cardiovascular system

functions of the cardiovascular system

• transportation (RBC’s, plasma, nutrients, waste products)

• protection (WBCs and platelets (to protect against infection and blood loss))

• regulation (temp, PH, plasma ((maintain fluid balance and homeostasis)

3 main types of blood vessels

• arteries carry blood away from the heart

• capillaries provide exchange between blood and tissues

• veins carry blood towards the heart

circulatory system

Circulatory system is a conduit of vessels that conducts blood to the entire body (so that all cells are near a constant blood supply)

oxygenated parts of the circulatory system

• arteries: thick walled, elastic and muscular to withstand pressure exerted by blood pumped by the beating heart

  • aorta is largest artery

• smaller than arteries, have muscular walls that constrict or relax to control blood pressure

deoxygenated parts of the circulatory system

• venules: smaller than veins

• veins: thinner walls than arteries, have valves to maintain blood flow in right direction since much lower pressure in them, muscles squeeze them to help blood flow–Inferior vena cava and

  • Superior vena cava are largest veins

both oxygenated and deoxygenated part of circulatory system

capillaries: simple epithelial lining, very thin walled. Functional unit for exchange between blood and tissue cells

all parts of circulatory system

• arteries

• arterioles

• capillaries

• venules

• veins

pulmonary circulation (circulatory system between heart and lungs)

1. pulmonary artery

   • carries deoxygenated blood from the right ventricle of the heart

   • Branches into right and left pulmonary arteries, then into smaller arterioles within the lungs.

2. pulmonary capillaries

   • Surround the alveoli (air sacs)

   • Gas exchange occurs here:

     • Oxygen diffuses from alveoli → into capillaries → binds to hemoglobin in RBCs.

     • Carbon dioxide diffuses from plasma → into alveoli → exhaled

3. venules and veins

   • collected oxygenated blood from the capillary networks

4. pulmonary veins

   • carry oxygenated blood back to the left atrium of the heart

systemic circulation (between heart and rest of the body)

1. aorta

   • Carries oxygenated blood from the left ventricle of the heart.

   • Branches into arteries, then arterioles, which supply all body organs and tissues.

2. systemic capillaries

   • gas and nutrient exchange occurs here:

     • Oxygen unbinds from hemoglobin in RBCs and diffuses through capillary walls → into tissues.

     • Carbon dioxide leaves tissues → diffuses into capillaries → dissolves in plasma

3. venules and veins

   • collect deoxygenated blood from capillary beds

4. superior and inferior vena cava

   • return deoxygenated blood from upper and lower body to right atrium of heart

how the heart is a double pump

• Right side pumps deoxygenated blood from the rest of the body to the lungs (Pulmonary Circuit)

• Left side pumps oxygenated blood from the lungs to the rest of the body (Systemic)

functions of the heart

1. pump

2. rhythm/electrical activity

3. coronary arteries (blood flow to the heart tissue itself)

structure of the heart

• The heart is made up of cardiac muscle cells called the myocardium.

• Myocardial cells contract and relax in a coordinated rhythm to keep blood moving efficiently

four chambers of the heart

• Right Atrium – receives deoxygenated blood from the body

• Right Ventricle – pumps blood to the lungs (pulmonary circuit)

• Left Atrium – receives oxygenated blood from the lungs

• Left Ventricle – pumps blood to the rest of the body (systemic circuit)

two phases of the cardiac cycle

1. diastole

2. systole

diastole (relaxation phase)

• Heart muscle relaxes, allowing chambers to fill with blood.

• Atrioventricular (AV) valves (tricuspid and mitral) are open.

• Semilunar valves (pulmonary and aortic) are closed

blood flow:

• From veins → atria → ventricles (passive filling).

• Ends with a brief atrial contraction that tops off ventricular volume.

systole (contraction phase)

• Ventricles contract, pumping blood out of the heart.

• AV valves close (prevent backflow).

semilunar valves open:

• Right ventricle → Pulmonary artery (to lungs).

• Left ventricle → Aorta (to body).

• After ejection, ventricles relax, and the cycle repeats.

cardiac rythym

• The electrical activity of the heart determines its rhythm and coordination.

• Electrical signals tell cardiac muscle cells when to contract and relax in sequence.

• This ensures efficient pumping of blood through both circuits.

Cardiac Conduction System

The heart contains a specialized conduction system that generates and propagates electrical impulses:

• Sinoatrial (SA) node – the natural pacemaker; initiates each heartbeat.

• Atrioventricular (AV) node – delays the signal, allowing atria to contract before ventricles.

• Bundle of His → Bundle branches → Purkinje fibers – spread the impulse through ventricles for coordinated contraction.

BP

• the force exerted by circulating blood on the walls of blood vessels.

• It ensures continuous blood flow through the circulatory system to deliver oxygen and nutrients

what determines blood pressure

• Cardiac Output (CO):

  • Amount of blood pumped by the heart per minute.

  • ↑ Cardiac output → ↑ Blood pressure.

• Vascular Resistance:

  • Opposition to blood flow in vessels (mainly arterioles).

  • Narrower vessels → higher resistance → higher pressure.

measuring BP

• Pressure varies throughout the circulation:

  • Highest in arteries, lowest in veins.

• Routinely measured in the brachial artery of the arm (easily accessible and reflects central pressure).

• Can be measured in any artery where blood flow is strong and close to the surface.

high blood pressure means

your heart is pumping more blood and your arteries are narrow