Chapter 11 The Circulatory System

1. Chapter 11The Circulatory System Part D

2. Arterial Supply of the Brain • Internal carotid arteries divide into • Anterior and middle cerebral arteries • These arteries supply most of the cerebrum • Vertebral arteries join once within the skull to form the basilar artery • Basilar artery serves the brain stem and cerebellum

3. Arterial Supply of the Brain • Posterior cerebral arteries form from the division of the basilar artery • These arteries supply the posterior cerebrum

4. Circle of Willis Anterior and posterior blood supplies are united by small communicating arterial branches Result—complete circle of connecting blood vessels called cerebral arterial circle or circle of Willis

5. Arterial Supply of the Brain Figure 11.13

6. Fetal Circulation • Fetus receives exchanges of gases, nutrients, and wastes through the placenta • Umbilical cord contains three vessels • Umbilical vein—carries blood rich in nutrients and oxygen to the fetus • Umbilical arteries (2)—carry carbon dioxide and debris-laden blood from fetus to placenta

7. Fetal Circulation • Blood flow bypasses the liver through the ductus venosus and enters the inferior vena cava  right atrium of heart • Blood flow bypasses the lungs • Blood entering right atrium is shunted directly into the left atrium through the foramen ovale • Ductus arteriosus connects the aorta and pulmonary trunk (becomes ligamentum arteriosum at birth)

8. Fetal Circulation • Ductus venosus – bypasses liver to heart → R atrium → foramen ovale opens to L atrium → blood that gets into R ventricle → pulmonary trunk → ductus arteriosus → aorta & pulmonary trunk connected → systemic circulation → placenta • At birth: • Foramen ovale closes • Ductus arteriosus collapses • Revert to normal circulation

9. Quick Check!! • 17. Through what organ does the fetus receive gases & nutrients: • A. umbilical arteries • B. ductusarteriosus • C. uterus • D. placenta

10. Fetal Circulation

11. Quick Check!! • 18. Blood entering the fetal right atrium is shunted directly into the left atrium through the: • A. ductusarteriosus • B. ductusvenosus • C. foramen ovale • D. fossaovalis

12. Hepatic Portal Circulation • Veins of hepatic portal circulation drain • Digestive organs • Spleen • Pancreas • Hepatic portal vein carries this blood to the liver • Liver helps maintain proper glucose, fat, and protein concentrations in blood

13. Hepatic Portal Circulation • Major vessels of hepatic portal circulation • Inferior and superior mesenteric veins • Splenic vein • Left gastric vein

14. Hepatic Portal Circulation Figure 11.16

15. Hepatic Portal Circulation Figure 11.14

16. Quick Check!! • 19. What does the hepatic portal vein deliver blood to? • A. liver • B. spleen • C. intestines • D. pancreas

17. Pulse • Pulse – pressure wave of blood • Monitored at “pressure points” where pulse is easily palpated • 70-76 beats/minute Figure 11.16

18. Pulse

19. Blood Pressure • Measurements by health professionals are made on the pressure in large arteries • Systolic – pressure at the peak of ventricular contraction • Diastolic – pressure when ventricles relax • Write systolic pressure first and diastolic last (120/80 mm Hg) • Pressure in blood vessels decreases as the distance away from the heart increases

20. Comparison of Blood Pressures in Different Vessels Figure 11.19

21. Quick Check!!! • 20. The lowest blood pressure would be found in the: • A. aorta • B. arteries • C. capillaries • D. veins • E. vena cava

22. BP – pressure blood exerts against inner wall of vessels • Systolic: 120 mmHg • Diastolic: 80 mmHg • Ascultatory – use stethoscope to listen to brachial artery

23. Measuring Arterial Blood Pressure Figure 11.20a

24. Measuring Arterial Blood Pressure Figure 11.20b

25. Measuring Arterial Blood Pressure Figure 11.20c

26. Measuring Arterial Blood Pressure Figure 11.20d

27. Blood Pressure: Effects of Factors • BP is blood pressure • BP is affected by age, weight, time of day, exercise, body position, emotional state • CO is the amount of blood pumped out of the left ventricle per minute • PR is peripheral resistance, or the amount of friction blood encounters as it flows through vessels • Narrowing of blood vessels and increased blood volume increases PR

28. Blood pressure = cardiac output x peripheral resistance • (cardiac output = stroke volume x heart rate)

29. 21. The amount of blood pumped out of the left ventricle per minute: • A. BP • B. CO • C. PR • D. HR

30. Blood Pressure: Effects of Factors • Neural factors • Autonomic nervous system adjustments (adrenal medulla -sympathetic division) – constricts vessels causing ↑ PR (peripheral resistance) • Atherosclerosis causes ↑ PR • Renal factors • Regulation by altering blood volume • ↑ volume or viscosity causes ↑ PR • Urinate water to ↓ PR • Renin – enzyme produced by kidneys • Renin → angiotensis II → vasoconstriction

31. Blood Pressure: Effects of Factors • Temperature • Heat has a vasodilation effect • Cold has a vasoconstricting effect • Chemicals • Various substances can cause increases or decreases • Epinephrine ↑ heart rate & BP • Nicotine ↑ BP • Alcohol & histamines ↓BP & cause vasodilation • Diet

32. Factors Determining Blood Pressure Figure 11.21

33. Variations in Blood Pressure • Human normal range is variable • Normal • 140–110 mm Hg systolic • 80–75 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

34. Capillary Exchange • Substances exchanged due to concentration gradients • Oxygen and nutrients leave the blood • Carbon dioxide and other wastes leave the cells

35. Capillary Exchange: Mechanisms • Direct diffusion across plasma membranes – into interstitial fluid • Endocytosis or exocytosis – lipid insoluble substances • Some capillaries have gaps (intercellular clefts) • Plasma membrane not joined by tight junctions • Fenestrations of some capillaries • Fenestrations = pores