Vascular anatomy

Learning goals I will identify the structure and function of components of vascular system. I will identify the physiological effects of training to the vascular system.

Parts of vascular system

ARTERIES & ARTERIOLES carry blood away from the heart very thick muscular walls, but also very elastic (so that they continue to ‘push’ blood through during diastole as they recoil) branch into smaller and smaller vessels called ARTERIOLES regulate blood distribution to various tissues/organs by constricting or d i l a t i n g depending on body’s needs e.g., during exercise, arterioles that supply the muscles & heart dilate and arterioles that supply the intestines contract (therefore, running cramps)

Artery vs Vein

Arteries Arterioles Capillaries Venule Vein Arteries to Veins Arteries Arterioles Capillaries Venule Vein Oxygenated blood Deoxygenated blood

CAPILLARIES capillary walls are only 1 cell thick & are so narrow that a single RBC can barely fit through allows for easy DIFFUSION gas exchange (O2 / CO2) delivery of nutrients from blood to muscles & organs (e.g. glucose) pick-up of waste products from muscles & organs (e.g. lactic acid, CO2)

VEINS & VENULES carry blood back to the heart as blood begins to return to heart, capillaries connect to form larger and larger VENULES which merge into VEINS (eventually merging into sup. or inf. vena cava) veins also have thick muscular walls to push blood back to the heart, but because most veins have to pump blood against gravity (and by then the force of systole is relatively weak), veins have some “back-up” …

VEINS & VENULES Valves – open only in the direction of blood flow and close to prevent ‘backflow’ Skeletal muscle pump – when a muscle contracts, the veins constrict a little which pushes the blood along Thoracic pump – when we breathe in (and diaphragm moves down), pressure in abdominal cavity decreases (more space). when diaphragm relaxes, pressure increases, forcing blood in veins upward

It’s in you to give

BLOOD made up of: plasma - fluid component (55%) blood cells (45%) 99% RBC’s (erythrocytes)- contain HEMOGLOBIN that actually carries O2 to the tissues and CO2 to lungs < 1% WBC’s (leukocytes) - immune system <1% PLATELETS - clotting

blood

VASCULAR REVIEW Q’S What is the function of the smooth muscle that surrounds arteries & veins? Which artery carries deoxygenated blood? Which vein carries oxygenated blood? Why must capillaries be sooooo small? How can capillaries be classified as part of the arterial system and also part of the venous system? What principle accounts for how substances can enter and exit capillaries? Describe how it works using the movement of oxygen between capillaries and muscles as an example. Provide 2 reasons for why blood in our feet can move back up to the heart (against gravity).

training

CARDIOVASCULAR TRAINING EFFECTS recall...our ENERGY SYSTEMS respond to training our CARDIOVASCULAR system also responds to training by making adjustments to…

Q = stroke volume (SV) X heart rate (HR) 1. CARDIAC OUTPUT (Q) the amount of blood pumped into the aorta each minute at rest = 5-6 L/min vs. exercise = 25-30 L/min Q = stroke volume (SV) X heart rate (HR) Obviously, Q increases during exercise (muscles need O2), but it’s not just due to increased HR…SV increases too!

SV increases due to increase in amount of blood returning from veins because of: 1. Skeletal Muscle Pump 2. Thoracic Muscle Pump 3. Constriction of the Veins 4. An Increase in the Force with which the Heart Contracts NOTE: during prolonged exercise, Q is maintained, but SV decreases (sweat = fluid loss), so HR has to increase…CARDIOVASCULAR DRIFT

2. STUCTURE OF THE HEART heart gets bigger & thicker, therefore, can eject more blood per beat and each beat can contract with more force Increased # of capillaries supplying the myocardium

3. DISTRIBUTION OF BLOOD FLOW amount of blood flow that is directed to working muscles increases and blood flow to other organs (e.g., stomach, intestines, kidneys) decreases 2 systems responsible: CNS sends signal to contract/relax muscles surrounding arterioles “autoregulation” – chemicals produced in muscle cells during exercise (e.g. nitric oxide) cause arterioles to relax NOTE: blood flow to brain never decreases

4. BLOOD VOLUME blood plasma increases up to 15% (within only a few days!!!!) # of RBC’s increases with continued training reversed very quickly …1-2 wks

Learning goals I will identify the structure and function of components of vascular system. I will identify the physiological effects of training to the vascular system.