Components of the Digestive System

Question 1

List the different types of herbivores.

Answer 1

frugivores (fruit-eaters), granivores (seed eaters), nectivores (nectar feeders), and folivores (leaf eaters).

Question 2

Differentiate between obligate and facultative carnivores.

Answer 2

Obligate carnivores rely entirely on animal flesh to obtain their nutrients.
Facultative carnivores eat non-animal food in addition to animal food.

Question 3

What is the simplest type of digestive system?

Answer 3

Gastrovascular cavity

Question 4

What organisms use a gastrovascular cavity?

Answer 4

Platyhelminthes (flatworms), Ctenophora (comb jellies), and Cnidaria (coral, jellyfish, and sea anemones)

Question 5

How is a gastrovascular cavity set up?

Answer 5

a blind tube or cavity with only one opening, the “mouth”, which also serves as an “anus”.

Question 6

Outline digestion in a gastrovascular cavity.

Answer 6

Ingested material enters the mouth and passes through a hollow, tubular cavity. Cells within the cavity secrete digestive enzymes that break down the food. The food particles are engulfed by the cells lining the gastrovascular cavity.

Question 7

Explain the structure of an alimentary canal. What is an example of an organism with this type of digestive system?

Answer 7

consists of one tube with a mouth at one end and an anus at the other. Earthworms

Question 8

Outline the process of digestion in an alimentary canal.

Answer 8

Once the food is ingested through the mouth, it passes through the esophagus and is stored in an organ called the crop; then it passes into the gizzard where it is churned and digested. From the gizzard, the food passes through the intestine, the nutrients are absorbed, and the waste is eliminated as feces, called castings, through the anus.

Question 9

What does monogastric mean?

Answer 9

Stomach with only one chamber.

Question 10

Outline the general process of monogastric digestion.

Answer 10

The teeth play an important role in masticating (chewing) or physically breaking down food into smaller particles.
The enzymes present in saliva also begin to chemically break down food.
Using peristalsis, or wave-like smooth muscle contractions, the muscles of the esophagus push the food towards the stomach.
The gastric juices, which include enzymes in the stomach, act on the food particles and continue the process of digestion.
The further breakdown of food takes place in the small intestine where enzymes produced by the liver, the small intestine, and the pancreas continue the process of digestion.
The nutrients are absorbed into the bloodstream across the epithelial cells lining the walls of the small intestines.
The waste material travels on to the large intestine where water is absorbed and the drier waste material is compacted into feces; it is stored until it is excreted through the rectum.

Question 11

Explain how human and rabbit digestion differs.

Answer 11

(a) Humans and herbivores, such as the (b) rabbit, have a monogastric digestive system. However, in the rabbit, the small intestine and cecum are enlarged to allow more time to digest plant material. The enlarged organ provides more surface area for absorption of nutrients. Rabbits digest their food twice: the first time food passes through the digestive system, it collects in the cecum, and then it passes as soft feces called cecotrophes. The rabbit re-ingests these cecotrophes to further digest them.

Question 12

What special challenges do birds face with receving nutrients from food?

Answer 12

No teeth; system must be able to process unmasticated food.
High metabolic rates to efficiently process food and keep body weight low for flight.

Question 13

How many chambers do bird stomachs have? Name and describe them.

Answer 13

2: the proventriculus, where gastric juices are produced to digest the food before it enters the stomach, and the gizzard, where the food is stored, soaked, and mechanically ground.

Question 14

Where does most of the chemical digestion and absorption happen in birds?

Answer 14

Intestine

Question 15

How do birds expel waste?

Answer 15

Through cloaca.

Question 16

Name the three glands that secrete saliva.

Answer 16

the parotid, the submandibular, and the sublingual.

Question 17

What enzymes does saliva contain? What do they do?

Answer 17

Amylase begins process of converting starches into maltose.
Lipase begins breakdown of fats.

Question 18

What is the pH of the stomach?

Answer 18

1.5-2.5

Question 19

What is the major site of protein digestion?

Answer 19

Stomach

Question 20

What enzyme mediates protein digestion?

Answer 20

Pepsin

Question 21

Which cells secrete pepsin?

