1. Circulation and Gas Exchange

2. Trading Places Occurs across a moist cell membrane
Must be dissolved in water to enter the cell membrane (osmosis)
May need internal transport if cells are isolated
Animals gain oxygen and nutrients while shedding carbon dioxide and wastes

3. Trading Places Diffusion too slow
time of diffusion is proportional to the square distance the chemical must travel
Two Solutions 
Body size and shape keep many or all cells in direct contact with the environment
Circulation
reduces the distance a substance must diffuse to enter or leave a cell
Fluid is moved between each cell’s immediate surroundings andthe tissues where exchange with the environment occurs

4. Gastrovascular Cavities
Cnidarians and Platyhelminthes
No specific internal transport (circulatory) system
Functions in digestion and distribution of nutrients
Gastrodermal cells have direct access to nutrients
nutrients only have short distance to diffuse

5. General Properties of Circulatory Systems
3 basic components
Heart
A muscular pump
Circulatory fluid
Set of interconnecting vessels

6. Open Circulatory System
Hemolymph bathes the internal organs directly while moving through sinuses
Circulation results from contraction of the dorsal vessel (heart) and body movements
Relaxation of the “heart” draws the blood back into the ostia (pores)
Not energy expensive
Arthropods and most mollusks

7. Closed Circulatory System
Blood is confined to vessels and is distinct from the interstitial fluid
Heart pumps blood into larger vessels
Major vessels branch
In organs, nutrients are exchanged through capillaries b/w blood and interstitial fluid
Effective delivery of O2
Annelids, squids, octopus, vertebrates

8. Organization of Vertebrate Circulatory Systems
Cardiovascular system
Arteries  Arterioles  Capillaries  Venules  Veins
Capillary beds
Networks of capillaries that infiltrate every tissue

9. Organization of Vertebrate Circulatory Systems
Heart has at least 2 chambers
Atria
Receives the blood
Ventricle
Pumping out blood

10. Organization of Vertebrate Circulatory Systems
Single Circulation
Blood only passes through the heart once per circuit
Double Circulation
Blood passes through two circuits
Pulmonary circuit
Systemic circuit
Pulmocutaneous circuit
Capillaries in both skin & lungs

11. Double Circulation in Vertebrates

12. Mammalian Circulation
RV contracts  blood to lungs via pulmonary arteries
Blood exchanges O2 and CO2 in the capillary beds of the lungs
Pulmonary veins  LA  bicuspid  LV pumps blood into the systemic circuit via the aorta
First 2 branches of the aorta are coronary arteries to supply heart muscle
Diffusion between capillaries from blood to tissues and tissues to blood
Capillaries join venules  veins  superior/inferior vena cava  RA  tricuspid valve  RV

13. Mammalian Heart and Circulation

14. Mammalian Heart…a closer look
Cardiac cycle
Complete sequence of contraction and relaxation
Systole
heart contracts and pumps the blood
Diastole
heart relaxes and heart fills with blood

15. Mammalian Heart…a closer look
Cardiac output
Volume of blood each ventricle pumps per minute
Average is 5 L/min
Determined by two factors
Heart rate
The number of heartbeats per minute
Stroke volume
Amount of blood pumped by a ventricle in a single contraction
Average in a human is 70 mL

16. Mammalian Heart…a closer look
Valves
prevent backflow of blood
Atrioventricular valves (between atria and ventricles)
Bicuspid and tricuspid
Semilunar valves (between ventricles and arteries)
Aortic and pulmonary
Heart Murmur
defect in one or more of the valves that allows backflow to occur

17. Maintaining the Heart’s Rhythmic Beat
Myogenic (autorhythmic) cells
self-excitable
Sinoatrial node (SA node)
pacemaker
Cluster of cells that controls the rhythm
contracts and stimulates the AV node
can be influenced by outside forces
Atrioventricular node
Delay of 0.1 second before stimulating specialized muscle fibers called bundle branches and Purkinje fibers

18. Blood Vessel Structure and Function
Lumen lined with endothelium
Smooth to minimize friction

19. Blood Flow Velocity
Blood slows as it moves from arteries to arterioles to capillaries
Total cross sectional area is much greater in capillary beds

20. Blood Pressure

21. Blood Pressure
Hydrostatic force that blood exerts against a vessel wall
Pressure greater in arteries and during systole
Systolic
top #
Arterial blood pressure is highest when the heart contracts during ventricular systole
Diastolic
bottom #

22. A sphygmomanometer, an inflatable cuff attached to a pressure gauge, measures blood pressure fluctuations in the brachial artery of the arm over the cardiac cycle.
The arterial blood pressure of a healthy human oscillates between about 120 mm Hg at systole and 70 mm Hg at diastole.

23. Blood Pressure Regulation
Physical/emotional stress triggers nervous and hormonal responses
Nitric Oxide
Major inducer of vasodilation
Endothelin
Major inducer of vasoconstriction

24. Blood Pressure and Gravity
Gravity is a major influence
Return of venous blood to heart –
Rhythmic contractions of smooth muscle
Contraction of skeletal muscles
Change in pressure in thoracic cavity

25. Capillary Function
Only 5-10% of capillaries have blood in them at any one given time
Each tissue has so many capillaries that tissues have a blood supply all of the time

26. Capillary Function
Fluid exchange b/w capillaries and interstitial fluid
Endocytosis and exocytosis
Simple diffusion
Blood pressure drives fluids out of capillaries
Presence of blood proteins pulls fluid back in

27. Fluid Return by Lymphatic System
Lose 4-8 L of fluid from capillaries to tissues daily
Return to the blood via the lymphatic system
Fluid lost by capillaries  lymph
Lymph nodes surround lymph vessels
Filter the lymph and house cells that attack viruses and bacteria

28. Blood

29. Cellular Elements Erythrocytes (red blood cells) Oxygen transport
Biconcave disks
Lack nuclei
Contain hemoglobin
Iron containing protein that transports the O2
Sickle cell anemia

30. Cellular Elements Leukocytes (white blood cells) 5 major types
Fight infection
Phagocytic
Develop specialized B cells and T cells to mount immune responses against foreign substances
Thrombocytes (platelets)
cellular fragments
Structural and molecular functions in blood clotting

31. Blood Clotting

32. Stem Cells and Replacement of Cellular Elements
Multipotent; dedicated to replenishing body’s blood cell population
Erythropoietin (EPO)
Hormone from kidney
Stimulates RBC production
Negative feedback

33. Cardiovascular Disease
Cholesterol metabolism
Low Density Lipoprotein (LDL)
Delivers cholesterol to cells for membrane production
High Density Lipoprotein (HDL)
Scavenges extra cholesterol for return to the liver
Inflammation

34. Cardiovascular Diseases
Atherosclerosis
chronic cardiovascular disease characterized by plaques that develop on the inner walls of arteries and narrow the width of the vessel
Thrombus
a blood clot that blocks a major vessel
embolus – moving clot

35. Cardiovascular Diseases
Ateriosclerosis
degenerative condition of the arteries where plaque hardens
Hypertension
high blood pressure
may promote atherosclerosis

36. Cardiovascular Diseases
Heart attack
death of cardiac muscle resulting from prolonged blockage of one or more coronary arteries

37. Cardiovascular Diseases
Stroke
death of nervous tissue in the brain often resulting from blockage of arteries in the brain