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Chorionic villi development in Third Week Primary Secondary amp Tertiary Villi
>> YOUR LINK HERE: ___ http://youtube.com/watch?v=9YHPCvcoNFs
In this visual medical lecture, Dr. Aizaz from MedicoVisual talks about development of chorionic villi in third week. What are primary villi, secondary villi and tertiary villi. How these developmental changes paves the way towards formation of placenta. • 00:00 Intro • 01:00 What is the chorion • 01:45 Primary villi • 03:26 Secondary villi • 05:00 Tertiary villi • 07:14 Functions of chorionic villi and early placenta • 08:30 Anchoring villi or stem villi and Absorbing villi or free villi • 10:29 Review • The embryo has two balloon like fluid filled structures the amnion and yolk sac and whole this structure is floating inside the chorionic cavity. • The outer layer of chorionic cavity is also called chorion, consists of extraembryonic somatopleuric mesoderm on the inner side and cytotrophoblast on the outer side. The cytotrophoblast is further surrounded from outside by the syncytiotrophoblast. • Cytotrophoblast formed finger like projections into the syncytiotrophoblast, called primary villi. Primary villi were formed during second week of development. Embryo, embedded into uterus of its mother, is fully covered by these villi. • Now lets talk about happens to these villi during third week of development of the embryo. • Primary villi are solid finger like cords of cytotrophoblast penetrating into the syncytiotrophoblast. Some of these primary villi also branch out but they are still the solid cords of cytotrophoblast. They are called branched primary villi. • During the third week, as the extraembryonic somatopleuric mesoderm grow further. It extends its processes into the primary villi. Now the primary villi have an inner core made up of mesenchyme from the extraembryonic somatic mesoderm. At this stage, the villi are now termed as secondary villi. • In the next step, the inner mesenchymal core through vasculogenesis and angiogenesis form the vasculature inside the villus. Now we call it, tertiary villus. • With the ongoing development of chorionic villi, almost all of the tertiary villi are branched. Some of these branches are buried into the maternal endometrium. Such villi help in anchoring the conceptus into the maternal endometrium. These branches are anchoring branches or simply anchoring villi. While rest of the branches are free and called non-anchoring villi or free villi. • Between the villi, there are the lacunar spaces that are connected with maternal blood vessels. As they blood flow within this lacunar network. The free villus branches / non-anchoring villi take up the nutrients. The nutrients then flow into the vasculature of these villi. Since these free villi help in absorbing the nutrition from maternal tissue. They are also called absorbing villi. • We will discuss the dynamics of nutrients and gaseous exchange in later lectures of placenta and fetal circulation. But here we will have a brief overview. • The vasculature in the tertiary villi has an afferent arm that bring the less-oxygenated and nutrient deficient blood came from umbilical artery and the efferent arm, that take the blood after it becomes enriched with nutrients and oxygen, to the umbilical vein that take the blood ultimately to primordial heart of the embryo. Later on, as the chorion develops further and placenta develops, this system becomes much more robust and efficient by some changes into its structure that we will discuss later. • Website: https://www.medicovisual.com • Email: [email protected]
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