Module 3 Digestive System

Question 1

Name the two main divisions of the digestive system organs.

Answer 1

The human digestive organs can be divided into those of the alimentary canal and the accessory digestive organs.

Question 2

Name the seven parts of the gastrointestinal tract.

Answer 2

The gastrointestinal tract is composed of the mouth, pharynx, esophagus, stomach, small intestine, large intestine, and anus.

Question 3

Name the six digestive system accessory organs.

Answer 3

The accessory organs are the teeth, tongue, gallbladder, salivary glands, liver and pancreas.

Question 4

List the two bones and the membrane to which the tongue is attached.

Answer 4

The tongue is attached to the hyoid bone and the mandible and the membranous lingual frenulum.

Question 5

How many teeth are there in an adult human and what do they do?

Answer 5

There are thirty-two teeth in the human mouth. Together they work to tear, crush and grind food to mechanically digest food.

Question 6

What are the four types of teeth, how many of each type are there and what does each type do?

Answer 6

The teeth are composed of two chisel-shaped incisors for biting; one pointed canine for tearing; two fairly flat pre-molars for grinding; and three flat molars for crushing.

Question 7

What is the specific function of the salivary gland in the process of digestion?

Answer 7

Food is mixed and moistened with saliva (from the salivary glands) containing enzymes that begin the process of chemical digestion by breaking down starches.

Question 8

Where are taste buds located?

Answer 8

Taste buds are found primarily on the tongue but also on the surface of the mouth and the wall of the pharynx.

Question 9

Describe the function of the tongue in the digestive process.

Answer 9

The tongue grips the food, constantly repositions it between the teeth and forms it into a compact mass which is pushed back to the pharynx to begin the process of swallowing.

Question 10

What is a bolus?

Answer 10

A bolus is the compact mass of food formed by the combination of chewing by the teeth and repositioning by the tongue.

Question 11

List the 3 parts of the pharynx.

Answer 11

The pharynx is made up of three parts: the nasopharynx, the oropharynx, and the laryngopharynx.

Question 12

Through what sections of the pharynx does air travel? Through what sections of the pharynx does food travel?

Answer 12

Air enters the nose, continues through the nasopharynx, oropharynx and the laryngopharynx. Air then enters the trachea on its way to the lungs. Food and liquid enter the mouth, continue through the oropharynx and the laryngopharynx but then continue into the esophagus.

Question 13

What prevents food from entering the lungs and why is this necessary?

Answer 13

Food is prevented from entering the larynx by the epiglottis, a flap of elastic cartilage which covers the larynx when swallowing food or liquid.

Question 14

Describe how the muscular layers in the pharynx assist with food passage.

Answer 14

The pharynx has two types of skeletal muscles; a circumferential outer layer and an inner longitudinal layer which contract alternatively squeezing food into the esophagus.

Question 15

List and describe the tissue layers of the esophagus.

Answer 15

The esophagus contains 4 layers of tissue: the innermost layer is the mucosa which secretes mucus into the interior the gastrointestinal tract, the second layer is the submucosa which contains blood and lymph vessels, lymph nodes, nerves, and mucous glands, the third layer is the muscularis externa which is made of two layers of muscle: the outer longitudinal fibers and inner circumferential fibers and the outermost layer is the serosa which is made up of cells that make serous fluid.

Question 16

Explain peristalsis.

Answer 16

Peristalsis is the squeezing of food through the GI tract by the alternating contraction of the sets of longitudinal and circumferential muscles.

Question 17

What are the three main divisions of a tooth?

Answer 17

Each tooth is made of three main parts: the crown, the neck and the root.

Question 18

What are the three types of papillae on the tongue? Which ones contain taste buds?

Answer 18

There are three types of papillae which help to grip food on the tongue: circumvallate, fungiform and filiform. Circumvallate and fungiform papillae both contain taste buds.

Question 19

Describe the shape of the stomach and its location relative to the abdomen and diaphragm.

Answer 19

The stomach is a backward C shaped organ that is located along the left side of the abdomen below the diaphragm.

Question 20

Describe the passage of food into and out of the stomach.

Answer 20

Food enters the stomach from the esophagus via the cardioesophageal sphincter and exits the stomach via the pyloric sphincter into the small intestine.

Question 21

Describe the lesser curvature and the greater curvature.

Answer 21

The stomach has two curvatures: the concave lesser curvature which extends inward on the shorter side of the stomach and the convex greater curvature which extends outward on the longer side of the stomach.

Question 22

Describe the lesser omentum and the greater omentum.

Answer 22

The lesser omentum is a serous membrane which attaches the lesser curvature of the stomach to the liver and the greater omentum is a serous membrane which attaches the greater curvature of the stomach to the posterior wall of the body.

Question 23

List and describe the two functions of the stomach.

Answer 23

The stomach has two purposes. It is a temporary storage area for food, storing up to two liters of partially digested food. The muscular walls of the stomach contract vigorously and mix food with juices that are secreted whenever food enters the stomach, allowing food to be broken down into smaller pieces that are easier to digest.

Question 24

The pH of stomach is 1.3 - 3.5. What is this due to and what is its source and function?

