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What are the four layers of the GI tract from the lumen out
- Mucosa
- Submucosa
- Muscularis externa
- Serosa/Adventitia
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What is the function and makeup of the Mucosa layer of the GI track
- Protection, secretion, absorption
- Epithelium
- Lamina Propria (GALT) (Loose connective tissue)
- Thin layer of muscularis mucosae
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Where is an exception of the Mucosa layer not having muscularis mucosae
Gallbladder
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What is the purpose of the muscularis mucosae in the Mucosa layer of the GI
It provides localized movement of mucosa (not peristalsis)
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What is the Submucosa made up of
- Dense Connective tissue (GALT)
- Meissners plexus (submucosal plexus)
- Glands in the esophagus and Duodenum
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What is the Muscularis Externa layer of the GI made up of, and what is its role
- 2-3 layers of smooth muscle (inner circular/outer longitudinal)
- Myenteric plexus
- Performs peristalsis
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Auerbachs plexus (Myenteric Plexus)
This is the plexus between two layers in the Muscularis Externa that contains parasympathetic ganglia
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What is the makeup of the Serosa/Adventitia layer of the GI tube
- Serosa is covered by mesothelium
- Adventitia has no mesothelium
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Hypodontia/Hyperdentia
Less teeth then normal/More teeth then normal
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Enamel is produced by
Ameloblasts
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What is the hardest part of the teeth
Enamel
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Cementum
Lower portion of the teeth embeded between the Dentin and the alveolar bone
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Dentin is found where and produced by what
Found just below the enamel and is the thickest portion of the tooth, it is produced by Ondotoblasts
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What portion of the tooth is derived from Ectoderm
Enamel (the rest from mesenchyme)
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What portions of the tooth are derived from Neural crest cells
- Ondotoblasts which develop into Dentin
- Pulp
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What portion of the teeth is derived from Mesoderm
- Cementocytes
- Periodontal ligaments
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When does tooth development begin
6th week
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What is the difference between Gingivitis and Periodontitis
- Gingivitis is reversible damage to the gums
- Periodontitis is irreversible damage to the gums with portions of the roots being uncovered
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Malocclusion
Imperfect position of teeth when the jaw is closed
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What nerve provides voluntary movement of the jaw
Trigeminal (CNV)
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What are the two types of oral mucosa
- Parakaratinized (Masticatory mucosa)
- Non-karatinized epithelium (Lining mucosa)
- Both are stratified squamous epithelia
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Where is the Parakaratinized epithelium found
- Hard palate
- Part of Gingiva (gums)
- Some of the Dorsal surface of the tongue
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Parakeratinized vs keratinized epithelium
- Parakeratinized epithelium has an outer layer (stratum corneum) that is keratinized and have nuclei but lack a stratum granulosum layer
- Karatinized epithelium outer cells do not have nuclei but do have a stratum granulosum layer
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Where is Non-karatinized epithelium found in the oral cavity
Internal surface of the lips, cheeks, floor of the mouth, and the underside of the tongue and soft palate
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What are the layers of the Non-karatinized epithelium in the mouth
- Relatively thick mucosa
- Lamina propria
- Submucosa
- No muscularis mucosa
- No muscularis externa
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Why is the underside of the tongue a good place for absorption of oral medication
Because the underside of the tongue is thin and more permeable therefore absorption will happen rapidly
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The oral cavity contains no
Muscularis mucosa or muscularis externa, therefore, the lamina propria is attached directly to the underlying bone or muscle
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What are the three sections of the lip and their contents
- External aspect - Thin keratinized skin, hair, & glands
- Vermilion zone - Thin skin, no glands or hairs
- Internal aspect - Labial mucosa, minor salivary glands
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What is the difference in the epithelium of dorsal and ventral tongue
- Dorsal - Keratinized stratified squamous epithelium
- Ventral - Non-keratinized lining mucosa
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Filiform papillae characteristics
- Most abundant type of papillae on the tongue
- Connective tissue core with heavily keratinized epithelium
- Catches food
- Gives sandpaper like feel
- No taste buds
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Fungiform Papillae characteristics
- Mushroom shape projections on the tongue
