Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
107 Cards in this Set
- Front
- Back
Motility
|
Contractions of smooth muscle in the wall of the tube crush, mix and move contents
|
|
Absorption
|
Transport water, ions and nutrients from lumen, across epithelium and into blood
|
|
Secretion
|
Delivers enzymes, mucus and ions into the lumen (and hormones into blood)
|
|
Organization of the gut wall
(Name the layers...starting with lumen) |
Lumen
Mucosa (epitheliuma and lamina propria) Muscularis mucosa Submucosa Muscularis externa (2 -3 layers) Serosa/adventitia |
|
Esophagus
(Basic Sxr, Fxn) |
passageway for rough bolus of food
(nonkeratinized) stratified squamous epithelium glands in submucosa for lubrication |
|
Stomach
(Basic Fxn) |
produces secretions required to convert food into chyme;
mucosa comprises multiple types of secretory cells. Mechanical actions require greater smooth muscle |
|
Small Intestine
(Basic Fxn) |
provides additional digestive enzymes (some from extramural glands) and
absorbs amino acids, sugars, fats and other molecules liberated by digestion; mucosa includes both secretory and absorptive cells |
|
Large Intestine
(Basic Fxn) |
completes absorption (especially reabsorption of water and ions) and
compacts non-digestible waste for elimination; some absorptive cells and goblet cells to produce lubricating secretions |
|
In contrast to the rest of the GI tract, this layer of muscle is not just smooth muscle in the esophagus...
|
the Muscularis Externa contains a variable amount of striated muscle
- proximal esophagus = striated muscle - distal esophagus = smooth muscle |
|
What is the outer most layer of the esophagus?
|
esophagus is not free as it courses through the thoracic cavity... it is embedded in connective tissue
the outer tunic is ADVENTITIA , not serosa |
|
Does absorption or secretion occur in the esophagus?
|
No absorption in esophagus
Secretions lubricate the luminal surface to facilitate movement of the food bolus Secretions provided by subepithelial glands |
|
esophageal cardiac glands
|
occur in lamina propria of lower (and sometimes upper) esophagus; produce neutral mucus that helps neutralize stomach acid
|
|
What innervates the muscularis externa of the esophagus?
|
CN X (vagus nerve) produces peristaltic movements
|
|
What do the submucosal glands of the esophagus produce?
|
acidic mucus that lubricates the luminal wall
|
|
Esophageal Sphincters
|
Esophagus bounded by two physiologic sphincters (formed from inner circular layer of muscularis externa)
Upper esophageal sphincter closely associated with larynx; during swallowing pulls larynx forward to help rout food into esophagus Lower esophageal sphincter where esophagus joins stomach. Normally upper and lower sphincters closed except during swallowing to prevent entry of air from the oral cavity or reflux of stomach contents |
|
What occurs with the sphincters in GERD?
|
In heartburn and gastroesophageal reflux disease (GERD) lower sphincter does not close properly so acid refluxes into esophagus and causes a burning sensation in the chest /throat and even coughing and sensation of choking.
|
|
What are the components of the submucosa in the esophagus?
