The forming tissues of the endoderm, cortical and endodermal tissues all belong to .

Generally, the endoderm is separated from the ectoderm when the gastrula is formed. During the gastrulation phase, the endoderm constitutes all or part of the gastrulation wall. In amniotes, the endoderm appears in the embryo as the subblastic layer before the appearance of the notochord mesodermal canal or protobar.

In addition to the endoderm forming the main part of the digestive tract, vertebrates also differentiate into the liver, pancreas, thymus, thyroid, and other pharyngeal derivatives of the appendages of the digestive tract. Generally speaking, endoderm cells contain more yolk than other germ cells, so the cells are larger, especially in the terminal yellow total fissure, and the yolk concentration in the endoderm is significantly increased. In most cases, the endoderm is the cytoplasm that originates from the plant pole of the egg cell and its vicinity, with the exception of localized and superficial blasted eggs, and a subset of total loblasts of invertebrates.

The endoderm has phylogenically appeared in the most primitive form in coelenterates, and it can be regarded as the primitive germ like ectoderm (mesoderm can only be seen in metazoans above coelenterates). The results of the study of amphibians show that the formation of the endoderm is significantly later than that of the other two germ layers, and a considerable part of the organ primordium of endoderm differentiation is dependent on the mesoderm.

1. The ectoderm forms epidermis and nerve tissue.

The ectoderm is formed by animal pole cells. The epidermis and its appendages, nervous system and sensory organs developed from it.

The epidermis, the extension of the epidermis, such as the oral mucosa, nasal mucosa, etc., is developed from the ectoderm. ** Accessory structures refer to sweat glands, sebaceous glands and salivary glands. The nervous system includes the brain, spinal cord and the cranial nerves they emit, and the sensory organs mainly refer to the eyes, ears, etc.

2. The mesoderm forms bones, muscles, blood, lymph and other connective tissues in fibers.

The mesoderm is mainly formed by the extremely involution cells of animals.

The locomotor system composed of bones and muscles, the dermis, the entire circulatory system, the excretory system, the reproductive system and the outer membrane of the internal organs are developed from it.

The circulatory system includes the heart, blood vessels, and the blood that flows through the heart and blood vessels, and the bone marrow, the hematopoietic organ, is also developed from the mesoderm.

Lymphatic vessels and lymphatic organs are also developed from the mesoderm. The excretory system, including the kidneys, ureters, bladder, etc., is developed from the middle deficiency germ layer.

3. The endoderm forms the intestinal lumen epithelium and the digestive gland epithelium.

The endoderm is formed by plant polar cells.

The respiratory epithelium and the digestive tract epithelium and various digestive glands such as liver, pancreas, gastric glands, and intestinal glands developed from it.

The respiratory epithelium refers to the epithelium on the inner wall surface of the pharynx, larynx, bronchi, and bronchioles at all levels, and the alveolar epithelium also belongs to the respiratory epithelium. The epithelial of the digestive tract refers to the epithelium on the inner surface of the pharynx, esophagus, stomach, small intestine, and large intestine.

In general, the ectoderm forms epidermis and nervous tissue, the endoderm forms the intestinal luminal epithelium and digestive gland epithelium, and the mesoderm forms bones, muscles, blood, lymph, and other connective tissues. It can be simply written: "Internal exhalation of the liver and pancreas, external sensory nerves."

Everything else develops from the mesoderm.

Germ layer differentiation basically follows the above route. But there are exceptions: the sphincter of the iridescent eyeball does not come from the mesoderm, nor from the mesenchyme, but from part of the retina, that is, from the ectoderm.

The smooth muscle of the sweat glands does not come from the mesoderm, but from the ectoderm;Mesenchyme itself is ill-defined, and it can come from ectoderm, mesoderm, or even endoderm. In the case of regeneration, dedifferentiated cells may change the direction of differentiation, making it more difficult to distinguish which germ layer they belong to.

Hope you help. ^_

Both cortical and endodermal tissues belong to the sensitive and reclusive bridges ().

a.Surface organization.

b.Ground organization.

c.Internal organization.

d.Meetings with external organizations.

Correct answer: B