Cardiovascular, Lymphatic, Respiratory, and Endocrine Systems: Study Guide for Anatomy & Physiology

Cardiovascular System

Structural and Functional Differences Between Atria and Ventricles

The heart is divided into four chambers: two atria and two ventricles. Each chamber has distinct structural and functional roles in cardiac physiology.

• Atria: Thin-walled chambers that receive blood returning to the heart. The right atrium receives oxygen-poor blood from the body, while the left atrium receives oxygen-rich blood from the lungs.

• Ventricles: Thick-walled chambers responsible for pumping blood out of the heart. The right ventricle pumps blood to the lungs (pulmonary circuit), and the left ventricle pumps blood to the systemic circuit (body).

• Functional Difference: Ventricles generate higher pressure to propel blood, especially the left ventricle, which must overcome systemic resistance.

• Structural Difference: The left ventricle has a thicker myocardium compared to the right ventricle due to its greater workload.

Heart as a Double Pump

The heart functions as a double pump, separating pulmonary and systemic circulation. This separation is crucial for efficient oxygenation and distribution of blood.

• Pulmonary Circuit: Right side of the heart pumps oxygen-poor blood to the lungs.

• Systemic Circuit: Left side of the heart pumps oxygen-rich blood to the body.

• Significance: Prevents mixing of oxygen-rich and oxygen-poor blood, ensuring tissues receive adequately oxygenated blood.

Path of Blood Through the Heart

Blood flows through the heart in a specific sequence, passing through valves and changing oxygenation status.

1. Oxygen-poor blood enters the right atrium via the superior and inferior vena cava.

2. Passes through the tricuspid valve into the right ventricle.

3. Pumped through the pulmonary valve into the pulmonary arteries to the lungs (becomes oxygen-rich).

4. Oxygen-rich blood returns via pulmonary veins to the left atrium.

5. Passes through the bicuspid (mitral) valve into the left ventricle.

6. Pumped through the aortic valve into the aorta and systemic circulation.

Oxygen Status: Right side handles oxygen-poor blood; left side handles oxygen-rich blood.

Cardiac Action Potentials

Pacemaker Cell Action Potential

Pacemaker cells in the sinoatrial (SA) node generate spontaneous action potentials, initiating the heartbeat.

• Phase 4 (Pacemaker Potential): Slow depolarization due to Na+ influx.

• Phase 0 (Depolarization): Rapid Ca2+ influx.

• Phase 3 (Repolarization): K+ efflux restores resting potential.

Contractile Cell Action Potential

Contractile cells have a distinct action potential with a plateau phase.

• Phase 0: Rapid Na+ influx (depolarization).

• Phase 1: Brief K+ efflux (initial repolarization).

• Phase 2: Ca2+ influx balances K+ efflux (plateau phase).

• Phase 3: K+ efflux (repolarization).

• Phase 4: Resting membrane potential.

Importance of Plateau: Prevents tetanus, ensures proper contraction and relaxation.

Cardiac Conduction System

The cardiac conduction system coordinates the heartbeat.

• Sinoatrial (SA) Node: Primary pacemaker.

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

• AV Bundle (Bundle of His): Conducts impulse to ventricles.

• Bundle Branches: Carry impulse through interventricular septum.

• Purkinje Fibers: Distribute impulse to ventricular myocardium.

Heart Valves and Pressure Changes

Opening and closing of heart valves are governed by pressure differences between chambers.

• AV Valves: Open when atrial pressure exceeds ventricular pressure; close during ventricular contraction.

• Semilunar Valves: Open when ventricular pressure exceeds arterial pressure; close as ventricles relax.

Stroke Volume and Cardiac Output

Stroke volume is the amount of blood ejected by a ventricle per beat; cardiac output is the total volume pumped per minute.

• Factors Influencing Stroke Volume: Preload, contractility, afterload.

• Cardiac Output Formula:

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

Blood Vessels and Circulation

Structure of Arteries, Veins, Arterioles, and Venules

Blood vessels are classified by structure and function.

• Arteries: Thick, elastic walls; carry blood away from heart.

• Veins: Thinner walls, larger lumen; carry blood toward heart, contain valves.

• Arterioles: Small arteries; regulate blood flow to capillaries.

• Venules: Small veins; collect blood from capillaries.

Factors Influencing Blood Flow, Pressure, and Resistance

Blood flow is determined by vessel diameter, blood viscosity, and vessel length.

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

• Peripheral Resistance: Opposition to flow; increases with smaller diameter, higher viscosity, longer vessels.

• Relationship: Blood flow is inversely proportional to resistance.

