Cardiovascular System

Applied Anatomy III: Cardiovascular System

Anatomy of the Cardiovascular System

  • Importance: Indicates it is a vital system for survival.

  • Components:

    • Blood

    • Heart

    • Circulatory system

    • Lymphatic system

Composition of Blood

  • Blood is a fluid connective tissue.

  • Types of Blood:

    • Whole blood: Blood contained in the cardiovascular system.

    • Peripheral blood: Whole blood in circulation carrying oxygen, nutrients, and waste.

Physical Characteristics

  • Gross Appearance: Opaque, deeply red fluid.

Components of Blood

  • Plasma: Liquid portion composed of:

    • Water: Major component.

    • Dissolved Salts for osmotic balance and pH:

    • Sodium (Na)

    • Chlorine (Cl)

    • Potassium (K)

    • Calcium (Ca)

    • Magnesium (Mg)

    • Bicarbonate

    • Proteins:

    • Albumin: Helps to hold water in blood.

    • Fibrinogen: Forms blood clots.

    • Immunoglobulins: Function as antibodies.

  • Blood Cells (solid portion):

    • Erythrocytes (Red Blood Cells - RBC): Most numerous.

    • Leukocytes (White Blood Cells - WBC), classified as:

    • Neutrophils

    • Eosinophils

    • Basophils

    • Lymphocytes

    • Monocytes

    • Thrombocytes (Platelets): Important for clotting.

Functions of Blood

  1. Transportation:

    • Carries gases, nutrients, and waste products.

    • Oxygen Transport:

      • Hemoglobin in RBCs binds oxygen in the lungs.

      • Releases oxygen at the capillary level.

      • Transports carbon dioxide and other waste products to liver and kidneys for excretion.

  2. Regulation:

    • Maintains tissue fluid balance:

      • Plasma may enter body tissues in case of dehydration, causing hemoconcentration.

      • Excess fluid from tissue goes into plasma causing hemodilution.

    • Regulates body temperature and blood pH for acid-base balance.

  3. Defense:

    • Carries leukocytes to tissues to combat infection.

    • Delivers thrombocytes to injury sites to prevent excessive bleeding.

Circulatory System

  • Overview: System of blood vessels.

  • Divided into Systems:

    • Systemic Circulation: Transports blood from heart to body and back.

    • Pulmonary Circulation: Transports blood from heart to lungs and back.

The Heart

  • Location: Middle of the thoracic cavity in the mediastinum.

  • Characteristics:

    • Muscular organ that rhythmically contracts to pump blood.

    • Specialized system controls heart muscle contraction rhythms.

    • Defined by two ends: base (rounded cranial end) and apex (pointed caudal end).

Chambers of the Heart

  • Four Chambers:

    • Atria: Left and right upper chambers receiving blood from the body.

    • Separated by the interatrial septum.

    • Auricles: Blind pouches resembling ear flaps.

    • Ventricles: Left and right lower chambers pumping blood out.

    • Separated by the interventricular septum.

    • Right side: Sends blood to lungs (Pulmonary Circuit).

    • Left side: Sends blood to the rest of the body (Systemic Circuit).

Valves of the Heart

  • Atrioventricular Valves: Prevent backflow from ventricles to atria.

    • Right AV valve: Tricuspid valve.

    • Left AV valve: Mitral valve.

  • Semilunar Valves: Prevent backflow from vessels into ventricles.

    • Left semilunar valve: Aortic valve.

Path of Blood Flow in the Heart

  • Receives deoxygenated blood and sends it to the lungs for oxygenation; returns oxygenated blood to the systemic circulation.

Blood Vessels

Overview

  • Blood travels through arteries, capillaries, and veins in a systemic pathway.

Arteries and Arterioles

  • Carry blood away from the heart under pressure.

  • Major Artery: Aorta, supplies the body.

  • Arteries have elastic walls enabling them to accommodate pressure and create pulses.

