Cardiovascular System

Layers of the Heart

The heart wall consists of three distinct layers, each with specific functions in cardiac physiology.

• Epicardium: The outermost layer, composed of connective tissue and fat, which protects the heart and reduces friction.

• Myocardium: The thick, muscular middle layer responsible for the contractile force needed to pump blood.

• Endocardium: The innermost layer lining the heart chambers and valves, providing a smooth surface for blood flow.

Heart Chambers and Valves

The heart contains four chambers and four valves, each facilitating the flow of blood through the heart and to the body.

• Chambers: Right atrium, right ventricle, left atrium, left ventricle. Each chamber receives or pumps blood to specific circuits.

• Valves: Tricuspid, pulmonary, mitral (bicuspid), aortic. Valves prevent backflow and ensure unidirectional blood flow.

Pulmonary and Systemic Circuits

The heart supports two major circulatory pathways: the pulmonary and systemic circuits.

• Pulmonary Circuit: Right side of the heart pumps deoxygenated blood to the lungs for oxygenation.

• Systemic Circuit: Left side of the heart pumps oxygenated blood to the rest of the body.

Blood Flow Pathways

Blood follows a specific pathway through the heart and circulatory system.

• Deoxygenated Blood: Returns to the right atrium via the superior and inferior vena cava, passes to the right ventricle, and is pumped to the lungs via the pulmonary artery.

• Oxygenated Blood: Returns from the lungs to the left atrium via pulmonary veins, passes to the left ventricle, and is pumped to the body via the aorta.

Blood Vessel Structure

Veins and arteries have three layers that provide strength, elasticity, and regulation of blood flow.

Capillary Types

Capillaries are classified based on their permeability and structure.

Cardiac Cycle and EKG

The cardiac cycle describes the sequence of events in one heartbeat, which can be tracked using an electrocardiogram (EKG).

• P wave: Atrial depolarization.

• QRS complex: Ventricular depolarization.

• T wave: Ventricular repolarization.

Each event corresponds to specific phases of contraction and relaxation in the heart chambers.

Cardiac Output and Blood Pressure

Cardiac output is the volume of blood pumped by the heart per minute.

• Formula:

• Stroke Volume (SV): Amount of blood ejected per beat.

• Heart Rate (HR): Number of beats per minute.

Blood pressure is regulated by cardiac output, vessel diameter, and blood volume.

• Pulse Pressure:

• Mean Arterial Pressure (MAP):

Regulation of Heart Rate and Contractility

Heart rate and contractility are regulated by neural centers and chemical agents.

• Cardioacceleratory center: Increases heart rate.

• Cardioinhibitory center: Decreases heart rate.

• Chronotropic agents: Affect heart rate.

• Inotropic agents: Affect contractility.

Shock and Heart Failure

Shock is a state of inadequate tissue perfusion, classified by cause.

Respiratory System

Respiration Types

Respiration involves gas exchange at the lungs and tissues.

• External Respiration: Exchange of gases between alveoli and blood.

• Internal Respiration: Exchange of gases between blood and tissues.

• Ventilation: Movement of air in and out of the lungs.

Anatomy of the Respiratory System

The respiratory system is divided into upper and lower airways, each with specific structures.

• Upper Airway: Pharynx, nasopharynx, larynx, glottis, thyroid cartilage, vestibular folds, vallecula, cricoid cartilage.

• Lower Airway: Trachea, carina, bronchi (main, lobar, segmental), bronchioles, alveoli.

Lung Lobes and Pleura

Each lung is divided into lobes and surrounded by pleural membranes.

• Right lung: 3 lobes.

• Left lung: 2 lobes.

• Pleura: Parietal (outer) and visceral (inner) layers.

Ventilation and Pressure

Ventilation is driven by pressure differences between the atmosphere and the lungs.

• Inspiration: Diaphragm contracts, thoracic volume increases, pressure decreases, air flows in.

• Expiration: Diaphragm relaxes, thoracic volume decreases, pressure increases, air flows out.

Lung Volumes and Capacities

Lung volumes and capacities are important for assessing respiratory function.

• Tidal Volume (TV): Volume of air inhaled/exhaled per breath.

• Total Lung Capacity (TLC): Maximum volume of air in lungs after maximal inspiration.

• Residual Volume (RV): Air remaining after maximal expiration.

• Vital Capacity (VC): Maximum air exhaled after maximal inspiration.

• Functional Residual Capacity (FRC): Air remaining after normal expiration.

Gas Exchange and Transport

Oxygen and carbon dioxide are exchanged in the alveoli and transported in the blood.

• Oxygen: Mostly bound to hemoglobin; small amount dissolved in plasma.

• Carbon Dioxide: Transported as bicarbonate (), dissolved in plasma, or bound to hemoglobin.

Hemoglobin Dissociation Curve: Shows the relationship between oxygen saturation and partial pressure of oxygen.

Acid-Base Balance

Respiratory and metabolic processes affect blood pH.

• Respiratory Acidosis: Caused by hypoventilation, leading to increased .

• Respiratory Alkalosis: Caused by hyperventilation, leading to decreased .

• Metabolic Acidosis/Alkalosis: Caused by changes in metabolic acids or bases.

Neural Control of Respiration

Respiratory drive is regulated by centers in the brainstem.

• Pons: Pneumotaxic center regulates rate and pattern.

• Medulla Oblongata: DRG and VRG control rhythm and depth.

Common Respiratory Pathologies

Several conditions affect respiratory function.

• Atelectasis: Collapse of lung tissue.

• Pneumothorax: Air in pleural space causing lung collapse.

• Hemothorax: Blood in pleural space.

• Asthma: Chronic inflammation and constriction of airways, triggered by allergens, exercise, or irritants.

• Lung Cancer: Types include adenocarcinoma, squamous cell carcinoma, and small cell carcinoma. Can cause ionic and hormonal imbalances (e.g., ACTH, ADH secretion).

Gas Laws and Respiratory Physiology

Gas exchange is governed by physical laws.

• Dalton's Law: Total pressure of a mixture of gases equals the sum of the partial pressures of each gas.

Fetal Circulatory Adaptations

Fetal circulation includes unique structures that bypass the lungs.

• Ductus Venosus: Shunts blood from umbilical vein to inferior vena cava.

• Foramen Ovale: Opening between right and left atria.

• Ductus Arteriosus: Connects pulmonary artery to aorta.

*Additional info: Some explanations and definitions have been expanded for clarity and completeness based on standard Anatomy & Physiology curriculum.*