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Mammalian Physiology > Slide Set 9 - The Digestive System > Flashcards

Slide Set 9 - The Digestive System Flashcards

1
Q

What are the 4 major functions of the digestive system?

A
  1. Motility: muscular contractions that mix the food and move it forward in the digestive tract
  2. Secretion
  3. Digestion
  4. Absorption
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2
Q

What is the route of the digestive system?

A

Oral cavity –> esophagus –> stomach –> small intestine –> large intestine –> rectum

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3
Q

What is the name of the surface folding of the stomach called?

A

Rugae

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4
Q

The mucosa lines the ______ surface of the digestive tract.

A

luminal

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5
Q

What 3 layers is the mucosa divided into?

A
  1. Mucosa membrane - an inner epithelial layer which serves as a protective surface and is modified for secretion and absorption
  2. Lamina propria - a thin layer of connective tissue. Location of gut associated lymphoid tissue: important in defence against disease-causing intestinal bacteria
  3. Muscular mucosa - sparse layer of smooth muscle
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6
Q

What 3 type of cells does the mucous membrane layer of the mucosa contain?

A
  1. Exocrine gland cells: secrete digestive juices
  2. Endocrine gland cells: secrete blood-born gastrointestinal hormones
  3. Epithelial cells: specialized for absorbing digestive nutrients
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7
Q

What do the cells at the base of each crypt secrete?

A

bactericidal enzymes

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8
Q

What are the 3 compartments of the small intestine?

A

duodenum
jejunum
ileum

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9
Q

Each villus contains an _______ and a ______ to facilitate absorption of nutrients and release hormones.

A

artery, vein

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10
Q

What is the epithelial lining of the stomach called? How are they similar to the epithelium lining of the small intestine?

A

rugae, highly folded

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11
Q

What are the depressions in rugae called? What is found between them?

A

gastric pits. Coiled glands are found below these pits in the fundus and body of the stomach

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12
Q

What is the outer most later of the stomach called?

A

serosa

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13
Q

What does the serosa secrete? What is the function of this?

A

Secretes serous fluid which lubricates and prevents friction between digestive organic and surrounding internal organs (called viscera)

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14
Q

Saliva is produced by what 3 major pairs of salivary glands?

A
  1. Parctid gland
  2. Submanditurar gland
  3. Subingual gland
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15
Q

What is the composition of saliva?

A
  1. 5% H2O

0. 5% electrolytes and protein (amylase, mucus, lysozyme)

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16
Q

What is the function of salivary amylase and what cells secrete it? salivary mucus? water? Lysozyme?

A
  1. serous cells secrete it. digests COH
  2. mucus provides lubrication 3. facilitates swallowing by moistening food
  3. destros bacteria - saliva rinses away material that could serve as a food source for bacteria
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17
Q

amylase works best at what pH?

A

slightly basic

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18
Q

What is the structure of the esophagus in active and resting state?

A

Active: straight muscular tube
Resting: flattened

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19
Q

What type of epithelial cells is the esophagus lined with?

A

stratified squamous epithelial

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20
Q

The esophagus extends between the _____ and ______.

A

pharynx and stomach

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21
Q

What is located at both ends of the esophagus? Function and name of 1st one, function and name of 2nd one

A

Sphincters!

  1. Pharyngoesophageal sphincter which keeps the entrance closed to prevent large volumes of air from entering the esophagus and the stomach
  2. gastroesophageal sphincter: prevents reflux of gastric contents
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22
Q

During motility, as the bolus moves forward, do the walls of the intestine move forward?

A

No, they just contract which moves the food forward. Segmental contractions promote mixing

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23
Q

What 3 sections is the stomach divided into?

A

Fundus
Body
Antrum

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24
Q

What is the pyloric sphincter of the stomach?

A

The barrier between the stomach (Antrum section) and the upper part of the small intestine

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25
Q

In what two organs does peristalsis take place?

A

stomach and small intestine

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26
Q

Mixing actions in the stomach include both _____ and _______. What is this action called?

A

propulsion, retropulsion

gastric motility

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27
Q

What is chyme?

A

partially digested food mix

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28
Q

What happens as peristalsis contractions become stronger in the stomach?

A

some liquid chyme squirts past the pyloric sphincter and into the duodenum - the stomach continues to mix the chyme as it is gradually released into the duodenum

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29
Q

What inhibits further emptying of acidic gastric contents from the stomach into the duodenum?

A

Unneutralized acidic foods in the duodenum inhibits further emptying of acidic gastric contents. So basically gastric contents are only released again once the chyme in the duodenum is neutralized from the bicarbonate released from the pancreas.

