Overview

Question 1

GI function

Answer 1

(DEEPMASS acronym) – digestion, endocrine, expulsion, protection, motility , absorption, secretion, storage

Question 2

Fluid Volume

Answer 2

o Fluid volumes and pH changes through the tract facilitate digestion and absorption
o Control of fluid balance through secretion, absorption and reabsorption of fluids
 Intake only ~2L a day but GI tract secretes an additional 7-8 liters
 Therefore must absorb 9-10 liters of fluid each day

Question 3

Mouth

Answer 3

mechanical digestion, salivation for carbohydrates and lipids

Question 4

stomach

Answer 4

– chemical breakdown of food by acid and enzymes

 Mechanical breakdown via muscular contractions

Question 5

Small intestine

Answer 5

-enzymatic digestion & absorption of water, organic substrates, vitamins & ions
 Host defense

Question 6

duodenum

Answer 6

– first part of small intestine and entry of common bile duct
• Carbohydrates, proteins, and lipids are rapidly digested and absorbed

Question 7

jejunum

Answer 7

most of absorption occurs before the end of the jejunum

Question 8

ileum

Answer 8

FINAL absorption of nutrients, salt, and water

Question 9

large intestine

Answer 9

– dehydration and compaction of indigestible materials for elimination
 Resorption of water and electrolytes
 Host defense

Question 10

liver

Answer 10

secretes bile (important for lipid digestion)
 Storage of nutrients
 Production of cellular fuels, plasma proteins, clotting factors
 Detoxification and phagocytosis

Question 11

pancreas

Answer 11

– secretion of basic buffers to increase pH in small intestines
 Secretion of digestive enzymes by exocrine glands
 Secretion of hormones by endocrine cells to regulate digestion

Question 12

gall bladder

Answer 12

storage and concentration of bile

Question 13

salivary glands

Answer 13

– secretion of lubricating fluid containing enzymes that initiate digestion

Question 14

Structure (small intestine)

Answer 14

o Lumen
o Intestinal villi with epithelial lining – 1 cell thick
o Lamina propria (connective tissue) with glands and mucosa
o Muscularis mucosae
o Submucosa with submucosal blood vessels, nerves, and glands
o Common bile duct
o Muscularis externa - motility
 Inner circular muscle layer
 Outer longitudinal muscle layer
o Serosa
o Mesentery

Question 15

Enteric Nerves

Answer 15

– even if you lose/damage the autonomic input to GI tract, it will still retain motility and secretions due to enteric nervous system
o Myenteric plexus – between the muscle layers; propulsion
o Submucosal plexus – between circular muscle and submucosa; secretion
 Senses stretch and osmolarity of chyme

Question 16

Vascularization

Answer 16

• provides an energy source, connection to other sites for endocrine actions, and an outlet for nutrient absorption
  o Blood flow to the intestines increases for 3-6 hours after eating to facilitate absorption
  o Splanchnic circulation – blood from intestines travels through portal vein to the liver
   All absorbed nutrients pass through the liver (first-pass effect) to be processed, cleaned up and stored so the liver can control the release of absorbed substances

Question 17

Regulation

Answer 17

o Parasympathetic system – mainly vagus nerve – PROmotility and PROsecretion
o Sympathetic nervous system – mainly slows/stops/shuts down GI tract, digestion, and motility
o Enteric nervous system – made up of myenteric and submucosal plexes
 Can function without extrinsic nervous system input
o Central nervous system – anticipatory response – smelling/seeing food initiates salivation; something in your mouth initiates hydrochloric acid secretion in stomach
o Lumenal Chemo-, mechano-, and osmoreceptors in mucosa signal the enteric nerves for local response
o Hormones – made locally in GI tract; acting in autocrine, paracrine, and endocrine manners

Question 18

Smooth vs. Skeletal muscle

Answer 18

-smooth muscle everywhere in GI tract EXCEPT: mouth, upper esophagus sphincter, external anal sphincter

Question 19

borborygmi

Answer 19

– sound of fluids and gases moving through the GI tract