Biology 212Anatomy & Physiology I

Dr. Thompson

Digestive System

Functions:

Organs

Two functional groups:

1. Alimentary Canal or Gastrointestinal tract

2. Accessory Digestive Organs

Organs:

Oral Cavity:

Paired Salivary Glands:

Saliva:

97% - 99% waterSolutes:

Swallowing

From esophagus to anus: 4 concentric layers or tunics

Alimentary Canal:

Esophagus:

Propels food from pharynx to stomachPosterior to trachea & heart

Mucosa:

Submucosa:

Muscularis Externa:

Adventitia:

Esophagus:

Passes from thorax to abdomen through diaphragm, enters stomach (left of midline).

Stomach:

Storage: Highly distensible Delivers slowly to duodenum Secretion of mucous, hydrochloric acid Secretion of enzyme - Digestion of proteins Secretion of enzyme - Digestion of lipids Secretion of enzyme - Absorption of B12

Stomach:

Stomach:

Small Intestine: Total length: 6 to 7 metersDiameter: 2.5 to 3 centimeters

Small Intestine:

Duodenum

Jejunum

Ileum

Small Intestine:

DUODENUM: Receives Secretes

JEJUNUM:

ILEUM:

Small Intestine:

Small Intestine:

Mucosa specialized three ways to increase surface area for absorption

Large Intestine (colon):

From ileocecal junction to anus~ 2 meters long~ 5 to 8 cm diameter

Abdominal Accessory Organs:

Liver

Liver

Digestive functions:

Liver:

Pancreas:

Pancreas:

Produces many different digestive enzymes:

Amylases: starches & monosaccharides glycogen & disaccharides

Proteases: proteins amino acids

Lipases: diglycerides & fatty acids triglycerides & glycerol

Nucleases: nucleic acids nucleotides

The abdominal cavity is lined by a double-layered serous membrane

More terminology:

Intraperitoneal Retroperitoneal

Intestinal Motility:

Moves liquid distally

Digestion:

Breakdown of food into molecules small enough to be absorbed from the lumen of the intestine into its blood vessels.

Four types of molecules = more than 95% of total:

Also: Nucleic acids Ions (electrolytes, minerals) Vitamins ? Others ?

Mechanical digestion

Chemical digestion

Absorption of nutrients electrolytes vitamins

Absorption of water

All absorbed molecules

Since contents include many foreign substances, including microorganisms, your immune system considers it “outside”

so

Lined by many lymphatic and immune tissues in lamina propria and submucosa

Alimentary Canal: