Anatomy & Physiology Study Notes: Cardiovascular System and Blood

Cardiovascular System

Structures of the Cardiovascular System

The cardiovascular system consists of the heart, blood vessels, and blood. It is responsible for transporting nutrients, gases, hormones, and waste products throughout the body.

• Heart: Muscular organ that pumps blood.

• Blood vessels: Includes arteries, veins, and capillaries.

• Blood: Fluid connective tissue composed of plasma and formed elements.

Functions of Arteries, Veins, and Capillaries

• Arteries: Carry blood away from the heart; usually oxygenated except for pulmonary arteries.

• Veins: Carry blood toward the heart; usually deoxygenated except for pulmonary veins.

• Capillaries: Microscopic vessels where exchange of gases, nutrients, and waste occurs between blood and tissues.

Pericardium

The pericardium is a double-walled sac that surrounds and protects the heart. It consists of the fibrous pericardium and the serous pericardium.

• Fibrous pericardium: Outer layer, provides protection and anchors the heart.

• Serous pericardium: Inner layer, produces serous fluid to reduce friction.

Layers of the Heart Wall

• Epicardium: Outer layer, also known as the visceral pericardium.

• Myocardium: Middle layer, composed of cardiac muscle tissue responsible for contraction.

• Endocardium: Inner layer, lines the heart chambers and valves.

Cardiac Skeleton

The cardiac skeleton is a framework of dense connective tissue that supports the heart valves and provides electrical insulation between the atria and ventricles.

Right and Left Ventricles

• Right ventricle: Pumps deoxygenated blood to the lungs via the pulmonary artery.

• Left ventricle: Pumps oxygenated blood to the body via the aorta.

• Difference: The left ventricle has a thicker wall to generate higher pressure for systemic circulation.

Flow of Blood: Oxygenation and Circuits

Blood flow is divided into two main circuits:

• Systemic circuit: Carries oxygenated blood from the left side of the heart to the body and returns deoxygenated blood to the right side.

• Pulmonary circuit: Carries deoxygenated blood from the right side of the heart to the lungs and returns oxygenated blood to the left side.

Heart Valves and Their Functions

• Atrioventricular (AV) valves: Tricuspid (right) and bicuspid/mitral (left); prevent backflow into atria.

• Semilunar valves: Pulmonary and aortic; prevent backflow into ventricles.

Coronary Circulation and Sinus

• Coronary arteries: Supply oxygenated blood to the heart muscle.

• Coronary sinus: Collects deoxygenated blood from the heart muscle and returns it to the right atrium.

Myocardial Infarction

A myocardial infarction (heart attack) occurs when blood flow to a part of the heart is blocked, causing tissue damage.

• Characteristics: Chest pain, shortness of breath, and possible tissue death.

Conduction System of the Heart

The heart's conduction system coordinates contraction:

• Sinoatrial (SA) node: Pacemaker, initiates heartbeat.

• Atrioventricular (AV) node: Delays impulse before passing to ventricles.

• Bundle of His: Conducts impulse to bundle branches.

• Purkinje fibers: Distribute impulse throughout ventricles.

ECG (Electrocardiogram)

An ECG records the electrical activity of the heart. It consists of several waves:

• P wave: Atrial depolarization.

• QRS complex: Ventricular depolarization.

• T wave: Ventricular repolarization.

Cardiac Cycle

The cardiac cycle is the sequence of events in one heartbeat, including contraction (systole) and relaxation (diastole) of the atria and ventricles.

• Systole: Contraction phase, blood is ejected.

• Diastole: Relaxation phase, chambers fill with blood.

Cardiac Output

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

• Formula:

$\text{Cardiac Output} = \text{Stroke Volume} \times \text{Heart Rate}$

End-Systolic and End-Diastolic Volume

• End-diastolic volume (EDV): Volume of blood in a ventricle at the end of filling (diastole).

• End-systolic volume (ESV): Volume of blood remaining in a ventricle after contraction (systole).

Frank-Starling Principle

The Frank-Starling principle states that the strength of the heart's contraction increases with greater filling (preload).

Blood Types

Blood types are classified based on the presence of antigens on red blood cells.

• ABO system: Types A, B, AB, and O.

• Rh system: Rh-positive (+) and Rh-negative (-).

Blood Type Differences

• Antigen presence: Determines compatibility for transfusions.

• Antibody presence: Determines immune response to foreign blood types.

Difference Between Rh+ and Rh-

• Rh+: Has Rh antigen on red blood cells.

• Rh-: Lacks Rh antigen; can develop antibodies if exposed to Rh+ blood.

White Blood Cells (Leukocytes)

White blood cells are immune cells that protect the body against infection.

• Types: Neutrophils, lymphocytes, monocytes, eosinophils, basophils.

• Functions: Phagocytosis, antibody production, inflammation, and allergic responses.

Lymphocytes

• B cells: Produce antibodies.

• T cells: Destroy infected cells and coordinate immune response.

• Natural killer (NK) cells: Attack abnormal cells.

Platelets

Platelets are cell fragments involved in blood clotting.

• Function: Form plugs in vessel injuries and release clotting factors.

Red Blood Cells (Erythrocytes)

Red blood cells transport oxygen and carbon dioxide.

• Features: Biconcave shape, lack nucleus, contain hemoglobin.

• Markers: ABO and Rh antigens.

Table: Comparison of Blood Vessel Types

Vessel Type	Wall Structure	Function	Pressure
Artery	Thick, muscular	Carry blood away from heart	High
Vein	Thin, less muscular, valves present	Carry blood toward heart	Low
Capillary	Single cell layer	Exchange of substances	Very low

Additional info: Academic context and definitions have been expanded for clarity and completeness.