Renal Final - Jarrett - Summer '22

Which enteric plexus is found between the longitudinal and circular muscle layers?

Myenteric (Auerbach's)

Which enteric plexus is found within the submucosa?

Submucosal (Meissner's)

The mucosa of the GI tract wall consists of?

Epithelial liningLamina propria (loose CT, vessels, small glands)Muscularis mucosa (thin layer of smooth msucle)

The submucosa of the GI tract wall consists of?

Denser CT, submucosal plexus, glands

The muscular is layer of the GI tract wall consists of?

Inner circular layer (smooth muscle)Myenteric plexusOuter longitudinal layer (smooth muscle)

The serous of the GI tract wall consists of?

Loose CTCovered by mesothelium (linked to mesentery)

What is responsible for gross GI movements?

Myenteric plexus

This plexus is composed of a linear chain of interconnecting neurons extending the length of the GI tract?

Myenteric plexus

Myenteric stimulus creates?

Increased ionic contractionsIncreased intensity and velocity of rhythmic contractionsDecreased sphincter tone (vasoactive intestinal polypeptide)

What are the functions of the submucosal plexus?

Controls local intestinal secretion and absorptionControls local contraction of mucosal muscles (in folding of the mucosa)

Which neurotransmitter most often excited GI activity?

Acetylcholine

Which neurotransmitter almost always inhibits GI activity?

Norepinephrine

What innervates the esophagus to the 1st half of the large intestine and the pancreas?

Cranial parasympathetic nerves - mainly vagus

What innervates the distal large intestine to the anus?

Sacral parasympathetic nerves (pelvic nerves)

Postganglionic nerves are located where?

Within the enteric plexus - acetylcholine is postganglionic

Preganglionic neurons originate from?

Segments of T5-L2

Postganglionic neurons originate from?

Prevertebral ganglion

What hormone inhibits the intestinal tract smooth muscle but excites the muscularis mucosa?

Norepinephrine

Afferents are sensitive to?

Irritation of the mucosaDistinction of the gutChemicals in the gut

What provides feedback to the enteric plexus for local control?

Sensory fibers from the gut

What mediates broader reflexes by going to the prevertebral ganglia, spinal cord and brain stem?

Sensory fibers

80% of nerve fibers in the vagus nerves are?

Sensory

Which reflexes are within the gut wall enteric nervous system and control local GI secretions, peristalsis, mixing, and local inhibitory effects?

Enteric reflexes

Which reflexes originate in the gut, go to the prevertebral ganglia and then motor back to the gut?

Autonomic reflexes

Which reflex promotes evacuation of the colon?

Gastrocolic

Which reflex inhibits stomach motility and secretions?

Enterogastric

Which reflex inhibits emptying of ileal contents into the colon?

Colonoileal

Which reflexes send signals from the gut to the spinal cord or brain stem to the GI tract?

Higher level reflexes

Gastrin is secreted by?

G cells of the stomach

What stimulates gastric acid secretion and gastric mucosal growth?

Gastrin

What is secreted by I cells of the duodenum mucosa?

Cholecystokinin (CCK)

Which hormone stimulates gall bladder contraction, slows gastric emptying, and inhibits appetite?

Cholecystokinin (CCK)

Which hormone is secreted by S cells of the duodenum mucosa?

Secretin

Which hormone stimulates pancreatic secretion of bicarbonate and has some effect on GI motility?

Secretin

Which hormone is secreted by mucosa of the upper small intestine?

Gastric inhibitory peptide (GIP)

Which hormone stimulates insulin secretion and decreases stomach motility?

GIP

Which hormone is secreted by the stomach and upper duodenum during fasting?

Motilin

Which hormone increases GI motility and growling stomach?

Motilin

Peristalsis is?

A contractile ring that progresses along tube propelling contents

Peristalsis is generally stimulated by?

Distention but also by parasympathetic and irritation to the epithelium

Peristalsis requires?

The Myenteric plexus

peristalsis always moves?

Toward the anus

What causes a churning effect?

Peristalsis towards a closed sphincter

What creates a chopping or shearing effect?

Local intermittent constrictive contractions

Arterial supply to the caudal stomach is from?

Celiac arterySuperior mesenteric arteryInferior mesenteric artery

The portal system drains from?

The gut, spleen, and pancreas to the liver through the sinusoids

Where does the portal system eventually drain into?

IVC via hepatic veins

Which cells remove any bacteria or particulate materials that may have gotten into the blood?

Reticuloendothelial cells within the liver

In the portal system, fats are absorbed where?

Into the lymph which bypasses the liver and goes into the thoracic duct

Villi contains what?

EpitheliumArteries, veins, and capillariesCentral lacteal (lymph)

As motility and absorption increase, what happens to blood flow?

Blood flow in the micro circulation of the villus also increases

What are chemical factors that regulate blood flow?

Vasodilators - CCK, vasoactive intestinal peptide, Gastrin, secretin, kininOxygen lackAdenosine

How does parasympathetic vasodilation regulate blood flow?

Indirectly increases blood flow by stimulating glandular activity which then increases blood flow by autoregulation

How does sympathetic stimulation regulate blood flow?

Causes vasoconstriction -during intense exercise or in circulatory shock

The muscles of mastication are innervated by?

CN V3

What are the muscles of mastication?

Temporalis, masseter, medial and lateral pterygoid

How does the chewing reflex work

Bolus causes pressure Relaxes muscles to open jawPressure is releasedStretch of muscleTriggers contractionRepeat

What are the three stages of deglutition or swallowing?

Voluntary stage, pharyngeal stage, esophageal stage

What happens during the voluntary stage of swallowing?

Tongue pushes food against palate and squeezes food toward oropharynx

What muscles propel food by peristalsis into the esophagus?

Pharyngeal constrictor muscles

Innervation for swallowing comes from?

CN V and IX Swallowing center in brain stemEfferents: mostly via CN X