Chapter 18: The Digestive System

The Functions of the Digestive System

Motility, secretion, digestion, absorption, storage and elimination, immune barrier

Motility definition

movement of food through digestive tract

Secretion definition

exocrine and endocrine

Digestion definition

breakdown of food molecules

Absorption definition

passage of digested end products into blood or lymph

Alimentary canal drives ingested food through what

various tubular organs

Alimentary canal is a continuous tube from where

mouth to anus

What do Accessory organs facilitate

digestion and absorption

examples of accessory organs

Salivary glands, liver, gall bladder, pancreas

how is the GI tract regulated

extrinsic and intrinsic mechanisms

what are the extrinsic mechanisms

Autonomic Nervous System and Endocrine System

what are the intrinsic mechanisms

Enteric nervous system and Paracrine regulation

Mastication (Chewing) definition

Mechanical break down food and mixes food with saliva

What does Salivary amylase begin

chemical digestion of starch

Saliva also contains

mucus, HCO3- (buffer), and various immunoglobulins

mastication creates what

bolus

how many phases of swallowing are there

three

Oral phase definition

bolus of food moved by tongue from oral cavity to pharynx

Pharyngeal phase definition

reflex and controlled by swallowing center in medulla oblongata

Esophageal phase definition

reflex that results in stretching of esophagus and peristalsis of muscles

Esophagus is a what

muscular tube

esophagus is a muscular tube from where

pharynx to stomach

what does the esophagus exhibit

peristalsis

peristalsis definition

wave-like muscular contraction

Lower esophageal (gastroesophageal) sphincter definition

narrowed end before stomach

What does the stomach mix

bolus with gastric juices to create chyme

the stomach stores what temporarily

food

what does the stomach initiate

digestion of proteins

what does the stomach kill

bacteria with strong acidity of digestive juice

Pyloric sphincter releases small amounts of

chyme

Pyloric sphincter releases small amounts of chyme to where

duodenum

what do goblet cells secrete

mucus

what do Chief cells Secrete

Secrete pepsinogen a proteolytic enzyme precursor

what do Parietal cells Secrete

HCl and intrinsic factor (B12 absorption

During Hydrochloric acid (HCl) Secretion where is H+ pumped into

lumen

During Hydrochloric acid (HCl) Secretion how is H+ pumped into the lumen

H+/K+ ATPase pumps

During Hydrochloric acid (HCl) Secretion Cl- moves into what cell

parietal cell

During Hydrochloric acid (HCl) SecretionCl- moves into parietal cell on which side

basolateral

During Hydrochloric acid (HCl) Secretion Cl- moves out of what cell

parietal cell

During Hydrochloric acid (HCl) Secretion Cl- moves out of parietal cell on what side

apical side

During Hydrochloric acid (HCl) Secretion Cl- moves out of parietal cell on apical side into where

the lumen

HCl converts pepsinogen into

active pepsinogen

HCl converts pepsinogen into active pepsinogen for what purpose

break down proteins

What do G cells secrete

gastrin

What do Amino acids and distention of stomach stimulate

gastrin release

Enterochromaffin-like cells are Stimulated by

gastrin and secrete histamine

Histamine stimulates

HCl release

What do D cells Secrete

somatostatin

D cells Secrete somatostatin which have what effect on gastric activity

decrease

Where do Almost all absorption and remaining digestion occur

small intestine

The mucosa has a series of 3 structures which increase its surface area 300x, what are the 3 structures

Plica circularis, Intestinal villi, Microvilli

What is the Intestinal Villus covered in

columnar epithelial cells with mucus-secreting goblet cells

Connective tissue core contains

lymphocytes, blood capillaries, and a lacteal (for fat absorption

What do Intestinal crypts contain

Paneth cells and intestinal stem cells

what do microvilli provide

large surface area for absorption

what do microvilli contain

digestive enzymes for final breakdown of the carbohydrates and protein

What does the stimulus of stretching the intestinal walls cause

contraction or relaxation of intestinal smooth muscle

what are the 2 major types of contraction

segmentation, peristalsis

Segmentation definition

produced by slow waves

what is the Peristalsis controlled by

enteric nervous system

Slow waves are produced by the

interstitial cells of Cajal

Autonomic nerves modify the automatic contractions by

influencing the enteric nervous system

Secretin is released in response to what

acidic chyme in the duodenum

Secretin = Released in response to acidic chyme in the duodenum Stimulates secretions of

HCO3- from the pancreatic, liver, and gall bladder ducts

Cholecystokinin (CCK) = Released in response to

proteins or lipids in the small intestines

Cholecystokinin (CCK) Stimulates secretions of the

pancreas and gall bladder

what does the Cholecystokinin (CCK) inhibit

gastric activities

Gastric inhibitory peptide (GIP) Inhibits

gastric activity

Gastric inhibitory peptide (GIP) Inhibits gastric activity and Stimulates

secretion of insulin from pancreas

Cecum

below the junction with small intestine

Ascending colon

goes up right side of body

Transverse colon

crosses abdominal cavity

Descending colon

passes down left side of body

What does the Sigmoid colon enter

rectum

How is the large intestine characterized

haustra

haustra definition

pouches that store material and taenia coli

taenia coli definition

band of muscle that cause mass movement

which vitamins do Microflora or intestinal microbiota produce

B vitamins, vitamin K

Microflora or intestinal microbiota is largely what

anaerobic

Microflora or intestinal microbiota produce what

Produce short-chain fatty acids

why is it important that microflora or intestinal microbiota produce short chain fatty acids

for absorption

Large Intestine Function

absorb remaining H2O from the small intestine (10% to 20%) and various vitamins and minerals

what other function does the large intestine serve

forms, stores, and releases feces

GLP-1 (glucagon-like peptide-1 functions

Decrease gastric activity , Stimulates secretion of insulin from pancreas

what are liver cells called

hepatocytes

Liver cells called hepatocytes form

hepatic plates separated by sinusoids

Sinusoids are fenestrated but more

permeable than the fenestrated capillaries of kidneys

Sinusoids also contain

phagocytic cells called Kupffer cells

Venous (hepatic portal) and arterial blood mix in the

hepatic sinusoids

Venous (hepatic portal) and arterial blood mix in the hepatic sinusoids and flow to the

central vein

what is Bile is produced by

by hepatocytes

Bile is produced by hepatocytes and flows through

canaliculi to bile ducts

Bile is produced by hepatocytes and flows through canaliculi to bile ducts at the

portal triad

Enterohepatic Circulation

Refers to a phenomenon where secreted bile substances, particularly drugs, are reabsorbed by the small intestines

Functions of the Liver

1. Detoxification of blood via phagocytosis by Kupffer cells, 2. Carbohydrate and Lipid metabolism,3. Plasma protein synthesis, Bile Production and Secretion

what does bile consist of

bilirubin (pigment), bile salts, phospholipids, cholesterol, and inorganic ions

what does bile do to fat

Emulsifies it in the small intestine

Gall Bladder function

Stores, concentrates, releases bile

what is the gall bladder stimulated by

CCK from the small intestine

Pancreas as an Exocrine Gland contains what

pancreatic acini