Human Anatomy and Physiology - The Digestive System

Flashcards about the digestive system.

What are the main functions of the digestive system?

Take in food, break it down into nutrient molecules, absorb molecules into the bloodstream, and rid body of any indigestible remains.

What are the two main groups of organs in the digestive system?

Alimentary canal and accessory digestive organs.

Name the organs of the alimentary canal.

Mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus.

Name the accessory digestive organs.

Teeth, tongue, gallbladder, salivary glands, liver, pancreas.

Name the six essential activities of processing food.

Ingestion, propulsion, mechanical breakdown, digestion, absorption, defecation.

What is ingestion?

Eating.

What is propulsion?

Movement of food through the alimentary canal.

What is peristalsis?

Alternating waves of contraction and relaxation.

What does mechanical breakdown include?

Chewing, mixing food with saliva, churning food in the stomach, and segmentation.

What is segmentation?

Local constriction of intestine that mixes food with digestive juices.

What is digestion?

Series of catabolic steps that involves enzymes that break down complex food molecules into chemical building blocks.

What is absorption?

Passage of digested fragments from lumen of GI tract into blood or lymph.

What is defecation?

Elimination of indigestible substances via anus, in the form of feces.

What is the peritoneum?

Membranes of abdominal cavity.

What is the visceral peritoneum?

Membrane on external surface of most digestive organs.

What is the parietal peritoneum?

Membrane that lines the body wall.

What is the peritoneal cavity?

Fluid-filled space between two peritoneums

What is the mesentery?

Double layer of peritoneum.

What are intraperitoneal organs?

Organs located within the peritoneum.

What are retroperitoneal organs?

Organs located outside, or posterior to, the peritoneum.

What is peritonitis?

Inflammation of the peritoneum.

What are the four basic layers, or tunics, of digestive organs?

Mucosa, submucosa, muscularis externa, serosa.

What is the mucosa?

Tunic layer that lines the lumen.

What are the three sublayers of the mucosa?

Epithelium, lamina propria, muscularis mucosae.

What is the lamina propria made of?

Loose areolar connective tissue.

What is the muscularis mucosae?

Smooth muscle that produces local movements of mucosa.

What does the submucosa consist of?

Consists of areolar connective tissue.

What is the Muscularis externa?

Muscle layer responsible for segmentation and peristalsis.

What is the serosa?

Outermost layer. Made up of the visceral peritoneum.

What does the splanchnic circulation include?

Arteries that branch off aorta to serve digestive organs.

What is the hepatic portal circulation?

Drains nutrient-rich blood from digestive organs and delivers blood to liver for processing.

What is the enteric nervous system also referred to as?

The gut brain.

What does the submucosal nerve plexus regulate?

Regulates glands and smooth muscle in mucosa.

What does the myenteric nerve plexus control?

Controls GI tract motility.

What are short reflexes?

Mediated by enteric nerve plexuses (gut brain); respond to stimuli in GI tract.

What are long reflexes?

Respond to stimuli arising inside or outside of gut, such as from autonomic nervous system.

What does the parasympathetic system do to the digestive process?

Enhances digestive process.

What does the sympathetic system do to the digestive process?

Inhibits digestion.

What do intrinsic controls involve?

Involve short reflexes (enteric nervous system).

What do extrinsic controls involve?

Involve long reflexes (autonomic nervous system).

What provokes digestive activity?

Mechanical and chemical stimuli.

What are the effectors of digestive activity?

Smooth muscle and glands.

what is deglutition?

Swallowing.

What are the four alimentary canal layers?

Mucosa, submucosa, muscularis externa, and serosa.

What is heartburn?

A condition caused by stomach acid regurgitating into the esophagus.

What happens during the buccal phase of deglutition?

Voluntary contraction of the tongue

What happens during the pharyngeal-esophageal phase of deglutition?

involuntary phase that primarily involves the vagus nerve. Controlled by swallowing center in medulla and lower pons

What is the stomach?

A temporary storage tank that starts chemical breakdown of protein digestion.

What does the cardial part of the stomach do?

Surrounds the cardial orifice.

What is the fundus of the stomach?

Dome-shaped region beneath the diaphragm.

What part of the is the body?

Midportion of the stomach.

What is the pyloric part of the stomach?

The wider and more superior portion of the pyloric region.

What is the pyloric valve?

Sphincter controlling stomach emptying

What is the greater curvature of the stomach?

Convex lateral surface of stomach.

What is the lesser curvature of the stomach?

Concave medial surface of stomach.

