Cleavage in Animal Development: Definition, Patterns & Regulation Video

An error occurred trying to load this video.

Try refreshing the page, or contact customer support.

Coming up next: Gastrulation and the 3 Germ Layers (Ectoderm, Endoderm & Mesoderm)

You're on a roll. Keep up the good work!

Take Quiz Watch Next Lesson
Your next lesson will play in 10 seconds
  • 0:01 Embryonic Development
  • 0:47 Major Events During Cleavage
  • 2:10 Patterns of Cleavage
  • 3:30 Lesson Summary
Save Save Save

Want to watch this again later?

Log in or sign up to add this lesson to a Custom Course.

Log in or Sign up

Speed Speed

Recommended Lessons and Courses for You

Lesson Transcript
Instructor: Sarah Friedl

Sarah has two Master's, one in Zoology and one in GIS, a Bachelor's in Biology, and has taught college level Physical Science and Biology.

Did you know that you were once just a tiny, single cell? But look at you now - a full grown multicellular being! You can thank cleavage for that, which you'll learn about in this video lesson.

Embryonic Development

You've come a long way from when you were just a zygote. You probably don't remember this stage of your life because you were only a newly fertilized egg in the first stage of being a unique individual. But think about how much has happened to you since then - you developed and grew, you were born, and now here you are, learning about it all!

As a human you are made up of many trillions of cells, but you weren't always this way. The first major stage of development a zygote goes through to help you reach this great cellular height is called cleavage. This is the rapid cell division that leads to a multicellular embryo (to cleave something is to split or slice it). And, this is such an important stage that we've devoted an entire lesson to it! Ready to get started?

Major Events During Cleavage

There are some really important things that happen during cleavage, as well as some processes that are essentially put on hold. The cell is dividing incredibly fast during cleavage, which means that the processes that go along with cell division, such as DNA synthesis, mitosis, and cytokinesis, also occur at rapid-fire speed. But during this time, very few new proteins are made. The embryo also doesn't do much growing in terms of size during cleavage - it stays the same size as the zygote! What happens is that, as the cells continue to divide, they divide into smaller and smaller cells instead of just building up into a larger embryo.

This makes sense if you think about it. If you cut an apple in half, you have divided the apple into two equal segments. Divide each of those two pieces in half and you now have four. But you don't have four larger pieces, just four pieces that add up to the same size as the original apple.

In an embryo, this process continues on and on, with each new cell dividing into smaller cells until a hollow cell ball called a blastula is formed. And inside this ball is a fluid-filled cavity called the blastocoel. Unlike our apple, though (which is now just many equal-sized pieces of one apple), each new cell that is formed from division has its own nucleus and is its own independent cell.

Patterns of Cleavage

Just like animals come in all shapes and sizes, so does the cleavage that creates them. There are two main patterns of cleavage to be familiar with: complete and incomplete. Complete cleavage is also called holoblastic cleavage, and incomplete cleavage is called meroblastic cleavage.

To unlock this lesson you must be a Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use

Become a member and start learning now.
Become a Member  Back
What teachers are saying about
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create an account