Class 12 Biology (India)
Course: Class 12 Biology (India) > Unit 3Lesson 6: Fertilisation, Pregnancy and Embryonic Development
Germ layer derivatives
Created by Jeff Otjen.
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- At1:10, it is mentioned that the bladder is derived from the mesoderm. However, I have read in other textbooks that while the kidneys are derived from the mesoderm, the bladder is in fact derived from the endoderm. A clarification would be greatly appreciated.(61 votes)
- You're right, but the bladder has two parts. 2/3 of it is made by endoderm. 1/3 of it is made by mesoderm, and is called trigone. The trigone, unlike the rest of the bladder does not stretch. The urinary ducts (all 3) are attached to this part of the bladder. This rigid quality of trigone helps to ensure that the urinary ducts are not blocked as a result of stretching.
"Embryologically, the trigone of the bladder is derived from the caudal end of mesonephric ducts, which is of mesodermal origin (the rest of the bladder is endodermal)".(21 votes)
- It is worth noting that the nasal, oral, and anal epithelium are produced from the ectoderm, not the endoderm with the rest of the GI tract.(22 votes)
- Great note, although you don't have to know this specific fact for the MCAT.(0 votes)
- To answer all of the questions on more in detail (which I also agreed), I personally liked these two sources; this should be all we need for the MCAT:
- is the urinary bladder in the mesoderm?? Are you sure?(2 votes)
- is there a video where it explains the heart's embryology?(4 votes)
- I thought mesoderm responsible for hair(1 vote)
- Is there a video that explains it more in detail?(3 votes)
- What is a coelom? Can i say it to be the space that lies between the body wall i.e skin and the the alimentary canal,?In other words can i say it to be the space in which heart, lungs or bones are located?(2 votes)
- A coelom is a fluid-filled cavity that is completely surrounded by mesoderm (compare to pseudocoeloms or acoelomates). The abdominal and thoracic cavities that hold visceral (internal) organs are divisions of a coelom in very broad terms. Because they have other divisions within them, though, they tend to have more specific names that are commonly used.(3 votes)
- There is a key part that is from ectoderm you are not mention!(1 vote)
- what about eyes?(1 vote)
- The eye is derived from the neuroepithelium, surface ectoderm, and the extracellular mesenchyme which consists of both the neural crest and mesoderm. Therefore it is basically from the Ectoderm and Mesoderm .(1 vote)
- Now if you'll remember from near the end of early embryogenesis, you've gone through the process of gastrulation, and you've formed your three primary germ layers, and those germ layers were the endoderm, the mesoderm, and the ectoderm. And the cells in these germ layers go on to form very specific structures. Endodermal cells are primarily responsible for forming the gastrointestinal tract. So, I'll draw the gastrointestinal tract as a tube here, at least to start out with, and we have holes at one end and at the other. So, the lungs actually develop from the upper gastrointestinal tract, and, of course, the liver as well. And up here in the abdomen as well we have the pancreas, and then, of course, that tube goes on to form the esophagus, the stomach, the small intestines, and the large intestines. Mesoderm tissues, I'll draw here in purple, form some of the layers of the skin, some of the inner layers. They also form muscles and bones, and that includes the cardiac muscle as well. And then tucked away down here in the abdomen and pelvis we have the kidneys and the bladder and our ovaries or testes. And moving on to the ectoderm, as you might suspect, the ectoderm forms the outer layer of skin, and it also forms some skin-related items like sweat glands and hair, but interestingly, in addition to skin and hair and glands, the ectoderm also forms our nervous system. So, just a recap. The endoderm forms our gastrointestinal and pulmonary systems, including the lungs, gastrointestinal tract, liver, pancreas, et cetera. The mesoderm forms our muscles, including the heart muscle, our skeletal system, and our genitourinary tracts. And the ectoderm forms our skin and related structures, along with our nervous system.