Which one contains only mesodermal structures?
A. Liver, heart. blood and muscles
B. Notochord, heart. blood and bone
C. Liver. heart. blood and bone
D. Liver. blood. notochord and muscles

Hint The mesoderm is one of the three basic germ layers in the very early embryo of all bilaterian animals. Mesenchyme, mesothelium, non-epithelial blood cells, and coelomocytes are all formed in the mesoderm.

Complete step by step answer:
Intercellular signalling separates the mesoderm from the rest of the embryo, following which the mesoderm is polarised by an organising centre. The position of the organising centre is determined by the regions where GSK-3 protects beta-catenin from degradation. Other structures, such as the neural plate, which is the predecessor to the nervous system, can be induced by mesoderm.
One of the three germinal layers that develops in the third week of embryonic development is the mesoderm. Gastrulation is the process through which it is created. Signals for somite differentiation come from the notochord, neural tube, and epidermis, among other tissues. The intermediate mesoderm joins the paraxial and lateral plates, eventually forming urogenital organs such as the kidneys, gonads, and their accompanying ducts, as well as the adrenal glands.
After implantation, the blastocyst's inner cell mass divides into an outer ectoderm, middle mesoderm, and inner endoderm. The embryo's tissues and organs develop from these layers. Endoderm gives rise to the colon, stomach, intestines, liver, lungs, and pancreas, among other organs.
The heart, kidneys, gonads, genital ducts, cartilage, bones, muscles, blood cells, and other tissues are all made of mesoderm. The epithelium, brain, spinal cord, nerves, ears, nails, and hair are all made up of ectoderm. The mesoderm gives birth to the notochord.

As a result, B is the correct response.

Note: A process known as gastrulation forms a mesodermal layer between the endoderm and the ectoderm during the third week. The creation of a primitive streak on the epiblast's surface starts the process. The layers' cells migrate between the epiblast and hypoblast, spreading laterally and cranially.