Section 9: 9.3 - Organs specialized for sequential stages of food processing form the mammalian digestive system

Question 1

What is peristalsis?

Answer 1

Waves of contraction and relaxation of smooth muscle tissue that pushes food along the alimentary canal.

Question 2

What are sphincters?

Answer 2

Ring-like valves at key points to regulate passage of material between compartments.

Question 3

What is the function of teeth in digestion?

Answer 3

Mechanical digestion

Question 4

What is the function of salivary glands in digestion?

Answer 4

Deliver saliva into the oral cavity, initiating chemical digestion

(Primarily affects starch)

Question 5

What is the function of the tongue in digestion?

Answer 5

It investigates whether an item is food and can stimulate rejection if not. It also helps shape the food into a ball (bolus) and pushes it into the pharynx (throat).

The pharynx opens into the trachea (to the lungs) and esophagus (to the stomach)

Question 6

What are the functions of the stomach? (2)

Answer 6

1. Chemical digestion of proteins
2. Food storage

It can hold 2 litres of food and fluid

Question 7

What are some details about stomach chemistry? (Gastric juice)

Answer 7

1. Gastric juice is mixed with food (creates chyme)
2. Pepsin, a protein-digesting enzyme, breaks proteins into amino acid components
3. Pepsin works best in acidic environments, so gastric juice contains HCl
4. Gastric juice pH is 2

Question 8

Describe the interior surface of the stomach.

Answer 8

Highly folded and pitted; pits lead to gastric glands

Question 9

What are the 3 types of cells in gastric glands?

Answer 9

1. Mucous cells
2. Chief cells
3. Parietal cells

Question 10

What is the function of mucous cells?

Answer 10

Release mucous to lubricate and protect stomach lining

Question 11

What is the function of chief cells?

Answer 11

Secrete pepsinogen, an inactive form of the enzyme pepsin

Question 12

What is the function of parietal cells?

Answer 12

To produce the components of HCl

Question 13

What is the function of the mucous layer?

Answer 13

Protect the stomach lining from being damaged by stomach acids. Stomach cells renew every 3 days to ensure this.

Question 14

What are some facts about physical digestion in the stomach? (2)

Answer 14

1. Stomach muscle contractions every 20s help mix contents and enzymes
2. It takes 2-6 hours for a meal to pass through the stomach

Question 15

When does the lower esophageal sphincter open?

Answer 15

When a bolus arrives from the oral cavity

Question 16

What causes heartburn and acid reflux?

Answer 16

Backflow of chyme into the lower esophagus

Question 17

What is the function of the pyloric sphincter?

Answer 17

To release chyme into the small intestine; Does so in single squirts

Question 18

What happens in the duodenum?

Answer 18

Chyme from the stomach mixes with digestive juices from the pancrease, liver, and gall blander, and with gland cells from the intestine itself.

Question 19

What happens in the Ileum and jejunum?

Answer 19

Nutrients and water are absorbed

Question 20

What are the associates of the small intestine?

Answer 20

1. The liver
2. The gall bladder
3. The pancreas

Question 21

What are the functions of the pancreas? (3)

Answer 21

1. Secrete alkaline solution to neutralize chyme acidity
2. Release enzymes to help digest carbs, proteins, nucleic acids, and fats
3. Plays a role in the endocrine system

Question 22

What are the functions of the liver? (2)

Answer 22

1. Produce bile that is used in fat and lipid digestion
2. Filter out toxins and convert molecules as needed

Question 23

What is the function of the gallbladder

Answer 23

Bile storage

Question 24

What helps increase the surface area of the small intestine?

Answer 24

Villi

With them, the small intestine’s surface area is 300m^2

Question 25

What are the two types of transport in small intestine absorption?

Answer 25

1. Active (amino acids, peptides, vitamins) 2. Passive (fructose)

Question 26

What is the function of the hepatic portal vein?

Answer 26

Carrying nutrient-rich blood from villi to liver

Question 27

What is the transport path in the small intestine?

Answer 27

Villi -> Capillaries -> Hepatic portal vein -> Liver -> Rest of body ## Footnote Triglycerides follow a different path

Question 28

What happens in the small intestine lumen?

Answer 28

* Bile breaks fat into droplets * Droplets are made of triglycerides, which as droplets get smaller, are easier exposed to hydrolysis * Lipase breaks down exposed triglycerides into fatty acids and monoglycerides (Enzymatic hydrolysis)

Question 29

What happens to monoglycerides and fatty acids once they leave the lumen?

Answer 29

* They diffuse into epithelial cells of small intestine, reforming into triglycerides * These incorporate into chylomicrons * Chylomicrons leave epithelial cells by exocytosis and enter lacteals, getting carried away by lymph into large veins

Question 30

What makes chylomicrons water soluble?

Answer 30

Their formation involves phospholipids and proteins forming a surface on the molecule

Question 31

What is included in the large intestine? (3)

Answer 31

1. Colon 2. Cecum 3. Rectum ## Footnote The colon is 1.5 metres long

Question 32

What is the function of the colon?

Answer 32

Reabsorption of water through osmosis (~6.3L per day)

Question 33

What is the function of the cecum?

Answer 33

Fermentation of ingested materials in animals. Vestigial in humans.

Question 34

Describe the process of human waste formation and elimination.

Answer 34

* Waste forms as feces in colon * 12-24 hours later, it passes along colon into the rectum * Feces is stored there til it can be eliminated

Question 35

What are the mammalian accessory glands?

Answer 35

1. Salivary gland 2. Pancreas 3. Liver 4. Gallbladder

Question 36

What are the 4 parts of the human digestive system?

Answer 36

1. Oral cavity, pharynx, and esophagus 2. Stomach 3. Small intestine 4. Large intestine ## Footnote The small intestine is 6 meters long