digestion, absorption, and transport Flashcards
1
Q
Digestion
A
Process that breaks down food into individual molecules small enough to be absorbed through the intestinal wall
2
Q
Absorption
A
Process of moving nutrients from GI tract —> circulatory system
3
Q
Elimination
A
Excretion of undigested and unabsorbed food through feces
4
Q
GI Tract
A
Tubular organ system which digests food, absorbs nutrients, and expels waste
20-24 ft long
Provides barrier between food within lumen and our body’s cells
5
Q
6 organs of GI tract
A
Mouth Pharynx Esophagus Stomach Small intesine Large intestine
6
Q
Propulsion
A
Process that moves food along GI tract during digestion
7
Q
Sphincters
A
Muscular rings along GI tract that allow foods to flow into next organ (but not flow back)
8
Q
Chemical digestion
A
Food breakdown through enzymatic reactions
9
Q
Mechanical digestion
A
Food breakdown by chewing, grinding, squeezing, and moving through GI tract
10
Q
Mastication
A
Chewing food
11
Q
Chemical digestion and mechanical digestion both begin in the _____
A
Mouth
12
Q
Digestion in the mouth
A
Mastication cuts/grinds food into small pieces while the tongue mixes it with saliva that dissolves the pieces
Once food is adequatey chewed/moistened, tongue rolls it into bolus and pushes it into pharynx to be swallowed
13
Q
Saliva
A
Secretion from salivary glands that softens and lubricates food and begins chemical breakdown of starch
14
Q
Epiglottis covers ____ in swallowing
A
Trachea
15
Q
Esophagus digestive function
A
Transports foods/fluids from mouthto stomach
16
Q
Upper esophageal sphincter
A
Moves bolus from pharynx to esophagus
17
Q
Lower esophageal sphincter
A
Moves bolus from esophagus to stomach
18
Q
Stomach digestion
A
Stomach stores, mixes, and prepares foods for digestion
Mixes food with gastric juices to chemically break it down
Muscles of stomach push/churn/mix contents of stomach with gastric juices
19
Q
How many layers of stomach lining are there
A
4
20
Q
Innermost layer of stomach lining contains
A
Goblet cells and gastric pits, which secrete digestive juices
21
Q
Parietal cells, chief cells, and mucus neck cells are located in the _____; they secrete ______
A
Stomach lining; gastric juices and mucus
22
Q
Chyme
A
Semiliquid, partially digested food mass that leaves stomach and enters small intestine at pyloric sphincter
23
Q
When does food mixture become chyme
A
Once it reaches lower part of stomach
24
Q
Most digestion occurs in the _______
A
Small intestine
25
3 segments of small intestine (and length)
Duodenum (10in), jejunum (8ft), ileum (12ft)
26
Sphincter that enters small intestine; sphincter that exits small intestine
Pyloric sphincter; ileocecal valve
27
Mechanical digestion in SI
Muscle contractions
28
Chemical digestion in SI
Digestibe secretions from pancreas, gallbladder, and intestinal lining chemically break down nutrients
29
Villi
Small projections that line intestinal walls
Increase surface area, maximize absorption, and help mix everything
Each villi contains capillaries and lymphatic vessles (lacteals) that pick up digested nutrients in absorption
30
How are villi arranged
In circular folds to push chyme forward
31
Enterocytes
Epithelial cells that cover villi; contain microvilli
| Secrete enzymes
32
Enterocytes/microvilli function
Microvilli trap nutriente and absorb them
| Nutrients then enter blood or lymphatic vessels
33
What do goblet cells secrete
Lubricating mucus into intestine
34
What do crypts between villi secrete?
Intestinal juices
35
What happens to villi if not given propr nutrition
They deteriorate and flatten, leading to malabsorption
36
How lomg does food stay in small intestine
3-10 hours
37
What doew the large intestine absorb
Water and some nutrients
38
3 segments of large intestine
Cecum
Colon
Rectum
39
Largest portion of large intestine
Colon
40
4 segments of colon
Ascending
Transverse
Descending
Sigmoid
41
Which intestine absorbs more nutrients? Which absorbs nutrients more efficiently?
