The Digestive System

Do a basic organ trace of food from the environment to the toilet.

1. Oral cavity

2. oropharynx

3. laryngopharynx

4. esophagus

5. stomach

   1. fundus

   2. body of stomach

   3. pyloric part

   4. pyloric sphincter

6. small intestine

7. large intestine

8. rectum/anal canal

Tunica mucosa

1. simple columnar epithelium

2. lamina propria— vascular loose connective tissue

3. muscularis mucosae— thin, smooth muscle and connective tissue

4. submucosal layer— vascular, loose connective tissue with elastin

muscular layer

1. circular layer

2. longitudinal layer

Both have smooth muscle and connective tissue

• having two layers of muscle helps move the chyme through the digestive system

Tunica serosa

Mesothelium: thin, squamous epithelial layer

• Secretes slippery fluid to help slide and protect

Sphincters

a thickening of muscle, so much that it can pinch the tube off to stop flow

Peristalsis

Means to move things through a tube

• describes the coordinated muscle contractions in the muscular layer— muscle fibers running in both directions

Why does the tunica mucosa have those little fingers?

Those fingers exist to increase surface area. Usually, tubes branch to increase surface area, but this one can’t do that.

Function of the digestive tube?

transport

cardia

fundus

body of stomach

pylorus

bottom part of stomach

greater curvature

top part of stomach

lesser curvature

gastric rugae/folds

What kind of muscle fibers are in the stomach wall?

1. circular

2. longitudinal

3. oblique— fibers running in irregular directions

Function of the stomach?

storage

pyloric sphincter

Duodenum

Jejunum

Ilium

liver

What is this and what does it do?

gallbladder; bile storage

What is this and what does it do?

Extrahepatic bile ducts; transport bile

What is this and what does it do?

Pancreas

• exocrine: secretes digestive enzymes

• endocrine: regulates blood sugar

Order of the small intestines:

1. Duodenum

2. Jejunum

3. Ileum

Why is the pancreas so important for the digestive system?

It is responsible for almost all of the metabolic regulation and digestive enzymes

Tube design of the mucosa of the small intestine

1. epithelium

2. lamina propria

3. muscularis mucosae

4. submucosa

muscular layer of small intestine:

1. circular layer

2. longitudinal layer

**one of the only places we’ve learned where circular is more inside

So far, where do had a serosa rather than adventitia?

Digestive system (not esophagus) & heart wall

**mesothelium

caecum

vermiform appendix

what is the order of the large intestine?

1. caecum

2. ascending colon

3. transverse colon

4. descending colon

5. sigmoid colon

6. rectum

How does the large intestine increase surface area, and why?

The large intestine has semilunar folds that absorb water and thicken the consistency of the fecal matter.

What changes happen to the tubular design of the large intestine?

• Mucosa remains the same

• Muscular layer:

  • the circular layer remains the same

  • the longitudinal layer bunches together to create taeniae coli, which are bands of muscle fibers that are in the middle of the large intestine

  • the contractions of the colon create haustra (the bumps)

• Serosa gains fatty appendages

function of the large intestine?

storage and water absorption

function of the small intestine?

nutrient absorption and digestion