BIO120 Mod 10 PPT (Cardiovascular System 2024) (1)

Moving Fluids: Cardiovascular & Lymphatic Systems

The cardiovascular and lymphatic systems are crucial in maintaining homeostasis, regulating fluid balance, immune responses, and transporting vital substances throughout the body. These systems work in tandem to ensure that cells receive nutrients and oxygen, while also facilitating the removal of waste products.

Functions of the Cardiovascular System (CVS)

  • Transporting Blood: Blood functions as a transport medium, carrying oxygen, carbon dioxide, hormones, nutrients, and waste products to and from the cells of the body.

  • Exchange of Materials: The CVS allows for vital exchanges at the cellular level, where oxygen and nutrients diffuse into the cells while waste products such as carbon dioxide and urea diffuse into the blood for removal.

  • Generating Blood Pressure: The heart generates sufficient pressure to circulate blood through the vast network of arteries and veins, ensuring that oxygen-rich blood reaches all tissues.

  • Regulating Blood Flow: Blood flow can be adjusted based on the metabolic needs of various tissues in response to factors like exercise or stress, allowing for efficient distribution of resources.

Basic Anatomy of the Cardiovascular System (CVS)

  • Heart: The heart is structurally composed of two interconnected pumps— the right side pumps deoxygenated blood to the lungs, while the left side pumps oxygenated blood to the body. It operates efficiently to maintain continuous blood circulation.

  • Blood Vessels: The vascular system includes arteries, veins, and capillaries, which form a closed-loop system that transports blood throughout the body.

Blood Vessels Overview

  • Arteries: Carry oxygen-rich blood AWAY from the heart. Arterioles are smaller arteries that lead into capillaries, regulating blood flow into specific areas.

  • Capillaries: These tiny vessels are crucial for the exchange of gases, nutrients, and waste products. They create a network that facilitates the delivery and absorption of materials at the cellular level.

  • Venules and Veins: After the exchange, blood is collected by venules, which then converge into veins that return deoxygenated blood TOWARD the heart. Veins are characterized by thinner walls and the presence of valves that prevent backflow.

Structure of Blood Vessels

  • Layers of Tissue: Blood vessels comprise three main layers:

    1. Endothelium: The innermost layer that reduces friction as blood flows.

    2. Smooth Muscle: Middle layer that allows for vasoconstriction and vasodilation to regulate blood pressure.

    3. Connective Tissue: Provides structural support.

  • Arteries: Feature thick walls to withstand high pressures generated by the heart's contractions.

  • Veins: Have thinner walls and possess valves to prevent backflow; they hold approximately 70% of the body's blood at any given time, acting as blood reservoirs.

Capillaries

  • Exchange Functionality: Capillaries are the site for nutrient and gas exchange, with a structure that allows for permeability to small molecules, enhancing diffusion.

  • Stable Flow: The slow flow of blood through capillaries is essential for optimal nutrient absorption and waste removal.

Venous System

  • Venules: Collect blood from capillaries, where it is again low in pressure, and transport it to veins.

  • Veins: Return blood to the heart at lower pressures than arteries, with valves ensuring a unidirectional flow.

  • Role of Skeletal Muscles: Contractions of skeletal muscles during movement aid in venous return against gravity, particularly from the lower extremities.

Factors Affecting Blood Flow in Veins:

  • Skeletal Muscle Contraction: Helps pump blood through the veins during physical activity.

  • Respiratory Movements: Breathing creates pressure changes that facilitate blood flow back to the heart.

  • Valves in Veins: Prevents backflow of blood, allowing efficient return to the heart.

Heart Structure

  • Location: Positioned medial to the lungs and deep to the sternum.

  • Shape: The heart has a cone shape, with the apex pointing towards the left hip, providing efficient blood pumping.

  • Pericardium: A double-layered serous membrane that surrounds the heart, filled with lubricating fluid to reduce friction during beats.

Heart Layers

  • Myocardium: The thick muscular wall responsible for contracting and pumping blood.

  • Endocardium: The inner lining of the heart chambers that ensures smooth blood flow.

  • Epicardium: The outer layer of the pericardium, providing protection.

Chambers of the Heart

  • Atria: The two upper chambers (left and right) receive blood from the body and lungs respectively.

  • Ventricles: The lower chambers pump blood; the right pump sends blood to the lungs, while the left pump distributes it to the entire body. The left ventricle has a thicker myocardial wall to manage systemic circulation.

