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Physiology 2130 > Gastrointestinal Physiology > Flashcards

Gastrointestinal Physiology Flashcards

1
Q

What are the 4 processes of the digestive system? Describe each one.

A
  1. Secretion
    - Exocrine = into lumen of digestive tract
    - Endocrine = into bloodstream
  2. Digestion
    - mechanical
    - chemical (enzymes)
  3. Motility
    = coordinated movements/contracts through GI tract
    - propels food through each tract segment
    - can participate in mechanical digestion (can’t control it though)
  4. Absorption
    = movement of macronutrients –> cells of digestive tract –> bloodstream
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2
Q

Function of the STOMACH

A

= holding centre until the bolus can enter the intestines where enzymes can come digest

  • liquifies the bolus to enhance enzymatic digestion
  • mechanically breaks down contents with coordinated muscular contractions
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3
Q

Function of the SALIVARY GLAND

A

= makes saliva that have enzymes for digestion
- a converging duct system (single gland cell secretes into its own duct, and multiple ducts flow into large ducts before all meeting at one main duct)

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4
Q

Function of the GALLBLADDER

A

= stores bile made by the liver

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5
Q

Function of the COMMON BILE DUCT

A

= where contents of the liver + pancreas + gallbladder gather together and enter the SMALL INTESTINE where it interacts with the stuff

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6
Q

Define ACCESSORY ORGAN (List them.)

A

= doesn’t directly come in contact with food stuff

Salivary Gland
Gallbladder
Liver
Pancreas

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7
Q

What path does the food take?

A

Mouth –> Esophagus –> Stomach –> Small Intestine –> Large Intestine –> Rectum

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8
Q

Functions of SALIVA

A
  • helps us talk (so tongue won’t get stuck on roof)
  • keep teeth clean and prevent cavities
  • digest food (chemical digestion in mouth)
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9
Q

List and describe the 3 stages of swallowing

A
  1. VOLUNTARY STAGE
    - the bolus is moved from mouth –> pharynx (back of motuh) by You
  2. PHARYNGEAL STAGE
    - Involuntary –> takes over once bolus is far enough back
    - nasal cavity + trachae closed off (via nervous reflex) and pushed towards Esophagus
  3. ESOPHAGEAL STAGE
    - Involuntary
    - bolus moving from esophagus –> stomach
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10
Q

Define MASTICTATION

A

= chewing; mechanical manipulation of food into a bolus
–> a form of mechanical digestion and motility

  • mastication + chemical digestion (salivary amylase and lingual lipase) is what starts digestion at the mouth
  • *Lingual lipase secreted in the mouth but not activated until stomach
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11
Q

Define PERISTALSIS

A

= coordinated contractions and relaxations of both circular and longitudinal muscle in ONE Direction that moves the bolus down the esophagus

  • under the control of medulla oblongate (involuntary)
  • muscular movement (don’t need gravity)
  • movement = relaxation of muscle in front of bolus, contraction of muscles behind bolus
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12
Q

What is Secondary Peristalsis?

A

= a much more vigorous peristalsis

= initiated if food still lodged in the esophagus

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13
Q

What are the 3 parts to the stomach? And what/where are the sphincters located?

A
  1. Fundus
    - - lower esophageal sphincter (prevents going back up) –
  2. Body
  3. Antrum
    - - pyloric sphincter –

** the 3 layers secrete different things at different ratios

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14
Q

Layers of the Stomach

what are they, what is in each layer, functions of each layer

A

MUCOSA –> eggs

  • single layers of cells that are either endocrine (secrete hormones) or exocrine (secrete acid, enyzmes)
  • rugae (large folds that increase V and SA)
  • pits (deep invaginations)

SUBMUCOSA –> cheese (sticks it together)

  • Submucosal plexus; neurons important for controlling cells/receiving info from them
  • connective tissue, which adheres mucosa to smooth muscle

SMOOTH MUSCLE (MUSCULARIS EXTERNA) –> meat

  • circular muscle + longitudinal muscles to change shape of the stomach
  • Myenteric plexus

SEROSA –> bun (keeps it together, foundation)

  • external layer
  • dense connective tissue
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15
Q

What are the 3 types of exocrine cells in the gastric glands? What do they secrete? What’s the functions of each secretion?

A
  1. MUCUS NECK CELLS
    - secretes mucus (to protect stomach from acid)
  2. CHIEF CELLS
    - secretes pepsinogen (activated but doesn’t do anything yet) and gastric lipase (digests lipids)
  3. PARIETAL CELLS (oxyntic cells)
    - secretes intrinsic factor, HCl (all are extrinsic factors therefore go into stomach)
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16
Q

What is a G cell?

