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Human Physiology > Lecture 4: Digestive system > Flashcards

Lecture 4: Digestive system Flashcards

1
Q

What are the six essential activities?

A

1-Ingestion
2-Propulsion
3-Mechanical breakdown
4-Digestion (chemical)
5-Absorption
6-Defecation

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2
Q

Name the two groups of organs in digestive system.

A

1- alimentary canal organ
2-accessory glands

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3
Q

What are the accessory glands?

A

salivary glands, liver, gallbladder, pancreas

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4
Q

is saliva a mechanical or chemical process?

A

both

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5
Q

What does saliva do?

A

Lubricates food, neutralizes acid, antibacterial agents kill bacteria, contain salivary amylase that breaks down food and carbohydrates

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6
Q

Is swallowing voluntarily controlled?

A

both

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7
Q

What occurs when bolus enters the pharynx? (2)

A

1-The esophageal sphincter relaxes (opens)
2-The larynx moves up and epiglottis moves down to cover glottis (opening of larynx)

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8
Q

Which digestive activity occurs in the esophagus?

A

Propulsion

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9
Q

What happens during emesis?

A

Reverse peristalsis + involuntary

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10
Q

How does bolus moves through the esophagus?

A

by peristalsis

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11
Q

What are sphincters?

A

circular ring of muscle that acts like a valve (can open and close)

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12
Q

What are the two types of sphincters called?

A

1- esophageal (from pharynx to esophagus)
2- gastroesophageal (from esophagus to stomach)

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13
Q

True or False :The digestive system starts from mouth to anus.

A

False, food moves through esophagus to anus

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14
Q

is peristalsis voluntary or involuntary?

A

involuntary

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15
Q

Name the four layers that compose the digestive tract

A

1- Muscosa
2- Submucosa
3-Muscularis externa
4- Serosa

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16
Q

Which layer in the digestive tract is responsible for peristalsis?

A

Muscularis externa

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17
Q

What’s the composition of the mucosa layer? (3)

A

1- Epithelium
2- Lamina propria
3- Muscularis mucosae (smooth muscle)

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18
Q

what do mucosa and submucosa have in common?

A

they both are composed of areolar connective tissue

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19
Q

What does the submucosa contain?

A

glands, nerve endings, blood vessels and lymphatic vessels

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20
Q

what types of layers make the muscularis externa?

A

Circular and longitudinal

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21
Q

What’s the composition of the serosa layer?

A

1- fibrous connective tissue
2- serous membrane ( mesothelium/ epithelium)

The mesothelium is a component of the serous membrane

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22
Q

what type of tissue is the serous membrane made of ?

A

simple squamous epithelium

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23
Q

what do you notice about the muscularis externa of stomach? Why is it important?

A

it has a three layers: an extra oblique layer and it is important for the way food is mixed with gastric juices to produce chyme.

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24
Q

What does the rugae of mucosa do?

A

it helps the expansion/ stretching of stomach

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25
Q

oblique layer works during which stage? is it mechanical or chemical?

A

the churning stage (mechanical)

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26
Q

Is digestion mechanical or chemical?

A

chemical

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27
Q

what happens during digestion?

A

hydrolysis of proteins begins ( pepsin)

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28
Q

Which essential activity happens when chyme slowly empties into duodenum?

A

propulsion

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29
Q

How long does it take for chyme to empty into SI?

A

2 to 6 hours

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30
Q

where is gastric juice secreted by?

A

gastric pit epithelium

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31
Q

How does the stomach protects the stomach lining from the pH of 2?

A

Epithelium produces alkaline mucus

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32
Q

how often is the epithelium replaced?

A

every 3 days

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33
Q

name the three type of cells in gastric pits.

A

1- parietal cells
2- chief cells
3- enteroendocrine cells

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34
Q

what does parietal cells secrete?

A

HCl

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35
Q

What does the chief cells secrete and what happens after it is secreted?

A

Secretes pepsinogen. In the presence of HCl, pepsinogen is activated to pepsin

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36
Q

Why is the small intestine over 6 meters long?

A

to increase surface area to maximize absorption

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37
Q

what does the enteroendocrine cells secrete?

A

secrete hormones: serotonin, histamine, somatostatin, gastrin

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38
Q

In duodenum, acidic chyme mixes with secretions from where?

A

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

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39
Q

True or False: absorption happens in duodenum

A

False, digestion.

40
Q

where does the absorption occur?

A

in jejunum and ileum

41
Q

What is the purpose of circular folds?

A

To maximize surface area

42
Q

What are the three structural modifications

A

1- circular folds
2- villi
3- microvilli

43
Q

there is a rich supply of blood and lymphatic vessels in which structural modification?

A

villi

44
Q

two activities happen in the small intestines?

A

peristalsis and segmentation

45
Q

What does segmentation do ?

A

helps to mix food and break it down (mechanical)

46
Q

Which of these digestive activities occur in small intestines?
-ingestion
- propulsion
-mechanical breakdown
- digestion
-absorption
-defecation

A

propulsion, mechanical breakdown, digestion, absorption

47
Q

What are the functions of liver?

A
  • produces bile
  • metabolism
    -detoxification
    -stores vitamins and minerals
    -converts glucose into glycogen
    -regulates amino acid levels
  • converts ammonia to urea
48
Q

What does the pancreas do?

