Digestive System

Organs

Teeth

Tongue

Esophagus

Stomach

Small & Large Intestines

Liver

Gallbladder

Pancreas

Gastrointestinal

The organs that take in food and liquids and break them down into substances that the body can use for energy, growth, and tissue repair

Ingestion

Taking in food (eating)

• Food is brought into the mouth

• mastication

Digestion

biomolecule polymers break down into building blocks

• Mechanical: physically breaking down food into smaller particles 

• Chemical: enzymes break down nutrients into smaller molecules (salivary amylase: carbs & lingual lipase: fats; digestive enzymes)

Epiglottis

flap that covers the trachea during swallowing so food does not enter the lungs

Peristalsis

involuntary constriction and relaxation of the esophagus, creating wave-like movements to push contents down the canal

Segmentation

adjacent portions of the digestive tract contract and relax to move the chyme

Stomach

can store approximately. 2 liters of food and liquids

• Mechanical: 

  • Churning of the stomach: bathes contents in gastric juices

  • Chyme: pulpy acidic fluid which passes from the stomach into the small intestine

• Chemical: 

  • Hydrochloric Acid (HCl): strong acidic solutions of the gas hydrogen chloride in water

  • Pepsin: Chief digestive enzyme in the stomach that breaks down proteins into polypeptides

Lower Esophageal sphincter

separates the esophagus from the stomach

Pyloric Sphincter

separates the stomach from the small intestine

Duodenum

shortest segment of the small intestine

• Chemical digestion of chyme: enzymes from pancreas and bile from liver

• Breaks down fats, proteins, and carbs

• Absorbs iron and other minerals

Jejunum

middle segment of the small intestine

• Absorption of nutrients

• Carbohydrates and proteins are absorbed into the bloodstream

Ileum

final segment of the small intestine

• Absorption of nutrients

• Vitamin B12, Bile salts, and products of digestion are absorbed

Villi

tiny hair-like projections that line the intestines and help with absorption into the bloodstream

Ascending colon

first segment of large intestine (right side)

• Absorbs water and salts

• Solidify waste formed into stool

Transverse colon

longest most mobile part of the large intestine

• Storage site for digested food

• More absorption of water and salts

Descending colon

descending segments of the large intestine

• Carries solid waste towards the rectum

• More absorption of water and minerals

• Stores feces until defecation

Rectum

final segment of the large intestine

• Stores feces until they are expelled through the anus

Liver

Carbohydrate and protein metabolism

Creates bile to help with the breakdown of lipids in small intestine

Gallbladder

Stores the bile produced by liver

Bile

Emulsifies fats

Pancreas

Produces pancreatic juices that help neutralize chyme

Gastrin

found in the G cells of the stomach

• Stimulate gastric glands to secrete pepsinogen and HCl

Cholecystokinin

found in the I cells of the duodenum and jejunum

• Digests fats and proteins and stimulates the gallbladder to release bile

Secretin

found in the S cells of the duodenum

• Regulates pH by inhibiting gastric acid secretion and stimulating bicarbonate production

Insulin

found in the beta cells of pancreas

• Glucose metabolism and stores glucose as glycogen

• Uptake of glucose into cells = lowers blood glucose levels

Glucagon

found in the alpha cells of pancreas

• Raises blood glucose levels

• Stimulating liver to break down stored glycogen into glucose and release into bloodstream