1. Circulatory Systems: Pumps, Vessels, and Blood
A circulatory system is composed of a pump (heart), fluid (blood), and conduits (blood vessels).
This is also called a cardiovascular system.

2. Every organism must exchange materials with its environment
Overview: Trading Places
Every organism must exchange materials with its environment
Exchanges ultimately occur at the cellular level
In unicellular organisms, these exchanges occur directly with the environment 2

3. Concept 42.1: Circulatory systems link exchange surfaces with cells throughout the body
In small and/or thin animals, cells can exchange materials directly with the surrounding medium
In most animals, transport systems connect the organs of exchange with the body cells
Most complex animals have internal transport systems that circulate fluid 3

4. Circulatory Systems: Pumps, Vessels, and Blood
Some simple aquatic animals do not have circulatory systems.
In small animals, nutrients, gases, and wastes can diffuse between the cells and the environment and a circulatory system is not needed.
Some aquatic animals have a flat body shape or a highly-branched gastrovascular cavity (cnidaria) to provide maximum surface area for exchange.
Larger animals with many cell layers must rely on extracellular tissue fluids to carry materials to and from cells.

5. Not very efficient -as hemolymph under low pressure
Figure Open Circulatory Systems
Not very efficient -as hemolymph under low pressure
-not able to be directed to tissues that may need more oxygen

6. Figure 49.2 A Closed Circulatory System

7. Circulatory Systems: Pumps, Vessels, and Blood
Closed systems have advantages over open systems:
Blood flow, nutrient delivery and waste removal are more rapid.
Closed systems can direct the blood to specific tissues.
Cellular elements and large molecules that aid in transport can be kept within the vessels.
Closed systems generally support higher levels of metabolic activities.
Insects are an exception to this rule, but they do not rely on their circulatory systems for gas exchange.

8. REPTILES (EXCEPT BIRDS) Pulmocutaneous circuit
Vertebrate circulatory systems
FISHES
AMPHIBIANS
REPTILES (EXCEPT BIRDS)
MAMMALS AND BIRDS
Systemic capillaries
Lung capillaries
Lung and skin capillaries
Gill capillaries
Right
Left
Systemic circuit
Pulmocutaneous circuit
Pulmonary circuit
Systemic circulation
Vein
Atrium (A)
Heart: ventricle (V)
Artery
Gill circulation A V
Systemic aorta
Right systemic aorta
Figure 42.4

9. Vertebrate Circulatory Systems
The four-chambered hearts of birds and mammals completely separate the pulmonary and systemic circuits.
The advantages of separate circuits are:
Oxygenated and deoxygenated blood cannot mix.
Gas exchange is maximized because the lungs receive only blood with low O2 and high CO2 content.
The separate circuits can operate at different pressures.

10. Figure 49.3 The Human Heart and Circulation (Part 2)

11. The mammalian cardiovascular system
Pulmonary
vein
Right atrium
Right ventricle
Posterior
vena cava
Capillaries of
abdominal organs
and hind limbs
Aorta
Left ventricle
Left atrium
artery
Capillaries
of left lung
head and
forelimbs
Anterior
of right lung
Figure 42.5 1 10 11 5 4 6 2 9 3 7 8

12. The heart contracts and relaxes
In a rhythmic cycle called the cardiac cycle
The contraction, or pumping, phase of the cycle
Is called systole
The relaxation, or filling, phase of the cycle
Is called diastole

13. The cardiac cycle Figure 42.7 Semilunar valves closed AV valves open
AV valves closed
Semilunar valves open
Atrial and ventricular diastole 1
Atrial systole; ventricular diastole 2
Ventricular systole; atrial diastole 3
0.1 sec
0.3 sec
0.4 sec

14. The heart rate, also called the pulse, is the number of beats per minute
The stroke volume is the amount of blood pumped in a single contraction
The cardiac output is the volume of blood pumped into the systemic circulation per minute and depends on both the heart rate and stroke volume 14

15. Maintaining the Heart’s Rhythmic Beat
Some cardiac muscle cells are self-excitable
Meaning they contract without any signal from the nervous system. The electrical impulse is then rapidly conducted due to the branching nature of cardiac muscle and the presence of intercalated discs (which have gap junctions to allow rapid flow of charge)
The impulses that travel during the cardiac cycle
Can be recorded as an electrocardiogram (ECG or EKG)
The pacemaker is influenced by
Nerves, hormones, body temperature, and exercise
The autonomic nervous system controls heart rate by influencing the rate at which pacemaker cells gradually depolarize.
Acetylcholine and norepinephrine from the parasympathetic and sympathetic nerve endings slow and increase the rate, respectively

16. The control of heart rhythm
Figure 42.8
SA node (pacemaker)
AV node
Bundle branches
Heart apex
Purkinje fibers 2
Signals are delayed
at AV node. 1
Pacemaker generates wave of signals to contract. 3
Signals pass
to heart apex. 4
Signals spread
Throughout ventricles.
ECG

