Digestion 1 - After Midterm

Question 1

Alimentary Canal
* Gastrointestinal or GI tract
pathway

Accessory Glands

Answer 1

Alimentary Canal
* Gastrointestinal or GI tract
* Mouth
* Pharynx
* Esophagus
* Stomach
* Small intestine (SI)
⬧ Duodenum
⬧ Jejunum
⬧ Ileum
* large intestine (LI)

Accessory Glands
LST GP
Teeth, tongue
Salivary Glands
Gallbladder
Liver
pancreas

Question 2

GI tract regulatory mechanisms - Intrinsic and extrinsic controls
Short reflexes
*
Hormones
*
*
Long reflexes
*
⬧ Eg.

Four digestive Processes

Answer 2

Short reflexes
* Enteric nerve plexuses (gut brain) respond to
stimuli in the GI tract
Hormones
* from stomach and small intestine
* stimulate target cells in same or different organs
Long reflexes
* Respond to stimuli inside or outside the GI tract
⬧ Eg. Thought or smell of food
* Autonomic control / Central Nervous system

Four digestive Processes
Motility(able to move), secretion, absorption, digestion

Question 2

Digestive Activities
Six essential activities

AFTER

Digestive Tract
same general structure from esophagus to anus
Four major tissue layers

Submucosa
*
Muscularis externa
*
Serosa
*
Mucosa
*

Answer 2

MADPIC
1. Ingestion
2. Propulsion
3. Mechanical digestion
4. Chemical digestion
* Involves secretion
5. Absorption
6. Defecation

AFTER

Mucosa
* Innermost layer / secretions / absorption
Submucosa
* Blood / nerve supply
Muscularis externa
* motility
Serosa
* Outer CT layer

Question 3

GI tract Sensory Receptors
Mechanoreceptors respond to
*
Chemoreceptors respond to
*
*
Both Initiate reflexes that
*
*

Extrinsic controls –
Intrinsic control -
Both affect
*
*

Answer 3

Mechanoreceptors respond to
* Stretch (as food moves through)
Chemoreceptors respond to
* Osmolarity and pH changes
* Digestive substrates and end products (ie. Food, sugar or protein)
Both Initiate reflexes that
* Activate or inhibit digestive glands
* Stimulate smooth muscle to mix and move lumen
contents

Extrinsic controls – from outside digestive tract (sight smell)
Intrinsic control - within digest tract
Both affect
* motility
* secretion of enzymes/hormones

Question 4

Motility- what is it?
Two types
1)
2)

AFTER

Secretion of 3 hormones. what are they and what do they affect?
Digestive Enzymes. Where?
Mucous. where?

Answer 4

Muscular contractions that mix and move
forward the contents of the digestive tract

1) Peristalsis * Propulsive
2) Segmentation * Mixing movements
⬧ promotes digestion of foods
⬧ Facilitates absorption

AFTER

CCK, gastrin, secretin
* Affect motility and secretions
Digestive Enzymes
- mouth, Stomach, Small intestine
Mucous
- Mouth, stomach, S. Intestine

Question 5

Villi and microvilli. purpose?

… digestion by …
Chemical break-down by enzymes of

Answer 5

Villi and microvilli
Increase surface area for absorption

Mechanical digestion by chewing
Chemical break-down by enzymes of
- Carbohydrates
- Proteins
- Fats

Question 6

Digestion of Carbohydrates
Starch – usually … of carbohydrates
Dissaccarides (eg. , )
Monosaccarides (eg. )
Complex carbohydrates (i.e. )

Enzymes
Amylase
* From…
* From…
SI enzymes (from ; acts in)
*…
* …

Pathway!!!

Complex Carbohydrate Digestion
Humans … to digest … (eg.)
α -
Fibre moves to .. for… Digestion
Fermentation
*

Answer 6

Starch – usually 2/3 of carbohydrates
Dissaccarides (eg. Sucrose, Lactose)
Monosaccarides (eg. Glucose)
Complex carbohydrates (i.e. fibre)

Amylase (breakdown carbs)
* From salivary glands (acts in Mouth)
* From pancreas (acts in SI)
SI enzymes (from SI wall ; acts in SI)
* Lactase
* Maltase

Humans lack enzyme to digest complex carbohydrates (eg. oligosaccarides)
α - galactosidase
Fibre moves to LI for E.Coli Digestion
Fermentation
* Gas production

Question 7

Protein digestion path
from protein to polypeptides, dipeptides, A.A

Answer 7

Question 8

Protein Digestion
- …g per day needed
- Essential Amino acids
Enzymes
-… (Stomach)
From Pancreas (acts in …)
* …
* ….
* ….
- … (SI)

… enzymes needed to break the bonds between the different…

Answer 8

• 50-60 g per day needed
• Essential Amino acids
  Enzymes
  Pepsin (Stomach)
  From Pancreas (acts in SI) TCA
• Trypsin / chymotrypsin
• Carboxypepsidase
• Aminopeptidase
  Dipeptidases (SI)

Many enzymes needed to break the bonds between the different amino acids

Question 9

Fat Digestion
polar?
Need … such as
…
* Made in …, stored in …
* Increases … for …
Enzymes
- … (from …, acts in …)

Fat digestion pathway

Answer 9

Non-polar
Need emulsifier
Bile(NOT AN ENZYME)
* Made in liver, stored in gall bladder
* Increases surface area for lipase
Enzymes
Lipase (from pancreas, acts in SI)

Question 10

… acts on … droplets
Get … and …
Can enter … or form …

Within cell – forms …
* Absorbed into …

AFTER

Nucleic Acids
Digested by …
* From …, act in …
* … enzymes
Vitamins
- … by carriers

Answer 10

Lipase acts on emulsified droplets
Get monoglyceride and fatty acids
Can enter absorptive cells or form micelles

Within cell – forms chylomicron
* Absorbed into lymph

AFTER

Nucleic Acids
Digested by Nucleases
* From pancreas, act in small intestine
* SI enzymes
Vitamins
Absorbed whole by carriers