Biology 201
Human Anatomy I
Digestive System
Functions:
Organs
Two functional groups:
1. Alimentary Canal or Gastrointestinal tract
Organs which ingest, propel, digest, absorb, & eliminate
Oral cavity, pharynx, esophagus, stomach,
small intestine, large intestine, anus
2. Accessory Digestive Organs
Assist with digestion
Teeth, tongue, salivary glands,
liver, gall bladder, pancreas
Organs:
Oral Cavity:
Includes:
Opens
Which
Three Pairs of Salivary Glands:
Alimentary Canal: From esophagus to anus:
Esophagus:
Propels food from pharynx to stomach
Posterior to trachea & heart
: Nonkeratinized stratified squamous epithelium
Many mucous-secreting cells
Thin lamina propria
Thin muscularis mucosa
: Thick layer of dense irregular CT
: Upper third = skeletal muscle
Middle third = mixed
Lower third = smooth muscle
Thin layer of connective tisssue
Esophagus:
Passes from thorax to abdomen through diaphragm, enters
stomach (left of midline).
Stomach:
Storage: Highly distensible
Delivers
Stomach
Stomach: Regions
Stomach:
Stomach:
Stomach:
Small Intestine: Total length: 6 to 7 meters
Diameter: 2.5 to 3 centimeters
Small Intestine: Three parts
Small Intestine:
Serosa or Adventitia
Muscularis Externa
Submucosa
Mucosa
Epithelium
Lamina propria
Muscularis mucosa
Small Intestine:
Mucosa specialized three ways to increase surface area
for absorption
1. All layers of mucosa thrown into
folds called
Small Intestine:
Mucosa specialized three ways to increase surface area
for absorption
2. Epithelium and
lamina propria
form finger-like
Small Intestine:
Mucosa specialized three ways to increase surface area
for absorption
3. Plasma
membranes
of epithelial
cells form
finger-like
Small Intestine:
Nutrients,
ions, etc.
are absorbed
through
these plasma
membranes & passed
through the cell to the
deeper lamina propria,
where they are
absorbed into
capillaries & lymphatic
vessels.
Large Intestine (colon):
From ileocecal junction to anus
~ 2 meters long
~ 5 to 8 cm diameter
Abdominal Accessory Organs:
Liver,
Gall bladder,
Pancreas,
& associated ducts
Liver
Most superior organ in abdomen
Immediately inferior to diaphragm
Partially protected by ribs
Develops from embryonic intestine
Mass ~ 1.5 kg
Four lobes
Blood supply:
Liver:
Enter / exit together on inferior surface
Pancreas:
Inferior & posterior to stomach
Fits into concavity of duodenum
The abdominal cavity is lined
More terminology:
Intraperitoneal Retroperitoneal