Sunday, 28 April 2019

Yolk-sac : Parts of the body

                                              A to Z 2019

The yolk sac is situated on the ventral aspect of the embryo. It is filled with fluid, the 

vitelline fluid, which possibly may be utilized for the nourishment of the embryo during 

the earlier stages of its existence. Blood is conveyed to the wall of the sac by the 

primitive aortae , and after circulating through a wide-meshed capillary plexus, is 

returned by the vitelline veins to the tubular heart of the embryo. This constitutes the 

vitelline circulation, and by means of its nutritive material is absorbed from the yolk-sac 

and conveyed to the embryo. After the end of the fourth week the yolk-sac presents the 

appearance of a small pear-shaped vesicle  (umbilical vesicle) opening into the digestive 

tube by a long narrow tube, the vitelline duct.


The yolk-sac is also responsible for the initial circulation and is in charge of delivering 

nutrients, via a primitive aorta, to the developing embryo. The yolk-sac provides 

nutrition to the developing embryo until the placenta takes over. 

                                        How does the yolk-sac disappear?

As the pregnancy advances, the yolk-sac progressively increases from the 5th to end of 

the 10th gestational week, following which the yolk sac gradually disappears and is often 

sonographically undetectable after 14-20 weeks.

                     Readers, did you know about yolk-sac earlier?

                   I am participating in the A to Z Challenge. 

Information courtesy Google

Day 3.Chin & Cheeks                 Day 4. Dimples 
Day 5. Eye                                        Day 6. Feet
Day 7 . Gums/Gingiva                       Day 8. Hair 
Day 9. Intestine                                Day 10. Jaws                                   

Day 11. Kidneys                                Day 12. Lungs

Day 13. Mouth                                  Day 14. Nails 

Day 15. Ovary                                      Day 16. Pituitary-gland

Day 17.  Quadriceps                             Day 18.  Ribs                        

Day 19. Spleen                                  Day 20. Trachea

Day 21. Uterus                                  Day 22. Vertebral Column

Day 23.  Waist                                   Day 24. Xiphoid-process 



  2. Replies
    1. the topic becomes interesting after we read and know about it. Thanks A Tarkabarka H.

  3. I have not read anything like this before - thanks for sharing this information.

  4. Another informative and interesting post, Kalpana. Didnt know all this about Yolk Sac!

    1. Yes shilpa, this is an interesting post. Thanks for reading and appreciating.

  5. How interesting, Kalpana! I remember this from college (majored in Zoology).

    1. Zoology is an interesting subject. Thanks Vidya for reading and commenting.

  6. Like much I've read here of late, this as completely new to me!

    My story - 'This way that way!'

  7. Great post, very interesting. Thanks about the yolk-sac, I didn't knew!

  8. I knew about it but not in detail.Thanks for the insights


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