$\text{Blood Flow} = \frac{\text{Pressure Difference}}{\text{Resistance}}$

Vessel Diameter, Cross-Sectional Area, Blood Pressure, and Velocity

Changes in vessel diameter and cross-sectional area affect blood pressure and velocity.

• Smaller diameter: Higher resistance, lower flow.

• Greater cross-sectional area (capillaries): Lower velocity.

Blood Pressure Changes in Circulation

• Arteries: Highest pressure.

• Capillaries: Moderate pressure, slow flow.

• Veins: Lowest pressure.

Regulation of Blood Pressure

• Local Factors: Autoregulation by tissues.

• Hormonal Factors: Epinephrine, angiotensin II, ADH.

• Neural Factors: Baroreceptor reflex, sympathetic/parasympathetic input.

Net Filtration Pressure Across Capillary Wall

Net filtration pressure determines movement of fluid across capillary walls.

$\text{NFP} = (\text{Capillary Hydrostatic Pressure} + \text{Interstitial Fluid Colloid Osmotic Pressure}) - (\text{Capillary Colloid Osmotic Pressure} + \text{Interstitial Fluid Hydrostatic Pressure})$

Blood Composition

Major Components of Blood

• Plasma: Liquid matrix; contains water, proteins, nutrients, hormones.

• Formed Elements: Erythrocytes (RBCs), leukocytes (WBCs), platelets.

Plasma Composition and Proteins

• Albumin: Maintains osmotic pressure; produced in liver.

• Globulins: Transport, immune functions; produced in liver and lymphoid tissue.

• Fibrinogen: Clotting; produced in liver.

Erythrocytes (Red Blood Cells)

• Structure: Biconcave, anucleate.

• Function: Transport oxygen (via hemoglobin), some CO2.

Leukocytes (White Blood Cells)

• Neutrophils: Phagocytosis of bacteria.

• Lymphocytes: Immune response (B and T cells).

• Monocytes: Phagocytosis; become macrophages.

• Eosinophils: Combat parasites, allergies.

• Basophils: Release histamine, inflammation.

Hemostasis

• Vascular Phase: Vasoconstriction.

• Platelet Plug Formation: Platelets adhere and aggregate.

• Coagulation: Fibrin forms clot.

Blood Groups and Antigens

• Surface Antigens: Determine blood type (A, B, Rh).

• ABO System: Type A (A antigen), Type B (B antigen), Type AB (A and B antigens), Type O (no antigens).

• Rh System: Rh+ (D antigen present), Rh- (D antigen absent).

Antigen and Antibody Table

Blood Type	Antigen	Antibody
A	A	Anti-B
B	B	Anti-A
AB	A, B	None
O	None	Anti-A, Anti-B
Rh+	D	None
Rh-	None	Anti-D (if exposed)

Development of Antibodies

• Anti-A and Anti-B: Naturally occurring.

• Anti-Rh: Develops only after exposure to Rh antigen.

Blood Type Compatibility and Transfusion Reactions

• Compatible Types: Based on absence of recipient antibodies against donor antigens.

• Transfusion Reaction: Occurs if incompatible blood is transfused; causes agglutination and hemolysis.

Lymphatic and Immune Systems

Lymphoid Organs: Structure and Function

• Lymph Nodes: Filter lymph, house immune cells.

• Spleen: Filters blood, removes old RBCs, immune surveillance.

• Thymus: T cell maturation.

• Tonsils: Protect against pathogens entering via mouth/nose.

Antibody-Mediated vs. Cell-Mediated Immunity

• Antibody-Mediated (Humoral): B cells produce antibodies targeting pathogens.

• Cell-Mediated: T cells directly attack infected or abnormal cells.

Cells and Proteins of the Immune System

• B Lymphocytes: Produce antibodies.

• T Lymphocytes: Helper, cytotoxic, regulatory functions.

• Macrophages: Phagocytosis, antigen presentation.

• Antibodies: Immunoglobulins (IgG, IgA, IgM, IgE, IgD).

Classes of T Lymphocytes

Class	Function
Helper T (CD4+)	Activate B cells and other T cells
Cytotoxic T (CD8+)	Destroy infected cells
Regulatory T	Suppress immune response

Major Classes of Antibodies

Class	Structure	Function
IgG	Monomer	Main antibody in blood, crosses placenta
IgA	Dimer	Found in secretions (mucus, saliva)
IgM	Pentamer	First antibody produced, agglutination
IgE	Monomer	Allergic responses, parasitic infections
IgD	Monomer	B cell receptor

Primary vs. Secondary Immune Response

• Primary: First exposure, slower, less antibody produced.

