The Circulatory System

Caramel Kitty
Mind Map by Caramel Kitty, updated more than 1 year ago
Caramel Kitty
Created by Caramel Kitty almost 5 years ago


parts of the circulatory system

Resource summary

The Circulatory System
  1. Heart
    1. blood is kept circulating throughout the body by means of a muscular pump; the heart
      1. relaxes
        1. fills up with blood
        2. contracts
          1. blood is squeezed out
            1. blood circulates through blood vessels which direct blood flow round the body
        3. Arteries
          1. blood vessels that carry blood away from heart
            1. need to be able to withstand the immense pressure of the blood as it is forced out of the heart
              1. have thick, muscular and elastic walls
                1. elastic layer is much thicker in arteries near the heart
                  1. elasticity enables artery wall to stretch and recoil or spring back
                    1. this helps to push the blood in spurts along the artery and also gives rise to the pulse
              2. constricts
                1. lumen becomes narrower & less blood flows through per unit time
                2. dilates
                  1. lumen becomes wider & more blood flows through it per unit time
                  2. most arteries carry oxygenated blood
                    1. except pulmonary arteries
                      1. carry deoxygenated blood from heart to lungs
                  3. Arterioles
                    1. aorta -> arteries -> arterioles -> capillaries
                    2. Blood Capillaries
                      1. found between the cells of almost all tissues
                        1. have walls made up of only a single layer of flattened cells (endothelium)
                          1. endothelium is partially permeable
                            1. enables certain substances to diffuse quickly through the capillary walls
                          2. branch repeatedly
                            1. numerous branches provide a large surface area for exchange of substances between blood & tissue cells
                            2. total cross-sectional area increases when arteriole branch into capillaries
                              1. this lowers blood pressure in capillaries
                                1. flow of blood is slowed down, giving more time for exchange of substances
                            3. Venules
                              1. before the capillaries leave an organ or tissue, they unite to form small veins called venules
                              2. Veins
                                1. venules in turn join to form bigger veins
                                  1. carry blood back to the heart
                                    1. blood pressure in veins is much lower than in the arteries
                                      1. blood flows more slowly and smoothly
                                        1. walls do not need to be as thick and muscular as of those arteries of about the same size
                                      2. contain less elastic tissue
                                        1. semi-lunar valves
                                          1. prevent blood from flowing backwards
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