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Egg Incubation Physiology - Anatomy & Physiology (view source)
Revision as of 14:05, 5 July 2012
, 14:05, 5 July 2012→Heat Loss from the Egg
== Changes in Composition of the Egg during Incubation ==
::[[Exotics - Development of Physiological Functions - Anatomy & Physiology|Development of Physiological Functions]]
*As the embryo grows within the egg, the composition of the egg changes.
* Both [[Egg Composition and Formation - Anatomy & Physiology#Yolk|yolk]] and albumin diminish.
** Yolk providing energy for growth and maintenance of the embryo.
** Albumin providing protein for the embryo and giving up water, which is lost through pores in the [[Egg Composition and Formation - Anatomy & Physiology#Shell|shell]].
* Water is produced when yolk fat is oxidised.
* Water lost from the egg is replaced by air, creating the 'air cell' at the blunt end of the egg.
* Embryo punctures the [[Egg Composition and Formation - Anatomy & Physiology#Embryonic_Membranes|chorioallantoic]] and [[Egg Composition and Formation - Anatomy & Physiology#Shell_membranes|internal shell membrane]].
** Able to begin pulmonary ventilation, rebreathing the 'air cell' gas.
** Transition from diffusive respiration through the [[Egg Composition and Formation - Anatomy & Physiology#Embryonic_Membranes|chorioallantois]] to breathing through the [[Lungs_- Anatomy & Physiology|lungs]].
== Heat Transfer to the Egg ==
=== Heat Transfer to the Egg ===
* Transfer of heat from the body to the egg is the most important contribution of the incubating adult to incubation.
* Most birds develop a seasonal bare patch of skin known as the ''''brood patch'''' on part of the thorax and abdomen.
** 'Brood patch' is in direct contact with the egg to permit a greater heat transfer than if there were feathers between them.
* At the same time, there is an increase in the size and number of blood vessels in the bare skin.
** Serves to increase heat transfer, as hot blood runs closer to the surface.
* Adult can adjust the rate of heat transfer by:
** Standing or leaving the egg.
** The closeness with which the 'brood patch' is applied to the egg.
** Responding physiologically to the temperature of the egg, thus increasing or decreasing metabolic heat production.
* 'Brood patch' temperature is 34.9-42.4ºC.
** This is 1.1-5.5ºC higher than the egg temperature.
=== Heat Loss from the Egg ===
* Heat loss from the egg is prevented by a thin boundary layer of air adjacent to the [[Egg Composition and Formation - Anatomy & Physiology#Shell|shell]].
* If the egg is in a nest, the nest will also provide resistance to heat loss.
[[Category:Avian Reproduction]]
[[Category:Bullet Points]]