Pathophysiology Ii

Front 1

Transverse colon

Back 1

Extends across the abdomen, anterior to the SI

Front 2

Descending colon

Back 2

Turns downward on left side of abdomen

Front 3

Sigmoid colon

Back 3

Empties into the rectum

Front 4

Rectum

Back 4

Has outlet at the anus for elimination of feces

Front 5

Intestinal wall

Back 5

Responsible for many reflexes that occur locally in the GI tract

Front 6

Two layers of intrinsic nervous system

Back 6

Submucosal and myentric plexus

Front 7

› Submucosal plexus

Back 7

Controls secretion and sensory functions

Front 8

Myenteric plexus

Back 8

Lies between longitudinal and circular muscular layers Responsible for control of GI movements
Stimulation increases GI tract activity

Front 9

Parasympathetic innervation

› Cranial

Back 9

Transmitted with vagus nerves to provide extensive innervation to esophagus, stomach, pancreas, first half of the large intestine

Front 10

Parasympathetic innervation

› Sacral

Back 10

Originates in 2nd, 3rd, 4th sacral segments of spinalcord

Innervates the distal half of the large intestine Key role in defecation reflex

Front 11

Sympathetic innervation

Back 11

› Originate in spinal cord between T8 and L3
› Postganglionic fibers radiate out to all parts of GI

tract

Front 12

Sympathetic innervation

› Secrete norepinephrine

Back 12

Promotes inhibitory effects of SNS and on neurons of the intrinsic nervous system of the GI tract

Strong stimulation can shut down motility and block movement of nutrients

Front 13

Afferent nerve fibers

Back 13

› Transmit important information about status
› Bodies in submucosal plexus and terminate in

myenteric plexus
Transmit signals resulting in excitation or inhibition of

motility or secretion

Front 14

Electrical activity of gastrointestinal smooth muscle

Back 14

› Slow-wave
Stimulation by stretching or effects of acetylcholine or parasympathetic excitation

Front 15

Hormonal control

› Gastrin

Back 15

Secreted by the mucosa of antrum in response to food entering the stomach

Increases stomach motility

Front 16

Hormonal control

>Cholecystokinin

Back 16

Secreted by mucosa of the jejunum in response to entry of fatty substances; increases contractility of the gallbladder

Front 17

Hormonal control

> Gastric inhibitory peptide

Back 17

Secreted by mucosa of upper portion of SI in response to the presence of fat; decreases stomach motility

Front 18

Intestinal contraction of smooth muscle

Back 18

› Slow waves without superimposed spikes do not give rise to

contraction

› Electrical activity in smooth muscle of gut gives rise to contractions

Front 19

Chewing

Back 19

› First step in nutrient digestion

› Voluntary control

› Process of moving food in mouth and mixing it with saliva

Front 20

Swallowing:

Back 20

transport of material from mouth to stomach

Front 21

Swallowing happens in four (three) stages:

Back 21

~Oral stage

Bolus passed from mouth to pharynx

~Pharyngeal stage

Bolus passed through pharynx into esophagus ~Esophageal stage

Pharyngoesophageal junction relaxation and pharyngoesophageal sphincter contraction force bolus into esophagus

Front 22

Neural control of swallowing

Back 22

› Swallowing receptor in posterior of mouth and throat

transmits impulses in response to stimulus to mucous

membranes in mouth

› Impulses travel by trigeminal nerve into medulla

oblongata (swallowing center)

› Once activated, muscular reactions occur

› Reactions are automatic and cannot be stopped

voluntarily

Front 23

Motor function of stomach

Back 23

Concentric circles move food
Peristaltic contractions occur once every 20 seconds Contractions in antrum are responsible for mixing

nutrients with gastric secretions Mixture called chyme

Front 24

Small intestine

Back 24

› 3-5 hours for passage from pyloric sphincter to

ileocecal valve

Front 25

Small intestine

› Segmental contractions (mixing)

Back 25

Back-and-forth action that breaks apart chyme and

mixes with digestive juices
As one set of contractions is completed, a new set

begins
Contractions occur at rate of 7-12 times/min

Front 26

Ileocecal sphincter

Back 26

› Normally closed
› Relaxes when intestinal contents are present in

terminal ileum
› Propulsive movement push contents into cecum

Front 27

Large intestine (colon)

Back 27

› Main function is fluid absorption
› Storage of fecal mass until expelled from body
› Segmental contractions produce haustral churning

› Defecation

Takes about 18 hours to reach distal end › One to three mass movements per day