Answer 21

Chief cells

Question 22

How is HCl formed in the stomach? What does it do?

Answer 22

Another cell type—parietal cells—secrete hydrogen and chloride ions, which combine in the lumen to form hydrochloric acid, the primary acidic component of the stomach juices. Hydrochloric acid helps to convert the inactive pepsinogen to pepsin.

Question 23

What is chyme?

Answer 23

The partially digested food and gastric juice mixture in the stomach.

Question 24

What regulates the movement of chyme to the small intestine?

Answer 24

The pyloric sphincter.

Question 25

How is the stomach protected from pepsin?

Answer 25

First, as previously mentioned, the enzyme pepsin is synthesized in the inactive form. This protects the chief cells because pepsinogen does not have the same enzyme functionality of pepsin. Second, the stomach has a thick mucus lining that protects the underlying tissue from the action of the digestive juices.

Question 26

How do ulcers form?

Answer 26

When this mucus lining is ruptured, ulcers can form in the stomach. Ulcers are open wounds in or on an organ caused by bacteria (Helicobacter pylori) when the mucus lining is ruptured and fails to reform.

Question 27

What happens in the small intestine?

Answer 27

Digestion of protein, fats and carbs is completed.

Question 28

How is absorption efficiency increase in the small intestine?

Answer 28

The villi and microvilli, with their many folds, increase the surface area of the intestine and increase absorption efficiency of the nutrients.

Question 29

List the three parts of the human small intestine.

Answer 29

duodenum, the jejunum, and the ileum

Question 30

What happens in the duodenum?

Answer 30

In the duodenum, chyme is mixed with pancreatic juices in an alkaline solution rich in bicarbonate that neutralizes the acidity of chyme and acts as a buffer.
These digestive juices break down the food particles in the chyme into glucose, triglycerides, and amino acids.
Absorption of fatty acids also takes place in the duodenum.

Question 31

Where is bile produced? Where is it stored?

Answer 31

Produced in liver, stored in gallbladder.

Question 32

What occurs in the jejunum?

Answer 32

hydrolysis of nutrients is continued while most of the carbohydrates and amino acids are absorbed through the intestinal lining. The bulk of chemical digestion and nutrient absorption occurs in the jejunum.

Question 33

What occurs in the ileum?

Answer 33

bile salts and vitamins are absorbed into bloodstream. The undigested food is sent to the colon from the ileum via peristaltic movements of the muscle.

Question 34

What occurs in the large intestine?

Answer 34

reabsorbs the water from the undigested food material and processes the waste material

Question 35

List the three parts of the human large intestine.

Answer 35

the cecum, the colon, and the rectum

Question 36

What occurs in the cecum?

Answer 36

The cecum joins the ileum to the colon and is the receiving pouch for the waste matter.

Question 37

What is the primary role of the rectum?

Answer 37

store the feces until defecation

Question 38

How are feces propelled?

Answer 38

The feces are propelled using peristaltic movements during eliminationq

Question 39

Differentiate betweem the two sphincters that control elimination.

Answer 39

the inner sphincter is involuntary and the outer sphincter is voluntary.

Question 40

What are accessory organs? Give examples.

Answer 40

Accessory organs are organs that add secretions (enzymes) that catabolize food into nutrients. Accessory organs include salivary glands, the liver, the pancreas, and the gallbladder.

Question 41

What does the liver do?

Answer 41

The liver produces bile, a digestive juice that is required for the breakdown of fatty components of the food in the duodenum. The liver also processes the vitamins and fats and synthesizes many plasma proteins.

Question 42

What does the pancreas do?

Answer 42

The chyme produced from the stomach is highly acidic in nature; the pancreatic juices contain high levels of bicarbonate, an alkali that neutralizes the acidic chyme. Additionally, the pancreatic juices contain a large variety of enzymes that are required for the digestion of protein and carbohydrates.

Question 43

What does the gallbladder do?

Answer 43

The gallbladder is a small organ that aids the liver by storing bile and concentrating bile salts. When chyme containing fatty acids enters the duodenum, the bile is secreted from the gallbladder into the duodenum.