Circulatory Systems, Blood, & Blood Vessels

Learning Objectives

• Differentiate Circulatory Systems:

  • Open vs Closed Circulatory Systems

• System Organization:

  • Understand overall organization of the circulatory system

• Circulation Types:

  • Distinguish between single and double circulation

• Vessel Structure and Function:

  • Specifics about arteries, arterioles, capillaries, veins, and venules

• Blood Composition:

  • Identify the 4 components of blood along with their functions

Primary Functions of the Circulatory System

1. Transport:

   • Dissemination of nutrients, hormones, O2, CO2, and waste products.

2. Protection:

   • Transport immune system cells to combat infections.

3. Regulation:

   • Maintenance of homeostasis in various bodily conditions.

Linking Exchange Surfaces with Body Cells

• Circulatory system connects tissues where gas exchange, nutrient extraction, and toxin purification occur.

• Supplies interstitial fluid with oxygen and nutrients and removes waste products.

Overview of Circulatory Systems

• Components of a Circulatory System:

  • Circulatory fluid, interconnected vessels, heart as muscular pump.

• Types:

  • Open Circulatory System

  • Closed Circulatory System

Open Circulatory System

• Definition:

  • Circulatory fluid (hemolymph) directly bathes organs, nutrients/wastes exchanged between hemolymph and cells (O2 and CO2 not exchanged).

• Advantages:

  • Low metabolic cost, can adapt to metabolic demands.

• Disadvantages:

  • Limited selective delivery to tissues.

Closed Circulatory System

• Definition:

  • Blood is confined within vessels distinct from interstitial fluid; allows for more efficient chemical exchanges.

• Advantages:

  • Enables larger size organisms and differential blood flow adapted to metabolic needs.

Features of Closed Circulatory Systems

• Essential characteristics include:

  • Blood remains in vessels.

  • Arteries carry blood away from the heart; veins return it.

  • Capillaries are sites of exchange.

  • Adaptability and repair capability as the organism grows.

Arrangements in Closed Circulation

• Two Major Types:

  • Single Circulation

  • Double Circulation

Single Circulation

• Found in bony fish, rays, and sharks utilizing a two-chambered heart (1 atrium, 1 ventricle).

• Process:

  • Blood travels from the heart to gills for oxygenation then to tissue, returning partially deoxygenated blood back to heart.

Double Circulation

• Present in crocodiles, birds, and mammals with a four-chambered heart (2 atria, 2 ventricles).

• Blood flows separately in two circuits:

  • Pulmonary: oxygen-poor blood is sent to gas exchange tissues.

  • Systemic: oxygen-rich blood is sent to organs and tissues.

Pulmonary and Systemic Circulation

• Pulmonary Circuit:

  • Right side delivers deoxygenated blood to lungs.

• Systemic Circuit:

  • Left side propels oxygenated blood to body tissues.

More on Double Circulation

• Critical for maintaining higher blood pressure in organs vs single circulation.

Summary of Closed Circulatory Systems

• Recap:

  • Two arrangements: single and double.

  • Double circulation enhances pressure mechanics in organ function.

Heart Contraction and Circulation

• Description of coordinated heart contractions driving double circulation in mammals.

Vertebrate Cardiovascular System

• Type:

  • Closed circulatory system (cardiovascular system).

• Main Blood Vessels:

  • Arteries, veins, capillaries.

  • Blood flow is unidirectional, classified by direction, not oxygen content.

Systemic Organization of Vessels

• Breakdown of vessel functions:

  • Arteries: conduct blood away from heart.

  • Veins: project blood back to heart.

  • Capillaries: sites of gas and nutrient exchange.

  • Venules: small extensions of capillaries.

  • Arterioles: regulate blood distribution.

Anatomy of Arteries

• Structurally distinct layers, with arteries being thicker due to higher pressure requirements.

  • Construction:

    • Innermost: endothelium.

    • Arterioles branch from arteries; help deliver blood to capillaries.

Continuing Arteriole Structure

• Further detail: arterioles exhibit 1-2 layers of smooth muscle and connective tissue for delivery to capillaries.

Anatomy of Capillaries

• Structure: single layer of epithelial cells, smallest vessels, designated for gas and nutrient exchange.

Specialized Capillary Functions

• Essential functions:

  • Gas exchange in respiratory organs.

  • Nutrient and waste exchange with tissues (term pulmonary pertains to lungs).

Anatomy of Veins

• Veins possess thinner walls and larger chambers, facilitating low-pressure blood return to heart.

  • Venules—small extensions for blood entry before returning to heart.

Venule Functions

• Reiterate role of venules in blood flow back to heart, highlighting structure for efficient return at low pressure.

Venous Adaptations for Blood Return

• Include:

  • One-way valves prevent backflow.

  • Blood return aided by smooth muscle contraction and skeletal muscle movement.

Components of Blood

• Cellular Elements: 45%

• Plasma: 55%

  • Main constituents: water, electrolytes, plasma proteins.

• Functions of Blood: exchange, transport, and defense.

Functions of Plasma

• Osmotic Balance: rain, regulation of pH/viscosity and nutrient transport.

• Plasma proteins’ roles: immunoglobulins for defense and clotting factors.

Overview of Leukocytes

• Also known as white blood cells (WBC), crucial for immune responses, appearance in circulation and tissues.

Major Types of Leukocytes

• Include:

  • Lymphocytes (B and T cells), Neutrophils, Basophils, Monocytes, Eosinophils.

Erythrocytes (Red Blood Cells)

• Most numerous blood cells, lose organelles during maturation, contain hemoglobin for oxygen transport.

Role of Platelets

• Also termed thrombocytes, critical for blood clotting. They originate in bone marrow.

Platelet Function in Clotting

• Process involves collagen fibers, platelets, and factors leading to clot formation: enzymatic cascade producing fibrin from fibrinogen.

Aspirin's Effect on Platelets

• Aspirin inhibits platelet activity, aids in prevention of myocardial infarction (heart attack).