Littleton Part I Flashcards
What are the constituent of saliva?
Mucins
Amylase (starch breakdown)
lipase
lysozyme
IgA
Nerve Growth factor
Epidermal Growth factor
What are the functions of saliva?
lubrication
digestion of starch
digestion of fat
antibacterial
immune protection
Saliva Secreation and Chewing have several functions, what are they?
- Disruption of food resulting in smaller particles
- Aid in the formation of a bolus for swallowing
- Initiation of starch and lipid digestion
- Facilitation of taste
- Clensing of mouth and selective antibacterial action
- Clearance and neutralization of refluxed gastric material in the esophagus
- Production of intraluminal gastric and duodenal stimuli
- Regulation of food intake and eating behavior
- Aids in speech
Is salivary secretion hypotonic, isotonic, or hypertonic?
It is a plasma-like isotonic when first secreted into the acinar cells and as it passes through the duct it becomes hypotonic. Therefor the saliva that is actually secreted is hypotonic
What is the direction of ions in the ductal cells?
Chloride and Sodium are heavily reabsorbed
Bicarbonate and potassium are secreted byt to a lesser extent
(Net loss in ions)
Stimulated salivary secretion is ___________ dependent and alkaline.
Flow
As flow rate increases what happens to the ions?
pH, sodium, and bicarb increase then plateau
chloride steadily increases
potassium decreases then plateau
What occurs with flow rate of saliva nad pH while sleeping?
Flow rate decreases
pH becomes more acidic
(this is why you wake up with a weird taste in your mouth)
What are the two spinchters in the esophagous?
Upper esophageal sphincter
Lower esophageal sphincter
They remain tonically contracted (myogenic tone)
Neurotransmitters mediate swallow-induced esophagel peristalsis and les relaxation. What are the names of the neurotransmitters involved?
Ach - stimulates contraction
NO/VIP - cause relaxation
What maintains salivary amylase activity in the stomach?
Buffers and substrate protection
(this allows it to be neutralize)
What occurs to the pH and concentration of salivary amylase as you go from the esophagous to the pylorus?
Esophagous
pH - 7-8
amylase - 100 units
body of stomach
pH 5-6
(buffers are then released)
duodenum
pH 6-7
salivary amylase 50 units
What are the layers of the digestive tract?
Serosa
Muscularis External
Submucosa
Mucosa
What is the name and function of the plexus located in the submucosa layer?
Submucosal plexus
“inner wall of circular muscle layer, nut in submucosa layer”
SENSORY FUNCTION
Motor function of the GI is controlled by?
Myenteric plexus
Located between the circular and longitudinal layers of the muscularis externa
Describe the serosa?
Connective tissue lining
If damaged, the peritoneum is exposed and this must be surgically repaired
Describe the Submucosa?
Contains vessels and nerves
If damaged occurs at this layer you develop a ulcer (damage extends through the muscularis mucosa)
What are the two layers of the muscularis externa?
Outer longitudinal muscle
Inner circular muscle
Name and Describe the layers of the mucosa
(from inner to outter)
Mucous Membrane
line villi, epithelial cells, sensory
Lamina Propria
connective tissue
Muscularis Mucosa (interna)
muscular, movement in villi upon contraction
Damage to the mucosa is known as?
Erosion
(superficial to the muscularis mucosa)
The stomach and the proximal duodenum are normally exposed to what?
HCL
Pepsin
The cells in the cardia are sensitive to what?
Change in the concentration of ions and motility
Duodenal ulcers are typically associated with which part of the duodenum?
Duodenal bulb
this is the first part after the plyoric spinchter
What is the difference betwen the Right and left colon function and slow wave propagation?
Right colon (ascending)
slow wave propagation is backward
Last stop for absorption of water and electrolytes
Left colon (descending)
slow wave propagation is forwards
Formation and storage of feces
What are the three mechanism of communication response in the GI tract?
Endocrine
sensor cell -> hormone released into circulation -> target cells
Neurocrine
sensory neuron -> interneuron -> secretomotor neuron -> Neurotransmiter realeased close to target cell
more rapid in eliciting a response
Paracrine
released into interstitium and the target cell is near by
What is the localizaiton and fuction of amylin?
