This page is optimized for mobile devices, if you would prefer the desktop version just click here

2.3.1 blood circulatory system  (Page 7/8)

Figure showing capillaries as the transition between arteries and veins

http://en.wikipedia.org/wiki/File:Illu_capillary.jpg

Interactive diagram illustrating arterial and venous structure.

http://www.phschool.com/science/biology_place/biocoach/cardio2/structure.html

Figure

Shows the how valves cause blood to only flow one way though veins

http://upload.wikimedia.org/wikipedia/commons/thumb/4/4a/Venous_valve.svg /2000px-Venous_valve.svg.png

Capillaries

  • Capillaries are little more than a single layer or endothelial cells.
  • Capillaries form intricate networks throughout the tissues.
  • They allow water, nutrients and gasses to diffuse out of the blood and waste materials to diffuse into the blood.
  • This exchange occurs between the blood and the interstitial fluid.
  • The interstitial fluid is the fluid surrounding the cells.
  • The blood never comes into contact with the cells.
  • The blood and interstitial fluid exchange material, and the interstitial fluid then exchanges material with the cells.

Veins

  • The intricate networks formed by the capillaries eventually converge to form venules, (small veins)
  • The venules then converge to form veins which return the blood to the heart.
  • Veins only consist of two layers.
  1. The outer layer is made up of connective tissue
  2. The inner layer is made up of endothelial cells.

Valves

  • Once the blood has passed through the capillaries very little blood pressure remains to return blood to the heart.
  • Instead of pressure from the heart veins use a series of valves to force blood to return to the heart.
  • Contraction of the muscles squeezes the veins, pushing the blood through them.
  • The valves cause the blood to flow in only one direction, back to the heart.

Figure showing capillaries as the transition between arteries and veins

http://en.wikipedia.org/wiki/File:Illu_capillary.jpg

Interactive diagram illustrating arterial and venous structure.

http://www.phschool.com/science/biology_place/biocoach/cardio2/structure.html

Figure

Shows the how valves cause blood to only flow one way though veins

http://upload.wikimedia.org/wikipedia/commons/thumb/4/4a/Venous_valve.svg /2000px-Venous_valve.svg.png

Veins

  • The intricate networks formed by the capillaries eventually converge to form venules, (small veins)
  • The venules then converge to form veins which return the blood to the heart.
  • Veins only consist of two layers.
  1. The outer layer is made up of connective tissue
  2. The inner layer is made up of endothelial cells.

Valves

  • Once the blood has passed through the capillaries very little blood pressure remains to return blood to the heart.
  • Instead of pressure from the heart veins use a series of valves to force blood to return to the heart.
  • Contraction of the muscles squeezes the veins, pushing the blood through them.
  • The valves cause the blood to flow in only one direction, back to the heart.

Figure showing capillaries as the transition between arteries and veins

http://en.wikipedia.org/wiki/File:Illu_capillary.jpg

Interactive diagram illustrating arterial and venous structure.

http://www.phschool.com/science/biology_place/biocoach/cardio2/structure.html

<< Chapter < Page Page > Chapter >>

Read also:

OpenStax, Siyavula: life sciences grade 10. OpenStax CNX. Apr 11, 2012 Download for free at http://cnx.org/content/col11410/1.3
Google Play and the Google Play logo are trademarks of Google Inc.
Jobilize.com uses cookies to ensure that you get the best experience. By continuing to use Jobilize.com web-site, you agree to the Terms of Use and Privacy Policy.