Chapter 17: The Digestive System

What is absorption?

Absorption is the movement of digested nutrients into the circulation.

What is an enzyme?

An enzyme is a catalyst that speeds the rate of a chemical reaction but is not used up in the reaction.

Why does food have to be digested before cells can use it?

Food must be broken down by digestion into particles small enough to pass through the plasma membrane of cells.

Name the two monosaccharide components of sucrose.

Glucose and fructose are the two monosaccharide components of sucrose.

What is the difference between hunger and appetite?

Hunger is the desire for food that can be satisfied by the ingestion of a filling meal. Appetite is a desire for food that is unrelated to a need for food.

What process means "spitting by means of water," as in digestion?

Hydrolysis means "splitting by means of water" as in digestion.

How does the small intestine function in the digestive process?

Most digestion takes place in the small intestine under the effects of digestive juices from the small intestine and the accessory organs. Most absorption of digested food and water also occurs in the small intestines.

Which form of motility occurs in the esophagus? In the small intestine?

Peristalsis occurs in the esophagus. Segmentation occurs in the small intestine.

Which type of motility would be most useful in the esophagus where the contents should move quickly?

Peristalsis to move food rapidly is most useful in the esophagus.

What type of food is digested in the stomach?

Proteins are digested in the stomach.

What type of tissue is between the submucosa and the serous membrane in the digestive tract wall?

Smooth muscle (circular and longitudinal) is between the submucosa and the serous membrane in the digestive tract wall.

Into which part of the small intestine do these accessory organs secrete?

The accessory organs shown secrete into the duodenum.

What is the common name for the gingiva?

The common name for the gingiva is the gum.

What are the four layers of the digestive tract wall?

The digestive tract typically has a wall composed of a mucous membrane (mucosa), a submucosa, smooth muscle (muscularis externa), and a serous membrane (serosa).

What are the three divisions of the small intestine?

The duodenum, jejunum, and ileum are the three divisions of the small intestine.

What is the role of the gallbladder?

The gallbladder stores bile and contracts to release it into the duodenum.

Which portions of the small and large intestines join at the ileocecal valve?

The ileum of the small intestine joins the cecum of the large intestine at the ileocecal valve.

What are the functions of the large intestine?

The large intestine reabsorbs some water and stores, forms, and eliminates the stool. It also houses bacteria that provide some vitamins.

Which accessory organ secretes bile, and what is the function of bile in digestion?

The liver secretes bile, which emulsifies fats, that is, breaks it down into small particles.

Which part of the peritoneum is around the small intestine?

The mesentery is the part of the peritoneum around the small intestine.

Which additional muscle layer in in the wall of the stomach that is not found in the rest of the digestive tract?

The oblique muscle layer is an additional muscle layer in the stomach that is not found in the rest of the digestive tract.

Which organ produces the most complete digestive secretions?

The pancreas produces the most complete digestive secretions.

What accessory organ secretes sodium bicarbonate, and what is the function of this substance in digestion?

The pancreas secretes sodium bicarbonate, which neutralizes the acidic chyme from the stomach.

What is the name of the large serous membrane that lines the abdominopelvic cavity and covers the organs it contains?

The peritoneum is the large serous membrane that lines the abdominopelvic cavity and covers the organs it contains.

Which accessory organs of digestion secrete into the mouth?

The salivary glands are the accessory organs that secrete into the mouth.

What are the names and locations of the salivary glands?

The salivary glands are the parotid, anterior and inferior to the ear; submandibular (submaxillary), near the body of the lower jaw; and sublingual, under the tongue.

Which salivary glands are directly below the tongue?

The sublingual salivary glands are directly below the tongue.

What are the two types of control over the digestive process?

The two types of control over the digestive process are nervous control and hormonal control.

Mastication

act of chewing

Defecation

act of eliminating undigested waste from the digestive tract

Deglutition

act of swallowing

Segmentation

alternating contraction and relaxation of the circular muscle in the small intestine's wall that mix its contents with digestive juices and move them through the organ

Mesentery

connective tissue membrane that attaches the small intestine to the dorsal abdominal wall

Duodenum

first portion of the small intestine

Ingestion

intake of food

Liver

large organ inferior to the diaphragm in the superior right abdomen; has many functions, including bile secretion, detoxification, storage, and interconversion of nutrients

Pancreas

large, elongated gland behind the stomach; produces digestive enzymes and hormones

Lacteal

lymphatic capillary that drains digested fats from the villi of the small intestine

Chyle

milky-appearing fluid absorbed into the lymphatic system from the small intestine. It consists of lymph and droplets of digested fat

Chyme

mixture of partially digested food, water, and digestive juices that forms in the stomach

Sphincter

muscular ring that regulates the size of an opening

Gallbladder

muscular sac on the inferior surface of the liver that stores bile

Esophagus

muscular tube that carries food from the throat to the stomach

Intestine

organ of the digestive tract between the stomach and the anus, consisting of the small and large intestines

Stomach

organ of the digestive tract that stores food, mixes it with digestive juices, and moves it into the small intestine

Digestion

process of breaking down food into absorbable particles

Saliva

secretion of the salivary glands; moistens food and contains an enzyme that digests starch

Peritoneum

serous membrane that lines the abdominal cavity and forms the outer layer of the abdominal organs; forms supporting ligaments for some organs

Villi

small, finger-like projections from the surface of a membrane; projections in the lining of the small intestine through which digested food is absorbed

Hydrolysis

splitting of large molecules by the addition of water, as in digestion

Gastric Inhibitory Peptide (GIP)

stimulates insulin release from pancreas when glucose enters duodenum; inhibits release of gastric juice (duodenum)

Cholecystokinin (CCK)

stimulates release of digestive enzymes from pancreas; stimulates release of bile from gallbladder; inhibits the stomach

Gastrin

stimulates release of gastric juices in the stomach

Secretin

stimulates release of water and bicarbonate from pancreas; inhibits the stomach

Bile

substance produced in the liver that emulsifies fats

Absorption

the process of taking up or assimilating a substance

Emulsify

to break up fats into small particles

Peristalsis

wavelike movements in the wall of an organ or duct that propel its contents forward