OIA1004 GASTROINTESTINAL SYSTEM I

What are the six basic processes of the digestive system?

Ingestion, secretion, mixing and propulsion, digestion (mechanical and chemical), absorption, and defecation.

What is the gastrointestinal (GI) tract?

A continuous muscular tube extending from the mouth to the anus, including the stomach, intestines, and associated organs.

Name the accessory organs of the digestive system.

Salivary glands, liver, gallbladder, and pancreas.

What is mechanical digestion?

Physical breakdown of food by chewing, churning, and mixing, preparing it for chemical digestion.

What is chemical digestion?

The breakdown of food molecules into smaller molecules by enzymatic hydrolysis.

Where does most nutrient absorption occur?

In the small intestine.

What is the enteric nervous system (ENS)?

Known as the "brain of the gut," it controls GI tract motility and secretions via the myenteric and submucosal plexuses.

How does the autonomic nervous system regulate the GI tract?

The parasympathetic system stimulates digestion, while the sympathetic system inhibits it.

What is the role of the myenteric plexus?

It controls GI motility.

What are the functions of saliva?

Lubrication, moistening, chemical digestion (salivary amylase), and antibacterial action.

What enzyme in saliva begins carbohydrate digestion?

Salivary amylase.

What is a bolus?

A soft, flexible mass of food mixed with saliva, ready for swallowing.

What are the functions of the stomach?

Mixing food, storing food temporarily, secreting gastric juice, and initiating protein digestion.

What is the composition of gastric juice?

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

What is the function of HCl in the stomach?

Kills microbes, denatures proteins, activates pepsinogen to pepsin, and stimulates secretion of digestive hormones.

What are the two functions of the pancreas?

Exocrine function (secretion of digestive enzymes and bicarbonate) and endocrine function (secretion of insulin and glucagon).

What does pancreatic juice contain?

Sodium bicarbonate, amylase, lipase, proteases (trypsin, chymotrypsin), and nucleases.

What is the role of bicarbonate in pancreatic juice?

Neutralizes acidic chyme and creates an alkaline environment for enzymes in the small intestine.

What are the functions of the liver?

Bile production, metabolism of carbohydrates, lipids, and proteins, detoxification, vitamin storage, and synthesis of plasma proteins.

What is the function of bile salts?

Emulsification of fats to aid in digestion and absorption.

What is the role of the gallbladder?

Stores and concentrates bile.

What are the three parts of the small intestine?

Duodenum, jejunum, and ileum.

What structures increase the surface area of the small intestine for absorption?

Circular folds, villi, and microvilli.

What are brush-border enzymes?

Enzymes on the surface of microvilli that aid in the digestion of carbohydrates, proteins, and nucleic acids.

What are the main functions of the large intestine?

Absorption of water and electrolytes, bacterial fermentation, and formation and storage of feces.

What is haustral churning?

A type of mechanical digestion where haustra sequentially contract to mix and propel contents.

How does the large intestine contribute to vitamin production?

Gut bacteria synthesize vitamins B and K.

What triggers the defecation reflex?

Stretching of the rectum by feces.

What is gastroesophageal reflux disease (GERD)?

A condition where stomach acid refluxes into the esophagus, causing heartburn.

What causes constipation?

Reduced intestinal motility, leading to excessive water absorption and hard stools.