OIA1004 (TERMS) GASTROINTESTINAL SYSTEM

Gastrointestinal Tract

Continuous muscular tube from mouth to anus.

Accessory Digestive Organs

Organs aiding digestion, e.g., liver, pancreas.

Ingestion

Taking food into the gastrointestinal tract.

Secretion

Release of digestive fluids into GI lumen.

Mixing and Propulsion

Churning and moving food through GI tract.

Digestion

Breakdown of food into smaller molecules.

Mechanical Digestion

Physical breakdown of food, e.g., chewing.

Chemical Digestion

Enzymatic breakdown of food molecules.

Absorption

Transfer of nutrients into blood and lymph.

Defaecation

Elimination of waste products from the body.

Peristalsis

Wave-like muscle contractions moving food forward.

Segmentation

Rhythmic contractions mixing food in intestines.

Gastric Juice Composition

Includes acid, enzymes, and buffers for digestion.

Small Intestine

Primary site for nutrient absorption.

Enteric Nervous System

Intrinsic nervous system controlling GI functions.

Myenteric Plexus

Controls GI motility and muscle contractions.

Submucosal Plexus

Regulates secretions in the GI tract.

Autonomic Nervous System

Extrinsic control affecting GI activity.

Parasympathetic Nervous System

Stimulates digestive processes and secretion.

Sympathetic Nervous System

Inhibits digestive activity and secretion.

Neural Reflex Pathways

Responses initiated by stimuli affecting digestion.

Motility

Capability of GI tract to mix and move material.

GIT Length

Approximately 5 to 7 meters long.

Oral Cavity

Space from gums and teeth to fauces.

Salivary Glands

Secrete saliva into oral cavity.

Extrinsic Salivary Glands

Three pairs of glands outside the oral cavity.

Intrinsic Salivary Glands

Small glands scattered throughout oral mucosa.

Mucous Cells

Secrete viscous mucus in saliva.

Serous Cells

Produce watery secretion with enzymes.

Parotid Gland

Contains only serous cells.

Submandibular Gland

Has equal serous and mucous cells.

Sublingual Gland

Primarily composed of mucous cells.

Composition of Saliva

99.5% water, 0.5% electrolytes and enzymes.

Salivary Amylase

Enzyme that breaks down starches.

Electrolytes in Saliva

Activate amylase and buffer acidic foods.

Lysozyme

Antibacterial compound found in saliva.

Control of Salivation

Regulated by autonomic nervous system.

Parasympathetic Stimulation

Increases saliva secretion for lubrication.

Sympathetic Stimulation

Decreases saliva, causing dry mouth.

Lingual Frenulum

Secures tongue to floor of mouth.

Extrinsic Tongue Muscles

Maneuver food and hold tongue position.

Intrinsic Tongue Muscles

Alter tongue shape for speech and swallowing.

Teeth

Accessory organs for chewing food.

Dentin

Calcified tissue providing tooth shape and rigidity.

Bolus

Soft mass of food ready for swallowing.

Monosaccharides

Simple sugars absorbed directly into bloodstream.

Lactose

Disaccharide sugar found in milk.

Fructose

Fruit sugar, a type of monosaccharide.

Lingual Lipase

Enzyme that breaks down triglycerides in mouth.

Pharynx

Common passage for digestive and respiratory systems.

Nasopharynx

Part of pharynx for respiration only.

Oropharynx

Part of pharynx for digestion and respiration.

Laryngopharynx

Part of pharynx for digestion and respiration.

Peristalsis

Muscular contractions propelling food to esophagus.

Oesophagus

Muscular tube transporting food to stomach.

Upper Oesophageal Sphincter (UES)

Regulates food movement from mouth to esophagus.

Lower Oesophageal Sphincter (LES)

Regulates food movement from esophagus to stomach.

Deglutition

Swallowing process involving multiple muscle groups.

Buccal Phase

Voluntary phase of swallowing using tongue.

Pharyngeal Phase

Involuntary phase triggered by tactile receptors.

Esophageal Phase

Involuntary phase moving bolus to stomach.

Stomach

J-shaped organ mixing food and gastric juices.

Chyme

Semi-liquid mixture of food and gastric juice.

Gastric Juice

Digestive fluid containing HCl and enzymes.

Intrinsic Factor

Protein necessary for vitamin B12 absorption.

Gastrin

Hormone stimulating gastric acid secretion.

Mucous Neck Cells

Secrete alkaline mucus protecting stomach lining.

Chief Cells

Produce pepsinogen, inactive form of pepsin.

Parietal Cells

Secrete hydrochloric acid (HCl) in stomach.

B12 absorption

Process of absorbing vitamin B12 in intestines.

Pepsinogen

Inactive enzyme converted to pepsin for protein digestion.

Pepsin

Active enzyme that breaks down proteins into peptides.

Gastric Lipase

Enzyme that digests triglycerides into fatty acids.

Gastrin hormone

Hormone that stimulates gastric acid secretion.

Mechanical digestion

Physical breakdown of food via muscular contractions.

Mixing waves

Peristaltic movements mixing food with gastric juice.

Chyme

Semi-liquid mixture of food and gastric juices.

Pylorus

Region regulating chyme passage to the duodenum.

Peristaltic waves

Rhythmic contractions moving food toward pylorus.

Chemical digestion

Breakdown of food by enzymes and acids.

HCl

Hydrochloric acid aiding digestion and killing microbes.

Parietal cells

Cells secreting H+ and Cl- to form HCl.

Proton pump

Transport mechanism secreting H+ ions into lumen.

ACh

Neurotransmitter stimulating gastric acid secretion.

Gastric juice

Digestive fluid containing enzymes and acids.

Pancreatic juice

Digestive fluid secreted by pancreas into intestines.

Sodium bicarbonate

Buffers gastric juice, creating alkaline pH.

Pancreatic amylase

Enzyme digesting starches into simpler sugars.

Trypsin

Enzyme breaking down proteins into peptides.

Hepatocytes

Liver cells performing metabolic and secretory functions.

Islets of Langerhans

Endocrine cells in pancreas secreting hormones.

Ribonuclease

Enzyme digesting RNA into nucleotides.

Deoxyribonuclease

Enzyme digesting DNA into nucleotides.

Bile canaliculi

Ducts collecting bile between hepatocytes.

Common hepatic duct

Bile duct from liver merging with cystic duct.

Cystic duct

Duct connecting gallbladder to common bile duct.

Common bile duct

Duct transporting bile to the duodenum.

Hepatic sinusoids

Capillaries between hepatocytes for blood exchange.

Hepatic artery

Supplies oxygenated blood to the liver.

Hepatic portal vein

Carries nutrient-rich blood to the liver.