1. CARDIOVASCULAR SYSTEM
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2. Objective Students should be able to:
Compare the histological structures of arteries and veins.
Relate the structure of different blood vessel walls to their function.
Examine the nutrient blood supply and the innervation of large blood vessels.
Compare the organisation and structure of exchange vessels in different tissues.

3. The Heart Into the right atrium comes blood from :
From the right ventricle blood is pumped to the :
Into the left atrium blood comes from :
From the left ventricle blood is pumped to :

4. The Heart Into the right atrium comes blood from :
The systemic circulation.
From the right ventricle blood is pumped to the :
Into the left atrium blood comes from :
From the left ventricle blood is pumped to :

5. The Heart Into the right atrium comes blood from :
The systemic circulation.
From the right ventricle blood is pumped to the :
Lungs.
Into the left atrium blood comes from :
From the left ventricle blood is pumped to :

6. The Heart Into the right atrium comes blood from :
The systemic circulation.
From the right ventricle blood is pumped to the :
Lungs.
Into the left atrium blood comes from :
From the left ventricle blood is pumped to :

7. The Heart Into the right atrium comes blood from :
The systemic circulation.
From the right ventricle blood is pumped to the :
Lungs.
Into the left atrium blood comes from :
From the left ventricle blood is pumped to :

8. Canine Thorax left view, left lung removedSy C As A V2 S O V1 LA D L P LV RV
A – Aorta D – Diaphragm
LV- Left ventricle LA- Left auricle
RV- Right ventricle O - Oesophagus
S - Left subclavian artery
L - Accessory lobe of right lung
P - Left phrenic nerve innervating diaphragm
Sy - Sympathetic trunk
V1 - Dorsal vagal trunk V2 - Ventral vagal trunk
C - Cervicothoracic ganglion (sympathetic)
As - Ansa subclavia of cervicothoracic ganglion
White arrow - Left interventricular groove
(Sulcus interventricularis paraconalis)

9. Demo slide section through wall of heart.
What three layers make up the wall of the heart?
1.0 mm

10. Demo slide section through wall of heart.
What three layers make up the wall of the heart?
Endocardium : lines atria and ventricles, forms valves.
Myocardium : the cardiac muscle.
Epicardium : covers the external surface of the heart – serous membrane also called the visceral pericardium.
myocardium
endocardium
chamber of ventricle
epicardium
1.0 mm

11. Demo slide section through developing rabbit heart
LA: left atrium
LV: left ventricle
RV: right ventricle
pulmonary artery
ductus arteriosus
bronchus
oesophagus
aortic arch
(path of)
lung LA
pulmonary
arch
atrio-ventricular
valve
vena cava
diaphragm LV RV
liver
ribs
1.0 mm

12. Identify the principal features of cardiac muscle.
SLIDE 106 Cardiac muscle
Identify the principal features of cardiac muscle.
50 µm

13. SLIDE 106 Cardiac muscle
Identify the principal features of cardiac muscle.
Intercalated discs, central nuclei (usually one but sometimes two) with perinuclear space, branched fibres, good blood supply. I
I : intercalated discs
central nucleus
branched fibres
blood vessels
50 µm

14. SLIDE 106 Cardiac muscle
List the structures that allow cardiac muscle to act as a functional syncytium.
TS section of fibres
25 µm

15. SLIDE 106 Cardiac muscle
List the structures that allow cardiac muscle to act as a functional syncytium.
Intercalated discs. Gap junctions.
Branched fibres – lateral junctions.
Rich vasculature.
TS section of fibres
25 µm

16. Cardiac muscle demonstration slide for Purkinje fibres
What type of cells make up Purkinje fibres?
M : myocardium
Pf : Purkinje fibres
L : lumen of heart M Pf L
250 µm
The endocardium is lost in this section

17. Cardiac muscle demonstration slide for Purkinje fibres
What type of cells make up Purkinje fibres?
Impulse conducting cardiac muscle cells.
They form the atrioventricular bundle and its branches in the walls of the ventricles.
M : myocardium
Pf : Purkinje fibres
L : lumen of heart M Pf L
250 µm
The endocardium is lost in this section

18. SLIDE 56 Aorta (dog) elastic arteries
This slide shows a transverse section through the aorta.
Identify the layers of this structure at both low and high magnification.
Suggest why there appear to be two lumens in this structure?
1.0 mm

19. SLIDE 56 Aorta (dog) elastic arteries
This slide shows a transverse section through the aorta.
Identify the layers of this structure at both low and high magnification.
Suggest why there appear to be two lumens in this structure?
The section was most likely cut at the divergence of the brachiocephalic trunk.
aorta
brachiocephalic trunk
1.0 mm

20. SLIDE 56 Aorta (dog) elastic arteries
Identify the layers of this structure.
250 µm

21. SLIDE 56 Aorta (dog) elastic arteries
Identify the layers of this structure.
Tunica intima (interna) : consists of endothelial lining, sub endothelial connective
tissue and internal elastic membrane.
Tunica media : consists of circular smooth muscle layer, elastic and collagen fibres
and the external elastic membrane.
Tunica externa (adventitia) : outer covering. connective tissue sheath.
tunica media
lumen
tunica externa
tunica intima
250 µm

22. SLIDE 56 Aorta (dog) elastic arteries
What structures are present in the tunica adventitia?
What is their function?
250 µm

23. SLIDE 56 Aorta (dog) elastic arteries
What structures are present in the tunica adventitia?
Blood vessels – the vaso vasorum and autonomic nerves – the nervi vasorum.
What is their function?
They supply the wall of the blood vessel.
adipocytes
blood vessel
nerve
250 µm

