Fertilization, Cleavage & Implantation

The process of sperm and ovum joining to form a zygote.

The ampullary part of the uterine tube (lateral third).

Inherited only from the mother.

Mitochondria in the middle piece provide energy, and the tail (flagellum) propels it.

A conditioning period of sperm in female tract (7 hours in humans).

Contains enzymes that help sperm penetrate the egg.

Contains DNA and acrosome (enzymes needed to penetrate egg).

The egg cell immediately after ovulation.

The process where the blastocyst embeds into the uterine lining.

Happens approximately 12-24 hours after ovulation.

Embryo stage approximately 30 hours after fertilization.

Embryo with 12-16 cells, approximately 3 days old.

Embryo stage (about 4.5 days old) with fluid-filled cavity; zona pellucida disappears.

Implantation begins around the 6th day, and is complete around 11 days after fertilization.

Typically in the anterior or posterior uterine wall.

The modified uterine lining after implantation.

The process where the neural folds fuse together to form the neural tube, which eventually develops into the central nervous system.

Cells derived from the neuroectoderm that form between the neural tube and the surface ectoderm. They contribute to a variety of structures like nerves, pigment cells, and bones of the face.

The period of embryonic development when the major organs and organ systems are formed. This crucial period occurs during the third to eighth week of gestation.

Birth defects that occur when the neural tube fails to close properly during embryonic development. Examples include anencephaly (absent brain) and spina bifida (open spinal cord).

The portion of the chorion that continues to grow and expand during pregnancy. It forms the fetal part of the placenta.

The process where the cranial part of the embryo folds ventrally, integrating part of the yolk sac into the foregut.

The cranial part of the endodermal yolk sac incorporated during head folding, forming the future digestive tract.

The process where the caudal part of the embryo folds ventrally, incorporating part of the yolk sac into the hindgut.

The caudal part of the endodermal yolk sac incorporated during tail folding, forming the future digestive tract.

The terminal part of the hindgut, which will eventually differentiate into the urinary bladder and rectum.

The process where the lateral sides of the embryo fold medially, creating a cylindrical shape and integrating the midgut.

The middle part of the endodermal yolk sac incorporated during lateral folding, forming the central part of the digestive tract.

The constricted communication between the extraembryonic coelom and the midgut, formed during lateral folding.

The fluid-filled cavity that surrounds the embryo, expanding during lateral folding at the expense of the extraembryonic coelom.

Folding gives the embryo its cylindrical shape, establishes the gut tube, and creates the amniotic cavity.

A condition where the placenta implants low in the uterus, near the cervix, instead of the upper part.

The process where the blastocyst, an early embryo, burrows into the lining of the uterus.

The outer layer of the blastocyst, the trophoblast, develops into two layers: the cytotrophoblast and the syncytiotrophoblast.

This inner layer of the trophoblast actively divides and grows, contributing to the formation of the placenta.

This outer layer of the trophoblast invades and breaks down maternal tissue, paving the way for the placenta.

Empty spaces (lacunae) appear in the syncytiotrophoblast, setting the stage for blood flow between mother and fetus.

The beginning of blood flow between the mother and the developing fetus, established by the end of the second week.

Cellular columns (primary villi) extend from the cytotrophoblast and are surrounded by the syncytiotrophoblast.

The inner cell mass, or embryoblast, splits into two layers: the epiblast and the hypoblast, forming a bilaminar disc.

Cells from the epiblast layer that line the amniotic cavity, creating a protective sac for the developing embryo.

The part of the endometrium directly beneath the implanted blastocyst, forming the maternal side of the placenta.

The part of the endometrium covering the implanted blastocyst, separating it from the uterine cavity.

The remaining part of the endometrium lining the uterine cavity, not directly involved with the implantation.

Implantation of the blastocyst outside the normal uterine wall, often leading to complications like miscarriage or internal bleeding.

The trophoblast differentiates into two layers: the cytotrophoblast (inner, actively dividing layer) and the syncytiotrophoblast (outer, invasive layer). This sets the stage for the formation of the placenta.

The syncytiotrophoblast invades and breaks down the maternal tissues, creating spaces (lacunae) that will eventually be filled with maternal blood. This is essential for the exchange of nutrients and waste between mother and fetus.

Cellular columns called primary villi extend from the cytotrophoblast and are surrounded by the syncytiotrophoblast. These structures will eventually develop into the chorionic villi, which are essential for placental function.

The embryoblast is the inner cell mass of the blastocyst. It differentiates into the epiblast and hypoblast, forming the bilaminar disc that will eventually develop into the embryo.

The three-layered embryonic disc formed during gastrulation, consisting of the ectoderm, mesoderm, and endoderm.

The process where the bilaminar embryonic disc transforms into a trilaminar germ disc through cell migration and differentiation.

A midline groove on the surface of the epiblast, acting as a pathway for cell migration during gastrulation.

A rod-like structure that forms the axis of the embryo, providing structural support and signaling for nervous system development.

The three primary layers of cells in the embryo: ectoderm, mesoderm, and endoderm, each giving rise to distinct organs and tissues.

Villi that extend from the chorionic plate to the decidua basalis, anchoring the placenta to the uterine wall.

Villi that branch out from the sides of anchoring villi, facilitating the exchange of nutrients, oxygen, and waste between mother and fetus.

A fluid-filled cavity that surrounds the embryo, providing a protective and buoyant environment for its growth.

Clear watery fluid within the amniotic cavity, primarily composed of maternal blood and fetal urine.