Overview of the Human Digestive System ( chapter 25 )

Ingestion

Taking in food.

Mastication (Mechanical Digestion)

Chewing food to break it down.

Chemical Digestion

Enzymatic breakdown of food into smaller molecules.

Absorption

Nutrients move into the blood.

Elimination (Excretion)

Removal of undigested waste (feces).

Alimentary Canal

Main digestive tract — oral cavity → pharynx → esophagus → stomach → small intestine → large intestine → rectum → anus.

Peristalsis

Wave-like muscle contractions that move food through the digestive system.

Protein Digestion

Begins in the stomach.

Nutrient Absorption

Occurs mainly in the small intestine (longest part).

Water Absorption

Happens in the large intestine.

Salivary Glands

Release saliva; salivary amylase starts breaking down carbohydrates.

Liver

Produces bile to help digest fats.

Gallbladder

Stores and releases bile into the small intestine.

Pancreas

Secretes digestive enzymes and regulates blood sugar (endocrine function).

Pepsin

Enzyme that breaks down proteins in the stomach; activated by low pH.

Salivary Amylase

Enzyme that starts starch (carbohydrate) breakdown in the mouth.

Bile

Emulsifies (breaks apart) lipids in the small intestine.

Cardiac Sphincter

Valve between esophagus and stomach; prevents acid reflux.

Pyloric Sphincter

Valve between stomach and small intestine; controls food flow.

Ileocecal Sphincter

Valve between small intestine and large intestine.

Bolus

Name for chewed food as it moves down esophagus.

Chyme

Partially digested, acidic food mixture in the stomach.

GERD (Acid Reflux)

Stomach acid flows into esophagus; causes heartburn.

Ulcers

Open sores often caused by Helicobacter pylori bacteria.

Crohn's Disease

Inflammatory bowel disease affecting the small intestine.

Appendicitis

Inflammation of the appendix; often requires surgery.

Diverticulitis

Infection of small pouches (diverticula) in the colon.

Pancreatitis

Inflammation of the pancreas; causes severe abdominal pain.

Celiac Disease

Autoimmune reaction to gluten damaging the small intestine.

Colon Cancer

Symptoms include blood in stool and changes in bowel habits.

Jaundice

Yellowing of skin and eyes due to liver problems.

Halitosis

Chronic bad breath from poor oral hygiene.

Mucosa Layer

Inner lining; secretes enzymes and absorbs nutrients.

Submucosa Layer

Connective tissue with blood vessels; supports mucosa.

Muscular Layer

Smooth muscle that causes peristalsis (movement).

Serosa Layer

Outer protective layer; reduces friction with surroundings.

Mouth (Digestion Step)

Chewing and salivary amylase begin carbohydrate digestion.

Pharynx/Esophagus (Digestion Step)

Swallowing; peristalsis moves food to stomach.

Stomach (Digestion Step)

Protein digestion starts; food churned mechanically.

Small Intestine (Digestion Step)

Most chemical digestion and nutrient absorption; bile emulsifies fats.

Large Intestine (Digestion Step)

Water absorbed; feces formed.

Rectum/Anus (Digestion Step)

Stores and releases waste.

Rectum & Anus

Final structures in the digestive tract responsible for waste excretion.

Pancreas

An accessory organ that secretes digestive enzymes and has endocrine functions.

Submucosa Layer

Connective tissue layer with blood vessels supporting the mucosa.

Muscular Layer

Smooth muscle responsible for peristalsis and movement of food.