Cardiovascular System Notes

Cardiovascular System

Objectives

• Describe the location, structure, & function of the heart and the pathway of blood through the heart.
• Identify, compare, & contrast the body’s major arteries and veins, and the exchanges that occur across capillary walls.
• Describe the development of the cardiovascular system and explain how exercise & diet may help maintain cardiovascular health.

Heart Facts

• The heart is a hollow muscular organ roughly the size of your fist.
• It weighs less than 1 lb.
• Fully developed about 8 weeks after conception and begins beating at 4 weeks.
• Every minute the heart pumps our entire supply of blood through the body (About 5qts).
• Women have faster heartbeats than men.
• Normal pulse is 70 heartbeats per minute.

Function

• A closed system of the heart & blood vessels (& blood).
• The heart pumps blood.
• Blood vessels allow blood to circulate to all parts of the body.
• Functions to deliver O2 and nutrients and to remove CO2 and other waste products.

Heart Anatomy

Location

• Medially in the thoracic cavity.
• Pointed tip (apex) directed toward the left hip. The APEX is 9 cm to the left of the midsternal line.

Coverings

• Outer Coverings:
  • Pericardium – a double membrane, protective sac around the heart
    • Visceral Pericardium – inner layer
    • Parietal Pericardium – outside layer
• Inner Coverings:
  • Walls of the heart are made up of 3 layers of tissue
    • Outer Layer à called PERICARDIUM (Epithelial tissue)
    • Middle Layer à called MYOCARDIUM (Cardiac muscle tissue)
    • Inner Layer à called ENDOCARDIUM (Epithelial tissue)

Chambers

• Atria:
  • Receiving chambers (the top chambers)
  • Right Atrium
  • Left Atrium
• Ventricles:
  • Discharging chambers (bottom chambers, the actual "pumps" in the heart)
  • Right Ventricle
  • Left Ventricle

Valves

• Allow blood to flow in only 1-direction to prevent backflow in the heart.
• Atrioventricular – b/t atria & ventricles
  • Bicuspid Valve (Mitral Valve) – left side.
  • Tricuspid Valve – right side.
• Semilunar Valves–b/t ventricle & artery
  • Pulmonary Semilunar Valve.
  • Aortic Semilunar Valve.
• Valve Facts:
  • Blood travels in a one-way direction through the valves.
  • Valves open and close in response to pressure changes.
  • Held in place by Chordae Tendineae - - - - - - - - - “Heart Strings”.
• Artificial Valves:
  • Mechanical lasts forever BUT requires use of blood thinners.
  • Biological needs future replacement and does NOT require blood thinners (10 -15 yrs).
  • Types: Marble-in-a-cage, Tilting Disc, Saloon Doors, Pig Valves, Cow-Based Valves, Collapsible Valve
  • Valve Repair

Vessels

• Vena Cavas – superior & inferior:
  • Brings deoxygenated blood from the body tissues back to the heart.
• Pulmonary Arteries:
  • Carries deoxygenated blood away from the heart and to the lungs.
• Pulmonary Veins:
  • Brings oxygenated blood from the lungs back to the heart.
• Aorta:
  • Carries oxygenated blood away from the heart and to the body tissues.

Heart Diagrams

Refer to the transcript for diagrams of the heart and its internal anatomy, including:

• Brachiocephalic artery
• Superior vena cava
• Right pulmonary artery
• Ascending aorta
• Pulmonary trunk
• Right pulmonary veins
• Left common carotid artery
• Left subclavian artery
• Aortic arch
• Ligamentum arteriosum
• Left pulmonary artery
• Left pulmonary veins
• Left atrium
• Auricle
• Right atrium
• Right coronary artery
• Anterior cardiac vein
• Right ventricle
• Marginal artery
• Small cardiac vein
• Inferior vena cava
• Circumflex artery
• Left coronary artery
• Left ventricle
• Great cardiac vein
• Anterior interventricular artery
• Apex
• Fossa ovalis
• Tricuspid valve
• Chordae tendineae
• Pulmonary semilunar valve
• Bicuspid valve
• Aortic semilunar valve
• Interventricular septum
• Myocardium
• Visceral pericardium

Circulation

Pulmonary Circulation

• PATH: RIGHT SIDE of heart à LUNGS à LEFT SIDE of heart
• FUNCTION: Carry blood to the lungs for gas exchange
• RIGHT Ventricle = PULMONARY Pump

Systemic Circulation

• PATH: LEFT SIDE of heart à BODY TISSUES à RIGHT SIDE of heart
• FUNCTION: Supply Oxygen and nutrient- rich blood to all body organs
• LEFT Ventricle = SYSTEMIC Pump

Cardiac Circulation

• Blood in heart chambers does NOT nourish the myocardium.
• Heart has its own nourishing circulatory system.
  • Coronary Arteries
  • Cardiac Veins