- Non-keratinized or lightly keratinized stratified squamous epithelium
- Have taste buds
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Circumvallate Papillae characteristics
- Largest papillae on the tongue
- Mushroom shaped
- Non-keratinized epithelium
- 250 taste buds per papillae found between each fold
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Foliate Papillae
- Leaf like
- Found along the side of the tongue
- Rudimentary in humans
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Von Ebners glands
Pure serous glands found between the circumvallate papillae
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What are the four types of cells, and their defining characteristics in taste buds
- I - Dark
- II - Light
- III - Neurosensory
- IV - Stem cell (basal cell) don't synapse
- All but IV have microvilli on there outer ends
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What are the five components of saliva
- Hypotonic fluid containing:
- Lubricating proteoglycans (mucin)
- Amylase
- Lysozyme
- IgA
- Salivary proteins
- "SALLI"
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Minor salivary glands are found where in the oral cavity
Lamina propria
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Mucocele
Rupture of the duct and spilling of saliva
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What are the major salivary glands
- Parotid (serous)
- Submandibular (mixed)
- Sublingual (mixed)
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What is the duct of the parotid gland
Stensens duct
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What is the duct of the sub-mandibular gland
Whartons
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How much saliva is secreted in a day
Over one liter
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Ranula
Mucoceles in the floor of the mouth
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What are the components of salivary ducts and their cell types starting with the beggining of the ducts
- Intercalated ducts - Low cuboidal cells
- Striated ducts - Simple cuboidal
- Interlobular/excretory ducts - varied cell types
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What is the role of striated ducts in the duct system of salivary glands
Actively transport Na+ ions from saliva into extracellular space
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How do the salivary glands obtain IgA
Acinar cells or duct cells (beginning of ducts), endocytose IgA dimers from plasma cells, placing them in the lumen of the duct
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Xerostomia
- Dry mouth
- Common in the aged
- Can be drug induced
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Sjogren syndrome
- Autoimmune
- Obstructed ducts
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Sialolithiasis
- Ca2+ Stone formation in saliva ducts causing obstruction
- Dehydration, infections occur as a result
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What are the primary functions of Saliva
- Maintenance of oral hygiene
- Mineralization of teeth
- Lubrication
- Digestive function (amylase & lipase)
- Solvation (taste of soft foods)
- Lysis
- "LDS Love M&M's"
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What are the two stages of salivary secretion
- Primary (Acini)
- Secondary ductal modification (salivary ducts)
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What is the composition and flow of ions in the secondary ductal formation of saliva
- Hypotonic solution
- Low H2O permeability of ducts
- Na+ and Cl- leave the duct
- K+ and HCO3 enter the duct
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What is the fluid like in the primary stage of salivary secretion
Isotonic ECF and plasma like composition (proteins, mucins, & enzymes present)
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What is the primary difference between plasma and Primary secretion of the salivary glands form the acini cells
Acini secrete a higher K+ concentration then what is found the the plasma
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What are the normal plasma levels of K+, Na+, HCO3, and Cl-
- K+ - 3.5-5 mM
- Na+ - 130
- HCO3 - 25
- Cl- - 100
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What is the concentration of Na+ in its stimulated and unstimulated state in the Parotid gland
- Stimulated - 90 mM
- Unstimulated - 15 mM
- 6 times higher in stimulated state
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What is the concentration of K+ in its stimulated and unstimulated state in the Parotid gland
- Stimulated - 15 mM
- Unstimulated - 30 mM
- Half the amount in stimulated state
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What is the concentration of Cl- in its stimulated and unstimulated state in the Parotid gland
- Stimulated - 50 mM
- Unstimulated - 15 mM
- Over 3 times higher in stimulated state
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What is the concentration of HCO3- in its stimulated and unstimulated state in the Parotid gland
- Stimulated - 60 mM
- Unstimulated - 15 mM
- 4 times higher in the stimulated state
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How does Aldosterone and ADH effect the Salivary glands
- Aldosterone - Increases NaCl absorption and K+ secretion
- ADH - Increases NaCl absorption
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What is the difference in Parasympathetic and Sympathetic stimulation of salivary secretion
- Parasympathetic - Copious flow of watery saliva
- Sympathetic - Reduced volume of saliva, rich in enzymes
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What is the route of parasympathetic innervation of salivary secretion
- Reflex (smell, taste, ect.)