|
mucus glands
lymphoid cells blood vessels elastic fibers |
|
Esophagogastric junction
|
Transition from esophagus to stomach normally more discrete in mucosa (squamous epithelium to invaginating columnar epithelium) than in deeper layers
Esophagogastric sphincter (in muscularis externa) less prominent than sphincter between stomach and small intestine |
|
Stomach: four basic functions that assist in early stages of digestion and prepare for further processing
|
1. Short-term storage reservoir – meal consumed quickly but dealt with over extended period
2. Substantial enzymatic digestion is initiated, particularly of proteins 3. Contraction of smooth muscle grinds food and mixes with gastric secretions; liquefaction of ingesta prerequisite for delivery to small intestine 4. Ingesta slowly released into the small intestine for further processing |
|
Absorption in the stomach
|
Stomach absorbs few substances
- Small amounts certain lipid-soluble compounds (including aspirin and other NSAIDs) - Ethanol These substances recognized causes of gastric irritation; use/overuse commonly associated with development of gastritis |
|
Muscle layers of the stomach
(inner to outer) |
Oblique muscle layer (overlying mucosa)
Cicular muscle layer Longitudinal muscle layer |
|
Four major secretory products of gastric epithelium
|
1. acid
2. mucus 3. proteases 4. hormones Other enzymes secreted by gastric epithelial cells include a lipase and gelatinase Intrinsic factor (glycoprotein secreted by parietal cells) necessary for intestinal absorption of vitamin B12 |
|
Mucus
Stomach Secretion |
Mucous cells cover lumenal surface and extend into the glands (mucous neck cells)
Secrete bicarbonate-rich mucus; coats/lubricates surface, protects epithelium from acid |
|
Acid
Stomach Secretion |
HCl secreted by parietal cells into the lumen
Acidic environment important for activation of pepsinogen and killing microorganisms |
|
Proteases
Stomach Secretion |
Pepsinogen (inactive) secreted by chief cells; activated by acid into protease pepsin, initiates digestion proteins
In young animals chief cells also secrete chymosin (rennin), protease that coagulates milk proteins so retained longer in the stomach |
|
Hormones
Stomach Secretion |
Principal hormone from the gastric epithelium is gastrin, influences acid secretion and gastric motility
secreted from enteroendocrine cells |
|
Six cell types in the gastric epithelium
|
- Non-secretory
Stem cells (throughout GI tract) - Secretory Mucus: 2. Surface mucous cells 3. Mucous neck cells Acid and Intrinsic Factor: 4. Parietal cells (oxyntic cells) Enzymes: 5. Chief cells (peptic cells) Peptides (endocrine/paracrine factors): 6. Enteroendocrine cells (found throughout GI tract) |
|
Stem cells in the Stomach
|
Epithelial Renewal
Dividing stem cells primarily in isthmus region of gastric glands Most new cells become surface cells (live 3-5 days) Other cell types have longer lifespans (up to 150-200 days for parietal cells) but all are replaced from the stem cells |
|
Surface mucous cells in Stomach
|
Each contains mucinogen granules forming “mucous cup” apically; when released the mucinogen forms viscous coat that adheres to epithelial surface
Provides mechanical protection and, because of high bicarbonate concentration, protects epithelium from acidic gastric juice |
|
Mucous neck cells in Stomach
|
Shorter than surface cells, located among groups of parietal cells in neck region of gastric glands
Contain less mucinogen and no prominent mucous cup Produce more soluble mucous, under the control of vagal stimulation |
|
Chief Cells in Stomach
|
Protein secreting cells
Abundant rER basally, so basophilic Eosinophilic apically due to presence of secretory (zymogen) granules containing enzyme precursors Secrete pepsinogen (converted to pepsin on contact with gastric juice) and a weak lipase |
|
Parietal Cells in Stomach
|
oval shape
eosinophilic cytoplasm “fried egg” appearance with prominent central nucleus “secrete” HCL |
|
Acid Production by parietal cells
|
Hydrogen ion concentration in parietal cell secretions is 3,000,000-fold higher than in blood
Chloride is secreted into lumen against both a concentration and electric gradient Ability parietal cells to secrete acid dependent on active transport and ATP Key player is H+/K+ ATPase ("proton pump“) in cannalicular membrane Acid production controlled in part by rapid regulation of the extent of plasma membrane over which ions can be moved between cytoplasm of parietal cells and lumenal fluid |
|
HCl Secretion by parietal cells
(the steps) |
- Dissociation water yields hydrogen ions
- Hydroxyl ions formed and rapidly combine with carbon dioxide to form bicarbonate (catalyzed by carbonic anhydrase) - Bicarbonate transported out of the basolateral membrane in exchange for chloride - Chloride and potassium ions transported from cytoplasm into the lumen of the cannaliculi by passive conductance channels. - Hydrogen ions pumped out of the cell and into the lumen in exchange for potassium through the action of the proton pump (ATPase); potassium is thus recycled back into the cytoplasm - Accumulation of osmotically-active hydrogen ions in the cannaliculus generates osmotic gradient across membrane; get outward diffusion H2O - Acid production dependent on ATP; large numbers mitochondria account for eosinophilia of parietal cells |
|
Regulation of acid production
|
Parietal cells bear receptors for three stimulators of acid secretion, reflecting three-way neural, paracrine and endocrine control:
- Acetylcholine (muscarinic type receptor) - Gastrin - Histamine (H2 type receptor) Histamine from enteroendocrine cells primary modulator but get additive interaction of multiple signals Low amounts histamine, gastrin or ACh released constantly from cells in the gastric mucosa Individually only weakly stimulate acid secretion but when all are present acid secretion is strongly activated |
|
What is the extent of canaliculli and microvilli in parietal cells?
