How do veins return blood to the heart? select all that apply?

1 answer:

6 0

A relatively small blood pressure gradient is generally insufficient to move blood through the veins under given conditions, thus venous return must be facilitated by valves within veins and two "pumps." ... As skeletal muscles contract, veins are squeezed to help propel the blood toward the heart.

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lora16 [44]

Answer:waves

Explanation:

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Darwin was spurred to finally publish his theory of natural selection by the writings of which scientist?. A.Lyall. B.Hutton. C.

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I believe is was C. Wallace

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What of the following is ordered from LARGEST to SMALLEST? Select one: a. virus, mitochondrion, hemoglobin, glucose, water molec

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Answer:

c. mitochondrion, virus, hemoglobin, glucose, water molecule

Explanation:

The mitochondrion is a membrane which is found in cytoplasm of eukaryotic cells. It is also known as power house of cells. This is largest from virus, hemoglobin, water molecule and glucose.

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Humoral immunity involves ________ cells and ___________

jarptica [38.1K]

Answer:

Humoral immunity involves B cells and recognize antigens or pathogens in the lymph or blood.

Explanation:

Humoral immunity is defined as the immunity which is mediated by several macromolecules presnet in the extracellular fluids such as antibodies, certain antimicrobial peptides, and complement proteins.

Humoral immunity allows to distinguishes two groups of foreign substances. it involves B cells and recognize antigens or pathogens in the lymph or blood.

Humoral immunity begins when an antigens bind to B cells. Interleukins or helper T cells provides a secondary signal to the B cells that activates a B cell and allows B cell proliferation. which roduces produce plasma cells. The plasma cell then produces antibodies which are identical to the specific antigen. The antibodies are the released and circulate through the body, binding to antigens. B cells the further produces memory cellss for future immunity.

So, Humoral immunity involves B cells and recognize antigens or pathogens in the lymph or blood.

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