1. Chapter 23
Circulation

2. How Does Gravity Affect Blood Circulation?
Most animals have a circulatory system that transports O2 and nutrients to cells and takes away CO2 and other wastes
The circulatory system of land animals has evolved adaptations to deal with gravity
Strong hearts are able to pump against the force of gravity
Muscles contract around veins and force blood to the heart through one-way valves
In snakes, wriggling contracts muscles, squeezing veins and increasing circulation

5. Video: Giraffe Courtship Ritual

6. 23.1 The circulatory system connects with all body tissues
A circulatory system transports materials close enough to cells for diffusion to occur
Microscopic capillaries form an intricate network among cells of a tissue
Molecules from blood cells diffuse into interstitial fluid and then into body cells
Waste products diffuse from body cells through interstitial fluid to capillaries for transport to disposal organs

7. Red blood cell Nuclei of smooth muscle cells Capillary LE 23-01b
LM 700

8. Capillary Interstitial Diffusion of fluid molecules Tissue cell
LE 23-01b
Capillary
Interstitial
fluid
Diffusion of
molecules
Tissue
cell

9. MECHANISMS OF INTERNAL TRANSPORT
23.2 Several types of internal transport have evolved in animals
Gastrovascular cavity
Sufficient for animals in which diffusion can transport molecules directly to the cells
Examples: cnidarians, flatworms
Open circulatory system
Heart pumps blood through open-ended vessels to bathe tissue cells directly; no separate interstitial fluid
Body movements help circulate blood
Examples: most molluscs, all arthropods

10. LE 23-02a
Mouth
Circular
canal

11. LE 23-02b
Tubular heart
Pores

12. Closed circulatory systems
Blood is confined to vessels, which keeps it separate from the interstitial fluid
Arteries carry blood away from heart to tissues and organs
Veins return blood to the heart
Capillaries convey blood between arteries and veins within each tissue
Most arteries carry oxygen-rich blood and most veins carry oxygen-depleted blood, but there are important exceptions

13. Capillary beds Arteriole Artery (O2-rich blood) Venule Vein Atrium
LE 23-02c
Capillary beds
Arteriole
Artery
(O2-rich blood)
Venule
Vein
Atrium
Heart
Ventricle
Gill
capillaries
Artery
(O2-poor blood

14. 23.3 Vertebrate cardiovascular systems reflect evolution
The switch from gill breathing to lung breathing in terrestrial vertebrates was accompanied by important changes in the cardiovascular system
Single circuit in aquatic animals
The two-chambered heart pumps blood from gill capillaries to systemic capillaries and back to the heart

15. Double circulation in terrestrial vertebrates
Pulmonary circuit carries blood between heart and lungs
Systemic circuit carries blood between heart and rest of the body
Amphibians: three-chambered heart
Reptiles (except birds): three-chambered heart with partially divided ventricle in most
Birds and mammals: four-chambered heart with ventricle completely divided
Essential adaptation to support high metabolic rate

16. LE 23-03a Gill capillaries Heart: Ventricle (V) Atrium (A)
Systemic capillaries

17. LE 23-03b Lung and skin capillaries Pulmocutaneous circuit A A V Right
Left
Systemic
circuit
Systemic capillaries

18. LE 23-03c Lung capillaries Pulmonary circuit A A V V Right Left
Systemic
circuit
Systemic capillaries

19. THE MAMMALIAN CARDIOVASCULAR SYSTEM
23.4 The human heart and cardiovascular system are typical of mammals
The mammalian heart
Formed mostly of cardiac muscle tissue
Two thin-walled atria receive blood and pump it into the ventricles
Thick-walled ventricles pump blood to lungs and other body organs
Valves maintain the flow in one direction
Animation: Path of Blood Flow in Mammals

20. LE 23-04a
Right
atrium
Left
atrium
Semilunar
valve
Semilunar
valve
Atrioventricular
(AV) valve
Atrioventricular
(AV) valve
Right
ventricle
Left
ventricle

21. The flow of blood is from the heart to the lungs, back to the heart, out to the body, and then back to the heart
Pulmonary circuit
1. Right ventricle
2. Pulmonary arteries
3. Capillaries in lungs
4. Pulmonary veins
5. Left atrium
6. Left ventricle

22. Systemic circuit
7. Aorta
8. Head, chest, arms, abdominal region, legs
9. Superior and inferior venae cavae
10. Right atrium to right ventricle

23. LE 23-04b Capillaries of Superior head, chest, and vena cava arms
Pulmonary
artery
Pulmonary
artery
Capillaries
of right lung
Aorta
Capillaries
of left lung
Pulmonary
vein
Pulmonary
vein
Right atrium
Left atrium
Left ventricle
Right ventricle
Inferior
vena cava
Aorta
Capillaries of
abdominal region
and legs