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30
Q

____ is digested and absorbed more slowly than other nutrients.

A

Fat - takes longer to be neutralized by the small intestine?

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31
Q

When _______ of duodenum contents start to rise, the pyloric sphincter of the stomach closes. What builds up in order to cause this?

A

osmolarity / hypertonicity. Build up of amino acids and glucose molecules

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32
Q

What is distension?

A

too much chyme in duodenum inhibits gastric emptying of even more gastric contents

33
Q

What 2 responses can fat, hypertonicity, acid, or distension in the duodenum trigger?

A
  1. neural response - enterogastric reflex: acts to slow peristalsis activity - smooth muscle contractions - autonomic system
  2. Hormonal response: release of Gastric Inhibitory Peptide (GIP) acts on gastric muscle to decrease peristalsis and thus slow passage of food into duodenum
34
Q

What are psychological factors that influence gastric motility?

A
  1. Emotions: sadness and fear decreases motility, while anger and aggression increases motility.
  2. Intense pain - inhibits motility
35
Q

What are two distinct areas of gastric mucosa that secrete gastric juice?

A

Oxyntic mucosa (lines body of fundus)

Pyloric glans area (PGA) (lines the antrum)

36
Q

What are the 3 phases of gastric secretion? What is this entire phase called?

A
  1. sensation / thought about food = relayed to brainstem
  2. in response, parasympathetic signals to the gastric mucosa are initiated
  3. secretion of gastric juice

This is called the Cephalic phase

37
Q

What happens during the gastric phase? What hormone is secreted and what does it do?

A

distension of the stomach caused by the presence of food triggers local and parasympathetic reflects that increase secretion of gastric juice

Gastrin - secreted by mucosa in presence of food causes increased secretion of gastric juice

38
Q

what happens in terms of hormonal secretions in the stomach as food enters the duodenum?

A

stomach activity is inhibited by decreased production of gastric juice from GIP (gastric inhibitory peptide), CCK, and secretin. This all opposes the action of gastrin.

At the same time, this signals pancreas to increase ejection of bile required to neutralize HCl from acidic chyme

39
Q

What are the 4 exocrine cells and what are their functions?

A
  1. Mucous cells: secrete mucus, protect against pepsin and acid
  2. Chief cells: secretes pepsinogen when activated which begins protein digestion
  3. Parietal cells: Secrete HCl which activates pepsinogen which activates pepsin enzyme - this provides acidic medium for optimal pepsin activity. Denatures proteins, breaks down connective tissue & muscle fibres, kills microorganisms ingested with food, intrinsic factor important for vitamin B12 absorption
  4. Enterochomaffin-like cells (ECL): secrete histamine which stimulates parietal cells
40
Q

Where are endocrine cells located in the stomach?

A

in the pyloric gland area

41
Q

What are the 2 endocrine cells located in the stomach?

A

G-cells and D-cells

42
Q

Function of G-cells? What does this ensure?

A

secrete gastrin which stimulates exocrine cells to secrete gastric juice into the lumen of the stomach which has high HCl and pepsinogen

This ensures that when there is food in the stomach there will be enough juice and enzymes there to digest it - promotes digestion.

43
Q

Function of D-cells?

A

Produce somatostatin which inhibits parietal cells, G-cells, and ECI cells

44
Q

How is HCl formed?

A

In parietal cells: Carbon dioxide + water = carbonic acid. This dissociates into H+ and HCO3. H+ moves into the stomach’s lumen via an H-K co-tansporter which transports K+ out of the lumen and H+ into it. As HCO3 exits the parietal cell into the blood, Cl- is transported in. Cl- then moves into the lumen of the stomach via a Cl- channel.

45
Q

In what 3 ways does the gastric mucosal barrier enable to stomach to contain acid without injuring itself?

A
  1. luminal membranes are impermeable to H+ so HCl can not penetrate into the cells
  2. cells are joined by tight junctions to prevent HCl from penetrating between them
  3. contains a mucus cover for extra protection
46
Q

What are 2 causes of damage to the gastric mucosal barrier?

A
  1. Helicopter pylori - bacteria

2. emotions/stress - as it can increase gastric juice secretion

47
Q

Helicobacter pylori

  1. causes what % of ulcers?
  2. Where are they located?
  3. Use _______ to burrow below mucus cells
  4. What part of the cells do they damage?
  5. Allow ____ to damage intestinal tissue
  6. Treatment
A
  1. 60
  2. in Fundus to hide from HCl
  3. flagella
  4. mucus layer and tight junction
  5. HCl
  6. antibiotics
48
Q

The pancreas is a mixture of _______ and _______ tissue

A

exocrine, endocrine

49
Q

Structure and location of pancreas?