• Secondary: Subsequent exposure, faster, more robust response due to memory cells.

Respiratory System

Four Respiratory Processes

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

• Pulmonary Gas Exchange: Exchange of gases between alveoli and blood.

• Gas Transport: Movement of gases in blood.

• Tissue Gas Exchange: Exchange of gases between blood and tissues.

Pathway of Air During Inspiration

1. Nasal cavity or mouth

2. Pharynx

3. Larynx

4. Trachea

5. Bronchi

6. Bronchioles

7. Alveoli

Muscles of Respiration

• Inspiratory Muscles: Diaphragm, external intercostals.

• Accessory Muscles of Inspiration: Sternocleidomastoid, scalene.

• Accessory Muscles of Expiration: Internal intercostals, abdominal muscles.

• Effect: Change thoracic cavity volume, affecting pressure and airflow.

Pressure Changes During Breathing

• Atmospheric Pressure: Constant (outside body).

• Intrapulmonary Pressure: Changes with inspiration/expiration.

• Intrapleural Pressure: Always lower than intrapulmonary; prevents lung collapse.

Gas Laws and Exchange

• Dalton's Law: Total pressure is sum of partial pressures of gases.

• Henry's Law: Amount of gas dissolved in liquid is proportional to partial pressure.

Oxygen and Carbon Dioxide Gradients

• O2: Moves from high (alveoli) to low (blood/tissues).

• CO2: Moves from high (tissues/blood) to low (alveoli).

Transport of Gases in Blood

• Oxygen: Bound to hemoglobin, dissolved in plasma.

• Carbon Dioxide: Dissolved in plasma, bound to hemoglobin, as bicarbonate.

$\text{CO}_2 + \text{H}_2\text{O} \rightarrow \text{H}_2\text{CO}_3 \rightarrow \text{H}^+ + \text{HCO}_3^-$

Endocrine System

Major Structures and Functions

• Glands: Pituitary, thyroid, parathyroid, adrenal, pineal, thymus, gonads, pancreas.

• Function: Secrete hormones regulating metabolism, growth, reproduction, homeostasis.

Types of Chemical Signaling

• Endocrine: Hormones travel via blood to distant targets.

• Paracrine: Affect nearby cells.

• Autocrine: Affect same cell that secreted signal.

Chemical Classes of Hormones and Receptors

• Amino Acid-Based: Bind to cell surface receptors.

• Steroid-Based: Bind to intracellular receptors.

Stimuli Controlling Hormone Secretion

• Humoral: Changes in blood levels of ions/nutrients.

• Neural: Nervous system stimulation.

• Hormonal: Other hormones stimulate release.

• Feedback: Negative (inhibits), positive (enhances) secretion.

Pituitary Gland Hormones

• Anterior Pituitary: ACTH, TSH, GH, PRL, FSH, LH (stimulus: releasing hormones from hypothalamus; targets: adrenal cortex, thyroid, liver, mammary glands, gonads).

• Posterior Pituitary: ADH, oxytocin (stimulus: neural; targets: kidneys, uterus, mammary glands).

Thyroid and Parathyroid Hormones

• Thyroid Hormones: Stimulus: TSH; targets: most cells; effects: increase metabolism.

• Parathyroid Hormone: Stimulus: low blood Ca2+; targets: bone, kidneys; effects: increase blood Ca2+.

Adrenal Cortex Hormones

• Mineralocorticoids (Aldosterone): Stimulus: low Na+, high K+; targets: kidneys; effects: increase Na+ reabsorption.

• Glucocorticoids (Cortisol): Stimulus: ACTH; targets: most cells; effects: increase glucose, suppress inflammation.

Adrenal Medulla and Sympathetic Nervous System

• Adrenal Medulla: Releases catecholamines (epinephrine, norepinephrine) in response to sympathetic stimulation.

Hormones of Other Glands

• Pineal: Melatonin; regulates circadian rhythm.

• Thymus: Thymosin; T cell development.

• Gonads: Estrogen, testosterone; reproductive functions.

• Adipose: Leptin; regulates appetite.

• Heart: ANP; lowers blood pressure.

• Kidneys: Erythropoietin; stimulates RBC production.

Insulin and Glucagon Regulation of Blood Glucose

• Insulin: Lowers blood glucose by promoting uptake.

• Glucagon: Raises blood glucose by promoting release from liver.

Example: After a meal, insulin increases; during fasting, glucagon increases.

Additional info: Academic context and definitions were added to expand brief study guide points into full explanations, tables, and formulas.