Lecture 19 & 20 - Avian GI anatomy, physiology & disease Flashcards
what structures in the oral cavity normally found in mammals are absent in birds?
lips
teeth
soft palate
no distinct separation between oral cavity and pharynx = oropharynx
no true intrinsic muscles in avian tongue
Name 1 airborne ruminant (there arent many)
hoatzin
what is the choana?
median fissure in palate connecting oropharynx and nasal cavity
what is tongue supported by?
the hyobranchial (hyoid) apparatus
where are salivary glands most prominant?
around the choanal slit, glottis and base of tongue
describe the action of swallowing
- pellet of food is seized by beak and moved by tongue to palate
- choanal opening reflexlively closed by muscular action - stops food entering nasal cavity
- rapid rostro-caudal movements of tongue move bolus into caudal part of oropharynx aided by caudally directed papillae
- infundibular cleft and glottis are reflexively closed
- propulsive action continued by laryngeal mound, etc.
describe the action of drinking
- fluid enters mouth by rapid rostro-caudal movements of tongue and accumulates in floor of oropharynx, caudal to tongue
- simultaneously larynx moves rostrally to lie close to choana
- head is raised and fluid flows around larynx and into esophagus mainly by gravity
common problems seen in oral cavity
hypovitaminosis A bacterial microabsceses candidiasis trichomoniasis capillariasis coccidosis
describe the internal surface of the esophagus
is longitudinally folded to increase distensibility of tube
abundant subepithelial mucus glands to lubricate food passage
describe location of esophagus
most of cervical esophagus is on the RIGHT side of the neck
what is another name for the crop?
ingluvies
where is the crop located?
dilatation of the esophagus
is the crop present in all species?
no!
are there mucus glands in the crop?
no!
describe the internal surface of the crop
its aglandular with a thin muscularis
innervation to the crop and esophagus is mediated by what nerve?
the vagus!
the esophagus and crop of granivores/omnivores have primarily what type of bacteria?
Gram (+) bacteria
transport of food down esophagus is aided by lubrication from what 2 things?
- esophageal glands
2. peristalsis
retroperistalsis
regurgitation of food stored in esophagus or crop
where is food stored if ventriculus is full?
crop and/or esophagus!
what does entry of food into crop do to contractions?
initially decreases them
when the ventriculus is empty, where does food go?
directly to the stomach - entrance to the crop is blocked by contraction of longitudinal muscle layer of esophagus
what is crop milk?
fed by pigeons and doves (columbiformes) to their young
how is crop milk produced?
produced by desquamation of fat-laden cells of the proliferated stratified squamous epithelium lining the very well-developed crop of both sexes
which pituitary hormone controls production of crop milk?
prolactin
describe the nutritional content of crop milk
rich in fat and protein
LACKS Ca and carbs!
common problems of esophagus and crop
paralysis impaction perforation infection burn injuries (in infant or debilitated birds that are gavage fed)
what is the demarcation between the esophagus and proventriculus?
there is none!
what is the primary function of the proventriculus?
production and release of gastric secretions: pepsin, HCl and mucus
proventricular folds are usually absent except in what two types of birds?
piscivores and carnivores
describe the distribution of glands within the proventriculus for: domestic fowl owls ostrich anhinga (a type of water bird)
domestic fowl = distributed throughout proventriculus
owls = present along longitudinal tracts
ostrich = present along circular patches
anhinga = separate diverticular
where do gastric glands open into?
proventricularis - visible to naked eye
what type of cell is seen within gastric glands and what do they secrete?
gastric glands contain only CHIEF CELLS.
chief cells secrete PEPSIN & ACID
what type of granules do chief cells contain? when are they increased?
chief cells contain zymogen or pepsinogen granules
they are increased during fasting or immediately after feeding
what type of flora is usually seen within the proventriculus?
Lactobacillus (Streptobacillus)-like flora
what are common problems seen with the proventriculus?
can be colonized with Candida sp. or bacteria
megabacteriosis
what is the main function of the ventriculus?
main functions are mechanical digestion and preliminary proteolysis
is grit essential for grinding action in the ventriculus?
no!
what is another name for ventriculus?
gizzard
what is the cuticle or koilin layer?
its present on the surface of the epithelium in the highly muscular ventriculus.
what produces cuticle (koilin layer)?
condensed or polymerized secretions of simple tubular glands and by entrapment of sloughed cells and cellular debris
how is cuticle (koilin layer) of ventriculus removed?
its constantly being worn away by grinding movements of ventriculus
it can also be eroded from perforating foreign bodies, heavy metal intoxication, or hyper-acidity
describe the appearance of the cuticle (koilin layer)
it has many longitudinal parallel folds and is usually brown, green or yellow as a result of regurgitation of bile pigments from duodenum
