Day 9: The Circulatory System

Overview of the circulatory system


       -Carries oxygen and food to the cells of the body

       Carries carbon dioxide and other waste away from cells to excretory organs, kidney, lungs and skin

      Aids in coagulation process


      Assists in defending body against disease


      And in regulation of body temperature

The circulatory system is a system of closed tubes. Circulation occurs in two large loops- the pulmonary circulation and the systemic circulation. The pulmonary circulation carries blood between the heart and the lungs for gas exchange, and the systemic circulation carries blood between the heart and the rest of the body's tissues. In both cases, arteries carry blood  from the heart to capillary beds, where exchange occurs. Veins return blood to the heart.

The Heart

     4 chambers

    Atria, right and left

    Ventricles, right and left

Septa: partitions separating the right and left sides of the heart

Cardiac cycle


              One complete contraction (systole ) and relaxation ( diastole ) of the heart

             Last about 0.8 seconds

Pulmonary circulation

     Carries blood from right ventricle of heart to lungs


     Carbon dioxide is removed: oxygen is picked up

      Oxygenated blood returns to the left atrium of the heart

Systemic circulation

         Carries oxygenated blood and nutrients from left ventricle to body cells


           Returns deoxygenated blood with carbon dioxide and wastes from cells to right atrium

-Origin of the heart sounds

The first sound: “LUBB” (ventricles contract, AV valves close )


 The second sound: “DUPP” ( ventricles relax, semilunar valves close )

Heart rate: number of heartbeats per minute

Cardiac output: volume of blood pumped by the heart in one minute

Pulse: palpable rhythmic dropping caused by alternating expansion and contraction of  an artery as blood passes through

Blood pressure: force exerted by blood on the walls of vessels


        Carry oxygenated blood away from the heart to issue

        Thick walls to withstand high pressure


         Aorta is the largest artery


     Return deoxygenated blood from tissue to heart

     Thin walls, low pressure

     Blood is moved by skeletal muscles movement, valves that prevent back flow, & pressure changes in breathing


   Microscopic, one-cell-thick vessels that connect arterioles & veins

   Site of gas exchange between blood and body tissues

Blood vessels layers

 Tunica Adventitia: outer, connective tissue


Tunica Media: Middle. Smooth muscles & elastic fibers

Tunica Intima: inner, Single layer endothelial cells, basement membrane, connective tissue & elastic internal membrance

Lumen: Internal space a blood vessel through which blood flows

Valves: thin membrane leaflets in veins prevents back flow of blood

Coronary artery diseases (CAD): Illness where the arteries that supply the heart muscle become narrowed, thickened, and hardened by the buildup of fatty deposit called plaque.

The plaque damages the inner lining of the vessel and causes hardening and thickening of the vessel wall. The name of this condition is atherosclerosis.

The major cause of coronary artery diseases is atherosclerosis (is the build-up of fat in the wall of the arteries).

As coronary artery diseases progress, the damaged to the coronary arteries can cause increase in the blood pressure and decreases blood flow to the heart muscle.

In extreme cases, a total blockage of the artery can result in heart muscle death (Heart Attack or Myocardial Infarction, MI).

Arteriosclerosis can also affect other arteries, including those in the brain and those that supply the arms and legs.

Coronary artery diseases can also cause complications if plaque becomes dislodged from the artery wall or if damage in the artery results in the formation of a blood clot.

Thrombus: blood clot that stays in the wall of the blood vessels.

Embolus: is when this thrombus dislodged from the wall of the blood vessel and goes into the blood flow.

Ischemia and Myocardial Infarction

When an embolus (Blood Clot) blocks the coronary artery, the heart muscle supplies by that vessel does not get enough oxygen, creating a condition called ischemia

Ischemia: pain cause by a lack of oxygen and blood

If ischemia in not treated, it may results in myocardial infarction (MI).

Myocardial infarction (MI) or heart attack:

Caused by complete block of blood flow to heart muscle, which results in tissue death.

Area of dead tissue may be large or small. Can result in serious heart damage or death.

Symptoms of a heart attack:

sudden severe pain in the chest, usually on the left side

skin color maybe pale or cyanotic (bluish)

anxiety- sense of doom

cold and clammy skin


skin that is pale, blue or gray, due to low levels of oxygen in the bloodstream

Angina pectoris:

the medical term for chest pain, pressure, or discomfort due to coronary artery disease.

Ok so now that we have covered the second lesson on Body Systems, lets revise the new terms we leaned on the following quiz.

Use the link below to start your work!