The endoderm, the innermost embryonic layer, becomes the digestive organs and other accessory organs such as the liver and pancreas. The ectoderm becomes the epidermis and nervous system. The mesoderm becomes muscles, bones, cartilage, blood, and reproductive organs.
Unlike the rest of the abdominal organs which are derived from endoderm, the spleen is mesodermal in origin.
Endoderm
The endoderm.
Diploblastic is generally referred to as "having a body derived from only two embryonic cell layers (ectoderm and endoderm, but no mesoderm), as in sponges and coelenterates".
From inner to outer, the germ cell layers are the endoderm, mesoderm, and ectoderm. Each of the three layers develops into a different part of the embryo: the endoderm into the respiratory, auditory, and digestive system; the mesoderm into the skeleton and muscles; and the ectoderm into the skin, tooth enamel, and nervous system.
endoderm
Prussian embryologist Robert Remak coined the term "endoderm" in 1835. The endoderm is the innermost of the three primary germ layers of an embryo. The endoderm may also be called the hypoblast.
Organelles
Oral mucosa is very tough to tolerate all sort of insults or misuses done to it. That is why it is derived from the skin or ectoderm. Mucosa from the gastrointestinal tract is derived from the endoderm.
no
The endoderm of the gastrula turns into internal organs such as the liver and pancreas, and into the lining of some systems.
Actually ur question is itself not correct so the 'WHY" part cannot be answered. Epithelial tissue is a lining tissue which can be present in any organ.the mesoderm gives rise to organs like-muscles / bones / connective tissue / blood and lymph vessels / kidney / gonads and the cortex of suprarenal glands. ectoderm-nervous system epidermis and so on and endodermto GIT liver lungs pancreas and GIT so for example if u consider the epithelial tissue of lungs----its derived from endodermas lung as a whole is derived from endoderm.