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Biology 12 > Digestive System > Flashcards

Digestive System Flashcards

0
Q

Mechanical digestion

A
  • large pieces made smaller to prepare for chemical digestion
  • happens in mouth & stomach
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1
Q

5 functions of digestive system

A
  • ingests food
  • secretes enzymes & hormones
  • digests food into macromolecules
  • absorbs nutrients
  • eliminates feces
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2
Q

Chemical digestion

A
  • enzymes break down macromolecules into small molecules that can be digested
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3
Q

Mouth

A
  • 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
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4
Q

Salivary glands

A
  • sublingual glands: beneath tongue
  • submaxillary glands: beneath lower jaw
  • parotid glands: along side of jaw
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5
Q

Pharynx

A
  • 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
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6
Q

Esophagus

A
  • 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
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7
Q

Stomach

A
  • 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)
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8
Q

Cardiac sphincter

A
  • 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)
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9
Q

Pyloric Sphincter

A
  • relaxes to allow food from stomach into small intestine

- controls rate of stomach emptying

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10
Q

Small Intestine

A
  • 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!)
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11
Q

3 sections of small intestine

A
  • 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
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12
Q

Villi

A
  • cover entire length of small int & increase s.a. for absorption
  • nutrients absorbed into either blood capillary or lacteals of villi
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13
Q

Microvilli

A

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

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14
Q

Blood capillary

A
  • absorbs glucose, simple sugars, amino acids, and nucleic acids into bloodstream by active transport
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15
Q

Lacteals

A
  • 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
16
Q

Hepatic Portal Vein

A
  • 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
17
Q

Large Intestine (AKA: colon/bowel)

A
  • 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
18
Q

Cecum

A

Where large int. joins to small int.

19
Q

Appendix

A
  • Small projection of cecum

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

20
Q

Rectum

A
  • last 20cm of large intestine

- stores feces until it can be eliminated

21
Q

Anus

A
  • where defecation occurs

- feces contains bacteria, fiber, & other indigestible remains

22
Q

Bacteria’s function in large int.

A
  • ex. E. coli
  • break down indigestible material
  • produce vitamins and minerals that can be used by the body
23
Q

Saliva (mouth)

A
  • contains water, mucus, salivary amylase

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

24
Q

Gastric Juices (stomach)

A
  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
25
Q

Bile (liver/gall bladder)

A
  • 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
26
Q

Hormones (pancreas)

A

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)

27
Q

Pancreatic juice (pancreas)

A

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
28
Q

Intestinal juice (small intestine)

A
  • 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

Biology 12 (14 decks)

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