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Physiology > Digestion > Flashcards

Flashcards in Digestion Deck (103):
1

What is the role of the gastrointestinal system

Digestion
Absorption
Secretion
Excretion
Protection from pathogens

2

What pathway does food take through the GI tract

Mouth
Oesophagus
Stomach
Small intestine
Large intestine/colon
Rectum
Anus
Toilet

3

What are the four basic layers of the GI tract

Mucosa
Submucosa
Muscularis externa
Serosa

4

The mucosa is made up of what three layers

Epithelial cells
Lamina propria
Muscularis mucosae

5

The epithelial cells that make up villi are important because

They increase surface area increasing absorption efficiency

6

The lamina propria houses what?
It is also the source of what nervous system

Houses lymph tissue
This is where the enteric nervous system begins

7

What is in the muscularis mucosae and what does it help with? What is it controlled by?

Muscle
Helps with motility of the GI tract
Controlled by ENS

8

What does the muscularis externa contain

Circular and longitudinal muscle

9

Why is the Serosa layer in the GI tract important

It's connective tissue which holds holds the tract together
Secretes lube that allows for movement of the GI tract

10

Is the histology of the GI tract the same the whole way through the system

No. It has the same things just variations of them

11

What are the skeletal muscles in the digestive system controlled by

Controlled by somatic motors from the CNS

12

Does the digestive system rely on the parasympathetic or sympathetic nervous system

Both. Remember they are both alway active, but the parasympathetic system would be more active

13

Where is the enteric system housed

Completely in the walls of the digestive tract

14

What controls the enteric nervous system

It is independent so sometimes called a mini brain

15

The enteric nervous system controls the....which controls secretion and the........ Which is where longitudinal and circular muscles are found

Submucosal plexus
Myenteric plexus

16

What are the two types of contractions occurring in the GI

Tonic and phasic/rhythmic

17

What are tonic contractions. What would they be prominent in

Contractions that are sustained over a long period of time
I.e. Sphincters

18

What are phasic contractions controlled by

Neural activity
Hormones/paracrines

19

Three examples of phasic contractions are

Peristaltic
Segmental
Migrating motor complex

20

What is migrating motor complex phasic contractions used for

When the body is in a fasted state it sweeps any left over bits to the anus

21

What are long reflexes and where are they integrated

A feed forward mechanism preparing the GI for food
Integrated in the CNS

22

Where are short reflexes integrated and what do they do

Integrated by the enteric nervous system
Sense, integrate, and respond to stimuli

23

Long reflexes activate what in the ANS

Parasympathetic and sympathetic system

24

How are paracrines different to hormones

Paracrines secreted by cells act on other cells in a close vicinity
Hormones are secreted in the blood acting on cells far away

25

Cholecystokinin is a hormone secreted by? Targets what?

Secreted by cells in the small intestine and targets the stomach, gallbladder, pancreas

26

Histamine is a paracrines that is secreted by specific cells where. Is it secreted in the lumen?

Secreted by specific cels in the gastric gland into the interstitial fluid

27

The two components of the upper gastrointestinal tract are

Cephalic phase
Gastric phase

28

What triggers the cephalic phase

Sight sound smell of food
Think of when we salivate over food

29

The first step in the digestive process that occurs in the mouth is called

Mastication

30

What does saliva do?
What is it made up of?

Saliva helps soften and lubricate food
It contains lysozymes for destroying bac
Amylase for carb breakdown
Lipase for fat digestion

31

Go through the swallowing reflex

Tongue pushes Bolus against dog palate at back of mouth triggering reflex
Upper oesophageal spincter relaxes and epiglotis closes
Food moves downward aided by gravity and peristalsis

32

What is important about the gastro-oesophageal sphincter? What would a disorder of this sphincter produce

It seperate a the oesophagus from the stomach preventing reflux of gastric juices into it
Heartburn occurs when it is ineffective

33

The three function of the stomach are?

Storage of chyme and controlled release into the duodenum
Protection from bacteria as acidic cond destroys them
Digestion of proteins

34

What is absorbed in the stomach

Not much except a few lipid soluble substances. Primarily alcohol and aspirin

35

The main things involved in protein digestion are

Enzymes
Acid assists

36

What are the three compartments of the stomach

Fundus
Body
Antrum

37

Is food digested chemically or mechanically in the stomach

Both actually

38

What are rolgues in the stomach and what do they do

They are folds in the stomach epithelial layers that increase surface area

39

Factors that increase gastric emptying

Volume of chyme in the stomach

40

Gastric emptying is controlled by?

Peristaltic contractions of smooth muscle

41

Factors that decrease gastric emptying are

Presence of fat, acid, hypertonicity or distension within the duodenum
Increased sympathetic activity (ie running from a bear)

42

Gastric emptying for fluids takes how long

Minutes

43

Gastric emptying for an ordinary meals takes how long

2-3 hours

44

Gastric emptying for a fatty meal takes how long

4-6 hours

45

What are stomach walls made of

Protein

46

What do mucous neck cells do

Secrete mucous and bicarbonate which acts as a physical barrier between gastric acid juices and the stomachs epithelial cells to prevent autodigestion

47

What stimulates mucous cells

Irritation of the mucosa

48

What stimulates chief cells and what do they release

Stimulates by ACh
Releases pepsinogen

49

What activates pepsinogen turning it into pepsin

Acid assists

50

What does pepsin do

Cuts up polypeptides once the protein has been denatured by acid

51

How do acid assists help the digestion process

Provides medium for optimal pepsin activity
Beaks down connective tissue and muscle
Denatures protein
Kills microbes

52

Parietal cells are stimulated by? And release what?

