CH 9 The Digestive System

Question 1

Digestive System Pathway

Answer 1

Question 2

1. Oral Cavity (amylase, lipase)
2. Pharynx (epiglottis)
3. Esophagus (peristalsis)

Answer 2

1. Oral Cavity: salivary amylase hydrolyzes starch into smaller sugars (maltose and dextrins) and lipase catalyzes the hydrolysis of lipids)
2. Pharynx: epiglottis prevents food from entering the larynx during swallowing.
3. Esophagus: Peristalsis if the autonomic part of the smooth muscle that propels the food (bolus) towards the stomach.

Question 3

4. Stomach

• Parietal Cells (HCl function) and intrinsic factor
• Chief Cells (how is pepsin made and what does it do)
• Mucus Cells function
• G-cells (what do they secrete and function)
• D-Cell, function and what do they secrete

Answer 3

• Parietal cells: Release HCl which kills microbes and denatures proteins. Intrinsic factor: glycoprotein involved in proper absorption of vitamin B12
• Chief Cells: Secrete pepsinogen (pepsinogen + HCL =pepsin which does hydrolysis of proteins (breaks peptide bonds)
• Mucus Cells: Release mucin (mucus) with bicarbonate to protect the layer of stomach so HCl and pepsin don’t damage the stomach
• G-cells: Gastrin stimulates acid secretion by direct action on parietal cells or indirectly through histamine.
• D-Cells: Somatostatin release by H+ is the negative feedback signal that modulates acid and pepsin release.

Question 4

5. Duodenum (brush-border enzymes)

what separates the stomach and small intestine?

chyme?
Cholecystokinin (CCK)?

6. Pancreas (acinar cells) pancreatic amylase?

Enteropeptidase? trypsinogen, chymotrypsinogen, and carboxypeptidases A and B?

Answer 4

Chyme cause the release of enzymes:

pyloric sphincter

• Disaccharidases (maltase, isomaltase, lactase, sucrase)
• Peptidases (dipeptidase)

Cholecystokinin (CCK): stimulates the release of bile and pancreatic juices

6. Pancreas: Acinar cells release pancreatic juices (bicarbonate rich alkaline secretions)

• pancreatic amylase: breaks down large polysaccharides (responsible for carbohydrate digestion)
• Enteropeptidase produced in the duodenum converts trypsinogen into trypsin which digest proteins (also chymotrypsinogen, and carboxypeptidases A and B)

Question 5

7. Liver functions

• Bile (bilirubin) Bile ducts where is it stored?
• Hepatic portal vein?
• Detoxification, ammonia, drugs?

Answer 5

• Bile: amphipathic molecules that engulfs fat with bile salts and bilirubin (the product from the breakdown of hemoglobin)
• Bile moves through the bile ducts where can be stored in the gallbladder and secreted into the small intestine (duodenum)
• Hepatic portal vein: transports nutrient-rich blood from the abdominal portion of the digestive tract. Takes up excess sugar to create glycogen, and stores fat as triacylglycerols. can also reverse it (glycogenolysis and gluconeogenesis)
• Converts ammonia (AA metabolism product) into Uria which can be excreted by the kidneys.

Question 6

8. Small intestine (composed of 3 parts which ones?)

• how do they absorb nutrients? Villi, microvilli?
• type of diffusion?
• how are fats absorbed? small vs large. (triglycerides, chylomicrons, lacteal?

Answer 6

• Duodenum (digestion breakdown), jejunum, and ileum (absorption of nutrients)
• Small intestine is lined with villi and microvilli (increases surface area) for absorption
• They are absorbed by secondary active transport and facilitated diffusion
• Short-chain fatty acids diffuse directly since they are non-polar
• Large fats, glycerol, and cholesterol form triglycerides which then are packed into chylomicrons and are transported through lacteal (small vessels) to the lymphatic system, and then are emptied at the thoracic duct into the blood stream
  *

Question 7

9. Large intestine

• cecum
• colon
• rectum

Answer 7

• cecum: accepts fluid from small intestine
• colon: absorb water and salts to form feces
• rectum: Stores feces, water, bacteria, enzymes, and some bile

Question 8

Hormones and feeding behavior?

leptin

ghrelin