SC 3.2

• The Blood Circulatory System in Humans

  • The human blood circulatory system consists of the heart, blood and blood vessels.
  • The blood vessels that carry blood out of the heart are called arteries.
  • The blood vessels that carry blood into the heart are called veins.
  • In the veins, blood is prevented from flowing backwards by valves.
• • Pulmonary circulation consists of blood vessels that transport deoxygenated blood from the heart to the lungs to be oxygenated and returns oxygenated blood to the heart.
  • Systemic circulation consists of the aorta and all its branches (arteries) that transport oxygenated blood to the body tissues and returns deoxygenated blood to the heart.

  
• The Heart

  • The heart is a muscular organ which contracts and relaxes continuously to pump blood to the whole body.
• • There are four types of blood vessels connected to the heart:

  1. The vena cava carries deoxygenated blood from all parts of the body to the right atrium located at the right atrium
  2. The pulmonary artery carries deoxygenated blood from the heart to the lungs located at right ventricle
  3. The pulmonary vein carries oxygenated blood from the lungs to the heart located at left atrium
  4. The aorta carries oxygenated blood from the heart to the whole body located at left ventricle
  5. Blood capillaries carry blood from an artery to a vein.
• The period of time for blood to make one complete circulation from the heart to all parts of the body including the lung s and back to the heart is approximately 1 minute
• • The human heart have four chambers, divided into two parts
  • Left part
  • Upper part: Left atrium
  • Lower part: left ventricle
  • Right part
  • Upper part: Right atrium
  • Lower part: Right ventricle

  
• Structure and Function of heart

  Right atrium

  • Deoxygenated blood from the whole body except the lungs enters the right atrium through the superior and inferior vena cava
  • When the right atrium contracts, deoxygenated blood is forced to flow into the chamber below it, namely the right ventricle
• Structure and Function of heart

  Tricuspid valve

  • Allows the flow of blood in only one direction from the right atrium to the right ventricle

  Right ventricle

  • When the right ventricle contracts, deoxygenated blood is forced to flow out into the pulmonary artery to be carried to the lungs

  Semilunar valve

  • Semilunar valve at the pulmonary artery and aorta ensure that blood flows only in one direction and not back into the ventricles
• Structure and Function of heart

  Left atrium

  • Oxygenated blood from the lungs enters the left atrium through the pulmonary vein
  • When the left atrium contracts, oxygenated blood is forced to flow into the chamber below it, namely the left ventricle

  Bicuspid valve

  • Allows the flow of blood in only one direction from the left atrium into the left ventricle

  Left ventricle

  • When the left ventricle contracts, oxygenated blood is forced to flow out into the aorta to be carried to all parts of the body except the lungs.
• Structure and Function of heart

  Septum

  • Isolate the left chamber and the right chamber of the heart
  • Prevent oxygenated blood from mixing with deoxygenated blood
• The valve in the heart

  • Bicuspid valve: separates the left atrium from the left ventricle
  • Tricuspid valve: Separates the right atrium from the right ventricle
  • Semilunar valve: Located at the beginning of the aorta and the pulmonary vein

  Function of valve

  • Prevent the backflow of blood
  • Ensure that the direction of the flow of blood in one direction only
•  The functional efficiency of the human heart:

  • The heart wall is built of cardiac muscle that can contract and relax rhythmically
  • The ventricle has a thicker wall and contracts more strongly than the atrium
  • Has a valve that keeps the blood flowing in one direction only
  • Has a septum that ensures oxygenated blood and deoxygenated blood do not mix
• Blood vessels

  Artery

  Structure

  • Lumen size : Small
  • Wall : thick, muscular and elastic to withstand with blood with high pressure
  • No valve

  Function

  • Transport oxygenated blood from the heart to the whole body except the lungs
  • Pulmonary artery transport deoxygenated blood from the heart to the lungs

  Circulation of blood

  • Rapid blood flow under high blood pressure
  • Pulse detected
• Blood vessels

  Vein

  Structure

  • Lumen size : Large
  • Wall : Thin, less muscular and less elastic wall to facilitate blood flow under low blood pressure
  • has valves

  Function

  • Transport deoxygenated blood back to the heart from the whole body except the lungs
  • Pulmonary vein transport oxygenated blood from the lungs to the heart

  Circulation of blood

  • Slow blood flow under low blood pressure
  • No pulse
• Blood vessels

  Capillary

  Structure

  • Lumen size : smallest
  • Wall : Thinnest wall which is one cell thick without any muscle or elastic tissue
  • No valves

  Function

  • Allows the exchange of gases, food and waste products between the blood and body cells via diffusion through the thin wall of the capillary

  Circulation of blood

  • Slow blood flow under decreasing blood pressure
  • No pulse
• Heartbeat

  • When our heart is beating, the sound 'lub dub' is produced. The 'lub dub' sound can usually be heard using a stethoscope
  • 'Lub dub' sound is produced by the closing of valves in the heart
  • The 'dub' sound is produced by the closing of the semilunar valves in the aorta and pulmonary arteries (diastole)
  • The 'lub' sound is produced by the closing of tricuspid and bicuspid valves between the atrium and the ventricle (systole)
• Heartbeat

  • The reading of blood pressure that flows and fills the heart is called diastolic pressure reading
  • The reading of blood pressure that flows out of the heart is called systolic pressure reading
  • Blood pressure is take by using sphygmomanometer
• Cardiac cycle

  • Is the series of events that occur during one complete heartbeat, includes:
  • Contraction (systole)
  • Relaxation (diastole)
• Cardiac cycle

  • Is the series of events that occur during one complete heartbeat, includes:
  • Contraction (systole)
  • Relaxation (diastole)
  • Average: 72 heartbeats per minute
  • 1 cycle: 0.8 second
• Regulatory mechanism of blood pressure

  • Blood pressure: the force of the blood exerted on the walls of the arterial blood vessels
  • Arterial blood pressure
  • Highest during systole (contraction)
  • Lowest during diastole (relaxation)
  • Blood pressure reading
  • x/y mm Hg
  • x is the magnitude of systolic reading
  • y is the magnitude of diastolic reading
• Regulatory mechanism of blood pressure

  Blood pressure reading usually taken using a sphygmomanometer based on hearing the 'lub dub' sound produced by the closing of valves during the occurrence of systole and diastole

  Normal blood pressure: 120/80 mm Hg

  Systolic pressure = 120 mm Hg

  Diastolic pressure = 80 mm Hg

  Baroreceptors: receptors that monitor the pressure of blood
• The human circulatory system:

  • The human circulatory system is a closed tubular system that is pumped throughout the body
  • Double circulatory system
  • Pulmonary circulation - blood is transported from the heart to the lungs and back to the heart
  • Systemic circulation - blood is transported from the heart to other parts of the body (except the lungs) and back to the heart
• The cardiac care measures:

  • Reduce salt and sugar in food
  • Control blood pressure and diabetes
  • Exercise regularly at least five times a week
  • Eat vegetables and fruits