Chapter 15 The Digestive System

Where are carbohydrates digested? Proteins? Fats?

The primary site for digestion of carbohydrates, proteins, and fats is the small intestine. Carbohydrate digestion begins in the mouth, and protein digestion begins in the stomach.

Describe how food is processed in the mouth. What are the functions of the teeth and tongue?

The processing of food begins in the mouth, where food is mechanically broken down by the teeth. Saliva contains the enzyme salivary amylase, which begins the chemical breakdown of starch. The tongue functions in keeping the food in the mouth and then swallowing the food.

Why are so few substances absorbed from the stomach?

Very few foods are absorbed from the stomach because food is not digested sufficiently.

The most important function of the stomach is?

storage of food.

What is the function of the Salivary Glands in digestion?

3 pairs of glands that secrete saliva, Saliva moistens food & Enzyme (amylase) in saliva begins starch digestion

What is obesity?

A BMI greater than 30.

What is the function of the Serosa in the GI tract?

A connective tissue covering that secretes a fluid to lubricate the outside of the GI tract.

What is the function of the Submucosa in the GI tract?

A layer of connective tissue that contains blood vessels, lymph vessels, and nerves.

What is the function of the Mucosa in the GI tract?

A mucous membrane that lines the GI tract and secretes mucus that lubricates and protects the GI trac

How does bile assist in the digestion and absorption of fats?

Bile assists in the digestion of fats by coating small fat droplets created by mechanical digestion in the small intestine. This bile coating keeps the fat in small droplets (emulsifies it), which creates a larger surface area for lipase, a water-soluble enzyme, to chemically digest the fat into glycerol and fatty acids. Bile salts then combine with the glycerol and fatty acids to form micelles, which can be absorbed.

What is the function of the Cecum in digestion?

Blind pouch at junction of small and large intestines

What are the functions of the digestive system?

Breaks complex organic molecules in food into smaller subunits that can be absorbed into the bloodstream for delivery to cells.

What is the function of the epiglottis? Where is it located?

Causes a cartilaginous flap to move covering the opening to the airways of the respiratory system & its located in the larynx.

What is the function of the mouth in digestion?

Entrance to digestive system, Teeth chew food & Tongue positions and tastes food

What is the function of the Pancreas in digestion?

Gland located behind stomach, Secretes enzymes that digest all major nutrients, Secretes buffers that neutralize HCl from stomach & Releases secretions into small intestine

Discuss appendicitis.

Inflammation of the appendix & its caused by an infection that arises in the appendix after it becomes blocked by a piece of hardened stool from the cecum, food, or a tumor.

What is the function of the Stomach in digestion?

J-shaped muscular sac, Stores food, Secretes gastric juice(pepsin and HCl), Mixes food with gastric juice & Protein digestion begins

What is the function of the Liver in digestion?

Large organ in abdominal cavity, Secretes bile, which emulsifies fats & Plays role in processing and storing certain nutrients

What is the function of the Small Intestine in digestion?

Long, muscular tube, Mixes food with bile and with intestinal and pancreatic enzymes, Digests most nutrients & Absorbs most nutrients and water

What is the function of the Muscular in the GI tract?

Made up of two layers of smooth muscle—one circular and one longitudinal.

What types of digestion occurs in the mouth?

Mechanical Digestion.

What are the organs and accessory organs of GI tract?

Mouth, salivary glands, pharynx, esophagus, liver, stomach, gallbladder, pancreas, small intestine, colon, cecum, rectum, anal canal, anus

What is the function of the Esophagus in digestion?

Muscular tube & Moves food from pharynx to stomach

What is the function of the Colon in digestion?

Muscular tube, Absorbs water and some nutrients & Stores waste materials(feces)

What is the function of the Anus in digestion?

Opening at end of system & Expels feces

What is the function of the Pharynx in digestion?

Passageway for food (and air) & Plays a role in swallowing

What is the function of the Rectum in digestion?

Region of large intestine, Passageway for feces & Stretching of wall stimulates the defecation reflex

What is the function of the Anal Canal in digestion?

Regulates defecation

What is the function of the Gallbladder in digestion?

Small sac, Stores bile & Releases bile into small intestine

What are the functions of the large intestine?

The functions of the large intestine are to absorb water and store feces for removal from the body

What are the three primary functions of the stomach? What are the functions of gastric juice?

The functions of the stomach are food storage, mechanical digestion, and chemical digestion. Gastric juice contains hydrochloric acid and pepsin, which begin the digestion of proteins.

Describe the neural or hormonal mechanisms that regulate the release of digestive juices from each structure involved in digestion.

The sight, thought, or smell of food cause neu- ral reflexes that stimulate the salivary glands to secrete salivary amylase. Chewing causes a neural influence that causes the stomach to produce gas- tric juice. The distention of the stomach by food and the partial digestion of protein cause the stom- ach to release the hormone gastrin, which circulates in the bloodstream and stimulates the stomach to produce gastric juices. Acidic chyme entering the small intestine triggers the release of the hormone secretin from the small intestine that causes the pancreas to release bicarbonate. Acidic chyme also causes the small intestine to release cholecystokinin, which causes the gallbladder to release bile and the pancreas to release digestive enzymes.

Which structures produce the digestive enzymes that act in the small intestine?

The small intestine and pancreas produce enzymes that act in the small intestine.

Describe the structural features that increase the surface area for absorption in the small intestine.

The small intestine has many structures that increase the surface area for absorption. It has accordion-like folds (circular folds). The surface of the lining of the small intestine also has many fingerlike projections called villi. Each villus is covered with microvilli. The combined effect greatly increases the surface area for absorption.

Describe the structures of a tooth that are involved in tooth decay. What causes tooth decay?

The tooth is a hard structure covered by enamel. The inner portion is called dentin and surrounds the pulp. In the center there is a pulp cavity that houses blood vessels and nerves—structures that keep the tooth alive. Tooth decay is the destruction of the enamel coating of the tooth by acids produced by bacteria in the mouth. The result is a cavity.

Why is obesity dangerous?

They are many health risks associated with obesity such as disease of the heart and blood vessel, high cholesterol & other diseases.

What is the hormone produced by the small intestine that causes the gallbladder to contract and release bile.

cholecystokinin

What is a liquid mixture of food and gastric juices found in the stomach.?

chyme

What anorexia?

deliberate self-starvation.

The villi in the wall of the small intestine function to.?

increase the surface area for absorption

The is the organ that produces bile.

liver

List the structures of the GI tract, in the order that food passes through them.

mouth - esophagus - stomach - small intestine - large intestine - colon - rectum

It is possible to swallow while standing on one's hands because ?

peristalsis pushes food along the digestive tract in the right direction.

You go out with your friends to celebrate your birthday and share a sausage pizza. The digestion of the oil begins in the?

small intestine.

Saliva contains an enzyme that begins the chemical digestion of.

starch

Describe the defecation reflex.

the feces are pushed into the rectum, stretching the rectal wall and initiating it. Nerve impulses from the stretch receptors in the rectal wall travel to the spinal cord, which sends motor impulses back to the rectal wall, stimulating muscles there to contract and propel the feces into the anal canal. Two rings of muscles, called sphincters, must relax to allow defecation, the expulsion of feces. The internal sphincter relaxes auto- matically as part of the defecation reflex.

What are the layers of the GI tract? What is their function?

the mucosa, the submucosa, the muscularis, and the serosa.