mass flow

Mass flow:

Bulk transport of substances from one area to another, in one direction ( controlled by the valves) due to a difference in pressure caused by the heart.

as an organism increases in size, diffusion becomes insufficient as its too slow at providing cells with the materials it needs, so multicellular organisms have a mass transport system which overcomes the limitations of diffusion.

Requirements for a mass transport system:

• A network to move through ( vessels)

• A medium for movement ( blood)

• Controlled direction

Closed circulatory system:

• ALL VERTEBRATES

• Blood is enclosed within the blood vessels, don't come into direct contact with tissue cells

• This generates a higher blood pressure as it forces blood through fairly narrow channels instead of flowing through large cavities

• Its highly responsive to the changing needs of the organ and is highly efficient

• For active and larger animals

Open circulatory system:

• for molluscs and arthropods

• Pumps blood into a hemocoel which can diffuse back into a circulatory system between cells

• Blood is pumped by a heart into a body cavity where tissues are surrounded by blood.

• When the heart relaxes, blood fills back into the heart from the cavity.

Double circulatory system:

• Prevents the mixing of deoxygenated and oxygenated blood

  • More efficient and creates a high bp

• Pulmonary circulation: deo2 blood moves from heart to the lungs

  • O2 taken on and co2 excreted

  • O2 blood moves back from the lungs to the heart

• Systemic circulation: o2 blood moves from the heart to the rest of the organ systems in the body

  • O2 is delivered and co2 Is taken on

  • Deo2 blood flows from organ systems in body back to the heart

This provides a high blood pressure which in turn gives multicellular organisms a higher metabolic rate, the substances needed for metabolic reactions ( o2 and c6h12o2) are delivered at a faster rate to the cells and meets the needs of the organism.

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