Cardiopulmonary Unit Notes

Mr. Rimmer Cardiopulmonary Systems (General Overview) Pope John XXIII High School November 12th 2008

LESSON GOALS • •

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State the components of the Cardiovascular/Pulmonary circulatory systems; Describe the manner in which the heart, lungs, arteries, capillaries and veins work together as a SYSTEM to move a drop of blood through the body; Describe the manner by which O2 and CO2 are regulated at the lung-tissue level.

The Circulatory System (CS) • Unicellular organisms provide for their own maintenance to sustain life, multicellular organisms must have nutrients brought to them. • The CV system does this by providing 60,000 miles of vessels to serve a trillion cells throughout the body!!!

Functions of Circulatory System (3) • Transportation – Respiratory – Nutritive – Excretory

• Regulation – Hormonal – Temperature

• Protection – Clotting and Immunity factors

THE GOAL IS HOMEOSTASIS

Components of the CV Circulatory System The cardiovascular system consists of three basic components: • The Heart: is a dual pump and contains four basic chambers: – –

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Two atria (Rt & Lt) Two ventricles (Rt & Lt)

Blood Vessels : passageways for blood to move to tissues (arteries) and from tissues (veins) Blood: is the medium in which material is transported either dissolved (gases) or suspended (cells).

The Heart & Types of Circulatory Systems •

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The heart is a pump that imparts pressure to the blood to cause it to flow down a pressure gradient (higher to lower (i.e. systolic pressure, Figure 1) Generally, the atria receive blood from venous return and transfers it to the ventricles to be pumped out to the lungs and rest of body. There are TWO cardiopulmonary circulations that we will consider: – –

Pulmonary (lungs) Systemic (body)

Blood Vessels • Form tubular network to carry blood from larger size vessels (e.g. aorta) to smaller vessels (capillaries) then back to larger veins. • In general, arteries carry OXYGENATED blood away from heart (red blood) and veins carry DEOXYGENATED blood to the heart (blue blood). – Color? • Veins are blue and arteries are red…WHY!

Now Let’s Trace a Drop of Blood in More Detail! • Blood enters the right atrium of heart by way of large veins called Inferior and Superior Vena Cavae. (See Figures 1) • This blood is DEOXYGENATED (O2 has been extracted by tissues & CO2 added from tissue). • Drop flows to right ventricle through the atrioventricular valve (AV) called the “Tricuspid” valve (Figure 1) • Valves are normally 1-way…WHY? (hint: heart murmur)

Let’s Trace a Drop of blood Through the Body • The right ventricle pumps DEOXYGENATED blood away to the lungs to load up on O2, through the semi-lunar / pulmonary valve and the Pulmonary Artery, (Figure 1) • This is called the Pulmonary Circulation. …but you just said that arteries transports oxygenated blood? What’s up??

Drop Con’t •From pulmonary circulation the OXYGENATED drop returns to left atrium via Pulmonary Veins (Figure 2). •Drop flows to left ventricle through another atrio-ventricular valve called“Bicuspid” or “Mitral valve” (two leaflets). •Ventricle propels drop to body thru the semilunar / aortic valve by way of largest artery, the Aorta. This is the Systemic Circulation.

Drop Con’t • Aorta then branches to progressively smaller vessels in a “tree-like” fashion. • Blood passes from arteries to arterioles (where blood pressure regulation takes place) and finally to capillaries feeding tissues where materials are exchanged. • Finally, blood then flows through venules (small veins) to larger veins (the vena cavae) and back to right heart for re-oxygenation.

**Summary of Circuit** • Right side of heart receives de-oxygenated blood and pumps it to the lungs via Pulmonary Artery (Pulmonary Circulation); • Left side of the heart receives oxygenated blood from lung via the Pulmonary Vein and pumps it to the rest of the body through the Aorta (Systemic Circulation)

Blood Pressure • The pulmonary circulation is a “low-pressure, low-resistance” system. (mean pressure ~2mmHg) • The arterial circulation is a “high-pressure, high resistance” system (mean pressure ~100mmHg). • Therefore, the left heart must work much harder than right to push blood out, so it is much more MUSCULAR. (Figure 1) • Ventricular pressure must be greater than this to move blood out…120/80 (systolic / diastolic) • 120 > 100=outflow to systemic system

Respiratory Organization “Respiration” refers to three related functions: • • •

Ventilation: mechanical act of breathing; Gas Exchange: occurs b/w air and blood as well as b/w blood and tissue; Oxygen Utilization: where the tissues perform energy-liberating reactions in mitochondria

Respiratory Anatomy The respiratory system is divided into two zones. • In the Conducting Zone, air moves from the Larynx to the Trachea, then splits into right and left primary bronchial trees (Figure 3). • In the Respiratory Zone, air moves from the terminal bronchi (which split in a tree-like manner) to the respiratory bronchi leading to the ALVEOLAR SACs.

Gas Exchange • The purpose of breathing is to supply fresh O2 for pick up and remove CO2 from the blood. – (Apollo 13) • Gas exchange occurs the alveoli that are wrapped by capillaries. Very thin membrane to easily allow movement of gases (Figure 3).

Respiration Physiology -Properties of Gas Exchange • At sea level, the TOTAL atmospheric (ATM) pressure is 760mmHg. • The air is composed of many gases, each exerting their own pressure independently. • Thus, each gas exerts it’s own Partial Pressure (PP or Pgas) on the overall ATM pressure.

Properties of Gases • For example O2= 21% of total air and and exerts a PO2 = 160 mmHg. • CO2 = 3% of total air and exerts a PCO2 = < 1 mmHg. • Other gases such as Nitrogen are present as well to make up the rest. • These gases dissolve in the blood.

Gas Exchange-How? • Fick’s Law states that gases will PASSIVELY move from regions of higher concentration to lower. • The PO2 at the level of the alveoli = 100 mmHg and is much greater than the tissue & capillary blood = PO2 =40mmHg. • This forms the PP gradient: 100 - 40 = 60 mmHg • This favors movement of O2 from alveoli into the blood to feed tissue.

Gas Exchange-How? • Similarly, the PCO2 at the level of the tissue = 46mmHg and is much greater than that in the alveoli capillary blood = PO2 =40mmHg gradient. • This forms the PP gradient: 46 - 40 = 6 mmHg • This favors movement of CO2 from the blood back into the alveoli and lungs to be removed by breathing.

The Result? • In the absence of disease, there exists a near perfect match between Ventilation (movement of fresh air into lung) and Perfusion (flow of blood in capillaries past the aveoli) • This is called The Ventilation Perfusion Ratio (Va/Q). It is near perfect during normal resting conditions (SaO2=97%). • What factors may cause changes to this ratio??? – Posture, exercise, smoking, obstructive diseases, emphysema, asthma etc.

Bottom Line • Names of heart structures and vessels • Which vessels carry loaded O2 in systemic vs pulmonary circulations • List all valves • Review pressure gradients • Trace drop of blood through heart

Wrap-Up • What did you learn today? • We’ll finish up this section tomorrow!!!

• The End-Thank You