Chapter 24. The Digestive System The Alimentary Canal Accessory Digestive Organs. Functions of Digestive System. Ingestion - selective intake of food. Digestion – mechanical and chemical breakdown of food into a form the body can use. Absorption – uptake of nutrients into blood and lymph.
The Digestive System
The Alimentary Canal
Accessory Digestive Organs
Auerbachs nerve plexus Meissners plexus
Three regions defined by location and function:
Nasopharynx- air passage way only: composed of -pseudostratified ciliated columnar epithelium
Oropharynx- back of oral cavity down to epiglottis:
-composed of stratified squamous epithelium.
Laryngopharynx- air passageway, food is deflected into esophagus and does not enter this region
-composed of stratified squamous epithelium
Food moves as a
bolus in segmented
manner with alternate
segments of esophagus - contracting then relaxing to move food downward.
Defined: Temporary storage tank where chemical breakdown of proteins begins and a creamy paste “chyme” is formed. pH~ 1-2.
Location-Lies in upper left quadrant of abdominal cavity, inferior to diaphragm and partially covered by the liver.
Histology: Lined with simple columnar epithelium and numerous gastric glands
Size: Varies from 15 to 25 cm. (6-10”) in length.
empty has a volume of ~ 50 ml; full capacity ~ 4 l.
- note the lacteal within the core of the microvilli
- Haustra- pocket like sacs along L.I.; result in segmentation of L.I. Churning action occurs here which turns fecal material into a sludgy paste.