BIOL40C Ch. 24 Digestive System

mouth, pharynx, esophagus, stomach, small intestine, large intestine

(MPESSL)

teeth, tongue, salivary glands, liver, pancreas, gall bladder

(TTSLPG)

yes, although most do not come into contact with food

secrete or store secretions needed for digestion

• 1) ingestion
• 2) secretion of substances to aide in digestion
• 3) mixing & propulsion
• 4) digestion (mechanical, chemical)
• 5) absorption
• 6) disposal of wastes

process of digested food, fluids, ions crossing the gut wall to enter blood or lymph

by properties of epithelial cells

mucosa, submucosa, muscularis, serosa

epithelium, connective tissue layer (lamina propria), smooth muscle

non-keratinized stratified squamous

non-keratinized stratified squamous

non-keratinized stratified squamous

non-keratinized stratified squamous

simple columnar

mucosa-associated lymphatic tissue

immune cell clusters in lamina propria

tonsils, small intestines, appendix, large intestine

• 1) myenteric plexus
• 2) submucosal plexus

between circular and longitudinal muscle layers of muscularis

in submucosa

by interneurons

controls gut motility

control secretion

parasympathetic: increase GI secretion/motility

sympathetic: decrease GI secretion/motility

via cranial nerve X (vagus)

EXCEPT large intestine, which is supplied by PS fibers from sacral spinal cord

from thoracic & lumbar regions of spinal cord

space containing lubricating serous fluid between parietal and visceral portions of peritoneum

lines outside of abdominopelvic cavity

covers some organs of abdominopelvic cavity

largest serous membrane in the body

consists of mesothelium (simple squamous), w/ underlying layer of areolar CT

acute inflammation of the peritoneum

caused by infectious microbes

fluid accumulated in the peritoneal cavity in some diseases

between teeth, hard palate, soft palate, and tongue

inferior/anterior to the ears, between skin & masseter muscle

floor of the mouth, medial/partly inferior to body of the mandible

beneath tongue, superior to submandibular glands

• 99.5% water
• ions, enzymes, mucous

inflamed parotid glans due to paramyxovirus

also inflammation of testes in adult men

gastrointestinal reflux disease

lower esophageal sphincter doesn't close completely, resulting in reflux

can lead to esophageal cancer

swallowing

• 1) chief cells
• 2) parietal cells
• 3) surface mucous cells
• 4) mucous neck cells
• 5) G cells

secrete pepsinogen, gastric lipase

breaks down proteins/peptides, triglycerides

secrete HCl, intrinsic factor

needed for vitamin B12 absorption, which is used in RBC formation

secrete mucous as protective barrier

some absorption

secrete gastrin

stimulates parietal cells to secrete HCl, and chief cells to secrete pepsinogen

contracts lower esophageal sphincter, increases motility of stomach, relaxes pyloric sphincter

• 1) make chyme
• 2) hold food until room in small intestine
• 3-7) secrete HCl, pepsin, intrinsic factor, lipase, gastrin

mixture of saliva, food, gastric juices

• 1) mucous neck cells
• 2) parietal cells
• 3) chief cells

G cells

• 1) carbonic anhydrase (CA) forms carbonic acid (H₂CO₃) from water & CO2
• 2) H₂CO₃ dissociates to form H⁺ & bicarbonate (HCO₃^-)
• 3) H+ secreted into lumen by H+/K+ pump
• 4) HCO3- exchanged for Cl- by Cl-/HCO3- antiporter
• 5) Cl- secreted by Cl- channel

• 1) ACh from PS neurons
• 2) gastrin from G cells
• 3) histamine from mast cells

acini (99%)

islets (1%)

amylase, trypsin, carboxypeptidase, elastase, lipase, RNase, DNase

digests starch

digest proteins

insulin, glucagon, somatostatin, pancreatic polypeptide

• - hexagonal
• - central vein in center
• - portal triad at 3 corners

bile duct, hepatic artery, portal vein

from GI -> portal vein -> sinusoids -> central vein -> hepatic veins -> inferior vena cava

(TOWARD central vein)

• 1) hepatocytes
• 2) bile duct cells
• 3) Kupffer cells (phagocytes)

• 1) carb, fat, protein metabolism
• 2) hormone, drug processing
• 3) excrete bilurubin
• 4) synthesize bile salts
• 5) vitamin, mineral storage
• 6) phagocytosis
• 7) vitamin D activation

stores/concentrates bile

pear-shaped sac in depression of liver

• - secreted by hepatocytes, stored in gall bladder
• - partial excretory product, partially digestive secretion
• - bile salts break down large lipid globules

principal bile pigment

derived from heme, by-product of RBC phagocytosis

• 1) duodenum
• 2) jejunum
• 3) ileum

microvilli lining small intestine

increases surface area of plasma membrane of absorptive cells -> larger amounts of digested nutrients can diffuse into cells

• 1) a-dextrase
• 2) sucrase
• 3) lactase
• 4) maltase

• 1) pepsin (stomach)
• 2) trypsin, chymotrypsin, carboxypeptidase, elastase
• 3) aminopeptidase, dipeptidase (brush border)

monosaccharides (glucose, fructose, galactose)

amino acids

(and some di-/tri-peptides)

fatty acids and glycerol

• - secondary active transport
• - facilitated diffusion
• - active transport

most sugars transported by cotransport with Na+ ions

• - short chain FAs absorbed by simple diffusion
• - long chain FAs & monoglycerides form micelles with bile salts

large aggregates of long chain FAs in the cell (entered by transport to brush border as micelles)

leave cell by exocytosis, transported via lacteals

9.3L

9.2L

• 1) saliva
• 2) ingested liquids
• 3) gastric juice
• 4) pancreatic juice
• 5) intestinal juice

• 1) completion of absorption (particularly water)
• 2) production of some B vitamins and vitamin K
• 3) formation of feces
• 4) expulsion of feces