Functional Anatomy and General Principles

Question 1

What is the sphincter of oddi?

Answer 1

The sphincter between the common bile duct/pancreatic duct and the duodenum. It controls the amount of bile and pancreatic juices released into the duodenum

Question 2

What are the three major arteries of the splanchnic circulation?

Answer 2

Celiac, SMA and IMA

Question 3

What organs are supplied by the celiac artery?

Answer 3

Liver, spleen and stomach

Question 4

What organs are supplied by the Superior mesenteric artery?

Answer 4

Pancreas, small intestine and proximal colon

Question 5

What organs are supplied by the IMA?

Answer 5

Distal colon

Question 6

What happens to large molecules that are too large to pass into capillaries?

Answer 6

They are taken up by the lymphatic system and returned to the systemic circulation through thoracic duct –> subclavian vein

Question 7

Name the four layers of the gut wall from inside to outside

Answer 7

Mucosa, Submucosa, muscularis externa, serosa

Question 8

What individual components make up the mucosa of the gut wall?

Answer 8

Mucosa is the innermost layer. It is made up of epithelium, the lamina propria, and the muscularis mucosae

Question 9

What are absorptive enterocytes?

Answer 9

The are the most abundant cell of the GI tract epithelium. They play a vital role in digestion and absorption

Question 10

What is produced in gastric mucosal cells?

Answer 10

Protons

Question 11

What type of cells are found in the mucosal epithelium of the esophagus?

Answer 11

Squamous cells- they help in the transportation of swallowed food

Question 12

What type of cells are found in the mucosal epithelium of the intestine?

Answer 12

Columnar- helps in absorption or selective uptake of nutrients, ions, water

Question 13

Describe the architecture of the small intestinal epithelium

Answer 13

The surface area of the small intestinal epithelium consists of villi and crypts.

Question 14

What is the average life span of a cell at the villus tip in the GI tract?

Answer 14

3-5 days. The epithelial lining of the GI tracts is continously renewed

Question 15

What is the consequence of a reduced surface area in the intestinal epithelium, such as in celiac disease?

Answer 15

Malabsorption

Question 16

What is the lamina propria?

Answer 16

The layer immediately below the epithelium- it consists of loose connective tissue (collagen and elastin fibrils).

It is rich in glands, contains lymph vessels and nodes, capillaries, nerve fibers.

Question 17

What three layers make up the mucosa?

Answer 17

Epithelium, lamina propria, and the muscularis mucosa

Question 18

What is the muscularis mucosae?

Answer 18

This this layer of smooth muscle cells directly below the lamina propria

Question 19

In what layer of the GI tract is the submucosal plexus of the enteric nervous system found?

Answer 19

The submucosae

Question 20

In what layer of the GI tract is the myenteric plexus of the enteric nervous system found?

Answer 20

Between the two layers of the muscularis externa (muscularis propria)

Question 21

Describe the muscularis externa

Answer 21

It consists of two layers of smooth muscle cells:

Inner circular layer
Outer longitudinal layer

Responsible for mixing and propelling contexts of the GI tract

Question 22

What is the outermost layer of the GI tract?

Answer 22

The Serosa

Question 23

What cell type makes up the serosa?

Answer 23

Squamous mesothelial cells- secretes a viscous fluid in order to reduce friction between organs in the abdominal cavity

Question 24

Which are the “sensor cells” of the GI system?

Answer 24

Enteroendocrine cells- they respond to a stimulus by secreting a peptide or hormone

Question 25

Which are target cells of paracrine regulation?

Answer 25

smooth muscle, absorptive enterocytes, secretory cells in glands and other EECs

Question 26

Enterochromaffin-like cells in the stomach release what hormone? What is the effect?

Answer 26

Histamine. When released, the histamine binds to nearby parietal cells which can then release HCl

Question 27

What is the role of serotonin released in the GI tract?

Answer 27

Regulation of smooth muscle contractility in the GI

Question 28

What cells release serotonin?

Answer 28

Enteric neurons, mucosal mast cells and enterochromaffin cells

Question 29

When and where is cholecystokinin released?

Answer 29

Cholecystokinin is released from the I cells in duodenum in response to dietary protein and fatty acids

Question 30

What is celiac disease?

Answer 30

Allergic response to gliadin, a component of gluten. It causes an inflammatory response which results in a reduction of density and length of microvilli

Question 31

Differentiate the extrinsic from the intrinsic nervous system in the gut

Answer 31

Extrinsic: nerves that innervate the gut, with cell bodies outside of the gut wall- part of the ANS (parasympathetic and sympathetic) Intrinsic: The enteric nervous system- includes the submucosal and myenteric plexus

Question 32

What parts of the gut does the vagus nerve innervate?

Answer 32

Everything except for the distal colon and anorectal region | Esophagus, stomach, gallbladder, pancreas, 1st part of the intestine, cecum, proximal part of the colon

Question 33

Describe the general impact of parasympathetic stimulation on GI function

Answer 33

Activation

Question 34

What two neurotransmitters are released by peptidergic neurons?

Answer 34

Substance P and VIP

Question 35

What are vagovagal reflexes?

Answer 35

Both afferent and efferent fibers of the vagus nerve coordinate responses to gut stimuli

Question 36

Which gut muscles are activated by sympathetic innervation?

Answer 36

GI sphincter muscles

Question 37

Differentiate how the parasympathetic and sympathetic nerves interact with the ENS.

Answer 37

Parasympathetic fibers all affect the gut indirectly, through synapsing on the ENS Sympathetic fibers can either directly stimulate cells, or indirectly through stimulation of the ENS

Question 38

Where is the myenteric plexus?

Answer 38

Between the inner circular and outer longitudinal muscle layer (muscularis externae)

Question 39

Where is the submucosal plexus?

Answer 39

In the submucosal layer of the gut wall

Question 40

Is the ENS autonomous?

Answer 40

The ENS can act autonomously, but also receives information from the ANS

Question 41

Is all of the muscle of the GI tract smooth muscle?

Answer 41

No- the pharynx, upper 1/3 of the esophagus and the external anal sphincter are striated muscle

Question 42

What permits rapid cell-cell spread of action potentials in GI smooth muscle?

Answer 42

Gap Junctions formed with interstitial cells of Cajal (ICC's)

Question 43

Differentiate phasic from tonic conctractions

Answer 43

Phasic: periodic contractions followed by relaxation Tonic: Constant level of contraction- generally found in sphincters that only relax when told to do so

Question 44

Which cells act as the pacemaker for the gut?

Answer 44

Interstitial cells of cajal- ICCs: They generate the slow waves.

Question 45

How do slow waves of the GI tract relate to contraction?

Answer 45

Slow waves that do not reach threshold still lead to tonic contractions. When action potentials occur, it is followed by a much stronger phasic contraction

Question 46

Where do segmentation contractions occur?

Answer 46

Predominantly in the small and large intestines

Question 47

What is the purpose of segmental contractions?

Answer 47

These allow mixing of the luminal contents with GI tract secretions and increase exposure to the mucosal surfaces where absorption occurs

Question 48

Which neurotransmitters are involved in orad contraction of peristalsis?

Answer 48

ACh and substance P

Question 49

Which neurotransmitters are involved in caudad relaxation of peristalsis?

Answer 49

VIP and NO