Prehension, mastication, swallowing, and esophagus Flashcards
Facial muscles in herbivores vs. carnivores vs. omnivores
Herbivores: well developed
Carnivores:reduced, allowing wide mouth gape
Omnivores: reduced
Jaw motion in herbivores vs. carnivores vs. omnivores
Herbivores: no shear, more side to side and front to back action
Carnivores: shearing, minimal side to side
Omnivores:shearing, minimal side to side
Mouth opening in herbivores vs. carnivores vs. omnivores
Herbivores:small
Carnivores and Omnivores: large
Incisors in herbivores vs. carnivores vs. omnivores
Herbivores:broad, flat and spindle shaped
Carnivores:sharp and pointed
Omnivores: sharp and pointed
Canines in herbivores vs. carnivores vs. omnivores
Herbivores: short or long for defence or none
Carnivores and Omnivores: long, sharp, curved
Molars in herbivores vs. carnivores vs. omnivores
Herbivores: flattened with cusps
Carnivores: sharp, jagged, and blade shaped
Omnivores: sharp blades and or flattened
Prehension
-the seizing and conveying of food/liquid to the mouth
-methods vary between animals (domestic use lips, teeth and tongue; some animals will use forelimbs to hold food to pass into mouth)
Horse prehension
-horse uses its mobile lips extensively to prehend food
-while grazing these sensitive lips are drawn back to allow the incisor teeth to cut grass
Cattle and Sheep Prehension
-lips have limited movement relative to the horse
-tongue is main prehensile organ (long, rough, mobile)
>curves around herbage pulling It towards mouth
-pulled between the incisor teeth and dental pad and severed by movement of the head
Pig prehension
-naturally, pig digs up the ground with snout (rooting)
-once food is found, it is carried to mouth primarily by the action of the lower pointed tip
Carnivore prehension
-use teeth to capture prey
-limited use of lips
-toss and catch motion
Bird prehension
-a type of toss and catch although varies among species
Prehension and consumption
-prehension is correlated but not equal to consumption
>animals may move product into the mouth, but does not mean they will consume it
**higher palatability=consumption
Drinking
-divided into:
>suction through orifice or a tube (capillary action)
>use tongue (combo of muscular contractions and capillary action)
Pig drinking
-tongue extends into the liquid with the snout immersed
Dogs and cats drinking
-move fluid to the mouth using tongue
-tongue used to create a ladle and lifts up a column of water, drops head and closes mouth allowing water to move to back of cavity
>inability to tightly close lips means that they cannot form negative pressure required
-rapid and repeatedly
Cattle, pigs, horses drinking
-draw liquid into the mouth by suction that is created by inspiration and tongue contractions
Taste
-a group of sensations mediated by the chemosensory system located in the oral cavity
-typically 5 senses: sweet, salty, umami, sour, bitter (cats and chickens don’t taste sweet) present in all areas of tongue
Papillae
-present on tongue, epiglottic, soft palate
-each papillae contains thousands of organelles called taste buds
Taste buds
-each consists of 50-120 sensory cell that project microvilli that reach the mucous layer of the tongue
>each cell within a taste bud expresses one family of taste receptor (TR)
Papillae types
-circumvallate
-fungiform
-filiform
-foliate
Taste receptors
-transmembrane proteins
-binding of the ligand to the Taste receptor triggers an intercellular metabolic cascade followed by intercellular communication and then finally form synapses with sensory neurons
Animals with greatest # of taste buds from least to greatest
-chickens
-dog (some studies suggest dog greater than cat)
-cat
-man
-pig
-cow
Tongues role in prehension
-has bundles of muscles that run in all directions allowing for flexibility
-muscles attached to posterior tongue allowing retraction, protrusion, depression and elevation
What innervates the motor aspects of tongue?
