CH 35 Gastrointestinal Function

What is the primary function of the gastrointestinal (GI) system?

To facilitate digestion and absorption of nutrients.

What are the three general functions of the GI system

movement (propulsion & mixing), secretion of digestive juices, digestiona nd absorption of nutrients

The GI system is divided into

upper GI, lower GI, Accessory GI organs

What are the major structures of the GI tract?

Oral cavity, pharynx, esophagus, stomach, small intestine, large intestine.

At the fourth week of gestation, what is present?

divisions of the intestines

The third week of gestation

Embryonic structures begin to fold inward to create the primitive gut

Foregut

pharynx, esophagus, stomach, duodenum, hepatobiliary system, and pancreas

Midgut

Small intestine, ecum, appendix, ascending colon, proximal transverse colon

Hindgut

distal transverse colon, descending colon, sigmoid colon, rectum, superior anal canal

What are the three main divisions of the intestines during embryonic development?

Foregut, midgut, hindgut.

Atresia

to end as a blind pouch

Fistula

abnormal connection between two body parts

What is esophageal atresia?

A developmental disorder where the esophagus ends as a blind pouch.

What is a tracheoesophageal fistula?

An abnormal connection between the trachea and esophagus.

intestinal atresia

Failure of normal partitioning between the foregut and the midgut

With intestinal atresia in the small intestine, what leads to the development of a blind pouch and discontinuity of the GI?

Necrotic gut is reabsorbed into the fetus

with Intestinal Atresia of the small intestine, what is the maternal potential etiology

methamphetamine and pseudoephedrine, as well as smoking

What is omphalocele?

A congenital herniation of the viscera into the base of the umbilical cord.

Colonic or Anal Agenesis

rectal pouch ends blindly above the surface of the perineum

Anal Stenosis

Anal aperture is small (narrowed)

anal atresia (imperforate anus)

anal membrane persists and covers the aperture to create an obstruction

Omphalocele of the small intestine is due to?

Failure of the midgut to rotate properly with respect to the umbilical cord

Oral cavity function

break up food particles

Pharynx function

swallowing

esophagus function

conduit for food

stomach function

The main site of chemical digestion

small intestine function

The main site of nutrient absorption

large intestine function

reabsorbs remaining water and vitamins, stores feces for excretion

Salivary glands

saliva; starts carbohydrate digestion

The pancreas secretes what?

pancreatic enzymes

The liver makes what?

bile

What are 3 things the gallbladder does with bile?

stores, concentrates, and secretes

Bile ducts do what?

transport bile

Saliva is secreted by what 3 major glands?

Parotid, submandibular, and sublingual glands

What allows for taste perception?

saliva

Digestion of carbohydrates will produce what two things?

dextrin and maltose

What does the LES (lower esophageal sphincter) prevent?

highly acidic contents from moving up from the stomach into the esophagus

GERD will result in

heartburn or dyspepsia

What are the parts of the stomach

cardia, fundus, body, antrum

Chief cells secrete

pepsinogen and gastric lipase

Parietal cells secrete

HCL and intrinsic factor

surface mucous cells secrete

alkaline mucus

Gastrin cells secrete

gastrin

What cells monitor intragastric pH

gastrin cells

Digestion and absorption of nearly all nutrients occur where? regarding the small intestine

duodenum and jejunum

Absorption of vitamin B12 and Bile Salts occurs where? regarding the small intestine

terminal ileum

What regulates gastric emptying and motility to enhance digestiona nd absorption of nutrients

mucosal horomones

CCK is released from the small intestine in respone to _____

fatty chyme

CCK stimulates____ to strongly contract and release ____

gallbladder, bile

CCK stimulates ____ to release _____ juice

pancreas, pancreatic

CCK ______ stomach motility and release of gastric secretions

inhibits

CCK will ______ satiety

induce

Secretin is a horomone released from small intestine in response to _________

increased chyme acidity

Secretin stimulates realease of ____ and _____

pancreatic fluid and alkaline HCO3-

secretin inhibits ____ and ______

gastric secretions and motility

What is the primary role of the small intestine?

Main site of nutrient absorption.

What are the three sections of the small intestine?

Duodenum, jejunum, ileum.

What is the function of the lower esophageal sphincter?

To prevent acidic gastric contents from moving up into the esophagus.

What is the role of salivary amylase?

To begin the chemical digestion of carbohydrates in the oral cavity.

What are the major secretions of the stomach?

Hydrochloric acid (HCl), pepsinogen, gastric lipase, intrinsic factor.

What is the function of the gastric mucosa?

To secrete digestive juices and protect the stomach lining.

What is the primary function of the large intestine?

To absorb remaining water and electrolytes and store feces.

What are plicae circulares?

Circular folds of mucous membrane in the small intestine that increase surface area.

What is the role of intestinal villi?

To increase surface area for digestion and absorption of nutrients.

Microvilli

microscopic projections covered with a brush border

Brush borders contain many?

digestive enzymes

What is peristalsis?

A progressive type of movement that propels material through the GI tract.

Colon is the tube from the?

Cecum to Rectum

appendicitis

inflammation of the appendix

What hormones regulate gastric emptying and motility?

Cholecystokinin (CCK), secretin, and gastric inhibitory peptide (GIP).

What is the primary function of the large intestine mucosa?

absorb remaining water and electrolytes

Goblet cells produce

mucus

Parasympathetic nervous system will ____ motility/secretions

increase

Vagus Nerve innervates?

proximal GI all the way to the proximal 1/2 of the large intestine

Sacral Plexus innervates?

remaining regions after Vagus

What parasympathetic nerve plays a key role in defecation?

Sacral Plexus

SNS ______ motility/secretions

decreases

SNS will secrete ______ which is inhibitory to the PNS and intrinsic nervous system of the GI

norepinephrine

Inhibits GI activity and motility

SNS

The Intrinsic Nervous System is responsible for what?

GI reflexes

Myenteric Plexus is also called?

Auerbach's plexus

Myenteric (Auerbach) plexus is in control of?

GI Movements

The submucosal plexus is also called

Meissner's plexus

Submucosal (Meissner) plexus is in control of?

secretion and sensory function

Gastrin will ______ stomach motility

increase

Causes increased constriction of the LES

Gastrin

gastrin is the?

Primary mediator of gastric acid secretions

CCK is

Secreted by jejunum mucosa when fat enters jejunum

CCk will increase

contractility of gallbladder

CCK will stimulate

pancreatic secretions

CCk helps

regulate gastric emptying and bowel motility

Secretin is produced by the mucosa of the duodenum in response to

The entry of acidic gastric juice from the stomach

secretin stimulates

pancreatic fluid and bicarbonate secretion, neutralizing the acidity of intestinal contents

Secretin will

decrease motility

Gastric Inhibitory Peptide (GIP) will

decrease stomach motility

GIP is released from the upper portion of the small intestine in response to

fat in chyme and carbohydrates

What is the role of ghrelin?

To increase appetite and stimulate growth hormone secretion.

What is the function of goblet cells in the large intestine?

To produce mucus for the concentration and storage of feces.

What is anal atresia?

A condition where the anal membrane persists and covers the anal aperture, creating an obstruction.

What are the major accessory structures of the GI system?

Salivary glands, pancreas, liver, gallbladder.