GI Lecture 1-3 Flashcards
What is the GI tract?
concentric muscle cylinders lined with an epithelium.
What are the accessory organs?
Teeth, tongue, salivary glands, liver, pancreas
What are identifying characteristics for the carnivorous GI tract?
A big stomach
and a relatively short
intestinal tract. They must eat a lot before other competitors arrive. Slower absorption.
What are identifying characteristics for the ruminant GI tract?
fermentation in
the fore stomach system
What are identifying characteristics for the equine GI tract?
fermentation in the
large intestine. (Small stomach, large intestine is fermentive)
What are identifying characteristics for the Bird GI tract?
food store (the crop),
a glandular stomach (pro-
ventriculus), and a
muscular stomach (gizzard)
What are the major functions of the GI tract?
- Transportation of food
- Digestion
- Absorption
- Regulation (H2O and electrolyte balance)
- Immunologic Barrier (GALT)
- Thermoregulation
What is prehension?
How food is grabbed.
Species differ in feeding behavior
How does prehension occur in Horses?
lips (when eating from manger) or incisors (when grazing)
How does prehension occur in Cattle?
tongue (wrap the tongue around forage) and incisors
How does prehension occur in goat and sheep?
tongue and lips
How does prehension occur in pigs?
snout and mandible
How does prehension occur in carnivorous animals?
canines, incisors, and forelimbs
What is mastication?
The first act of digestion, involves the actions of the teeth, jaws, tongue, and cheeks
What are the key features of mastication in carnivorous animals?
very sparsely, movement of the mandible are vertical. Molars and
premolars in the upper and lower jaws move against each other like scissor blades
What are the key features of mastication in herbivorous animals?
spend long time masticating, upper and lower jaws are large providing
room for teeth with large chewing surfaces. Mastication movements are horizontal
Ruminants —-> Regurgitation, Remastication
What are the functions of movements of the GI tract?
To propel ingesta from one location to the next
To retain ingesta at a given site for digestion, absorption, or storage
To break up food material physically and mix it with digestive
secretions
To circulate ingesta so that all portions come in contact with
absorptive surfaces
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What kind of meal moves through the GI tract quicker, a hypocaloric meal or a hypercaloric one?
Hypocaloric- less to digest
What is Deglutition?
The first motility pattern in the GI tract is the deglutition Deglutition involves voluntary and involuntary stages and occurs after food has been masticated
What occurs in the voluntary phase (oral phase) of deglutitation?
Food is in the oral cavity and is molded into a bolus Using the tongue it will be pushed back into the pharynx
When food enters the pharynx
-> activation of sensory nerve endings ->initiation of the involuntary part of deglutition
What occurs in the involuntary phase (swallow reflex) of deglutitation?
Involuntary phase (swallow reflex): It occurs within the pharynx and esophagus -> it directs food into the digestive system (away from the upper airways)
What occurs step by step during deglutition?
- soft palate closes pharyngeal opening of nasopharynx
- tongue is pressed against hard palate to close oral opening.
- epiglottis is moved backwards, covering the entrance of trachea.
- upper esophageal sphincter opens and peristaltic contractions allows food to move through esophagus and trachea reopens and respiration continues
What are some disorders of deglutition?
Dysphagia which can result from neuromuscular disorder or mechanical obstruction.
What are the classification of Dysphagia?
- oropharyngeal dysphagia: due to malfunction of the pharynx and upper esophageal
sphincter (Parkinsons) - esophageal dysphagia: due to malfunction of the esophagus (ex: megaesophagus)
- Aspiration: a dysphagia in which food particles /fluids or stomach contents (acid reflux)
reach the upper airways
What is the regulatory center for energy homeostasis?
Hypothalamus
What is within the hunger center?
Nucl. Paraventricularis, lateral hypothalamus fields, perifornical region
What is within the satiety center?
Nucl. ventromedialis
What are stimulatory neuropeptides (Hunger) from the hypothalamus?
Neuropeptide Y (NPY) and Orexin
What are inhibitory (Satiety) neuropeptides from the hypothalamus?
Melanocyte-stimulating hormone (MSH)
Think of the labradors!
What are stimulatory (Hunger) non-hypothalamic hormones?
Ghrelin
What are inhibitory (Satiety) non-hypothalamic hormones?
Cholecystokinin (CCK), Peptide YY (PYY), Leptin (fat cells -> inhibits NPY release and activates MSH release and activity), Insulin (pancreas -> glucose availability)
What are the major salivary glands?
- Parotis (parotid gland)
- Mandibularis (mandibular gland)
- Sublingualis (sublingual gland
What are the small salivary glands?
- Ventral jaw glands
- Palate, pharyngeal glands
- Lips glands (labiales)
- Zygomatic glands
Which salivary glands provide the largest amount of secretion?
Parotis and Mandibularis account for 90% of salivary secretion
What is the primary function of saliva (digestive)?
Protection of the buccal mucosa and teeth
Facilitation of deglutition
Initiation of enzymatic carbohydrate
digestion (human and pigs -> amylase) -> pH regulation (HCO -)
What are the secondary functions of saliva?
• Immunologic function (Lysozyme, Ig‘s)
• Thermoregulation (panting in dogs)
• Defense mechanism in some species (llamas,
alpacas)
What makes up saliva?
99% Water and 1% electrolytes (Na+, K+, Cl-, HCO3-)
In the salivary gland, what is produced in the ducts?
Secondary Saliva (K+, and HCO-)
In the salivary gland, what is produced in the acinus?
Primary Saliva (Cl-, Na+. H2O)
What can be caused by disturbances in saliva production?
- Xerostomia (dry mouth)
- buccal ulcers
- dysphagia
- proliferation of bacterial population
- Cavities
What are the four routes secretions of the Gi tract reach their target tissue?
- Endocrine
- Paracrine
- Autocrine (not hormones, does not enter blood)
- Neurocrine
What is Neurocrine secretion?
secretions by enteric neurons that affect muscle cells, glands, and blood cells.
What is Autocrine secretion?
Secretions of a given cell regulate functions of the same cell.
What is paracrine secretion?
Secretions that diffuse through the interstitial space to affect other cells.
Where is secretin synthesized?
Duodenum, Jejunum