In humans, the yolk sac is the
site of origin for blood cells and primordial germ cells. The human yolk sac is
a membrane located outside the embryo and it is connected by a tube through the
umbilical opening to the embryo's midgut. The yolk sac serves as an early site
for the formation of blood and in time, is incorporated into the primitive gut
of the embryo.
<span>
are always unicellular
may have evolved from prokaryotes
</span><span>are more primitive than prokaryotes
</span>
Answer:
Columnar epithelial cells are elongated and column-shaped and have a height of at least four times their width. Their nuclei are elongated and are usually located near the base of the cells. Columnar epithelium forms the lining of the stomach and intestines
Explanation:
Epithelium - Wikipedia
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Keratinocytes are differentiated skin cells found in the outermost layer of the epidermis. Dendritic cells are antigen-presenting cells that play important roles in the adaptive immune response.
- In addition to keratinocytes, the <em>stratum spinosum</em> also contains another epidermal cell type called epidermal DENDRITIC cells that help to fight infection.
- The s<em>tratum spinosum</em><em> </em>is an epidermal skin layer between the <em>stratum granulosum </em>and<em> stratum basale</em>.
- Dendritic cells are antigen-presenting cells that are capable of processing harmful antigens in order to present them on the cell surface to the T cells of the immune system.
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Answer: Holds Genetic Information
Explanation: