1. Heart and Blood Vessels8
Heart and Blood Vessels 1

2. Blood Vessels Transport Blood
Arteries
Carry blood away from the heart
Transport blood under high pressure
Thick-walled
Capillaries
Exchange solutes and water with cells of the body
Microscopic
Veins
Return blood to the heart
Thin-walled

3. Outer layer: Middle layer: Inner layer: Vein Artery Venule Arteriole
Figure 8.1
Direction of
blood flow
Outer layer:
Connective
tissue
Middle layer:
Smooth
muscle with
elastic fibers
Inner layer:
Endothelium
Vein
Artery
Connective tissue
Figure 8.1 The structures of blood vessels in the human body.
Smooth muscle
Endothelium
Venule
Arteriole
Capillary
Epithelial cells of
capillary endothelium
Tissue cells 3

4. Arteries Transport Blood Away From Heart
Structure
Thick-walled, three layers
Innermost layer: endothelium of squamous epithelial cells
Middle layer: smooth muscle
Outer layer: connective tissue
Function
Arteries carry blood away from heart
Carry blood under pressure

5. Arteries Transport Blood Away From the Heart
Aneurism—defect in arterial wall
Ballooning of the arterial wall
Some bulge inward, obstructing flow
Others bulge outward
Often develop slowly over time
Often symptomless, until they rupture
Rupture of aortic aneurism—rapidly fatal
May be detected by careful screening and surgically repaired

6. Arterioles and Precapillary Sphincters Regulate Blood Flow
Heart  Arteries  Arterioles  Capillaries
Arterioles: smallest arteries
Precapillary sphincters: control blood flow from arterioles into capillaries
Vasodilation:
Relaxation of vascular smooth muscle
Increases blood flow to capillaries
Vasoconstriction:
Contraction of vascular smooth muscle
Decreases blood flow to capillaries

7. Relaxed Constricted precapillary precapillary sphincters sphincters
Figure 8.2
Relaxed
precapillary
sphincters
Constricted
precapillary
sphincters
Arteriole
Capillaries
Figure 8.2 Precapillary sphincters control the flow of blood into individual capillaries.
Small vein (venule) 7

8. Capillaries: Where Blood Exchanges Substances with Tissues
Structure
Smallest blood vessels, microscopic
Thin-walled: one cell-layer thick
Porous
Capillary beds: extensive networks of capillaries
Function: selective exchange of substances with the interstitial fluid

9. A medium-magnification view showing a rich network of capillaries
Figure 8.3
Capillary cell
Pores through cells
Slit between cells
A medium-magnification
view showing a rich
network of capillaries
surrounding and
interconnecting small
arteries and veins.
Nucleus
Figure 8.3 Capillaries.
RBC
A higher magnification showing
a single branching capillary.
Notice the red blood cells traveling
single file in the capillary.
The structure of a capillary. 9

10. Precapillary sphincter
Figure 8.4
Precapillary sphincter
Capillary
RBCs, most proteins
Fluid (water)
O2, nutrients,
raw materials
CO2, wastes
Arteriole
Venule
Figure 8.4 The general pattern of movement between capillaries, the interstitial fluid, and cells.
Tissue cell 10

11. Lymphatic System Helps Maintain Blood Volume
Function
Maintains blood volume
Returns excess interstitial fluid to circulatory system
Also functions in immune defenses
Structure
Blind-ended capillaries
Lymphatic vessels (similar to venous system)
Lymph—derived from interstitial fluid

12. Veins Return Blood to the Heart
Structure
Three layers, thin-walled
Larger lumen than arteries
High distensibility
Functions
Carry blood toward the heart
Blood flow
Capillaries  Venules  Veins  Heart
Serve as blood volume reservoir

13. Veins Return Blood to the Heart
Three Mechanisms assisting in blood return
Contraction of skeletal muscles
One-way valves permit only one-way blood flow
Pressure changes associated with breathing push blood toward the heart

14. Calf muscles relaxed Calf muscles contracted
Figure 8.5
Valve
(open)
One-way
valves
(closed)
Figure 8.5 The skeletal muscle pump.
Calf muscles
relaxed
Calf muscles
contracted 14

15. Figure 8.6
Figure 8.6 A human heart. 15

16. Aortic semilunar valve Left atrioventricular (AV) valve Right atrium
Figure 8.7
Aorta
Superior
vena cava
Left pulmonary artery
Right pulmonary
artery
Pulmonary trunk
Left pulmonary veins
Left atrium
Pulmonary
semilunar valve
Aortic semilunar valve
Left atrioventricular
(AV) valve
Right atrium
Left ventricle
Right
atrioventricular
(AV) valve
Figure 8.7 A view of the heart showing major blood vessels, chambers, and valves.
Chordae tendineae
Papillary muscles
Septum
Right ventricle
Epicardium
Inferior vena cava
Myocardium
Endocardium 16