A

secretes alkaline solution (which neutralizes the acidity of the chyme) and hydrolytic enzymes (for carbs, fats, proteins, nucleic acids)

49
Q

What are secreted into the duodenum?

A

alkaline solution and bile

50
Q

bile are amphipathic and acts as a ___ to break fat up into smaller pieces.

A

detergent/ emulsifier

51
Q

what does the gallbladder do?

A

stores excess bile

52
Q

is bile mechanical or chemical?

A

mechanical

53
Q

What does the hepatic portal vein do in the liver?

A

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

54
Q

what is the function of the large intestine?

A

reabsorbs water to form solid feces as contents move by peristalsis ( propulsion)

55
Q

where are feces stored and eliminated?

A

stored in rectum, eliminated via the anus

56
Q

what are feces?

A

1- undigested food stuff
2- bacteria

57
Q

What causes diarrhea or constipation?

A

diarrhea: food travels too fast so not enough time for water absorption
constipation: food travels too slow so too much water absorption

58
Q

Where does the digestion of carbohydrates start?

A

in the mouth by salivary amylase.

59
Q

What does the bacteria in the colon produce?

A

gases and vitamins

60
Q

True or False: we can only absorb disaccharides.

A

False, we can only absorb monosaccharides

61
Q

in the small intestines, which enzymes break down carbohydrates?

A

pancreatic amylase and brush border enzymes

62
Q

What is the function of pancreatic amylase in the digestion of carbs?

A

hydrolyzes to oligosaccharides and disaccharides

63
Q

What is the function of brush border enzymes in the digestion of carbs?

A

hydrolyzes disaccharides to monomers ( monosaccharides) : glucose, galactose and fructose

64
Q

Where does the digestion of proteins start?

A

in stomach by pepsin

65
Q

Which pancreatic enzymes are responsible for the digestion of proteins?

A

trypsin
chymotrypsin
carboxypeptidase

66
Q

Which brush border enzymes are responsible for the digestion of proteins?

A

dipeptidase
aminopeptidase
carboxypeptidase

67
Q

What is the function of pancreatic amylase in the digestion of proteins?

A

break down polypeptides into smaller ones

68
Q

What is the function of brush border enzymes in the digestion of proteins?

A

turn smaller polypeptides into amino acids

69
Q

Are enzymes that hydrolyzes proteins produces in an active or inactive form?

A

inactive

70
Q

Where does the digestion of fats start at?

A

in small intestines by pancreatic lipases

71
Q

Which enzymes break down fat?

A

pancreatic lipase and bile

72
Q

what does the pancreatic lipase do to fat?

A

breaks it down to glycerol, fatty acids, and monoglycerides

73
Q

What does bile do to fat?

A

emulsifies fat to increase surface area exposed to lipase

74
Q

Where do the nucleic acids start to be digested?

A

in the small intestines (duodenum)

75
Q

Which enzymes are responsible for the digestion of nucleic acids?

A

pancreatic nucleases and brush border enzymes

76
Q

what do pancreatic nucleases do to nucleic acids?

A

they break polynucleotide into sugars, bases and phosphates

77
Q

what do brush border enzymes do to nucleic acids?

A

same things as pancreatic nucleases

78
Q

Where are carbs and proteins absorbed?

A

From intestinal lumen,
1st: crosses the intestinal epithelium
2nd: crosses the interstitial fluid
3rd: crosses epithelium of capillaries

79
Q

Where are fats absorbed?

A

From intestinal lumen,
1st: crosses the intestinal epithelium
2nd: crosses the interstitial fluid
3rd: crosses epithelium of lacteals

80
Q

where does fat go before going into the blood?

A

in the lymphatic system

81
Q

what is the form of fats after it crosses intestinal epithelium?

A

chylomicron

82
Q

what are chylomicrons?

A

triglycerides packaged with phospholipids, cholesterol and proteins

83
Q

What are the hormones that regulate digestion?

A

1- gastrin
2- secretin
3- cholecystokinin CCK

84
Q

where is gastrin released from? What does it do?

A

from stomach wall and it stimulates the secretion of gastric juices

85
Q

To keep pH at a homeostatic level, what does the stomach do ( abt gastrin) ?

A

low stomach pH inhibits/decrease release of gastrin

86
Q

where is secretin secreted from? what does it do?

A

from duodenum wall, released in response to acidic chyme and stimulates release of bicarbonate from pancreas

87
Q

where is CCK secreted from?

A

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

88
Q

Why do we want fat to stay longer in stomach?

A

give more time for duodenum to work on it and extract as much nutrients as possible

89
Q

what does fatty chime in duodenum do?

A

stimulates the release of secretin and CCK in high levels
secretin and CCK inhibit (slows down ) peristalsis of the stomach and the secretion of gastric juices

90
Q

what is mesentery?

A

Fold of tissue that attaches organs in the abdominal cavity to the body wall

91
Q

what’s another name for mesentery?

A

mesocolon

92
Q

what type of tissue is in the surface epithelium?

of intestines

A

simple columnar

93
Q

What type of tissue is in the lamina propria?

A

areolar/ loose connective tissue

94
Q

what type of tissue is in the serous membrane?

A

simple squamous

95
Q

bile contains what (2)?

A

bile salts and pigment

96
Q

how are pigment created?

A

by the destruction of red blood cells in the liver

97
Q

what is the name of the sphincter that controls movement going from SI to LI?

A

ileocecal valve

Human Physiology (9 decks)

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