Anatomy of Birds
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What class are birds in?
State three areas of the body that have been adapted to reduce the weight of birds and allow them to fly
- Digestive system
- Respiratory system
- Urogenital system
State three adaptations of the body that promote the power of birds and allow them to fly
- They are endothermic
- Muscles and tendons
- Cardiovascular system
- Digestive system
- Respiratory system
- Method of locomotion
In birds there is an increased/decreased number and size of bones?
What area in particular has been adapted dramatically in birds to reduce its weight?
State three adaptations of the bird skull
- Birds lack teeth - they have been replaced by a bill
- Lots of fusion of bones in the skull
- Birds have a single occipital condole
- Large eye orbits
How has the vertebral column in birds been adapted to reduce its weight?
- There are more cervical vertebrae than in mammals.
- There is also fusion of the thoracic, lumbar and sacral vertebrae into Notarium, Synsacrum and Pygostyle.
- They have a reduction and fusion of ribs
What adaptation of the vertebral column is the site of attachment for flight muscles?
The deep keel on their sternum
True or false: birds have a pubic symphysis?
False - birds have a free pubis. There is no pubic symphysis joining the two bones.
Why are feathers important in the avian integument?
They reduce weight and are important for thermoregulation
How do birds regulate their temperature?
Birds use thermopanting to cool themselves as they lack sweat glands.
What type of glands do most birds have to keep their skin moist?
Uropygial glands or 'preen glands'. These secrete oil which the birds work through their feathers and skin to keep them in good condition.
When are the testes/ovaries not regressed in birds?
During the breeding season
Where do the ductus deferens/oviducts open onto?
True or false: avian kidneys are similar in structure to mammalian kidneys?
False - the kidneys contain a mixture of reptilian and mammalian nephrons (some possess loops of Henle but others do not)
Do birds possess a urinary bladder?
What structures receive faeces, uric acid and sperm/eggs in birds?
The cloacca and vent
What is the cloacal bursa?
The cloacal bursa is a collection of lymphatic tissue where B cells mature in birds
What is the source of vocalisation in birds?
The syrinx (birds lack a larynx)
Why must care be taken when restraining birds, with regards to putting pressure on their chest cavity?
Birds lack a diaphragm so care must be taken not to put too much pressure on their chest cavity
What are the functions of air sacs?
- Air sacs make their body light for flight
- They also draw air through the lungs, which are non-elastic in birds.
Describe the unidirectional airflow through birds during inspiration and expiration
Lungs > caudal air sacs > lungs > cranial air sacs
True or false: gas exchange occurs in the air sacs?
False - there is no gas exchange in the air sacs
What are some of the locations of air sacs in the body?
- Paired cervical
- Paired cranial and caudal thoracic
- Paired cranial and caudal abdominal
- Unpaired clavicular
In birds the oesophagus forms a diverticulum called the ...?
What is the function of the crop?
This allows birds to stores as much food as possible before it eventually progresses to the stomach
Which species do not have a crop?
Owls, gulls and penguins
What is the gizzard?
A highly mechanical muscular organ which, in seed eating birds, is used to break down seeds. In birds of prey the debris (bones, etc) remain in the gizzard and are extruded back up the oesophagus and out through the mouth.
What are the two flight muscles in birds? And what are their functions?
- Pectoral - creates the downstroke
- Supracoracoid - raises the wing
What is the location of the flight muscles relative to each other?
The supracoracoid muscles sit medial to the pectoral muscles
How many chambers are there in the avian heart?
True or false: birds have nucleated erythrocytes?
Which part of the forelimb is the point of attachment for a) the flight muscles b) the secondary flight feathers c) the primary flight feathers?
- a) humerus
- b) radius and ulna
- c) carpo-metacarpus and phalanges
Which parts of the wing are fused to form a stiff brace?
The scapula, coracoid and clavicle
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