Week 4 GI tract

What are the two primary metabolic activities supported by the digestive system?

Anabolism (building molecules) and catabolism (breaking down molecules for energy).

What are the two main components of the digestive system?

Digestive tract (GI tract) and accessory organs.

What is another name for the digestive tract?

Gastrointestinal (GI) tract or alimentary canal.

What is the primary function of the oral cavity?

Ingestion, mechanical digestion, moistening food, and mixing with saliva.

What is the function of the pharynx?

Muscular propulsion of food into the esophagus.

What is the function of the esophagus?

Transporting food to the stomach via peristalsis.

What is chyme?

A mixture of partially digested food and acidic gastric secretions.

What is the primary site of digestion and absorption?

Small intestine.

What is the primary function of the large intestine?

Water reabsorption and compaction of feces.

What is the function of the teeth?

Mechanical digestion through mastication.

What are the functions of the tongue?

Mechanical digestion, taste, touch, temperature sensation, and secretion of mucins and lingual lipase.

What is the function of the salivary glands?

Secrete saliva containing enzymes for carbohydrate digestion.

What are the major functions of the liver?

Bile production, nutrient storage, metabolic regulation, and hematological regulation.

What is the function of the gallbladder?

Stores and concentrates bile.

What are the exocrine and endocrine functions of the pancreas?

Exocrine: digestive enzymes and buffers. Endocrine: insulin and glucagon secretion.

What is ingestion?

Entry of food into the oral cavity.

What is mechanical digestion?

Physical breakdown of food into smaller pieces.

What is chemical digestion?

Chemical breakdown of food into absorbable molecules.

What is secretion?

Release of water, acids, enzymes, buffers, and salts.

What is absorption?

Movement of nutrients and water into body fluids.

What is defecation?

Elimination of feces from the body.

What tissue is responsible for GI tract motility?

Visceral smooth muscle.

What are pacesetter cells?

Cells that spontaneously depolarize and establish rhythmic contractions.

Define peristalsis.

Waves of muscular contractions that move a bolus through the digestive tract.

Define segmentation.

Mixing contractions that churn food without moving it in a specific direction.

Which type of movement primarily propels food forward?

Peristalsis.

Which type primarily mixes intestinal contents?

Segmentation.

What are the three major mechanisms regulating digestion?

Local factors, neural mechanisms, and hormonal mechanisms.

What local factors can stimulate digestion?

Changes in pH, stretching, and nutrient presence.

What chemicals can local factors stimulate?

Histamine and prostaglandins.

What is the role of the myenteric plexus?

Controls GI motility.

What are short reflexes?

Local reflexes that control small GI segments without CNS involvement.

What are long reflexes?

CNS-mediated reflexes controlling larger digestive activities.

Which salivary gland produces mainly salivary amylase?

Parotid gland.

Which salivary gland primarily produces mucus?

Sublingual gland.

Which salivary gland produces both mucins and salivary amylase?

Submandibular gland.

What enzyme begins carbohydrate digestion in the mouth?

Salivary amylase.

What enzyme begins lipid digestion in the mouth?

Lingual lipase.

What nervous system division increases salivary secretion?

Parasympathetic nervous system.

What is mastication?

Chewing.

What is deglutition?

Swallowing.

What initiates the swallowing reflex?

Stimulation of tactile receptors on the palatal arches and uvula.

What happens during the buccal phase?

Tongue pushes bolus into the oropharynx.

What happens during the pharyngeal phase?

Epiglottis closes airway and bolus enters esophagus.

What happens during the esophageal phase?

Peristalsis moves bolus toward the stomach.

What are the four regions of the stomach?

Cardia, fundus, body, and pyloric part.

What are rugae?

Folds that allow the stomach to expand.

What extra muscle layer does the stomach possess?

Inner oblique layer.

What do parietal cells secrete?

Hydrochloric acid (HCl) and intrinsic factor.

Why is intrinsic factor important?

It is required for Vitamin B12 absorption.

What do chief cells secrete?

Pepsinogen.

What converts pepsinogen into pepsin?

Hydrochloric acid.

What do G cells secrete?

Gastrin.

What does gastrin do?

Stimulates acid secretion and gastric contractions.

What do D cells secrete?

Somatostatin.

What does somatostatin do?

Inhibits gastrin release.

What triggers the cephalic phase?

Sight, smell, taste, or thought of food.

Which cranial nerve is important in the cephalic phase?

Vagus nerve (CN X).

What triggers the gastric phase?

Food entering the stomach.

What triggers the intestinal phase?

Chyme entering the duodenum.

Is the intestinal phase stimulatory or inhibitory to the stomach?

Primarily inhibitory.

What enzyme digests carbohydrates in pancreatic secretions?

Pancreatic alpha-amylase.

What enzyme digests lipids?

Pancreatic lipase.

What do nucleases digest?

RNA and DNA.

What activates trypsinogen?

Enteropeptidase.

Which pancreatic enzymes are secreted as inactive proenzymes?

Trypsinogen, chymotrypsinogen, procarboxypeptidase, and proelastase.

Approximately how many functions does the liver perform?

Over 200.

What is the hepatic portal system?

System carrying blood from the digestive tract to the liver.

What is the function of bile salts?

Emulsification of fats.

What hormone causes gallbladder contraction?

Cholecystokinin (CCK).

What hormone relaxes the hepatopancreatic sphincter?

CCK.

What percentage of nutrient absorption occurs in the small intestine?

About 90%.

What are the three regions of the small intestine?

Duodenum, jejunum, and ileum.

Which section is the major site of digestion and absorption?

Jejunum.

What is the function of brush border enzymes?

Complete digestion at the intestinal surface.

What does the gastroenteric reflex do?

Stimulates motility and secretion throughout the small intestine.

What does the gastroileal reflex do?

Opens the ileocecal valve.

What does secretin do?

Increases pancreatic buffers and bile secretion while reducing gastric motility.

What does GIP do?

Stimulates insulin release.

What does CCK do?

Stimulates pancreatic enzyme secretion and gallbladder contraction.

What does VIP do?

Stimulates intestinal glands and inhibits stomach acid secretion.

What does enterocrinin do?

Stimulates alkaline mucus production.

What are the main functions of the large intestine?

Water reabsorption, feces compaction, and vitamin absorption.

Which vitamin produced by gut bacteria is important for clotting?

Vitamin K.

What vitamin supports glucose metabolism and is produced by bacteria?

Biotin.

What causes the characteristic odor of feces?

Ammonia, indole, and skatole.

What gas causes a rotten egg smell?

Hydrogen sulfide.

Which enzymes digest carbohydrates?

Salivary amylase, pancreatic amylase, maltase, sucrase, and lactase.

What are carbohydrates ultimately absorbed as?

Monosaccharides.

What structure helps transport lipids across the intestine?

Micelles.

What are chylomicrons?

Lipid transport particles formed inside intestinal cells.

Where do chylomicrons enter circulation?

Lacteals.

What enzyme in the stomach begins protein digestion?

Pepsin.

What activates pepsinogen?

Hydrochloric acid.

How much water is reabsorbed by the small intestine daily?

About 8000 mL.

How much water is normally lost in feces daily?

About 150 mL.