Difference between revisions of "File:Bailey083.jpg"

From Embryology
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Eternod. From models by Ziegler.  
 
Eternod. From models by Ziegler.  
  
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The changes that occur in the simple cylindrical body after the ventral body wall is closed comprise the differentiation of the head, neck and trunk regions and the development of the extremities as appendages of the trunk. Even in Eternod's embryo (Fig. 83) the region where the brain is developing is greater in diameter than the other part of the embryo. Thus the beginning of the head is indicated by an increase in size due primarily to the growth of the brain. The end of the head region is bent ventrally almost at a right angle to the long axis of the embryo, the bend occurring in the mid-brain and being known as the cephalic flexure. This is the first of the flexures that appear as development proceeds. On the cephalic side of the yolk sac attachment is a protrusion which indicates the position of the heart in what now may be called the cervical region or neck. Between the protrusion caused by the heart and the fore-brain there is~a depression which foreshadows the oral and nasal cavities and is now called the oral fossa.
  
 
:'''Links:''' [[Book_-_Text-Book_of_Embryology_8#Fig083|Fig.83 in text]]
 
:'''Links:''' [[Book_-_Text-Book_of_Embryology_8#Fig083|Fig.83 in text]]

Revision as of 08:24, 13 April 2011

Fig. 83. Ventral and dorsal view of human embryo with 8 pairs of mesodermal somites

2.11 mm. CRL

(a) Ventral view, the yolk sac has been removed.

(b) dorsal view, the amnion has been removed, merely the cut edge showing.

Eternod. From models by Ziegler.

The changes that occur in the simple cylindrical body after the ventral body wall is closed comprise the differentiation of the head, neck and trunk regions and the development of the extremities as appendages of the trunk. Even in Eternod's embryo (Fig. 83) the region where the brain is developing is greater in diameter than the other part of the embryo. Thus the beginning of the head is indicated by an increase in size due primarily to the growth of the brain. The end of the head region is bent ventrally almost at a right angle to the long axis of the embryo, the bend occurring in the mid-brain and being known as the cephalic flexure. This is the first of the flexures that appear as development proceeds. On the cephalic side of the yolk sac attachment is a protrusion which indicates the position of the heart in what now may be called the cervical region or neck. Between the protrusion caused by the heart and the fore-brain there is~a depression which foreshadows the oral and nasal cavities and is now called the oral fossa.

Links: Fig.83 in text


Text-Book of Embryology: Germ cells | Maturation | Fertilization | Amphioxus | Frog | Chick | Mammalian | External body form | Connective tissues and skeletal | Vascular | Muscular | Alimentary tube and organs | Respiratory | Coelom, Diaphragm and Mesenteries | Urogenital | Integumentary | Nervous System | Special Sense | Foetal Membranes | Teratogenesis | Gallery of All Figures
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Pages where the terms "Historic" (textbooks, papers, people, recommendations) appear on this site, and sections within pages where this disclaimer appears, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms, interpretations and recommendations may not reflect our current scientific understanding.     (More? Embryology History | Historic Embryology Papers)

Reference

Bailey FR. and Miller AM. Text-Book of Embryology (1921) New York: William Wood and Co.



Cite this page: Hill, M.A. (2020, September 24) Embryology Bailey083.jpg. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/File:Bailey083.jpg

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