L5_Circulatory system I

Circulatory System Overview

• Principal Components:

  • Heart: the pump of the circulatory system.

  • Blood Vessels: the pipes that transport blood.

  • Blood: the fluid moved through the system.

• The cardiovascular system is influenced by:

  • Endocrine System

  • Nervous System

  • Kidneys

Functions of Blood

• Transport: Blood is responsible for:

  • Carrying oxygen to cells and removing carbon dioxide for excretion by the lungs.

  • Delivering nutrients, ions, water, hormones, and enzymes to body cells.

  • Carrying away waste products.

• Regulation: Blood helps regulate:

  • pH levels

  • Body temperature

• Composition:

  • Blood consists of plasma (55% of total blood volume, about 91% water) and formed elements (solids).

Two Loops in the Cardiovascular System

• Systemic Loop: Transports blood from the heart to the rest of the body.

• Pulmonary Loop: Carries oxygen-poor blood to the lungs and back to the heart.

• Emphasizes a closed system: leaks are detrimental.

Blood Circulation Details

• An average adult circulates approximately five liters of blood constantly.

• The heart functions as a double pump, crucial for:

  • Pulmonary circulation (blood through the lungs)

  • Coronary circulation (blood supply to the heart itself)

  • Systemic circulation (blood to the rest of the body).

Blood Components

• Plasma Proteins:

  • Albumin: Maintains osmotic pressure and water balance.

  • Globulins: Include antibodies to support the immune system.

  • Fibrinogen: Essential for blood clotting.

• Formed Elements:

  • Red Blood Cells (RBC): Contain hemoglobin for oxygen transport.

  • White Blood Cells (WBC): Part of the immune system.

  • Platelets (Thrombocytes): Crucial for clotting.

Pulmonary and Systemic Circulation Explained

• Pulmonary Circulation:

  • Blood travels from the heart to lungs to exchange carbon dioxide for oxygen.

  • Deoxygenated blood enters the right side of the heart via the superior and inferior vena cavae, goes to the lungs, and returns oxygenated to the left side of the heart.

• Systemic Circulation:

  • Oxygen-rich blood leaves the heart through arteries to capillaries, delivering oxygen and nutrients while collecting waste.

  • The blood returns to the heart via veins.

Structure of Blood Vessels

• Types of blood vessels include:

  • Arteries: Thick-walled, carry blood away from the heart, and maintain blood pressure.

  • Capillaries: Tiny, thin-walled vessels for gas and nutrient exchange between blood and tissues.

  • Veins: Thinner walls, assist in returning blood to the heart, and contain valves to prevent backflow.

Capillary Bed Functions

• Capillary Networks:

  • Enable the exchange of oxygen, carbon dioxide, water, and salts between blood and surrounding tissues.

Vasodilation and Blood Flow Regulation

• Vasodilation: Widening of blood vessels, increasing blood flow and decreasing blood pressure (opposite of vasoconstriction).

• Regulated by local tissue needs or external factors like hormones and nervous system signals.

Blood Vessel System in Skin

• The skin's vascular system nourishes skin cells and regulates temperature.

• Comprises a network of blood vessels, including a superficial network in the dermis and deeper vessels within the subcutis.

Skin Thermoregulation

• Body Temperature Maintenance:

  • Controlled by feedback mechanisms involving receptors in the skin and responses from the hypothalamus.

• Responses include:

  • Vasoconstriction: Reduces blood flow to skin when cold to minimize heat loss.

  • Vasodilation: Increases blood flow to skin when hot to promote heat loss.

  • Sweating: Further cooling through evaporation.

Structure and Function of the Heart

• Heart Chambers:

  • Atria: Thin-walled reservoirs for blood.

  • Ventricles: Thicker walls to pump blood over greater distances.

• Heart Valves: Ensure unidirectional blood flow (e.g., tricuspid and mitral valves).

Blood Pressure Characteristics

• Systolic Pressure: Peak arterial pressure during ventricular contraction.

• Diastolic Pressure: Minimum arterial pressure prior to contraction.

• Represented in mmHg and must be monitored as hypertension can lead to serious health issues.

The Heart's Conducting System

• Electrical Activity: Begins in the sinoatrial (SA) node, spreads to atrioventricular (AV) node, triggering heartbeats.

• Composed of specialized cells essential for heart excitation.

• Heart cells do not fully rest; they continuously contract with limited replacement ability.