GI Tract Anatomy review

What are the four layers of the GI tract (from outermost to innermost)?

Serosa, Muscularis externa, Submucosa, Mucosa.

What is the function of the serosa?

Reduces friction; outer protective layer.

What does the muscularis externa do?

Performs peristalsis and segmentation through circular and longitudinal muscle layers.

What is found in the submucosa?

Blood vessels, lymphatics, and Meissner's plexus (nerve supply).

What are rugae?

Folds in the mucosa that allow the stomach to expand.

Name the three salivary glands.

Parotid, Submandibular (Submaxillary), and Sublingual.

What enzyme does saliva contain to start digestion?

Salivary amylase.

What joint type anchors teeth in sockets?

Gomphosis.

What are the layers of a tooth?

Enamel, dentin, pulp cavity.

Name the three regions of the pharynx.

Nasopharynx, Oropharynx, Laryngopharynx.

What forms Waldeyer's ring?

Palatine, Pharyngeal, and Lingual tonsils.

What type of movement pushes food through the esophagus?

Peristalsis.

Where does the esophagus pass through the diaphragm?

Esophageal hiatus.

What type of epithelium lines the proximal and distal ends of the esophagus?

Proximal - Stratified squamous non-keratinized; Distal - Simple columnar.

Name the four regions of the stomach.

Cardia, Fundus, Body, Pylorus.

What do parietal cells secrete?

Hydrochloric acid (HCl) and intrinsic factor.

What do chief cells secrete?

Pepsinogen.

What hormone do G-cells secrete?

Gastrin.

What are the three parts of the small intestine?

Duodenum, Jejunum, Ileum.

Which section of the small intestine does most absorption occur in?

Jejunum.

What increases surface area for absorption in the small intestine?

Plicae circulares, villi, microvilli.

What is the main function of the large intestine?

Water and electrolyte absorption.

List the regions of the large intestine in order.

Cecum, Ascending, Transverse, Descending, Sigmoid, Rectum, Anal canal.

What are the main functions of the liver?

Detoxification, bile production, glycogen storage, breakdown of RBCs, and blood filtration via Kupffer cells.

What is the hepatic triad composed of?

Hepatic artery, portal vein, and bile duct.

What is the function of the gallbladder?

Stores and concentrates bile.

What causes gallstones?

Too much cholesterol and salts in bile.

What enzymes does the pancreas produce?

Pancreatic lipase, Trypsinogen, Pancreatic amylase.

What hormone does the pancreas secrete to regulate blood sugar?

Insulin.

What nerves provide parasympathetic innervation to most of the GI tract?

Vagus nerve (cranial X).

What provides parasympathetic innervation to the descending colon?

Pelvic splanchnic nerve.

What does the duodenum receive for digestion?

Pancreatic enzymes and bile.

What are the primary functions of the jejunum?

Absorption of nutrients through villi and microvilli.

What does the ileum absorb?

Remaining nutrients like bile salts and vitamin B12.

What are the functions of the stomach?

Mechanical digestion, chemical digestion with acid and enzymes, and food storage.

What is the function of mucus in the stomach?

Protects stomach lining from acid and enzymes.

Where are Meissner's and Auerbach's plexuses located?

In the submucosa (Meissner's) and muscularis (Auerbach's) layers.

What is the function of Kupffer cells in the liver?

Remove bacteria and debris from the blood.

What is the function of bile?

Emulsifies fats for digestion.

What does the pancreas' endocrine portion do?

Secretes insulin and glucagon to regulate blood sugar.

What is the main function of the colon?

Water reclamation and feces formation.

Where is the appendix located?

Attached to the cecum.

What separates the stomach from the small intestine?

Pyloric sphincter.

What separates the esophagus from the stomach?

Cardiac sphincter.

What is the function of gastric pits?

Openings to gastric glands that secrete digestive substances.

What kind of muscle contractions move food along the digestive tract?

Peristaltic contractions.

What is the purpose of villi and microvilli?

Increase surface area for absorption in the small intestine.

Which organ detoxifies alcohol and drugs?

Liver.

What stores glycogen in the digestive system?

Liver.

What produces digestive enzymes for all nutrient types?

Pancreas.

Where does most chemical digestion occur?

Duodenum.

What structure controls defecation?

Anal sphincters (internal and external).

What type of tissue lines most of the GI tract?

Simple columnar epithelium (except mouth, pharynx, esophagus).

What nerve innervates most of the GI tract for parasympathetic control?

Vagus nerve.

Which organ lies posterior to the trachea?

Esophagus.

At what point does the esophagus enter the abdominal cavity?

At the esophageal hiatus in the diaphragm.

What is the role of the pyloric sphincter?

Regulates passage of chyme from stomach to duodenum.

What happens in the fundus of the stomach?

Food storage and initial chemical digestion.

What is the function of the sigmoid colon?

Stores fecal matter before defecation.

What kind of muscle controls the internal anal sphincter?

Smooth (involuntary) muscle.

What kind of muscle controls the external anal sphincter?

Skeletal (voluntary) muscle.