Salivary Glands and Swallowing Flashcards
Label this diagram of a basic salivon
Describe the components of saliva
- electrolytes
- proteins
- carbohydrate splitting enzyme (amylase)
- desquamated cells from mucosa
- lymphocytes
- mucin (if mucous secreting gland)
- 98-99% water
Why is bicarbonate ions important in ruminant saliva?
To buffer the ruminal acids
Where in the salivon is the primary secretion produced?
Epithelial cells within the acinus
Where is saliva modified after it is produced?
The ducts
Describe the modification of saliva in the ducts and what effects it
- Na and Cl resorbed
- HCO3 and K secreted into saliva
- osmolarity depends on flow
- faster flow = less time in ducts = less modification
- slow flow = hypotonic
Describe basal striation of the striated duct and its other components in the salivary gland
- infolding of the basal cell membrane -> high surface area
- many mitochondria
- Na/K-ATPase pump
Label the serous acini and the striated duct
Name the types of salivary cells and their secretion/role
Serous cells - watery secretion
Mucous cells - mucous secretion
Plasma cells - produce IgA (found around acini)
Myoepithelial cells - envelop each acinus
Name the different types of salivary ducts and their function
Intercalated ducts - secrete HCO3 and absorb Cl
Striated ducts - secrete K and absorb Na
Secretory ducts - convey saliva to the mouth
Label the cells and ducts of this mixed salivary gland
Name the functions of saliva (there is a lot)
- Wetting agent/lubrication, moistens food bolus to aid mastication and swallowing
- Lubricates oral mucosa
- mechanical washing of surfaces of teeth and mucosa to remove food, debris, microbes
- protective role via antimicrobial effect through enzymes, immunoglobulins
- antifungal and antiviral activity
- water solubkle food components dissolve in saliva
- enzyme action (amylase)
- buffering (in rumen and orally)
- phosphate buffer and aid to microbial growth to enable digestion
- hydroxyapatite in salive provides Ca ions to maintain enamel
- urea/ammonia in ruminants’ saliva returns to the rumen (protein recycling)
- thermoregulation in dogs and cars
- anti-foaming: salivary mucoproteins act with other agents to increase surface tension, frothy bloat can occur if absent
- peroxide-base antibacterial system: potassium thiocyanate in saliva is oxidised to form hypothiocyanate which it toxic to bacteria
What is pyalism
Hypersalivation
Describe the regulation of saliva production
Sympathetic NS: viscous, amylase, more protein, low volume
Parasympathetic NS: water, high volume, increase flow in response to taste, visual and olfactory stimuli, continuous basal flow
What stimulates salivation in a ruminants diet
the presense of long fibre e.g., grass, hay, in the reticulum near the cardia
Describe the parasympathetic pathway in saliva production
Parasympathetic supply travels along the trigeminal nerves
Name the different salivary glands
Parotid
Mandibular
Sublingual (mono and polystomatic)
Zygomatic
Buccal
Palatine
Gustatory (on the tongue)
Label the salivary glands and ducts
Describe the location, shape and secretion of the parotid gland
- ventral to base of ear
- V-shaped in carnivores (fits around auricular cartilage)
- C-shaped in herbivores (fits against caudal border of mandibular vertical ramus)
- Mixed serous/mucus saliva
- single duct
Clinical relevance of the parotid gland and horses on new grass
Becomes swollen
parotiditis
Describe the route of the parotid duct
Runs from craniomedial surface of gland across the masseter muscle
Opens in the upper buccal area by the maxillary fourth premolar (upper carnassial)
When does the parotid gland secrete saliva in ruminants
spontaneously when distal oesophagus/reticulum is mechanically stimulated
Label the parotid gland histology
Which species have a zygomatic gland?
Dogs and cats
What salivary gland is this?