  • Septum: A wall that separates the left and right sides of the heart, preventing the mixing of oxygenated and deoxygenated blood.

Heart Valves

  • Types of Valves: Four total valves - two atrioventricular (AV) valves (Tricuspid and Bicuspid) and two semilunar valves (Aortic and Pulmonary).

  • Function: Heart valves ensure one-way blood flow, preventing backflow during contraction phases.

Circulatory Systems

  • Coronary Circulation: Specifically supplies the heart muscle with oxygen and nutrients via coronary arteries, critical for heart function.

  • Circuits of Blood Flow:

    • Pulmonary Circuit: Transports deoxygenated blood from the heart to the lungs for gas exchange.

    • Systemic Circuit: Delivers oxygenated blood from the left ventricle to body tissues and returns deoxygenated blood to the right atrium.

Blood Flow Pathway

  • Deoxygenated Blood Flow: Blood returns to the heart through the superior and inferior vena cavae into the right atrium, passes through the tricuspid valve into the right ventricle, exits through the pulmonary semilunar valve into the pulmonary trunk and travels to the lungs for oxygenation.

  • Oxygenated Blood Flow: Oxygen-rich blood is carried by pulmonary veins into the left atrium, flows through the bicuspid valve into the left ventricle, and is pumped out via the aorta to the body.

Lymphatic System Overview

  • Functions of the Lymphatic System:

    • Absorbs lipids in the small intestine through specialized lymphatic vessels called lacteals, facilitating fat absorption.

    • Provides a site for immune system cell maturation and proliferation in lymph nodes.

    • Absorbs excess tissue fluid and returns it to the bloodstream, where it is known as lymph, playing a crucial role in fluid homeostasis.

Characteristics of Lymphatic Vessels

  • Structure: Resemble veins but have thinner walls and valves that ensure unidirectional flow of lymph.

  • Lymph Movement: Relies heavily on the contraction of adjacent skeletal muscles, with little smooth muscle in their walls, making them more dependent on external forces for fluid movement.

Blockage of Lymph Drainage

  • Lymphedema: A condition where lymph drainage is blocked, leading to swelling in tissues; this can be caused by tumors, injury, surgical removal of lymph nodes, or parasitic infections.

Cardiac Cycle Overview

  • Heartbeat: Each heartbeat constitutes a cardiac cycle, which averages around 70 beats per minute, divided into phases for pumping and filling the heart.

  • Systole and Diastole Phases:

    • Systole: The pumping phase where all heart chambers contract, pushing blood out of the heart.

    • Diastole: The filling phase where the heart’s chambers relax and fill with blood.

Rhythm Control

  • The heart rhythm is regulated by the internal electrical conduction system, primarily initiated by the sinoatrial (SA) node, which generates impulses for contraction.

External Control of Heartbeat

  • Nervous System Influence: The cardiac control center located in the brainstem regulates heart rate through autonomic nervous system impulses, allowing for rapid adjustments in response to physiological needs.

  • Hormonal Influence: Stress or physical activity stimulates the adrenal glands to release adrenaline (epinephrine), which increases heart rate and cardiac output.

Blood Pressure in Arteries

  • Blood Pressure Dynamics: Blood pressure fluctuates with heart activity:

    • Systolic Pressure: Reflects the higher pressure in the arteries during ventricular contraction.

    • Diastolic Pressure: The lower pressure present in arteries during ventricular relaxation.

Normal Blood Pressure Levels:

  • Normal: systolic < 120 mmHg, diastolic < 80 mmHg

  • Prehypertension: systolic 120-139 mmHg, diastolic 80-89 mmHg

  • High: systolic ≥ 140 mmHg or diastolic ≥ 90 mmHg

Cardiovascular Disorders

  • Leading Cause of Death: Cardiovascular disease (CVD) encompasses a range of related conditions that pose significant health risks:

    • Hypertension: Often termed the ‘silent killer’ because it may be asymptomatic until severe complications arise, such as strokes or heart attacks.

    • Atherosclerosis: The gradual build-up of plaque in arteries, which can significantly narrow passages, increasing the risk of clots that lead to heart attacks or strokes.

    • Stroke & Heart Attack: Result from either an insufficient blood supply to the heart (myocardial infarction) or brain (cerebrovascular accident), often associated with long-standing high blood pressure or blocked blood vessels.

    • Aneurysm: An abnormal ballooning in the wall of a blood vessel, which may rupture, causing life-threatening internal bleeding and other severe complications.