Digestive System Flashcards
0
Q
Mechanical digestion
A
- large pieces made smaller to prepare for chemical digestion
- happens in mouth & stomach
1
Q
5 functions of digestive system
A
- ingests food
- secretes enzymes & hormones
- digests food into macromolecules
- absorbs nutrients
- eliminates feces
2
Q
Chemical digestion
A
- enzymes break down macromolecules into small molecules that can be digested
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
4
Q
Salivary glands
A
- sublingual glands: beneath tongue
- submaxillary glands: beneath lower jaw
- parotid glands: along side of jaw
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
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
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)
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)
9
Q
Pyloric Sphincter
A
- relaxes to allow food from stomach into small intestine
- controls rate of stomach emptying
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!)
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
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
13
Q
Microvilli
A
Microscopic villi found on larger villi to increase S.A.
14
Q
Blood capillary
A
- absorbs glucose, simple sugars, amino acids, and nucleic acids into bloodstream by active transport
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
- 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) - 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
