Blood Vessels, Lymphatic & Immune Systems, and Respiratory System: Study Notes

Blood Vessels & Hemodynamics

Vocabulary and Key Concepts

• Arteries: Blood vessels that carry blood away from the heart; thick-walled and able to withstand high pressure.

• Veins: Blood vessels that return blood to the heart; thin-walled, contain valves to prevent backflow, and act as capacitance vessels (expand easily to hold blood).

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

• Resistance vessels: Arteries that regulate blood pressure by resisting flow.

• Capacitance vessels: Veins that accommodate varying blood volumes.

• Baroreceptors: Pressure sensors in the aortic arch and carotid arteries; regulate heart rate and blood pressure.

• Chemoreceptors: Receptors sensitive to changes in pH, CO2, and O2 levels.

• Portal system: Blood passes through two consecutive capillary beds before returning to the heart (e.g., hepatic portal system).

• Arteriovenous shunt: Direct connection between an artery and a vein, bypassing capillaries.

• Anastomosis: Alternate routes for blood flow; can be arterial or venous.

• Aneurysm: Weak point in a vessel wall that may rupture.

• Hemodynamics: Study of blood flow, pressure, and resistance.

• Blood flow: Volume of blood moving through tissue per minute (mL/min).

• Perfusion: Blood flow per given mass of tissue (mL/min/g).

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

• Systolic pressure: Pressure during ventricular contraction.

• Diastolic pressure: Pressure during ventricular relaxation.

• Peripheral resistance: Friction between blood and vessel walls; affects BP.

• Vasomotion: Change in vessel radius (vasoconstriction or vasodilation).

• Reactive hyperemia: Increased blood flow after temporary blockage.

• Angiogenesis: Formation of new blood vessels.

• Baroreflex & Chemoreflex: Neural feedback mechanisms for BP and blood chemistry regulation.

• RAAS (Renin-Angiotensin-Aldosterone System): Hormonal system that increases blood volume and BP.

• ADH (Antidiuretic Hormone): Increases water retention and BP.

• Atrial natriuretic factor: Promotes sodium and water excretion, lowering BP.

• Capillary filtration: Fluid movement out of capillaries at arterial end.

• Capillary reabsorption: Fluid movement into capillaries at venous end.

• Skeletal muscle pump & Thoracic pump: Mechanisms aiding venous return.

• Shock: Inadequate tissue perfusion; types include cardiogenic, hypovolemic, and venous pooling.

• TIA (Transient Ischemic Attack): Temporary neurological deficit due to reduced blood flow.

• CVA (Cerebrovascular Accident): Stroke caused by brain infarction.

• Edema: Excess fluid in tissue spaces.

Blood Vessel Structure & Function

• Arteries withstand high pressure from ventricular contraction and retain their shape even when empty.

• Veins operate under lower pressure and rely on valves, skeletal muscle pump, and thoracic pump to return blood to the heart.

• Capillaries are the primary sites of exchange; at rest, most skeletal muscle capillaries are closed.

Blood Pressure and Flow

• Blood flow is directly proportional to the pressure difference and inversely proportional to resistance.

• BP decreases as blood moves from the aorta to the vena cavae.

• BP is determined by:

  1. Cardiac output

  2. Blood volume (regulated by kidneys)

  3. Peripheral resistance (affected by blood viscosity, vessel length, and especially vessel radius)

• Smaller vessel radius increases resistance and BP.

Regulation of Blood Pressure

• Local control: Vasodilators like histamine and prostaglandins; reactive hyperemia.

• Neural control: Baroreceptors (respond to stretch) and chemoreceptors (respond to CO2, O2, pH).

• Hormonal control: RAAS and ADH increase BP; atrial natriuretic factor lowers BP; epinephrine causes vasoconstriction.

Capillary Exchange

• Diffusion: Main mechanism for exchange of gases and nutrients.

• Transcytosis: Transport of larger molecules (e.g., fatty acids, albumin, insulin).

• Filtration: Fluid moves out at arterial end; Reabsorption: Fluid moves in at venous end.

Shock and Clinical Correlations

• Cardiogenic shock: Heart pump failure.

• Hypovolemic shock: Blood loss or dehydration.

• Venous pooling shock: Prolonged standing or widespread vasodilation.

• TIA: Temporary neurological symptoms; warning sign.

• CVA: Permanent brain infarction (stroke).

• Edema: Caused by high BP, low albumin, or impaired reabsorption.

Lymphatic & Immune Systems

Vocabulary and Key Concepts

• Lymph: Clear fluid similar to plasma but lower in protein.

• Lacteals: Lymphatic capillaries in the intestine that absorb dietary fats.

• Chyle: Milky lymph containing absorbed fats.

• Cisterna chyli: Dilated sac at the lower end of the thoracic duct.

• Lymphedema: Swelling due to blocked lymphatic drainage.

• Red bone marrow: Site of blood cell formation (hematopoiesis).

• Thymus: Site of T-cell maturation.

• Lymph nodes: Filter lymph and activate B and T cells.

• Lymphadenitis: Inflammation of lymph nodes.

• Spleen: Filters blood, recycles old RBCs, and stores immune cells.

• Innate immunity: Nonspecific, immediate defense mechanisms.

• Adaptive immunity: Specific, memory-based defense mechanisms.

• Neutrophils: Phagocytic white blood cells with a respiratory burst.

