Cardiovascular, Blood, and Lymphatic Systems: Study Notes (Chapters 17, 18, 19, 20)

Chapter 18: The Cardiovascular System

Coverings of the Heart – Names and Functions of Each Layer

• Pericardium: Double-layered sac that protects and anchors the heart.

  • Fibrous pericardium: Outermost, tough connective tissue; prevents overfilling and anchors heart.

  • Serous pericardium: Two layers with fluid in between to reduce friction.

    • Parietal layer: Lines internal surface of fibrous pericardium.

    • Visceral layer (epicardium): Covers external heart surface.

    • Pericardial cavity: Fluid-filled space between parietal and visceral layers.

Layers of the Heart – Names and Functions of Each Layer

• Epicardium: Outer surface; protective layer.

• Myocardium: Middle, muscular layer; responsible for contraction and pumping action.

• Endocardium: Inner lining; smooth, reduces friction for blood flow.

Chambers of the Heart

• Four chambers: two atria (upper), two ventricles (lower).

• Atria: Receive blood.

  • Right atrium: Receives blood from systemic veins (superior/inferior vena cava, coronary sinus).

  • Left atrium: Receives blood from pulmonary veins (oxygenated blood from lungs).

• Ventricles: Pump blood out of the heart.

  • Right ventricle: Pumps blood to pulmonary trunk (lungs).

  • Left ventricle: Pumps blood to aorta (systemic circulation).

Valves of the Heart

• Ensure one-way blood flow; prevent backflow.

• Atrioventricular (AV) valves: Between atria and ventricles.

  • Tricuspid valve: Right side.

  • Bicuspid (mitral) valve: Left side.

• Semilunar valves: Between ventricles and arteries.

  • Pulmonary valve: Right ventricle → pulmonary trunk.

  • Aortic valve: Left ventricle → aorta.

Pathway of Blood Through the Heart

• Pulmonary Circuit: Right side of heart → lungs → left side of heart (oxygenates blood).

• Systemic Circuit: Left side of heart → body tissues → right side of heart (delivers oxygen).

Anatomy of Cardiac Muscle

• Intercalated discs: Connect cells, allow for synchronized contraction.

• Desmosomes: Hold cells together.

• Gap junctions: Allow ions to flow between cells.

Electrical Events of the Heart

• Autorhythmic cells: Self-depolarize, set the pace of the heart.

• Sequence of excitation:

  • SA node: Pacemaker; initiates impulse.

  • AV node: Delays signal to allow atria to contract before ventricles.

  • Bundle of His: Conducts impulse into interventricular septum.

  • Bundle branches: Carry impulse through septum.

  • Purkinje fibers: Spread impulse to ventricular muscle.

Electrocardiography (ECG/EKG)

• P wave: Atrial depolarization.

• QRS complex: Ventricular depolarization (atrial repolarization hidden).

• T wave: Ventricular repolarization.

Heart Sounds

• "Lub" (S1): AV valves close.

• "Dub" (S2): Semilunar valves close.

Cardiac Cycle

• Systole: Contraction phase.

• Diastole: Relaxation phase.

• Four phases, each defined by valve status and pressure changes:

  1. Ventricular filling: AV valves open, semilunar valves closed. Blood flows from atria to ventricles.

  2. Isovolumetric contraction: All valves closed; ventricles contract, pressure rises.

  3. Ventricular ejection: Semilunar valves open, blood ejected into arteries.

  4. Isovolumetric relaxation: All valves closed; ventricles relax, pressure drops.

Chapter 19: Blood Vessels

Structure of Blood Vessels – Three Layers (Tunics)

• Tunica intima: Innermost; endothelium for smooth blood flow.

• Tunica media: Middle; smooth muscle, controls vessel diameter.

• Tunica externa: Outermost; connective tissue, protects and anchors vessel.

Types of Arteries

• Elastic arteries: Largest; stretch and recoil (e.g., aorta).

• Muscular arteries: Distribute blood to organs; more smooth muscle.

• Arterioles: Smallest; control flow into capillaries.

Capillaries

• Exchange gases, nutrients, wastes between blood and tissues.

• Continuous capillaries: Least permeable; most common (e.g., skin, muscle).

• Fenestrated capillaries: Have pores; found in kidneys, intestines.

• Sinusoidal capillaries: Most permeable; found in liver, bone marrow.

Venous System

• Veins: Carry blood toward the heart; have valves to prevent backflow.

• Venules: Collect blood from capillaries.

Physiology of Circulation

• Blood pressure: Force exerted by blood on vessel walls.

• Resistance: Opposition to flow; affected by viscosity, vessel length, and diameter.

• Arterial blood pressure: Systolic (during contraction) and diastolic (during relaxation).

• Capillary blood pressure: Low to protect capillaries.

• Venous blood pressure: Very low; aided by skeletal muscle pump, respiratory pump, and valves.

Control of Blood Pressure

• Short-term regulation: Neural and hormonal (baroreceptors, hormones).

• Long-term regulation: Renal control (kidneys adjust blood volume).

• Indirect renal mechanism: Renin-angiotensin-aldosterone system increases BP.

Chapter 17: Blood

Functions of Blood

• Transports oxygen, nutrients, hormones, and wastes.

• Regulates temperature, pH, and fluid volume.

• Protects through clotting and immune defense.

Composition of Blood

• Plasma: 90% water, proteins (albumin, globulins, fibrinogen), nutrients, ions, gases.

• Formed elements: RBCs, WBCs, platelets.

  • Erythrocytes (RBCs): Carry oxygen and some CO2.

    • Structure: Biconcave, no nucleus, filled with hemoglobin.

    • Hemoglobin: Protein that binds oxygen.

    • Production: Stimulated by erythropoietin (EPO) from kidneys.

  • Leukocytes (WBCs): Defend against infection and disease.

  • Platelets: Cell fragments; function in clotting.

Chapter 20: Lymphatic System

Functions of the Lymphatic System

• Returns excess fluid from tissues to blood.

• Absorbs fats from digestive tract.

• Provides immune defense.

Lymphatic Vessels

• Capillaries collect fluid from tissues (lymph).

• Lymph is transported by skeletal muscle, breathing, and valves (no pump).

Lymphoid Cells

• B cells: Produce antibodies.

• T cells: Attack infected or abnormal cells.

Lymphoid Organs

• Lymph nodes: Filter lymph, remove debris, activate immune response.

• Spleen: Filters blood, removes old RBCs, stores platelets, activates immune cells.

• Thymus: Site of T cell maturation; most active in childhood.

• Mucosa-associated lymphoid tissue (MALT): Includes tonsils, Peyer's patches, appendix; protects mucous membranes from pathogens.

Blood Clotting (Hemostasis)

• Three steps: vascular spasm, platelet plug formation, coagulation.

• Platelets stick to injury site; fibrin mesh seals break.

Key Table: Comparison of Blood Vessel Types

Vessel Type	Main Function	Structure	Location Example
Elastic Artery	Conduct blood from heart	Thick tunica media, elastic fibers	Aorta
Muscular Artery	Distribute blood to organs	More smooth muscle	Renal artery
Arteriole	Regulate flow into capillaries	Small diameter, thin walls	Precapillary arteriole
Capillary	Exchange of substances	Single endothelial layer	Systemic capillary bed
Venule	Collect blood from capillaries	Thin walls	Postcapillary venule
Vein	Return blood to heart	Thinner walls, valves	Superior vena cava

Key Equations

• Blood Pressure Equation:

  • $\text{Blood Pressure} = \text{Cardiac Output} \times \text{Peripheral Resistance}$

• Cardiac Output Equation:

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