Study Guide: Blood, Heart, and Blood Vessels (Chapters 17–19)

Chapter 17 – Blood

Formed Elements of Blood

The formed elements of blood include erythrocytes (red blood cells), leukocytes (white blood cells), and platelets (thrombocytes). Each type has distinct functions essential for homeostasis and defense.

• Erythrocytes: Transport oxygen and carbon dioxide.

• Leukocytes: Defend against pathogens; include granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (lymphocytes, monocytes).

• Platelets: Cell fragments involved in blood clotting.

Normal lifespan of erythrocytes: Approximately 120 days due to the lack of a nucleus and most organelles, which limits repair mechanisms.

Thrombocytopenia: A decreased number of platelets, leading to increased bleeding risk.

Plasma Components

Plasma is the liquid matrix of blood, containing water, proteins, nutrients, hormones, and waste products.

• Albumin: Maintains osmotic pressure and transports substances.

• Globulins: Include antibodies for immune defense.

• Fibrinogen: Essential for blood clotting; converted to fibrin during coagulation.

Blood Cell Formation and Disorders

• Erythropoiesis: Formation of red blood cells, stimulated by erythropoietin (EPO) from the kidneys in response to hypoxia.

• Anemia: Reduced oxygen-carrying capacity; causes include iron deficiency, vitamin B12 deficiency, and chronic disease.

• Polycythemia: Increased RBC count, which can thicken blood and increase clot risk.

• Leukopenia: Low WBC count; leukocytosis: high WBC count.

Hemostasis and Coagulation

Hemostasis is the process that stops bleeding and involves three main steps:

1. Vascular spasm: Vasoconstriction to reduce blood flow.

2. Platelet plug formation: Platelets adhere to damaged endothelium and aggregate.

3. Coagulation: Fibrinogen is converted to fibrin, forming a stable clot.

Key conversions:

• Prothrombin is converted to thrombin.

• Fibrinogen is converted to fibrin.

Blood Typing and Transfusion

• Antigens: Surface proteins on RBCs that determine blood type (A, B, AB, O).

• Antibodies: Proteins in plasma that react against incompatible antigens.

• Universal donor: Type O (no antigens); universal recipient: Type AB (no antibodies).

• Rh factor: Rh+ has antigen; Rh- lacks antigen. Hemolytic disease of the newborn can occur if an Rh- mother carries an Rh+ fetus.

Chapter 18 – Heart

Heart Anatomy and Landmarks

The heart is a muscular organ located in the mediastinum, resting on the diaphragm, with the apex pointing left and inferiorly.

• Chambers: 2 atria (receive blood), 2 ventricles (pump blood).

• Valves: Ensure unidirectional blood flow: tricuspid (right AV), bicuspid/mitral (left AV), pulmonary semilunar, aortic semilunar.

• Coronary sulcus: Groove marking the border between atria and ventricles.

Heart Valves and Circulation

• AV valves: Close at the beginning of ventricular systole to prevent backflow into atria.

• Semilunar valves: Close at the beginning of ventricular diastole to prevent backflow into ventricles.

• Chordae tendineae and papillary muscles: Prevent AV valve prolapse during contraction.

Electrical Conduction System

• Sinoatrial (SA) node: Pacemaker of the heart, initiates electrical impulses.

• Atrioventricular (AV) node, bundle of His, bundle branches, Purkinje fibers: Conduct impulses through the heart.

Electrocardiogram (ECG/EKG): Records electrical activity of the heart.

• P wave: Atrial depolarization.

• QRS complex: Ventricular depolarization.

• T wave: Ventricular repolarization.

Cardiac Cycle and Output

• Cardiac cycle: Sequence of events in one heartbeat, including systole (contraction) and diastole (relaxation).

• Stroke volume (SV): Volume of blood pumped per beat.

• Heart rate (HR): Beats per minute.

• Cardiac output (CO): Total blood pumped per minute.

Formula:

$CO = SV \times HR$

End diastolic volume (EDV): Blood in ventricle at end of filling; end systolic volume (ESV): blood remaining after contraction.

Heart Sounds and Murmurs

• First heart sound (S1): Closure of AV valves.

• Second heart sound (S2): Closure of semilunar valves.

• Murmurs: Abnormal heart sounds due to valve dysfunction.

Chapter 19 – Blood Vessels

Types and Structure of Blood Vessels

• Arteries: Carry blood away from the heart; thick muscular walls.

• Veins: Return blood to the heart; thinner walls, valves prevent backflow.

• Capillaries: Microscopic vessels for exchange of gases, nutrients, and wastes.

All blood vessels (except capillaries) have three tunics:

• Tunica intima: Inner endothelial layer.

• Tunica media: Smooth muscle and elastic fibers.

• Tunica adventitia (externa): Outer connective tissue.

Major Circulatory Pathways

• Systemic circulation: Oxygenated blood from left heart to body, returns deoxygenated blood to right heart.

• Pulmonary circulation: Deoxygenated blood from right heart to lungs, returns oxygenated blood to left heart.

• Hepatic portal circulation: Blood from digestive organs passes through the liver before returning to the heart.

Blood Pressure and Regulation

• Blood pressure (BP): Force of blood against vessel walls.

• Systolic BP: During ventricular contraction; diastolic BP: during relaxation.

• Hypertension: BP above 130/90 mmHg; cause often unknown (essential hypertension).

• Factors affecting BP: Cardiac output, peripheral resistance, blood volume, viscosity.

Formula:

$BP = CO \times PR$

Where PR is peripheral resistance.

Regulation of Heart Rate and Blood Pressure

• Sympathetic nervous system: Increases HR and contractility.

• Parasympathetic nervous system: Decreases HR via the vagus nerve.

• Hormones: ADH, epinephrine, angiotensin II increase BP; ANP decreases BP.

Table: Types of Blood Vessels and Their Features

Vessel Type	Main Function	Wall Structure	Examples
Elastic artery	Conduct blood from heart	Thick tunica media, elastic fibers	Aorta, pulmonary trunk
Muscular artery	Distribute blood to organs	More smooth muscle, less elastic	Brachial, femoral arteries
Arteriole	Regulate flow into capillaries	Thin wall, smooth muscle	Smallest arteries
Capillary	Exchange of substances	Single endothelial layer	Capillary beds
Venule	Collect blood from capillaries	Thin wall	Smallest veins
Vein	Return blood to heart	Thin tunica media, valves	Vena cava, jugular vein

Additional info:

• Some explanations and examples were expanded for clarity and completeness.

• Table content was inferred and organized based on standard textbook knowledge.