Lecture 22- Digestive System

Question 1

What are the four main functions of the digestive system?

Answer 1

1. Take food in
2. Break it don into nutrient molecules
3. Absorb nutrients into bloodstream
4. Rid the body of any indigestible remains

Question 2

Gastrointestinal tract (alimentary canal)

Answer 2

Continuous muscular tube that includes the mouth, pharynx, esophagus, stomach, small intestine and large intestine

Question 3

What are the accessory digestive organs?

Answer 3

Teeth, tongue and salivary glands located in the mouth

Gallbladder, liver and pancreas onnected to the alimentary canal by series of ducts

These facilitate mechanical breakdown of food and produce specialized secretions to aid digestion

Question 4

What are the six activities of processing food?

Answer 4

1. Ingestion- takes food into GI tract
2. Secretion- of digestive enzymes
3. Motility- swallowing, peristalsis, chewing, churning food in stomach and segmentation
4. Digestion- occurs as enzymes catabolize food to its chemical components
5. Absorption- movement of digested end products from lumen of GI tract into blood or lymph
6. Defecation- eliminates indigestible substances via the anus

Question 5

Layers of GI tract

Answer 5

Mucosa- innermost, moist, epithelial membrane that lines entire digestive tract, provides secretions to GI lumen, absorbs digestive end products and protects against infectious diseases

Submucosa- moderately dense connective tissue layer, contains blood and lymphatic vessels, lymphoid follicles and nerve fibres

Muscularis- consists of inner layer of circular and outer layer of longitudinal smooth muscle, performs peristalsis and segmentation

Serosa- protective outer layer, called serosa inside body cavity and ADVENTITIA when surrounded by other tissues, forms visceral peritoneum

Question 6

Splanchinic circulation

Answer 6

Includes arteries that branch off the abdominal aorta to digestive organs and hepatic portal circulation to the liver

Question 7

Visceral peritoneum

Answer 7

Covers external surfaces of most digestive organs

Question 8

Parietal peritoneum

Answer 8

Lines body wall of abdominopelvic cavity

Question 9

Peritoneal cavity

Answer 9

Located between visceral peritoneum and parietal peritoneum and is filled with serous fluid to prevent friction and damage to tissues

Question 10

Mesentary

Answer 10

Double layer of peritoneum that extends to digestive organs from body wall

Allows blood vessels, lymphatics and nerves to reach digestive organs, holds organs in place and stores fat

Question 11

Greater omentum

Answer 11

Fold in visceral peritoneum that connects to stomach

Hangs from the greater curve of stomach in front of intestines

Question 12

Lesser omentum

Answer 12

Fold in visceral peritoneum that connects to stomach

Hangs from liver to lesser curve of the stomach

Question 13

Retroperitoneal organs

Answer 13

Found posterior to mesentery, lying against dorsal abdominal wall

Includes most of pancreas, duodenum and parts of large intestine

Question 14

Enteric nervous system

Answer 14

GI tract nervous system

Participate sin both short and long reflexes

Question 15

Short reflexes

Answer 15

Mediated entirely by enteric neurons

Question 16

Long reflexes

Answer 16

Involve CNS integration centres and extrinsic autonomic nerves

Question 17

What are two major nerve plexuses in alimentary canal?

Answer 17

Myenteric plexus and Submucosa plexus

Question 18

What are the three concepts that govern regulation of digestive activity?

Answer 18

1. Variety of chemical and mechanical stimuli promote digestive activity
2. Smooth muscle and glands are the effectors of GI system
3. Neurons and hormones control digestive activity