Overview of Cardiovascular System

systemic circulation

left heart and the systemic arteries, capillaries, and vein; high-pressure, high-resistance circulation

pulmonary circulation

right heart, pulmonary arteries, capillaries, and veins; low-pressure, low-resistance circulation

venous return

rate at which blood is returned from the veins to the right atria

Cardiac output

Stroke volume X heart rate

Function of AV valves

closure of mitral and tricuspid valves at the start of systole produces first heart sound “lub”

Function of semilunar valves

closure of aortic and pulmonary valves at the end of systole produces second heart sound “Dub"

Sinoatrial (SA) node

pacemaker of the heart

Conduction system of the heart

sinoatrial (SA) node => atria => atrioventricular (AV) node => His bundle (AV bundle) => bundle branches => Purkinje fibers => ventricles

Intercalated discs

gap junctions that allow rapid diffusion of ions and spread of AP

Atrial syncytium

atria contract as one unit

Ventricular syncytium

ventricles contract as one unit

Diastole

relaxation of ventricles in order for them to fill with blood; “dub” sound made by the closure of the semilunar valves (pulmonary, aortic); atrioventricular valves open

Systole

contraction of ventricles in order for them to pump blood out of the heart; “lub” sound made by the closure of the atrioventricular valves (tricuspid, mitral); semilunar valves open

primary function of cardiovascular system

transport of essential nutrients to tissues and waste products from the cells to organs that excrete them (lungs, liver, kidney); includes metabolic substrates, hormones, water, electrolytes, blood cells, antibodies, clotting factors, and waste products

Homeostatic functions of the cardiovascular system

adequate blood flow, blood pressure, distribution, and perfusion of the tissues; delivery of hormones from endocrine glands to their target tissues; regulation of body temperature; making adjustments to altered physiological states

How does the cardiovascular system regulate body temperature?

heat is brought from deep tissues to surface tissues

Adequate blood flow depends on…

1. Pressure (normal heart function)

2. Viscosity (optimal blood volume and blood constituents)

3. Radius of blood vessels

4. Colloid osmotic pressure, capillary pressure (exchange between the capillaries and tissues)

Ischemia

inadequate blood flow that deprives the tissues of oxygen

Stroke

cerebral infarction

thrombus

blood clot that forms inside a blood vessel, obstructing blood flow

primary cardiovascular dysfunctions

conditions and diseases that affect the CVS directly

loss of blood (hemorrhage)

primary dysfunction that decreases blood flow to organs and affects their functions

myocarditis

primary dysfunction in which inflammation of the heart muscles results in a reduced ability of the heart to pump blood

congenital disease

condition that is present when the animal is born

Heart failure

decreased ability of the heart to pump enough blood to the tissues (can be acquired or congenital)

Exercise intolerance

occurs when animals may be able to pump enough blood at rest but not enough during exercise; can be caused by acquired or congenital diseases

How do heartworms cause CVS dysfunction?

in dogs can cause a blockage in the right ventricle and pulmonary artery that impedes blood flow and affects the body’s ability to control blood pressure

Strongyles worms

intestinal parasites in horses that get lodged in mesenteric arteries and impede blood flow in the intestines, reducing motility and secretion; horses exhibit signs of colic

Secondary cardiovascular dysfunctions

condition or disease in another system that causes issues with the CVS

What does persistent diarrhea or vomiting result in?

loss of water and electrolytes; change in electrolyte concentrations leads to disruption of heart function (e.g. arrythmia, ineffective pumping by heart muscle, heart failure)

How can anesthetics negatively affect the CVS?

anesthetics can depress the CNS and cardiac output, and decrease blood pressure; barbiturates directly depress the pumping action of the heart

Bulk flow

mode of transportation that moves blood through blood vessels rapidly over a long distance (10 seconds from the aorta to distant parts of the body)

How is the energy for bulk flow provided?