1. BLOOD VESSEL STRUCTURE, BLOOD PRESSURE AND SYSTEMIC VESSELS

2. Blood Vessels: The Vascular System
Types of blood vessels:
Arteries (in direct contact with the heart) and Arterioles
Carry blood away from the heart
Capillaries
Where substance exchange (gases, nutrients, hormones, etc) between other tissues and the blood occurs
Venules and Veins (in direct contact with the heart)
Return blood toward the heart

3. Arteries and Arterioles
1. Arteries are strong, elastic vessels adapted for carrying high-pressure blood.
2. The inside space of an artery through which blood flows is the lumen.
The wall of an artery has 3 layers. From the inside to the outside they are:
Tunica interna (endothelium)- Elastic tissue
Tunica media- Smooth muscle and elastic tissue
Tunica externa (adventitia)- Elastic tissue
The structure of an artery helps it propel blood onward while the ventricles are relaxing.
Arterioles are very small (almost microscopic) arteries

4. Arteries and Arterioles continued..
6. When the sympathetic nervous system (fight or flight) is active, the smooth muscle of arteries contract, which narrows the lumen (less blood flow). This is called vasoconstriction. When the parasympathetic nervous system is active, the smooth muscle relaxes, which increases the lumen diameter. This is called vasodilation.
*When would vasoconstriction occur? Vasodilation?

6. Tunica Interna
Tunica Media
Tunica Externa
Artery – Cross section

7. Capillaries
Capillaries are the smallest vessels, consisting only of one cell layer through which substances are exchanged with tissue cells. Consist only of the tunica intima.
The number of capillaries throughout the body varies, depending on metabolic activity. Tissues with high metabolic requirements include the muscles, liver, kidneys and nervous system.
3. Because they are so numerous, blood flows more slowly through them which helps with substance exchange.
4. Precapillary sphincters (rings of smooth muscle) regulate the flow of blood into capillaries.

8. Capillary Beds

9. Exchanges in Capillaries
1. At the arteriole end of a capillary, the blood pressure is high, which forces oxygen, water and nutrients out of the capillary. This is called filtration.
2. At the venule end of a capillary, the blood pressure is lower, which causes most water and solutes that were forced out before to diffuse back into the capillary. This is called reabsorption. About 85% of the fluid filtered is reabsorbed. The carbon dioxide from the surrounding cells gets absorbed as well.

10. Filtration
Reabsorption

11. Venules and Veins
1. Venules leading from capillaries merge to form veins that return blood to the heart.
Veins have the same three layers as arteries, but are much thinner. They do not carry the same high pressure blood.
Veins have flap-like valves inside to prevent backflow of blood.
4. Veins use the milking action of skeletal muscles to move blood because they are not lined with the same amount of smooth muscle as arteries.

12. Movement of Blood Through Veins

13. Varicose Veins
In people with weak vein valves, gravity forces blood backwards through the valve. This increases venous blood pressure, which pushes the vein’s wall outward. After this repeatedly happens, the walls lose their elasticity and become stretched and flabby. This is called varicose veins.

14. Main Differences Between Blood Vessels
Walls of arteries are the thickest and their smooth muscle helps move blood
Lumens of veins are larger because walls are thinner
Larger veins have valves to prevent backflow
Skeletal muscle “milks” blood in veins toward the heart
Walls of capillaries are only one cell layer thick to allow for exchanges between blood and tissue

16. Blood Pressure
Blood pressure is the pressure exerted by blood on the walls of a blood vessel. It is highest in the aorta and large arteries branching off of the aorta.
Blood pressure is affected by the distance from the left ventricle , the total volume of blood, vasoconstriction/vasodilation and blood viscosity.
Pressure in an artery is approximately 93 mm Hg, in a capillary is 35 mm Hg and in a venule is 16 mm Hg.
Loss of blood would lower bp as water retention would raise bp.
Vasoconstriction raises bp as vasodilation lowers bp.
Blood viscosity is “thickness” of blood. The greater the # of blood cells and solutes, the greater the bp.

