Circulatory System Module 10

Cardiovascular System

• Consists of the heart, blood vessels (arteries, veins, and capillaries), and blood
• Responsible for circulating blood, nutrients, oxygen, hormones, and waste products throughout the body

Heart

• Specialized cardiac muscle tissue
• Pumps oxygenated blood to the body and deoxygenated blood to the lungs

Blood Vessels

• Arteries: carry oxygenated blood away from the heart to various tissues and organs
  • Have thick, muscular walls to withstand high pressure
• Veins: carry deoxygenated blood back to the heart from the body’s tissues
  • Have thinner walls than arteries and often contain valves to prevent backflow
• Capillaries: tiny, thin-walled vessels where gas exchange and nutrient exchange occur between the blood and tissues

Four Chambers of the Heart

• Right Atrium: receives deoxygenated blood from the body via the superior and inferior vena cavae
• Right Ventricle: pumps deoxygenated blood to the lungs through the pulmonary artery
• Left Atrium: receives oxygenated blood from the lungs via the pulmonary veins
• Left Ventricle: pumps oxygenated blood to the rest of the body through the aorta

Layers of Connective Tissue in the Heart

• Myocardium: thick, middle layer of the heart wall, composed of cardiac muscle cells or cardiomyocytes
  • Contracts rhythmically to pump blood throughout the body
  • Striated, involuntary, highly resistant to fatigue
• Pericardium: double-layered sac that surrounds and protects the heart
  • Fibrous Pericardium: outer layer of dense connective tissue that provides protection and anchorage for the heart
  • Serous Pericardium: inner layer composed of two sublayers
    • Parietal Layer: lines the fibrous pericardium
    • Visceral Layer (Epicardium): directly covers the outer surface of the heart and is continuous with the epicardium
• Endocardium: innermost layer of the heart, consisting of endothelial cells and connective tissue
  • Provides smooth lining for the chambers of the heart and covers the heart valves
  • Helps reduce friction as blood flows through the heart and maintains the integrity of the heart’s structure
• Epicardium: outer layer of the heart wall, adjacent to the myocardium
  • Serves as protective layer and secretes lubricating fluid that reduces friction between the heart and surrounding structures

Lymph Vascular System

• Network of vessels and organs that play a crucial role in maintaining fluid balance, immune function, and lipid absorption in the body
• Lymphatic capillaries: tiny, thin-walled vessels located throughout the body's tissues
  • Collect excess tissue fluid (interstitial fluid), proteins, and cellular debris from the interstitial spaces and transport it as lymph
• Lymphatic vessels: larger vessels that collect lymph from lymphatic capillaries and transport it towards lymph nodes and eventually back into the bloodstream
  • Serve as conduits for transporting lymph and immune cells throughout the body
  • Have valves to prevent the backward flow of lymph and contain smooth muscle in their walls to help propel lymph forward
• Lymphatic ducts: largest lymphatic vessels that drain lymph into the venous circulation
  • Return lymph to the bloodstream, primarily through two main ducts: the thoracic duct