
-directs food from mouth to esophagus
5
Q
epiglottis function:
A
-protects airway during swallowing
6
Q
esophagus function:
A
-passes food from the mouth to the stomach
7
Q
stomach function:
A
-churns, mixes, and grinds food to liquid mass
-adds acid, enzymes, and fluid
8
Q
small intestine function:
A
-duodenum, jejunum, and ileum
-secretes enzymes that digest all energy- yielding nutrients to smaller nutrient particles
-cells of wall absorb nutrients into blood and lymph.
9
Q
large intestine (colon) function:
A
-absorbs water and minerals
-passes waste (fiber, bacteria, and unabsorbed nutrients) along with water to the rectum
10
Q
rectum function:
A
-stores waste prior to elimination
11
Q
anus function:
A
-holds rectum closes
-opens to allow elimination
12
Q
Accessory organs that aid digestion:
A
-salivary glands
-liver
-gallbladder
-pancreas
13
Q
salivary glands function:
A
-secrete saliva
14
Q
liver function:
A
-manufactures bile salts to help digest fats
15
Q
gallbladder function:
A
-stores bile until needed
16
Q
pancreas function:
A
-manufactures enzymes to digest all energy-yielding nutrients and releases bicarbonate to neutralize acidic chyme that enters small intestine.
17
Q
what are the principle organs of the GI tract?
A
-stomach & intestines
18
Q
Where does the physical process of digestion start?
A
-mouth
19
Q
Saliva helps…
A
-helps dissolve food so that we can taste it.
-only particles in solution can react with taste buds.
20
Q
When food is swallowed it passes through the?
A
-pharynx
-short tube shared by both digestive system and respiratory system
21
Q
Bolus
A
-mouthful of chewed up and swallowed food
22
Q
each bolus slides across your..
A
-epiglottis
-during each swallow the epiglottis closes off trachea, air passageway to lungs, so that we don’t choke
23
Q
Sphincter (“cardiac sphincter”)
A
-muscle at the end of esophagus
-during a swallow, the upper esophageal sphincter opens, bolus slides down the esophagus so that it travels to the stomach.
24
Q
The lower esophageal sphincter closes behind the bolus so that..
A
-it cannot slip back up
25
Bolus in stomach:
-stomach adds gastric juices and transforms it into chyme (semiliquid mass)
26
Stomach then transports chyme to:
-releases chyme into another sphincter (pyloric shincter) which opens into the small intestine and closes after chyme passes through.
27
Chyme in small intestine:
-in beginning of small intestine, chyme passes by opening from common bile duct, which secretes digestive fluids into small intestine from two organs outside GI tract.
28
2 organs outside GI tract that secrete digestive fluids into small intestine:
-gallbladder & pancreas
29
3 segments of small intestine
-duodenum, jejunum, ileum
-total of 10 feet of tubing coiled within abdomen
30
Where is digestion completed?
-small intestine
31
Sphincter between small intestine and large intestine:
-ileocecal valve
32
Where is the large intestine (colon) located?
-lower right hand side of abdomen
33
Upon entering the colon(large intestine) the contents pass another opening:
-the one leading to appendix (blind sac size of finger)
-contents bypass this opening and head to rectum
34
Food travels through digestive tract in this order:
-mouth
-esophagus
-lower esophageal sphincter
-stomach
-pyloric sphincter
-duodenum
-jejunum
-ileum
-ileocecal valve
-large intestine (colon)
-rectum
-anus
35
Gastrointestinal motility:
-spontaneous motion in the digestive tract accomplished by involuntary muscular contractions
36
two types of movements of gastrointestinal motility:
1)peristalsis
2)segmentation
37
The entire GI tract is ringed with…
-circular muscles are inside
-longitudinal muscles are outside.
38
Peristalsis
-begins when bolus enters esophagus
-successive waves of involuntary muscular contractions passing along the walls of the GI tract that push the contents along
39
When tube is constricted:
-circular rings tighten and long muscles relax
40
when tube bulges:
-circular rings relax and long muscles tighten
41
What may interfere with normal GI tract contractions?
-stress
-medicines
-medical conditions
42
Segmentation:
-periodic squeezing of the intestine by its circular muscles that both mixes and slowly pushes contents along
-promotes close contact with mixing digestive juices and absorbing cells intestinal walls
43
The muscles of the GI tract also aide in ..
-liquefying process
44
Liquefying process
-GI tract help liquify bolus to chyme so that the digestive juices will have access to all their nutrients.
-initiated in mouth and finished in stomach
45
Which organ has the thickets walls and the strongest muscles of all the GI tract organs?
-the stomach
46
Third layer of muscles in stomach (in addition to the circular and longitudinal)
-diagonal muscles that alternately contract and relax.
47
All 3 muscles of stomach work together to :
-force chyme downward
48
The pyloric sphincter opens briefly...
-about 3 times a minute, to allow small portions through.
49
To digest food, how many organs secrete digestive juices?
-5
-salivary glands, stomach, small intestine, liver (via gallbladder), and pancreas
50
Digestion of carbs begins in:
-in mouth, where the salivary glands secrete saliva that breaks the bonds in the chains of starch.