|
Extent of canaliculli and microvilli is not constant
membrane from tubulovesicular system is inserted into plasma membrane and proton pumps are inserted under appropriate physiological stimulation; histamine influences movement of H+/K+ ATPase from cytoplasm into plasma membrane |
|
Enteroendocrine Cells in the Stomach
|
Present throughout gland but most prominent at base
Apex often does not reach lumen (although some processes may) Secrete basally Granules small; usually poorly preserved and palely stained Appears each cell specialized for one type of secretion |
|
Stomach Glands by region
(cardiac, fundic/corpus, pyloric) |
Glands in cardiac and pyloric regions contain a larger proportion of mucus producing cells and fewer parietal cells
Cardiac: moderately deep pits; tortuous, loosely packed tubular glands Fundic/corpus: shallow pits; long, straight tubular glands Pyloric: deep pits; coiled and branched glands |
|
Submucosa of Stomach
|
No glands in submucosa, just connective tissue with lymphoid cells, blood vessels
|
|
Epithelium of Stomach
|
simple columnar epithelium covers luminal surface and invaginates into lamina propria to form gastric glands
|
|
Outer most layer of stomach
|
Serosa: connective tissue covered by simple squamous epithelial cells
|
|
Gastroduodenal Junction
|
Mucosa: change from gastric pits and glands to intestinal villi (V)
Submucosa: appearance of Brunner’s glands (B) Muscularis externa: thicker in pyloric stomach (MEP), particularly where it forms the pyloric sphincter (PS); muscularis externa much thinner in the duodenum (MED) |
|
Function of Small Intestine
|
Small intestine site of absorption virtually all nutrients
In small intestine macromolecular aggregates exposed to pancreatic enzymes and bile, enables digestion to molecules that are ready (or almost ready) to be absorbed Final stages of digestion occur on the surface of the small intestinal epithelium. Net effect of passage through small intestine is absorption of most water and electrolytes (sodium, chloride, potassium) and essentially all dietary organic molecules (e.g., glucose, amino acids and fatty acids) Small intestine provides nutrients to the body and helps regulate water and acid-base balance |
|
What does the duodenum have that the ileum and jejunum lack?
|
Brunner's glands
|
|
What is the pH of the Brunner's Glands secretions in the duodenum?
|
8.1 - 9.3
(a mixture of glycoproteins and bicarbonate ions that neutralize chyme as it is delivered from the stomach, making it close to the optimal pH for pancreatic enzymes) |
|
Layers of the Small Intestine
Plicae Circularis |
involve both submucosa and overlying mucosa
|
|
Layers of the Small Intestine
Villi |
represent evaginations of the mucosa
|
|
Layers of the Small Intestine
Crypts (glands) |
represent invaginations of the epithelium into the underlying lamina propria
|
|
Layers of the Small Intestine
Glycocalyx |
formed by glycoproteins projecting from apical plasma membrane of absorptive cells provides additional surface for absorption and includes enzymes needed for the final digestion of proteins and sugars
|
|
Layers of the Small Intestine
Microvilli |
Absorptive cells (enterocytes) bear microvilli on their apical surface that increase the area of the apical cell membrane
|
|
Six cell types in the small intestinal epithelium
|
Non-secretory
1. Stem cells (found throughout GI tract) 2. Intermediate cells (differentiating cells) 3. Enterocytes (aka absorptive cells) Secretory 3. Enterocytes (produce digestive enzymes) 4. Goblet cells – produce mucus 5. Paneth cells – produce lysozyme 6. Enteroendocrine cells – produce peptides (hormones, etc., found throughout GI tract) |
|
Paracellular
|
transportation across tight junctions between epithelial cells for absorption
tight junctions are impermeable to organic molecules |
|
Transcellular
|
transportation across the plasma membrane of the epithelial cells for absorption
organic molecules (amino acids and glucose) transported transcellularly |
|
Features of the Ultrastructure of Absorptive Cells
|
Microvillous (brush) border: Microvilli contain actin microfilaments that extend into the apical, terminal web cytoplasm.
