1. Cardiovascular System: Blood Vessels and Circulation
Nestor T. Hilvano, M.D., M.P.H.

2. Learning Objectives
Differentiate the types of blood vessels on the basis of their structure and function.
Describe the factors that influence blood pressure and how it is regulated.
Discuss the important processes of capillary exchange.
Discuss venous return and circulatory shock.
Identify the special circulation to the brain, heart, and lungs.
Identify the major blood vessels of pulmonary and systemic circuits and the areas they serve.
Identify the differences between fetal and adult circulation.

3. Anatomy of Blood Vessels
_____ carry blood away from heart
_____ carry blood back to heart
_____ connect smallest arteries to veins
Where does diffusion between blood and interstitial fluid occur?
a. Capillary b. Vein c. Artery d. Lymph

4. Vessel Wall
____- simple squamous endothelium overlying a basement membrane, with Internal elastic membrane; inner layer
____- smooth muscle for vasomotion, with External elastic membrane; middle layer
____- loose connective tissue, with vasa vasorum (small b.v. within a large vessel); outer layer
a. Tunica intima b. tunica adventitia c. tunica media

5. Comparison of Typical Artery and Vein
Feature
Artery
Vein
Lumen
Regular
Irregular
Thickness of Wall
Thick
Thin
Internal Elastic Membrane
Visible
Not distinct
Thickest Coat
T. Media
T. Adventitia
Valves
No valvee
With valves

6. Types of Vessels Elastic artery (large a.) Conducting artery
Aorta and pulmonary trunk
Muscular artery (med-sized a.)
Most arteries
distributes blood to specific organs
Resistance artery (small a.)
control amount of blood to various organ; little or no T. externa

7. Types of Capillaries Capillaries - smallest vessels with thin walls
____ – complete endothelial lining; found in all tissues except epithelia and cartilage
____ – pores in endothelial lining; found in choroid plexus, kidney, intestine, endocrine organs
____ – gaps in between endothelial cells, incomplete basement membrane, irregular outline; found in liver, bone marrow, spleen
a. sinusoids b. continuous c. fenestrated

8. Veins Veins – larger diameter than arteries, have: Varicose veins
____ walls: a. thin b. thick
____ blood pressure: a. low b. high
___ aid skeletal muscles in upward blood flow: a. valves b. sphincters
Veins expand easily at low pressure (capacitance vessels)
Varicose veins
Hemorrhoids

9. Principles of Blood Flow
Important for delivery of ______ and ______, and removal of metabolic waste.
Hemodynamics
physical principles of blood flow based on pressure and resistance
F  P/R, (F = flow, P = difference in pressure, R = resistance to flow)

10. Blood Pressure Force that blood exerts against a vessel wall
S_____ pressure – BP during ventricular contraction
D_____ pressure – BP during ventricular relaxation
BP = SP/DP , in young adult (120/80 mm Hg)
Mean Arterial Pressure (MAP) = diastolic pressure + pulse pressure 3
Effect of age in BP level? ______
BP determined by cardiac output, blood volume and peripheral resistance

11. Total Peripheral Resistance: Factors
Blood viscosity – resistance to flow by RBC’s and albumin
 viscosity with anemia (flow at low pressure)
 viscosity with polycythemia (flow under high pressure)
Turbulence – upset the smooth flow of blood, create eddies and swirls, increases resistance and slows blood flow
Vascular resistance – friction between blood and vessel walls
a) Vessel length- Blood pressure and flow decrease with distance (increases friction)
b) Vessel diameter (radius)- controls resistance quickly; vasomotion; Vasoconstriction -  BP; Vasodilatation-  BP
Increasing the length increases the friction (the larger the surface area in contact with the blood)

12. Abnormalities of Blood Pressure
_____________
chronic resting BP
> 140/90
consequences
can weaken small arteries and cause aneurysms
chronic low resting BP
< 90/60
caused by blood loss, dehydration, and anemia
a. hypotension b. hypertension

13. Regulation of BP and Flow
Autoregulation (immediate, localized response) - chemical changes (histamine, bradykinin, low O2, high CO2, low pH)
Neural control - Vasomotor center of medulla oblongata, integrates baroreceptor reflexes and chemoreceptor reflexes
Endocrine control (direct long- term changes)
- renin – angiotensinogen – aldosterone, ADH, ANP, Epi, NEpi

14. Capillary Exchange Mechanisms involved
diffusion, filtration and reabsorption
Opposing forces
capillary hydrostatic pressure (CHP) drives fluid out of capillary: Filtration
blood colloid osmotic pressure (BCOP) draws fluid into capillary: Reabsorption
Capillary filtration at arterial end; Capillary reabsorption at venous end
Edema = condition when fluids build up in peripheral tissues

15. Mechanisms of Venous Return
Gravity drains blood from head and neck
Skeletal muscle pump in the limbs
Thoracic (respiratory) pump
blood flows faster with inhalation
Exercise  venous return
Venous pooling occurs with inactivity
- with prolonged standing, Cardiac Output may be low enough to cause dizziness or syncope
- Shock = reduction of effective circulating blood, blood pressure and cardiac output

16. Pulmonary and Systemic Circulations
Major vessels - pulmonary arteries and pulmonary veins
Trace the blood flow beginning at the right ventricle and ending at the left atrium.
The aorta
Major branches of aortic arch – brachiocephalic a., left common carotid a., left subclavian a.

17. Fetal Circulation Umbilical vein Ductus venosus Foramen ovale
Ductus arteriosus
Umbilical arteries

18. Homework (Self-Review)
Define the following: angina pectoris, myocardial infarction, capillary, blood pressure, capacitance vessels, edema, shock, aneurysm, peripheral resistance, varicose, and hemorrhoid.
Compare and contrast artery and vein as to structure and function.
Describe the walls of blood vessels.
Describe the types of capillaries and give example where you can find them.
List the 3 major branches of the aortic arch.
Discuss the fetal circulation. What becomes of these fetal structures after birth?
Give example of elastic artery, muscular artery, large vein, fenestrated capillary, and continuous capillary .