Small; large
42
GI flora
Helpful bacteria that follnize the colon
Produce vitamins
Ferment some undigested and unabsorbed dietary carbs
43
Probiotics
Live microorganisms that, when consumed in adequate amounts, confer a health benefit on host
Help restore GI flora # if altered by stressors
44
Prebiotics
Nondigestible starch found in plant foods that promotes the growth and health of GI flora
45
Synbiotics
Processed foods and supplements that contain probiotics and prebiotics
46
Where to find probiotics
Fermented dairy and soy products
| Dietary supplements
47
What is stool made of
Undigested food residue, dead cells of GI tract, and bacteria
48
What causes darker stool color
Increased Iron concentration
49
Accessory organs of digestion
Salivary glands, liver, gallbladder, pancreas
They secrete digestive juices, but food does not pass thru them
Help with breakdown and transport of nutrients
50
Components of saliva
Water
Electrolytes
Enzymes (incl salivary amylase and lysozyme)
Mucus
51
Liver digestion role
```
Essential role in carb metabolism
produces proteins
manufactures bile salts
metabolizes alcohol
Degrades toxins and excess hormones
```
52
Bile is produced by ____; stored in ______
Liver; gallbladder
53
Gallbladder role in digestion
Receives bile through hepatic duct (from liver), concentrates it, secretes it into small intestine through common bile duct
54
Duct that sends bile into gallbladder; Duct that sends bile out of gallbladder
Hepatic duct; common bile duct
55
Endocrine function of pancreas
Releases hormones that regulate blood glucose levels into bloodstream
56
Exocrine function of pancreas
Produces and secretes digestive enzymes through pancreatic duct into small intestine
57
Peristalsis
Forward, rhythmic muscular contractions that move food through the GI tract
Beguns in esophagus
Slower in stomach
58
Why is peristalsis slower in stomach
Peristalsis is mixing and churning the stomach contents with gastric juices until it is liquified
59
Segmentation
Muscular contractions of small intestine that move food back and forth, breaking the mixture into smaller pieces and combining it wjth digestive juices
60
Second form of mechanical digestion
Segmentation
61
When food is shifted, rather than squeezed, what is this called
Segmentation
62
Mass movement peristalsis
Strong, slow peristaltic movements occuring only 3-4 times per day within colon
Forces waste toward colon
63
What makes mass movement peristalsis stronger
High fiber diet
64
Enzymes
Substances, mostly proteins, that increase rate of chemical reactions
They accelerate hydrolysis
Unchanged in reactions
65
Hydrolysis
Chemical reaction that breaks bond between 2 molecules with H2O
66
3 conditions for enzymes to catalyze hydrolysis
1. Compatible enzyme and nutrient must both be present
2. The pH of environment must fall within appropriate range
3. Temperature of the environment must fall within appropriate range
67
T/F each enzyme is only compatible with one specific substrate
True
68
Where are digestive enzymes secreted
All along GI tract
69
Where are most digestive enzymes produced
Pancreas
70
Enzymes with the term amylase are involved in
Carb digestion
71
Enzymes with the term lipase are involved in
Lipid digestion
72
Enzymes that are activated from an inactive “ogen” form are involved in
Protein digestion
73
Enzyme secreted by salivary glands
Salivary amylase
74
Enzymes secreted by stomach
Pepsinogen —> pepsin
| Gastric lipase
75
Enzymes secreted by pancreas
```
Pancreatic amylase
Trypsinogen —> trypsin
Chymotrypsinogen —> chymotrypsin
Procarbixypeptidase —> carboxypeptidase
Pancreatic lipase
```
76
Enzymes secreted by small intestine
```
Sucrase
Maltase
Lactase
Dipeptidase
Tripeptidase
Lipase
```
77
Saliva pathway and action
Secreted by salivary glands into mouth
| Moistens food, eases swallowing; contains salivary amylase
78
HCl pathway and action
Secreted by parietal cells into stomach
| Denatures proteins, activates pepsinogen
79
Intrinsic Factor pathway and action
Secreted by parietal cells into stomach
| Needed for vitamin B12 absorption
80
Mucus pathway and action
Secreted throughout GI tract
| Lubricates and coats internal mucosa to protect it from chemical or mechanical damage
81
Intestinal Juice pathway and action
Secreted by crypts into small intestine
| Contains enzymes that digest macronutrients
82
Bile pathway and action
Secreted by liver into gallbladder for storage, released from gallbladder into small intestine via common bile duct
Emulsifies large globules of lipid into smaller droplets
83
Bicarbonate ions pathway and action
Secreted by pancreas through pancreatic duct into small intestine
Raises pH and neutralize stomach acid
84
When food enters stomach, parietal cells produce:
HCl and intrinsic factor
85
Functions of HCl in digestion
Lower pH of gastric juice, denaturing proteins
| Activate proteins and enhance absorption of certain minerals
86
Chief cells release:
Pepsinogen and gastric lipase
87
Goblet cells in stomach produce:
Mucus
| To protect stomach lining from damage
88
Bile components
