This paper studies.

height

Histogenesis and Changes of Embryonic Lung of Mongolian Sheep in 1970s

the seamy side

Laryngeal air groove appears, with longitudinal slit-like opening, forming laryngotrachea.

embryonic development

By the time of 10mm, the tracheal bud had produced two tubular bubbles.

branch

Then it develops into the left and right main bronchi. The embryonic lung is 85mm long, and the whole lung tissue is composed of compact tracheal buds with smaller diameter, which is the pseudoglandular stage of embryonic lung development. Since the embryo was 85 mm long, some large bronchi have appeared in fetal lung tissue.

besides

There are obvious cartilage slices in the membrane, and mixed glands have been formed in the submucosa. At this time, the tissue development of embryonic lung began to enter the tubule stage; Terminal bullous stage refers to the development stage from 250mm fetus to 347mm fetus with long lungs, that is, the primitive alveolar stage. At this stage, capillaries proliferate rapidly, while primitive alveoli differentiate. The lung structure of embryos from 400mm( 130 days) to before birth is obviously different from that of the final bubble stage, and basically similar to that of adults, which is called "prenatal period". 300 mm embryonic lung can be seen under electron microscope.

attend a class

Type ⅰ and type ⅱ alveoli

cell

Appear. Type ⅰ alveolar cells are spindle-shaped, with irregular nuclei and inconspicuous nucleoli. Less cytoplasm. Type ⅱ alveolar cells are cubic with abundant cytoplasm and obvious nucleoli.

cell organ

More,

mitochondria

Rich.

rough endoplasmic reticulum

Developed, but no secretory granules.

After 400mm body length, two typical types of alveolar cells have appeared in the lungs of embryos, namely type ⅰ and type ⅱ alveolar cells. Some type ⅱ alveolar cells have typical endocrine granules.

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essay

Yes