Embryogeny: Definition, Meaning, Diagram, Plants

Definition Of Embryogeny

Embryogeny is the process in which the zygote—an already fertilized egg—develops into a completely formed embryo. Being such a complex process, it involves multi-staged cell divisions, differentiation, and morphogenesis, finally forming an onset of different tissues and organs of the organism.

Major, general stages of embryogenesis present themselves with the following: fertilization, zygote formation, blastula stage, gastrula stage, and organogenesis. To single out each process at every stage, one can mention certain cellular processes and structural changes that give rise to the developing embryo.

Stages Of Embryogenesis

Embryogenesis involves a series of coordinated stages wherein a single-celled zygote transforms into a multicellular embryo.

Fertilization

• A process where a sperm and an egg combine to form a zygote.

• A sperm cell penetrates an egg (ovum) cell, and the egg then becomes activated and its genetic material combines with that of the sperm.

Zygote Formation

The single cell is formed from the combination of the sperm cell and the egg cell during fertilization.

First Cell Division (Cleavage)

• Rapid, mitotic cell division of the zygote, without intervening cell growth.

• Formation of a multicellular structure called morula.

Stage Of Blastula

This is the process of the development of a hollow sphere composed of cells.

Formation Of Blastula

A fluid-filled cavity formed inside a spherical layer of cells: blastocoel.

Formation Of Blastocoel

The central cavity is formed within the blastula.

Gastrula Stage

• It is a process that rearranges the blastula into a three-layered formation called gastrula.

• The cell movement leads to the development of the primary germ layers.

Formation Of The Germ Layers

• Ectoderm: The outer layer of skin and the nervous system.

• Mesoderm: It forms the middle layer, such as muscles and bones.

• Endoderm: it forms the inner layer, like the digestive tract and organs.

Organogenesis

• The process through which germ layers develop into the organs and tissues of the organism.

Differentiation In Various Organs

• Cells from germ layers become specific to form particular organs, such as the heart, lungs, and brain.

Examples Of Organ Formation

• Formation of heart from mesodermal cells

• Formation of Brain from ectodermal cells.

Duration And Stages Of Pregnancy

Pregnancy is the most critical period in human development, normally ranging to about 40 weeks from the first day of the last menstrual period to childbirth. It is divided into three trimesters that have quite significant developmental milestones.

First Trimester: Weeks 1-12

The developments in this period are given below:

Conception And Implantation

• Fertilization ensues, resulting in a zygote.

• The zygote divides and is implanted in the uterine wall.

Embryo Development

• Major organs and structures start to form.

• Heartbeat is detectable by the end of week 6.

Second Trimester (Weeks 13-26)

The developments in this period are given below:

Fetal Development

• Rapid growth and development of body systems.

• Movement of the fetus (quickening) felt by the mother.

Features

• Formation of skeletal structure and facial features.

• Development of sensory organs; The fetus can hear and respond to stimuli.

Third Trimester (Weeks 27-40)

The developments in this period are given below:

Final Growth And Maturation

• Rapid weight gain and maturation of lungs and other vital organs.

• Positioning of the fetus for birth (head down).

Preparation For Birth

• Braxton Hicks's contractions can be felt.

• More frequent prenatal visits will be booked to make sure the baby is healthy.

Key Milestones In Pregnancy

• Week 4: Implantation complete

• Week 8: All major organs start to develop

• Week 12: The chance of miscarriage greatly decreases

• Week 20: Ultrasound can detect the sex of the baby

• Week 24: Baby has a survival chance outside the womb if a medical intervention is made

• Week 37-40: Fully developed pregnancy; the baby is ready to come out of the mother's body.

Embryogeny In Plants

Plant embryogeny consists of stages and processes particular for both monocots and dicots.

Monocot Embryogeny

• One cotyledon, or seed leaf is present.

• The endosperm remains and is used as a food source.

• The zygote divides and differentiates.

• Scutellum and coleoptile are established.

Dicot Embryogeny

• Two cotyledons, or seed leaves are usually present.

• The endosperm is usually degraded by the cotyledons.

• The zygote divides and differentiates.

• Hypocotyl, radicle and cotyledons are established.

Factors Affecting Embryogeny

Embryogenesis is subject to control by genetic, environmental, and hormonal factors.

Genetic Factors

• Developmental processes are controlled by inherited genetic information.

• Furthermore, mutations can affect embryonic development.

Environmental Factors

• Extrinsic factors like temperature, nutrition, and toxins affect development.

Hormonal Influence

• Hormones regulate the proliferative and differentiation processes in embryogenesis.

Common Anomalies Of Embryogenesis

A variety of factors may truncate or abort the process of embryogenesis.

Causes Of Developmental Defects

• Gene mutations, environmental stress, nutritional deficits.

Examples of Common Anomalies

• Neural tube defects, Congenital heart defects, Limb malformation.

Importance Of Studying Embryogeny

The study of embryogeny has significant medical and agricultural implications.

Medical Significance

• Understanding the mechanisms of birth defects.

• Advances in regenerative medicine and stem cell therapy.

Agricultural Applications

• Helps in developing self-incompatible plants with desired traits.

• Enhancement of plant breeding

• Improved yield of crops with disease resistance.

Recommended Video On 'Embryogeny'