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Flashcards in Overview Deck (19):
1

GI function

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

2

Fluid Volume

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

3

Mouth

mechanical digestion, salivation for carbohydrates and lipids

4

stomach

– chemical breakdown of food by acid and enzymes
 Mechanical breakdown via muscular contractions

5

Small intestine

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

6

duodenum

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

7

jejunum

most of absorption occurs before the end of the jejunum

8

ileum

FINAL absorption of nutrients, salt, and water

9

large intestine

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

10

liver

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

11

pancreas

– 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

12

gall bladder

storage and concentration of bile

13

salivary glands

– secretion of lubricating fluid containing enzymes that initiate digestion

14

Structure (small intestine)

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

15

Enteric Nerves

– 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

16

Vascularization

- 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

17

Regulation

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

18

Smooth vs. Skeletal muscle

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

19

borborygmi

– sound of fluids and gases moving through the GI tract