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Human Physiology > lecture 4: digestive system > Flashcards

lecture 4: digestive system Flashcards

1
Q

name the 2 paths involved in the digestive system (common names)

A

path food takes
accessory organs

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2
Q

name the 6 essential activities of digestion

A

ingestion
propulsion
mechanical breakdown
digestion (chemical, enzymes needed)
absorption
defecation

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3
Q

name the 2 groups of organs of digestive system

A

alimentary canal organs
accessory glands

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4
Q

describe alimentary canal organs (digestive track)

A

food passes through
mouth –> pharynx –> esophagus –> stomach –> small intestine –> large intestine –> anus

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5
Q

describe accessory glands

A

secretes digestive juices into the canal to aid digestion
salivary glands, liver, gallbladder, pancreas

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6
Q

what type of epithelium is mouth pharynx and esophagus lines with

A

stratified squamous

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7
Q

why do we choke

A

food gets into airway - talking while eating or chewing too fast

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8
Q

name the important sections of oral cavity

A

soft palate - muscle and connective tissue
hard palate - bone
tongue - skeletal muscles
epiglottis - elastic cartilage

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9
Q

name steps of the mouth digestion

A

entry point of food (ingestion)
food is chewed (mechanical)
saliva is secreted by salivary glands (chemical, mechanical)
tongue

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10
Q

describe food being chewed

A

teeth of varying shapes cut, smash and grind food so its easy to swallow
increases surface area of food - so enzymes can work more efficiently

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11
Q

describe purpose of saliva

A

lubricates foods for swallowing (contains mucin)
neutralizes acid in mouth (since its basic)
antibacterial agents kill bacteria
contains salivary amylase

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12
Q

describe function of tongue

A

tastes food (papillae)
pushes food around while chewing
helps form bolus and push it into pharynx while swallowing

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13
Q

describe pharynx

A

connects mouth and nasal cavity to trachea and esophagus
epiglottis - covers airway when swallowing
oro + laryngo + naso pharynx = call it all the pharynx

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14
Q

what is swallowing and is it voluntary

A

propulsion
starts off as voluntary then becomes involuntary

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15
Q

what happens when bolus enters the pharynx

A

esophageal sphincter relaxes (opens)
larynx moves up and epiglottis moves down to cover glottis (opening to larynx)

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16
Q

how does bolus move through esophagus

A

PERISTALSISSSS

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17
Q

describe esophagus + digestive activities

A

conducts food from pharynx to stomach ~ 25cm long
propulsion via peristalsis

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18
Q

name the 2 sphincter of esophagus

A

esophageal - pharynx/esophagus
gastroesophageal - esophagus/stomach

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19
Q

what is a sphincter

A

circular ring of muscle that acts like a valve (opens and closes)

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20
Q

what is peristalsis

A

alternating contraction and relaxation of smooth muscle lining the digestive track
propels food towards anus (one direction)

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21
Q

is peristalsis voluntary?

A

NOPEee
involuntary

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22
Q

what happens during emesis (vomiting)

A

Involuntary
reverse peristalsis

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23
Q

name parts of walls of digestive track

A

mucosa
submucosa
muscularis externa
serosa (adventitia)

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24
Q

describe mucosa (walls of digestive track)

A

surface epithelium (simple columnar or stratified squamous)
lamina propria (areolar connective tissue)
thin layer of smooth muscle

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25
Q

describe submucosa (walls of digestive track)

A

areolar connective tissue containing glands, nerve endings, blood vessels and lymphatic vessels

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26
Q

describe muscularis externa (walls of digestive track)

A

circular smooth muscle (inner)
longitudinal smooth muscle layer (outer)
PERISTALSIs

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27
Q

describe serosa (walls of digestive track)

A

fibrous connective tissue
serous membrane (simple squamous)

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28
Q

what is strange about muscularis externa of stomach

A

extra internal layer called oblique layer - for churning

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29
Q

describe structure of stomach

A

located in upper abdominal cavity below diaphragm
muscularis externa = longitudinal layer, circular layer and oblique layer

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30
Q

name steps of the stomach digestion

A

stores food
churning (mechanical)
digestion (chemical)
empties chyme into duodenum (small intestine)

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31
Q

describe storing of food (stomach digestion)

A

rugae (accordion folds in mucosa) and very elastic wall allows stretching
accommodates up to 2L

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32
Q

describe churning (stomach digestion)

A

oblique layer of smooth muscle pummels food and mixes with gastric juices –> produces chyme

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33
Q

describe digestion (stomach digestion)

A

hydrolysis of protein begins
enzyme pepsin

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34
Q

describe the emptying of chyme into duodenum (small intestine (stomach digestion)

