LECTURE 24 - THE DIGESTIVE SYSTEM

what are the 4 specialized subparts of the peritoneum? where is each found? what is the function of each?

-mesentery

• encircles the small intestine (except the duodenum) and anchors them to the dorsal body wall

• functions: houses blood vessels and prevents entanglement

-greater omentum

• extends between the greater curve of the stomach and the transverse colon

• functions: fat deposition, lubrication, cushioning, prevents spread of infection

-lesser omentum

• extends between the liver and lesser curvature of the stomach

• function: encloses/supports bile duct, hepatic artery, and portal vein

-mesocolon

• attached to transverse colon

• function: support the transverse colon

know the pathway through the GI tract. make sure to include the sub-regions of the small and large intestines.

• Mouth (oral cavity)

  • histology: stratified squamous epithelium

• Oropharynx —→ Laryngopharynx

  • histology: stratified squamous epithelium

• Esophagus

  • histology: stratified squamous epithelium

• Stomach

  • histology: simple columnar epithelium

• Small Intestine

  • histology: simple columnar epithelium

    • Duodenum

    • Jejunum

    • ileum

• Large Intestine

  • histology: simple columnar epithelium (no villi)

    • Cecum

    • Ascending Colon —→

    • Transverse Colon —→

    • Descending Colon —→

    • Sigmoid Colon —→

• Rectum

  • histology: stratified squamous epithelium

• Anus

  • internal sphincter —→ smooth muscle

  • external sphincter —→ skeletal muscle

what are the functions of the tongue and teeth?

-tongue

• function: skeletal muscle for speech, mastication, swallowing, and taste

-teeth

• function: organs of mastication

what are the main functions of the salivary glands/saliva? what molecule do the enzymes found in saliva digest?

functions: lubrication; primary carbohydrate digestion

breaks down starch or carbohydrates

what is the function of the esophagus? know the histology of the esophagus.

-function: initiates peristalsis to move food down to the stomach

-histology: lined with stratified squamous epithelium

• upper 1/3 = voluntary (skeletal muscle)

• lower 2/3 = involuntary (smooth muscle)

what is peristalsis?

wave like contractions

what molecules are absorbed in the stomach? what molecules are digested in the stomach?

absorbed: water, electrolytes, aspirin, and alcohol

digested: further digestion of carbohydrates and proteins

what is the histology of the lining of the stomach? how does this tissue help protect the stomach?

histology: lined with simple columnar epithelium

• secretes mucus to protect the walls from acids

what is the function of the:

• rugae

• esophageal/cardiac sphincter

• pyloric sphincter

• gastric glands

-rugae

• internal folds of mucosa

• function: allow for the stomach to expands; increases surface area

-esophageal/cardiac sphincter

• entrance to stomach

• function: prevents backflow of acidic stomach contents

-pyloric sphincter

• exit

• function: controls entry of chyme into the small intestine

-gastric glands

• function: secrete gastric juice

what do gastric glands secretes? what does this secretion break down/digest?

secretes gastric juice

• composed of hydrochloric acid and enzymes for protein digestion

where does the majority of digestion and absorption occur?

the small intestine

• primarily within the duodenum and jejunum

what are the 3 regions of the small intestine? which are suspended by the mesentery?

-duodenum: proximal

• receives chyme from the stomach and digestive enzymes from the pancreas and liver

-jejunum: middle

-ileum: distal

-the jejunum and ileum are suspended by the mesentery

be able to diagram.