17. The Heart Is Mostly Muscle
Surrounded by fibrous sac—pericardium
Protects and anchors the heart
Layers of the heart
Epicardium: thin layer of epithelial and connective tissue
Myocardium: thick layer of cardiac muscle
Electrical signals flow directly from cell to cell
This is what contracts when the heart beats
Endocardium: thin layer of endothelial tissue
Continuous with lining of blood vessels

18. The Heart Has Four Chambers and Four Valves
Two atria: upper chambers
Two ventricles: lower chambers
Septum, muscular partition separates right and left sides of the heart
Four valves—prevent backflow
Two atrioventricular (AV) valves
Tricuspid valve (right side)
Bicuspid (mitral) valve (left side)
Two semilunar valves
Pulmonary valve
Aortic valve

19. The Pulmonary Circuit Provides for Gas Exchange
Deoxygenated blood from the body travels through the vena cava to the right atrium
Through the right AV valve into the right ventricle
Through the pulmonary semilunar valve into the pulmonary trunk and the lungs
Blood is oxygenated and CO2 is given up within pulmonary capillaries
Oxygenated blood travels through the pulmonary veins into the left atrium
Through the left AV valve into the left ventricle

20. The Systemic Circuit Serves the Rest of the Body
Oxygenated blood travels from the left ventricle through the aortic semilunar valve into the aorta
Through branching arteries and arterioles to tissues
Through the arterioles to capillaries
Within capillaries, nutrients and oxygen are delivered and wastes are picked up
From capillaries into venules and veins
To the vena cava and into the right atrium

21. Systemic Circuit Figure 8.8 Head and upper limbs
Lung
capillaries
Pulmonary
Circuit
Lung
capillaries
Heart
Aorta
Figure 8.8 A schematic representation of the human cardiovascular system showing the separate pulmonary and systemic circuits.
Torso and
Lower limbs 21

22. Jugular vein Subclavian vein Carotid artery Subclavian artery Superior
Figure 8.9
Jugular vein
Carotid artery
Subclavian vein
Superior
vena cava
Subclavian artery
Inferior
vena cava
Aorta
Renal artery
Renal vein
Common
iliac vein
Femoral vein
Figure 8.9 Some of the major arteries and veins in the human body.
Femoral artery
Common
iliac artery
Great saphenous
vein 22

23. The Systematic Circuit Serves the Rest of the Body
Coronary arteries
Arteries that supply the heart muscle itself
Supply the myocardium
Small diameter—may become partially or completely blocked by atherosclerosis

24. Aorta Superior vena cava Pulmonary trunk Cardiac vein Left coronary
Figure 8.10
Aorta
Superior
vena cava
Pulmonary
trunk
Cardiac
vein
Left
coronary
artery
Right
coronary
artery
Figure 8.10 Blood vessels of the heart.
Cardiac
veins
Inferior
vena cava 24

25. The Cardiac Cycle: The Heart Contracts and Relaxes
Atrial systole
Both atria contract
AV valves open, semilunar valves are closed
Ventricles fill
Ventricular systole
Both ventricles contract
AV valves close, semilunar valves open
Diastole
Both atria and ventricles relax
Semilunar valves close

26. Diastole Systole Atrial systole. Both atria Diastole. The ventricles
Figure 8.11
Right atrium
Left atrium
Aortic semilunar valve
Pulmonary
semilunar valve
Left AV valve
Right AV valve
Left ventricle
Right ventricle
Atrial systole. Both atria
contract, forcing blood
into the ventricles. The AV
valves are open, and the
semilunar valves are
closed.
0.1 second
Diastole
Systole
0.4 second
Aorta
Pulmonary trunk
Figure 8.11 The cardiac cycle.
0.3 second
Diastole. The ventricles
relax and begin to fill
passively with blood
through the open AV
valves. The semilunar
valves are closed, and the
atria remain relaxed.
Ventricular systole. Both ventricles
contract, causing the AV valves to
close and the semilunar valves to open.
Blood is ejected into the pulmonary
trunk and aorta. The atria relax. 26

27. Heart Sounds Reflect Closing Heart Valves
Lub-dub heart sound
Lub: closing of both AV valves during ventricular systole
Dub: closing of both semilunar valves during ventricular diastole
Heart murmurs
Caused when blood flow is disturbed
May be a sign of a defective valve

