Practical Review: Blood, Cardiovascular, and Lymphatic Systems

Blood: Components and Clinical Tests

Composition of Blood

Blood is a specialized connective tissue composed of plasma and formed elements. When whole blood is separated, it forms three distinct layers:

• Plasma: The top layer, a straw-colored fluid, makes up about 55% of blood volume and contains water, proteins, electrolytes, and nutrients.

• Buffy coat: The middle thin layer, composed of leukocytes (white blood cells) and platelets.

• Erythrocytes: The bottom layer, consisting of red blood cells, accounts for about 45% of blood volume.

Formed elements are derived from hematopoietic stem cells in the bone marrow.

Characteristics and Functions of Formed Elements

• Erythrocytes (Red Blood Cells): Biconcave, anucleate cells specialized for oxygen transport via hemoglobin.

• Platelets: Small cell fragments involved in blood clotting.

• Leukocytes (White Blood Cells): Immune cells classified as granulocytes or agranulocytes.

Granulocytes:

• Neutrophils: Phagocytic cells, most abundant, respond to infection.

• Eosinophils: Combat parasitic infections and modulate allergic responses.

• Basophils: Release histamine, involved in inflammatory responses.

Agranulocytes:

• Monocytes: Differentiate into macrophages, phagocytize pathogens.

• Lymphocytes: Include B cells (antibody production) and T cells (cell-mediated immunity).

Clinical Blood Tests

Blood Typing System: Blood types are determined by antigens present on erythrocyte surfaces.

• Antigens: A, B, Rh (D) are the main antigens involved.

• Antibodies: Individuals produce antibodies against antigens not present on their own RBCs.

Agglutination is the clumping of cells due to antibody-antigen interaction, used to determine blood types. Types of Anemia:

1. Iron-deficiency anemia

2. Pernicious anemia

3. Hemorrhagic anemia

4. Hemolytic anemia

5. Aplastic anemia

Heart Anatomy and Physiology

Heart Structure and Location

The heart is located in the mediastinum, surrounded by serous membranes (pericardium), and composed of cardiac muscle tissue. The heart wall consists of three layers:

• Epicardium: Outer layer

• Myocardium: Middle, muscular layer

• Endocardium: Inner layer

Heart Chambers, Valves, and Great Vessels

• Chambers: Right and left atria, right and left ventricles

• Valves: Tricuspid, bicuspid (mitral), pulmonary, aortic

• Great vessels: Superior/inferior vena cava, pulmonary arteries/veins, aorta

Blood Flow Direction:

1. Deoxygenated blood enters right atrium → right ventricle → pulmonary arteries → lungs

2. Oxygenated blood returns via pulmonary veins → left atrium → left ventricle → aorta → systemic circulation

Cardiovascular Physiology

Blood Pressure

• Systolic pressure: Pressure during ventricular contraction

• Diastolic pressure: Pressure during ventricular relaxation

Conduction System of the Heart

• Sinoatrial (SA) node: Pacemaker, initiates electrical impulse

• Atrioventricular (AV) node: Delays impulse, allows atrial contraction

• Bundle of His, bundle branches, Purkinje fibers: Distribute impulse to ventricles

Electrocardiogram (EKG)

• P wave: Atrial depolarization

• QRS complex: Ventricular depolarization

• T wave: Ventricular repolarization

Types of Arrhythmias

• Bradycardia: Slow heart rate

• Tachycardia: Fast heart rate

• Atrial fibrillation (A-fib): Irregular atrial rhythm

• Ventricular fibrillation (V-fib): Disorganized ventricular rhythm

Blood Vessels

Types and Structure of Blood Vessels

There are three basic types of blood vessels:

• Arteries: Carry blood away from the heart; thick muscular layer, highly folded endothelium

• Veins: Carry blood toward the heart; smooth endothelium, valves, less smooth muscle

• Capillaries: Site of exchange; simple squamous epithelium

Layers of Vessel Walls:

• Tunica intima: Inner layer

• Tunica media: Middle, muscular layer

• Tunica externa: Outer layer

Great Vessels of Pulmonary and Systemic Circuits

• Pulmonary circuit: Pulmonary arteries and veins

• Systemic circuit: Aorta, vena cavae, and branches

Systemic Vessels: Head and Neck

The head and neck contain major arteries and veins supplying and draining blood.

• Common carotid artery

• Temporal artery

• Occipital artery

• Facial artery

• External and internal jugular veins

Systemic Vessels: Arm

The arm is supplied by branches from the subclavian artery and drained by corresponding veins.

• Arteries: Axillary, brachial, radial, ulnar, palmar arch

• Veins: Dorsal venous network, basilic (medial), cephalic (lateral), axillary, subclavian

Systemic Vessels: Thorax and Abdomen

The thorax and abdomen contain the aorta and its branches, as well as veins associated with organs.

• Aorta: Ascending, arch, descending (thoracic and abdominal)

• Celiac trunk: Supplies upper abdominal viscera

• Common iliac, sacral arteries

• Hepatic, splenic, renal arteries and veins

Systemic Vessels: Leg

The leg is supplied by femoral and tibial arteries and drained by saphenous and other veins.

• Arteries: Femoral, deep femoral, popliteal, anterior and posterior tibial

• Veins: Great and small saphenous, dorsal venous arch

Lymphatic System

Lymphatic Organs and Functions

The lymphatic system is essential for immune defense and fluid balance.

• Lymph nodes: Filter lymph, house immune cells

• Spleen: Filters blood, recycles RBCs, stores platelets

• Thymus gland: Site of T cell maturation

Organization of Lymphatic Vessels

Lymph flows through a hierarchical network:

1. Lymphatic capillaries

2. Lymphatic vessels

3. Lymphatic trunks

4. Lymphatic ducts (right lymphatic duct and thoracic duct)

5. Right and left subclavian veins

Inflammatory Response

The inflammatory response is a protective reaction to injury or infection.

• Pain

• Redness

• Swelling

• Heat

Steps:

1. Release of inflammatory mediators

2. Vasodilation and increased permeability

3. Recruitment of immune cells

4. Resolution and tissue repair

Example: A cut on the skin triggers inflammation, resulting in redness, swelling, heat, and pain as immune cells respond to pathogens.

Additional info: Academic context was added to clarify vessel structure, blood cell function, and lymphatic organization.