Localization
Pancreatic Beta cells
Function
decrease insulin secretion
decrease gastric emptying
satiety factor
What is the function and localization of Ghrelin?
Localization
CNS, Stomach, Intestine
Function
released by fasting
increease gastric activity
increase growth hormone release
What is the localization and function of PP (pancreatic polypeptide)?
Localization
Pancreatic PP secreting cells (Islet of Langerhan)
Function
decrease post prandial exocrine pancreatic secretion via vagal-dependent pathway
Undigested fat -> PP stimulated -> slows down other pathways -> fat can be effectively broken down
Stimulus - Vagus
Physio funciton
+ small intestine absorption
- pancreatic exocrine secretion
- pancreatic endocrine secretion
Gastrin (G)
Main Active Form - G17 and G34
Localization - antrial G cells
Function - regulation of gastic hydrogen ion concentration
Stimulus - distention of stomach (main), peptides and AA
Distribution - Antrum, duodenum, jejunum
Physio action
+gastric acid and peptide secretion
+growth fo stomach and intestine mucosa
+ gastric motility
+closure LES
Cholecystokinin (CCK)
Main Active Form - CCK8, 33, 39, 58
Localization - Intestinal I cells
Function - regulation of pancreatic enzyme secretion
Stimulus - fat, peptides and AA
Distribution - Duodenum, jejunum, ileum
Physio Actions
+ gall bladder contraction
+ relaxation of sphinchter of oddi
+ pancreatic enzyme release
- gastric emptying
+ pancreatic aqueous secretion
- gastric acid and pepsin secretion
Gastin releasing peptide (GRP)
Main Active Form - GRP
Localization - GI nerves
Function - gastrin release and acid secretion
Somatostatin
Main Active Form - SS14, SS28
Localization - Gastric D cells
Function - Paracrine regulator of hydrogen ions and gastrin
Stimulus - ACid in lumen
Distribution - fundus, small intestine, colon
Physio action
- gastrin, secretin, VIP, GIP, motilin
- gastric acid secretion
- pancreatic exocrine secretion
- gastric motility
Secretin
Main Active Form - Secretin 17
Localization - Intestinal S cells
Function - regulation of pancreatic bicarbonate
Stimulus - Acid
Distribution - duodenum, jejunum, and Ileum
Physio action
+ pancreatic aqueous secretion (bicarb and water)
+ pancreatic enzyme secretion
- gastric acid and pepsin secretion
- gastric emptying
Gastrin inhibitory peptide (GIP)
Main Active Form - GIP 43
Localization - Intestinal K cells
Function - regulation of insulin release/inhibitor of hydrogen ions
Stimulus - fat, glucose (glucose dependent insulin otropic peptide)
Distribution - Duodenum, jejunum, Ileum
Physio Action
- gastric acid and pepsin secretion
- gastric emptying
+ insulin secretion
Motilin
Main Active Form - Motilin 22
Localization - Intestinal M cells
Function - interdigestive intestinal motility
Stimulus - fasting
Distribution - duodenum, jejunum, ileum
physio action
+ contraction of intestinal smooth muscle, MMC
Calcitonin gene-related peptide (CGRP)
Main Active Form
Localization - primary afferents and myenteric neurons
Function - neural mediator of primary afferents
physio action - circular musclular contraction
Pancreatic polypeptide (PP) related
Main Active Form - PP - , neuropeptide Y, protein YY - 36
Localization - Enteropancreatic (PP-&L) endocrine cells, sympathetic neurons
Function - Neural modulation of sympathetic transmission, inhibiotr of pancreas
Vasoactive Intestinal Polypeptide (VIP)
Main Active Form - VIP 28
Localization - Myenteric Inhibitory motoneurons/submucosal neurons
Function - neural inhibitor of motiolity/ stimulant of fluid secretion
Stimulus - distension
Distibution - Fundus, Antrum, small intestine, colon
Physio action
+ smooth muscle relaxation and sphincter relaxation
+ intestinal secretion of electrolytes and water
+ dilation of peripheral blood vessels
Histamine
Main Active Form
Localization - ECL cells
Function - stimulus of gastric acid secretion
Stimulus - injury (vagus post ganglionic)
Distribution - mast cells (ECL)
Physio action
+ gastic secretionof HCL and pepsin
Norepinephrine
Main Active Form
Localization - extrinsic digestive nerves
Function - vascular regulation
Serotonin
Main Active Form
Localization - EC cell of digestive tract
Function - Stimulate peristalsis
Substance P
Main Active Form
Localization - digestive nerves
Function - neurotransmitter
Stimulus - distention
Distrubtion - excitatory motor neurons
Physio actions
+ intestinal motility
There are two forms of gastrin (large form in intestine and small one in the stomach), what is unique about gastrin?