Water, bile salts, bile pigments, fat, and cholesterol
89
Why does bile emulsify fats
It increases the surface area of fat globule so it is more accessible by pancreatic lipase
90
Bicarbonate
Negatively charged alkali ion produced from bicarbonate salts and secreted by pancreas
Neutralizes HCl in duodenum during digestion to protect small intestine and facilitate enzyme activity
91
Nutrients that need more time to be disassembled are mainly absorbed in which part of small intestine
Jejunum
92
Intestinal permeability (leaky gut syndrome)
Condition in which junctions between enterocytes allow large molecules to enter bloodstream
Decreases ability of GI tract to regulate absorption of nutrients
93
4 mechanisms of nutrient absorption
Passive diffusion
Facilitated diffusion
Active transport
Endocytosis
94
passive diffusion
movement of substances across cell membrane along their concentration gradient
no carrier no energy
95
facilitated diffusion
movement of substances across cell membrane with help of carrier protein, along their concentration gradient
yes carrier, no energy
96
active transport
movement of substance across cell membrane against their concentration gradient with help of carrier protein and energy expenditure
yes energy, yes carriers
97
endocytosis
type of active transport in which cell membrane forms an indentation, engulfs the substance to be absorbed, and releases it into interior of the cell
when molecules are too big for passive or active transport
allows whole proteins to be absorbed intact
98
what absorption occurs in large intestine
absorbs H2O and certain minerals (mainly Na)
99
how is H2O absorbed in lg intestine
passive diffusion
100
how is Na absorbed in lg intestine
active transport
101
enteric nervous system
section of peripheral nervous system that directly controls GI system
102
enterogastrones
group of GI tract hormones, produced in stomach and intestines, that control gastric motility and secretions
incl gastrin, secretin, CCK, GIP
103
what hormone is released when protein passes through LES
gastrin
104
what hormone is released when acidic passes through pyloric sphincter
secretin
105
what hormone is released when partially digested protein/fat passes through GI tract
CCK
106
what hormone is released when fatty acids/glucose passes through GI tract
GIP
107
ghrelin
hormone produced in stomach that stimulates hunger
| released from gastric cells when stomach is empty; travels to brain
108
peptide YY
hormone produced in small intestine that reduces hunger
| released by cells in ileum/colon; travels to brain
109
how are H2O soluble nutrients absorbed
they are absorbed into enterocytes, cross into capillaries, and travel to liver via hepatic portal vein
liver further breaks them down and repackages before releasing into blood
blood leaves liver toward heart
110
how are fat soluble nutrients absorbed
lacteals in villi of enterocytes collect fat-soluble vitamins, long chain fatty acids, and some large proteins
nutrients are transported from lymph capillaries to lymphatic vessels o thoracic duct to subclavian vein
111
lymphatic system
complex network of capillaries, small vessels, valves, nodes, and ducts that transport fat-soluble nutrients through the body
112
GERD
chronic condition characterized by backward flow of stomach contents into esophagus
results in heartburn
due to weak lower esophageal sphincter
113
in what types of individuals is esophageal cancer typically found
typically found in >50 y/o males in urban areas with history of heavy smoking and alcohol intake
114
gastroenteritis
inflammation of lining of stomach and intestines (stomach flu)
mainly caused by norovirus
115
ulcer
sore/erosion of stomach or intestinal lining
| burning pain is most common symptom
116
bacteria involved in ulcers
helicobacter pylori
117
what can worsen or cause ulcers
NSAIDs
nicotine
excess alcohol and stress
118
gallstones
stones formed from cholesterol in gallbladder or bile duct
119
celiac disease
genetic autoimmune disease in which hyperimmune response damages villi of small intestines when gluten is consumed
120
classic symptoms of celiac disorder
```
abdominal bloating
cramping
diarrhea, gas, smelly stool
weight loss
anemia
fatigue
bone and joint pain
skin rash
```
121
how to diagnose celiac disease
blood test measuring gluten-reactive T cells
| if positive, additionally do tissue biopsy of small intestine
122
non-celiac gluten sensitivity
reaction to eating foods with gluten when celiac disease has been ruled out; symptoms vary
123
irritable bowel syndrome
intestinal disorder resulting in abdominal discomfort, pain, diarrhea, constipation, and bloating
cause unknown
124
inflammatory bowel disease
chronic inflammation throughout the GI tract; results in diarrhea
incl ulcerative colitis and crohns disease
125
ulcerative colitis
chronic inflammation of colon that results in ulcers forming in lining of cololn
126
crohns disease
form of ulcerative colitis in which ulcers form throughout GI tract (not just in colon)
127
what is looked for in colonoscopy?
colon polyps; these can lead to colon cancer