A

pyloric sphincter separates stomach and duodenum (propulsion)
allows 3mL to enter small intestine at a time ~ 2-6 hrs to empty (slow digestion)

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35
Q

where is gastric juice found

A

stomach
secreted by gastric pit epithelium

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36
Q

what does stomach epithelium produce

A

alkaline mucus to protect the stomach lining

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37
Q

how often is stomach epithelium replaced

A

every 3 days

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38
Q

describe gastric juice

A

acidity kills bacteria, denatures proteins, breaks down cell walls
activates pepsin

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39
Q

name the 3 types of cells in gastric pits

A

parietal
chief
enteroendocrine

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40
Q

why is pepsin secreted in an inactive form (pepsinogen)

A

not to breakdown proteins in chief cells (pepsin is not specific, so it can attack all proteins)
pepsinogen is secreted from chief cells into stomach then HCl mixes with it and produced pepsin (activated enzyme)

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41
Q

describe parietal cells

A

secretes HCl

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42
Q

describe chief cells

A

secretes pepsinogen
in the presence of HCl pepsinogen is activated to pepsin

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43
Q

describe enteroendocrine cells

A

secrete hormones

44
Q

name 4 hormones secreted by enteroendocrine cells

A

serotonin
histamine
somatostatin
gastrin

45
Q

describe hormone serotonin (digestive track)

A

stimulates muscle contractions
excitatory

46
Q

describe hormone histamine (digestive track)

A

stimulates release of HCl (sometimes why stomach hurts during allergic reaction)
excitatory

47
Q

describe hormone somatostatin (digestive track)

A

inhibitory

48
Q

describe gastrin (digestive track)

A

stimulatory, excitatory
ex: HCl secretion

49
Q

name 3 parts of small intestine and functions

A

duodenum - digestion
jejunum - absorption
ileum - absorption

50
Q

describe small intestine

A

3 parts
longest section ~ 6 meters long
length = maximizes surface area for absorption

51
Q

what happens in duodenum

A

acidic chyme mixes with secretions from other organs

52
Q

name and briefly describe 3 organs (secretions) that chyme mixes with in duodenum

A

pancreas - enzymes and alkaline solution
liver and gallbladder - bile
intestinal epithelium- brushborder enzymes

53
Q

what is the purpose of the many structures of the small intestine

A

maximize surface area (250m^2) for absorption

54
Q

name the 3 structural modifications of small intestine

A

circular folds
villi
microvilli

55
Q

describe circular folds of small intestine

A

folding of mucosa and submucosa - like little hills

56
Q

describe villi of small intestine

A

finger like projections of mucosa (on tops of hills)
blood capillaries for absorption
lymphatic vessels

57
Q

describe microvilli of small intestine

A

projections of plasma membrane and epithelial cells
looks like brush

58
Q

does ALL absorption occur in small intestine?

A

NOOO
some in stomach for things like alcohol, aspirin, drugs, water, vitamins (faster absorption)

59
Q

what is segmentation

A

occurs in small intestine
squeezing at top and bottom
helps mix and breakdown food

60
Q

what digestive activities occur in small intestine

A

propulsion (whole digestive system)
mechanical breakdown (segmentation and bile)
digestion (chemical)
absorption

61
Q

which digestive activities do not occur in small intestine

A

ingestion and defecation

62
Q

what does liver do

A

produces bile
metabolism
detoxification

63
Q

what does pancreas do

A

produced hydrolytic enzymes (for carbs, fats, proteins and nucleic acids)
produced alkaline solution, rich in bicarbonate - neutralizes acidic chyme

64
Q

what are bile salts

A

amphipathic and act as detergent or emulsifier to break up fat into small pieces (more access for lipases)

65
Q

what does gallbladder do

A

stores excess bile

66
Q

what two things are secreted into duodenum and from where

A

bile - liver/gallbladder
alkaline solution - pancreas

67
Q

what does bile do

A

makes fat soluble in water (breaks down)
attaches to fat and gives it a hydrophilic side
helps enzymes work

68
Q

is bile mechanically or chemically digesting fats?