28. Cardiac Conduction System Coordinates Contraction
Sinoatrial (SA) node—small mass of cardiac cells in upper right atrium
Cardiac pacemaker
Initiates the heartbeat spontaneously
Pace can be modified by nervous system
Atrioventricular (AV) node
Located between atria and ventricles
Relays impulse
Atrioventricular (AV) bundle and Purkinje fibers
Located in septum and ventricles
Carry impulse to ventricles

29. Sinoatrial (SA) node Atrioventricular (AV) node AV bundle
Figure 8.13
Sinoatrial
(SA) node
Atrioventricular
(AV) node
AV bundle
Figure 8.13 The cardiac conduction system.
Bundle branches
Purkinje fibers 29

30. Electrocardiogram (EKG/ECG) Records the Heart’s Electrical Activity
Tracks the electrical activity of the heart
A healthy heart produces a characteristic pattern
Three formations
P wave: impulse across atria
QRS complex: spread of impulse down septum, around ventricles in Purkinje fibers
T wave: end of electrical activity in ventricles
EKGs can detect
Arrhythmias
Ventricular fibrillation

31. R T P Q S An ECG being recorded. A normal ECG recording.
Figure 8.14
An ECG being recorded. R T P Q S
Figure 8.14 The ECG is a tool for diagnosing heart arrhythmias.
A normal ECG recording.
Ventricular fibrillation. 31

32. Blood Exerts Pressure Against Vessel Walls
The force that the blood exerts on the wall of the blood vessels
Systolic pressure: highest pressure, as blood is ejected during ventricular systole
Diastolic pressure: lowest pressure, during ventricular diastole
Measurement
Sphygmomanometer: device used to measure blood pressure
“Normal” readings
Systolic pressure <120 mmHg
Diastolic pressure <80 mmHg

33. Systolic pressure Diastolic pressure Blood pressure (mm Hg) Veins
Figure 8.15
Systolic
pressure
120
Blood pressure (mm Hg) 80
Diastolic
pressure 40
Figure 8.15 Blood pressure in different segments of the vascular system.
Veins
Arteries
Arterioles
Venules
Capillaries 33

34. A schematic representation of the pulses of
Figure 8.16
140
Cuff pressure
Blood pressure 1
120
100
Column of mercury
indicating pressure
in mm Hg
Blood pressure (mm Hg) 80 2 60 2 4 6 8 10
Sphygmomanometer:
Time (seconds)
Squeezable bulb
A schematic representation of the pulses of
arterial blood pressure superimposed over
the steadily declining cuff pressure. Systolic
pressure is recorded at cuff pressure 1 when
sounds are first heard. Diastolic pressure is
recorded at cuff pressure 2 when sounds cease.
Inflatable
rubber cuff
Air valve
Figure 8.16 How blood pressure is measured.
Artery
Stethoscope
A clinician inflates the cuff with air and then allows the
pressure in the cuff to fall gradually while using a
stethoscope to listen for the sounds of blood movement
through the artery. 34

35. Hypertension: High Blood Pressure Can Be Dangerous
Sustained elevation in blood pressure
Systolic pressure  140 mmHg
Diastolic pressure  90 mmHg
Risk factor for cardiovascular disease
Higher blood pressure causes greater strain on cardiovascular system
Blood vessels react by becoming hardened and scarred
Strain on heart from having to work harder
Silent killer, no symptoms

36. Table 8.1
Table 8.1 Systolic and diastolic blood pressure. 36

37. Table 8.2
Table 8.2 Risk factors for hypertension. 37

38. Hypotension: When Blood Pressure Is Too Low
Low blood pressure
If low enough, may cause dizziness or fainting
May follow abrupt changes in body position
Standing up suddenly
May result from excessive blood loss or fluid loss from burns

39. How the Cardiovascular System Is Regulated
Importance of maintaining a constant arterial blood pressure
Constant arterial pressure is achieved by
Regulation of heart rate
Force of contraction
Regulation of diameter of arterioles
Local blood flows are adjusted to meet local requirements

40. Baroreceptors Maintain Arterial Blood Pressure
Baroreceptors: pressure receptors in aorta and carotid arteries
Steps in mechanism
Blood pressure rises, vessels stretched
Signals sent to the cardiovascular center in the brain
Heart signaled to lower heart rate and force of contraction
Arterioles vasodilate, increasing blood flow to tissues
Combined effect lowers blood pressure
Mechanism reversed if blood pressure is too low

41. Nerves and Hormones Adjust Cardiac Output
Amount of blood pumped into aorta in one minute
Cardiac output  heart rate  stroke volume
Heart rate: beats/minute (bpm)
Resting adult heart rate  approx. 75 bpm
Stroke volume:
Resting adult stroke volume  70 ml/beat
Resting cardiac output
75 bpm  70 ml/beat  5.25 liters/min.

