Avian Anatomy and Physiology

Question 1

What features of avian anatomy allow them to fly?

Answer 1

• Wings instead of forelimbs
• Feathers (streamline, contour and aid steering)
• Many bones are fused (weight reduction, strenght and stability)
• Numerous bones pneumatised/hollow - less weight
• Enlarged sternum (origin of flight muscles)
• Ventral musculature and centre of gravity
• Triosseal canal heping with the movement of wings

Question 2

What is the coracoid?

Answer 2

Additional structure in birds that acts as a brace between the sternum and the wing

Question 3

What muscles are associated with flight in the bird?

Answer 3

Supracoracoideus muscles (L-humerus to R-humerus via sternum)
Pectoralis muscles connecting sternum and humerus ventrally

Question 4

What is Furcula and what is its function?

Answer 4

Clavicles of the bird fused acting as a strut for the avian shoulders - articulates to each of the scapulae - forms the triosseal canal in conjunction with the coracoid and scapula

Question 5

What is the role of the triosseal canal?

Answer 5

Houses the tendon that connects to the supracoracoideus muscles to the humerus - this system is responsible for the lifting of the wings during the recovery stroke

Question 6

What different types of diets do birds have and give examples of species

Answer 6

Herbivores - Waterfowl
Granivore - Parrots, Finches etc.
Carnivore - Eagles, Falcons, Owls

Question 7

What are the species specific differences in the Avian GIT?

Answer 7

Relatively short GIT tract (less weight) - includes a crop in some species which is a outpouching of the oesophagus for food storage, a gizzard which is where mechanical breakdown occurs and the proventriculus which is the glandualr part of the stomach.
Cloaca - termination of urinary and intestinal tract with no omentum

Question 8

Describe the reproductive anatomy of avian species

Answer 8

Males - paired testes internal craniventral to the kidneys most species have no phallus waterfowl and poultry have phallus - protrusible in some species
Females - most species have single left ovary and oviduct - egg production varies (25 hours in poultry, 48 hours in parrots etc)
Many species are sexually monomorphic sexing is done via DNA testing

Question 9

What are the functions if respiration in avian species?

Answer 9

Gas exchange as well as thermoregulation

Question 10

How is the trachea of avian species different to mammals?

Answer 10

2.79x larger and 1.3x wider
Tracheal resistance similar
Dead space larger by 4.5 times
Birds have large tidal volume and lower respiratory frequency

Question 11

What are the airsacs in avian species for and what is their anatomy?

Answer 11

Usually 9 air sacs that are thin walled (transparent) no active role in gas exchange and act as bellows pushing air over the lungs
1 Interclavicular airsac
2 Cervical
2 Cranial thoracic
2 Caudal thoracic
2 Abdominal

Question 12

What path does the air follow starting with the trachea

What is the structure of the bronchiole tree in avian species?

Answer 12

Trachea - Mesobrochi - Ventrobronchi - Parabronchi
Parabronchi are several mm long and 0.5-2mm in diameter, the walls contain air capillaries surrounded by blood vessels
The parabronchi lead into larger dorsobronchi which lead back to mesobronchi

Question 13

How is air moved trough the respiratory tract in avian species?

Answer 13

During inhalation the air moves into the caudal air sacs and lungs - air also moves through the parabronchi into the cranial air sacs
During exhalation air moves out of the caudal air sacs into and through the parabronchi simultaneously air moves out of the cranial air sacs into the trachea and out of the body - 2 cysles for air to go in and out

Question 14

Where is calcium found within birds?

Answer 14

As hydroxyapatite in bone - highly labile source in birds
Intracellular
Extarcellular Calcium(ionised calcium and protein bound) ionised = active form

Question 15

What hormones are responsible for calcium homeostasis in birds?

Answer 15

Vitamin D3
Parathyroid Hormone
Calcitonin

Question 16

How do birds obtain Vitamin D3?

Answer 16

Dietary or Dermal source (UVB) - requirments for enzymatic converison to active metabolites

Question 17

e.g. UVB stimulates 7-dehydrocholesterol

What are the metabolic pathways associated with the sources of Vitamin D3?

Answer 17

1. 7-dehydrocholesterol (Provitamin D) production in the liver which is secreted onto the skin is then exposed to UVB which activates the Provitamin into Cholecalciferol (Vitamin D3)
2. Or Vitamin D3 can be obtained in the diet

Question 18

How is Vitamin D3 metabolised by the liver?

Answer 18

Cholecalciferol is transported to the liver where it is converted to calcidiol which is then transported to the kidney and converted into its active forms (mainly calcitriol which is responsible for increasing calcium levels in the blood by acting on the gut, kidney and bone)

Question 19

What are the functions of Vitamin D3?

Answer 19

• Facilitation of intestinal absorption of dietary calcium
• Facilitation of uptake in calcium from bones or deposition of calcium into bone depedning on body calcium levels
• Decreases renal excretion of calcium if blood level low
• Sex hormones in female birds affect calcium storage, mobilisation and transportation

Question 20

Why are high calcium levels required in egg laying birds?

Answer 20

Egg shell comprised of calcium (requires around 10% of the bodies reserve in calcium) therefore require more calcium in the diet

Question 21

What is the role of parathyroid hormone in calcium maintenence?

Answer 21

• Parathyroid hormone produced in response to low blood calcium
• Works in minutes in avian species
• Increases renal tubular reabsorption of calium
• Increased bone resorption
• Increases conversion of Vitamin D3 into calcitriol in the kidney

Question 22

What is Metabolic Bone Disease and how does it occur?

Answer 22

Group of diseases caused by calcium deficiencies and associated hyperparathyroidism
e.g. Secondary hyperparathyroidism - homeostasis of blood calcium at the expense of skeletal calcification (soft bones, growth deformities) causd by dietary issues (seeds low in calcium high in phosphorus low in Vitamin D3)

Question 23

What are the major causes of Metabolic Bone Disease in birds?

Answer 23

• Diet (dietary calcium or vitamin d deficiency/ Inappropriate calcium to phosphorus ration)
• UVB exposure