Yolk Sacs and Yellow Marrow

Yolk sacs and yellow marrow. I can honestly say I have never put these two in the same sentence before, much less in a blog post. Here I am at the letter “Y” though and these two are rare companions on the short list of body components that start with this second-to-the-last letter of the alphabet. They aren’t body parts like our arms, legs, lungs, and xiphoid process are, but they each play vital roles in our amazing bodies.

With a little help from Google sources I would refer to as reputable, here is what a yolk sac is:

A yolk sac is a small pouch in the uterus made from thin membranes. The yolk sac is one of the first things to develop during pregnancy. It plays a very important role in early development, specifically during weeks 5 to 10 of a pregnancy, which are known as the embryonic stage. The yolk sac function includes: Circulating gasses between the baby and mother. Creating the first form of blood cells. Creating the cells that turn into other important structures. Providing the baby with nutrients. Providing the baby with metabolism and immune function.

After week 10, the yolk sac gets smaller and eventually disappears, as the placenta takes over these key functions.

It’s a little surreal to consider we were all once tiny embryos nourished by our very own, made-just-for-us yolk sac. Wow!

Then there’s the yellow marrow, unseen and not all that glamorous, but really incredible all the same.

Yellow bone marrow stores fat. These cells preserve fat for energy production and develop bone, cartilage, muscles and fat cells for your body. Yellow bone marrow is located in the hollow cavity of long bones. It is typically found at the center surrounded by red bone marrow.

So . . . we never see it, but yellow marrow tends to our needs for energy and helps keep the skeletal and muscular structure that hauls us around and holds us together healthy and operational. Pretty significant stuff! Wow!

Humble little yolk sac and yellow marrow help make us who we are. Amazing.