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| − | == Changes in Composition of the Egg during Incubation ==
| + | <big><center>[[Reproductive System|'''BACK TO REPRODUCTIVE SYSTEM''']]</center></big> |
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| − | *As the embryo grows within the egg, the composition of the egg changes.
| + | <big><center>[[Reproductive_System#Exotics|'''BACK TO EXOTICS''']]</center></big> |
| − | * Both [[Egg Composition and Formation - Anatomy & Physiology#Yolk|yolk]] and albumin diminish.
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| − | ** Yolk providing energy for growth and maintenance of the embryo.
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| − | ** 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]].
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| − | * Water is produced when yolk fat is oxidised.
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| − | * Water lost from the egg is replaced by air, creating the 'air cell' at the blunt end of the egg.
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| − | * Embryo punctures the [[Egg Composition and Formation - Anatomy & Physiology#Embryonic_Membranes|chorioallantoic]] and [[Egg Composition and Formation - Anatomy & Physiology#Shell_membranes|internal shell membrane]].
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| − | ** Able to begin pulmonary ventilation, rebreathing the 'air cell' gas.
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| − | ** Transition from diffusive respiration through the [[Egg Composition and Formation - Anatomy & Physiology#Embryonic_Membranes|chorioallantois]] to breathing through the [[Lungs_- Anatomy & Physiology|lungs]].
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| − | == Heat Transfer to the Egg ==
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| − | === Heat Transfer to the Egg ===
| + | * [[Exotics - Changes in Composition of the Egg during Incubation - Anatomy & Physiology|Changes in Composition of the Egg during Incubation]] |
| − | | + | * [[Exotics - Heat Transfer to the Egg - Anatomy & Physiology|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. | + | * [[Exotics - Development of Physiological Functions - Anatomy & Physiology|Development of Physiological Functions]] |
| − | * Most birds develop a seasonal bare patch of skin known as the ''''brood patch'''' on part of the thorax and abdomen.
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| − | ** 'Brood patch' is in direct contact with the egg to permit a greater heat transfer than if there were feathers between them.
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| − | * At the same time, there is an increase in the size and number of blood vessels in the bare skin.
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| − | ** Serves to increase heat transfer, as hot blood runs closer to the surface. | |
| − | * Adult can adjust the rate of heat transfer by:
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| − | ** Standing or leaving the egg.
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| − | ** The closeness with which the 'brood patch' is applied to the egg.
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| − | ** Responding physiologically to the temperature of the egg, thus increasing or decreasing metabolic heat production.
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| − | * 'Brood patch' temperature is 34.9-42.4ºC.
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| − | ** This is 1.1-5.5ºC higher than the egg temperature.
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| − | === Heat Loss from the Egg ===
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| − | * 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]].
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| − | * If the egg is in a nest, the nest will also provide resistance to heat loss. | |
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| − | [[Category:Avian Reproduction]] | |
| − | [[Category:Bullet Points]]
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