LO Vasculature

Innermost vascular layer lined by endothelial cells that interfaces directly with blood plasma

Tunica Intima

Middle vascular layer containing smooth muscle cells and elastic fibers responsible for regulating vessel diameter and vascular tone

Tunica Media

Outermost vascular layer composed of fibrous connective tissue that provides structural strength and anchor support to the vessel

Tunica Externa (Adventitia)

Large vessels containing abundant elastic fibers in the tunica media that stretch during systole to absorb pressure and function as high-pressure conduits

Elastic Arteries

Vessels containing dense smooth muscle layers and fewer elastic fibers that actively contract and relax to direct regional blood flow

Muscular Arteries

Small vessels with thick muscular walls that experience the largest pressure drop in systemic circulation and act as noncompliant resistance vessels controlling tissue flow

Arterioles

Microscopic thin-walled vessels composed of a single endothelial cell layer resting on a basal lamina that act as noncompliant exchange vessels

Capillaries

Thin-walled vessels with minimal smooth muscle and connective tissue that serve as low-pressure collection conduits draining capillary beds

Venules

Thin-walled, highly compliant fibrous vessels with large lumens and unidirectional valves that function as capacitance blood reservoirs to adjust preload

Veins

Capillary exchange route providing direct passage across endothelial cell membranes for lipid-soluble molecules driven by concentration gradients

Simple Diffusion

Water-filled clefts between adjacent endothelial cells permitting small water-soluble solutes like sodium, potassium, glucose, and amino acids to pass

Intercellular Junctions

Oval membrane pores or windows in specialized capillaries that facilitate rapid filtration of water and small solutes

Fenestrations

Active vesicular transport route facilitating the movement of large, exchangeable plasma proteins across the capillary endothelium

Vesicular Transport (Transcytosis)

Fundamental hemodynamic relationship stating that blood flow rate equals the pressure gradient divided by vascular resistance

Pressure Gradient and Flow Equation

Hemodynamic equation stating that bulk flow volume rate equals cross-sectional area multiplied by average flow velocity

Bulk Flow Rate Formula

Physical principle stating that vascular resistance is directly proportional to blood viscosity and vessel length, and inversely proportional to the fourth power of vessel radius

Poiseuille's Law

Primary determinant of vascular resistance where a 2-fold increase in vessel radius causes a 16-fold decrease in resistance and a 16-fold increase in blood flow

Vessel Radius

Internal fluid friction of blood directly proportional to vascular resistance, which increases with polycythemia and decreases with anemia

Blood Viscosity

Laboratory parameter measuring the percentage of total blood volume occupied by erythrocytes, normally 40% to 45%

Hematocrit

Physical parameter directly proportional to vascular resistance that scales linearly as total blood vessel distance increases

Vessel Length

Fluid movement pattern composed of concentric parallel layers moving smoothly straight ahead, with highest velocity in the vessel center and lowest along the vessel wall

Laminar Flow

Disorganized fluid movement occurring across structural obstructions or sharp turns that generates vibrations presenting clinically as audible murmurs

Turbulent Flow

Valvular pathology where narrowing of the valve orifice forces high-velocity ejection, producing severe turbulent flow and a harsh systolic ejection murmur loudest at the right second intercostal space

Aortic Stenosis

Fundamental hemodynamic relationship stating that average perfusion pressure equals Cardiac Output multiplied by Total Peripheral Resistance

Mean Arterial Pressure (MAP) Formula

Volume of blood ejected per beat by the left ventricle, determined by preload, myocardial contractility (inotropy), and afterload

Stroke Volume

Hemodynamic measure of total systemic frictional resistance, calculated as MAP minus CVP divided by CO, multiplied by 80

Systemic Vascular Resistance (SVR/TPR) Formula

Primary determinant of Total Peripheral Resistance because they account for the largest proportion of resistance in the systemic cardiovascular tree

Arteriolar Diameter

Pressure oscillation value calculated as Systolic Blood Pressure minus Diastolic Blood Pressure, which directly reflects Stroke Volume and inversely relates to arterial compliance

Pulse Pressure

Mechanoreceptors sensitive to arterial stretch located in the carotid sinus and aortic arch that modulate short-term blood pressure

Baroreceptors

Carotid sinus mechanoreceptors innervated by the glossopharyngeal nerve (CN IX) that respond dynamically to both increases and decreases in MAP

Carotid Sinus Baroreceptors

Aortic arch mechanoreceptors innervated by the vagus nerve (CN X) that respond primarily to increases in MAP

Aortic Arch Baroreceptors

Medullary reflex response to falling blood pressure involving increased sympathetic and decreased parasympathetic outflow to increase HR, contractility, TPR, and venous return

