EKG Ch 3

Anatomy and Physiology

Key Concepts of Anatomy and Physiology

• The human body is comprised of 10 systems:

  • Each system describes both anatomy (the parts of the system) and physiology (how the system functions).

• Organs: Organized groups of tissues with specific functions.

• Tissues: Composed of cells, which are the basic units of the body.

• Homeostasis: A state of balance and stability maintained by the interaction of body systems essential for optimal body function.

  • Example: The nervous system regulates breathing to ensure sufficient oxygen intake from the respiratory system.

Body Systems Overview

Metabolism

• Metabolism: Refers to the physical and chemical processes that body systems perform to maintain homeostasis.

• Disease or injury can lead to changes in metabolism, impacting homeostasis and producing observable signs/symptoms during patient assessments.

Anatomical Terms

• Understanding anatomical terms is essential for describing body parts. Medical professionals use special terms to document locations and positions on the body.

Anatomical Terms for Parts of the Body

• Axilla: Armpit

• Thorax: Chest

• Thoracic cavity: Area inside the chest

• Mediastinum: Compartment in thoracic cavity where the heart is located

• Clavicle: Collarbone

• Sternum: Breastbone

Directional Anatomical Terms

• Anterior or ventral: Front of the body

• Posterior or dorsal: Back of the body

• Superior: Toward the head

• Inferior: Away from the head

• Medial: Toward the midline of the body

• Lateral: Away from the midline

• Proximal: Closer to the torso

• Distal: Farther from the torso

• Intercostal: Between the ribs

Anatomical Lines of Reference

• Midline: Imaginary line through the middle of the body.

• Midclavicular line: Line through the midpoint of the clavicle parallel to the midline.

• Anterior axillary line: Line parallel to midclavicular line from the anterior axillary fold.

• Midaxillary line: Line parallel to the anterior axillary line beginning at the midpoint of the axillary fold.

Importance of Medical Terms

• Anatomical terms aid EKG technicians in communicating effectively with healthcare teams. However, they must use lay terms when communicating with patients and families for better understanding.

Cardiovascular System

Parts and Functions

• Composed of the heart, blood vessels, and blood. A healthy cardiovascular system is critical for sustaining life.

• EKG technicians assist with tests providing insights into cardiovascular function.

Heart Location and Structure

• Located in the chest (thorax) between the lungs in the mediastinum.

  • Center of the heart is slightly to the left of the body's midline between the second rib and fifth intercostal space, tilted such that the base points toward the right shoulder and apex toward the left hip.

• Heart chambers:

  • Atria: Upper chambers that receive blood (left and right atria).

  • Ventricles: Lower chambers that pump blood (left and right ventricles).

• Blood volume in a healthy adult is approximately 5-6 liters.

  • Blood composition:

  • Plasma (liquid portion): 91% water and 9% dissolved substances (proteins, gases, hormones).

  • Formed elements (solid portion): 45% of blood volume, includes erythrocytes, leukocytes, and thrombocytes.

    • Erythrocytes: Carry oxygen and carbon dioxide.

    • Leukocytes: Protect the body against infections.

    • Thrombocytes: Involved in clotting.

Types of Blood Vessels

• Arteries: Carry oxygen-rich blood away from the heart; the aorta is the largest artery.

• Capillaries: Sites of gas and nutrient exchange between blood and cells.

• Veins: Carry oxygen-depleted blood back to the heart.

Respiratory System

Parts and Functions

• Works closely with the cardiovascular system to provide oxygen and eliminate carbon dioxide through breathing.

  • Inhalation: Intercostal muscles and diaphragm contract to draw air in.

  • Exhalation: Air is expelled from the lungs.

• Anatomy of the respiratory tract:

  • Air passes through the pharynx, into the larynx, and down the trachea, which divides into bronchi leading to the lungs.

  • Alveoli: Tiny sacs surrounded by capillaries where gas exchange occurs.

Interaction with Cardiovascular System

• Oxygenated blood moves from pulmonary capillaries to venules and then into pulmonary veins, returning to the left atrium of the heart.

Nervous System Relationship to Cardiovascular System

• Central nervous system (CNS): Comprises the brain and spinal cord; controls and coordinates body functions.

• Peripheral nervous system (PNS): Nerves branching off the CNS that control voluntary (somatic) and involuntary (autonomic) actions.

• Autonomic nervous system (ANS): Manages involuntary actions, including heart rate via electrical impulses stimulating the heart muscle to contract.

  • Sympathetic nervous system: Increases heart rate, respiratory rate, blood pressure; activated in stress situations (fight-or-flight response).

  • Parasympathetic nervous system: Decreases heart rate and fosters recovery after sympathetic stimulation.

Heart Structure

Layers of the Heart

• Epicardium: Outermost protective layer; contains coronary arteries.

• Myocardium: Thickest layer; muscular tissue enabling heart contraction.

• Endocardium: Innermost layer; smooth lining facilitating blood flow.

Major Vessels Related to the Heart

• Superior vena cava and inferior vena cava: Return oxygen-depleted blood to the right atrium.

• Pulmonary arteries: Carry deoxygenated blood from the right ventricle to the lungs.

• Pulmonary veins: Bring oxygenated blood back to the left atrium.

• Aorta: Distributes oxygenated blood from the left ventricle throughout the body; includes branches like the coronary arteries.

Heart Chambers and Valves

• The heart operates as a double pump:

  • Right side: Pumps oxygen-depleted blood to the lungs.

  • Left side: Pumps oxygen-rich blood to the body.

• Chambers:

  • Atria: Upper chambers.

  • Ventricles: Lower chambers.

• Heart valves:

  • Tricuspid valve: Between right atrium and right ventricle; prevents backwards flow during contraction.

  • Pulmonary valve: Between right ventricle and pulmonary artery; prevents backward flow into the heart.

  • Bicuspid valve (Mitral valve): Between left atrium and left ventricle; prevents backward flow during contraction.

  • Aortic valve: Between left ventricle and aorta; keeps blood flowing in the correct direction.

Blood Flow Through the Heart

• Blood flows from the right atrium to the right ventricle, then to the lungs via pulmonary arteries; returns oxygenated to the left atrium from the lungs via pulmonary veins, flows to the left ventricle, and is pumped throughout the body.

Circulatory Paths

Pulmonary and Systemic Circuits

• Pulmonary circuit: Blood circulation between the heart and lungs.

• Systemic circuit: Circulation of blood throughout the body, delivering oxygen and nutrients while removing waste products, ending with the return of oxygen-depleted blood to the right atrium.

Interaction of Systems

• The respiratory and cardiovascular systems are interdependent; dysfunction in one can lead to issues in the other. Examples:

  • Choking or asthma leads to reduced oxygen availability and impacts capillary oxygenation.

  • Fluid in the lungs from heart failure obstructs efficient oxygen and carbon dioxide exchange.

  • Heavy bleeding reduces circulation, limiting oxygen available to tissues despite healthy respiratory function.

• Hypoxia: Inadequate oxygen supply leading to symptoms such as cyanosis and potential brain dysfunction.

Chapter Review

• Anatomy and physiology study the body's components and their interaction for optimal function.

• Homeostasis achieved through systemic cooperation.

• Healthy cardiovascular systems are vital for life, and interaction with the nervous and respiratory systems is critical to maintain balance.