chapter 24: Digestive system

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128 Terms

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digestive tract

gastrointestinal tract

muscular tube with different parts

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accessory organs of the digestive system

teeth, tongue, salivary glands, liver, gallbladder, pancreas, gastrinal and intestinal glands

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digestive system function

ingestion, mechanical processing, digestion, secretion, absorption, excretion

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ingestion

put food into digestive system

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mechanical processing

chewing and swallowing food

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digestion

chemical breakdown of food

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secretion

cells release h2o, salts, enzymes

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absorption

bring stuff from inside tube into blood

nutrients, vitamins, ions

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excretion

removes wastes

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oral cavity

mouth; contains teeth and tongue

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pharynx

throat; passageway for food to the esophagus and air to the larynx

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esophagus

A muscular tube that connects the mouth to the stomach.

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stomach

large muscular sac that continues the mechanical and chemical digestion of food

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small intestine

Digestive organ where most chemical digestion and absorption of food takes place

duodenum, jejunum, ileum

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large intestine

Absorbs water and forms feces

cecum, appendix, colons

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cecum

the cavity in which the large intestine begins and into which the ileum opens

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appendix

A small, fingerlike extension of the vertebrate cecum; contains a mass of white blood cells that contribute to immunity.

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transverse colon

passes horizontally from right to left toward the spleen

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decending colon

part of colon that progresses downward (caudally)

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sigmoid colon

an S-shaped structure that continues from the descending colon above and joins with the rectum below

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ascending colon

travels upward from the cecum to the undersurface of the liver

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serosa

outermost layer of GI tract

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muscularis externa

responsible for segmentation and peristalsis

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layers of muscularis externa

inner circular layer and outer longitudinal layer

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submucosa

larger CT area

larger blood vessels and nerves

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mucosa

epithelium, lamina propria, muscularis mucosae

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myentric nerve plexus

controls GI tract motility

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segmentation

constricting the tube and dividing its contents

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mixing

moving material back and forth slowly

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further mixing

maximises nutrient absorbtion

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mixing steps

1. segmentation

2. mixing

3. further mixing

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peristalsis

coordinated wave of muscular contraction that propels material through the tube

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oral cavity functions

sensory analysis, mechanical processing, lubrication, chemical digestion

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buccal phase of swallowing

voluntary

tongue moves up, pushes food back, soft palate lifts up, materials enter oropharynx

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pharyngeal phase of swallowing

involuntary

cranial nerves cause muscles of pharynx to contract

larynx elevates

epiglottis closes, blocks trachea

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esophageal phase of swallowing

esophageal sphincter opens to allow bolus to enter stomach

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bolus enters stomach

chemical digestion of food continues

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esophigal sphincter

last part of esophagus before stomach

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cardia

area around the opening of the esophagus

produces mucous to protect

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fundus of stomach

The upper left portion of the stomach, which has a curved, dome-shaped appearance.

storage

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body of stomach

mixing chamber

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pylorus

controls food moving into the duodenum

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stomach function

storage

mechanical/chemical breakdown

intrinsic factor (absorbs b12)

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layers of muscularis externa of stomach

outer longitudinal, middle circular, inner oblique

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stomach motility

moving material from stomach into duodenum

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distention increasing motility

stretch of stomach

activate sensory receptors that activate parasympathetic

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hormone increasing motility

gastrin (stomach/duodenum)

gastric secretors and contractions of muscularis externa

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distention decreasing motility

enterogastric reflex

stomach slows down

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hormones decreasing motility

secretin

gastroinhibitory peptide (GIP)

choleocytoskin (CCK)

from duodenum

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gastrocentric reflex

controls movement of materials from stomach into small intestine

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gastroileal reflex

controls movement of material from small to large intestine

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haustrum

small pouches caused by sacculation, which give the colon its segmented appearance

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haustral churning

mixing of material

produces feces

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mass movements

large intestine into rectum

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defecation

wastes leave the body and eliminates feces from the body

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defacation reflex

stimulus: feces in rectum

response: perastalis in rectum

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consequences of defection reflex

contractions (descending, sigmoid, rectum)

internal anal sphincters relax

external anal sphincters close

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socially acceptable to defacate

anal sphincter relax

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socially unnaceptable to defacate

reflex dies down until acceptable

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chemical digestion proteins

proteins --> short polypeptides --> single amino acids

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chemical digestion carbohydrates

carbs --> di/trisaccharides --> monosaccharides

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chemical digestion fats

fats --> triglycerides --> glycerol/fatty acids

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saliva

produces 1-2 L a day

h2o, SCH's, mucus, enzymes

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lysosome

attacks bacteria

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lingual lipase

digest fat

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salivary amylase

digest carbs

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digestion by saliva

- starch is broken down by salivary amylase into di and tri saccharides

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regulation of salivary secretion

cranial nerves --> medulla oblognata --> parasympathetic

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gastric juice

highly acidic (ph=2)

secretions from gastric glands

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mucous cells

secrete mucus

located in gastric pits

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parietal cells

cells of gastric gland

secrete HCL, intrinsic factor (B-12 absorption)

HCl dentures proteins

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chief cells

cells of gastric gland

secrete pepsinogen (inactive)

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g cells

pylorus

enterodnocrine cells

secretes gastrin

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cephalic secretion

increases parasympathetic and digestive function

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gastric secretions

neural, hormonal, local

food enters stomach

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neural gastric secretion

stretch and chemoreceptors

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hormonal gastric secretion

secretes gastrin

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local gastric phase

lamina propria release histamine

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intestinal secretions

food enters small intestine

neural, hormonal

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neural intestinal phase

estrogastric reflex

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hormonal intestinal phase

CCK

GIP

Secretin

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hepatocytes

produce bile in the liver

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bile

emulsifies fats

h2o, ions, bilirubin, bile salts

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release of bile

goes through ducts to gall bladder

gall bladder to duodenum

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gall bladder

stores and concentrates bile

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chyme

acidic soupy mixture from stomach

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gall bladder regulation

chyme stimulates cck (concentration of bile)

opens hepadipancreatic sphincter

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pancreas

Regulates the level of sugar in the blood

exocrine and endocrine

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endocrine pancreas

regulates blood glucose

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exocrine pancreas

secretes digestive enzymes

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pancreatic juice

water, bicarbonate/phosphate buffers, enzymes

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pancreatic alpha-amylase

breaks down starches to di and trisaccharides

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pancreatic lipase

breaks down triglycerides to fatty acids and glycerols

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nucleases

break down nucleic acids

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proleolytic enzymes

break down proteins

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inactive proenzymes

proteolytic enzymes secreted

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Trypsinogen active enyme

trypsin

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What converts trypsinogen to trypsin?

enteropeptidase

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trypsin function

activate other enzymes

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Chymotrypsinogen active form

chymotrypsin