1. BLOOD VESSELS Arteries Away from the heart Oxygen rich Elasticity and contractility (ANS, sympathetic) Divide into smaller vessels- arterioles Which divide to single cell layer thick capillaries

2. Arterial walls  3 layers around an opening: lumen  Endothelium-Inner layer is made of simple squamous epithelium  Middle layer: made of smooth muscle and elastic fibers  Outer layer: elastic and collagen fibers

3. Blood vessels  Veins  Oxygen poor blood  Carry blood to the heart  Similar to arteries but the smooth muscle layer is thinner  Branch into smaller vessels : venules  Venules branch into capillaries  Contains folds in the inner layer called:valves  Lumen is wider than in corresponding arteries

4. Veins

5. Varicose veins

6. Capillaries  Connect arterioles to venules  Primary function: exchange nutrients and waste between blood and tissue cells.  Certain tissue with more metabolic activity (muscle, nerve, kidney, liver) require more caplillaries.  Composed of a single layer of endothelium and a basement membrane  Flow of blood in capillaries is regulated by smooth muscle fibers + precaplillary sphincters: rings of smooth muscle at their origin.

7. Blood reservoirs  Veins- 60%, referred to as blood reservoirs (also liver + spleen)  Arteries-15%  Pulmonary Vessels-12%  Heart-8%  Capillaries-5%

8. PHYSIOLOGY OF CIRCULATION  Blood flow: amount of blood that passes thru a vessel in a given period of time.  Determined by:  Blood pressure  Resistance  Blood pressure: pressure exerted on the wall of a vessel  Resistance: opposition to blood flow from friction between blood + vessel walls related to:  Viscosity-adhesiveness  Blood vessel length- the longer the more resistance

9. 3 Factors Affecting Blood Pressure 1.Cardiac Output: amount of blood leaving the lt. ventricle each minute. Stroke volume x heart rate a.chemicals: epinephrine, K, Na, Ca: increase CO, which increases BP b.temperature, emotions, gender, age

10. Factors continued  2. Blood Volume: Normal = 5 liters or quarts Normal = 5 liters or quarts Anything that decreases blood volume decreases blood pressure Ex:Trauma like a hemorrhage, diuretics Anything that increases blood volume increases blood pressure Anything that increases blood volume increases blood pressure Ex: Salt intake

11. Factors continued 3. Peripheral resistance: resistance to blood flow as it moves away from the heart. a. mostly in arterioles,capillaries, + venules b. arterioles control blood pressure + flow by changing their diameter. Vasoconstriction + Vasodialation This process is controlled by the vasomotor center in the medulla oblongata This process is controlled by the vasomotor center in the medulla oblongata

12. Factors continued

13. Vasomotor Center  Located in the Medulla Oblongata  Maintains peripheral resistance in the arterioles( especially skin, abdominal viscera)  Increased sympathetic impulse=increase vasoconstriction and decreases in impulses=vasodilatation  Is modified by: baroreceptors,chemoreceptors,brain, and hormones

14. Baroreceptors  Same as in the control of heart rate:  Parasympathetic stimulation slows things down and thus lowers Blood Pressure (BP)  Sympathetic speeds things up thus Increasing BP  Special note: blood vessels are controlled by sympathetic only.

15. Capillary Exchange  Filtration- fluid goes from arteriole end capillaries into surrounding interstitial tissue.  Reabsorbtion-fluid returns to into the venous end capillaries  About 85% of filtered fluid reabsorbs, the rest is returned to the cardiovascular system by the lymphatic system

16. Pulse + Blood Pressure  Pulse- alternate expansion and recoil of an artery with each contraction of the lt. ventricle.  Tachycardia- rapid pulse over 100/min  Bradycardia- slow pulse under 60/min  Measured by a sphygmomanometer  120/80=systolic/diastolic  Systolic=pressure against arterial wall during vent. Contraction.  Diastolic=pressure against arterial wall during vent. relaxation

17. Circulatory Routes  Pulmonary-lungs  Systemic- rest of the body  Cerebral – brain  Hepatic Portal- liver  Fetal – see ch.24  Renal- kidney

18. 3 functional adaptations for venous return  Respiratory pump-changes in abdominal and thoracic pressure during breathing  Muscular pump-milking of skeletal muscle  Smooth muscle contraction under sympathetic control

19.  Orthostatic Hypotension  Old people –sympathetic system can not respond fast enough when they stand up  Hypertension – high blood pressure over 140 (systolic)  Hypotension- low blood pressure below 90