2 - Salivary Secretion, Swallowing, Esophagus Flashcards
Objectives: Describe how salivation is regulated
Nervous System
What increases production?
Parasympathetics vs Sympathetics
- Nervous Control
- Under total autonomic nervous system control
- BOTH parasympathetic and sympathetic INCREASE saliva production
- Parasympathetics (cut = atrophy)
- Stronger; increases tx process of acinar/ductal cells
- Stimulates vasodilation of blood vessels
- Sympathetics (cut = little effect)
- Increase production of saliva; growth of salivary glands
- Contraction of myoepithelial cells
- Stimulates vasoconstriction of blood vessels
Objectives: Describe how salivation is regulated
Stimulation
Inhibition
- Saliva Production Increased by:
- Food in mouth
- Smells
- Conditioned reflexes
- Nausea
- Saliva Production Decreased by:
- Sleep
- Fatigue
- Dehydration
- Fear
- Anticholingergic Drugs - block parasympathetics (ACh)
Objectives: Describe the organic and ionic composition of saliva
Proteins
Other substances?
Ionic Composition
- Protein Components of Saliva
- a-amylase (ptyalin) - digest starches
- Lingual Lipase - digests fats
- Mucin - lubrication
- Also contains bacteriocidal substances
- Ionic Composition:
- Hypotonic to Plasma (Less Na+ vs Plasma)
- Initial fluid from acinus isotonic
-
Striated Ducts modify:
- Reabsorb Na / Cl - Lowers [X] vs Plasma
- Secrete K / HCO3 - Increases [X] vs Plasma
- More solute than water is reabsorbed; saliva becomes hypotonic
- Mechanism:
- Cl- exchange w/HCO3-
- Na+ exchange w/H+
- H+ exchange w/K+
Objectives: Describe the relationship between ionic composition and flow rate of saliva
As Flow Rate Increases:
[Na+]Saliva : Increase/Decrease?
[Cl-]Saliva : Increase/Decrease?
[K+]Saliva : Increase/Decrease?
[HCO3-]Saliva : Increase/Decrease?
As flow rate increases, less time for ion transport–thus saliva more isotonic (more Na+ / Cl- than normal)
HCO3- also increases with flow rate because its secretion stimulated when saliva stimulated
Summary:
As Flow Rate Increases:
[Na+]Saliva : Increase
[Cl-]Saliva : Increase
[K+]Saliva : Decrease, Plateau
[HCO3-]Saliva : Increase, Plateu
Objectives: Describe how food moves through the esophagus
Swallowing (Deglutition) Mechanism: Voluntary vs Involuntary
Steps to Involuntary?
-
Oral = Voluntary Phase
- Swalloing initiated by voluntary action of collecting bolus of food and forcing into oropharynx
-
Pharyngeal = Involuntary Phase
- Nasopharynx closed by soft palate (blocking nasal cavity)
- Breathing inhibited
- Glottis closed; larynx elevated
- Peristalsis begins in pharynx to propel toward esophagus
- Upper esophageal sphincter relaxes
- Contraction of constrictor muscles in pharynx moves material into esophagus
Objectives: Describe how food moves through the esophagus
Control
- Reflex Response
- Coordinated in swallowing center in medulla
- Can be initiated voluntarity; needs trigger
- Dysfunction (Dysphagia)
- Lesions in swalling center result in loss of pharyngeal (involuntary) phase
- Neurological Disorders; Cancer
Objectives: Describe the clinical correlations associated with the esophagus
Gastroesophageal Reflux Disease (GERD)
Hiatal Hernia
Barretts Esophagus
- GERD
- Cause: Decrease tone of LES; reflux of acid
- Symptoms: Heartburn; Esophagitis; ulceration/stricture due to scarring; asthma, chronic cough, chest pain
- Treatment: Lifestyle change; antacids; surgery; endoscopic procedures
- Hiatal Hernia
- Cause: Congenital condition where part of LES and stomach moved through hiatus of diaphragm
- Weakens acid reflux barrier
- Barrett’s Esophagus
- Constant injury causes continuous cell growth (metaplasia)
- Can lead to esophageal cancer
- Achalasia
- Cause: Neuromuscular disorder of lower 2/3 of esophagus, leading to absence of peristalsis and failure of LES to relax
- Sympoms: Food accumulates in esophagus; Regurg of food; weight loss
- Treatment: Surgery, drugs
Salivary Secretion Overview
Function
Named Glands
Structure of Glands
- Function:
- Digestion
- Lubrication
- Protection
- Sense of Taste
- Named Glands
- Parotid (middle)
- Submaxillary (most) / Submandibular
- Sublingual (least)
- Structure
- Acinus - Blind end of duct; secretes initial saliva
- Intercalated Duct - Connects acinus with striated duct
- Striated Duct - Modified inforganic composition of saliva
- Myoepithelial Cells - Contract when saliva production is stimulated and eject saliva into mouth
Xerostomia (Dry Mouth)
Associated with?
Causes?
Treatment?
- Associated With:
- Dental Caries
- Chronic Infecion of Buccal Mucosa
- Speech, Taste, Swalloing Dysfunction
- Causes:
- Antidepressents (anticholinergic, block parasympathetics)
- Sjogren’s Syndrome, Radiation damage during cancer treatment
- Treatment
- Sipping water
- lemon-lozenges
- artificial saliva
- pilocarpine mouthwash/tablets
Describe esophagus structure
Muscle structure
Upper Esophageal Sphincter (UES)
Lower Esophageal Sphincter (LES)
- Muscle structure
- Upper 1/3 Striated
- Lower 1/2 Smooth
- Upper Esophageal Sphincter (UES)
- Cricopharyngeal M.
- Separates esophagus from Oral Cavity
- Blocks air
- Lower Esophageal Sphincter (LES)
- Not distinct muscle; higher pressure
- Separates esophagus from Stomach
- Blocks gastric acid backflow
Explain the motility steps to movement of food through esophagus
- UES relaxes; food moves; contracts to prevent backflow
- Primary Peristaltic Contraction Begins - Initiated by Swallowing; propels food toward LES
- LES relaxes; food enters stomach; LES contracts to prevent gastric acid backflow
-
Secondary Peristaltic Contraction - Initiated by food in esophagus (distension); stretch of mech. receptors cause add’l contractions to clear materials
- Mediated by Enteric Nervous System and Vagovagal Reflex
