Circulatory System Overview

Circulatory System

• The heart pumps blood, delivering oxygen and removing waste products.
• Arteries carry oxygenated blood away from the heart; pulmonary arteries carry deoxygenated blood to the lungs.
• Capillaries facilitate gas exchange.
• Pulmonary veins carry oxygenated blood to the heart; systemic veins carry deoxygenated blood back to the heart.
• The lungs perform gas exchange.

Blood Functions

• Transportation: Blood carries gases, hormones, nutrients, and waste products.
• Protection: White blood cells (WBCs) and antibodies defend against pathogens; platelets and proteins are involved in clotting.
• Regulation: Maintaining pH, fluid balance, and temperature.

Bodily Fluids

• Blood: Found throughout the body, consisting of plasma and formed elements (RBCs, WBCs, and platelets)
  • Plasma: fluid matrix (no cells).
  • Formed elements: 45% of total blood volume.
  • Buffy coat: Leukocytes and platelets (less than 1%).
  • Hematocrit: Percentage of volume of all formed elements (45%).
• Plasma solutes: Ions, nutrients, gases, and waste (1%).
• Interstitial fluid: Derived from plasma, found in capillaries.
• Lymph: Found in lymph vessels, ground substance of blood without clotting proteins.
• Serum: Interstitial fluid without clotting proteins.

Blood Cell Types

• Formed elements (Blood Cells):
  • RBCs (Red Blood Cells): 55% of whole blood. Biconcave disks, no nucleus, and very flexible plasma membrane.
    • Functions: Gas transportation (oxygen binding). ATP generation.
  • Hemoglobin (color red pigment with 4 heme groups): Each heme has iron binding oxygen, for oxygen transport. Oxygen loading (oxygen binding) occurs in the lungs.
  • Oxyhemoglobin: bright red, hemoglobin bonded with oxygen.
  • Deoxyhemoglobin: dark red, hemoglobin not bonded with oxygen
  • WBCs (White Blood Cells): Less than 1%.
  • Platelets: Less than 1%. Involved in blood clotting.
  • For neutrophil type: 50-70 %, phagocytize infectious pathogens, nucleus segmented and varied in 2-5 lobes, granules appear light purple.
  • For eosinophil type: 1-4 %, attack parasitic worms, phagocytize antigen-antibody complexes, bilobed nucleus, granules stain reddish-pink.
  • For basophil type: .5-1 %, release histamine and heparin during inflammatory or allergic reactions, bi-lobed nuclei, granules stain blue-violet, occlude nucleus and cytoplasm.
• Others:
  • Lymphocytes (20-40%): Orchestrate immune responses, attack viruses/infected cells, produce antibodies (B cells), and natural killer cells.
  • Monocytes (2-8%): Exit blood vessels and become macrophages, phagocytize pathogens.

Heart Anatomy and Function

• Apex: Pointed end projecting inferolaterally.
• Base: Superior portion where major vessels attach.
• Fibrous pericardium: Surrounds the heart, fibrous sac lined with serous membrane, protects and anchors the heart, prevents blood from overflowing into the heart, provides friction-free environment.
• Serous pericardium: Parietal layer lines the inside of fibrous pericardium, visceral layer covers external surface of heart.
• Endocardium: Simple squamous epithelium and areolar connective tissue.
• Atria: Right atrium receives deoxygenated blood from superior and inferior vena cava and right and left pulmonary veins. Left atrium receives oxygenated blood from the lungs.
• Ventricles: Right ventricle pumps deoxygenated blood to the lungs, left ventricle pumps oxygenated blood to the body.

Blood Vessels

• Arteries: Carry oxygenated blood away from the heart, thick and muscular walls with smooth and elastic fibers to withstand high pressure, regulate blood flow. Tunica interna, tunica media, tunica externa.
• Arterioles: Small branches of arteries that lead to capillaries, thinner layer allowing blood flow and able to control blood flow, pressure through contraction.
• Capillaries: Sites of gas and nutrient exchange, single layer of endothelial cells.
• Venules: Collect blood from capillaries and transport to veins. Thin layer similar to capillaries to provide support & Minimal construction.
• Veins: Return deoxygenated blood to the heart, contain valves to prevent backflow, lower pressure than arteries, structural support and elasticity.

Lymphatic System

• Functions: Returns interstitial fluid to blood circulation; monitors interstitial fluid; mounts immune responses.
• Lymphatic capillaries: Closed-end tubes that collect interstitial fluid, and lipids (chyle in intestinal tract).
• Lymph nodes: Filter lymph; site of immune responses.

Lung Anatomy and Functions

• Respiratory Membrane: Alveolar simple squamous epithelial cells wall. Capillary endothelial walls.
• Alveoli: Sites of gas exchange in the lungs. Surfactant to prevent sticking.
• Pleura: Lining surrounding lungs to reduce friction. Parietal layer (thoracic wall); visceral layer (lung surface).