Extensive apical SER: Involved in packaging some nutrients for transport through cytoplasm Cells tightly opposed apically; intercellular space is wider basally |
|
What is critical to enterocyte function?
|
the establishment of an electrochemical sodium gradient across the epithelial cell boundary
- cells must have low intracellular [Na] to remain viable |
|
How mcuh sodium is tranported out of each small intestinal enterocyte per minute?
|
About 150,000 sodium pumps per small intestinal enterocyte allow each cell to transport about 4.5 billion sodium ions out of each cell per minute
This flow and accumulation of sodium is ultimately responsible for absorption of water, amino acids and carbohydrates. |
|
Absorption of Fatty Acids
|
Most products of lipid digestion (fatty acids and monoglycerides) enter enterocyte by diffusion across plasma membrane (fraction enters via specific fatty acid transporter )
Once inside enterocyte fatty acids and monoglycerides transported into ER, used to synthesize triglyceride Beginning in ER and continuing in the Golgi, triglyceride packaged with cholesterol, lipoproteins and other lipids into chylomicrons. Chylomicrons extruded from Golgi into exocytotic vesicles, which are transported to the basolateral aspect of the enterocyte; vesicles fuse with plasma membrane and undergo exocytosis, dumping chylomicrons into extracellular space |
|
How does the structure of enterocytes vary?
|
Structure of enterocytes varies with functional state (may not be apparent light microscopic level
In “active” enterocyte on there is extensive sER in apical region, large membrane-bound vesicles in middle portion cell, and chylomicrons discharged in extracellular space basalaterally |
|
How is transportation of lipids into circulation different rom transportation of sugars and amino acids?
|
Lipids enter the lymphatic capillary in the core of the villi as chylomicrons
Chylomicron-rich lymph drains into the lymphatic system and then ultimately into the blood Sugars and AAs drain into the blood capillaries |
|
What is the function of goblet cells in the intesetinal epithelium?
|
Produce mucus that contributes to barrier functions:
- Carbohydrates on mucin molecules bind bacteria; helps prevent colonization and causes aggregation, accelerating clearance - Reduced diffusion hydrophilic molecules in mucus (compared aqueous solution) retards access of many damaging chemicals, including gastric acid, to epithelial surface |
|
Paneth Cells
|
- Provide defense against microbes (functionally similar neutrophils)
- Produce alpha-defensins - Secrete defensins when exposed to bacteria or bacterial products secrete lysozyme and phospholipase A2 (antimicrobial activity) - In intestinal crypts identified by basophilic basal cytoplasm and intensely acidophilic apical secretory vesicles |
|
Alpha-defensins
|
interact with phospholipids in cell membranes and form pores to disrupt membrane function and kill cells - bacterial membranes have higher concentrations of negatively-charged phospholipids than vertebrate membranes so intestinal cells are protected
|
|
Which part of the small intestine has the greatest development of lymphoid tissue?
|
Ileum (peyer's patches)
|
|
What is the main site of absorption?
|
Jejunum (most extensive development of plicae and most complex villi)
|
|
Are there glands in the submucosa of the small intestine?
|
only in the duodenum
|
|
Small Intestine Mucosa
|
Simple columnar epithelium covers luminal surface and invaginates into lamina propria to form glands (crypts of Lieberkuhn)
|
|
Recovery water and electrolytes in LI
|
by time ingesta reaches terminal ileum 90% of water absorbed but some water and electrolytes like sodium and chloride remain and must be recovered by absorption in large intestine
|
|
Formation/storage of feces in LI
|
as ingesta moved through large intestine is dehydrated, mixed with bacteria and mucus, and formed into feces
|
|
Microbial fermentation in LI
|
large intestine all species filled with microbes; produce enzymes capable of digesting many molecules that to vertebrate cells are indigestible (e.g., cellulose) - extent and nutritional benefit of fermentation varies among species
|
|
Cecum
|
is a blind-ended pouch, in humans terminates in worm-like extension called vermiform appendix
|
|
Colon
|
constitutes majority of the length of the large intestine
|
|
Rectum
|
is short, terminal segment of the digestive tube, continuous with anal canal
|
|
Histology of Large Intestine
|
Mucosa has smooth surface (no villi) although crypts are present and extend down to the muscularis mucosa.
