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The Human Circulatory System

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The circulatory system is the system that transports materials around the body to and from the cells.
 Question: Why do humans need a circulatory system whereas bacteria and simple organisms do not?AnswerBecause the cells of a complex organism such as a human have many cells that are far from the outside environment where nutrients would come from. The system brings the materials to the cells that would not normally receive them.

Humans have a closed circulatory system: This means that the blood is always contained in tubes and vessels.
The human circulatory system is composed of the following


  1. Blood vessels
  2. Heart
  3. Blood



BLOOD VESSELS
Humans have three types of blood vessels.  They are:
a.         Arteries

              Structure:     o Thick, elasti
                                o Contain layers of connective, and smooth muscle tissues 
             o DO NOT CONTAIN VALVES    
Function:  Carry Blood AWAY from the heart. Arteries divide to form very small arteries called arterioles.

b.         Veins

               Structure:    o   Thin and slightly elastic.
                                o   Contain VALVES for one way flow of blood.
Function:       return blood TO the heart
Veins divide to become venules.

Medical Alert:  Varicose Veins. This is a condition where the valves in the veins of a person are not working properly and blood seeps back into the vein causing the vein to become stretched and lose their elasticity.

Result: Sagging veins and lack of blood flow to the heart.

c.         Capillaries
            Structure:    o   Microscopic blood vessels that connect arterioles and venules
                                o   Thin walled and narrow
                                o   Blood cells pass through them in single file
Function:       Allows material and gas exchange between the body cells and the blood. 

THE HEART

 Structure: o   A four chambered muscular organ located in the chest cavity of a human.
                  o   Made of Cardiac muscle.
                  o   It is Covered by a Pericardium that protects it
                  o   Pericardium: A tough membrane that surrounds the heart.

Functions of Heart Structure

1.   Inferior/Superior Vena Cava:  Returns deoxygenated blood to the right atrium from the body.

2.   Right Atrium: Thin walled chamber of the heart that receives deoxygenated blood from the body

3.   Tricuspid valve: Controls the flow of blood entering the right ventricle from the right atrium

4.    Right Ventricle: Muscular chamber that pumps blood TO the lungs

5.    Semilunar Valves: Valves that control the flow of blood out of the heart

6.    Pulmonary Arteries: Arteries that carry blood TO the lungs

7.    Pulmonary Veins: Veins that bring blood to the heart from the lungs

8.    Left Atrium: Thin walled chamber that receives oxygenated blood from the lungs

9.   Left Ventricle: Thick walled chamber that pumps blood out of the heart and to the body

10.  Aorta: Large artery that carries blood away from the heart and to all parts of the body.

11.   Septum: A wall of muscle that separates the left side of the heart from the right side.This
 prevents the mixing of oxygenated and deoxygenated blood.

12.  Chordae Tendonae: Control the opening and closing of the Tricuspid and Bicuspid (Mitral) valves

13. Bicuspid Valve: A valve that controls the flow of blood from the left atrium to the left ventricle.
The Human Circulatory System The Human Circulatory System Reviewed by gafacom on May 31, 2019 Rating: 5

1 comment:

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