Digestive System Flashcards
List the main functions of the digestive system.
Ingestion
Secretion
Mixing and propulsion
Digestion
Absorption
Defecation
Describe the layers of the digestive tract.
The GI tract contains 4 layers:
- Muscosa = Innermost layer
- Submucosa = A secretory layer, a thick layer of loose connective tissue that surrounds the mucosa.
- Muscular propria = smooth muscle layer
- Adventitia = Outermost layer
Identify the locations of the nine abdominal regions.
1 = Epigastric
2 = Umbilical
3 = Hypogastric
4 = Hypochondriac
5 = Lumbar
6 = Iliac (hypogastric)
Describe the structure and function of the salivary glands.
Structure = branched ducts that open into the oral cavity
Function =
releases saliva in the mouth
moistens food
makes it easier to swallow
contains amylase to digest carbs
Identify the voluntary and involuntary processes involved in swallowing (act of
deglutition).
Oral phase – voluntary, movement of the bolus from the oral cavity into the oropharynx.
Pharyngeal phase – involuntary, movement of the bolus from the oropharynx into the esophagus.
Esophageal phase – involuntary, movement of the bolus through the esophagus and into the stomach
Describe the physiology of defecation.
the act of expelling faeces from the digestive tract via the anus.
Define Ingestion
Taking food in the mouth, with mechanical and chemical digestion.
Define Secretion
It is the release of water, acids, enzymes, buffers, and. salts. – By epithelium of the digestive tract.
Define Mixing and propulsion
Mixing movements occur in the stomach as a result of smooth muscle contraction.
These repetitive contractions usually occur in small digestive tract segments and mix the food particles with enzymes and other fluids.
The movements that propel the food particles through the digestive tract are called peristalsis.
Define Absorption
The simple molecules that result from chemical digestion pass through cell membranes of the small intestine’s lining into the blood or lymph capillaries. This process is called absorption.
Define Elimination
Elimination
The food molecules that cannot be digested or absorbed must be eliminated from the body. The removal of indigestible wastes through the anus, in the form of faeces, is defecation or elimination.
What is the function of the oesophagus?
To allow for the passage of material from the mouth and throat to the stomach.
What is the function of the stomach?
Holds the food and mixes it with acid and enzymes that continue to break the food down into a liquid or paste.
What is the function of the duodenum?
Food mixes with bile from the gallbladder and digestive juices from the pancreas. The absorption of vitamins, minerals, and other nutrients begins in the duodenum.
What is the function of the jejunum?
to absorb sugars, amino acids, and fatty acids.
What is the function of the ileum?
it absorbs any final nutrients
What is the function of the large colon?
absorbing water and electrolytes,
producing and absorbing vitamins,
forming and propelling feces toward the rectum for elimination.
What is the function of the rectum?
Excertion
Describe the structure and function of the Pancreas.
located inside your abdomen, just behind your stomach.
During digestion, your pancreas makes pancreatic juices called enzymes. These enzymes break down sugars, fats, and starches.
Describe the structure and function of the Liver.
Located beneath the rib cage in the right upper abdomen.
Removes toxins from the body’s blood supply, maintains healthy blood sugar levels, regulates blood clotting, and performs hundreds of other vital functions.
Describe the structure and function of the Gall bladder.
It is a muscular organ that contracts when bile is needed, and forces the enzyme through the cystic duct.
Located underneath the right lobe of the liver.
What are liver cells called?
hepatocytes
What does the hepatic artery do
brings oxygenated blood from the heart (from the aorta) into the liver
supplies the O2 for aerobic respiration
What does the hepatic portal vein do?
brings deoxygenated blood from the digestive system which is rich in the products of digestion.
What does the liver do, and why is its role important?
The blood, returning from the digestive system, may contain toxic compounds that have been absorbed from the intestine - it’s important these substances don’t continue to circulate around the body before their concentrations have been adjusted
(The liver filters blood)
Where does blood leave the liver?
through the hepatic vein - rejoins the vena cava
What is bile?
Bile is a fluid secreted by the liver and stored in the gallbladder. Bile helps with digestion, breaking down fats into fatty acids in the small intestine so they can be absorbed.
What does bile contain
some excretory products e.g. bile ligaments like bilirubin - leaves the body with faeces
What is the biliary tree?
The biliary tree is a system of vessels that directs secretions from the liver, gallbladder and pancreas through a series of ducts into the duodenum.
Where does the digestion of Disaccharides and Polysaccharides start?
Digestion of Disaccharides and Polysaccharides:
Mouth:
Salivary Amylase: Begins the breakdown of starches into smaller polysaccharides and maltose (a disaccharide).
Where does the Digestion of Lipids occur?
Digestion of Lipids:
Small Intestine: Emulsification by Bile: Bile salts from the liver/gallbladder emulsify fats, breaking large fat globules into smaller droplets and aiding digestion.
Pancreatic Lipase: Released by the pancreas into the small intestine, breaks down triglycerides (fats) into fatty acids and glycerol.
Where does the Digestion of Proteins start?
Digestion of Proteins:
Stomach:
Pepsin: Produced by stomach glands as pepsinogen and activated by stomach acid (HCl) into pepsin. It begins the breakdown of proteins into smaller peptide chains.
9.2 Identify the three phases of gastric secretion.
The cephalic phase
The gastric phase
The intestinal phase
What is the cephalic phase?
The cephalic phase of gastric secretion – The sense of thought, taste, smell, the sight of food, and swallowing activates the cephalic phase. It is mediated mostly by cholinergic/vagal mechanisms.
What is the gastric phase?
The vagus nerve and the release of gastrin mediate the gastric secretion phase.
What is the intestinal phase?
The intestinal phase of gastric secretion – involves complex stimulatory and inhibitory processes.
Describe the roles of the hormone secretin in digestion.
Secretin has 3 main functions: regulation of gastric acid, regulation of pancreatic bicarbonate, and osmoregulation.
Describe the role of the hormone cholecystokinin in digestion.
When fats and proteins enter your small intestine, cholecystokinin triggers your gallbladder and pancreas to contract. They deliver bile and enzymes to your duodenum to help break down the food for absorption.