Answer 24

The 1.3-3.5 pH of stomach contents is due to hydrochloric acid secreted by the parietal cells. The high acidity level kills bacteria and converts the inactive pepsinogen into the active enzyme pepsin.

Question 25

What is the source of the stomach enzyme pepsin and what is its function?

Answer 25

Inactive pepsinogen is secreted by the chief cells and converted into the active enzyme pepsin by HCl. Pepsin then begins the breakdown of proteins.

Question 26

What is a stomach ulcer?

Answer 26

A stomach ulcer is an open sore in the wall of the stomach.

Question 27

Explain in detail how the stomach contents enter the small intestine.

Answer 27

The pyloric sphincter valve, located at the base of the stomach, relaxes causing a small quantity of chyme to pass through the opening into the first part of the small intestine. This initiates a reflex that causes the muscles of the sphincter to contract and close the opening temporarily. Then the sphincter relaxes again and allows more chyme to enter.

Question 28

List the 3 sections of the small intestine. Which section is the shortest?

Answer 28

The first and shortest section of the small intestine is the duodenum. Second section is the jejunum and third is the ileum.

Question 29

What are the names of the valves which are located at the beginning and end of the small intestine?

Answer 29

The small intestine runs from the pyloric sphincter at the end of the stomach to the ileocecal valve at the large intestine.

Question 30

List the names of the 3 specialized structures in the wall of the small intestine.

Answer 30

The 3 specialized structures in the small intestine are circular folds, villi and microvilli.

Question 31

Where is bile formed and stored?

Answer 31

Bile is formed in the liver which is stored in the gallbladder.

Question 32

Describe in detail the 2 major functions of pancreatic juice.

Answer 32

Pancreatic juice contains sodium bicarbonate, which neutralizes the chyme and makes the pH of the small intestine slightly basic. Pancreatic juice also contains digestive enzymes that further digest every major component of food.

Question 33

Describe how fats, sugars and amino acids are absorbed by the small intestine.

Answer 33

Each small intestinal villus contains blood vessels and a lacteal lymphatic vessel. Sugars and amino acids enter villi cells and then are absorbed into the bloodstream. Glycerol and fatty acids enter villi cells and are reassembled into fat molecules, which move into the lacteals.

Question 34

What are the 3 functions of the liver that are important in digestion?

Answer 34

The 3 functions of the liver important in digestion are (1) it produces bile, which is stored in the gallbladder before entering the small intestine, where it emulsifies fats, (2) it stores glucose as glycogen and breaks down glycogen to glucose between meals to maintain a constant glucose concentration (homeostasis) in the blood, and (3) it produces urea from amino groups that are removed from excess amino acids.

Question 35

List the 8 regions of the large intestine.

Answer 35

(1) Cecum, (2) appendix, (3) ascending colon, (4) transverse colon, (5) descending colon, (6) sigmoid colon, (7) rectum, (8) anal canal.

Question 36

What are the two sphincters of the anal canal?

Answer 36

The anal canal has an involuntary smooth muscle internal sphincter and a voluntary skeletal muscle external sphincter.

Question 37

List 4 functions of the large intestine.

Answer 37

The large intestine propel wastes, reabsorbs water, reabsorbs electrolytes and absorbs Vitamin K and certain B vitamins produced by intestinal bacteria.

Question 38

What are the 2 major physiological problems caused by diarrhea?

Answer 38

When materials pass through the colon too quickly, excess water is not reabsorbed, and diarrhea will result, which can lead to serious dehydration and electrolyte loss.

Question 39

List the content of feces.

Answer 39

Feces are about 75% water and 25% solid matter containing intestinal bacteria, undigested plant material, fats, bile pigments, inorganic material, mucus, and dead intestinal cells.

Question 40

Name the 4 main functions performed by the digestive system.

Answer 40

The digestive system has four main roles that it performs: ingestion, digestion (both mechanical and chemical), absorption, and defecation.

Question 41

What digestive system functions are carried out by the mouth?

Answer 41

Ingestion and Digestion.

Question 42

Explain which digestive system functions are carried out by the stomach.

Answer 42

In the stomach mechanical digestion continues as muscles churn and mix the food, breaking it into smaller pieces in the form of chime which is moved to the small intestine by peristalsis. Chemical digestion continues as pepsin digests proteins.

Question 43

Explain which digestive system functions are carried out by the small intestine.

Answer 43

In the small intestine chemical digestion continues as enzymes from the pancreatic juices break down starches and proteins, and begin digestion of fat. Mechanical digestion continues as bile breaks down fat into smaller pieces. Absorption begins as digested food molecules, water and fat are absorbed into the bloodstream.

Question 44

Explain the two main hormones that are responsible for hunger and satiety.

Answer 44

Leptin and Ghrelin. Leptin is produced by adipose tissue (fat cells). The role of leptin is to alert the brain to turn off the hunger center in the brain and activate the satiety center when consuming a meal. Ghrelin is produced by the stomach and has the opposite role. Ghrelin travels to the brain and stimulates the hunger center as it deactivates the satiety center. Ideally, leptin and ghrelin work together to balance hunger and satiety.