• Macrophages: Phagocytes derived from monocytes.

• NK cells: Natural killer cells that destroy infected or cancerous cells.

• Complement system: Group of proteins that enhance immune responses.

• Membrane attack complex: Complement proteins that lyse pathogens.

• Fever: Elevated body temperature due to pyrogens.

• Antigen: Substance that triggers an immune response.

• Epitope: Specific part of an antigen recognized by the immune system.

• Antibody classes: IgG, IgA, IgM, IgE, IgD.

• Cytotoxic T cells: Kill infected cells directly.

• Helper T cells: Stimulate and coordinate immune responses.

• Memory T cells: Provide long-term immunity.

• Anaphylactic shock: Severe allergic reaction.

• Autoimmune disease: Immune system attacks self-tissues.

• AIDS: HIV infection that destroys helper T cells.

Lymphatic System Functions

• Immunity: Houses and transports immune cells.

• Lipid absorption: Absorbs dietary fats via lacteals.

• Fluid recovery: Returns excess interstitial fluid to the bloodstream.

Lymph Flow

• Pathway: Capillaries → vessels → trunks → ducts → subclavian veins.

• Right lymphatic duct drains right upper body; thoracic duct drains the rest.

Innate Immunity

• First line: Skin and mucous membranes (physical and chemical barriers).

• Second line: Phagocytes, NK cells, complement proteins, fever, and inflammation (characterized by pain, redness, heat, swelling, and loss of function).

Adaptive Immunity

• Humoral immunity: B cells produce antibodies; primary response is slow, secondary response is rapid due to memory cells.

• Cellular immunity: Cytotoxic T cells kill infected cells; helper T cells coordinate the response; memory T cells provide long-term protection.

Respiratory System

Vocabulary and Key Concepts

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

• Cellular respiration: Production of ATP using oxygen.

• Nasal conchae: Structures that warm and humidify incoming air.

• Olfactory mucosa: Detects odors.

• Respiratory mucosa: Traps debris and pathogens.

• Epiglottis: Prevents food from entering the airway during swallowing.

• Glottis: Opening to the trachea.

• Mucociliary escalator: Cilia move mucus upward to clear debris.

• Alveoli: Tiny sacs for gas exchange.

• Surfactant: Reduces surface tension in alveoli, preventing collapse.

• Pleurae: Visceral and parietal membranes surrounding the lungs.

• Pneumothorax: Air in the pleural cavity, causing lung collapse.

• Atelectasis: Collapse of lung tissue.

• Boyle’s law: Pressure is inversely proportional to volume: $P_1V_1 = P_2V_2$

• Oxyhemoglobin: Hemoglobin bound to oxygen.

• Carbaminohemoglobin: Hemoglobin bound to carbon dioxide.

• Respiratory acidosis: High CO2, low pH.

• Respiratory alkalosis: Low CO2, high pH.

• Hypoxia: Oxygen deficiency in tissues.

Airway and Gas Exchange

• Air pathway: Nose → pharynx → larynx → trachea → bronchi → bronchioles → alveoli.

• Gas exchange: O2 diffuses into blood; CO2 diffuses into alveoli.

CO2 Transport

• 90% as bicarbonate ion ($CO_2 + H_2O \rightarrow H_2CO_3 \rightarrow HCO_3^- + H^+$)

• 5% bound to hemoglobin (carbaminohemoglobin)

• 5% dissolved in plasma

Acid-Base Balance

• Acidosis: High CO2 leads to high H+ (low pH); triggers hyperventilation.

• Alkalosis: Low CO2 leads to low H+ (high pH); triggers hypoventilation.

Types of Hypoxia

• Ischemic hypoxia: Inadequate blood flow.

• Anemic hypoxia: Low hemoglobin or RBCs.

• Histotoxic hypoxia: Tissues unable to use O2.

• Hypoxemic hypoxia: Low arterial O2 pressure.

Example Table: Blood Vessel Types and Functions

Vessel Type	Structure	Function
Artery	Thick, muscular, elastic walls	Carry blood away from heart; withstand high pressure
Vein	Thin walls, valves present	Return blood to heart; act as blood reservoirs
Capillary	Single layer of endothelium	Exchange of gases, nutrients, and wastes

Example Table: Innate vs. Adaptive Immunity

Feature	Innate Immunity	Adaptive Immunity
Specificity	Non-specific	Specific (antigen-dependent)
Memory	None	Yes
Response Time	Immediate	Delayed (primary), rapid (secondary)
Main Components	Barriers, phagocytes, NK cells, complement	B cells, T cells, antibodies

Example Table: Types of Shock

Type	Cause	Example
Cardiogenic	Heart pump failure	Myocardial infarction
Hypovolemic	Blood volume loss	Hemorrhage, dehydration
Venous pooling	Widespread vasodilation	Prolonged standing, neurogenic shock

Key Equations

• Boyle’s Law: $P_1V_1 = P_2V_2$

• Blood Flow: $F = \frac{\Delta P}{R}$ (Flow equals pressure difference divided by resistance)

• CO2 Transport (Bicarbonate Reaction): $CO_2 + H_2O \leftrightarrow H_2CO_3 \leftrightarrow HCO_3^- + H^+$

Additional info:

• Some definitions and explanations have been expanded for clarity and completeness.

• Tables have been constructed to summarize and compare key concepts.