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BPK 205 > Lecture 33 > Flashcards

Lecture 33 Flashcards

1
Q

Oral phase

A
  • under autonomic control (mostly parasympathetic)
  • solubilization of material for taste
  • lubrication and moistening of food

In mouth:
Mechanical digestion of everything begins in mouth through chewing

Carbohydrates in the mouth:
Chemical digestion of carbohydrates begins in mouth because of salivary amylase
Mechanical digestion because chewing up food

Lipids in mouth:
Chemical digestion of lipids also begins in mouth but it’s a small component because lingual lipase (minor contributor to chemical fat digestion)

Antibacterial actions:
- lysozyme will break down anything that shouldn’t be there
- Immunoglobulins are antibodies

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2
Q

The swallowing reflux

A
  1. It is triggered when tongue pushes bolus against soft palate and back of the mouth because there are stretch receptors which sense this
  2. The epiglottis will then fold down over the trachea to help keep swallowed material out of airways. The upper esophageal sphincter relaxes when swallowing to allow food to enter esophagus
  3. Food moves down esophagus through peristalsis contractions and lower esophageal sphincter relaxes
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3
Q

The gastric phase

A
  • mechanical digestion through peristaltic contractions slamming food in stomach wall and breaking it up into bits and pieces
  • chemical digestion are secretions
  • once bolus enters the stomach it is referred to as chyme
  • stomach is an acidic environment (pH=2) that destroys pathogens and destroys epithelial lining of stomach so mucous cells will secrete mucous to cover innermost layer of stomach and bicarbonate to neutralize acidic contents that come in contact with wall
  • storage: release of chyme into SI is regulated by ENS
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4
Q

The mucous-bicarbonate Barrier

A

Is a physical and chemical barrier that protects against acid and damage

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5
Q

Protein digestion in stomach

A
  • mechanical digestion by peristaltic mixing/churning
  • main food that is being chemically digesting in stomach is protein
  • pepsinogen is an inactive protease that is secreted by chief cells of gastric glands and is activated at low pH to pepsin
  • protein is denatured by acid, but pepsin begins protein digestion by cleaving specific peptide bonds of polypeptides
  • protein product entering SI are short/long polypeptides and some free amino acids
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6
Q

Lipid digestion in the stomach

A
  • minor chemical digestion happening here through gastric lipase hydrolyzing triglycerides into monoglycerides and some free fatty acids
  • majority of fat digestion happening in the stomach is mechanical digestion through course emulsification due to stomach contractions. It forms an emulsion of lipids and gastric lipase to get big droplets because large fat droplets are suspended in chyme
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7
Q

Carbohydrate digestion in stomach

A
  • on hold because salivary amylase is denatured because of low pH in stomach
  • mechanical digestion due to peristaltic contractions (mixing and churning)
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8
Q

Secretions into the lumen of the stomach: mucous and bicarbonate

A

Cell type: mucous cells
Function 1: provide a physical barrier between lumen and epithelium
Function 2: neutralize gastric acid that comes in contacts with stomach wall to prevent damage

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9
Q

Secretions into the lumen of the stomach: gastric acid

A

Cell type: parietal cell
Function: activate pepsin, denture protein, destroy pathogens

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10
Q

Secretions into the lumen of the stomach: pepsin(ogen) and gastric lipase

A

Cell type: chief cells
Function 1: major contributor to chemical protein digestion in stomach
Function 2: minor contributor to chemical fat digestion in stomach

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11
Q

The small intestine

A
  1. Regulation of gastric emptying
    - chyme in the small intestine triggers feedback to regulate further release from the stomach
  2. Secretions into the duodenum of the small intestine
    - Epithelial cells: mucous (all the way along your GI tract to keep things lubricated, digestive (brush boarder) enzymes (break things down into absorbable bits)
    - Pancreas: HCO3- (neutralize chyme as it enters SI and to allow pancreatic enzymes to work), digestive enzymes (course, continues chemical digestion in SI)
    - Liver and gallbladder: bile (break things down into almost absorbable bits
  3. Digestion of fats, carbohydrates and lipids
    - mechanical digestion is mostly done
    - chemical digestion through all these enzymes that are being dumped into SI and segmental contractions that are mixing contents of the SI with enzymes that are being dumped in
  4. Absorption
    - free amino acids, sugars, free fatty acids, nutrients, vitamins
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12
Q

Enterocytes

A
  • microvilli increase surface area and have brush border that have a bunch of transporters for absorption
  • digestive enzymes on the brush border
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13
Q