24. 23.5 The structure of blood vessels fits their functions
Capillaries
Thin walls with a single layer of epithelial cells
Facilitate exchange of materials
Arteries and veins
Epithelium reinforced by layers of smooth muscle and connective tissue

25. Arteries
Thicker walls accommodate the rapid flow of blood and high pressure
Smooth muscle can regulate blood flow by constriction or relaxation
Veins
Thinner walls, under less pressure and slower flow
Valves prevent backflow

26. Capillary Epithelium Basement membrane Valve Epithelium Epithelium
LE 23-05
Capillary
Epithelium
Basement
membrane
Valve
Epithelium
Epithelium
Smooth
muscle
Smooth
muscle
Connective
tissue
Connective
tissue
Artery
Vein
Arteriole
Venule

27. 23.6 The heart contracts and relaxes rhythmically
The cardiac cycle is a complete sequence of filling and pumping
Diastole
1. Heart is relaxed; blood flows from the veins into all four chambers
Systole
2. Atria contract briefly; ventricles completely fill with blood
3. Ventricles contract; valves open and close; blood pumps into the large arteries and then flows into atria

28. LE 23-06 Atria Heart is contract. relaxed. AV valves are open. 0.1 sec
Systole
0.3 sec
Ventricles
contract.
Semilunar
valves
are open.
0.4 sec
Diastole

29. Cardiac output is the amount of blood/minute pumped into the systemic circuit by the left ventricle
Heart valves prevent the backflow of blood
“Lub-dup” sounds caused by the closing of valves
Heart murmur may indicate a valve defect

30. 23.7 The pacemaker sets the tempo of the heartbeat
The pacemaker (SA node) maintains the heart’s pumping rhythm
1. SA node generates electrical signals
2. Signals make atria contract in unison; are delayed at AV node
3. Specialized muscle fibers relay signals to apex of heart
4. Signals are relayed through walls of ventricles, triggering contractions that drive blood out of the heart

31. LE 23-07 Specialized AV node muscle fibers Pacemaker (SA node) Right
artium
Right
ventricle
Apex
ECG

32. An electrocardiogram measures electrical activity of the heart through changes in the skin
An artificial pacemaker provides a regular electrical signal to trigger normal heartbeat
Heart rate is also influenced by nerves, hormones, and environmental conditions

33. CONNECTION 23.8 What is a heart attack?
A heart attack is the death of cardiac muscle cells and the resulting failure of the heart to deliver enough blood to the rest of the body
Results from blockage in coronary arteries
Cardiovascular disease is a leading cause of death in the United States
Atherosclerosis: development of plaques on artery walls, impeding blood flow
Tendency may be inherited, but lifestyle changes can reduce risk

34. Aorta Superior vena cava Left coronary artery Pulmonary artery Right
LE 23-08a
Aorta
Superior
vena cava
Left
coronary
artery
Pulmonary
artery
Right
coronary
artery
Blockage
Dead
muscle
tissue

35. LE 23-08b Connective tissue Smooth muscle Epithelium Plaque LM 160

36. 23.9 Blood exerts pressure on vessel walls
Blood pressure is the force blood exerts against the walls of blood vessels
Caused by pumping of the heart
Can be felt as pulse, the rhythmic stretching of the arteries

37. Blood pressure and velocity depend partly on cardiac output and partly on the resistance of vessels
Highest in the aorta and arteries
Decrease abruptly as blood enters arterioles because of friction between blood and large surface area
Lowest in capillaries, because cross-sectional area is greatest
Near zero in veins
Blood returns to the heart with the aid of muscular contractions and valves

38. LE 23-09a 120 Systolic pressure 100 80 Pressure (mm Hg) 60 Diastolic40 20
Relative sizes and
numbers
of blood
vessels 50 40
Velocity (cm/sec) 30 20 10
Aorta
Veins
Arteries
Arterioles
Venules
Capillaries
Venae cavae

39. LE 23-09b Direction of blood flow in vein Valve (open) Skeletal muscle
(closed)

40. CONNECTION
23.10 Measuring blood pressure can reveal cardiovascular problems
Blood pressure indicates the force of the heart’s beating during systole and the background pressure of the blood in arteries during diastole
Blood pressure is measured as systolic over diastolic pressure, in mm Hg
110/70 is typical for a healthy young adult
Higher than normal blood pressure may indicate serious cardiovascular disorder
Hypertension is persistent blood pressure higher than 140/90

41. LE 23-10-3 Blood pressure 110 systolic 70 diastolic (to be measured)
in cuff
above 110
Pressure
in cuff
at 110
Pressure
in cuff
at 70
Rubber cuff
inflated
with air
110
110 70
Sounds
audible in
stethoscope
Sounds
stop
Artery
Artery
closed

42. 23.11 Smooth muscle controls the distribution of blood
Except for the brain, liver, kidneys, and heart, blood supply varies depending on tissue need
Constriction of arterioles can reduce blood flow to capillaries
Contraction and relaxation of precapillary sphincters controls blood flow through capillary beds
Nerves and hormones influence the contraction of smooth muscles in both mechanisms

