Mouth + Esophagus Flashcards
Components of the mouth
- Upper/lower lips: closes off oral cavity
- Frenulums (superior & inferior): attaches the lips to the gums to limit motion
- Hard palate: bony structure of the maxilla
- Soft palate: muscles running through it; able to raise it and close off nasopharynx so no food enters nasal cavity
- Uvula: helps close off nasopharynx; irritant receptors = gag reflex
- Tongue: keeps food up on teeth for grinding, initiates swallowing
- Lingual frenulum: flap of tissue that restricts backward movement of tongue
- Submandibular glands: saliva secretions
Gustation: taste buds
- Vallate papillae: 12 each, V shaped
- Fungiform papillae: scattered over tongue, mushroom shaped
- Foliate papillae: in the sides of tongue, degenerate in childhood; this is why there are changes in taste while maturing
- Filiform papillae: tactile sensation + friction
- These tastebuds contain gustatory receptors = specialized episodes cells that secrete neurotransmitters onto neurons at the base of tongue (will constantly replenish)
Cranial nerves involved in gustation
- Facial (7): anterior 2/3 of tongue, parasympathetic output to submandibular glands
- Glossopharyngeal (9): posterior 1/3 of tongue
- Vagus (10): taste sensations at throat and epiglottis
CNs –> brainstem –> thalamus –> primary gustatory area (parietal lobe)
Olfaction
- CN 1
- Olfactory glands produce mucus
- Odourant molecules dissolved here for neural transduction
- Conscious perception of smell occurs in the insular cortex (does NOT synapse in thalamus!!)
- Olfactory cells are only found in the olfactory tract/bulb
Odourant molecules in mucus –> receptors sense these –> dump neurotransmitters onto sensory neurons –> primary olfactory area
NOTE: mammillary bodies = smell memories
Chewing: teeth!
- Incisors: cutting, in front (4)
- Canines: tearing, on side (2)
- Premolars: crushing, front (4)
- Molars: grinding, back (6)
- Permanent teeth arise from ossification centres within the bone of maxilla/mandible
- Supernumerary teeth = extra teeth
Components of a tooth
- Enamel: hardest part of the body
- Pulp: living portion of teeth, has a neuromuscular bundle (A,V,CN5)
- Periodontal ligament: connects teeth to bone
- Need Vit C to make sure this doesn’t get loose (scurvy)
Intrinsic muscles of the tongue
All innervated by the hypogloassal n. (CN 12)
- Longitudinal muscles (x2, sup & inf): run from front –> back, shorten tongue when contracted
- Sup long muscle contracted = tongue rolling
Transverse muscles (x2): right --> left - Causes tongue to get skinnier
Vertical muscle: contracts to flatten tongue
Extrinsic muscles of the tongue
Innervated by CN 12 + attaches to the base of tongue to elevate/retract/depress
- Styloglossus: attaches to tongue + styloid process, raises tongue to force food down.
Hyoglossus: attaches to tongue + hyoid bone (free floating bone)
Genioglossus: attaches to tongue & mandible
- Allows for protrusion of tongue from oral cavity (this is the only muscle that does this!)
Muscles of mastication
All inverted by somatic motor nerves (CN 5)
- Tempolaris muscle: across temporal bone + sends tendon down to mandible
- Forces mandible up against maxilla (chewing)
Masseter muscle: talking + chewing muscle, attaches maxilla to mandible
Muscles of facial expression
Innervated by CN 7
- Buccinator: moves cheeks
- Orbicularis oris: circles around the mouth, purses lips
Vascular supply of mastication
Vascular supply mainly comes from external carotid a.
- Facial a: comes off early, supples mandible
- Maxillary a: supplies maxilla
- Superficial temporal a: runs underneath skin + supplies temporalis muscle
Mouth digestion
Three salivary glands
- Parotid
- Submandibular
- Sublingual
Composition of saliva
- Water
- Amylase: breaks down complex carbs –> simple carbs
- Mucin: makes saliva sticky
- Lysozyme: breaks down bacteria
- IgA
- Defensins: target bacteria
- Electrolytes: Na & Cl
Parasympathetic (CN 7&9) –> watery, enzyme-rich saliva
Sympathetic –> mucin-rich saliva, mainly from the sublingual gland
Salivary glands + composition
Parotid: only serous (watery, amylase) –> lots of tartar buildup *Target for mumps
Submandibular: mostly serous with amylase
Sublingual: mostly mucous with lipase, activated by low pH (only works in the stomach)
Three phases of swallowing
- Voluntary
- Oral cavity + tongue, you choose to bring food –> oropharynx
- Pharyngeal
- Deglutition reflex initiated by stretch of oropharynx (deglutition centre in brainstem - medulla + low pons)
- Skeletal muscle: you can still stop it at this point
- Closing off of nasal cavity (soft palate + uvula rise to protect upper airway)
- Closing off of trachea (epiglottis + larynx rise)
- Relaxation of upper esophageal sphincter (to allow bolus to pass)
- Esophageal
- Peristalsis: first 1/3 is voluntary (skeletal), second 2/3 is not voluntary (smooth muscle)
Anatomy of esophagus
- Glued into place by the adventitia (CT)
- Two kinks and 1 hiatus
- Kink 1: passing bifurcation of trachea
- Kink 2: passing behind left atrium
- Esophageal hiatus: in skeletal muscle of diaphragm
Esophagus histology
- Mucosa: stratified squamous epi (needs lots of layers –> friction from food)
- Lamina propria: CT that glues down the epithelium to underlying layers (this is where BVs + nerves are)
- Muscularis mucosa: thin layer of SM, puts mucosa into folds
- Submucosa: CT that glues down mucosa to underlying layers
- Muscularis: 2 muscles that work together to cause peristalsis
- Inner circular: sphincter-like motion
- Outer longitudinal: shortening
- Adventitia: CT that glues esophagus in place in cervical + thoracic regions
Esophageal phase of swallowing
Controlled by the enteric NS
- Circular muscles contract to constrict the pathway for bolus to go through
- Longitudinal muscles contract to shorten the bolus’ pathway
- LES only opens for bolus: so no stomach acid enters esophagus
Reasons for GERD
- LES pressure is too low
- Gastric pouch = part of stomach goes through esophageal hiatus + ends up in thorax, results in the LES not getting enough help from diaphragm to close
GERD
- Acid in esophagus = heart burn, can even burn through muscularis layer
- Effects are worsened by:
- Smoking + alcohol (relaxing of LES)
- Coffee, chocolate, peppermint + stress (increased acid production)
- Obesity + pregnancy: more pressure = pushing on stomach = into esophagus
Treatment options
- Smaller meals
- Maintaining upright position
- Antacids
