1. AP 110 Fundamentals of Anatomy and Physiology

2. Objectives
Describe the structure and function of blood vessels and the circulatory system

3. Blood Vessels
The blood vessels (arteries, arterioles, capillaries, venules, and veins) form a closed tube that carries blood away from the heart, to the cells, and back again.
Arteryarteriole capillary venule vein

4. Types of Blood Vessels Arteries:
Blood is pumped out of the ventricles into the arteries
Carry blood away from the heart and toward the lungs and capillaries in the tissues.
The smallest arteries are called arterioles. These carry blood to the capillaries.

5. Types of Blood Vessels Veins :
Drain capillaries in the tissues and return the blood to the heart.
The smallest veins are the venules.

6. Types of Blood Vessels Capillaries: Tiny, thin-walled vessels
Allow for exchanges between the blood and body cells, or between the blood and air in the lung tissue.
The capillaries connect the arterioles and venules.
Exchange between the tissues and blood occurs in the capillary beds

7. Blood Circuits Pulmonary circuit Systemic circuit
Vessels carrying blood from the heart to the lungs and back to the heart
Systemic circuit
Vessels carrying blood from the heart to the rest of the body and back.

8. Pulmonary Circuit
Convey blood from RV pulmonary artery to the lungs, alveolar capillaries, and pulmonary veins leading from the lungs to the left atrium.
Blood flows from the right side of the heart to the lungs and back to the left side of the heart
Gas exchange happens in the capillaries in the lungs

9. Systemic Circuit
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.
Blood flows from the left side of the heart through the body tissues and back to the right side of the heart
Systemic capillaries is where materials are exchanged

10. Arteries and Arterioles
Arteries are strong, elastic vessels adapted for carrying blood under high pressure.
Arteries become smaller as they divide and give rise to arterioles.
Arterioles carry blood capillaries

11. Vessel Structure The wall of an artery consists of an Endothelium
Tunica media (smooth muscle)
Tunica externa (connective tissue).
Arteries are capable of vasoconstriction as directed by the sympathetic impulses; when impulses are inhibited, vasodilatation results.

12. Artery walls are thickest
Lumens of veinsare larger
Larger veins have valves to prevent backflow
Sleletal muscle “milks” blookinveins towared theheart
Capillaries:
Walls of capillaries aree ony once cell layer thicl to allow for exchanges between bloodandtissue
Hve only tunica intima

13. Capillaries
Capillaries are the smallest vessels, consisting only of a layer of endothelium through which substances are exchanged with tissue cells.
Capillaries join arterioles and venules.

14. Exchanges in the Capillaries
Blood entering capillaries contains high concentrations of oxygen and nutrients that diffuse out of the capillary wall and into the tissues.
Plasma proteins remain in the blood due to their large size.

15. Exchanges in the Capillaries
Hydrostatic pressure drives the passage of fluids and very small molecules out of the capillary at this point.
At the venule end, osmosis, due to the osmotic pressure of the blood, causes much of the tissue fluid to return to the bloodstream

16. Systemic Arteries

17. Aorta
The Aorta extends upward and to the right from the left ventricle. Then it curves backward and to the left. It continues down behind the heart just in front of the vertebral column, through the diaphragm, and into the abdomen.

19. Aorta
This is the main trunk of the systemic arterial circulation and is composed of 4 parts:
Ascending aorta is near the heart and inside the pericardial sac.
Aortic arch curves from the right to the left and also extends backward.

20. Aorta
Thoracic aorta lies just in front of the vertebral column behind the heart and in the space behind the pleura.
Abdominal aorta is the longest section of the aorta, spanning the abdominal cavity
Ascending aorta – leaves the left ventricle
Aortic arch –arches to the left
thoracic aorta- travels downward through the thorax
abdominal aorta – passes through the diaphragm into the abdominoplevic cavity

22. Principal Branches of the Aorta
The branches of the ascending aorta are:
Right and Left coronary arteries
( lead to the heart muscle )
Branches of the aortic arch include:
the brachiocephalic artery
Left common carotid artery
Left subclavian artery

23. Venules and Veins Venules lead from capillaries & merge to
form veins that return blood to the heart.
Veins have the same three layers as arteries (different thicknesses) and have a flap-like valve inside to prevent backflow of blood.

24. Venules and Veins
Veins are thinner and less muscular than arteries; they do not carry high-pressure blood.
Veins also function as blood reservoirs.

25. Venous Blood Flow
Blood flow through the venous system is only partially the result of heart action and instead also depends on: 1. skeletal muscle contraction
2. breathing movements
3. vasoconstriction of veins

26. Venous Blood Flow
Contractions of skeletal muscle squeeze blood back up veins one valve at a time.
Differences in thoracic and abdominal pressures draw blood back up the veins.

27. Venous System
Veins return blood to the heart after the exchange of substances has occurred in the tissues.

28. Venous System Characteristics of Venous Pathways
Larger veins parallel the courses of arteries and are named accordingly; smaller veins take irregular pathways and are unnamed.

29. Venous System
Veins from the head and upper torso drain into the superior vena cava. Veins from the lower body drain into the inferior vena cava. The vena cavae merge to join the right atrium.