Crypt epithelial cell

A

Secrete water, ions and hormones

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14
Q

Goblet cell

A

Secrete mucous for protection and lubrication

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15
Q

Capillaries

A

Transport absorbed nutrients

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16
Q

Lacteals

A

Transport absorbed fats via lymphatic system

17
Q

The exocrine pancreas

A
  • secretions that are destined to leave the body
  • there are two type of cells here acinar cells and duct cell
  • acinar cells make enzymes to chemically digest protein, carbohydrates and lipids (proteases, amylases and lipases)
  • duct cells make bicarbonate to neutralize chyme that comes from stomach and continue chemical digestion of whatever is in there
18
Q

Biliary secretions

A
  • bile is amphipathic which helps suspend lipids in a solution
  • bile is produced in the liver
  • stored and concentrated in the gallbladder
19
Q

How are carbohydrates absorbed

A
  • as monosaccharides
  • glucose, fructose, galactose
20
Q

Carbohydrate digestion in small intestine

A
  • most digestion occurs here for carbohydrates
  • continued mechanical digestion through segmental contractions by mixing and mashing
  • chemical digestion through pancreatic amylase secreted into the lumen of the duodenum breaking down carbs to tri/disaccharides
  • brush border enzymes on the apical surface of epithelial cells of the duodenum further break carbs down into single sugars
21
Q

Example of brush border enzymes

A

Maltase, sucrase and lactase

22
Q

Course enzymes

A
  • pancreatic amylase
23
Q

Fine enzyme

A
  • maltase
  • sucrase
  • lactase
24
Q

Protein digestion in small intestine

A
  • mechanical digestion through segmental contraction that’s mix and mash back and forth
  • chemical digestion through cleavage by endo- and exopeptidase
  • trypsin, chymotrypsin, carboxypeptidase
  • Product : di and tri peptides and free amino acids
25
Q

Endopeptidases

A

Cleave internal peptide bonds

26
Q

Exopeptidases

A

Cleave terminal (at C or N) peptide bonds

27
Q

Brush border enzyme for protein

A

Aminopeptidase

28
Q

What are the functions of fats

A
  • provide high density source of energy and reserve
  • form hormones
  • are a part of cell membranes
  • provide insulation and shock absorption
  • transport fat soluble vitamins and other compounds
29
Q

Majority of fats are stored as

A

Triglycerides

30
Q

Lipid digestion in small intestine

A
  • major chemical digestion through pancreatic lipase because fat droplets are small enough for pancreatic lipase to come in and do its job
  • mechanical digestion by bile salts through the process of fine emulsification which increases SA and eventually forms a micellar solution. Which are composed of teeny tiny fat droplets due to mixing of bile salts, pancreatic amylase and chyme through segmental contractions with teeny tiny droplets now we can get the break down of triglycerides into free fatty acids that can be absorbed by pancreatic lipase and colipase
31
Q

What is needed when micelles are brought near enterocytes

A

Nothing they are hydrophobic so they will pass without the help of need of transporters

32
Q

Fat absorption

A
  • bile salts help with fine emulsification and coat fat droplets
  • pancreatic lipase and co lipase break down fats into monoglycerides and fatty acids stored in micelles
  • monoglycerides and fatty acids move out of micelles and are absorbed across the apical membrane of enterocytes
  • cholesterol is transported into cell and combine with absorbed fats and proteins to form chylomicrons
  • chylomicron will enter lacteal and be removed by lymphatic system
33
Q

The large intestinal phase

A
  • 1.4L/day of unabsorbed liquid enters the large intestine
34
Q

Functions of small intestine

A
  • fine tuning of water and salts, so further absorption of water and electrolytes
  • supports and environment that facilitates colonization by healthy bacteria
  • bacteria digests fibers (cellulose) and then we absorb them
  • storage of waste in rectum till it can be eliminated
35
Q

Colonic microflora

A
  • digest fiber
  • produce vitamin k (50% of total need)
  • limit growth or invasion of pathogens
36
Q

Defecation composed of

A
  • undigestible material, dead bacteria and epithelial cells, biliary metabolites and H2O
37
Q

What is it called when you have presence of fats in fecal matter

A

Steatorrhea

38
Q

Where along the way could there be a problem if there is a presence of nutrient along the way

A
  • could be a problem with liver and bile synthesis
  • could be a problem with gallbladder of bile concentration or release
  • could be lack of brush boarder enzymes
  • lack of transporters

BPK 205 (31 decks)

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