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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
oblique layer works during which stage? is it mechanical or chemical?
the churning stage (mechanical)
26
Is digestion mechanical or chemical?
chemical
27
what happens during digestion?
hydrolysis of proteins begins ( pepsin)
28
Which essential activity happens when chyme slowly empties into duodenum?
propulsion
29
How long does it take for chyme to empty into SI?
2 to 6 hours
30
where is gastric juice secreted by?
gastric pit epithelium
31
How does the stomach protects the stomach lining from the pH of 2?
Epithelium produces alkaline mucus
32
how often is the epithelium replaced?
every 3 days
33
name the three type of cells in gastric pits.
1- parietal cells 2- chief cells 3- enteroendocrine cells
34
what does parietal cells secrete?
HCl
35
What does the chief cells secrete and what happens after it is secreted?
Secretes pepsinogen. In the presence of HCl, pepsinogen is activated to pepsin
36
Why is the small intestine over 6 meters long?
to increase surface area to maximize absorption
37
what does the enteroendocrine cells secrete?
secrete hormones: serotonin, histamine, somatostatin, gastrin
38
In duodenum, acidic chyme mixes with secretions from where?
-pancreas (enzymes + alkaline solution) -liver and gallbladder (bile) -intestinal epithelium ( brushborder enzymes)
39
True or False: absorption happens in duodenum
False, digestion.
40
where does the absorption occur?
in jejunum and ileum
41
What is the purpose of circular folds?
To maximize surface area
42
What are the three structural modifications
1- circular folds 2- villi 3- microvilli
43
there is a rich supply of blood and lymphatic vessels in which structural modification?
villi
44
two activities happen in the small intestines?
peristalsis and segmentation
45
What does segmentation do ?
helps to mix food and break it down (mechanical)
46
Which of these digestive activities occur in small intestines? -ingestion - propulsion -mechanical breakdown - digestion -absorption -defecation
propulsion, mechanical breakdown, digestion, absorption
47
What are the functions of liver?
- produces bile - metabolism -detoxification -stores vitamins and minerals -converts glucose into glycogen -regulates amino acid levels - converts ammonia to urea
48
What does the pancreas do?
secretes alkaline solution (which neutralizes the acidity of the chyme) and hydrolytic enzymes (for carbs, fats, proteins, nucleic acids)
49
What are secreted into the duodenum?
alkaline solution and bile
50
bile are amphipathic and acts as a ___ to break fat up into smaller pieces.
detergent/ emulsifier
51
what does the gallbladder do?
stores excess bile
52
is bile mechanical or chemical?
mechanical
53
What does the hepatic portal vein do in the liver?
carries nutrient- rich blood from capillaries of the villi ( all blood from the intestines passes through the liver before going to the heart)
54
what is the function of the large intestine?
reabsorbs water to form solid feces as contents move by peristalsis ( propulsion)
55
where are feces stored and eliminated?
stored in rectum, eliminated via the anus
56
what are feces?
1- undigested food stuff 2- bacteria
57
What causes diarrhea or constipation?
diarrhea: food travels too fast so not enough time for water absorption constipation: food travels too slow so too much water absorption
58
Where does the digestion of carbohydrates start?
in the mouth by salivary amylase.
59
What does the bacteria in the colon produce?
gases and vitamins
60
True or False: we can only absorb disaccharides.
False, we can only absorb monosaccharides
61
in the small intestines, which enzymes break down carbohydrates?
pancreatic amylase and brush border enzymes
62
What is the function of pancreatic amylase in the digestion of carbs?
hydrolyzes to oligosaccharides and disaccharides
63
What is the function of brush border enzymes in the digestion of carbs?
hydrolyzes disaccharides to monomers ( monosaccharides) : glucose, galactose and fructose
64
Where does the digestion of proteins start?
in stomach by pepsin
65
Which pancreatic enzymes are responsible for the digestion of proteins?
trypsin chymotrypsin carboxypeptidase
66
Which brush border enzymes are responsible for the digestion of proteins?
dipeptidase aminopeptidase carboxypeptidase
67
What is the function of pancreatic amylase in the digestion of proteins?
break down polypeptides into smaller ones
68
What is the function of brush border enzymes in the digestion of proteins?
turn smaller polypeptides into amino acids
69
Are enzymes that hydrolyzes proteins produces in an active or inactive form?
inactive
70
Where does the digestion of fats start at?
in small intestines by pancreatic lipases
71
Which enzymes break down fat?
pancreatic lipase and bile
72
what does the pancreatic lipase do to fat?
breaks it down to glycerol, fatty acids, and monoglycerides
73
What does bile do to fat?
emulsifies fat to increase surface area exposed to lipase
74
Where do the nucleic acids start to be digested?
in the small intestines (duodenum)
75
Which enzymes are responsible for the digestion of nucleic acids?
pancreatic nucleases and brush border enzymes
76
what do pancreatic nucleases do to nucleic acids?
they break polynucleotide into sugars, bases and phosphates
77
what do brush border enzymes do to nucleic acids?
same things as pancreatic nucleases
78
Where are carbs and proteins absorbed?
From intestinal lumen, 1st: crosses the intestinal epithelium 2nd: crosses the interstitial fluid 3rd: crosses epithelium of capillaries
79
Where are fats absorbed?
From intestinal lumen, 1st: crosses the intestinal epithelium 2nd: crosses the interstitial fluid 3rd: crosses epithelium of lacteals
80
where does fat go before going into the blood?
in the lymphatic system
81
what is the form of fats after it crosses intestinal epithelium?
chylomicron
82
what are chylomicrons?
triglycerides packaged with phospholipids, cholesterol and proteins
83
What are the hormones that regulate digestion?
1- gastrin 2- secretin 3- cholecystokinin CCK
84
where is gastrin released from? What does it do?
from stomach wall and it stimulates the secretion of gastric juices
85
To keep pH at a homeostatic level, what does the stomach do ( abt gastrin) ?
low stomach pH inhibits/decrease release of gastrin
86
where is secretin secreted from? what does it do?
from duodenum wall, released in response to acidic chyme and stimulates release of bicarbonate from pancreas
87
where is CCK secreted from?
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
Why do we want fat to stay longer in stomach?
give more time for duodenum to work on it and extract as much nutrients as possible
89
what does fatty chime in duodenum do?
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
what is mesentery?
Fold of tissue that attaches organs in the abdominal cavity to the body wall
91
what's another name for mesentery?
mesocolon
92
what type of tissue is in the surface epithelium? | of intestines
simple columnar
93
What type of tissue is in the lamina propria?
areolar/ loose connective tissue
94
what type of tissue is in the serous membrane?
simple squamous
95
bile contains what (2)?
bile salts and pigment
96
how are pigment created?
by the destruction of red blood cells in the liver
97
what is the name of the sphincter that controls movement going from SI to LI?
ileocecal valve

Human Physiology (9 decks)

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