1. The Circulation of the Blood
Chapter 15
The Circulation of the Blood

2. Lesson 15.1
Structure and Function of Blood Vessel Circulation and Related Disorders
Describe the structure and function of each major type of blood vessel: artery, vein, and capillary.
List the major disorders of blood vessels and explain how they develop.
Trace the path of blood through the systemic, pulmonary, portal, and fetal circulations.

3. Blood Vessels
Types
Arteries—carry blood away from the heart and toward capillaries
Veins—carry blood toward the heart and away from capillaries
Capillaries—carry blood from the arterioles to the venules

4. Structure of Blood Vessels
Arteries
Tunica intima—inner layer of endothelial cells
Tunica media—smooth muscle, thick in arteries; some elastic tissue; important in blood pressure regulation
Tunica externa—outer layer of fibrous connective elastic tissue
Capillaries—microscopic vessels
Only one layer—the tunica intima

5. Structure of Veins
Tunica intima—inner layer; valves prevent retrograde movement of blood
Tunica media—smooth muscle; thin in veins
Tunica externa—heavy layer of fibrous connective tissue in many veins

6. Artery and Vein

7. Blood Vessels Functions
Arteries—distribute nutrients, gases, etc., carried in the blood by way of high pressure; assist in maintaining the arterial blood pressure; serve as blood reservoirs
Capillaries—serve as exchange vessels for nutrients, wastes, and fluids
Veins—collect blood for return to the heart; low-pressure flow of blood (compared to arteries)

8. Principal Arteries of the Body

9. Principal systemic arteries.9

10. Principal Veins of the Body

11. Systemic Veins 11

12. Disorders of Blood Vessels
Disorders of arteries—arteries must withstand high pressure and remain free of blockage
Arteriosclerosis—hardening of arteries caused by calcification of fatty deposits on arterial walls
Reduces flow of blood, possibly causing ischemia that may progress to necrosis (or gangrene)
May be corrected by vasodilators (vessel-relaxing drugs) or angioplasty (mechanical widening of vessels), or surgical replacement
Atherosclerosis—lipids and other matter block arteries

13. Partial Blockage of an Artery in Atherosclerosis

14. Balloon Angioplasty

15. Disorders of Arteries Aneurysm—abnormal widening of arterial wall
Promotes formation of thrombi that may obstruct blood flow to vital tissues
Arterial walls may burst, resulting in life-threatening hemorrhaging
Cerebrovascular accident (CVA) or stroke—ischemia (reduced blood flow) of brain tissue caused by embolism or hemorrhage

16. Disorders of Veins Veins are low-pressure vessels
Varicose veins (varices)—enlarged veins in which blood pools
Hemorrhoids are varicose veins in the rectum
Treatments include supporting affected veins and surgical removal of veins
Thrombophlebitis—vein inflammation (phlebitis) accompanied by clot (thrombus) formation; may result in fatal pulmonary embolism

17. Varicose Veins

18. Circulation of Blood Systemic and pulmonary circulation
Blood circulation—refers to the flow of blood through all the vessels, which are arranged in a complete circuit or circular pattern
Systemic circulation
Carries blood throughout the body
Path goes from left ventricle through aorta, smaller arteries, arterioles, capillaries, venules, venae cavae, to right atrium

19. Diagram of Blood Flow in the Circulatory System

20. Pulmonary & Hepatic Portal Circulation
Pulmonary circulation
Carries blood to and from the lungs
Arteries deliver deoxygenated blood to the lungs for gas exchange
Path goes from right ventricle through pulmonary arteries, lungs, pulmonary veins, to left atrium
Hepatic portal circulation
Unique blood route through the liver
Vein (hepatic portal vein) exists between two capillary beds
Assists with homeostasis of blood glucose levels
Stores glycogen and detoxifies the blood

21. Hepatic Portal Circulation

22. Fetal Circulation Refers to circulation before birth
Modifications required for fetus to efficiently secure oxygen and nutrients from the maternal blood
Unique structures include the placenta, umbilical arteries and vein, ductus venosus, ductus arteriosus, and foramen ovale

23. The Fetal Circulation

24. Changes to Fetal Circulation at Birth
Baby's specialized fetal blood vessels must stop working
When newborn first breathes air, the pressure exerted closes off those vessels and the foramen ovale
If the foramen ovale fails to close, ATRIAL SEPTAL DEFECT (ASD) occurs, creating a lack of oxygen
Resulting bluish tint is called cyanosis

25. Congenital heart defects.25

26. Circulation Physiology
Blood exchanges oxygen, carbon dioxide, other substances generated by cells.
Tissue fluid (interstitial fluid) is the exchange medium.

