EMBRYOLOGY

Embryologist is ==a scientist who studies embryology==

Prenatal development - the ==process of growth and development happening within the womb== in which a single cell zygote (the cell formed by the combination of a sperm and an egg) becomes an embryo, a fetus and then a baby.

THREE STAGES OF PRENATAL DEVELOPMENT

  • GERMINAL STAGE- approximately the first two weeks of development during which the primitive germ layers are formed
  • EMBRYONIC STAGE- the third through the eighth week; during which the major organ systems come into existence
  • FETAL PERIOD- From the ninth week until birth; the organ system grow and become more mature

Gametogenesis- is a ==series of changes that converts male and female sex cells into matured gametes==.

SPERMATOGENESIS- Gametogenesis in the male and produces spermatozoa.

OOGENESIS- Gametogenesis in the female and result in the formation of ova.

3 BARRIERS SPERM MUST PASS

  1. Jelly Coat
  2. Vitelline layer
  3. Plasma Membrane

Testes or seminiferous- where sperm production occurs

Spermatogonia (primitive germ cell)- are the initial pool of diploid cells that divide by mitosis to give two identical cells

  • A1 spermatogonia - will be used to replenish the pool of spermatogonia

This replenishment of spermatogonia means that males are fertile throughout their adult life.

  • Type B spermatogonium – will eventually form mature sperm.

  These cells are known as primary spermatocytes which then undergo meiosis.

  • Meiosis I -produces two haploid cells, known as secondary spermatocytes
  • Meiosis II -produces four haploid cells, known as spermatids

Four Major Events of Fertilization

  1. Sperm contacts the egg
  2. Sperm or its nucleus enters the egg
  3. Egg becomes activated and    developmental changes begin
  4. Sperm and egg nuclei fuse

Functions of Fertilization

Transmit- transmission of genes from both the parents to offsprings.

Restore- Restoration of the diploid number of chromosomes reduced during meiosis.

Development- Initiation of development in offspring.

BLASTOMERE- daughter cells produced by cleavage

morula- “little mulberry”

Blastula Stage -The ball of now tightly bound cells starts to secrete fluid and organize themselves around a fluid-filled cavity, the blastocoel.

inner cell mass or embryoblast - develops to become the embryo; and The cells that form the outer shell

outer cell mass or trophoblasts - cells will develop into the chorionic sac and the fetal portion of the placenta

Implantation - This process signals the end of the pre-embryonic stage of development

FERTILISED CELL DEVELOPMENT

OVULATION > OOCTYE> FERTILIZATION> ZYGOTE> FIRST SEGMENTATION> 4 CELL STAGE> 8 CELL STAGE> MORULA> BLASTOCYST> IMPLANTATION