17. Artery Vein SEM 100 µm Valve Basal lamina Endothelium Endothelium
Fig
Artery
Vein
SEM
100 µm
Valve
Basal lamina
Endothelium
Endothelium
Smooth
muscle
Smooth
muscle
Connective
tissue
Connective
tissue
Capillary
Artery
Vein
Figure The structure of blood vessels
Arteriole
Venule
15 µm
Red blood cell
Capillary LM 17

18. Capillaries have thin walls, the endothelium plus its basement membrane, to facilitate the exchange of materials
Arteries and veins have an endothelium, smooth muscle, and connective tissue
Structural differences in arteries, veins, and capillaries correlate with their different functions
Arteries have thicker walls than veins to accommodate the high pressure of blood pumped from the heart 18

19. All blood vessels
Are built of similar tissues
Have three similar layers

20. Figure 49.14 Atherosclerotic Plaque (Part 1)

21. Figure 49.14 Atherosclerotic Plaque (Part 2)

22. The Vascular System: Arteries, Capillaries, and Veins
If the coronary arteries are affected, blood supply to the heart decreases.
A thrombus here (coronary thrombosis) can block an artery, causing a heart attack (myocardial infarction, or MI).
If part of the thrombus breaks away (an embolism), lodges in the brain, and blocks blood flow, stroke may occur.
The best approach to reducing heart disease is prevention.
Risk factors include high-fat/high-cholesterol diets, smoking, a sedentary life style, and obesity.

23. Blood tends to accumulate in veins
Blood tends to accumulate in veins. Veins are called capacitance vessels because of their high capacity to store blood.
Direction of blood flow in vein (toward heart)
Valve (open)
Skeletal muscle
Valve (closed)
Pressure in veins is very low, Contraction of skeletal muscles pushes blood toward the heart because one-way valves in veins prevent backflow.
If veins become stretched, the valves no longer do their job and varicose veins develop.

24. The Vascular System: Arteries, Capillaries, and Veins
During walking or running, the legs act as auxiliary vascular pumps and return blood to the heart from the veins of the lower body.
A greater volume of blood is returned to the heart, which stretches the cardiac muscle cells, and the heart contracts more forcefully. This is known as the Frank-Starling law.
Breathing also helps return venous blood by creating negative pressure (suction), which pulls blood and lymph toward the chest area.
In large veins near the heart, smooth muscles also contract with exercise, increasing venous return and cardiac output.

25. Physical laws governing the movement of fluids through pipes
Influence blood flow and blood pressure
The velocity of blood flow varies in the circulatory system
And is slowest in the capillary beds as a result of the high resistance and large total cross-sectional area

26. Blood pressure
Is the hydrostatic pressure that blood exerts against the wall of a vessel
Systolic pressure
Is the pressure in the arteries during ventricular systole
Is the highest pressure in the arteries
Diastolic pressure
Is the pressure in the arteries during diastole
Is lower than systolic pressure

27. Two mechanisms
Regulate the distribution of blood in capillary beds
In one mechanism
Contraction of the smooth muscle layer in the wall of an arteriole constricts the vessel

28. In a second mechanism
Precapillary sphincters control the flow of blood between arterioles and venules

29. Figure 49.12 Starling’s Forces (Part 1)

30. Figure 49.12 Starling’s Forces (Part 2)

31. The Vascular System: Arteries, Capillaries, and Veins
The medical phenomenon called edema (tissue swelling) in certain diseases, or the inflammation accompanying injury or an allergic reaction, supports this model.
However, edema does not occur during strenuous exercise, for example, or in birds, which have higher arteriole pressure and lower osmotic pressure than mammals.

32. The Vascular System: Arteries, Capillaries, and Veins
CO2 and bicarbonate ions (HCO3–) are major factors that pull water back into the capillaries.
As blood flows through the capillary, CO2 diffuses into the plasma and is converted into HCO3–.
The increasing bicarbonate concentration causes osmotic pressure to be higher at the venous end, especially during exercise.
In fact, CO2 and HCO3– are the major factors that pull water back into the capillaries, not colloidal osmotic pressure.

33. Figure 49.15 The Composition of Blood

34. Figure 49.16 Blood Clotting (Part 1)

35. Blood pressure is determined
partly by cardiac output
And partly by peripheral resistance due to variable constriction of the arterioles

36. Figure 49.18 Control of Blood Pressure through Vascular Resistance

37. Control and Regulation of Circulation
When atria are receiving too much venous return they release a hormone called atrial natriuretic factor, which stimulates the kidney to excrete sodium and water, resulting in a reduced blood volume.

38. Figure 49.19 Regulating Blood Pressure

39. Control and Regulation of Circulation
Several adaptations permit the air-breathing seal to remain under water for long periods of time.
Seals have greater blood volume, greater blood O2 carrying capacity, and more myoglobin in their muscles than do humans.
The diving reflex is the most important adaptation.
During a dive, the heart rate slows, and all major blood vessels are constricted except those critical to survival under water.
Metabolic rate slows, and tissues switch to glycolytic (anaerobic) metabolism.

40. Figure 49.20 The Diving Reflex