- Salivary nucleus of medulla
- CN's VII and IX
- ACh
- IP3
- Ca+ release
- Saliva secretion
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How do the sympathetics trigger salivation
- T1-T3 nerves
- Superior cervical ganglion
- Norepinephrine
- cAMP
- Ca+ release
- Saliva secretion
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What is found in the Mucosa in the esophagus
- Stratified squamous epithelium non-keratinized
- Thin band of lamina propria
- Cardiac glands (mucus)
- Muscularis mucosae (single longitudinal layer)
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What is found in the Submucosa layer of the esophogus
Esophageal glands (Mucus)
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What is found in the Muscularis externa layer of the esophagus
- Inner circular muscle
- Outer longitudinal layer
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The Lower Esophageal Sphincter (LES) opening and closing is controlled by
- Increase tone - ACh & Gastrin
- Decreased tone - VIP & NO
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The Upper Esophageal Sphincter is controlled by what nerve
CN X
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How are the Serosa and Adventitia layers arranged in the Esophagus
Only the portion that is in the peritoneal cavity is covered with Serosa, the rest is covered with Adventitia
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Barretts esophagus
Normal non-keratinized epithelium in the esophagus under goes metaplasia into simple columnar epithelium causing chronic heart burn
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What are the four main stimuli to Motility and digestion
- 1. Distention of gut wall
- 2. Osmolarity of luminal contents
- 3. Luminal pH
- 4. Concentrations of fat, peptides, glucose, ect
- "COLD"
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What is the difference between Myenteric plexus and Meissners (submucosal) plexus
- Myenteric - Mainly gut motility
- Meissners - Mainly absorption, secretion, and blood flow
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What are the steps to swallowing and how long does it take
- Tongue thrust up and back
- Nasopharynx closed
- Larynx elevated
- Airway closed
- Upper esophageal sphincter opens
- Pharynx contracts
- Bolus enters esophagus
- Around 1 second
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After initiating swallowing through the vagus and glossopharyngeal nerves, what actions does the Dorsal Motor nucleus control
- It uses the vagus nerve to increase tone in the esophagus and relax the Lower esophageal sphincter
- Food enters the stomach through peristalsis
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After initiating swallowing through the vagus and glossopharyngeal nerves, what actions do the Nucleus Ambiguus control
- Sequential activation of pharyngeal-esophageal constrictors as well as relaxes the cricopharyngeal muscle
- Food enters esophagus through peristalsis
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After initiating swallowing through the vagus and glossopharyngeal nerves, what actions do the respiratory and speech center control
- Respiratory - Decrease breathing
- Speech - Elevates larynx
- (Sealing the trachea)
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What are the inhibitory signals used by the vagus nerve to stop peristalsis in the esophagus
- VIP (Vasoactive Intestinal Polypeptide)
- NO
- ATP
- Substance P
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What are the excititory signals used by the vagus nerve to initiate peristalsis in the esophagus
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What effect would atropine have on the esophagus
It would shut off the Acetylcholine causing dilation of the esophagus
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How would an NO inhibitor effect the esophagus
NO would be shut off while ACh is active causing the esophagus to constrict
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What is the state of the esophagus at baseline and vagal transaction
It is in the central position, not being constricted or dilated
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Caudad distension
This is when NO and VIP cause the esophagus to dilate ahead of the bolus allowing it to move forward
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Orad constriction
This is when ACh and SP are causing the constriction of the esophagus behind the bolus pushing it forward
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Achalasia
Failure of the esophagus to relax lower esophageal sphincters (LES)
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What are the treatments for Achalasia
- Nitrates
- Calcium Channel blockers
- Injection of botulinum toxin
- Balloon dilation
- Laproscopic myotomy (removal of circular muscles)
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