1
Q
mechanical digestion
A
- phy sical breakdown of food
1. Begins in the mouth w chewing (mastication)
2. Swallowing has three phases - voluntary buccal phase
- involuntary pharyngeal phase
- involuntary esophageal phase
2
Q
muscular externa
A
- muscle layer of the digestive tract that’s responsible for moving food along and mixing it during digestion.
- 2 muscle layer
1. circular - squeezes the tube (like wringing it), narrowing the passageway.
2. longitudinal - shortens the tube, pushing food forward.
3
Q
peristalsis
A
involuntary wave like muscle contractions that move through the digestive tract in one direction
4
Q
segmentation
A
involuntary back and fourth contractions in the intestines that mix food (chyme)
5
Q
ingestion
A
- food is moistened by saliva as soon as it enters the mouth
- saliva is produced by
1. parotid glands
2. submandibular glands
3. sublingual glands
6
Q
what do salivary glands contain
A
- salivary amylase - digestion of starches
- lingual lipase - digestion of fats
- lysozyme - kills bacteria
- mucin - lubricates food
- bicarbonate ions - maintains proper ph for enzymes
- immunoglobin a - provides immune protection
7
Q
esophagus
A
25 cm tube connecting pharynx to stomach
8
Q
esophagus function
A
- transports food (does not digest it)
- secretes mucus to lubricate passage
9
Q
4 layers of the esophagus
A
- mucosa (actually touches the food, makes mucus)
- submucosa
- muscularis externa (pushes the food down, muscular)
- adventitia (outer covering)
10
Q
esophagus muscle types
A
- upper third (top part) - made of skeletal muscle, you control it
- middle part - mix of skeletal and smooth muscle, partly under ur control
- lower third (bottom part) - smooth muscle only, completely involuntary
- so basically you start swallowing voluntarily at the top and the rest of the esophagus takes over and pushes the food
11
Q
sphincters control flow
A
- upper esophageal sphincter - opens to let food in
- lower esophageal sphincter - prevents acid reflux
12
Q
stomach
A
- storage and churning of food
- mixes food w gastric juices to form chyme
- 3 layers of muscle for mixing
1. circular
2. longitudinal
3. oblique (extra layer)
13
Q
pyloric sphincter
A
regulates chyme entering the small intestine
14
Q
production of digestive enzymes
A
- the stomach lining (mucosa) has gastric glands that open into gastric pits
- four main types of cells
1. mucous cells - secret mucus to protect stomach lining
2. parietal cells - secret hydrochloric acid
3. chief cells - secrete pepsinogen (converted to pepsin to digest proteins)
4. endocrine (G cells) - release hormones like gastrin into the blood to stimulate digestion
15
Q
parietal cells
A
- release intrinsic factor needed to absorb vitamin B12 in the small intestine
- release hydrochloric acid making stomach pH very acidic
- acid helps activate digestive enzymes
16
Q
chief cells
A
- release pepsinogen (inactive)
- acid HCl turns pepsinogen to pepsin which breaks proteins into smaller peptides
- also release gastric lipase which helps digest fats (but most fat digestion happens in the small intestine)
17
Q
mucous cells
A
- secrete mucus with bicarbonate
- protects the stomach from its own acids and enzymes
18
Q
g cells
A
- produce gastrin, a hormone that stimulates acid secretion
19
Q
gastroesophageal sphincter
A
- where food enters
- prevents reflux of acid back into the esophagus
20
Q
four main regions of the stomach
A
- cardiac region
- where food enters - fundus
- dome shaped top part of the stomach - body
- main central section - pylorus
- funnel shaped bottom section that narrows into the pyloric canal
21
Q
pyloric region
A
- controls release of chyme (partially digested food) into the small intestine
- pyloric sphincter acts as a valve
22
Q
rugae
A
folds in the stomach lining that allow the stomach to stretch when full
23
Q
liver
A
- produces bile
- detoxification
- nutrient metabolism
- synthesis of important molecules (cholesterol, plasma proteins, etc)
24
Q
bile
A
yellow green fluid made of
- bile salts (important for digestion)
- bilirubin (pigment from breaking down hemoglobin)
- cholesterol
- electrolytes
25
bile salts
- emulsify fats
- allows lipase enzyme to work on fats
- help absorb fat soluble vitamins
26
bile storage and release
- stored in the gallbladder
- when food enters the small intestine
1. CCk hormone released
2. CCK makes gallbladder contract
3. Bile is squeezed through cystic duct - common bile duct - duodenum
4. joins pancreatic duct at the hepatopancreatic ampulla
27
liver helps regulate blood glucose
If sugar is too high
- liver stores glucose as glycogen. process called glycogenesis
If blood sugar is too low
- liver breaks down glycogen into glucose. process called glycogenolysis
If starving/fasting
- liver makes glucose from protein and fats. process called gluconeogenesis