Baroreceptor Reflex for Decreased MAP

Sensory detectors located in carotid bodies, aortic bodies, and the medulla that respond to decreased PO2, decreased pH, or elevated PCO2 to coordinate vasomotor tone with blood gases

Chemoreceptors

Adrenergic receptors on vascular smooth muscle of arterioles and veins that induce vasoconstriction and venoconstriction upon sympathetic stimulation

Alpha-1 Adrenergic Receptors

Central nervous system adrenergic receptors that provide presynaptic sympathetic inhibition to promote vasodilation

Alpha-2 Adrenergic Receptors

Myocardial, SA node, and AV node adrenergic receptors that increase heart rate (positive chronotropy) and contractility (positive inotropy)

Beta-1 Adrenergic Receptors

Vascular smooth muscle adrenergic receptors located on skeletal muscle arterioles that mediate vasodilation upon stimulation

Beta-2 Adrenergic Receptors

Intrinsic smooth muscle response where increased perfusion pressure stretches arteriolar walls, triggering reflex contraction to keep local blood flow constant

Myogenic Mechanism

Autoregulatory response where accumulating metabolic by-products like adenosine, CO2, H+, and K+ induce local arteriolar vasodilation to drive active hyperemia

Metabolic Mechanism

Renal enzyme secreted by juxtaglomerular cells in response to low arterial pressure, reduced renal perfusion, or low sodium delivery

Renin

Potent peptide hormone produced via pulmonary ACE cleavage of Angiotensin I that acts as a direct vasoconstrictor and stimulates aldosterone release

Angiotensin II

Adrenal cortical hormone that enhances renal tubular sodium and water recovery, expanding blood volume and raising long-term blood pressure

Aldosterone

Hormone released from the posterior pituitary in response to high plasma osmolarity or hypovolemia that increases nephron water reabsorption and induces vasoconstriction at high levels

Antidiuretic Hormone (ADH / Vasopressin)

Cardiac hormones released from distended atria and ventricles that antagonize RAAS by inducing vasodilation, inhibiting renin/aldosterone, and promoting natriuresis and diuresis

Natriuretic Peptides (ANP and BNP)

Pathological accumulation of fluid in the extracellular interstitial space resulting from imbalances in Starling hydrostatic and oncotic forces

Interstitial Edema

Etiology of edema driven by intravascular fluid retention and venous congestion in clinical conditions like Heart Failure and Chronic Kidney Disease

Increased Capillary Hydrostatic Pressure

Mechanism of edema where low serum albumin reduces intravascular osmotic pulling force, leading to dependent edema, ascites, and periorbital edema

Hypoalbuminemia (Decreased Capillary Oncotic Pressure)

Etiology of edema resulting from inflammatory breakdown of intercellular junctions that permits plasma proteins and fluid to escape into tissues

Increased Endothelial Permeability

Etiology of edema where failure of lymphatic vessels to reabsorb filtered fluid and proteins causes protein-rich accumulation and high interstitial oncotic pressure

Lymphatic Obstruction

Blood pressure classification defined by a Systolic pressure <120 mmHg AND a Diastolic pressure <80 mmHg

Normal Blood Pressure

Blood pressure classification defined by a Systolic pressure of 120–129 mmHg AND a Diastolic pressure <80 mmHg

Elevated Blood Pressure

Blood pressure classification defined by a Systolic pressure of 130–139 mmHg OR a Diastolic pressure of 80–89 mmHg

Stage 1 Hypertension

Blood pressure classification defined by a Systolic pressure >=140 mmHg OR a Diastolic pressure >=90 mmHg

Stage 2 Hypertension

Severe blood pressure elevation (>180/120 mmHg) accompanied by acute, life-threatening target organ damage

Hypertensive Emergency

Multifactorial high blood pressure arising from complex genetic and environmental interactions without a single distinct underlying cause

Primary (Essential) Hypertension

High blood pressure resulting from an identifiable underlying primary disease process such as renal artery stenosis or endocrine tumors

Secondary Hypertension

Specific component of arterial blood pressure recognized as the most significant clinical risk factor driving target organ damage in the brain, heart, kidneys, eyes, and vasculature

Systolic Hypertension

Antihypertensive strategy that promotes renal sodium and water excretion to lower intravascular volume and reduce cardiac preload

Diuretics

Antihypertensive strategy that reduces cardiac output by decreasing heart rate (negative chronotropy) and myocardial contractility (negative inotropy)

Beta-Blockers

Pharmacological strategy that lowers blood pressure by relaxing arteriolar smooth muscle or inhibiting Angiotensin II formation to reduce total peripheral resistance

Vasodilators and ACE Inhibitor