<span>As blood moves away from the heart toward the tissues, the relative size of blood vessels decreases, the blood pressure drops, and the velocity of blood flow slows.
The size of the arteries progressively decreases as they branch out from the major arteries of the body. Once the arteries are the size of the arterioles, the resistance to blood flow increases and velocity of blood flow slows then blood pressure drops.
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Answer: Gene Pool
Explanation:
Gene pool is the collection of all the gene and various allelic form of those gene within a population.
Variation naturally occurs among the gene of members of the same species that interbreed.
Gene pool It is therefore the total number of gene of all the members among the population of a particular species. Gene pool is used to determine the level of mutation, variation, genetic diversity among members of a population.
Answer:
Helper T cells are arguably the most important cells in adaptive immunity, as they are required for almost all adaptive immune responses. They not only help activate B cells to secrete antibodies and macrophages to destroy ingested microbes, but they also help activate cytotoxic T cells to kill infected target cells.
Explanation:
Helper T cells become activated when they are presented with peptide antigens by MHC class II molecules, which are expressed on the surface of antigen-presenting cells (APCs). Once activated, they divide rapidly and secrete cytokines that regulate or assist the immune response.