43. Precapillary sphincters Thoroughfare channel
LE 23-11a
Precapillary sphincters
Thoroughfare
channel
Capillaries
Arteriole
Venule
Sphincters relaxed

44. Sphincters contracted
LE 23-11b
Thoroughfare
channel
Arteriole
Venule
Sphincters contracted

45. 23.12 Capillaries allow the transfer of substances through their walls
Capillaries are the only vessels with walls thin enough to allow transfer of substances through the epithelium
The transfer of materials between the blood and interstitial fluid occurs in several ways
Diffusion
Endocytosis and exocytosis
Pressure-driven flow through clefts between epithelial cells

46. Forces driving fluid out of and into capillaries
Blood pressure forces fluid out of the capillary at the arterial end
Osmotic pressure draws fluid in at the venous end

47. Nucleus of epithelial cell
LE 23-12a
Capillary
lumen
Capillary
wall
Interstitial
fluid
Nucleus of
epithelial
cell
Muscle
cell
Cleft between
two epithelial
cells of the
capillary wall
TEM 5,000

48. LE 23-12b Tissue cells Osmotic pressure Osmotic pressure Arterial
end of
capillary
Venous
end of
capillary
Blood
pressure
Blood
pressure
Interstitial
fluid
Net fluid
movement out
Net fluid
movement in

49. STRUCTURE AND FUNCTION OF BLOOD
23.13 Blood consists of red and white blood cells suspended in plasma
Blood is about 55% plasma and 45% cellular elements
Plasma
90% water
10% dissolved inorganic ions, proteins, nutrients, wastes, gases, and hormones
Red blood cells (erythrocytes)
Transport O2 bound to hemoglobin

50. White blood cells (leukocytes)
Function both inside and outside the circulatory system to fight infections and cancer
Platelets
Cell fragments involved in clotting

51. LE 23-13a Plasma (55%) Constituent Major functions Water Solvent for
carrying other
substances
Salts (ions)
Osmotic balance,
pH buffering, and
nerve and muscle
function
Sodium
Centrifuged
blood
sample
Potassium
Calcium
Magnesium
Chloride
Bicarbonate
Plasma proteins
Osmotic balance
and pH buffering
Fibrinogen
Clotting
Immunoglobulins
(anitbodies)
Immunity
Substances transported by blood
Nutrients (e.g., glucose, fatty acids, vitamins)
Waste products of metabolism
Respiratory gases (O2 and CO2)
Hormones

52. LE 23-13b Cellular elements (45%) Cell type Number
per L (mm3) of blood
Functions
Erythrocytes
(red blood cells)
5–6 million
Transport of
oxygen (and
carbon dioxide)
Centrifuged
blood
sample
Leukocytes
(white blood cells)
Defense and
immunity
5,000–10,000
Lymphocyte
Basophil
Eosinophil
Neutrophil
Monocyte
Platelets
250,000–
400,000
Blood clotting

53. 23.14 Too few or too many red blood cells can be unhealthy
CONNECTION
23.14 Too few or too many red blood cells can be unhealthy
Red blood cells
Circulate for 3 to 4 months
Old cells are broken down and their components are recycled
Anemia
An abnormally low amount of hemoglobin or red blood cells
Most commonly caused by iron deficiency

55. Red blood cell production
Takes place in bone marrow
Under control of a negative feedback system
Mediated by the hormone erythropoietin
Increased red blood cell production is a physiological adaptation to living at high altitudes
Athletes may try dangerous artificial methods

56. 23.15 Blood clots plug leaks when blood vessels are injured
Blood clotting involves platelets, the plasma protein fibrinogen, and clotting factors
The clotting process
1. Platelets adhere to exposed connective tissue
2. Platelet plug forms
3. Fibrinogen converted to fibrin, forms clot that traps blood cells

57. LE 23-15a Platelets adhere to exposed connective tissue
Platelet plug forms
Fibrin clot traps
blood cells
Epithelium
Connective tissue
Platelet plug
Platelet

58. Blood-clotting malfunctions
Hemophelia
Inherited disease
Blood doesn’t clot, and bleeding can be fatal
Thrombus
Clot formed in the absence of injury
Can break free and lodge in a vessel, causing heart attack, stroke, or pulmonary embolism

59. 23.16 Stem cells offer a potential cure for blood cell diseases
CONNECTION
23.16 Stem cells offer a potential cure for blood cell diseases
Red bone marrow contains unspecialized stem cells
Differentiate to produce all blood cells
Continually produce all the blood cells needed throughout life
Stem cells may be used to treat some blood disorders such as leukemia, cancer of the white blood cells
Healthy bone marrow may be transplanted from a donor

60. Stem cells Stem cells Basophils Erythrocytes Platelets Eosinophils
Lymphocytes
Monocytes
Neutrophils