Functional Anatomy and General Principles Flashcards Preview

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Flashcards in Functional Anatomy and General Principles Deck (49)

What is the sphincter of oddi?

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


What are the three major arteries of the splanchnic circulation?

Celiac, SMA and IMA


What organs are supplied by the celiac artery?

Liver, spleen and stomach


What organs are supplied by the Superior mesenteric artery?

Pancreas, small intestine and proximal colon


What organs are supplied by the IMA?

Distal colon


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

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


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

Mucosa, Submucosa, muscularis externa, serosa


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

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


What are absorptive enterocytes?

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


What is produced in gastric mucosal cells?



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

Squamous cells- they help in the transportation of swallowed food


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

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


Describe the architecture of the small intestinal epithelium

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


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

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


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



What is the lamina propria?

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.


What three layers make up the mucosa?

Epithelium, lamina propria, and the muscularis mucosa


What is the muscularis mucosae?

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


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

The submucosae


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

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


Describe the muscularis externa

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


What is the outermost layer of the GI tract?

The Serosa


What cell type makes up the serosa?

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


Which are the "sensor cells" of the GI system?

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


Which are target cells of paracrine regulation?

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


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

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


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

Regulation of smooth muscle contractility in the GI


What cells release serotonin?

Enteric neurons, mucosal mast cells and enterochromaffin cells


When and where is cholecystokinin released?

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


What is celiac disease?

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


Differentiate the extrinsic from the intrinsic nervous system in the gut

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


What parts of the gut does the vagus nerve innervate?

Everything except for the distal colon and anorectal region

(Esophagus, stomach, gallbladder, pancreas, 1st part of the intestine, cecum, proximal part of the colon)


Describe the general impact of parasympathetic stimulation on GI function



What two neurotransmitters are released by peptidergic neurons?

Substance P and VIP


What are vagovagal reflexes?

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


Which gut muscles are activated by sympathetic innervation?

GI sphincter muscles


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

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


Where is the myenteric plexus?

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


Where is the submucosal plexus?

In the submucosal layer of the gut wall


Is the ENS autonomous?

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


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

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


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

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


Differentiate phasic from tonic conctractions

Phasic: periodic contractions followed by relaxation

Tonic: Constant level of contraction- generally found in sphincters that only relax when told to do so


Which cells act as the pacemaker for the gut?

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


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

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


Where do segmentation contractions occur?

Predominantly in the small and large intestines


What is the purpose of segmental contractions?

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


Which neurotransmitters are involved in orad contraction of peristalsis?

ACh and substance P


Which neurotransmitters are involved in caudad relaxation of peristalsis?

VIP and NO