IB Biology Topic D3.1.16 Development of a Blastocyst and Implantation in the Endometrium Revision Notes (HL)

IB Biology Topic D3.1.16 Development of a Blastocyst and Implantation in the Endometrium Revision Notes (HL) | RevisionDojo

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A Blastocyst Forms From the Zygote and Implants in the Endometrium Around Day 7

After fertilisation, the zygote divides repeatedly to form a blastocyst.
The blastocyst then implants in the endometrium, the lining of the uterus.

Analogy

Think of the zygote as a seed.
Like a seed, it needs to settle into rich soil, here the endometrium, before it can draw nutrients and grow.

Cleavage Turns the Zygote Into a Hollow Blastocyst by Day 5 to 6

Cleavage divisions
1. The zygote undergoes mitotic divisions called cleavage.
2. These divisions raise the cell number without increasing the overall size of the embryo.
3. A solid ball of cells called the morula forms first.
Blastocyst formation
1. By day 5 to 6, a fluid-filled cavity called the blastocoel opens up, and the embryo becomes a blastocyst.
2. Trophoblast: the outer layer of cells that will form the placenta.
3. Inner cell mass: a cluster of cells inside the blastocyst that will develop into the embryo.
4. The blastocyst is still surrounded by the zona pellucida, a protective glycoprotein layer.

Note

The zona pellucida stops the blastocyst implanting early in the oviduct, which could cause an ectopic pregnancy.

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IB Biology Topic D3.1.16: Development of a Blastocyst and Implantation in the Endometrium Notes

A Blastocyst Forms From the Zygote and Implants in the Endometrium Around Day 7

Cleavage Turns the Zygote Into a Hollow Blastocyst by Day 5 to 6

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

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A Blastocyst Forms From the Zygote and Implants in the Endometrium Around Day 7

Cleavage Turns the Zygote Into a Hollow Blastocyst by Day 5 to 6

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A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

IB Biology Topic D3.1.16: Development of a Blastocyst and Implantation in the Endometrium Notes

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

A Blastocyst Forms From the Zygote and Implants in the Endometrium Around Day 7

Cleavage Turns the Zygote Into a Hollow Blastocyst by Day 5 to 6

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account

A Blastocyst Forms From the Zygote and Implants in the Endometrium Around Day 7

Cleavage Turns the Zygote Into a Hollow Blastocyst by Day 5 to 6

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account