avian git

pregastric system

• how is mechanical disruption of food achieved

• how is oesophageal peristalisis achieved

• what do most birds have

• what happens to food being swallowed

• do not masticate so mechanical disruption of food is accomplished by beak and gizzard

• esophagus is large in diameter

• esophageal peristalsis is aided in most birds by extension of the neck

• most birds have a crop which varies from a simple expansion of the esophagus to one or two esophageal pouches

• depending on the state of contraction food being swallowed is diverted into the crop then later propelled into the stomach by waves of peristalsis in the crop

stomach

• 2 parts

• shapes

• separation

• function

• have a glandular stomach or proventriculus and a muscular stomach or gizzard

• gizzard is disk shaped, very muscular and in many birds contain small stones that facilitate grinding of foodstuffs

• one of the gizzards two orifices recieves ingesta from the proventriculus and the other empties into the duodenum

• a cycle of contractions involving 2 stomachs force feed back and forth between two grinding it and increasing exposure to digestive enzymes

• also periodic retropulsion of duodenal contents back into the stomach

• final type of motility is seen in regurgitation of pellets of bone, hair and feathers from the stomach of raptors

• proventriculus is where digstion is initiated and ts epithelium contains tubular glands which secrete mucous and gastric glands secrete hydrochloric acd and pepsin

• the gizzard mechanically massages and grinds food to reduce its size and increase surface area, and is the location of action of HCl and pepsin

• gizzars is consisted of 2 pairs of smooth muscles arranged n disticnt bands that both originate and terminate ofn a circular tendon which provide mixing and grinding actions during contraction

• these muscles have a high myoglobin concentration

• interior lining of the gizzard contain deep tubular glands that prodce protein rich secretion that hardens into rods which forms the cuticle linng

• pyloric fold separates the gizzard from the small intestine

small intestine

• what is the intestine surrounded by and what does this do?

• duodenum, jejunum, ileum

• proximal small intestine recieves bile from the liver and digestive enzymes from pancreas and absoptive epithelial cells are decorated with essentially the same battery of enzymes and transporters as in mammals

• intestine is surrounded by inner circular and outer longitudual muscle layers which mix the digesta and propel

large intestine

• what serves as the common opening of the digestive, reproductive and urinary system and what happens here?

• where does antiperistalsis originate

• how many ceca

• short colon and typically a pair of ceca

• short villi extend into the lumen of the colon

• cloaca is an expanded tubular structure that serves as the common opening of the digestive, reproductive and urinary systems which opens to the outside of the bird as the vent

• absorption of water and electrolytes

• antiperistalisis that originates in the cloaca is a prominent pattern of motility in the avian colon and has been suggested to assist not only in filling the ceca but to flush urine from the cloaca into the large gut for absorption of water

• in some species ceca are important sites for fermentation

adaptations for diet

• ridges in tomia of their beak for slicing the hull

• dexterous tongue for manipulating seed and diposing the hull

overview

mouth

esophagus

crop

proventriculs

ventriculus/gizard

intestine

ceca

rectum

cloaca

beak

• has a keratin sheath growing from the upper and lower mandible which forms the beak

• subtle changes occur as food types change

• the outer edges, the tomia are sharp to facilitate cutting seed coats

oral cavity

• what is the anterior part roofed with and what does it contain

• what do granivorous species have

anterior part of the oral cavity is roofed with a hard palate whch in finches, canaries, budgerigas and cokatiels contains 2 ridges that facilitate removal of shell from seeds before consumptin

granivorous species have well developed tubular salivary glands scattered in groups around the lower oral cavity, tongue and pharynx

where are most taste buds located

palate and posterior tongue

palatal taste buds are usually located in regions where the epithelium is soft and glandular- typically near the salivary glands

tongue , oral cavity and beak have a rich supply of touch recepters

esophagus

• where does it extend into and where does it terminate

• in the budgerier where is it relative to the trachea

• what happens in what layer

• adaptations through…

• epithelium

• what does it widen into

• extends down the neck into the thoracic cavity and terminates in the proventriculus

• in the budgerigar the esophagus is dorsal to the trachea in the anterior region of the neck and then runs along the right side

• peristaltic contraction of inner cicruclar and outer longitudnal muscles in the tunica muscularis propels food poseriorly through

• is expandible to aid in swallowing large bits of food through a series of longitudinal folds which is encriched with mucou glands

• epithelial lining is thik and cornified

• in many species the esophagus widens into a crop beore entering the thoracic cavity

• some granivorous spcies do not have a true crop ut have a very expandable esophageal pouch

stomach

• glandular (proventriculus) and musclar (gizzard)

• proventriculus is where stion is initiated and ts epithelium contains tubular glands which secrete mucous and gastric glands secrete hydrochloric acd and pepsin

• the gizzard mechanically massages and grinds fod t reduce its size and increase surface area, and is the location of action of HCl and pepsin

• gizzars is consisted of 2 pairs of smooth muscles arranged n disticnt bands that both originate and terminate ofn a circular tendon which provide mixing and grinding actions during contraction

• these muscles have a high myoglobin concentration

• interior lining of the gizzard contain deep tubular glands that prodce portein rich secretion w=that hardens into rods which forms the cuticle linng

• pyloric fold separates the gizzard from thesmall inttetine

rectum- where does it extend between

extends between the ileocecal junction and the cloaca

cloaca- what empties here

• terminal chamber into which the digestive tract and urogenital ducts empty