Week 6 · Lecture Slides · Cardiovascular

Blood Vessels & Hemodynamics.

Seven slides on arteries, veins, capillaries, and the physics of blood flow. Sketch each vessel type and the BP regulators from memory.

Practice these cards

Core concept

Blood Vessels & Hemodynamics

What you'll do

  • Move through six concept slides
  • Three slides have a drawable canvas
  • Toolbar: pen color, size, eraser, undo, add image, save
  • Drop in your own anatomy images to label them
Vessels + Pressure + Flow

Vessel types

Arteries (elastic + muscular)
Arterioles
Capillaries
Venules
Veins

BP regulation

Baroreceptors (fast)
Chemoreceptors
RAAS (kidney)
ADH

Structure

Vessel Wall Layers

Three tunicas

  • Tunica intima: endothelium + basement membrane
  • Tunica media: smooth muscle + elastin (thickest in arteries)
  • Tunica externa (adventitia): connective tissue
  • Arteries have thick media (resist pressure)
  • Veins have thinner walls + valves (prevent backflow)
  • Capillaries: just endothelium + basement membrane (single cell thick)
Takeaway: wall structure matches function. Arteries: thick muscular wall handles pulse. Veins: thin wall, lumen wide, valves; pressure is low. Capillaries: just thin enough for diffusion.

Vessels

Compare Vessel Types

Cross-sections

  • Elastic artery (aorta): tons of elastin, recoils
  • Muscular artery (femoral): thick media, regulates flow distribution
  • Arteriole: mostly smooth muscle; the major resistance vessel
  • Capillary: endothelium only; site of exchange
  • Venule + vein: low pressure, valves, capacitance vessels
Draw: five concentric circles side by side showing cross-sections of elastic artery, muscular artery, arteriole, capillary, and vein. Label each tunica + lumen size. Show valves on vein.

Capillaries

Capillary Exchange

Where work happens

  • Continuous: tight junctions, most common (muscle, skin, brain)
  • Fenestrated: pores, fast exchange (kidney, intestine, endocrine)
  • Sinusoidal: large gaps, allow cells through (liver, spleen, marrow)
  • Starling forces: hydrostatic pressure pushes out, oncotic pressure pulls in
  • Net filtration at arteriole end, net absorption at venule end
  • Excess fluid drained by lymphatics
Takeaway: edema = imbalance in Starling forces. Causes: high venous pressure (CHF), low albumin (liver failure), blocked lymphatics (lymphedema), inflammation (leaky capillaries).

BP

Blood Pressure Mechanics

Systolic vs diastolic

  • Systolic BP: peak during ventricular ejection (~120 mmHg)
  • Diastolic BP: baseline during ventricular relaxation (~80 mmHg)
  • Pulse pressure = systolic - diastolic (~40 mmHg)
  • MAP (mean arterial pressure) = DBP + 1/3 pulse pressure
  • MAP > 60 mmHg required to perfuse organs
  • BP = cardiac output x systemic vascular resistance (CO x SVR)
Draw: a BP cuff schematic. Above the brachial artery, a curve showing systolic at the top and diastolic at the bottom of the wave. Label pulse pressure (the difference) and MAP (closer to diastolic since you're in diastole most of the cycle).

Regulation

BP Regulation

Multiple systems

  • Baroreceptors in carotid sinus + aortic arch, fast (seconds)
  • High BP → ↓ HR + dilate vessels (via vagus + SNS withdrawal)
  • Chemoreceptors respond to O₂, CO₂, pH
  • RAAS (renin-angiotensin-aldosterone): kidney sees low BP, releases renin → angiotensin II (vasoconstrict) + aldosterone (retain Na⁺/H₂O)
  • ADH (vasopressin): water retention, vasoconstriction
  • ANP: opposite, atrial natriuretic peptide drops BP
Takeaway: most hypertension drugs target RAAS. ACEi (block AT-I → AT-II conversion), ARBs (block AT-II receptor), beta blockers (block SNS), diuretics (drop volume), calcium channel blockers (vasodilate).

Clinical

Vascular Disorders

Common hits

  • Hypertension: sustained BP > 130/80 (newer guidelines)
  • Atherosclerosis: plaque in arterial walls
  • Aneurysm: wall weakening, balloon-out; rupture is catastrophic
  • DVT: deep vein clot, risk of PE
  • Varicose veins: failed valves, distended veins
  • Shock: circulatory failure (hypovolemic, cardiogenic, distributive)
  • Orthostatic hypotension: BP drops standing up
Takeaway: shock is failure of perfusion, not just low BP. You can be normotensive in early shock if vasoconstriction compensates. Lactate, urine output, mental status are better early markers.