A

= enteroendocrine cell in the gastric glands of the stomach

  • secrete GASTRIN (hormone) –> gastric motilitycontraction, acid release, & and function
  • gastrin travels around the body but comes back and acts on the stomach itself
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17
Q

Describe Mechanical Digestion in the mouth

A
  • gentle mixing waves (every 30sec) = mix food with secretions of gastric glands
  • vigorous mixing = as digestion proceeds, begins at the Body and intensifies towards pyloric pump
  • Gastric Emptying = pyloric sphincter is slightly open so a small amount of chyme enters into duodenum
  • but most of the chyme pushed back into Body so that more mixing can occur
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18
Q

Describe Chemical Digestion in the Mouth

A

Acidic gastric juices…

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19
Q

What are the different functions of acid in the stomach?

A
  • Activate Lingual Lipase
    • lipid digestion
    • secreted in mouth, activated with acidic environment
  • Activate pepsin
    • protein digestion
    • converts pepsinogen into pepsin
  • Inactivate salivary amylase
    • no carb digestion in stomach
  • Kill microbes
    -Denature proteins
  • Stimulate secretion of hormones
    ^ HCl = ^ gastrin = ^ motility = ^ HCl
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20
Q

Describe the 3 regions of the small intestine

A

DUODENUM

  • where enzymes mix with chyme
  • most chemical digestion occurs here
  • can increase/decrease motility to optimize chem. digestion
  • where liver/pancreas secretions enter via bile duct and interact with chyme

JEJUNUM

  • many villi to increase SA for optimal absorption
  • most absorption occurs here

ILEUM

  • less villi, but can still absorb any nutrients that weren’t absorbed before
  • backup if jejunum was removed
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21
Q

Describe the Layers in the Small Intestine

A

MUCOSA

  • epithelial cells (endocrine or exocrine)
  • capillary system (lyphatic vessels + capillary vessels)
SUBMUCOSA
- Submucosal plexus
- connective tissue, adheres mucosa to muscularis
MUSCULARIS
- smooth muscle layer
- circular muscle + longitudinal muscles
- Myenteric plexus

SEROSA

  • dense connective tissue
  • external layer that holds small intestine together
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22
Q

Describe SEGMENTATION

A

= localized mixing contractions that increase interactions of chyme with the absorptive cells in mucosa

  • sporadic, shove back and forth
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23
Q

Types of cells in the intestinal wall and their functions

A

ABSORPTIVE CELLS

  • epithelial cells with microvilli
  • absorb things across PM into blood vessels/lymphatics

Exocrine:
GOBLET CELLS
- secretes mucus (protect tissue from food and acid)

INTESTINAL GLAND CELLS
- secretes intestinal juice (water, alkaline mucus that neutralizes stomach acid)

PANETH CELLS
- secretes lysozyme (kills microbes)

Endocrine:
S CELLS
- secretes secretin

CCK CELLS
- secretes CCK

K CELLS
- secretes GIP

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24
Q

Define MICROVILLI

A

“brush border”

  • increase the SA of the plasma membrane so that more nutrients can be absorbed
  • have Brush Border Enzymes physically attached to the membrane of absorptive cells within the microvilli
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25
Q

Define BRUSH BORDER ENZYMES

A

= digestive enzymes that break down macromolecules into their smallest, absorbabal level

26
Q

List the Brush border enzymes and what they digest

A

–> only monosaccharides and individual AAs can be absorbed, so these enzymes break them down into that

LACTASE
- breaks down lactose –> glucose + galactose

SUCRASE
- breaks down sucrose –> glucose + fructose

MALTASE
- breaks down maltose –> 2 glucose

AMINOPEPTIDASE
- breaks one AA off the end of the peptide

DIPEPTIDASE
- hydrolyzes a pair of AAs into 2 separate AAs

27
Q

What are the Functions and parts of the LARGE INTESTINE?

A
  • finish absorption (absorbed other contents of the lumen instead of monosaccharides/AAs/fatty acids)
  • produce certain vitamins
  • formation of feces to be expelled
Parts include:
Appendix
Ileocecal valve
Ascending Colon
Descending Colon
Rectum

*Haustra = the folds/bumps of the large intestine

28
Q

What are the 3 parts of motility in the large intestine?

A

Gastroileal Reflex
- presence food in stomach stimulates opening of ileocecal valve

Haustral Churning
- mixing of contents from one haustra to the next, allowing for optimal absorption

Peristalsis & Mass peristalsis
- unidirectional movement of contents out

29
Q

What are the cellular structures of the pancreas?

