Digestive System

Question 0

Mechanical digestion

Answer 0

• large pieces made smaller to prepare for chemical digestion
• happens in mouth & stomach

Question 1

5 functions of digestive system

Answer 1

• ingests food
• secretes enzymes & hormones
• digests food into macromolecules
• absorbs nutrients
• eliminates feces

Question 2

Chemical digestion

Answer 2

• enzymes break down macromolecules into small molecules that can be digested

Question 3

Mouth

Answer 3

• receives food
• teeth chew & break down food
• salivary glands send saliva into mouth to moisten food
• tongue mixes food with saliva & forms mixture into bolus

Question 4

Salivary glands

Answer 4

• sublingual glands: beneath tongue
• submaxillary glands: beneath lower jaw
• parotid glands: along side of jaw

Question 5

Pharynx

Answer 5

• receives air from nasal cavity & food from mouth
• tonsils embedded in its membranes
• food passes through pharynx to esophagus
• swallowing is a reflex action that occurs here
• soft palate moves back during swallowing to close nasopharynx
• epiglottis closes to prevent food from passing into trachea

Question 6

Esophagus

Answer 6

• muscular tube that passes through thoracic cavity & diaphragm
• carries food from pharynx to stomach
• bolus moves through by peristalsis (muscle contractions), which continues though entire digestive tract

Question 7

Stomach

Answer 7

• thick-walled j-shaped organ
• located on left side of body below diaphragm
• stores food & aids in digestion
• “gastric” refers to stomach
• 3 muscle layers churn & mix food with gastric juice (mechanical dig.)
• Chemical dig: gastric pits in stomach lining contain gastric glands -> produce gastric juice (enzymes & HCl)
• goblet cells in stomach lining secrete mucus to protect stomach
• food leaving stomach is chyme (thick, soupy liquid)

Question 8

Cardiac sphincter

Answer 8

• circular muscle that relaxes to allow food from esophagus into stomach
• contacts to prevent stomach acid from backing up into esophagus (if not working -> heartburn)

Question 9

Pyloric Sphincter

Answer 9

• relaxes to allow food from stomach into small intestine

- controls rate of stomach emptying

Question 10

Small Intestine

Answer 10

• smaller diameter than large int.
• 6m long
• specialized for digestion & absorption:
  
  • long length allows time for digestive enzymes to break down food into nutrients
  • long length allows time for nutrients to be absorbed, villi & microvilli increase surface area for absorption (tennis-court size!)

Question 11

3 sections of small intestine

Answer 11

• duodenum: 1st 25cm, ducts from liver (bile) and pancreas (pancreatic juice) enter here
• jejunum: 2nd part, 2.5m long
• ileum: 3rd part, 3.6m long

Question 12

Villi

Answer 12

• cover entire length of small int & increase s.a. for absorption
• nutrients absorbed into either blood capillary or lacteals of villi

Question 13

Microvilli

Answer 13

Microscopic villi found on larger villi to increase S.A.

Question 14

Blood capillary

Answer 14

• absorbs glucose, simple sugars, amino acids, and nucleic acids into bloodstream by active transport

Question 15

Lacteals

Answer 15

• part of lymph system
• absorb glycerol, fatty acids, & fat droplets by diffusion
• lacteals merge to form lymph vessels and eventually add glycerol & fatty acids into circulatory system

Question 16

Hepatic Portal Vein

Answer 16

• nutrient-rich blood from villi moves to HPV
• carries blood from small int. to liver
• allows liver to detoxify ingested food before it travels though body & causes damage

Question 17

Large Intestine (AKA: colon/bowel)

Answer 17

• feces form here
• absorbs water, salts, and vitamins
• takes 12-24hrs to move through
• bacterial/viral irritation may cause less water to be absorbed, resulting in diarrhea
• constipation caused when peristalsis moves feces too slowly -> too much water absorbed -> feces compacted
• composed of cecum, colon, rectum, & anal canal

Question 18

Cecum

Answer 18

Where large int. joins to small int.

Question 19

Appendix

Answer 19

• Small projection of cecum

- may help fight infection (contains lymph tissue) & store bacteria

Question 20

Rectum

Answer 20

• last 20cm of large intestine

- stores feces until it can be eliminated

Question 21

Anus

Answer 21

• where defecation occurs

- feces contains bacteria, fiber, & other indigestible remains

Question 22

Bacteria’s function in large int.

Answer 22

• ex. E. coli
• break down indigestible material
• produce vitamins and minerals that can be used by the body

Question 23

Saliva (mouth)

Answer 23

• contains water, mucus, salivary amylase

- starch + h20 + salivary amylase -> maltose (disaccharide)

Question 24

Gastric Juices (stomach)

Answer 24

1. pepsin - a protease that breaks down proteins - stomach secretes inactive pepsinogen (won't digest stomach) - pepsinogen activated by HCl in stomach (only released when protein-containing foods arrive in stomach) -> pepsinogen becomes pepsin - mucus lining in stomach protects it from pepsin - proteins + h2o + pepsin = peptides (short protein chains) 2. Hydrochloric acid - creates a pH of 2 -> activates pepsin - breaks down connective tissue in meat - kills most bacteria present in food

Question 25

Bile (liver/gall bladder)

Answer 25

- liver produces bile, gall bladder stores it - emulsifies fat (breaks down large fat droplets into small fat droplets in water) - emulsification increases surface area for digestive enzymes to work on

Question 26

Hormones (pancreas)

Answer 26

A) insulin - released when blood glucose level is too high - stimulates all cells of body (except brain) to take up blood glucose (brain cells can absorb glucose w/o insulin) - slows glycogen breakdown in liver - inhibits conversion of amino acids & fatty acids to sugar - all these actions reduce blood glucose B) Glucagon - oppose effect of insulin (increases blood glucose)

Question 27

Pancreatic juice (pancreas)

Answer 27

C) Sodium bicarbonate (NaHCO3) - neutralizes acid chyme from stomach - makes pH of small int. slightly basic (7.6) D) Digestive enzymes - pancreatic amylase + starch + h20 -> maltose - trypsin (protease) + protein + h20 -> peptides - lipase + fat + h20 -> glycerol + 3 fatty acids - nuclease + nucleic acid + h20 -> nucleotides

Question 28

Intestinal juice (small intestine)

Answer 28

- produced by cells lining entire length of small int. - peptidase + peptides + h20 -> amino acids - maltase + maltose + h20 -> glucose + glucose - nucleosidase + nucleotides + h20 -> base + sugar + phosphate * all macromolecules are now broken down into monomers, their smallest components