51
Salivary glands
-exocrine glands that secrete saliva into the mouth
52
What does saliva consist of?
-water, salts, and enzymes (salivary amylase).
53
Saliva also protects:
-tooth surfaces and linings of mouth, esophagus, and stomach from attack by molecules that might harm them.
54
The enzymes in the mouth do not:-
-affect fats, proteins, vitamins, minerals, and fiber that are food.
55
gastric glands
-exocrine glands in stomach wall that secrete gastric juice into the stomach
56
gastric juice
-contains a mixture of water, hydrochloric acid, and enzymes.
-principle enzymes are pepsin (acts on proteins) and lipase (acts on emulsified fats)
57
Acid in stomach is so strong that
-it can burn the throat if it happens to reflux into the upper esophagus and mouth
-prevents bacterial growth and kills most bacteria that enter the body with food
58
What makes the stomach acid not attack the stomach itself?
-cells of stomach wall secrete mucus, a thick, slimy, white polysaccharide that coats and protects the stomachs lining.
59
Major digestive event in the stomach is:
-initial breakdown of proteins
-acid uncoils protein strands so that stomach enzymes can attack the bonds
60
pepsin
-protein digesting enzyme (gastric protease)
-circulates as precursor, pepsinogen, and is converted to pepsin by action of stomach acid
61
Minor digestive events in stomach
-digestion of some fat by gastric lipase
-digestion of sucrose (small) by stomach acid
-attachment of a protein carrier to VB12.
62
Which enzyme does not work well in the stomach acid?
-salivary amylase,
-it just becomes another protein to be digested
63
By the time the food leaves the stomach the digestion of all
-3 energy yielding nutrients has begun, but process gains momentum in small intestine
64
What digestive juices are secreted in the small intestine?
-pancreatic juice
-bile
-intestinal juice
65
These juices contain digestive:
-enzymes, bile, and biocarbonate
66
pancreatic juice
-exocrine secretion of pancreas, containing enzymes for the digestion of carbs, fat, and protein.
-juice flows from pancreas into small intestine through pancreatic duct.
-also contains sodium bicarbonate which neutralizes acidic chyme
67
bile
-secreted by liver, stored in gallbladder
-bile is an emulsifier, not an enzyme, which prepares fats and oils for digestion
68
All three energy-yielding nutrients are digested in:
-small intestine
69
Rate of digestion of energy nutrients depends on:
-contents of the meal:
EX:if meal is high in simple sugars, digestion is rapid
,if meal is rich in fat, digestion is slower.
70
What nutrients are absorbed as they are?
-vitamins, minerals, and water
71
Where does most absorption take place?
-small intestine absorptive surface area
-provides surface comparable to studio apartment (300ft)
72
villi
-fingerlike projections from the folds of the small intestine
-singular form is villus
73
Villi are in constant:
-motion.
-a thin sheet of muscle lines each villus so that it can wave, squirm, and wiggle like the tentacles of a sea anemone.
74
A single villus, magnified still more, turns out to be composed of:
-several hundreds of cells, each covered with microscopic hairs called microvilli.
75
microvilli
-tine, hairlike projections on each cell of every villus that can trap nutrient particles and transport them into the cells
76
Specialization of the intestinal tract:
-nutrients ready for absorption early are absorbed near the top
-those that take longer to be digested are absorbed farther down
77
What is the most elegantly designed organ systems in the body?
-lowly "gut"
78
The myth of food combining
-idea that people should not eat certain food combinations (meat and fruit) at the same meal because the digestive system cannot handle more than one task at a time
-IT IS A MYTH
79
Once the molecule (nutrient) has entered a cell in a villus, what is the next step?
-transmit it to a destination elsewhere in the body by two transport systems: bloodstream and lymphatic system
80
Both systems supply...
-vessels to each villus.
-through these vessels the nutrients leave the cell and enter either the lymph or the blood (either case, nutrient ends up in blood for a while)
81
Water soluble nutrients and the smaller products of fat digestion are released directly into the...
-bloodstream by way of the capillaries
82
The larger fats and fat soluble vitamins find direct access into..
-capillaries impossible because these nutrients are insoluble in water (blood is mostly water).
-they require some packaging before they are released
83
Intestinal cells assemble products of fat digestion into larger molecules called
-triglycerides
-these triglycerides, fat soluble vitamins, and other large lipids are clustered together with special proteins to from chylomicrons
84
chylomicrons
-lipoprotein that transports lipids from the intestinal cells into the body.
85
Cells release chylomicrons into the..
-lymphatic system.
-they glide through the lymph spaces until they arrive at the point of entry into the bloodstream near the heart
86
What system arranges the deliverance of nutrients wherever they are needed?
-vascular/circulatory system
87
Vascular/circulatory system:
-closed system of vessels through which blood flows continuously in a figure eight, with heart serving as a pump at the crossover point.
-blood goes from heart to arteries to capillaries to veins to heart.
88
How is blood carried to digestive system (and every tissue in body):
-through artery, which branches into capillaries to reach every cell.
89
How does blood leaving digestive system and where does it go?
