Compliments of Gary Larson

Pre-Lab Lecture

Blood Vessels and Circulation

Chapter 13

Peripheral Circulation:Systemic Circulation:

Blood vessels directing blood to the body tissuesLeft Heart to Right Heart

Pulmonary Circulation: Blood vessels directing blood to the lungs

for gas exchangeRight Heart to Left Heart

Functions:Carry Blood: “Duh!”Gas and Nutrient Exchange:

O2/CO2, Energy substrates, Minerals, H2O and wastes

Transport:“Special delivery”: Supply/Demand

Regulate Blood Pressure:Perfusion Homeostasis (More…)

Perfusion Homeostasis:Internal Environment: Depends

on appropriate perfusion (Blood flow)

Homeostasis: A constant balance of choices in maintaining blood pressure and distribution to demanding tissues

Important Homeostasis Key! Since Blood

transports life sustaining substances…

Appropriate Perfusion (Circulation) is the Key to Homeostasis!

Arteries:Vessels taking

blood Away From The Heart

Usually O2 and nutrient rich…”Supply” to tissues

Arteries: Structure/FunctionHigh Pressure Conduits:

Elastic Connective Tissue: Expands with systole, and recoils with diastole

Smooth Muscle: Assist in “pumping” and “directing” blood flow

Endothelium: Smooth inner surface

Veins:Vessels returning

blood Back To The Heart

Usually low in O2 – carrying wastes for removal

Veins: Structure/FunctionLow Pressure “Pools”:

Sometimes called “capacitance vessels” because they have a large resevoir (capacity) for blood

Less connective tissue and smooth muscle than arteries

Endothelium: Specialized valves assist blood flow toward heart

Check Out Those Valves! Locate the veins in

your forearm or hand

Place your index finger on a vein, then “milk” the vein toward your shoulder with your thumb…

NEXT…Leave the finger in place and observe if the

blood flows back when you remove your thumb

Remove your finger, observing what happensRepeat the experiment, only next time, milk

the vein toward your hand…now what happens?

How many valves can you locate?

CAPILLARIES:Gas ExchangeNutrient DeliveryWaste RemovalA Whole lot of

Diffusion Going On…

Capillaries: Structure/FunctionFunction: Diffusion/Osmosis!Endothelium: Single epithelial

(squamous) cell thickLumen: Just big enough to allow passage

of Red Blood CellsBlood flow affected by:

Pre-capillary sphincter/ArteriolesSurrounding tissues

Terms to Know:Vessel Layers:

Tunica Adventitia (Externa): Connective tissue surrounding vessel

Tunica Media: Elastic Connective tissue and Smooth Muscle

Tunica Intima: Basement membrane and endothelium

More Terms:Vasoconstriction: Contraction of

vascular smooth muscle to narrow the vessel lumenIncreases Vascular Resistance

Vasodilation: Relaxation of vascular smooth muscle to increase the diameter of vessel lumenDecreases Resistance

Pressure and Perfusion…Physiology of Circulation Systolic Pressure: Highest

arterial pressure following ventricular systoleMust be high enough to

adequately perfuse vital tissues (generally >100 mmHg)

Pressure and Perfusion:Diastolic Pressure: Lowest arterial

pressure during ventricular diastole The pressure in arteries when they are

fully openThe higher the pressure, the smaller

the collective arterial vessel bed Which leads us to…

Total Peripheral Resistance: (More terms)Resistance: Any impedance of

blood flow – usually by narrow or inelastic vessels

Total Peripheral Resistance: The collective sum of the entire arterial vascular bed resistance.

TPR: Effect on Perfusion

Increased Resistance (TPR):Increases the work of the heart and

ultimately heart failureCauses a greater drop in blood

pressure (perfusion) DOWNSTREAM possibly causing tissue ischemia (inadequate oxygen)

Final Terms: Conducting Vessels: Arteries that

are very elastic (low resistance) and transmit blood flow without a large drop in pressure

Resistance Vessels: Arterioles that are active in directing blood flow by selective vasoconstriction resulting in the largest drop in arterial pressure

Exercise Application:Exercise

Training increases Maximum Oxygen Consumption

VO2 Peak

Where is that happening?Oxygen Delivery:

O2 Exchange and Carrying capacity (Lungs/RBC) = Blood

Cardiac OutputDelivery: More blood flow to muscles

Oxygen Uptake: Increased a-vO2 Difference

a-vO2 Difference:The measured difference in O2

content between the arterial (delivery) and venous (removal) circulation

An indication of O2 consumption by the working tissues (more O2=more work)

VeinsArteries

O2 extractedby mitochondria

20 ml O2 15ml O2

Training Increases the a-vO2 DifferenceIncreases Cellular oxidative

capacity:More mitochondria and oxidative

enzymes Increases Working tissue mass and

the capillary network feeding it…More oxygen delivery