Digestive System

Question 1

Mechanical Digestion

Answer 1

Mechanical digestion is the physical breakdown of chunks of food into smaller pieces, and it takes place mainly in the mouth and stomach.

Question 2

Chemical Digestion

Answer 2

Chemical digestion is the chemical breakdown of large, complex food molecules into smaller, simpler nutrient molecules that can be absorbed by body fluids (blood or lymph). This type of digestion begins in the mouth and continues in the stomach, but occurs mainly in the small intestine.

Question 3

Absorption

Answer 3

Absorption is the process in which substances pass into the bloodstream or lymph system to circulate throughout the body. Absorption of nutrients occurs mainly in the small intestine. Any remaining matter from food that is not digested and absorbed passes out of the body through the anus in the process of elimination.

Question 4

Gastrointestinal Tract

Answer 4

The gastrointestinal (GI) tract is basically a long, continuous tube that connects the mouth with the anus. If it were fully extended, it would be about 9 meters (30 feet) long in adults. It includes the mouth, pharynx, esophagus, stomach, and small and large intestines.

Question 5

Peristalsis

Answer 5

The muscles in the walls of GI tract organs enable peristalsis. Peristalsis is a continuous sequence of involuntary muscle contraction and relaxation that moves rapidly along an organ like a wave, similar to the way a wave moves through a spring toy. Peristalsis in organs of the GI tract propels food through the tract.

Question 6

Pharynx

Answer 6

A lump of swallowed food is called a bolus. The bolus passes from the mouth into the pharynx, and from the pharynx into the esophagus.

Question 7

Esophagus

Answer 7

The bolus passes from the mouth into the pharynx, and from the pharynx into the esophagus. The esophagus is a long, narrow tube that carries food from the pharynx to the stomach. It has no other digestive functions.

Question 8

Stomach

Answer 8

From the esophagus, food passes into the stomach, where both mechanical and chemical digestion continue.

Question 9

Small Intestine

Answer 9

The small intestine is a narrow, but very long tubular organ. It may be almost 7 meters (23 feet) long in adults. It is the site of most chemical digestion and virtually all absorption of nutrients.

Question 10

Villi

Answer 10

Much of the inner lining of the small intestine is covered by tiny finger-like projections called villi, each of which is covered by even tinier projections called microvilli and greatly increase the surface area through which nutrients can be absorbed from the small intestine.

Question 11

Large Intestine

Answer 11

From the small intestine, any remaining nutrients and food waste pass into the large intestine. The large intestine is another tubular organ, but it is wider and shorter than the small intestine. It connects the small intestine and the anus.

Question 12

Liver

Answer 12

The liver is an organ with multitude of functions. Its main digestive function is producing and secreting a fluid called bile, which reaches the small intestine through a duct. Bile breaks down large globules of lipids into smaller ones that are easier for enzymes to chemically digest.

Question 13

Gallbladder

Answer 13

The gallbladder is a small sac below the liver that stores some of the bile from the liver. The gallbladder also concentrates the bile by removing some of the water from it. It then secretes the concentrated bile into the small intestine as needed for fat digestion following a meal.

Question 14

Pancreas

Answer 14

The pancreas secretes many digestive enzymes, and releases them into the small intestine for the chemical digestion of carbohydrates, proteins, and lipids. The pancreas also helps lessen the acidity of the small intestine by secreting bicarbonate, a basic substance that neutralizes acid.

Question 15

Salivary Glands

Answer 15

The mouth contains three pairs of major salivary glands. These three pairs are all exocrine glands that secrete saliva into the mouth through ducts.
The largest of the three major pairs of salivary glands are the parotid glands, which are located on either side of the mouth in front of the ears.
The next largest pair is the submandibular glands, located beneath the lower jaw.
The third pair is the sublingual glands, located underneath the tongue.

Question 16

Sphincters

Answer 16

When food is not being swallowed, the esophagus is closed at both ends by upper and lower esophageal sphincters. Sphincters are rings of muscle that can contract to close off openings between structures. The upper esophageal sphincter is triggered to relax and open by the act of swallowing, allowing a bolus of food to enter the esophagus from the pharynx. Then, the esophageal sphincter closes again to prevent food from moving back into the pharynx from the esophagus.

Question 17

Appendix

Answer 17

The cecum of the colon that is known as the appendix. The function of the appendix is uncertain, but it does not seem to be involved in digestion or absorption. It may play a role in immunity, and in the fetus, it seems to have an endocrine function, releasing hormones needed for homeostasis.