Transcript Biology 211 Anatomy & Physiology I

Biology 212
Anatomy & 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% water
Solutes:
Swallowing
Alimentary Canal:
From esophagus to anus:
4 concentric layers or tunics
Esophagus:
Propels food from pharynx to stomach
Posterior 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 meters
Diameter: 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 &
glycogen
monosaccharides
& disaccharides
Proteases:
proteins
amino acids
Lipases:
diglycerides &
triglycerides
Nucleases: nucleic acids
fatty acids
& glycerol
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
Alimentary Canal:
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