2.3.1 blood circulatory system  (Page 6/8)

4.Analyse the results by comparing the total score with the following descriptors:

30 marks- you take very good care of your heart. Well done!

25 marks- you take good care of your heart. Keep it up!

20 marks- you take reasonably good care of your heart but need to work

on a few aspects where you scored 0.

15 marks- you need to take better care of your heart.

0-10 marks- you do not look after your heart at all. It’s time to make a

change to a healthier lifestyle.

Assessment Rubric

Rich media:

Khan Academy

http :// www . khanacademy . org / video / circulatory - system - and - the - heart ? playlist = Biology

Cardiac Magnetic Resonance imaging of Beating heart: Large magnets are used to create images of the heart inside the body, without the need for surgery.

http://upload.wikimedia.org/wikipedia/commons/7/73/Four_chamber_cardiovascular_m agnetic_resonance_imaging.gif

View from the top

http://commons.wikimedia.org/wiki/File:Beating_Heart_axial.gif

View from the side

http://commons.wikimedia.org/wiki/File:Cardiac_mri_ani_sagittal_bionerd.gif

Blood vessels

Structure and functioning of arteries, veins, capillaries and valves

Arteries

• Arteries carry blood from away from the heart. The pressure created by the pumping heart forces blood down the arteries.
• Arteries have three layers.

1. Outside layer – connective tissue
2. Middle layer – smooth muscle, allows contraction of the arteries to regulate blood flow and pressure
3. Inside layer – single layer of tightly connected simple squamous endothelial cells

• The large arteries close to the heart branch into smaller arterioles (smaller arteries) and eventually branch into capillaries.

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.