1 / 21

Embryological Stages

This document outlines key embryological stages following fertilization in the female reproductive system. It begins with the release of the egg, its journey through the fallopian tube, and the fusion of sperm and egg nuclei resulting in a zygote. The text details subsequent cleavage stages—2-cell, 4-cell, and 8-cell stages—highlighting differences between protostomes and deuterostomes. Further stages include the morula formation and development of the blastula, followed by the gastrula stage where germ layers are established: ectoderm, mesoderm, and endoderm, crucial for organ formation.

latif
Télécharger la présentation

Embryological Stages

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Embryological Stages March 23, 2011

  2. Female Reproductive System

  3. Fertilization: 0 hours • Egg is released from the ovary & moves into the fallopian tube to wait for the arrival of the sperm • Fertilization- results in a zygote • requires the sperm & egg nucleus to fuse • Following fusion, egg plasma membrane undergoes changes that prevent entrance of other sperm • Then wave-like action of cilia move the fertilized egg toward the uterus for implantation to take place

  4. Fertilization of female egg

  5. Location

  6. Cleavage 2-cell: 24 hours • Cleavage: process by which a zygote divides by mitosis to form two new cells • mitosis and DNA replication occur repeatedly • Cell is no longer just one cell

  7. Location

  8. 4-Cell: 36 hours • Cleavage continues as two cells will divide to form 4 cells, and so on • Continue dividing until form a blastocyst

  9. Location

  10. 8-Cell: 48 hours 8-CELL STAGE IS KEY DIFFERENCE!!! • Either Protostomes or Deuterostomes depending on species • Protostomes (clams, worms, & insects) undergo spiral cleavage- cells divide and they do not sit on top of each other; they appear to spiral

  11. Deuterostomes • Deuterostomes- (starfish & vertebrates) cleavage results in 8 cells sitting directly on top of each other. This is called radial cleavage

  12. Location

  13. Morula 16-Cell: 60-84 hours • The eight cells now continue to divide until you are simply a large solid ball of cells (16-32 cells). Morula

  14. Location

  15. Blastula: 6 days • At this time, the morula begins to form a hollow ball of cells called the blastula. • The blastula contains a fluid filled space known as the blastocoel. BLASTOCOEL BLASTULA

  16. Location

  17. Gastrula: ~15 days • Blastula begins to fold inward on one side • When the folding occurs, it creates a horse shoe shaped structure that is 2 cell layers thick • Outer layer of the ball is called the ectoderm. • Inner layer of the ball is called the endoderm. • Eventually, another cell layer will begin to form between the endoderm and ectoderm. This layer is called the mesoderm. Mesoderm

  18. 3 Tissue Layers In Depth • Ectoderm- forms nervous system & outer layer of skin • Mesoderm- forms muscle, bone, & cardiovascular system • Endoderm- organs of digestive system, lining of respiratory system & bladder

  19. Gastrula (cont.) • The point where the horse shoe almost touches is called the blastopore (small hole) • In protostomes this will eventually form the mouth. • In deuterostomes this will form the anus Mesoderm

  20. Location

More Related