Digestion

Question 1

Describe the four basic digestive processes performed by the digestive system (motility)

Answer 1

-Muscular contractions–> mixing and moving

Question 2

What type of muscle tissue does the mixing and moving with muscular contractions?

Answer 2

Smooth muscle, in the esophagus it has some skeletal muscles

Question 3

Describe the four basic digestive processes performed by the digestive system (secretion)

Answer 3

-Digestive enzymes, bile salts, mucus, hormones, buffers, etc.

Question 4

Describe the four basic digestive processes performed by the digestive system (digestion)

Answer 4

Chemical breakdown of large food molecules into smaller subunits for absorption

Question 5

Describe the four basic digestive processes performed by the digestive system (absorption)

Answer 5

Small particles transported from digestive tract –> into body fluids (blood or lymph)

Question 6

Describe why we need to break food molecules down into smaller particles.

Answer 6

• So they are small enough and easier to cross the membrane

- increase surface area to allow enzymes to move

Question 7

Describe the digestion of proteins

Answer 7

Not much protein in mouth, mainly in the stomach

1) Pepsin(from the stomach): protein-> peptides(in stomach)
2) More proteases( from the pancreas): Proteins and peptides-> peptides (in small intestine)
3) Peptidases & dipeptidases( from the small intestine) peptides-> amino acids (in small intestine)

Question 8

Describe the digestion of carbohydrates

Answer 8

1) Salivary amylase (from the salivary glands) stops being active when in the stomach. It breaks down starch->disaccharides (in the mouth)
2) Pancreatic amylase (from the pancreas) starch->disaccharides (in the small intestine)
3) Disaccharidases ( from the small intestine) Disaccharides -> monosaccharides( in the small intestine)

Question 9

Describe the digestion of lipids

Answer 9

Must be physically broken into small enough droplets in order for digestion to be efficient (insufficient without bile in body)

1) By bile (used as an emulsifier) produced in the liver, occurs in the small intestine
2) Lingual lipase (make small amounts in the oral cavity) Lipids-> fatty acids and monoglycerides (in the oral cavity&stomach) small amount of digestion
3) Gastric lipase(from the stomach) Lipids-> fatty acids and monoglycerides (in the stomach) (infants only-milk diet)
4) Pancreatic lipase(from the pancreas) lipids-> fatty acids and monoglycerides(in the small intestine) digestion of fat is less efficient without gallbladder
5) Other lipases (from the pancreas and small intestine) lipids-> fatty acids and monoglycerides( in the small intestine)

Question 10

Briefly describe the mechanisms used in the absorption of carbohydrates, proteins, and lipids.

Answer 10

carbohydrates:
-have to get broken down to monosaccharides, they absorb monosaccharides and are put into capillary of villus(get through cells by secondary active transport and facilitated diffusion)
Proteins:
-have to get broken down by amino acids, they absorb amino acids and are put into capillary of villus (get through cells by secondary and tertiary active transport and facilitated diffusion)
Lipids:
-Packaged as chylomicrons go into lacteal of villus
-Use diffusion into intestinal cell, and exocytosis out
-different because lipids are hydrophobic

Question 11

In general, compare and contrast digestion, absorption, and transport of water-soluble nutrients (proteins and carbs, plus water-soluble vitamins) with lipid-soluble nutrients (fats, oils, and fat-soluble vitamins).

Answer 11

come back to this

Question 12

Describe the function of other secretions of the digestive system: lysozyme

Answer 12

Anti-bacterial enzyme

Question 13

Describe the function of other secretions of the digestive system: IgA (antibodies)

Answer 13

Antibodies in saliva and tears

Question 14

Describe the function of other secretions of the digestive system: hydrochloric acid

Answer 14

Decreases pH, activates pepsinogen, produced by parietal cells (most effective in acidic environment or neutral just not basic

Question 15

Describe the function of other secretions of the digestive system: intrinsic factor

Answer 15

produced by parietal cells; helps us absorb vitamin B12 (needed for cell division to make RBC)

Question 16

Describe the function of other secretions of the digestive system: bile

Answer 16

used as an emulsifier, produced in the liver

Question 17

Describe the function of other secretions of the digestive system: bicarbonate ions

Answer 17

they neutralize the pH in the small intestine, highly acidic

Question 18

Describe the function of other secretions of the digestive system: mucus.

