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Question 1

Function of the digestive system?

Answer 1

Takes in food, breaks it down into nutrient molecules, absorbs these molecules, rids the body of indigestible remains.

Question 2

Organs of the alimentary canal/digestive tract?

Answer 2

Mouth, pharynx, esophagus, stomach, small intestine, large intestine

Question 3

Accessory structures?

Answer 3

Teeth, tongue, gallbladder, salivary glands, liver, pancreas

Question 4

What are the major processes occurring in the digestive system?

Answer 4

Ingestion, propulsion, mechanical breakdown, digestion, absorption, defacation

Question 5

Ingestion

Answer 5

Taking food into the digestive tract

Question 6

Propulsion/motility

Answer 6

Moving of food through the alimentary canal - peristalsis, swallowing

Question 7

Mechanical breakdown/digestion

Answer 7

Physical process of preparing food for chemical digestion - chewing, mixing, churning, segmentation

Question 8

Digestion (chemical)

Answer 8

Series of catabolic steps in which complex food molecules are broken down to their chemical building blocks - enzymes, acid, bile, etc.

Question 9

Absorption

Answer 9

Passage of digested end products from the lumen of the GI tract through the mucosal cells into blood or lymph.

Question 10

Defacation/elimination

Answer 10

Eliminates indigestible substances from the body via the anus as feces.

Question 11

Peristalsis

Answer 11

Alternating waves of contraction and relaxation of muscles in the organ walls. Esophagus, stomach, small/large intestine.

Question 12

Segmentation

Answer 12

Nonadjacent segments of alimentary tract alternately contract and relax moving food forward and backward.

Question 13

Digestive activities are triggered by? Detected by?

Answer 13

Mechanical and chemical stimuli (i.e. stretching of organ by food, osmolarity, pH). Detected by: mechanoreceptors and chemoreceptors.

Question 14

What activities do the mechanoreceptors/chemoreceptors produce when stimulated?

Answer 14

1. Activate/inhibit glands to secrete digestive juices or hormones. 2. Stimulate smooth muscle of GI tract walls.

Question 15

What are the controls of digestive activity?

Answer 15

Neural mechanisms, Hormonal, Local

Question 16

Neural mechanisms of control?

Answer 16

ENS - as many neurons as the spinal cord, as many neurotransmitters as the brain. Includes submucosal plexus and myenteric plexus.

Short reflexes - local mediation, control smooth muscle contraction and glandular secretion as relatively localized activities involving small segment of the digestive tract. Sensory neurons/motor neurons/interneurons for local reflexes that operate outside the CNS.

Long reflexes - involve interneurons/motor neurons of CNS, provide a higher level of control over digestive and glandular activities.

Question 17

Hormonal mechanisms of control?

Answer 17

As many as 18 hormones affecting almost every aspect of digestive function.

Question 18

Local mechanism of control?

Answer 18

Involves prostaglandins, histamine and other chems released into the IF and affecting adjacent cells.

Question 19

4. Describe the location of the peritoneum.

Answer 19

Location: visceral layer covers external surfaces of most of the digestive system, parietal lines the wall of the abdominpelvic cavity.

Question 20

4. Describe the function of the peritoneum.

Answer 20

Reduce friction

Question 21

Mesentery

Answer 21

A double layer of peritoneum that extends to the digestive organs from the body wall.

Provides routes for blood vessels, lymphatics and nerves to reach the digestive viscera.

Holds organs in place.

Stores fat.

Mostly dorsal, some ventral attachments

Question 22

Some individual mesenteries?

Answer 22

Greater omentum, lesser omentum, falciform ligament, mesentery proper, mesocolon.

Question 23

5. Define retroperitoneal.

Answer 23

Found outside (posterior) to the mesentery, lying against the dorsal abdominal wall.

Question 24

5. Name the retroperitoneal organs of the digestive system.

Answer 24

Most of duodenum, pancreas, ascending/descending colon, rectum.

Question 25

7. Define splanchic circulation.

Answer 25

Includes those arteries that branch off the abdominal aorta to serve the digestive organs and the hepatic portal system.

Includes: hepatic, splenic, L gastric arteries of the celiac trunk, superior and inferior mesenteric arteries.

Question 26

7. Indicate the importance of the hepatic portal system.

Answer 26

First cap beds are in the stomach/intestines –> hepatic portal vein –> second bed is in the liver.

It is responsible for directing blood from parts of the gastrointestinal (GI) tract to the liver.

Substances absorbed in the small intestine travel first to the liver for processing before continuing to the heart.

Question 27

What are the four layers of the alimentary canal?

Answer 27

Mucosa, submucosa, muscularis externa, serosa (innermost to outermost)

Question 28

Structure/function of the mucosa?

Answer 28

Structure: epithelium, lamina propria (areolar), smooth muscle/muscularis mucosae, MALT.

Function:
1. Secrete mucus, enzymes, hormones

2. Absorb digestion end products
3. Protect against infectious disease

Epithelium is stratified squamous in mouth/esophagus/anus, elsewhere it is simple columnar.

Question 29

Structure/function of the submucosa?

Answer 29

Structure: CT - areolar/dense irregular, blood/lyphatic vessels, lymphoid follicles, nerve fibers (submucosal/meissner plexus), elastic fibers

Function: look at structure, self explanatory.

Question 30

Structure/function of the muscularis externa?

Answer 30

Structure: Circular layer/outer longitudinal layer controlled by myenteric plexus.

Function: peristalsis, segmentation, some section are thicker forming sphincters

Question 31

Structure/function of the serosa?

Answer 31

(visceral peritoneum)

Structure: areolar with mesothelium of simple squamous (adventita in esophagus).

Retroperitoneal organs have both a serosa and an adventitia.

Question 32

Peyer’s patches

Answer 32

MALT in ileum

Question 33

Blood supply

Answer 33

Splanchnic circulation supplies digestive system.

• Hepatic portal system
• celiac trunk - splenic, left gastric, hepatic
• superior/inferior mesenteric. Sup to small, inf to large

Question 34

Two nerve plexuses of the enteric system?

Answer 34

Submucosal plexus in submucosa

Myenteric plexus in between circular and longitudinal layer.