Answer to Question #53114 in Zoology for Aditya Dutta

Question

Hello Experts

Problem- What is IMPLANTATION AND GASTRULATION.{in context to embryonic development of humans} I am having difficulty in understanding the concept of it. PLEASE EXPLAIN THE TERMS IN greater depths and DETAIL.I shall be highly obliged

Answer 1

Implantation is a process of blastocyst attachment to the uterus endometrium. The initial phase of this process is called “adplantation” when blastocyst is loosely attached to the endometrium though it can roll to the site of attachment. Before this blastocyst using digesting enzyme (proteaze) to make a hole in zona pellucida and leave it. The attachment of blastocyst to uterine occurs through specific molecules of adhesion expressed on the surface of blastocyst and endometrium epithelial cells. For example, membrane protein trophinin mediates adhesion due to trophinin-trophinin interaction. This triggers next step of the implantation – proliferation and invasion of trophectoderm cells. At the same time apoptosis in the endometrial epithelial cells is induced that ease the penetration of the blastocysts. Another protein that provide adhesion is galectin 9 that binds galactosides of the extracellular matrix in the uterus. Cytokines (signal molecules also play an important role in implantation because they regulate the direction and the speed of this process. The main purpose of the implantation is to form placenta.
Gastrulation is a process of embryonic development when three primary germ layers (endoderm, mesoderm and ectoderm) are formed. During gastrulation spherical blastula transforms into structure with cavity and three layers of cells. This process requires special cell movements: invagination (cell layer is bending), ingression (only individual cell move), involution (rolling of cell layer), epiboly (thinning of cells), intercalation (one cells penetrate into another cell layer). Gastrulation of different animals require several types of cells movements. After three germ layers are placed in space all types of tissues can be formed.