A

mechanically
facilitates chemical breakdown BUT it isn’t chemical breakdown - just takes fats that are stuck together and beaks them up

69
Q

what does bile contain

A

bile salts and pigments - byproducts of destruction of red blood cells in liver
dark green or yellowish brown
pigments are eliminated with feces

70
Q

what is the hepatic portal vein

A

carries nutrient rich blood from capillaries of villi (all blood from intestines passes by liver before going to heart)

71
Q

why does blood have to pass by the liver before going to the heart

A

stores vitamins and minerals
detoxifies
converts glucose into glycogen
regulates amino acid levels
converts ammonia to urea

72
Q

describe large intestine

A

connected to small intestine at a T junction (includes cecum and illeocecum)
ileocecal valve (sphincter) controls movement from small to large intestine
shaped like a U 1.5 m long

73
Q

what does large intestine do

A

reabsorbs water to form solid feces
slow peristalsis (propulsion) 7L secreted and almost all reabsorbed

74
Q

what do bacteria in the colon produce

A

gases and some vitamins (vit k, B vits, folic acid)

75
Q

where are feces stored (explain process)

A

rectum until eliminated via anus
internal sphincter - involuntary
external sphincter - voluntary

76
Q

what is feces

A

undigested food stuff (ex cellulose)
bacteria

77
Q

what causes diarrhea or constipation

A

diarrhea - moves fast through large intestine, not enough water reabsorbed
constipation - moves slow through large intestine, too much water reabsorbed
has to do with muscle contractions - frequency affects how long it is in small intestine

78
Q

where does digestion of carbs start and where does it go ? explain areas

A

mouth
continues in small intestine (duodenum)

79
Q

name the enzymes involved in digestion of carbs

A

salivary amylase
pancreatic amylases
brush border enzymes

80
Q

describe pancreatic amylase (digestion of carbs)

A

hydrolyzed to oligosaccharides and disaccharides

81
Q

describe brush border enzymes (digestion of carbs)

A

hydrolyses to monomers
disaccharides
finalizes digestion of carbs

82
Q

describe digestion of proteins (where)

A

starts in stomach
continues into small intestine - duodenum

83
Q

name enzymes used to digest proteins

A

pepsin (stomach)
pancreatic enzymes
brush border enzymes

84
Q

describe pancreatic enzymes (digestion of proteins)

A

polypeptides to small polypeptides
trypsin
chymotrypsin
carboxypeptidase
secreted in inactive forms

85
Q

describe brushborder enzymes (digestion of proteins)

A

small polypeptides to amino acids and some dipeptides/tripeptides
dipeptidase
aminopeptidase
carboxypeptidase

86
Q

where does digestion of fats start

A

small intestine

87
Q

name enzymes that help digestion of fat

A

pancreatic lipases
bile

88
Q

describe pancreatic lipases (digestion of fats)

A

breaks down fat into glycerol, fatty acids and monoglycerides

89
Q

describe bile (digestion of fat)

A

emulsifies fat
increases surface area exposed to lipases

90
Q

where does digestion of nucleic acids start

A

small intestine (duodenum)

91
Q

name enzymes that help digest nucleic aids

A

pancreatic nucleases
brush border enzymes

92
Q

describe pancreatic nucleases and brush border enzymes (digestion of nucleic acids)

A

breaks down polynucleotide into sugars, bases and phosphates

93
Q

describe absorption of carbs and proteins

A

from intestinal lumen –> crosses intestinal epithelium
–> crosses interstitial fluid –> crosses epithelium of capillaries

94
Q

how are carbs and proteins (nutrients) separated from blood

A

2 layers of cells

95
Q

describe absorption of fats (name steps)

A

from intestinal lumen –> crosses intestinal epithelium –> crosses interstitial fluid –> crosses epithelium of lacteals

96
Q

what are lacteals

A

lymphatic capillary

97
Q

describe crossing intestinal epithelium (absorption of fats)

A

inside epithelial cell they (re)form triglycerides –> chylomicrons

98
Q

describe crossing epithelium of lacteals (absorption of fats)

A

lacteals converge into larger vessels of lymphatic system
eventually drain into large veins

99
Q

what are chylomicrons

A

triglycerides packaged with phospholipids (balls on outside - hydrophilic head), cholesterol and proteins
make fat soluble in water - environment of circulatory system

100
Q

name the hormones that regulate digestion

A

gastrin
secretin
cholecystokinin (cck)

101
Q

describe gastrin (regulates digestion, from where and what)

A

from stomach wall
released in response to food
stimulates secretion of gastric juices
low stomach pH inhibits release of gastrin

102
Q

describe secretin (regulates digestion, from where and what)

A

from duodenum wall
releases in response to acidic chyme
stimulates release of bicarbonate from pancreas

103
Q

describe cck (regulates digestion, from where and what)

A

from duodenum wall
released in response to presence of amino acids/fatty acids
stimulates release of bile from gallbladder and release of pancreatic enzymes

104
Q

why does it take longer to digest a fatty meal

A

fatty chyme in duodenum –> stimulates release of secretin and cck in high levels
THIS inhibits peristalsis of stomach and the secretion of gastric juices

105
Q

what is the mesentery

A

mesocolon = mesentery
fold of tissue that attaches organs in abdominal cavity to body wall
blood vessels, nerves, and lymphatic vessels branch through mesentery to supply organs

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