28
liver helps in detoxification
- converts amonia (toxic waste from amino acids) into urea, sent to kidneys
- inactivates hormones circulating in the blood
- breaks down drugs, alcohol, and toxins
29
the pancreas has two functions
1. Endocrine - releases insulin, glucagon, somatostatin in the blood
2. Exocrine - releases digestive enzymes to the small intestine
30
pancreas role in digestion
its major job is to produce digestive enzymes and bicarbonate
31
what happens when food enters the duodenum
- CCK stimulate pancreas got release digestive enzymes
- Secretin stimulates pancreas to release bicarbonate (raises ph so enzymes can work)
32
Pancreatic enzymes
- Released inactive, activate in small intestine
1. pancreatic amylase - stretch digestion
2. Pancreatic lipase - fat digestion
3. Tripsin, chymotripsin, carboxypeptidase A B - protein digestion
4. Nucleases - nucleic acid digestion
33
how do pancreatic enzymes get to small intestine
1. pancreatic juices enter the main pancreatic duct
2. Merge into ampulla of Vater
3. then enter the duodenum
34
small intestine location and function
- long tube from pyloric sphincter to ileocecal valve
- main job is to finish digestion and absorb nutrients
35
two sources of small intestine enzymes
1. pancreatic enzymes
- come from the pancreas
- help digest carbs, fats, proteins
2. brush border enzymes
- located in microvilli
- finish breaking down food into absorbable molecules
36
microvilli and villi
- increase surface area
1. Villi
- finger like projections of mucosa
- contain capillaries that absorb nutrients
2. Microvilli
- tiny folds on the apical surface of enterocytes (main cells that line SI)
- house the hormones that finish digestion
3. Plicae circulares
- deep circular folds in the mucosa + submucosa
- further increase surface area
37
absorption in small intestine
- absorption happens mostly in jejunum and ileum
38
what gets absorbed in small intestine and how
- amino acids + most sugars - via sodium cotransport
- lipids + water - by simple diffusion
- fatty acids, sugars, amino acids - enter capillaries inside villi - travel to the liver
39
chemical digestion small intestine
- most chemical digestion happens in SI
- brush border enzymes + pancreatic enzymes break down fat, carbohydrates, proteins and nucleic acid
40
small intestine anatomic subdivisions
1. Duodenum
2. jejunum
3. Ileum
41
duodenum
- first segment
- receives chyme, bile and pancreatic enzymes
- major site for neutralizing stomach acids
- begins chemical digestion w enzymes
42
jejunum
- middle segment
- main site of nutrient absorption (almost everything except iron + B12)
- has many plicae circulares and villi for absorption
43
ileum
- longest segment (3.5 meters)
- narrowest in diameter
- contains peers patches (immune tissue)
- absorbs vitamin B 12, bile salts, any nutrients not absorbed earlier
- ends at ileoceccal valve which controls entry into the large intestine
44
main job of large intestine
- absorbs water and electrolytes
- by the time food reaches large intestine, 80% of water is already absorbed
- large intestine absorbs most of the remaining water
45
gut bacteria
- large intestine has hundreds of species of bacteria
- they digest materials humans cant break down (like cellulose)
- they produce gases during fermentation (CO2, methane)
- also produce vitamins
- healthy bacteria keep pathogenic bacteria in check
46
large intestine anatomy
- begins at the illeocecal valve and ends at the anus
1. Cecum
- first part of the large intestine
- has appendix attached
2. Colon
- has four parts
3. Rectum
- stores feces before elimination
5. Anus
- last opening of the digestion tract
47
large intestine special features
1. Haustra
- pouch like sacs along the colon formed by smooth muscle contraction
2. Plicae semilunares
- folds between the haustra
3. Goblet cells
- secrete mucus to lubricate stool and protect the colon wall
48
large intestines have no vili
0 because its job is not nutrient absorption just water absorption
49
rectum
- last 12 - 15 cm of the LI
- stores feces
- connects to the anus
50
anal canal sphincters
- internal sphincter (involuntary)
- external sphincter (voluntary)
51
how you get the urge to poop
- when feces build up, rectum wall stretches
- stretch receptors send signals causing
1. rectum muscles to contract
2. internal spnichter to relax
3. external sphincter to tighten
teas science
flashcards
Decks in class (20)
# Cards
-
anatomy 199
-
digestive system51
-
nervous system92
-
muscular system67
-
reproductive system43
-
integumentary system29
-
endocrine system64
-
urinary system50
-
immune system26
-
lymphatic system13
-
skeletal system50
-
biology 164
-
biology 287
-
biology 357
-
biology 458
-
biology 567
-
chemistry 145
-
chemistry 265
-
chemistry 357
-
chemistry 472