On the carboxy end there are for AA that are essential. They are needed for minimal gastrin activity. It is found in the small (17) and large (34) form of gastrin. Also found in CCK but CCK has a couple more essential AA added that are essential.
What is the Pentagastrin?
It is a combination of the 4 essential AA need for gastrin activity plus Beta-ALA.
It can be injected in a patient to generate gastrin activity.
How does trypsin affect gastin?
Converts big gastrin to small gastin in the small intestine
Parasympathetic innervation to the GI tract
Cranial
Vagus (75%, up to transverse colon)
Sacral
Pelvic n.
Sympathetic innervation to the GI tract
Thoracolumbar
(intermediolateral cell column)
Splanchnic nerves (preganglionic)
Postganglionic
Celiac plexus
superior mesenteric plexus
inferior mesenteric plexus
What are the three division of the ANS that innervate the gastointestinal tract?
Sympathetic division - Thoracolumbar
Enteric division - Plexuses Submucosal-Myenteric
Parasympathetic division - Cranionsacral
Nitric oxide (NO)
Stimulus - distention
Distribution - inhibitory, motor neurons
Physio action
+ smooth muscle relaxation (nonadrenergic; noncholinergic mediator of smooth muscle relaxation)
+ release of VIP
Acetylcholine (Ach)
Stimulus - action potential
Physio action - enhances all GI functions
Describe Peristalsis and how the propulsive and recieving segment differ.
Propulsive Segment (wants to close up)
relaxation of longitudinal muscles (relaxation is passive)
contraction of circular muscles (Substance P, Acetycholine, CTRP)
Recieving segment (wants to open up)
contraction of longitudinal muscles (acetycholine)
relaxation of circular muscles (VIP and NO)
The regulation of peristalsis requires?
It requires reflexes
distension -> sensory neurons -> cholinergic interneuron -> exitatory motor neuron -> SP/Ach -> circular muscle (contraction of propulsive segment)
distension -> sensory neurons -> chollinergic interneuron -> inhibitory motor neuron -> VIP/NO -> circular muscle ( relaxation in recieving segment)
Persitalsis occurs in which part of the esophagus?
Bottom 2/3
What is the difference between the proximal stomach, distal stomach, and pylorus?
Proximal stomach = storage
Distal stomach = preparatory chamber
Pyloric antrum sphincter and duodenum = emptying mechanism
Antrial contraction forces contents into ______?
Corpus
Terminal Antrial contraction does what?
closes pyloric canal and pylorus
How does peristalsis affects the width of the stomach?
It provides a narrow orifice so that gastric content can be propelled forward and a portion of food is propelled backwards for further digestion
Jet retropulsion does what?
Produces emulsification
How is defecation initiated?
Ano-rectal distansion intiates a defecation response
Involuntary Defecation Reflex
Propulsive motility of descending colon and rectum
Voluntary Defection Reflex
closure of glottis
descent of diaphragm
contraction of abdominal wall muscles
(all of these cause a increase in intra-abdominal pressure
Relaxation of internal anal sphincter and external anal sphincter is caused by what?
Distansion of rectum
(this leads to defecation)
The colonic response to a meal is initiated by what?
By signals from the stomach and intestine