No submucosal glands are present. The outer longitudinal layer of the muscularis externa is thinner than the inner circular layer except where the outer layer forms the tenia coli |
|
Teniae coli
|
Outer longitudinal layer muscularis externa exhibits three equally-spaced bands called teniae coli (TC, in rectum outer band uniformly thick, as in small intestine)
|
|
What cell is in the epithelial intestinal glands of the small intestine, but not the large intestine?
What cells are there in spades? |
Paneth cells
Large bowel contains higher percentage goblet cells than small intestine but absorptive cells still predominate over goblet cells except in the distal colon near the rectum Absorptive cells absorb water and electrolytes as waste is compacted |
|
Mucosa of the Large Intestine
|
Crypts (glands) in large intestine straight and unbranched with regularly-spaced openings to surface epithelium
Absorptive cells most common apically, goblet cells predominate deeper in glands (where enteroendocrine cells (E) may be present) Plasma cells (P, antibody-producing cells) often present in lamina propria In contrast to small intestine lymphatic capillaries generally absent from lamina propria large intestine |
|
When do the goblet cells secrete mucus in the colon?
|
Goblet cells abundant in the colonic epithelium and secrete mucus in response to tactile stimuli from lumenal contents, as well as parasympathetic stimuli - mucus as lubricant protects epithelium and helps bind dehydrated ingesta to form feces
|
|
Absorption and secretion in the Colon
|
Water absorbed in response to osmotic gradient ; mechanism essentially identical to that in small intestine – Na+ transported from lumen across epithelium to basolateral extracellular space by virtue of active sodium pumps on basolateral membranes and means of absorbing sodium through lumenal membrane
Chloride absorbed by exchange with bicarbonate at apical surface; resulting secretion of bicarbonate ions into lumen aids in neutralization of acids generated by microbial fermentation mucus secretion |
|
Key cell types in the epithelium of the large intestin
|
Absorptive cells in surface epithelium (absorb mostly water and ions)
Many goblet cells (mucus secreting) Stem cells (deep in crypts) Enteroendocrine cells |
|
Key cell types in the Lamina Propria of the large intestine
|
Fibroblasts
Many scattered lymphocytes (mostly T cells); often small lymphoid nodules containing (mostly) B lymphocytes Eosinophils Muciphages |
|
Could the appendix have a purpose?
|
recent evidence suggests that the appendix is a sanctuary for beneficial gut bacteria
|
|
How does the appendix change as we age?
|
greatly increased lymphoid tissue in children
greater connective tissue in aubmucosa in adult |
|
Vermiform Appendix
|
- Blind-ending tubular extension of cecum
- Structure similar to that of colon but smaller diameter and taeniae absent - Mucosa similar to colon - straight glands with absorptive cells, goblet cells and some enteroendocrine cells - Lamina propria and submucosa may contain abundant lymphoid tissue (even confluent nodules); lymphoid tissue accumulates during childhood then progressively disappears so only traces evident in adults - As the lymphoid tissue atrophies is replaced by fibrous connective tissue |
|
What are the 3 zones of the anal canal?
|
colorectal zone
anal transitional zone squamous zone |
|
colorectal zone of anal canal
|
upper 1/3
simple columnar epithelium (as in rectum) |
|
anal transitional zone of anal canal
|
middle 1/3
transition from simple columnar to stratified squamous epithelium (which continues to the cutaneous zone) muscularis mucosa ends here |
|
squamous zone of anal canal
|
lower 1/3
stratified squamous epithelium that is continuous with perineal skin |
|
Peyer's Patches
|
lymphoid follicles located in mucosa and extending into submucosa small intestine (especially ileum).
