Biology 322Human 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:

From esophagus to anus: Alimentary Canal:

Esophagus:

Propels food from pharynx to stomachPosterior 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 metersDiameter: 2.5 to 3 centimeters

Small Intestine: Three parts

Small Intestine:

Mucosa Epithelium Lamina propria Muscularis mucosa

Submucosa

Muscularis Externa

Serosa or Adventitia

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:Abdominal Accessory Organs:

Liver,

Gall bladder,

Pancreas,

& associated ducts

Four lobesBlood supply:

Liver

Most superior organ in abdomenImmediately inferior to diaphragmPartially protected by ribsDevelops from embryonic intestineMass ~ 1.5 kg

Liver:

Enter / exit together on inferior surface

Pancreas:

Inferior & posterior to stomachFits into concavity of duodenum

The abdominal cavity is lined

More terminology:

Intraperitoneal Retroperitoneal