Question 45

List the 5 biochemical materials needed by the body that are found in food.

Answer 45

Carbohydrates, proteins, and lipids are the major biochemical substances found in food needed by the body in large amounts. Vitamins and minerals are also needed in a much smaller amount.

Question 46

What are the 2 classes of carbohydrates and in what foods can each be found?

Answer 46

Carbohydrates are classified as starches and sugars. Milk and fruits such as apples or peaches contain sugar, while grains such as wheat and vegetables such as potatoes contain starches.

Question 47

What are the 3 classes of lipids?

Answer 47

Lipids can be divided into three categories: saturated fat, unsaturated fat, and cholesterol.

Question 48

What are the 2 classes of proteins and in what foods can each be found?

Answer 48

Proteins can be categorized as complete or incomplete proteins. Examples of complete proteins are meat, poultry, eggs, milk or dairy products, and soybeans; whereas, examples of incomplete proteins are grains, legumes, seeds, and nuts.

Question 49

What is the definition of an essential amino acid, how many essential amino acids are there for adults and where can they be found?

Answer 49

There are nine amino acids called essential amino acids required in an adult human diet since the body is unable to make these amino acids. Complete proteins contain all nine essential amino acids.

Question 50

What are the 2 classes of vitamins? How is a vitamin different than a carbohydrate, lipid or protein? Why can ingestion of excessive amounts of one type of vitamin be dangerous?

Answer 50

The 2 classes of vitamins are water-soluble vitamins and fat-soluble vitamins. Vitamins are organic compounds that are not consumed in metabolic reaction but help enzymes carry out the metabolic reactions which convert nutrients to materials need by the body. Fat-soluble vitamins are stored in body fat and ingestion of excessive amounts can be problematic.

Question 51

List 2 ways in which minerals are different than carbohydrates, lipids and proteins. List the seven minerals needed in the human diet and four foods which are good sources of these.

Answer 51

Minerals are inorganic compounds (not organic like carbohydrates, lipids and proteins) and are not used as fuel in metabolic reactions. Humans need the following seven minerals in their diets: calcium, chloride, magnesium, phosphorus, potassium, sodium, and sulfur. Foods such as milk, some meats, legumes and vegetables are the best sources of minerals.

Question 52

Define anabolism.

Answer 52

Anabolism is the set of reactions in which smaller molecules are combined to make larger molecules.

Question 53

How is the energy released from the breakdown of glucose used by the body?

Answer 53

The energy released during the breakdown of glucose is used by the body to add a phosphate to an adenosine diphosphate (ADP) molecule and make adenosine triphosphate (ATP).

Question 54

Describe cellular respiration.

Answer 54

During cellular respiration, glucose combines with oxygen to form carbon dioxide, water, and ATP.

Question 55

Describe glycolysis.

Answer 55

In glycolysis glucose is broken down into two pyruvic acid molecules and two ATP molecules are formed.

Question 56

Describe the citric acid cycle (TCA cycle).

Answer 56

In the citric acid (TCA) cycle the pyruvic acid product of glycolysis is converted to carbon dioxide forming some additional ATP.

Question 57

Describe the electron transport chain.

Answer 57

In the electron transport chain hydrogen atoms formed during glycolysis and the TCA cycle are converted to water releasing energy which is used to add phosphate to ADP to form ATP.

Question 58

How is the energy released in the breakdown of glucose converted to a form usable by the cells?

Answer 58

The energy released in the breakdown of glucose allows the body to convert it into ATP.

Question 59

What occurs in the citric acid (TCA) cycle?

Answer 59

In the citric acid (TCA) cycle, the pyruvic acid product of glycolysis is converted to carbon dioxide, forming some additional ATP.

Question 60

Describe the electron transport chain.

Answer 60

In the electron transport chain, hydrogen atoms formed during glycolysis and the TCA cycle are converted to water, releasing energy which is used to add phosphate to ADP to form ATP.

Question 61

How is the energy released in the breakdown of glucose converted to a usable form?

Answer 61

The energy released in the breakdown of glucose allows the body to add a phosphate to an adenosine diphosphate (ADP) molecule and make adenosine triphosphate (ATP), which is then used by cells as a source of energy to perform cellular activities.

Question 62

How does the energy formed in fat catabolism compare to that formed in carbohydrate metabolism?

Answer 62

Lipid metabolism yields twice the energy formed during glucose metabolism.

Question 63

Where does lipid metabolism occur and what is the first stage of lipid breakdown?

Answer 63

Lipid metabolism occurs in the liver by a process known as beta-oxidation to form acetic acid, which is further catabolized by the TCA cycle to carbon dioxide, forming some ATP.

Question 64

Why are proteins not usually used as a body energy source and when are they used?

Answer 64

Proteins are the building blocks for the cells and are therefore preserved by the body, only being used to make ATP when carbohydrates and fats are unavailable to the body.

Question 65

What is the first step in the oxidation of an amino acid formed from a protein?

Answer 65

When proteins must be used to form ATP, the amino group is removed from the protein to form ammonia.

Question 66

How is ammonia removed from the body?

Answer 66

Ammonia is combined with carbon dioxide to make urea, which is excreted in the urine.