In adults, B lymphocytes predominate but T cells also present. maller lymphoid nodules found throughout intestinal tract |
|
Lamina propria lymphocytes
|
lymphocytes scattered in lamina propria of mucosa
most are IgA-secreting B cells |
|
Intraepithelial lymphocytes
|
Lymphocytes positioned in basolateral spaces between lumenal epithelial cells (beneath tight junctions)
|
|
Immune function in the GI system –GALT
|
Lumen of GI tract populated with potentially pathogenic microorganisms
Immune system maintains strong presence at mucosal boundary with lymphocytes, macrophages and other immune cells Lymphoid tissue in gut collectively referred to as gut-associated lymphoid tissue or GALT, represented by three primary populations: - peyer's patches -lamina propria lymphocytes - intraepithelial lymphocytes In addition to GALT the lymph nodes that receive lymph draining from gut (mesenteric nodes) and Kupffer cells (phagocytic cells in liver) help protect against invasion |
|
Lymphoid follicles
|
Lymphoid follicles contain both B- and T-cells, generally in discrete zones
Germinal centers of secondary follicles contain replicating and maturing B-cells Lymphoid follicles do not have afferent lymphatic vessels but have efferent lymphatics. Epithelium overlying Peyer’s patches (dome epithelium) has cuboidal rather than columnar cells and also many intraepithelial lymphocytes (IEL) Some epithelial cells are microfold cells (M cells), can transfer antigens (by endocytosis) between lumen and Peyer’s patch |
|
Microfold (M) cells
(sxr and location) |
are epithelial cells with apical folds instead of microvilli
Have deep recesses within which lymphocytes sit in close apposition to lumen of small intestine Bear MHC II molecules and present antigens to T lymphocytes within their recesses (see box 16.5, p. 509 for further description) |
|
M cell function
|
Microfold cells endocytose protein and peptide antigens; instead of digesting proteins M cells transport them into underlying tissue
Interact with dendritic cells to help coordinate immune response Are exploited by some infectious agents to gain access Function is altered when rest of mucosal barrier is altered by pathology (as in inflammatory conditions) |
|
Role of Auonomic Nervous System in GI Function
|
sympathetic stimulation causes inhibition of gastrointestinal secretion and motor activity (and contraction of gastrointestinal sphincters and blood vessels)
parasympathetic activation typically stimulates digestive activities |
|
Lymphoid follicles
|
Lymphoid follicles contain both B- and T-cells, generally in discrete zones
Germinal centers of secondary follicles contain replicating and maturing B-cells Lymphoid follicles do not have afferent lymphatic vessels but have efferent lymphatics. Epithelium overlying Peyer’s patches (dome epithelium) has cuboidal rather than columnar cells and also many intraepithelial lymphocytes (IEL) Some epithelial cells are microfold cells (M cells), can transfer antigens (by endocytosis) between lumen and Peyer’s patch |
|
Microfold (M) cells
(sxr and location) |
are epithelial cells with apical folds instead of microvilli
Have deep recesses within which lymphocytes sit in close apposition to lumen of small intestine Bear MHC II molecules and present antigens to T lymphocytes within their recesses (see box 16.5, p. 509 for further description) |
|
M cell function
|
Microfold cells endocytose protein and peptide antigens; instead of digesting proteins M cells transport them into underlying tissue
Interact with dendritic cells to help coordinate immune response Are exploited by some infectious agents to gain access Function is altered when rest of mucosal barrier is altered by pathology (as in inflammatory conditions) |
|
Name the 3 types of Neurons in the enteric plexuses
|
Sensory Neurons
Motor Neurons Interneurons |
|
NTs secreted by enteric neurons
|
Acetylcholine generally excitatory; stimulates smooth muscle contraction, intestinal secretions, release of enteric hormones and dilation blood vessels
Norepinephrine (from extrinsic sympathetic neurons) is generally inhibitory (opposes ACh) |
|
Interneurons
of the enteric nervous system |
integrate information from sensory neurons and relay it to motor neurons
|
|
Motor neurons
of the enteric nervous system |
control GI motility and secretion (possibly absorption)
act on smooth muscle, secretory cells (chief, parietal, mucous, enterocytes, pancreatic exocrine cells) and enteroendocrine cells |
|
Sensory neurons
of the enteric nervous system |
Receive information from sensory receptors in mucosa and muscle
Respond to mechanical, thermal, osmotic and chemical stimuli; Collectively provide information on gut contents and state of GI wall - Chemoreceptors sensitive to acid, glucose and amino acids "taste“ lumenal content - Sensory receptors in muscle respond to stretch and tension |
|
Components of the Submucosal and Myernteric plexi
|
axons and postganglionic parasympathetic neurons
|
|
What doe the nervous system influence in the GI tract
|
motility,
ion transport (associated with secretion and absorption), and gastrointestinal blood flow |
|
Myenteric Plexus
|
located between longitudinal and circular layers of muscle in tunica muscularis; exerts control primarily over digestive tract MOTILITY
|
|
Submucosal plexus
|
within submucosa; principal roles include
1. sensing environment within lumen, 2. regulating gastrointestinal blood flow, and 3. controlling epithelial cell function (sparse in esophagus where these functions less relevant) |