-hypoglossal (CN XII) nerve
Sensory innervation of tongue
-rostral 2/3rd of tongue innervated by sensory lingual branch (CN V)- sensitive to temp, touch, pain
-Cranial Nerve VII- sensation of taste and carries parasympathetic fibers to the base of taste buds
-caudal 1/3rd innervated by lingual branch of glossopharyngeal nerve (CN IX)- carries taste sensation from taste buds and parasympathetic efferent fibers to the taste buds
Canine tongue
-stretch receptors in the tongue
-use tongue to lose heat by panting
Ruminant tongue
-tongue is heavily keratinized with long papillae
Feline tongue
-have long papillae for grooming
-tongue is rough
Porcine tongue
-most of the papillae are soft, long and directed caudally
Avian tongue
-tongue has a bone
-used primarily for food manipulation, rather than vocalization
Mastication
-chewing
-mechanical breakdown of food in mouth
Incisors
-procure food by tearing and scraping actions
Molars
-used for grinding food into smaller pieces
-Carnivores: imperfectly grind food
-Herbivores:spend more time grinding
Purpose of mastication
-to break food into smaller particles to increase SA for digestion and to mix food with saliva. Saliva ensures adequate lubrication of the food bolus for passage down esophagus
Stratified squamous epithelium
-lines the mouth, tongue, pharynx, esophagus and can withstand the mechanical trauma associated with this process
Papillae aiding in mastication
-lingual papillae aid in mastication by increasing the SA which increases area of contact and friction between tongue and food
Types of lingual papillae
> lingual papillae divided into mechanical and gustatory papillae. When not associated with taste buds=mechanical
4 major papillae
1.Filiform- fine, small cone-shaped, highly keratinized, most numerous and considered mechanical (not associated with taste buds)
2. Fungiform-club shaped projections
3. Foliate- short vertical folds
4. circumvallate- dome shaped
Jaw movements carnivores and omnivores
-jaw movement is mainly in the vertical plane (straight up and down motion) producing shearing action
Jaw movements herbivores
-includes up and down movements and lateral movements which create a mechanical grinding necessary to break down the plant material
-upper jaw is wider than the lower jaw and mastication occurs only on one side at a time
Teeth types
1.hypsodont
2.brachydont
Hypsodont
-high crowned teeth, grow continuously and found generally in herbivores and omnivores that eat fibrous material which needs to be ground
Brachydont
-short pointed teeth
-good for holding prey, tearing and shedding
-found in carnivores and humans
-begin to wear down following emergence. If the enamel is worn, the tooth begins to develop cavities
Salivary secretions
-saliva added to the bolus of food for chewing
-saliva contains digestive enzymes (amylase and lipase)
-produced by acinar glands located in the mandible and upper jaw in most species
Functions of saliva and chewing
-disruption of food into smaller particles
-formulation of bolus for swallowing
-initiation of starch and lipid digestion
-facilitation of taste
-regulation of food intake and ingestive behaviour
-cleansing of mouth and selective antibacterial action
-neutralize refluxed gastric contents
-mucosal growth and protection in the rest of GI tract
-aids in vocalization
Deglutition
-swallowing
-passage of food from mouth through pharynx and esophagus into stomach
-starts out as voluntary but becomes reflex during execution
Movements in the mouth (swallowing)-becoming a reflex
1.mouth and tongue bring food bolus into a position that is on midline between tongue and hard palate
2.Food is then in contact with receptors in the mucous membrane of the posterior wall of the pharynx
3.receptors send afferent impulses along the glossopharyngeal nerve (IX) and vagus nerve (X), and maxillary division of trigeminal nerve (V) to the swallowing center of medulla
4. swallowing in then involuntary (a reflex)
Movements in the mouth (swallowing)- coordinated actions
1.breathing stops momentarily
2.soft palate elevates, closing the pharyngeal opening of the nasopharynx preventing food entering nostrils
3.tongue pressed to hard palate
4.hyoid bone and larynx are pulled forward glottis is pulled under the epiglottis, blocking the laryngeal opening
5. all openings to the pharynx are now closed
6. upper esophageal sphincter relaxes to allow the bolus to enter the esophagus
Timing of motor events of swallowing
- Bolus in mouth=~0.6sec, then in pharynx
- Bolus moves through pharynx and upper esophageal sphincter= ~0.5sec
***therefore in esophagus in a total of 1.2sec
Esophagus
-tube structure extending from pharynx to the stomach
-passes through the thorax into the abdomen
Esophagus wall
-muscular layer
-submucosa (stratified squamous epithelium)
-mucosa (stratified squamous epithelium)
Smooth muscle vs striated muscle of esophagus
-most domestic animals entire esophagus is striated muscle
-birds-entirely smooth
-horses, primates, cats- portion is smooth muscle, rest striated
Striated muscle nervous control
-portions under control of somatic motor neurons in the vagus nerve
Smooth muscle nervous control
-under control of the enteric nervous system (ENS)
Myenteric plexus
-exists along entire esophagus (whether smooth or striated or both)
Esophagus Sphincters
-upper (cricopharyngeal muscle) and lower esophageal sphincters
>as food reaches end of esophagus, lower sphincter will relax and ingested material enters the stomach
>when not swallowing, the sphincters remain constricted
Food movement through esophagus
-body serves as a relatively simple conduit transferring food from pharynx to stomach; a ring of constrictions
-food propelled by peristalsis (propulsive movement)
-secondary peristalic waves may be needed to clear esophagus (if bolus is lodged, this secondary waves may lead to muscle spasms)
Swallowing and pressures
-swallowing increases intrapharyngeal pressure due to the reduction in volume of the closed pharyngeal cavity
>increased pressure results in the sudden relaxation of the pharyngeoesophageal junctions and opening of sphincter, and helps push the bolus through
>sphincter will close and prevent backflow=pressure increases
>peristaliic wave begins in esophagus moving food towards stomach
Lower esophageal sphincter relaxation
-mediated by VIP (neuropeptide produced by enteric nervous system neurons when a bolus of food is present
-this opening is often paired with peristaltic wave within esophagus pushing the bolus into the stomach
What prevents food being ejected back into the esophagus?
-stomach muscles are relaxed, reducing pressure in the stomach
Distension of stomachs
-affects meal size
-some carnivores have very distensible stomachs
-horses have small stomachs and little distention
Functions of the esophagus and sphincters
-movement of food from mouth to stomach
-protection of the airway and the esophagus