  • Type of blood:

    • Oxygenated blood in systemic arteries.

    • Deoxygenated blood in pulmonary arteries.

Capillaries

  • Function as exchange sites for oxygen, CO2, and nutrients.

  • Lowest diameter vessels (1 mm), with 1 second transit time.

Veins and Venules

  • Carry blood to the heart.

  • Largest Vein: Vena cava, returns deoxygenated blood to right atrium.

  • Have valves to maintain unidirectional flow. Does not exhibit pulse.

  • Types of blood:

    • Deoxygenated blood in systemic veins.

    • Oxygenated blood in pulmonary veins.

Cardiovascular Monitoring Techniques

  • Assess cardiovascular health using:

    • Auscultation

    • Peripheral artery palpation

    • Measurement of arterial blood pressure

    • Thoracic radiography

    • Electrocardiography (ECG or EKG)

    • Echocardiography

Lymphatic System

Overview

  • Two parts contributing to the immune system:

    • Duct system with fluid lymph.

    • Lymphoid organs and tissues.

Functions of the Lymphatic System

  1. Removal of Excess Tissue Fluid: Prevents edema.

  2. Transport of Waste Material: Carries waste to systemic circulation.

  3. Filtration: Filters microorganisms and debris before bloodstream entry.

  4. Protein Transport: Transports large proteins unable to enter venous circulation directly.

Lymph Characteristics

  • Appearance: Colorless fluid from excess tissue fluid.

  • One-Way System: Valves prevent reverse flow, ultimately draining into vena cava before heart.

Lymph Nodes

  • Filter lymph and produce lymphocytes for infection defense.

  • Activated nodes may enlarge and can be evaluated through fine-needle aspiration for diagnosis.

Palpable Lymph Nodes

  • Submandibular, prescapular, axillary, superficial inguinal, popliteal.

Spleen

  • Largest lymphoid organ, located on the left abdomen.

  • Functions:

    • Storage for erythrocytes.

    • Filters and destroys old RBCs.

    • Lymphocyte production.

    • Removes infectious organisms.

    • Removal impacts ability to eliminate certain infections.

Common Cardiovascular Conditions

Anemia

  • Defined as decreased RBC count or hemoglobin deficiency.

  • Causes: Hemolysis, blood loss, decreased production.

  • Signs: Weakness, collapse, exercise intolerance, pale membranes.

  • Diagnosis: Evaluated through Packed Cell Volume (PCV).

Congestive Heart Failure (CHF)

  • Types:

    • Right-sided: Blood backs up to systemic circulation leading to edema and ascites.

    • Left-sided: Blood backs up in lungs causing pulmonary edema.

  • Common in older dogs: Indicates inadequacy in heart pumping, leading to fluid accumulation and oxygen deprivation.

  • Signs: Exercise intolerance, coughing, tachypnea, shock.

Heartworm Disease (Dirofilaria immitis)

  • Impact: Serious, potentially fatal disease affecting multiple animal species.

  • Transmission: Via infected mosquito bites.

  • Consequences: Causes right ventricular dilation and CHF.

  • Diagnosis:

    • Antigen tests and blood smear to detect infection.

    • Radiographs allow for thoracic assessment.

Prevention and Treatment

  • Highly dangerous to treat once infected; involves injections to kill adult worms.

  • Preventative medication, tested annually for exposure before administration.

Heartworm Prevention for Canines

  • Medications:

    • Simparica Trio (oral, monthly)

    • Proheart (subcutaneous, every 6 or 12 months)

Heartworm Prevention for Felines

  • Medications:

    • Revolution Plus (topical, every 2 months)

    • Bravecto Plus (topical, every 2 months)

Differences in Infection Impact

  • Feline heartworm disease usually involves 1-4 worms, less symptomatic, higher risk of sudden death.

  • No effective treatment exists; many cats may clear infection spontaneously.