A
  • Common Bile Duct
  • Pancreatic Duct
  • Ductal cells
  • Acher cells (exocrine)
  • Islet of Langerhans (exocrine)
30
Q

Define PANCREAS

A

= accessory organ that’s connected to the small intestine via two ducts
–> pancreatic secretions come into contact with the chyme in the duodenum, which is vital for digestion

31
Q

Functions of Exocrine Secretions of the Pancreas

A

BICARBONATE

  • by Ductal cells
  • neutralizes acid from stomach

PANCREATIC AMYLASE
- digestion of carbs

PANCREATIC LIPASE
- digestion of fats

TRYPSINOGEN –> Trypsin
- Once cleaved into trypsin (active form), it activates other secretions once in the intestine lumen

CHYMOTRYPSINOGEN –> Chymotrypsin

PROCARBOXYPEPTIDASE –> Carboxypeptidase

PROPHOSPHOLIPASE –> Phospholipase
- digestion of phospholipids

PROCOLIPASE –> Colipase
- lipid digestion

32
Q

Functions of the Endocrine Secretions (and origin)

A

INSULIN

  • made and secreted by beta cells
  • moves glucose into skeletal muscles and adipose cells

GLUCAGON

  • secreted from alpha cells
  • releases glucose from storage into the blood

SOMATOSTATIN

  • secreted by delta cells
  • decreases digestive activity (decreases acid secretion in the stomach)
  • inhibits insulin and glucagon secretion
33
Q

Path of Blood Flow TO THE LIVER

A
  • Hepatic Artery (from the heart = oxygenated blood)
  • Hepatic Portal Vein (from the GI organs = nutrient rich, deoxygenated blood)
  • Hepatic artery and portal vein combine into the Sinusoids (=permeable blood capillaries)
  • Sinusoids join together to deliver blood in a central vein
  • then, this becomes the Hepatic vein (takes deoxygenated blood to heart)
  • comes back again via Hepatic artery (goes towards GI organs and liver)
34
Q

Define HEPATOCYTE

A

= cell of the liver

35
Q

The Functions of THE LIVER

A

SYNTHESIS OF BILE SALTS
= hepatocyte cells in the liver secrete bile, which aids in the digestion/absorption of lips
- bile is secreted into the bile calculus, which then ultimately merges and goes into the common bile duct (via a converging duct system) and is stored in the bile
- biles salts contained in the bile

EXCRETION OF BILIRUBIN
- waste product excreted via bile and urine

METABOLISM OF CARBS, LIPIDS, PROTEINS
- modification/interconversion of molecules

PROCESSING DRUGS/HORMONES
- metabolic and convert drugs

36
Q

Path of Bile

A

Hepatocytes (secreted) –> bile canaliculus –> left and right bile ducts –> Common bile duct

37
Q

Components of Bile

A
  • BILE SALTS
  • help in lipid digestion via helping expose lipids to the lipases that digest them (thru Emulsification)
  • CHOLESTEROL
  • key base of steroid synthesis, made by liver
  • BILE PIGMENTS (Bilirubin)
  • give its yellow/green colour
  • WATER AND IONS
  • to get correct consistency
38
Q

Function of the Gallbladder (and release of bile)

A

= stores the bile made by the liver

  • as bile remains in the gallbladder, it becomes more concentrated (some of the water is reabsorbed back into the body)
  • greater concentration = better at aiding digestion
  • Bile is stimulated for release via hormones (i.e CCK)
  • secretes bile into duodenum via muscular contraction of tissue surrounding gallbladder
39
Q

Cephalic Phase Regulation

stimulus, method of control, result

A

Stimulus: sight, smell, taste of food

Neural Control

  • Medulla oblongata
  • activation of the enteric (intestine) nervous system
Results in:
Increased secretion from
- salivary glands
- stomach
- intestine
Increased motility of
- stomach
- small intestine
40
Q

Gastric Phase Regulation

stimulus, method of control, result

A

Stimulus: presence of food/beverage in the stomach, causing Distention

Neural Control
- sensory info to Submucosal Plexus (causes inc. secretions) and Myenteric Plexus (motility)
Hormonal Control
- gastrin

Results in:
Increased secretions from
- stomach (Hal)
- intestine (mucus)
Increased motility of
- stomach (more gastric emptying)
41
Q

Intestinal Phase Regulation

stimulus, method of control, result

A

Stimulus: presence of chyme in the intestine

Neural Control:
- sensory info to submucosal plexus (secretions) and myenteric plexus (motility)
Hormonal Control:
- secretin (S cells)
- CCK (CCK cells)
- GIP (K cells)

RESULTS IN
Increased secretions from:
- intestine
- pancreas
–> bicarbonate from ductal cells (secretin)
–> digestive enzymes from acinar cells (CCK)
–> insulin from Beta cells (*GIP)
Increased motility of:
- intestine
- gallbladder (contracts and releases bile due to CCK stimulation)

Decreased secretions from:
- stomach (HCl)
Decreased motility of:
- stomach (less gastric emptying)

42
Q

Sources of Carbohydrates

A

Simple

  • Monosaccharides (glucose, galactose, fructose)
  • Disaccharides (sucrose, maltose, lactose)

Complex

  • starch
  • glycogen
43
Q

Sources of Proteins

A
  • animal and plant sources
  • amino acids (20 different kinds)
  • dipeptides
  • tripeptides
  • polypeptides
44
Q

Sources of Fat

A

Triglycerol = glycerol + 3 fatty acids

  • fatty acids are variable in length (4-24C, 18C is most common)
  • can be saturated or unsaturated
45
Q

Two Classifications of Vitamins? What are the vitamins within them?