Answer 18

Mucins-> mucus; lubricates food and helps protects the digestive tract

Question 19

Describe how different aspects of digestive function are regulated by the following hormones: Gastrin

Answer 19

Produced in part by cells of the stomach (also by cells of the duodenum) and will increase activity in the stomach to help facilitate digestion (from stomach and duodenum)
Stimulated by:
-the arrival of food and stretching of the stomach, also by nervous stimulation (vagus nerve)
-or by the signals in the stomach or small intestine(duodenum) with large amounts of undigested protein
-Causes more gastric secretion(acids and enzymes), increased gastric motility (the only 1/6 hormone that increases activity in the stomach)

Question 20

Describe how different aspects of digestive function are regulated by the following hormones: Secretin

Answer 20

From duodenum

• Stimulated by the release of acidic chyme into the small intestine
• causes the pancreas to release bicarbonate ions(to neutralize the acidic chyme) and liver to secrete bile
• Inhibits gastric secretion, decreases gastric motility
• Slows down activity in the stomach
• Increase secretion from the pancreas and liver

Question 21

Describe how different aspects of digestive function are regulated by the following hormones: Gastric Inhibitory Peptide (GIP)

Answer 21

AKA “Glucose-dependent insulinotropic Hormone”

• From duodenum
• respond to fatty acids and glucose in chyme
• Inhibits acid production and peristalsis in stomach(slows rate of chyme being dumped into small intestine)
• Stimulates release of insulin from pancreas
• Stimulates lipid synthesis and glucose use
• This hormone will get the pancreas to secrete insulin in anticipation of a rise in blood glucose levels before the levels actually have the chance to rise.

Question 22

Describe how different aspects of digestive function are regulated by the following hormones: Cholecystokinin (CCK)

Answer 22

• From the duodenum
• In response to the arrival of chyme, especially with fatty acids and partially digested proteins
• Stimulates gall bladder to contract(release bile) and pancreas to release digestive enzymes
• Causes relaxation of hepatopancreatic sphincter; inhibits gastric secretion; may reduce hunger (CNS target)

Question 23

Describe how different aspects of digestive function are regulated by the following hormones: Vasoactive intestinal peptide (VIP)

Answer 23

From duodenum

• Respond to the arrival of chyme
• Stimulates secretions of small intestine inhibits acid production in the stomach, dilates intest. capillaries( to aid in the removal of absorbed nutrients)

Question 24

Describe how different aspects of digestive function are regulated by the following hormones: Enterocrinin

Answer 24

• has to do with mucus
• Released when chyme enters the duodenum
• Stimulates mucin production by submucosal glands

Question 25

Describe the three phases of gastric secretion (cephalic phase)

Answer 25

Increases activity in the stomach (to help digest food)
-Sight, smell, taste, and thought of food
-CNS brain sends a signal to the stomach to prepare for the arrival of food (vagus nerve)
OVERALL EFFECT: increased production of gastric juice(mucus, pepsin, acid)

Question 26

Describe the three phases of gastric secretion (gastric phase)

Answer 26

When food arrives in stomach:
-distension of stomach wall
-increase in stomach pH
-Presence of undigested food (especially protein)
-Increased gastric secretion
-Contraction of muscularis externa (churning)
Hormone involved : Gastrin

Question 27

Describe the three phases of gastric secretion (intestinal phase)

Answer 27

Intestine telling stomach what to do
Arrival of chyme in duodenum
-Detected by stretch receptors and chemoreceptors in duodenum
-Slows down activity of stomach to ensure small intestine has time to process chyme efficiently (enterogastric reflex; small intestine-> stomach)
-increases mucus production in small intestine
Hormonal effects: CCK, GIP & SECRETIN

Question 28

Describe how the digestive function is regulated by these local reflexes: stretch receptors in the stomach (during the “gastric phase”)

Answer 28

Stretch receptors stimulate myenteric and submucosal plexuses, leads to increased gastric activity

Question 29

Describe how the digestive function is regulated by these local reflexes: stretch receptors in the duodenum (the enterogastric reflex)

Answer 29

Stretch receptors inhibit myenteric plexus, leads to decreased gastric activity.
Enterogastric reflex= communication from the intestine back to the stomach

Question 30

Describe how digestive function is regulated by central reflexes, involving the CNS (stretch receptors in stomach)

Answer 30

triggered by stimulation of stretch receptors in stomach wall -> CNS

Question 31

Describe how digestive function is regulated by central reflexes, involving the CNS (gastroenteric reflex)

Answer 31

Starts in the stomach, then sends info to the CNS then motor output to the intestine will increase activity in the small intestine

Question 32

Describe how digestive function is regulated by central reflexes, involving the CNS (gastroileal reflex)

Answer 32

Starts in the stomach, then sends info to the CNS, then motor output to the ileocecal valve to get material moving from the small intestine on to the large intestine