Textbook Digestive System I

Question 1

In a cadaver, the alimentary canal is long, but in a living person, it is considerably shorter because of its muscle tone.

Answer 1

True

Question 2

Digestive system functions:

Answer 2

• Digest food
• Breaks it down into smaller fragments
• Absorbs digested fragments through the lining into blood or lymph
• Defecation - eliminates indigestible materials.

Question 3

Food material in this tube (alimentary canal) is technically outside the body because the canal is open to the external environment at both ends.

Answer 3

digestive glands and gallbladder lie outside the GI tract and connect to it by ducts

Question 4

The accessory digestive glands produce a variety of secretions that help break down foodstuffs.

Question 5

What major processes occur
during digestive system activity?

Answer 5

Ingestion: eating

propulsion: food through the alimentary canal, includes swallowing (voluntary),
- Peristalsis: contraction & relaxation of muscles (squeeze food along the tract, some mixing. It’s powerful even standing on your head, won’t stop it.

Mechanical breakdown/digestion: increase surface area of food increase before digestion by enzymes.
Chewing (mouth)
* Churning (stomach) * Segmentation
(small intestine) - Segmentation, a type of mixing wave, mixes food with digestive juices against the intestinal wall.

Digestion: series of steps in which enzymes secreted into the lumen (cavity) of the alimentary canal, break down complex food molecules to their chemical building blocks.

• How does a cell synthesize and store these enzymes without digesting itself? The answer is that the cell makes proenzymes, or zymogens. These are inactive forms of the enzymes that are only activated once they are released.

Absorption:
Defecation

Question 6

digestive tract as a “disassembly line” in which food becomes less complex at each step of processing until its nutrients become available to the body.

Question 7

Most digestive system organs reside in the abdominopelvic cavity.

Answer 7

ventral body cavities contain slippery serous membranes or peritoneum:

Two types of p. membranes:
- Vicsceral p.: coversexternal surface of digestive organs
- Parietal p.: lines the body wall

Btw. them is the parietal cavity - contains slippery fluid (serous) secreted by both membranes
- allows mobile digestive organs to glide easily.

Mesentery: double layer of peri- toneum. Both dorsal and ventral.
Function:
- routes for blood vessels, lymphatic, & nerves to reach digestive viscera.
- Hold organs in place
- Store fat

Question 8

Most digestive organs are intraperitoneal and are suspended from the body wall by a dorsal mesentery.

Answer 8

Some digestive organ mesenteries have specific names (such as the omenta)

Not all alimentary canal organs are suspended by a mesen- tery.

Question 9

during development, some regions of the small intestine, pancreas, large intestine, duodenum, adhere to the dorsal abdominal wall, so they lose their mesentery and lie posterior to peritoneum

Answer 9

Retroperitoneal organs

Question 10

Digestive organs (like the stomach) that keep their mesentery and are completely surrounded by the peritoneum are called intraperitoneal or peritoneal organs.

Answer 10

Peritonitis is inflammation of the peritoneum. From leaking juice, burst appendix (sprays bacteria-contained feces). often lethal.

Question 11

Some intraperitoneal digestive organs are also suspended from the body wall by ventral mesenteries.

Answer 11

Some digestive organs are retroperitoneal because they have lost their mesentery during development

Question 12

The walls of the alimen-tary canal have the same four basic layers, or tunics—mucosa, submucosa, muscularis externa, and serosa

Answer 12

The mucosa: Innermost layer, moist epithelial membrane moth to anus.
Functions:
- secret mucus, digestive enzymes, hormones (lining epithelium)
- absorb end products of digestion into blood
- Protection from infection

Sublayers:
1) a lining epithelium,
(2) a lamina propria (areolar connective tissue) - underlies the epith. nourish epith. and absorb nutrients, part of MALT (protection)
(3) a muscularis mucosae (smooth muscle cells): external to LP, local movements of mucosa (absorption & secretion)

The epithelium is usually a single layer of tall, column-shaped cells (simple columnar) in most places, but in areas with more mechanical stress (like the mouth and esophagus), the epithelium is tougher and stratified squamous (multiple flat cell layers, secretes mucus, protect digestive organs from being digested by organs.

Submucosa:

Question 13

Particularly large collections of lymphoid follicles occur within the pharynx (as the tonsils) and in the appendix.