Digestive System Overview

Digestive System Overview

• The digestive tract (alimentary canal) is a continuous tube running from the mouth to the anus.
• It includes the mouth, pharynx, esophagus, stomach, small intestine, and large intestine.
• Accessory organs include teeth, tongue, salivary glands, liver, gallbladder, and pancreas.

Digestive Processes

• Digestion involves mechanical and chemical breakdown of food.
• Mechanical digestion involves physical processes like chewing and stomach churning.
• Chemical digestion uses enzymes to break down large molecules into smaller ones.
• Absorption is the uptake of nutrients into the blood or lymph.
• Metabolism is the breakdown of food into basic nutrients, using the energy for bodily functions.

Mouth: Structure and Function

• The mouth is the entrance to the digestive tract.
• The hard palate separates the oral cavity from the nasal cavity.
• The soft palate and uvula help prevent food from entering the nasal passages.
• The tongue helps with chewing, tasting, and swallowing.
• Teeth are used for tearing and grinding food.

Salivary Glands

• Salivary glands secrete saliva.
• Saliva moistens and lubricates food, aiding in swallowing.
• Saliva contains enzymes that begin to break down starches.

Pharynx

• The pharynx is a common passageway for air and food.

Esophagus

• The esophagus is a muscular tube connecting the pharynx to the stomach.
• Peristalsis moves food through the esophagus.

Stomach

• The stomach stores and mixes food with gastric juices.
• The stomach has folds called rugae to allow expansion.
• The stomach has three layers of muscle to mix and churn food.
• An acidic environment in the stomach helps break down proteins with pepsin.

Small Intestine

• The small intestine is where most digestion and absorption occur.
• The small intestine is divided into three sections (duodenum, jejunum, and ileum).
• It has villi and microvilli to greatly increase surface area for absorption.

Large Intestine

• The large intestine absorbs water and electrolytes and prepares waste products for elimination.
• The colon is the main part of the large intestine.
• The cecum is the first part of the large intestine.
• The appendix is a small, tube-like structure attached to the cecum.

Liver

• The liver produces bile, which aids in fat digestion and absorption.
• Bile is stored in the gallbladder.
• The common bile duct carries bile to the small intestine.

Pancreas

• The pancreas produces enzymes important in digestion.
• Pancreatic enzymes aid in the chemical breakdown of proteins, carbohydrates, and fats.
• Insulin and glucagon are released into the bloodstream to regulate blood sugar levels.

Mesentery and Greater Omentum

• The mesentery helps hold the intestines in place.
• The greater omentum is a fatty apron-like structure that covers the abdominal organs.

Additional Notes: Order of Small & Large Intestines

• Order of small intestine: Duodenum, Jejunum, Ileum
• Order of large intestine: Cecum, Ascending colon, Transverse colon, Descending colon, Sigmoid colon, Rectum, Anus.

Accessory Organs

• Teeth, tongue, salivary glands, liver, gallbladder, and pancreas play important roles in digestion.