Embryology

Introduction

Embryology is the branch of biology that studies the prenatal development of gametes (sex cells), fertilization, and development of embryos and fetuses. Additionally, embryology encompasses the study of congenital disorders that occur before birth, known as teratology.

Gametogenesis

Gametogenesis is the process by which gametes are produced. This process involves the division of germ cells into haploid gametes, a process known as meiosis. There are two types of gametogenesis: spermatogenesis (formation of sperm) and oogenesis (formation of eggs).

Fertilization

Fertilization is the fusion of two gametes to initiate the development of a new individual organism. This process involves the joining of the sperm and egg, followed by the fusion of their nuclei.

Embryonic Development

Embryonic development refers to the process by which the embryo forms and develops. It begins with the cleavage of the fertilized egg, followed by gastrulation, a process that forms the germ layers, and organogenesis, where organs develop.

Cleavage

Cleavage is the division of cells in the early embryo. The zygotes of many species undergo rapid cell cycles with no significant growth, producing a cluster of cells the same size as the original zygote.

Gastrulation

Gastrulation is a phase of embryonic development that leads to the formation of three layers: the ectoderm, endoderm, and mesoderm. These layers give rise to all the tissues and organs of the animal body.

Organogenesis

Organogenesis is the process by which the ectoderm, endoderm, and mesoderm develop into the internal organs of the organism.

Fetal Development

Fetal development refers to the stages that follow embryogenesis. During this period, the major structures and organ systems have formed and the fetus continues to grow and mature.

Congenital Disorders

Congenital disorders, also known as birth defects, are structural or functional anomalies that occur during intrauterine life and can be identified prenatally, at birth, or sometimes may only be detected later in infancy.

Teratology

Teratology is the study of abnormalities of physiological development. It is often thought of as the study of human congenital abnormalities, but it is broader than that, taking into account other non-birth developmental stages, including puberty; and other organisms, including plants.