ch 7 - digestive system [STOMACH, SI, LI, accessory organs]

main functional features of stomach

highly muscular, extremely active holding organ passing bolus to SI

functions

• holds food (up to 75x its empty volume)

• parses out food to SI

• churns

4 main regions of stomach

1. cardia

2. fundus

3. body

4. pylorus

label stomach’s sphincter layers and regions

gastric secretion is controlled by _____ and ____ based on stimuli from the _____, _____, and _______

[nerves] [hormones]

[brain] [stomach] [small intestine]

gastric secretion phases

1. cephalic phase: smell/taste/thought/sight of food stimulates stomach secretory activity

2. gastric phase: stomach distension, food chemicals, and rising pH stimulate secretory activity

3. intestinal phase: low pH and partially digested food stimulate secretory activity

mucosal barrier

protects stomach from corrosive gastric juice

• bicarbonate-rich mucus

• epithelial cells of mucosa block gastric juice from penetrating

• stem cells replace damaged mucosal cells

peristaltic vs mixing waves

peristalsis waves: propel content forward

mixing waves: mechanical digestion

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3 features of SI submucosa

1. circular folds

2. vili

3. microvili

describe the process of how chyme is combined with digestive juices in the SI

contents are pushed back and forth as smooth muscle contracts and relaxes

• segmentation, peristalsis

name the nutrient digestions that occur in the SI

carbohydrate, protein, lipid

water absorption in the SI

via osmosis

functions of LI

• finish nutrient and water absorption

• synthesize vitamins

• form and expel feces

4 regions of LI

1. cecum

2. colon

3. rectum

4. anus

name the regions of LI

describe the order of structures in which food residue passes to reach the anus (use specific names)

Cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anal canal, anus

features of the LI mucosa (cell types)

• simple columnar epithelium w/ microvili

• goblet cells secreting mucus to assist feces movement

• enterocytes absorbing water, salts

3 types of mechanical digestion movement in LI

1. haustral contraction

   1. sluggish segmentation in transverse and descending colons

2. peristalsis

   1. slower contractions than in proximal portions of canal

3. mass movement

   1. strong waves of smooth muscle contraction (pushes residue towards rectum)

3 accessory digestive organs in SI (and their functions)

1. liver: produces bile for duodenum

2. pancreas: produces pancreatic juice for duodenum

3. gallbladder: stores/concentrates/releases bile

liver

• hepatic artery

• hepatic portal vein

• porta hepatis

(accessory organ, SI)

porta hepatis: where the artery and vein enter the liver

• hepatic artery: delivers oxygenated blood to heart

• hepatic portal vein: delivers partially deoxygenated blood w/ nutrients from SI

process occurring once nutrients are processed by the liver

nutrients pass back into blood at central vein → hepatic vein → back to the heart

bile (organ secreting it, structures within it)

secreted by liver (SI accessory organ) to emulsify (break down) lipids

mechanically separates large lipid globules into smaller ones

• water

• bilirubin - pigment produced by liver

• bile salts

• bile pigments

• phospholipids

• electrolytes

pancreas

• cell clusters

• pancreatic ducts

(accessory organ, connects directly to duodenum)

mix of exocrine and endocrine functions

• acinar cells secrete pancreatic juice (bicarbonate + digestive enzymes)

• pancreatic ducts: small ducts that pancreatic juice is secreted into

pancreatic juice (chemical makeup)

(accessory organ)

bicarbonate

digestive enzymes

• (proteins) chymotrypsin

• (proteins) trypsin

• (lipids) pancreatic lipase

• (starch) pancreatic amylase

• (nucleic acids) nucleases

hormones regulating pancreatic juice

• secretin (from SI)

• CCK

gallbladder (function)

• cystic duct

• common ducts

stores, concentrates, and propels bile into duodenum

• ejects bile through cystic duct

• cystic duct + common hepatic duct = common bile duct emptying into duodenum

essential nutrients (def, list)

mlcs that cannot be produced fast enough/at all by body

• 2 essential fatty acids

• 8 essential amino acids

• water

• vitamins and minerals

name 4 fat-soluble vitamins

name 1 water-soluble vitamin

fat-soluble

• D, E, A, K

water-soluble

• C

minerals (def, most common, and important electrolytes)

inorganic ions/compounds that must come from the diet

most common: calcium and phosphorus

imp electrolytes: sodium ions, chloride ions

what mineral ion is needed to make hemoglobin?

iron ion

describe the steps of chemical digestion and absorption through the diagram

fill in the carbohydrate digestion chart

identify mechanisms employed to absorb nutrients (5)

• active transport

• simple diffusion

• facilitated diffusion

• secondary active transport

• endocytosis

describe the chemical/cellular process of absorption

triglycerides broken into monoglycerides and fatty acids

• micelles