What is the lesser omentum?

Runs from lesser curvature to liver.

What is the greater omentum?

Drapes inferiorly from greater curvature over intestine, spleen, and transverse colon.

What are the branches of the celiac trunk?

Gastric and splenic branches.

How many muscle layers does the muscularis externa have?

Three layers, circular, longitudinal, and oblique.

What cell type is the mucosa layer of the stomach made of?

Simple columnar epithelium entirely composed of mucous cells.

What do mucous cells do?

Secrete two-layer coat of alkaline mucus.

What defines the surface of the mucosa layer?

Dotted with gastric pits that lead into gastric glands.

What are the secretory cells of the gastric glands?

Mucous neck cells, Parietal cells, Chief cells, Enteroendocrine cells.

What secretions does the parietal cells secrete?

Hydrochloric acid (HCl) and Intrinsic factor.

What secretions do chief cells secrete?

Pepsinogen and Lipases

What do the enteroendocrine cells secrete?

Serotonin, histamine, somatostatin, and gastrin.

What 3 factors make up the mucosal barrier?

Thick layer of bicarbonate-rich mucus, Tight junctions between epithelial cells, Damaged epithelial cells are quickly replaced by division of stem cells.

What is gastritis?

Inflammation caused by anything that breaches stomach’s mucosal barrier.

What are peptic or gastric ulcers?

erosions in stomach wall. Most ulcers are caused by bacterium Helicobacter pylori

What does the gastric mucosa secrete and how is it regulated?

Gastric juice and regulated by neural and hormonal mechanisms.

How is gastric secretion regulated by the autonomic nervous system?

Vagus nerve stimulation increases secretion and Sympathetic stimulation decreases secretion.

How is gastric secretion regulated by hormone mechanisms?

Gastrin stimulates HCl secretion by stomach and gastrin antagonist hormones by small intestine.

What are the three phases of gastric secretion?

Cephalic (reflex) phase, Gastric phase, Intestinal phase.

Parietal cells pump H+ (from carbonic acid breakdown) into stomach lumen via H+/

K+ ATPase (proton pumps).

Factors that cause pressure to remain constant in response to filling

Receptive relaxation and Gastric accommodation.

What are the accessory organs associated with the small intestine?

Liver, gallbladder, and pancreas.

What is the liver's digestive function?

Production of bile.

What is the gallbladder's chief function?

Storage of bile.

What is the pancreas' digestive function?

Supplies most of enzymes needed to digest chyme, as well as bicarbonate to neutralize stomach acid.

What are the four primary lobes of the liver?

Right, left, caudate, and quadrate.

What does the falciform ligament do?

Suspends liver from diaphragm and anterior abdominal wall.

What is the round ligament?

Remnant of fetal umbilical vein.

What are liver lobules?

Hexagonal structural and functional units.

What are hepatocytes?

Plates of hepatocytes (liver cells) that filter and process nutrient-rich blood.

What does the portal triad contain?

Branch of hepatic artery (supplies oxygen), Branch of hepatic portal vein (brings nutrient-rich blood from intestine), Bile duct (receives bile from bile canaliculi).

What are liver sinusoids?

Leaky capillaries located between hepatic plates.

What do stellate macrophages do?

Remove debris and old RBCs.

What are the Hepatocyte functions?

Produce ~900 ml bile per day, Process bloodborne nutrients, Store fat-soluble vitamins, Perform detoxification.

What are bile salts?

Cholesterol derivatives that function in fat emulsification and absorption.

What is bilirubin?

Pigment formed from heme.

What is stercobilin?

Bacteria break down in intestine to stercobilin that gives brown color of feces.

What is the Enterohepatic circulation?

Recycling mechanism that conserves bile salts.

What is Hepatitis?

Usually viral infection, drug toxicity, wild mushroom poisoning.

What is Cirrhosis?

Progressive, chronic inflammation from chronic hepatitis or alcoholism.

What is the function of the Gallbladder?

Store and concentrate bile by absorbing water and ions.

What causes Gallstones (biliary calculi)?

Too much cholesterol or too few bile salts.

What are Acini?

Clusters of secretory cells that produce zymogen granules containing proenzymes.

What does enteropeptidase do?

Activates pancreatic protease trypsinogen to trypsin

What are the hormonal controls of bile and pancreatic secretions?

Cholecystokinin (CCK) and Secretin.

What happens when Hepatopancreatic sphincter is closed, unless digestion is active?

Bile is stored in gallbladder and released to small intestine only with contraction.