17. Comparison of Blood Pressures in Different Vessels

18. Systolic/Diastolic Pressure
A healthy blood pressure reading is 120 mm Hg/80 mm Hg.
Systolic Blood Pressure is the top number of a blood pressure reading (120). This is the pressure that the blood is putting on the arteries as the ventricles contract, forcing blood out of the heart.
Diastolic Blood Pressure is the bottom number of a blood pressure reading (80). This is the pressure that the blood is putting on the arteries as the ventricles relax.
The surge of blood that occurs with ventricular contraction can be felt at certain points in the body as a pulse. The pulse rate normally is about bpm.

19. Measuring Arterial Blood Pressure

20. Pulse Pulse - Pressure wave of blood
Monitored at “pressure points” in arteries where pulse is easily felt
Pulse averages 70–76 beats per minute at rest

21. Variations in Blood Pressure
Normal human range is variable:
Normal
140–110 mm Hg systolic
80–70 mm Hg diastolic
Hypotension
Low systolic (below 110 mm HG)
Often associated with illness
Hypertension
High systolic (above 140 mm HG)
Can be dangerous if it is chronic

22. What helps maintain normal blood pressure?
Baroreceptors- Pressure receptor nerve cells which are located in the aorta and other large arteries and send messages to the brain.
Chemoreceptors- Measure the chemical composition (O2 and CO2) of blood. These cells send messages to alter respiration rate.
Hormones- Regulate blood flow and pressure
Renin, Adrenaline, ADH

23. Systemic Circulation
The systemic circuit includes the aorta and its branches leading to all body tissues as well as the system of veins returning blood to the right atrium.

24. Major Arteries of Systemic Circulation Areas that they feed
1. External carotid-external to skull
2. Internal carotid- internal to skull
3. Common carotid- branches into external and internal
4. Vertebral- posterior brain
5. Brachiocephalic trunk-branches into right subclavian and right common carotid
6. Brachial-arm
7. Renal-kidney
8. Radial-radial side of forearm
9. Common iliac-branches into internal and external iliac
10. Internal iliac- pelvis
11. Subclavian- parts of brain, spinal cord, neck, chest, shoulder
12. Axillary- shoulder
13. Ulnar- ulna side of forearm
14. External iliac- lower limbs
15. Femoral- groin and thigh
16. Posterior tibial- posterior muscles and bones of leg and foot
17. Popliteal- knee and posterior leg muscles
18. Anterior tibial-anterior muscles and bones of leg and foot

25. Major Arteries of Systemic Circulation

26. Parts of the Aorta The aorta has 4 parts:
Ascending aorta- Emerges from the left ventricle; where the coronary arteries branch to feed the heart.
Arch of the aorta- As the name implies, where the aorta “arches” to the left. The brachiocephalic trunk, left common carotid artery and left subclavian arteries branch off of this.
Thoracic aorta- The descending portion that is begins at the 4th/5th thoracic vertebrae and continues until the diaphragm opening.
Abdominal aorta- The descending portion between the diaphragm opening and the 4th lumbar vertebra.

27. Label the 4 parts of the aorta

28. Major Veins of Systemic Circulation Areas that they drain
1. Internal jugular- head
2. Vertebral- neck, cervical vertebrae
3. Brachiocephalic-dumps into the SVC
4. Brachial-forearm, elbow, and humerus
5. Renal- kidney
6. Radial- radius side of forearm
7. Common iliac- Pelvis and upper leg
8. Internal iliac- pelvis
9. Greater saphenous-longest in the body- femur region
10. Posterior tibial- back side of lower leg
11. Subclavian- arms, neck, thoracic wall
12. Axillary- arms and upper chest
13. Cephalic- lateral upper limbs
14. Hepatic-liver
15. Median cubital-elbow
16. Ulnar- ulna side of forearm
17. Femoral- thigh
18. Popliteal- knee
19. Small saphenous-Foot and posterior leg
20. Anterior tibial-anterior portion of leg, ankle and knee

29. Major Veins of Systemic Circulation

30. Common Blood Vessel Disorders
Hypertension- High blood pressure
Systolic greater than 140 mm Hg and Diastolic greater than 90 mm Hg
Effective treatments include: lose weight, limit alcohol intake, exercise, reduce sodium intake, don’t smoke and manage stress.
Aneurysm- A thin, weakened section of the wall of an artery or a vein. If it bursts, massive hemorrhaging could result.
Aneurysm video
Endovascular aneurysm repair

31. Abdominal Aortic Aneurysm- EEEKKK!!!