Avian and Reptilian GI and Urogenital tracts Flashcards
What are the components of the avian GI tract?
- mouth
- oesophagus
- crop
- proventriculus
- ventriculus (gizzard)
- intestine
- caeca
- rectum
- cloaca
What is the difference between avian organs and mammalian?
- large number of organs with greater number of interorgan cooperation than mammalian counterparts
Describe the mouth of an avian - in terms of digestion:
- rapid transit of food through the mouth
- lack of mastication and relatively low addition of saliva
- low number of taste receptors results in poor taste acuity
Describe the oesophagus in avian’s:
- oesophagus extends down the neck into the thoracic cavity and is expandible due to series of longitudinal folds
What do the longitudinal fold in the oesophagus allow for?
- can stretch lengthways to accommodate prey (owl)
The oesophagus widens into the crop just before entering the thoracic cavity - what does the crop allow for?
- bird can constantly have a supply of food in some species (seed eating)
- owls have no crop
What issues can occur in the crop?
- crop impaction
- sour crop when food isn’t passing usually due to a GI issues further down the tract
What is present in the proventriculus - glandular stomach?
- tubular glands = secrete mucous
- gastric glands = secrete HCL and pepsinogen
What is the structure and what happens in the ventriculus - muscular stomach?
- 2 pairs of smooth muscles arranged in distinct bands that both originate and terminate on a circular tendon
- can have grit here to aid in mechanical digestion
Describe the duodenal loop of the intestines in birds:
- encircles the pancreas and receives the pancreatic and hepatic ducts (empty here)
Describe the jejunum and ileum in birds:
- they are not clearly demarcated
Where does the short colon in birds empty?
- into a pair of caeca
What can food do in birds?
- move between both ventriculus and proventriculus
Raptors can regurgitate food - where does the regurge come from?
- from the proventriculus
What are the caeca like in psittacine and passerines and then in domestic birds?
- 2 distinct caeca
- psittacine and passerines = vestigial
- domestic birds - very well developed
What does the rectum extend between in birds?
- extends between the ileocecal junction and the cloaca
What is the cloaca?
- the terminal junction into which digestive tract and urogenital ducts empty
What are the accessory organs to the GIT in some species of birds?
- liver
- gall bladder (not all species)
- pancreas
What type of teeth do snakes and lizards have?
- acrodont - on summit of piece of bone and are an extension of this bone
What are the teeth like in non-venomous snakes?
- have teeth on 4 sets if bones
- maxilla, dentary, palatine and pterygoid bones
How do the palatine and pterygoid allow for larger prey to be taken in?
- separate bones moving independently if each other allowing prey to be ratcheted into mouth
- there is no dislocation of the jaw
- bones are joined by ligaments
What limits the size of prey snakes can take in?
- the size of the skull
In a normal resting state what is the glottis like in snakes ?
- always closed
What can the snake di with its glottis while feeding?
- snakes can extend glottis out the side of their mouth while eating to allow for respiration
How can snakes ingest prey significantly bigger than themselves?
- snakes have loosely connected jaw bones and elasticated skin allowing them to ingest prey significantly bigger than themselves
Describe the reptilian oesophagus?
- ciliated epithelium with numerous goblet ells in most reptiles
- when relaxed has several longitudinal folds to allow greater distensibility to accommodate large food items
What happens in the reptilian stomach?
- mechanical and chemical digestion
Where is the reptilian stomach located?
- located on the left side of the body and attaches to the left lung
What does the cardiac region of the reptilian stomach have?
- cardiac region has a glandular mucosa secreting mucous and HCL
What aids in the movement of ingesta through the digestive system of a snake?
- body contractions
What differences do reptilians have in terms of lack of organs?
- lots do not have a diaphragm
- not all reptiles have two lungs
What is the liver like in reptiles?
- largest visceral organ in reptiles
- consists if two lobes
- caudal to the heart and mostly cranial to the stomach
Where is the pancreas located in a reptile and what does it do?
- located along the duodenum secreting bicarbonate and pancreatic digestive enzymes
What are the intestines like in the reptile?
- function in digestion and absorption
- organ size is dynamic and responsible due to fasting period - intestines can shrivel to conserve energy then accommodate eating again
What reptiles is the caecum present in and absent in?
- present in most lizards and chelonians
- absent in most snakes
What species is the caecum largest in?
- tends to be larger in herbivores and omnivorous species than in carnivores
What the function of the large intestines in reptiles?
- functions to reclaim water ions and degradation of complex carbs
What is the cloaca like in reptiles?
- have dual system allows this to move forwards and backwards
- common opening of the digestive and urogenital tracts