Blood Circulation

• Includes Pulmonary and Systemic Circuits with oxygen-rich and oxygen-poor blood flow.
  • Pulmonary Circulation: Venae cavae → Right atrium → Right ventricle → Pulmonary arteries → Capillary beds of lungs (gas exchange) → Pulmonary veins → Left atrium → Left ventricle
  • Systemic Circulation: Aorta and branches → Capillary beds of all body tissues (gas exchange) → Venae cavae

Heart Surgery

• Heart-lung machine à cardio-pulmonary bypass
• Body cooling → more time for surgery without causing brain damage (56F … ~4-6 hours)
• KCl injections → paralyzes the heart muscle, temporarily.
• Artificial heart transplant → Dr. Robert Jarvik began in mid 70’s; success in 1982.
• Donor heart transplant → ice vs. heat?
• Common maximum organ preservation times: Heart, lung: 4-6 hours, Liver: 8-12 hours, Pancreas: 12-18 hours, Kidney: 24-36 hours.
• Organ donation facts: More than 120,000 people in the U.S. are waiting to receive a life-giving organ transplant.
• Organ Shortage: Public Health Care Crisis.
  • the trade of human organs for the purpose of transplantation
  • organ trafficking accounts for ~10% of all kidney transplants worldwide!
  • organ trafficking trade involves a network of human traffickers including surgeons, brokers, patients, and sellers
  • some doctors believe organ sales should be legalized, but tightly regulated

Heart Physiology

Intrinsic Conduction System (Nodal System)

• Nodes à Specialized tissue that functions as both muscle & nervous tissue; contracts like MT and generates nerve impulses like NT.

  1. SinoAtrial Node (Pacemaker).
  2. AtrioVentricular Node (AV Node).
  3. AV Bundle (Bundle of His).
  4. Bundle Branches.
  5. Purkinje Fibers.

• Sets the pace.

• ELECTROCARDIOGRAM (ECG OR EKG) → maps the electrical activity of the heart.

The Cardiac Cycle

• EVENTS OF ONE COMPLETE HEARTBEAT (.8s).
• Atria Contract – Simultaneously.
• Atria Relax.
• Ventricles Contract.
• SYSTOLE = Contraction.
• DIASTOLE = Relaxation.
• POLARIZATION – heart at rest à NO impulse, NO stimulation, NO contraction and NO measurable activity.
• DEPOLARIZATION – the discharge of electrical energy.
• REPOLARIZATION – the electrical recovery of the heart as the cells recharge themselves.

ECG Waves

• P wave: represents depolarization of both atria.
• QRS complex: represents ventricular depolarization.
• ST segment: important in identifying pathology such as myocardial infarctions (elevations) and ischemia (depressions).
• T wave: ventricular repolarization.

Cardiac Sounds

• LUB: Closing of AV Valves.
• DUB: Closing of the SL Valves.

Arrhythmia

• Tachycardia – above 100.
• Bradycardia – below 60.
• Irregular heartbeat
• Heart Murmur: Extra heart beat.
• Fibrillation: Rapid, irregular, and unsynchronized.

Cardiac Output

• Amount of blood pumped out by each ventricle of the heart in 1-MINUTE
• CO = HR \times SV \approx 5 \text{ quarts}
• STROKE VOLUME: Volume of blood pumped by each ventricle in one contraction
• CO = 75 \frac{\text{beats}}{\text{min}} \times 70 \frac{\text{ml}}{\text{beat}} = 5250 \frac{\text{ml}}{\text{min}}
• Stroke volume usually remains relatively constant
• Starling’s law of the heart – the more that the cardiac muscle is stretched, the stronger the contraction
• Changing heart rate is the most common way to change cardiac output

Regulation of Heart Rate

• Increased Heart Rate:
  • Exercise
  • Stress
  • Obesity
  • Hormones
  • Stimulants
  • Poor Stroke Volume
• HR_{max} = 220 - \text{age}

Blood Vessels

Three Layers (Tunics):

• Tunica Interna:
  • Endothelium (ET)
• Tunica Media:
  • Smooth Muscle Tissue (MT)
• Tunica Externa:
  • Mostly fibrous connective tissue (CT)

Structural Differences between Arteries and Veins

Movement of Blood Through the Vessels

1. Arteries: Most arterial blood is pumped by the heart
2. Veins: use the milking actions of muscles to help move blood
3. Capillary Beds:
   • Vascular Shunt directly connects an arteriole to a venule
   • True Capillaries are exchange vessels for gas, nutrients, & waste

