Download Development of the Avian Embryo: A Behavioural and by B. M. Freeman, Margaret A. Vince (auth.) PDF

By B. M. Freeman, Margaret A. Vince (auth.)

In this ebook we've got defined the foremost occasions of embryonic improvement and thought of the underlying mechanisms which bring about the creation of a workable hatchling. we've got, because the subtitle of the ebook shows, con­ centrated on behavioural and physiological subject matters: it isn't our function to contemplate the early embryology of the poultry - that's accurately coated through different texts - yet now we have integrated morphogenetic details the place applicable. the shape of the ebook was once dictated through a trust that curiosity during this point of improvement isn't constrained to embryologists, biochemists and physiolo­ gists. for this reason after describing the stipulations during which the egg often develops we've got thought of first the complete embryo: what it really is like at diverse phases, what it does, the way it will get from one place to a different in the shell and the way, later, it involves engage with the broader environ­ ment of the nest. basically after this have we thought of the improvement of the worried and sensory mechanisms on which this modification relies and at the challenge of the extent of behavioural adulthood with which the chick emerges from the egg. With the most traces of improvement defined we've got, within the moment a part of the ebook, became to an in depth attention of the body structure of improvement: starting from what could be with ease defined because the 'life-support' platforms - gaseous trade, provision of power, and so on. - to the of hormones in avian development.

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Extra resources for Development of the Avian Embryo: A Behavioural and Physiological Study

Example text

During these first days the albumen, initially surrounding the yolk, loses water rapidly, becomes more viscid and heavy and settles gradually towards the small end of the egg, a process which can be seen in Appendix 2, on days 2, 3 and 4. By the end of the third day the embryo is completely surrounded by the 20 GENERAL DEVELOPMENT amnion and fluid begins to accumulate within the amniotic cavity (compare Appendix 2, days 4B and 5B). The amnion in its turn is surrounded by the chorion, almost concentric with it (Fig.

Generally one side of the amnion contracts and a balloon expands over the other side, but sometimes two such balloons may appear simultaneously. When the balloon in one region contracts and collapses the contraction wave passes to the opposite region, where a new balloon is formed. These amniotic contractions and expansions compress the yolk sac which, now become flabby and elastic as its contents are absorbed, rebounds when the expansions come to an end. Between active amniotic movements, and passive recoil of the yolk the embryo is thrown into a 25 DEVELOPMENT OF THE AVIAN EMBRYO 'swinging' movement which becomes quite violent at the time when amnion contractions are at their height on the tenth day.

During the first few days the embryo is small and light and floats on the yolk. On the second day the head region begins to bend at the level of the midbrain from its original straight axis (the cranial flexure). At about the same time the head begins to be turned to the left and this turning continues in a tailward direction until, by about 96 h of incubation, the embryo lies on its left side (the half-way stage can be seen in Appendix 2, day 3). Meanwhile a second (cervical) flexure appears at about the junction of the head and trunk (Appendix 2, day 3) so that the head now forms a rightangle with the trunk.

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