lesson 2: Fertilization and Early Embryonic Development

Development

Changes from organism's beginnings to maturity.

Germ Cells

Haploid cells uniting to form diploid cells.

Haploid

Cells with one set of chromosomes.

Diploid

Cells with two sets of chromosomes.

Oogenesis

Process of maturation of female gametes.

Follicular Cell Proliferation

Increase in follicular cells during oogenesis.

Zona Pellucida

Glycoprotein layer surrounding oocyte.

Thecal Layer

Cell layer surrounding the follicle.

Antrum Folliculi

Fluid-filled cavity in a mature follicle.

Secondary Oocyte

Oocyte released during ovulation.

Corona Radiata

Layer of cells surrounding the oocyte.

Perivitelline Membrane

Membrane surrounding the oocyte.

Spermatozoa

Mature male gametes.

Spermiogenesis

Transformation of spermatids into spermatozoa.

Oligospermia

Low sperm count below 20 million/ml.

Azoospermia

Absence of sperm in semen.

Fertilization

Union of male and female gametes.

Internal Fertilization

Sperm fertilizes egg inside the body.

External Fertilization

Sperm fertilizes eggs outside the body.

Acrosome Reaction

Sperm enzymes help penetrate zona pellucida.

Cortical Reaction

Egg response blocking additional sperm entry.

Zygote

Fertilized egg, first stage of development.

Cleavage

Rapid mitotic divisions of the zygote.

Morula

Solid ball of cells post-cleavage.

Blastula

Hollow ball of cells surrounding blastocoel.

Gastrulation

Formation of three germ layers from blastula.

Ectoderm

Outer layer forming skin and nervous tissue.

Endoderm

Inner layer forming digestive tract lining.

Mesoderm

Middle layer forming muscles and circulatory system.

Blastopore

First opening in the embryo during gastrulation.

Primitive Gut

Initial gut structure formed during gastrulation.

Notochord

Structure forming backbone in developing embryo.

Neural Tube

Structure developing into the central nervous system.

Somites

Blocks of mesoderm forming vertebrae and muscles.

Coelom

Body cavity formed during embryonic development.

Cell Differentiation

Unspecialized cells become specialized tissues.

Cell Growth

Increase in cell number and size.

Apoptosis

Programmed cell death for development.

DNA

Hereditary material controlling cellular activity.

Cytoplasm

Receives instructions from nuclear DNA.

Fertilization in Sea Urchin

Multiple sperm bind, one fertilizes egg.

Fertilization Steps

Acrosome reaction, zona reaction, pronuclei formation.

Embryonic Development Stages

Cleavage, compaction, blastocyst formation, implantation.

Embryonic Tissues

Ectoderm, mesoderm, endoderm differentiate into organs.

Gastrulation in Frog

More complex due to yolk presence.

Gastrulation in Chick

Embryo sits atop yolk mass.

Gastrulation in Mammals

Blastula called blastocyst; forms placenta.

Control of Development

Nucleus and cytoplasm coordinate cellular functions.