Major Arteries of Systemic Circulation

• Internal carotid artery
• External carotid artery
• Vertebral artery
• Brachiocephalic artery
• Axillary artery
• Ascending aorta
• Brachial artery
• Abdominal aorta
• Superior mesenteric artery
• Gonadal artery
• Inferior mesenteric artery
• Common iliac artery
• External iliac artery
• Internal iliac artery
• Digital arteries
• Common carotid arteries
• Subclavian artery
• Aortic arch
• Coronary artery
• Thoracic aorta
• Branches of celiac trunk:
  • Left gastric artery
  • Splenic artery
  • Common hepatic artery
• Renal artery
• Radial artery
• Ulnar artery
• Deep palmar arch
• Superficial palmar arch
• Deep femoral artery
• Femoral artery
• Popliteal artery
• Anterior tibial artery
• Posterior tibial artery
• Dorsalis pedis
• Arcuate artery

Major Veins of Systemic Circulation

• Dural sinuses
• External jugular vein
• Vertebral vein
• Internal jugular vein
• Superior vena cava
• Axillary vein
• Great cardiac vein
• Hepatic veins
• Hepatic portal vein
• Superior mesenteric vein
• Inferior vena cava
• Ulnar vein
• Radial vein
• Common iliac vein
• External iliac vein
• Internal iliac vein
• Digital veins
• Subclavian vein
• Right and left brachiocephalic veins
• Cephalic vein
• Brachial vein
• Basilic vein
• Splenic vein
• Median cubital vein
• Renal vein
• Inferior mesenteric vein
• Femoral vein
• Great saphenous vein
• Popliteal vein
• Posterior tibial vein
• Anterior tibial vein
• Fibular vein
• Dorsal venous arch
• Dorsal digital veins

Blood Pressure

Pressure Points

• Temporal artery
• Facial artery
• Carotid artery
• Brachial artery
• Radial artery
• Femoral artery
• Popliteal artery
• Posterior tibial artery
• Dorsalis pedis artery
• Pulse - pressure wave of blood.
• Monitored at "pressure points" where pulse is easily palpated.

Blood Pressure Measurements

• Measurements by health professionals are made on the pressure in large arteries.
• SYSTOLIC – pressure at the peak of ventricular contraction (Norm = 120).
• DIASTOLIC – pressure when ventricles relax (Norm = 80).

Variations in Blood Pressure

• Normal: 110–140 mm Hg systolic, 75–80 mm Hg diastolic.
• HYPOtension: Low systolic (below 110 mm HG), Often associated w/ illness (heat=vasodilation).
• HYPERtension: High systolic (above 140 mm HG), Can be dangerous if it is chronic.

Blood Pressure: Effects of Factors

• Temperature:
  • Heat has a vasodilation effect
  • Cold has a vasoconstricting effect
• Chemicals: Various substances can cause increases or decreases
• Diet: Various substances can cause increases or decreases

Factors Determining Blood Pressure

• Exercise
• Postural changes
• Activates SNS Centers
• Kidney conserves water and salt
• Blood volume
• Chemicals (renin, nicotine and others)
• Blood viscosity
• Which brings about Vasoconstriction
• SV, HR, Cardiac output
• Peripheral resistance

Capillary Exchange

• Oxygen and nutrients leave the blood.
• Carbon dioxide and other wastes leave the cells.
• Substances exchanged due to concentration gradients.

Capillary Exchange Mechanisms

• Direct diffusion across plasma membranes.
• Endocytosis or exocytosis.
• Some capillaries have gaps (intercellular clefts).
  • Plasma membrane not joined by tight junctions.
• Fenestrations of some capillaries.
  • Fenestrations = pores.

Developmental Aspects of the Cardiovascular System

• A simple “tube heart” develops in the embryo and pumps by the fourth week.
• The heart becomes a four-chambered organ by the end of seven weeks.
• Fetal circulation à Arterial Ligamentosum & hole between atria.

CVS Disorders

• Aneurysm: A bulge or ballooning in the wall of a blood vessel, caused by a weakened spot.
• Arteriosclerosis: The hardening and stiffening of arteries, which can restrict blood flow and increase the risk of cardiovascular disease.
• Arrhythmia: Irregular heartbeat that can cause the heart to beat too fast, too slow, or with an irregular rhythm.
• Raynaud's Disease: A chronic condition that causes blood vessels in the extremities to narrow, reducing blood flow.
• Stroke: Occurs when blood flow to the brain is blocked or a blood vessel in the brain bursts.

Top Leading Causes of Death

1. Heart disease: 597,689
2. Cancer: 574,743
3. Chronic lower respiratory diseases: 138,080
4. Stroke (cerebrovascular diseases): 129,476
5. Accidents (unintentional injuries): 120,859
6. Alzheimer's disease: 83,494
7. Diabetes: 69,071
8. Nephritis, and nephrosis: 50,476
9. Intentional self-harm (suicide): 38,364