AP 110 Fundamentals of Anatomy and Physiology

1. AP 110Fundamentals 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.

7. Blood Circuits • Pulmonarycircuit • 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.

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.

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.

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 diffuseoutof 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

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 valveinside 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. 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. The Hepatic Portal System

34. 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 Anastomoses

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 70-80 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. 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 Pulse rate

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.