A

Fat-soluble vitamins (KADE)

  • A
  • D
  • E
  • K

Water-soluble vitamins
- B vitamins (except B12)

46
Q

Process of fat vs. water-soluble vitamin absorption

A

Fat soluble:

  • found in lipid droplets in the GI tract (**need fat in diet to absorb these fat vitamins)
  • formation of micelles by bile and then collapse help absorption
  • no safety mechanism, therefore can overdose on these

Water soluble:

  • requires transporters
  • Vitamin B12 also requires intrinsic factor (from parietal cells in stomach)
  • if too much, transporters become saturated and excess is excreted
47
Q

Described the 4 sets of reactions in Cellular Respiration

A
  1. Glycolysis
    - glucose –> Pyruvate
    - cytoplasm of mitochondria
    - ATP made
  2. Oxidation of Pyruvate
    - pyruvate –> Acetyl CoA
    - in matrix
  3. Krebs Cycle
    - Acetyl CoA metabolized to form ATP and energy carriers (NADH & FADH2)
    - in matrix
  4. Electron Transport Chain
    - energy carriers –> ATP
    - in inner membrane
48
Q

The Fates of Glucose

A
  1. ATP Production
    - oxidized to make ATP
  2. Amino acid synthesis
    - converted to AAs if needed
  3. Glycogen Synthesis
    - storage of glucose (but limited space)
  4. Triglyceride Synthesis
    - when glucose in excess
49
Q

Describe glucose uptake in the cells of the body

A
  • cells take up glucose from the blood –> ATP production
  • via glucose uriporters in membranes
  • requires insulin
50
Q

Describe GLYCOGENESIS

A

Glucose –> G6P –> Glycogen

  • some cells have large capacity to store glucose as glycogen (skeletal muscles, liver)
  • some don’t (brain)
51
Q

Describe GLYCOGENOLYSIS

A

Glycogen –> G6P –> Glycolysis (or –> glucose if liver)

  • glycogen converted to G6P to be used for ATP production
  • Liver = unique –> can form glucose straight from glycogen which can then be released into circulation
52
Q

Describe GLUCONEOGENESIS

A
  • liver creating new glucose molecules from non-carb sources (AAs, lactic acid, and glycerol)

Lactic Acid/AAs –> Pyruvic Acid –> G3P –> G6P
Glycerol –> G3P –> G6P

53
Q

The fates of Lipids

A
  • stored in adipose tissue as fat deposits
  • oxidized to produce ATP
  • formation of structural molecules (phospholipids, myelin sheaths)
54
Q

Triglyceride Storage

A

Triglycerides store in adipose tissue = major energy source

  • 50% in subcutaneous layer of skin
  • rest is around kidneys, genitals, between muscles etc.
55
Q

Describe LIPOLYSIS

A

= Triglycerides –> Glycerol and fatty acids

Glycerol –> G3P (–> glucose)
Fatty acids –> Acetyl CoA
- longer the chain = more Acetyl-CoA produced

56
Q

Describe LIPOGENESIS

A
  • liver and adipose cells can make triglycerides from non-lipid sources (glucose and AAs)

Was (can’t form glycerol) –> Acetyl CoA –> Fatty acids –> Triglycerides
Glucose –> G3P –> Glycerol –> Triglycerides

or, technically, glucose can go all the way down to Acetyl CoA and then be turned into fatty acids

57
Q

Describe KETOGENESIS/Ketone Bodies

A

Ketone Body = two acetyl CoA condensed

  • able to diffuse out of the cell (acetyl-CoA can’t) into blood
  • used by other cells for energy
  • then, ketone bodies converted back into 2 Acetyl CoA and enter Krebs cycle

** heart and kidneys prefer ketone bodies instead of glucose

58
Q

Define Protein Anabolism

A

= formation of proteins from AAs

- as soon as AAs transporter into cells after digestion, they’re reassembled into proteins

59
Q

List some types of proteins

A
  • enzymes
  • hormones
  • structural components
  • transporters
60
Q

Define Protein Catabolism

A

Proteins –> AAs

  • released AAs can be converted to other amino acids
  • hepatocytes can turn AA –> …..
    • fatty acids
    • ketone bodies
    • glucose
    • generate ATP via Krebs (first have to be deaminated to enter Krebs though)

Physiology 2130 (3 decks)

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