30. The Venae Cavae and their Tributaries
The veins of the head, neck, upper extremities, and chest all drain into the superior vena cava, which goes to the heart.
The azygos vein drains the thorax and enters the superior vena cava before it joins the heart

31. The Hepatic Portal System
A “portal system” is a kind of detour in the pathway of venous return that transports materials directly from one organ to another.
Eg. The hepatic portal system carries blood from the abdominal organs to the liver.

32. The Hepatic Portal System
Instead of emptying their blood directly into the inferior vena cava, they deliver it to this system.
On entering the liver, the portal vein divides into a network called sinusoids.
The purpose of this system is to transport blood from the digestive organs and the spleen to the liver, so the liver cells can carry out their function. (nutrients are processed, stored, and released as needed by the body.

34. Anastomoses
A communication between two vessels is called an anastomosis. By means of arterial anastomoses, blood reaches vital organs by more than one route.
Examples:
Circle of Willis
The palmar arch in the hand
The mesenteric arches in the intestines
Arterial arches in the foot

35. The Dynamics of Blood Flow
The flow of blood is carefully regulated to supply the needs of the tissues without unnecessary burden on the heart.
The brain, liver, and kidneys require large quantities of blood, even at rest.
Blood is affected by vasodilation, vasoconstriction.

36. Blood Flow
The requirements of some tissues, such as those of skeletal muscles and digestive organs, increase greatly during periods of activity.
The volume of blood flowing to a particular organ can be regulated by changing the size of the blood vessels supplying that organ

37. Blood Flow
Vasodilation is an increase in the diameter of a blood vessel. This allows for the delivery of more blood to an area.
Vasoconstriction is a decrease in the diameter of blood vessel, causing a decrease in blood flow.
These vasomotor activities result from the contraction or relaxation of smooth muscle in the walls of the blood vessels, mainly the arterioles.

38. Pulse and Pulse Rate
The ventricles pump blood into the arteries regularly about times a minute (in the adult). The force of ventricular contraction starts a wave of increased pressure that begins at the heart and travels along the arteries.
This wave, called the pulse, can be felt in any artery that is relatively close to the surface.

39. Pulse rate Various factors may influence the pulse rate:
Pulse is faster in small people than in large people and usually is slightly faster in women.
Muscular activity
Emotional disturbances
Infections

40. Pulse and Pulse Rate
Normally, the pulse rate is the same as the heartbeat
If a heartbeat is abnormally weak or if the artery is obstructed, the heartbeat may not be detected as a pulse.
In checking a pulse, it is important to gauge the strength as well as the regularity and rate.

41. Blood Pressure
Blood pressure is the force of blood against the inner walls of blood vessels anywhere in the cardiovascular system, although the term "blood pressure" usually refers to arterial pressure.

42. Arterial Blood Pressure
Arterial blood pressure rises and falls following a pattern established by the cardiac cycle
During ventricular contraction, arterial pressure is at its highest (systolic pressure).
When ventricles are relaxing, arterial pressure is at its lowest (diastolic pressure).

43. Arterial Blood Pressure
The surge of blood that occurs with ventricular contraction can be felt at certain points in the body as a pulse.

44. Factors that Influence Arterial Blood Pressure
Arterial pressure depends on:
Heart action
Blood volume
Resistance to flow
Blood viscosity.

45. Factors that Influence Arterial BP
Heart Action
Heart action is dependent upon stroke volume and heart rate (together called cardiac output); if cardiac output increases, so does blood pressure
Blood Volume
Blood pressure is normally directly proportional to the volume of blood within the cardiovascular system.
Blood volume varies with age, body size , and gender

46. Factors that Influence Arterial BP
Peripheral Resistance
Friction between blood and the walls of blood vessels is a force called peripheral resistance.
As peripheral resistance increases, such as during sympathetic constriction of blood vessels, blood pressure increases.

47. Factors that Influence Arterial BP
Blood Viscosity: = thickness of the blood
eg. Milkshake vs milk
↑ blood viscosity ↑ BP
Eg. Caused by: dehydration, loss of plasma volume, or increased # RBCs

48. Blood Viscosity
The greater the viscosity of blood, the greater its resistance to flowing, and the greater the blood pressure.

49. Control of BP
Blood pressure is determined by cardiac output and peripheral resistance. The body maintains normal blood pressure by adjusting cardiac output and peripheral resistance

50. Control of BP
Cardiac output depends on stroke volume and heart rate, and a number of factors can affect these actions. The volume of blood that enters the right atrium is normally equal to the volume leaving the left ventricle.

51. Control of BP
If arterial pressure increases, the cardiac center of the medulla oblongata sends parasympathetic impulses to slow heart rate. If arterial pressure drops, the medulla oblongata sends sympathetic impulses to increase heart rate to adjust blood pressure.

52. Control of BP
The vasomotor center of the medulla oblongata can adjust the sympathetic impulses to smooth muscles in arteriole walls, adjusting blood pressure. Certain chemicals, such as carbon dioxide, oxygen, and hydrogen ions, can also affect peripheral resistance.

53. Control of BP
Other factors, such as emotional upset, exercise, and a rise in temperature can result in increased cardiac output and increased blood pressure.

54. Measurement of BP May prove a valuable guide
Instrument used is called a sphygmomanometer
Two variables:
Systolic pressure
Diastolic pressure
Reported as a fraction
Experience is required to ensure an accurate reading
BP varies throughout the day.