27. Circulation Physiology (cont.)
Capillary Exchange
How substances move between cells and capillary blood
Diffusion
Main process
Blood pressure
Moves material into the interstitial fluid (filtration)
Osmotic pressure
Moves material from the interstitial fluid back into capillaries (osmosis)

28. The role of capillaries.
Circulation Physiology
The role of capillaries. 28

29. Circulation Physiology (cont.)
Return of Blood to the Heart
Mechanisms that promote blood’s return to the heart
Contraction of skeletal muscles
Valves in the veins
Breathing

30. Circulation Physiology (cont.)
Blood return. 30

31. Blood Pressure and Hypertension, Pulse Points, and Circulatory Shock
Lesson 15.2
Blood Pressure and Hypertension, Pulse Points, and Circulatory Shock
Identify and discuss the factors involved in the generation of blood pressure and how they relate to each other.
Define pulse and locate the major pulse points on the body.
Define hypertension and its associated risk factors and complications.
Explain what is meant by the term circulatory shock and describe the major types.

32. Blood Pressure Defining blood pressure
“Push” or force of blood in the blood vessels
Exists in all blood vessels—highest in arteries, lowest in veins
Blood pressure gradient—causes blood to circulate; liquids can flow only from areas of high pressure to areas of low pressure
Hypotension- Low or nonexistent blood pressure gradient is fatal if not reversed
Hypertension- (high blood pressure) can cause a blood vessel to rupture

33. Pressure Gradients in Blood Flow

34. Factors that Influence Blood Pressure
Blood volume—the larger the volume, the more pressure is exerted on vessel walls
Strength of heart contractions—affect cardiac output; stronger heartbeat increases pressure; weaker beat decreases it
Heart rate—increased rate increases pressure; decreased rate decreases pressure

35. Blood Viscosity and Resistance to Flow
Blood viscosity (thickness)—less than normal viscosity decreases pressure; more than normal viscosity increases pressure
Resistance to blood flow (peripheral resistance)—affected by many factors, including the vasomotor mechanism (vessel muscle contraction/relaxation)

36. Vasomotor Mechanism

37. Fluctuations in Blood Pressure
Blood pressure varies within normal range from time to time
Central venous pressure—influences pressure in large peripheral veins
Venous return of blood to the heart depends on five mechanisms
A strongly beating heart
An adequate arterial blood pressure
Valves in the veins
Pumping action of skeletal muscles as they contract
Changing pressures in the chest cavity caused by breathing

38. Pulse
Definition—alternate expansion and recoil of the blood vessel wall
Nine major pulse points named after arteries over which they are felt

39. Pulse Points

40. Hypertension (HTN) Occurs when blood pressure exceeds 140/90 mm Hg
Ninety percent of HTN cases are primary essential (idiopathic); secondary HTN can be caused by kidney disease or other causes
Many risk factors for HTN, including genetics, age, stress, obesity, and more
Untreated HTN may contribute to heart disease, kidney failure, and stroke

41. Classification of Hypertension

42. Circulatory Shock
Failure of the circulatory system to deliver oxygen to the tissues adequately, resulting in cell impairment
Cardiogenic shock—caused by heart failure

43. Hypovolemic Shock
Drop in blood volume that causes blood pressure (and blood flow) to drop
Often caused by hemorrhage or loss of interstitial fluid, causing blood plasma to drain out of the vessels

44. Negative Feedback

45. Neurogenic Shock
Caused by nerve condition that relaxes (dilates) blood vessels and thus reduces blood flow
Occurs when sympathetic stimulation is disrupted

46. Anapyhlactic Shock
Results from an acute allergic reaction called anaphylaxis
Causes the same kind of blood vessel dilation that occurs in neurogenic shock

47. Septic Shock
Results from complications of septicemia (toxins in blood resulting from infection)
Toxins dilate blood vessels, inducing shock