Zygomatic
Where does the zygomatic duct open?
in upper buccal mucosa opposite the upper first molar - often seen as a ridge with red dots
What are the 2 parts of the sublingual glands
Polystomatic (‘many holes’) part
Monostomatic (‘one hokle’) part
Describe the monostomatic part of the sublingual glands
has a long sublingual salivary duct which runs next to the mandibular salivary ducts and opens with it at the sublingual caruncle
Describe the polystomatic part of the sublingual gland
comprises of 6-12 lobules with independent short salivary ducts opening sublingually near the frenulum.
Mucus secretions mainly
Where does the mandibular duct open
sublingual caruncle at base of linguinal frenulum
What type of saliva is produced from the mandibular gland
Mixed mucus/serous
Can alternate
Describe the connection between the mandibular and sublingual glands
Connective tissue capsule shared between monostomatic portion and mandibular gland
Mandibular and monostomatic part open into same place (sublingual caruncle)
In about 30% of dogs the mandibular and sublingual ducts merge
Name the extrinsic muscles linked with tongue function
Geniohyoideus
Genioglossus
Hyoglossus
Styloglossus
Mylohyoideus
Name the extra muscles that assist in swallowing
sternohyoideus
sternothyroideus
thyrohyoideus
Label the extrinsic muscles of the tongue
Describe the function of the tongue
Prehension
Food capture
Moves food over teeth
Prepares bolus for swallowing
Catches ruminal bolus during cudding
carries taste buds
suckling in neonatal mammals
Label the hyoid apparatus (dogs and cats)
Describe the function of the hyoid apparatus
Acts as a series of levers for muscle action
Keeps larynx in correct alignment
Anchor for tongue
Designs related to prehension and swallowing
Describe the mechanosense/touch (GSA) sensory nerve supply to the mouth
Lower jaw/tongue/gingiva/buccal mucosa/teeth : V3 ( mandibular)
Upper jaw/gingiva/mucosa/teeth: V2 (maxillary)
Pharynx/larynx: IX/X (glossopharyngeal/vagus)
Describe the chemosense/taste (SVA) sensory nerve supply to the mouth
Rostral 2/3 of tongue: VII/V3 (facial/mandibular)
Caudal 1/3 of tongue: IX (glossopharyngeal)
Caudal pharynx and larynx: X (vagus)
Describe the motor nerve supplies of the Masticatory muscles
Masticatory muscles (mylohyoiudeus and pterygoideus): V3 trigeminal
Describe the motor nerve supplies of jaw opening
Jaw opening (digastricus): rostral portion is V3, caudal portion is VII (facial)
Describe the motor nerve supplies of swallowing
Swallowing (muscles of pharynx, hyoids and larynx): IX and X (glossopharyngeal and facial)
Describe the motor nerve supplies of the intrinsic tongue muscles
Intrinsic tongue muscles: XII (hypoglossal)
Name the striated muscles involved in constricting and shortening the pharyngeal wall
Rostral - palatopharyngeus
Middle - hyopharyngeus
Caudal - thyropharyngeus
Name the striated muscle involved in dilation of the pharyngeal wall
Stylopharyngeus caudalis
Which nerves innervate the muscles that control the pharyngeal wall
Glossopharyngeal (IX)
Vagus (X)
What part of the mammals anatomy allows it to suckle and breath at the same time?
Hard palate
Name the 3 seals in a mammals mouth
Lips
Tongue against soft palate
Soft palate against epiglottis
Describe the 3 stages of swallowing
1st stage:
- tongue moves food around
- masticated food + saliva -> bolus
- up and back between fauces to pharynx
2nd stage:
- soft palate elevated -> closes posterior nares
- epiglottis covers larynx and trachea (breathing suspended)
3rd stage:
- oesophagus dilates
- bolus passes up and over larynx into oesophagus
- oesophagus recloses and epiglottis uncovers trachea
- bolus moves down oesophagus into stomach
Describe what is different about the mouth anatomy of chinchillas and guinea pigs and its clinical relevance`
Palatal ostium:
soft palate almost seals off the oropharynx from the naso and laryngopharynx
small hole (ostium) remains
This makes intubation almost impossible