42. Nerves and Hormones Adjust Cardiac Output
Medulla oblongata: cardiovascular center of brain
Receives inputs from baroreceptors and other receptors
Output goes through two sets of nerves
1. Sympathetic nerves—constrict blood vessels, raising blood pressure
2. Parasympathetic nerves—dilate blood vessels, lowering blood pressure
Hormones: epinephrine and norepinephrin
Secreted by adrenal glands when sympathetic system is activated
Increase cardiac output

43. Local Requirements Dictate Local Blood Flows
Precapillary sphincters allow fine-tuning of blood flow to local tissues as needed
Metabolically active tissue—needs more O2, sphincters open, vasodilation
If blood pressure drops precipitously, blood pressure control would cause vasoconstriction to many organs and shunt blood to brain and heart where blood supply and pressure must be maintained

44. At rest, very little of the vasodilating
Figure 8.17
Blood flow
Cell
Diffusion of
vasodilating
substance
Arteriole
Precapillary
sphincter
Capillary
Vasodilating
substance
produced
during
metabolism
Figure 8.17 How an increase in metabolism increases local blood flow.
At rest, very little of the vasodilating
substance would be produced, and
flow would be minimal.
With increased metabolic activity,
the presence of more of the
substance in the interstitial space
would cause the arteriole and
precapillary sphincter to vasodilate,
increasing flow. 44

45. Exercise: Increased Blood Flow and Cardiac Output
Blood flow to active skeletal muscles increases
Cardiac output (CO) is increased to maintain blood pressure
Non-athletes: up to 20–25 liters/min
Trained athletes: up to 35 liters/min

46. Cardiovascular Disorders: A Major Health Issue
Angina
Sensation of pain and tightness in chest
Caused by narrowing of coronary arteries and diminished blood flow to coronary muscle
May be accompanied by shortness of breath and sensation of choking or suffocating
Usually temporary
Angiography: allows visualization of coronary arteries, enables diagnosis of angina
Treatment:
Medication
Balloon angioplasty
Coronary artery bypass graft

47. Figure 8.18
Figure 8.18 A coronary angiogram. 47

48. Cardiac Disorders: A Major Health Issue
Heart attack (myocardial infarction)
Sudden death of an area of myocardium
Symptoms:
Intense chest pain, tightness or pressure on chest, radiating left arm pain, jaw and back pain, nausea
Requires immediate medical attention
Diagnosis: ECG and presence of certain enzymes in the blood
Treatment and/or prevention
Control of arrhythmias
Clot-dissolving medications
Coronary artery bypass graft (CABG)—vein from leg is grafted to bypass obstructed coronary artery

49. Aorta Vein grafts Plaque blocking blood flow Figure 8.19
Figure 8.19 Coronary artery bypass grafts. 49

50. Cardiac Disorders: A Major Health Issue
Heart failure
Heart muscle becomes weaker, less efficient
Congestive heart failure: weakness of heart causes fluid back-up in interstitial spaces
Out of breath, swollen ankles, legs, neck veins
Why does the heart weaken?
Age, prior heart attacks, leaky heart valves, lung disease
Treatment
Improve cardiac performance, efficiency
Prevent accumulation of interstitial fluid

51. Cardiac Disorders: A Major Health Issue
Embolism
Sudden blockage of a blood vessel by material floating in the bloodstream
Often a blood clot broken away from a larger clot elsewhere
May be cholesterol deposits, tissue fragments, cancer cells, clumps of bacterial, bubbles of air
Locations
Pulmonary embolism—chest pain, shortness of breath
Cerebral embolism—may cause a stroke
Cardiac embolism—may cause heart attack

52. Cardiovascular Disorders: A Major Health Issue
Stroke
Damage to part of brain caused by an interruption in blood supply
Two common causes
Embolism blocking a brain blood vessel
Rupture of a cerebral artery
Symptoms: depend on area of brain affected
Immediate medical care is crucial
If embolism, patient receives clot-dissolving drugs
If rupture, surgical repair sometimes possible
Recovery may require extensive rehabilitation

53. Replacing a Failing Heart
Heart transplants
Expensive
Average post-transplant survival: 15 years
Problem: shortage of healthy hearts
Temporary solution to shortage of transplant organs:
Artificial heart
Xenotransplant (heart from another animal species)

54. The SynCardia heart. The AbioCor heart. Figure 8.20
Figure 8.20 Artificial hearts.
The SynCardia heart.
The AbioCor heart. 54

55. Reducing Your Risk of Cardiovascular Disease
Don’t smoke
Smokers have twice the risk of heart disease
Watch cholesterol levels
Risk increases with increasing blood cholesterol
Engage in regular moderate exercise
Maintain a healthy weight
Keep diabetes under control
Avoid chronic stress