Digestive System

Question 1

Ingestion

Answer 1

The act of eating

Question 2

Digestion

Answer 2

The breaking down of food into molecules small enough for the body to absorb

Question 3

Absorption

Answer 3

The take-up of the products of digestion

Question 4

Elimination

Answer 4

The removal of undigested materials out of the digestive tract

Question 5

Alimentary canal

Answer 5

Consists of:

• A mouth
• An anus
• Specialized regions associated with one-way food flow

Question 6

Food flow

Answer 6

Food moves:

• Into the pharynx/throat
• down the esophagus
• Into the stomach, where food is ground and stored
• Into the intestines, where chemical digestion and nutrient absorption occur
• Undigested food comes out the anus

Question 7

Human digestion

Answer 7

In humans, food is:

• Ingested and chewed in the oral cavity (mouth)
• Pushed by the tongue into the pharynx
• Moved by contraction and relaxation (peristalsis) by smooth muscle
• Moved out of the stomach by sphincters
• The final steps of digestion and absorption occur in the small intestine
• Undigested food is moved through the large intestine, stored in the rectum, and expelled out the anus

Question 8

Oral cavity

Answer 8

Mechanical and chemical digestion begins in the mouth

Question 9

Chewing

Answer 9

Chewing cuts, smashes and grinds food, making it easier to swallow

Question 10

Tongue

Answer 10

The tongue tastes and shapes food into a ball called a bolus and moves it towards the pharynx

Question 11

Salivary glands

Answer 11

Release a slippery glycoprotein:

• Moistens and lubricates food for easier swallowing
• Buffers that neutralize acids
• Salivary amylase that begins the hydrolysis of starch
• Antibacterial agents that kill some bacteria injested with food

Question 12

Air moves

Answer 12

Air moves from the pharynx, into the larynx, past the vocal cords and into the lungs

Question 13

Swallowed food

Answer 13

• Moves from the pharynx into the esophagus and stomach

- During swallowing, the tip of the larynx moves upward, preventing food from entering the trachea

Question 14

The stomach

Answer 14

Can stretch and hold up to 2 liters of food and drink

Question 15

Chemical digestion

Answer 15

• Occurs in the stomach
• The stomach secretes gastric juice made up of mucus, a protein-digesting enzyme and a strong acid with a ph of about 2 that kills bacteria, breaks apart food cells, and denatures proteins
• Pepsinogen and HCl produce active pepsin
• Pepsinogen, H+, and Cl are secreted into the stomach
• HCl conversts some pesinogen to pepsin
• Pepsin helps active more pepsinogen, starting a chain reaction
• Pepsin begins the chemical digestion of proteins

Question 16

Protecting the stomach wall from gastric juices

Answer 16

• The secretion of pepsin in the inactive form of pepsinogen helps protect the cells of gastric glands
• Mucus helps protect the lining against HCl and pepsin
• New cells begin lining the stomach every 3 days, replacing damaged cells

Question 17

Acid reflux

Answer 17

-When chyme in the stomach backs into the esophagus causing heartburn, which can lead to GERD

Question 18

Ulcers

Answer 18

-Form in the stomach and duodenum from bacterial infections

Question 19

Small intestine

Answer 19

• Is named for its small diameter
• About 6 meters long
• The site of much chemical digestion
• Where the most nutrients are absorbed

Question 20

Duodenum

Answer 20

-The first 25 cm of the small intestine, where chyme squirted from the stomach is mixed with digestive juices from the pancreas, liver, gallbladder, and gland cells in the intestinal walls

Question 21

Pancreas

Answer 21

-Produces pancreatic juice containing a mixture of digestive enzymes and an alkaline solution rich in bicarbonate

Question 22

Liver

Answer 22

• The epithelial cells of the liver (called hepatocytes) produce bile, which is delivered to the gallbladder where it is stored until it is needed
• Bile is delivered to the gallbladder where it is stored
• Bile breaks fat into small droplets (emulsification) that are easier to attack

Question 23

Surface area of small intestine

Answer 23

The surface area of the small intestine is greatly increased by:

• Folds in the lining
• Fingerlike projections called villi
• Tiny projections on the surface of the intestinal cells called microvilli

Question 24

Epithelial cells

Answer 24

-Nutrients pass into epithelial cells by diffusion and against concentration gradients

Question 25

Fatty Acids

Answer 25

- Fatty acids and glycerol are recombined into fats - Coated with proteins - Transported into lymph vessels (lymphatic capillaries called lacteals)

Question 26

Amino acids

Answer 26

-Pass out of the intestinal epithelium, across the thin walls of the capillaries, into the blood, and finally into the liver

Question 27

Hepatic portal vein

Answer 27

-Blood from the digestive tract drains into the hepatic portal vein into the liver

Question 28

The liver

Answer 28

The liver performs many functions: - Converts glucose into glycogen - Stores glucose and releases sugars into the blood - Synthesizes many proteins including blood clotting and lipoproteins that transport fats and cholesterol to body cells - Mediates substances absorbed into the digestive tract into less toxic forms and makes bile

Question 29

Large intestine

Answer 29

- Also known as the colon - Is about 1.5 m long and 5 cm in diameter - Has a pouch called the cecum near its junction with the small intestine which bears the appendix - Contains large populations of E. coli, which produce important vitamins - Absorbs vitamins and water into the bloodstream - Helps form feces which are stored in the rectum until elimination

Question 30

Basic Nutritional Needs

Answer 30

- Must obtain fuel to power body activities - Organic molecules to build body molecules - Essential nutrients or substance that an animal can't make itself

Question 31

Cellular respiration

Answer 31

- Produces the body's energy currency, ATP, by oxidizing organic molecules digested from food and usually using carbohydrates or fats as fuel - A gram of fat has more than twice the calories than as carbs or proteins

Question 32

4 Classes of Essential Nutrients

Answer 32

- Essential fatty acids - Essential amino acids - Vitamins - Minerals

Question 33

Essential fatty acids

Answer 33

- Are used for making phospholipids of cell membranes | - Found in seeds, grains, and veggies

Question 34

Essential amino acids

Answer 34

- Used to make proteins | - Found in eggs, meat, and milk

Question 35

Vitamins

Answer 35

- Organic nutrients - May be water soluble (B or C) - May be fat soluble (A, D, E, or K)

Question 36

Vitamin A

Answer 36

-Needed for teeth and bones

Question 37

Vitamin B

Answer 37

-Needed for CNS and proper RBC function

Question 38

Vitamin C

Answer 38

-Helps immune system and absorbs iron

Question 39

Vitamin D

Answer 39

-Needed for proper absorption of Calcium in the gut

Question 40

Vitamin E

Answer 40

Antioxidant

Question 41

Vitamin K

Answer 41

-Needed for proper blood clotting

Question 42

Minerals

Answer 42

- Simple inorganic nutrients - Calcium and phosphorus are required in larger amounts - Iron is needed to make hemoglobin - Iodine makes thyroid hormones