-goes through hepatic portal vein and conducts it to capillaries of liver
90
The hepatic portal vein branches into
-a network of small blood vessels( sinusoids) so that every cell of the liver has access to the newly absorbed nutrients that the blood is carrying.
91
Blood leaving the liver then again collects into a vein called:
-hepatic vein, which returns blood to the heart.
92
Blood flow from GI tract is:
-heart, to arteries, to capillaries (in intestine), to hepatic portal vein to sinusoids (in liver) to hepatic vein to heart.
93
Liver is located in the circulation system at the point where..
-it will have the first chance at most of the materials absorbed from GI tract
94
Lymphatic system
-one way route for fluids to travel from tissue spaces into the blood
-has no pump, lymph squeeze from one portion to another
95
flow of lymph:
-flows into thoracic duct (large duct behind heart), this duct terminates into the subclavin vein
-which conducts the lymph into the right upper chamber of the heart
96
When physicians measure a person blood lipid profile they are interested in:
-the types of fat present (such as triglycerides and cholesterol)
-the types of lipoproteins that carry them
97
Chylomicrons transport newly absorbed lipids from intestinal cells to:
-the rest of the body
-as chylomicrons circulate through the body, cells remove their lipid contents, so chylomicrons get smaller and smaller
-liver picks up chylomicrons remnants
98
Very-low-density lipoproteins:
-lipoprotein made by liver cells
-transport lipids to various tissues in body
-composed mainly of triglycerides
99
low-density lipoproteins (LDL):
-lipoprotein derived from VLDL as cells remove triglycerides from them
-LDL carry cholesterol and triglycerides from the liver to the cells of the body and are
composed primarily of cholesterol.
100
high-density lipoproteins
(HDL):
-the type of lipoproteins that transport cholesterol back to the liver from peripheral cells
-composed primarily of protein.
-synthesized in liver
101
Density of lipoproteins depends on:
-proportion of lipids and protein they contain
102
more lipids in lipoprotein molecule:
-the lower the density
103
The more protein in a lipoprotein:
-the higher the density
104
Both LDL and HDL:
-carry lipids around in the blood
-BUT LDL are larger, lighter, and filled with more lipid.
-HDl are smaller, denser, and packaged with more protein.
105
High LDL or Low HDL=
-increases risk of heart disease
106
factors that lower LDL con. and raise HDL conc. include:
-weight management
-polyunsaturated or monounsaturated, instead of saturated fatty acids in diet
-soluble fibers
-physical activity
107
Why do older adults experience constipation?
-because intestinal wall loses strength and elasticity with age, which slows GI motility.
108
Two intricate and sensitive systems coordinate all digestive and adsorptive processes of GI tract:
-hormonal (endocrine) system
-nervous system
109
Even before first bite of food is taken,
-the mere thought, sight, or smell of food can trigger a response from these systems.
110
As food travels through GI tract the nervous & hormone system either
-stimulates or inhibits digestive secretions and motility by way of messages.
111
EX: gastrin
-food entering stomach stimulates cells in stomach wall to release hormone gastrin
112
Gastrin: target & response
-Target organ: the glands of the stomach.
-Response: secretion of gastric acid.
113
When appropriate stomach acidity is reached:
-acid itself turns off the gastrin producing cells.
-they stop releasing gastrin, and the glands stop producing hydrochloric acid
114
Most studied GI hormone:
-gastrin, but GI tract releases 50 hormones
115
besides assisting with digestion and absorption, hormones also:
-regulate food intake and influence satiation
116
A healthy GI tract is home to a:
-100 trillion microbes
117
microbes (MY-krobes):
microscopically small organisms
including bacteria, viruses, fungi, and
protozoa; also called microorganisms.
118
The different microbes in various parts of GI tract depends on factors such as:
-pH, peristalsis, diet, and other microbes
119
Relatively few microbes can live in:
-low Ph and rapid peristalsis conditions found in the stomach
120
condition that Microbes permit growth of diverse and abundant population:
-neutral Ph and slower peristalsis of lower small intestine and large intestine
121
Changes in microbiota composition and activity are associated with:
-different diseases such as irritable bowel syndrome and obesity.
122
Most recommended diet strategy to improve health:
-plant based
-promotes most favorable changes in GI microbiota.
123
Diets high in fiber:
-cannot be digested by human body but can provide a major source of energy for bacteria, fostering their growth.
124
As GI bacteria digest and metabolize fibers:
-they produce short fragments of fat, which influence metabolism, inflammation, and disease
-These actions may help to explain how dietary fiber protects against colon cancer
125
prebiotics:
-indigestible substances in foods (such as fibers) that stimulate the growth of beneficial bacteria.
-may reduce risk of GI infections, inflammation, and disorders
126
probiotics:
-live microorganisms found in foods and dietary supplements
-help changes conditions in GI tract that benefit health
-YOGURT
127
Vitamins produced by bacteria in GI tract
-biotin, folate, pantothenic acid, riboflavin, thiamin, B6, B12, and vitamin K
-ESSENTIAL NUTRIENTS
128
Lifestyle factors that affect GI tract health:
-sleep
-physical activity
-state of mind
-nutrition