Stimulated by ACh gastric histamine
Secrets gastric acid

53

Enterochromaffin-like cells are stimulated by? And secrete what?

Stimulated by ACh and gastrin
Secrete histamine

54

D cells are stimulated by? And secrete what?

Stimulated by acid in the stomach
Secrete somatostatin

55

What does somatostatin do?

Dilutes the acid in a stomach

56

How do parietal cells secrete acid into the lumen of the stomach

With a hydrogen potassium ATPase pump

57

How is the hydrogen required by the H/K pump gathered

From H2O

58

What causes gastric ulcers and how

The bacteria helicobacter pylori as it disrupts the mucosal layer in the stomach

59

The anatomy of the lower GI tract includes

Small and large intestines
Liver
Pancreas

60

What does feedback reflexes from the small intestine control

Gastric emptying

61

What do feed forward reflexes from the small intestine promote

Digestion
Motility
Utilisation of nutrients

62

What controls the type of feed forward efferent pathway from the small intestine

The type of nutrient being digested

63

What do feed forward reflexes from carbohydrates stimulate and what does it inform the pancreas to secrete

Stimulates GIP and GIP-1 making the pancreas secrete insulin

64

Feed forward reflexes from fats and protein presence releases what? Causing the pancreas to release what to do what?

Releases CCK which tells the pancreas to release pancreatic enzymes which break down the fats and proteins

65

Acid in the small intestine causes a feed forward on what system? What substance is secreted in response and what does it do

Acid in the small intestine interacts with the efferent system which secretes Secretin which acts on the pancreas telling it to release bicarbonate

66

Chyme in the small intestine has a feed forward effect on which system? Why?

The enteric nervous system telling it to reduce gastric emptying

67

Why is intestinal motility important

Mixes the chyme and exposes nutrients to the mucosa for absorption and to propel the food forward down the GI tract

68

What is intestinal motility simulated by? What is it inhibited by?

Stimulated by parasympathetic nervous system
Inhibited by sympathetic nervous system

69

Can microbiota in the GI reflect the diet the person is on

Yes. Cool

70

What is the role of the liver

Makes bile salts
Filters lipid soluble nutrients
Clears drugs from body

71

Where are bile salts stored

The gall bladder

72

What is the hepatic portal system

Blood containing nutrients from the small intestine goes through the hepatic portal system into the liver

73

Does the liver recycle bile salts

Yes. Very efficient at it too

74

What is the role of the pancreas

Secretes hormones in the endocrine system
Secretes enzymes and other solutes required to buffer the acidic conditions in the exocrine system

75

What types of pancreatic substances does the exocrine pancreas secrete

Proteolytic enzymes (inactive enzymes)
Pancreatic amylase (active)
Pancreatic lipase (active)

76

Proteolytic inactive enzymes that digest proteins are

Trypsinogen
Chymotrypsinogen
Procarboxypeptidase

77

What does pancreatic amylase do?

Converts polysaccharides into disaccharides

78

What are pancreatic lipase involved in

Digestion of fat

79

How are inactive proteolytic enzymes activated

Trypsinogen secreted into lumen of SI and is activated by enteropeptidase which turns it into trypsin. Trypsin then activates other enzymes

80

Where are fats taken once they are absorbed

The lymph system

81

Where are enzymes that are secreted by SI cells found

On brush border cells found on villi

82

Carbs are digested by what secreted from where

Digested by amylase
Secreted in salivary glands and pancreas

83

Amylase digests polymers of glucose into disaccharides of

Maltose
Sucrose
Lactose

84

Enzymes on brush border cells digest what into what

Digest disaccharides into monosaccharides

85

Maltose is digested into what monosaccharides

Two glucose units

86

Sucrose is digested into what monosaccharides

One glucose one fructose

87

Lactose is digested into what monosaccharides

One glucose
One galactose

88

Is cellulose digested and absorbed

Nope becomes dietary fibre and is excreted

89

How is glucose and galactose absorbed

Through a sodium cotransporter into the epithelial cells.
Transported to capillary through GLUT-2 transporters

90

How is fructose absorbed

Through GLUT-5 transporters into the epithelial cell
Through GLUT-2 channel into ECF

91

Protein is digested by:

Pepsin in the stomach
Trypsin chymotrypsin carboxypeptidase from the pancreas
Aminopeptidass on brush border cells

92

How are di and Tri peptides absorbed

Cotransported with H+ into the cell. Turn into capillaries in opposite direction as H+

93

How are amino acids absorbed

Cotransporters with Na+ then into the capillaries in the opposite direction as Na+

94

How are small peptides carried across the epithelial cell

Intact in transcytosis

95

Triglycerides are digested into? By?

Monoglyceride
Two free fatty acid

Digested by lipase and colipase

96

Is cholesterol digested

No

97

How do bile salts work

Form a vesicle around fats as fats are not water soluble
Colipase makes gaps in bile allowing lipase in to digest it

98

Bile salts digest fats into what

Absorbable micelles

99

How are fats absorbed

All absorbed individually but combine to form chylomicrons which are packaged in the Golgi and sent to the lymphatic system

100

Where is most liquid absorbed

Small intestine

101

What causes diarrhoea

Normal intestinal water absorption disrupted

102

Describe osmotic diarrhoea

Osmotically active solutes not absorbed. They remain in the GI tract drawing water to them
Ie lactose and sorbitol

103

Describe secretory diarrhoea

Bacterial toxins enhance Cl ion secretion to attempt to flush out the bac. Treated with antibiotics and a foecal transplant or probiotics to bring normal microbiota levels back