Avian A&P Flashcards
Describe the avian bones
Reduced number as some as fused together
Reduced density of bones
Lightweight and Strong
Some bones fused into single ossification e.g. pygostyle (tail bone)
Thinner cortex in the bone
Many long bones are hollow and filled with air spaces - pneumatic bones
What is the purpose of fused bones?
Makes the skeleton more rigid
Describe the sternum of birds
Laterally flattened to form an extended keel bone
What is the function of the keel?
Provides a large surface area for the attachment of flight muscles
(flightless birds don’t have a keel)
Describe ribcage
Uncinate processes add strength to the ribcage. Point backwards between each rib. Also give extra space for more attachment.
First few ribs are short and incomplete.
Describe the vertebrae of birds
Elongated neck means more cervical vertebrae. Makes neck flexible. Many have 13-25 cervical vertebrae
Approximately 12 caudal vertebrae. End of these fused together to form pygostyle
What is unique about the bird’s axial skeleton?
Only vertebrates to have a fused collar bone called ‘furcula’ or ‘wishbone’
What is the coracoid?
A large bone that lies between the keel and each shoulder joint to support the wing.
What do baby birds have?
Egg tooth. Used to help break out the shell and then falls out
Describe the skull of birds
Highly mobile kinetic skull
Wide gape with the elastic hinge
Cranium is very light with no suture lines.
Upper and lower jaw can move independently
No teeth- replaced by light beak (keratinised)
Sclerotic rings around orbits to support eye (mammals don’t have these)
Single occipital condyle attaches the skull to the atlas - allows bird to rotate head 180 degrees (mammals have 2)
Quadrate bone between mandible and skull allows a wide gape
Describe the pelvic girdle of birds
Extensive fusion = Synsacrum. Provides support for shock of take off and landing
3 paired bones
Incomplete
Lacks pelvic floor - allows passage of eggs
Describe adaptions in birds feet
Water birds have webbed feet
Claws
4 toes:
Psittacines are Zygodactyl (2 toes facing forward and 2 toes facing backwards) - for climbing
Passerines are Angiodactyl (3 toes facing forwards and 1 back) - for perching and grasping
What do medullary bones store?
Ca for egg production
What glands do birds have?
No sweat glands
Have preen gland on upper surface of tail
(waterproofing)
Describe the digestive system regarding teeth and the mouth
Beak replaces teeth and lips of mammals - Initiates mastication
Saliva of birds is more mucoid to lubricate food
Waterfowl have modified tongue to scoop up water and has bristles to filter it.
Lightweight beak
Why are there differences between the digestive systems of birds and mammals?
Modifications allow maximum energy absorption of food due to high metabolic rate. Digestive tract in birds is relatively short to keep it lightweight.
What is the difference between the oesophagus in mammals and birds?
More distensible in birds and lies on RHS
What lies between within the oesophagus? What is its function?
Crop - oesophageal diverticulum
Used for storage of food when stomach is full. Also used to moisten and soften food.
Allows the bird to only eat a few times a day instead of all day.
Pigeons have crop milk
Owls and penguins lack a crop
Describe the small intestine in birds?
Chemical digestion site
Short and highly convoluted
Thin-walled, narrow and lined with villi
Name the 2 parts of the stomach
- Glandular Proventriculus
2. Muscular Ventriculus (Gizzard)
What is the function of glandular proventriculus?
Production of gastric juices
Propulsion of food into the stomach
Indigestible material is regurgitated into pellets