digestive tract

Digestive Tract

Mouth → Pharynx → Esophagus → Stomach → Small Intestine → Large Intestine → Rectum → Anus

Accessory Organs

Teeth, tongue, salivary glands, liver, gallbladder, pancreas

Ingestion

Taking food into the mouth

Mechanical Processing

Chewing, crushing, and mixing food

Digestion

Chemical breakdown of food into smaller molecules

Secretion

Release of enzymes, acids, water, and buffers

Absorption

Movement of nutrients into blood or lymph

Defecation

Elimination of feces from the digestive tract

Peritoneum

Serous membrane lining the abdominopelvic cavity

Mesenteries

Double sheets of membrane that suspend digestive organs

Mucosa

Inner lining of the digestive tract

Submucosa

Contains blood vessels, glands, and nerves

Muscularis Externa

Smooth muscle layer that moves food

Serosa

Outer covering of digestive organs

Plicae

Permanent folds that increase absorption surface area

Villi

Fingerlike projections that increase absorption

Peristalsis

Wave-like contractions that move food forward

Segmentation

Mixing contractions that churn food

Oral Cavity

Receives food and begins digestion

Tongue

Manipulates food and contains taste receptors

Salivary Glands

Parotid, sublingual, and submandibular glands that produce saliva

Salivary Amylase

Begins carbohydrate digestion in the mouth

Incisors

Cut food

Canines (Cuspids)

Tear food

Premolars (Bicuspids)

Crush and grind food

Molars

Heavy grinding and crushing teeth

Mastication

Chewing food

Pharynx

Common passageway for food, liquid, and air

Esophagus

Muscular tube connecting pharynx to stomach

Deglutition

Swallowing

Bolus

Ball of chewed food

Stomach

Stores food and begins protein digestion

Chyme

Acidic, partially digested food mixture

Cardia

Region where esophagus enters stomach

Fundus

Upper bulging portion of stomach

Body

Main central region of stomach

Pylorus

Connects stomach to small intestine

Pyloric Sphincter

Controls flow of chyme into small intestine

Rugae

Folds in the stomach wall

Greater Omentum

Large fatty apron hanging from stomach

Lesser Omentum

Connects stomach to liver

Parietal Cells

Produce hydrochloric acid and intrinsic factor

Chief Cells

Produce pepsinogen

Intrinsic Factor

Needed for vitamin B12 absorption

Hydrochloric Acid (HCl)

Creates acidic environment for digestion

Pepsinogen

Inactive form of pepsin

Pepsin

Protein-digesting enzyme in the stomach

Duodenum

First section of small intestine

receives chyme, bile, and pancreatic secretions

Jejunum

Main site of digestion and nutrient absorption

Ileum

Last section of small intestine ending at ileocecal valve

Ileocecal Valve

Controls movement into the large intestine

Microvilli

Tiny projections that greatly increase absorption

Lacteal

Lymphatic vessel that absorbs fats

Pancreas

Produces digestive enzymes and bicarbonate

Pancreatic Juice

Alkaline secretion released into small intestine

Pancreatic Amylase

Digests carbohydrates

Pancreatic Lipase

Digests fats

Proteases

Digest proteins

Liver

Produces bile and regulates metabolism

Gallbladder

Stores and concentrates bile

Falciform Ligament

Divides left and right liver lobes

Liver Lobule

Functional unit of the liver

Hepatocytes

Liver cells

Sinusoids

Specialized capillaries in the liver

Bile

Emulsifies fats

Common Hepatic Duct

Carries bile from the liver

Common Bile Duct

Carries bile into the duodenum

Cystic Duct

Connects gallbladder to bile ducts

Hepatic Portal System

Carries nutrient-rich blood from digestive tract to liver

Emulsification

Breaking large fat droplets into smaller droplets

Secretin

Stimulates bile and bicarbonate secretion

CCK (Cholecystokinin)

Stimulates release of bile and pancreatic enzymes

GIP (Gastric Inhibitory Peptide)

Slows stomach activity and stimulates insulin release

Large Intestine

Absorbs water and stores feces

Cecum

First pouch of the large intestine

Colon

Main portion of the large intestine

Haustra

Pouches of the colon

Teniae Coli

Longitudinal muscle bands of the colon

Ascending Colon

Travels upward on the right side

Transverse Colon

Travels across the abdomen

Descending Colon

Travels downward on the left side

Sigmoid Colon

S-shaped section before the rectum

Rectum

Final segment that stores feces

Mass Movements

Strong peristaltic contractions in large intestine

Vitamin K

Produced by colon bacteria

needed for blood clotting

Biotin

Produced by colon bacteria

important for metabolism

Vitamin B5

Produced by colon bacteria

needed for steroid hormone production

Carbohydrates

Broken down into monosaccharides

Brush Border Enzymes

Break disaccharides into monosaccharides

Monosaccharides

End products of carbohydrate digestion

Proteins

Broken down into amino acids

Trypsin

Protein-digesting enzyme

Chymotrypsin

Protein-digesting enzyme

Elastase

Protein-digesting enzyme

Amino Acids

End products of protein digestion

Lipids

Broken down into fatty acids