A

elongated gland located behind and below the stomach

50
Q

What is the endocrine function of the pancreas? Exocrine?

A
  1. islets of Langerhans - alpha and beta cells that secrete insulin and glucagon
  2. Secretes pancreatic juice and aqueous alkaline solution
51
Q

What is the pancreatic juice that the exocrine glands of the pancreas secrete made up of?
What cells secrete this?

What is the the aqueous alkaline solution important for? What type of cells secrete it?

A
  • trypsinogen, lipases, nuclease
  • acinar cells
  • neutralizing stomach contents in duodenum
  • duct cells that line the pancreatic duct (NaHCO3 solution)
52
Q

What 2 pancreatic enzymes is exocrine secretion regulated by?

A
  1. Secretin
  2. CCK

both act to stimulate release of pancreatic juice

53
Q

What two proteolytic enzymes can be found in the pancreas?

A
  1. trypsinogen (inactive form of trypsin)
  2. Chymotrypsinogen (inactive form of chymotrypsin)

Function: digest protein

54
Q

What is special about pancreatic lipase?

A

only enzyme secreted throughout entire digestive system that can digest fat

55
Q

What is the importance of the liver to the digestive system?

A

secretion of bile salts which are important for fat digestion

56
Q

The liver is the largest _____ in the body

A

gland

57
Q

Liver consists of 2 _____ which are highly _______.

A

lobes, vascularized

58
Q

What are 4 functions of the liver?

A
  1. detoxification
  2. bile secretion
  3. stores iron, vit D, A, B12
  4. site of hematopoiesis (creation of new blood cells) during fetal development
59
Q

Can the liver regenerate?

A

yes

60
Q

The ______ ducts fuse with the ________ ______ duct to form the common bile duct that enters into the __________.

A

hepatic

gallbladder cyst

duodenum

61
Q

Bile salts are formed in the ______ from ________

A

liver, cholesterol

62
Q

Bile is actively secreted by the ______ and actively diverted to the ________ between meals

A
  1. liver

2. gallbladder

63
Q

Where does the bile enter after a meal?

A

duodenum

64
Q

What is lecithin? What is its function?

A

A phospholipid - derivative of cholesterol that converts large fat globules into a liquid emulsion

65
Q

What happens to lecithin after participation in fat digestion and absorption?

A

most are reabsorbed into the blood

66
Q

What are the 5 steps in digestion and absorption of fats?

A
  1. bile salts from liver coat fat droplets
  2. Pancreatic lipase and collapse break down fats into monoglycerides and fatty acids stored in micelles
  3. monoglycerides and fatty acids move out of micelles and enter cells by diffusion. At the same time, cholesterol is transported into cells by a membrane transporter.
  4. absorbed fats combine with cholesterol and proteins in the intestinal cells to form chylomicrons
  5. Chylomicrons are released into the lymphatic system
67
Q

Where are the 3 divisions of the small intestine?

A
  1. duodenum: uppermost portion that the pyloric end of the stomach attaches
  2. Jejunum: commences at point where the tubes turn downwards
  3. Ileum: no clear demarcation from jejunum
68
Q

What is segmentation of GI tract?

A

alternation of contracted ring like regions that occur at intervals along the GI tract to chop and mix the food contents.

69
Q

What is segmentation initiated by?

A

pacemaker cells in small intestine which produce basic electrical rhythm.

70
Q

What influences circular smooth muscle responsiveness during segmentation?

A

distension

71
Q

What are the 2 main functions of the small intestine?

A
  1. mixing chyme with digestive juices secreted into small intestine lumen
  2. exposing all chyme to absorptive surfaces of small intestine mucosa
72
Q

What sweeps the intestines clean between meals?

A

the migrating motility complex

73
Q

What does the juice secreted by the small intestine NOT contain?

A

digestive enzymes

74
Q

Where is fat entirely digested in our body?

A

within small intestine lumen by pancreatic lipase

75
Q

Where does most of the absorption in the small intestine take place?

A

duodenum and jejunum

76
Q

The lining of the small intestine is replaced evert ___ days

A

3

77
Q

What are the 4 divisions of the large intestines?

A
  1. cecum
  2. ascending colon
  3. transverse colon
  4. descending colon
78
Q

Slides 51 & 52 = big overview

A

-

79
Q

What is saliva rich in that also creates a perfect environment for amylase to live in?

A

bicarbonate buffers

Mammalian Physiology (6 decks)

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