INTRODUCTION

Serial Sections

The study of serial sections allows for the study of the microscopic anatomy of the embryo, in particular, the internal anatomy of the embryo. Many features that are not evident in the study of the whole embryo can be examined by viewing a sequence of sections of the embryo. Serial sections consist of the entire embryo sectioned in a certain plane. In the case of serial cross sections, the entire embryo was sectioned perpendicularly to the cranio-caudal axis from the beginning of the head to the end of the tail and all the sections were laid out in sequence on microscope slides. The embryo from which the accompanying photomicrographs were taken consisted of 336 sections. At a thickness of approximately 12 micrometers per section, the embryo was 4,800 micrometers or 4.8 millimeters in length.

Navigation within the Web Site

The screen consists of three frames, a photographic frame on the left, a text frame on the upper right, and an orientation frame on the lower right.

The photographic frame contains a photomicrographic image of a cross section of a 5-7 mm frog embryo taken from a set of 400 serial cross sections. The photographs are numbered one to 44 out of a possible 44. The cross sectional photographs are presented with the dorsal surface of the embryo uppermost and ventral surface lowermost. The lateral surfaces of the embryo are located on the right and left. A "Next Section" button below the photograph allows you to click and move to the following photograph. Clicking on the "Zoom" button will open a new window with the section at a higher magnification.

The larger frame on the right hand side of the screen is the text frame. This frame has a scroll bar on the right hand side of the frame that allows you to move text upward and downward. The text consists of descriptive paragraphs that begin with a title that gives the section number out of the total number of 400 sections that comprise the embryo. A listing of the major visible features occurring at this particular level of sectioning follows the section number. Clicking on the title will bring the corresponding photograph into the photographic frame.

The orientation frame is located on the lower right hand side of the screen. This frame contains a thumbnail size photograph of a side view of a whole 5-7 mm frog embryo with a vertical line that indicates the level of sectioning of each cross sectional photograph. A button list, allows you to click and move to the next section, a previous section, the ZOO*2100 (Developmental Biology) index, or the main (Cell and Developmental Biology) index page.

Note that the images are designed to display optimally with a screen resolution of 600 X 800 pixels. You may wish to adjust your video display. (Hint: Minimizing some of the navigation bars in your browser will also increase the size of your viewing screen and will also make the viewing of the serial section frames more convenient.)

Send comments to:
Sandra K. Ackerley (ackerley@uoguelph.ca),
Department of Zoology, University of Guelph, Guelph, Ontario, Canada N1G 2W1.

Page revised: May 30, 2000