Detailed Notes on the Circulatory System

Circulatory System Overview

• The circulatory system is essential for transporting nutrients, gases, hormones, and waste products throughout the body.

Circulatory System Architecture

Open Circulatory System

• Definition: A system where hemolymph is pumped through blood vessels that empty into a body cavity (hemocoel).
• Functionality:
  • Hemolymph leaves vessels, flowing by cells and through tissues.
  • Returns to blood vessels through openings called ostia.
• Examples: Found in arthropods (e.g., bees) and most mollusks.

Closed Circulatory System

• Definition: A system where blood is contained within blood vessels.
• Circulation:
  • Blood flows unidirectionally from the heart, through a systemic circulatory route, and returns to the heart.
  • Two primary types of circulation:
  • Pulmonary Circulation: Moves blood between the heart and the lungs.
  • Systemic Circulation: Moves blood between the heart and the rest of the body.
• Pressure: Operates at relatively higher pressure.

Variations in Animal Circulatory Systems

Fish

• Heart Structure: Two-chambered heart.
• Blood Flow: Unidirectional; from heart through gills to the rest of the body.

Amphibians

• Heart Structure: Three-chambered heart (two atria and one ventricle).
• Circulation:
  • Oxygenation through lungs and skin.
  • Delivers oxygen to the rest of the body.

Reptiles

• Heart Structure: Three-chambered heart with partially separated ventricles.
• Blood Mixing: Some mixing of oxygenated and deoxygenated blood occurs.

Mammals and Birds

• Heart Structure: Four-chambered heart.
• Blood Flow: Completely separates oxygenated and deoxygenated blood.
  • Pumps only oxygenated blood to the body and deoxygenated to the lungs.

The Heart

• Anatomy: Hollow muscle with two upper chambers (atria) and two lower chambers (ventricles).
• Function: Pumps blood with the help of valves.
• Valves:
  • Atrioventricular Valves:
  • Tricuspid valve: Right atrium to right ventricle.
  • Mitral valve: Left atrium to left ventricle.
  • Semilunar Valves:
  • Pulmonary valve: Right ventricle to pulmonary artery.
  • Aortic valve: Left ventricle to aorta.

Blood Vessels

• Types:
  • Arteries: Carry blood away from the heart (oxygen-rich).
  • Muscular and capable of handling high pressure.
  • Capillaries: Microscopic vessels with thin walls.
  • Critical for gas and nutrient exchange between blood and tissues.
  • Veins: Carry blood back to the heart (deoxygenated).
  • Valves present to control blood flow.

Blood Composition

• Components:
  • Plasma: 90% water, contains coagulation factors and antibodies.
  • Serum: Plasma without coagulation factors.
  • Blood Cells:
  • Red Blood Cells (Erythrocytes): Contain hemoglobin, transport oxygen.
  • White Blood Cells (Leukocytes): Immune function; includes granulocytes, monocytes, and lymphocytes.
  • Platelets: Essential for blood clotting.

Functions of Blood

• Homeostasis: Maintains pH, temperature, and osmotic pressure; eliminates excess heat.
• Nutrient Distribution: Supports growth by distributing nutrients and hormones, removing waste.
• Immunity: Contains various components crucial for defending against diseases.

Diagnosis of Cardiovascular Abnormalities

• Techniques:
  • Physical examination (inspection, auscultation, palpation).
  • Imaging (X-rays, ECG, echocardiography).
  • Blood tests (complete blood count, cardiac biomarkers).
  • Specialized tests (cardiac catheterization, nuclear studies).

Types of Cardiovascular Abnormalities

• Causes:
  • Valvular diseases (valves not functioning properly).
  • Myocardial diseases (heart muscle function impairment).
  • Vascular diseases (issues in systemic vessels).
  • Cardiac shunts (abnormal blood flow between heart chambers).
  • Issues with blood volume (too much or too little).
  • Parasitic infections (e.g., heartworm disease).

Specific Cardiovascular Conditions

• Aortic Stenosis:
  • Narrowing in the heart affecting ventricular emptying, often detected via heart murmur.
  • Common in breeds like Golden retrievers and Rottweilers.
  • Symptoms: lethargy, exercise intolerance, heart dysfunction.
• Patent Ductus Arteriosus (PDA):
  • Incomplete closure of ductus arteriosus in puppies/kittens.
  • Consequences: volume overload and potential heart failure.
• Anaplasmosis in Ruminants:
  • Parasitic disease affecting red blood cells, leading to severe anemia and other symptoms.
• Heartworm Disease:
  • Caused by Dirofilaria immitis, often diagnosed through blood tests.
• Atrial Fibrillation:
  • Chaotic arrhythmia often secondary to heart disease, treated with medications to slow heart conduction.