24. Micrograph of cross section of a nerve fascicle
This section was stained with haematoxylin and eosin and shows the typical appearance of a nerve bundle running through the tissue.
Remember the diameters of such bundles can vary considerably.
50 µm

25. SLIDE 56 Aorta (dog) elastic arteries
Why are elastic fibres more prevalent in the aorta than in other arteries?
50 µm

26. SLIDE 56 Aorta (dog) elastic arteries
Why are elastic fibres more prevalent in the aorta than in other arteries?
The elasticity of the tunica media sustains blood pressure (reduces fluctuations) between heart beats.
smooth muscle
tunica
media
collagen
elastic fibres
tunica intima
endothelium
50 µm

27. SLIDE 56 Aorta (dog) elastic arteries
Why are elastic fibres more prevalent in the aorta than in other arteries?
The elasticity of the tunica media sustains blood pressure (reduces fluctuations) between heart beats.
Systole : elastic walls stretched. Pressure converted to elastic tension.
Diastole : elastic rebound in arterial wall maintains blood pressure.
smooth muscle
tunica
media
collagen
elastic fibres
tunica intima
endothelium
50 µm

28. Compare with previous slide 56 (aorta).
SLIDE 51 Large veins
Compare with previous slide 56 (aorta).
250 µm
1.0 mm

29. Are the same layers present in both vessels?
SLIDE 51 Large veins
Are the same layers present in both vessels?
100 µm

30. Are the same layers present in both vessels? Yes.
SLIDE 51 Large veins
Are the same layers present in both vessels?
Yes.
lumen
tunica intima
tunica media
tunica adventitia
100 µm

31. In which layer are most of the smooth muscle cells found?
SLIDE 51 Large veins
In which layer are most of the smooth muscle cells found?
50 µm

32. SLIDE 51 Large veins
In which layer are most of the smooth muscle cells found?
In the tunica media; (walls of veins are thinner relative to the size of the lumen).
lumen
endothelium
muscle cells in
tunica media
tunica adventitia
50 µm

33. SLIDE 51 Large veins
Junction between tunica media and tunica adventitia.
Dark pink staining muscle cells more numerous in tunica media.
A small venule is seen in the tunica adventitia.
venule
50 µm

34. At high magnification the depth of the tunica intima can be seen.
SLIDE 51 Large veins
At high magnification the depth of the tunica intima can be seen.
25 µm

35. At high magnification the depth of the tunica intima can be seen.
SLIDE 51 Large veins
At high magnification the depth of the tunica intima can be seen.
endothelial cells
smooth muscle cell
in tunica media
tunica intima
25 µm

36. SLIDE 52 Large vein (Vena cava) elastic stain
In this section elastic tissue has been stained black.
Which region has the most elastic tissue?
250 µm

37. SLIDE 52 Large vein (Vena cava) elastic stain
In this section elastic tissue has been stained black.
Which region has the most elastic tissue?
Tunica media.
tunica intima
tunica media
tunica adventitia
250 µm

38. SLIDE 52 Large vein (Vena cava) elastic stain
At higher magnification, elastic fibres can be seen.
elastic fibres
100 µm

39. SLIDE 57 Muscular arteries
Muscular arteries are usually smaller diameter than elastic ones.
Autonomic regulation of these vessels produces changes in blood flow to organ systems.
1.0 mm

40. SLIDE 57 Muscular arteries
How does the structure of a muscular artery relate to its compliance?
100 µm

41. SLIDE 57 Muscular arteries
How does the structure of a muscular artery relate to its compliance?
Thicker musculature - lower compliance.
tunica adventitia
tunica media
tunica intima
blood cells
smooth muscle
cells
100 µm

42. SLIDE 57 Muscular arteries
The smooth muscle cells in the tunica media
50 µm

43. SLIDE 57 Muscular arteries
What is the functional significance of the arrangement of these smooth muscle cells?
The smooth muscle is a near-circular tight helical arrangement.
Muscular arteries control blood flow to various organs.
50 µm

44. Femoral vein
The three layers tunica intima, tunica media and tunica adventitia can be identified.
The thickest layer is the tunica adventitia.
tunica intima
lumen
tunica media
tunica adventitia
250 µm

45. Identify the layer of endothelial cells lining the vein.
Femoral vein
Identify the layer of endothelial cells lining the vein.
50 µm

46. Identify the layer of endothelial cells lining the vein.
Femoral vein
Identify the layer of endothelial cells lining the vein.
tunica adventitia
tunica media
endothelium
tunica intima
50 µm

47. SLIDE 59 Muscular artery (elastic stain)
Muscular artery stained to show elastic fibres.
0.5 mm

48. SLIDE 59 Muscular artery (elastic stain)
The internal elastic membrane of the tunica intima can be seen. Also the external elastic membrane at the base of the tunica media.
The tunica adventitia has the most elastic fibres (stained black) and is of a similar thickness to the tunica media.
100 µm

49. SLIDE 59 Muscular artery (elastic stain)
The internal elastic membrane of the tunica intima can be seen. Also the external elastic membrane at the base of the tunica media.
The tunica adventitia has the most elastic fibres (stained black) and is of a similar thickness to the tunica media.
external elastic
membrane
internal elastic
membrane of
tunica intima
tunica adventitia
tunica media
endothelium
elastic fibres
100 µm

50. SLIDE 59 Companion vein (elastic stain)
Again with the companion vein most of the elastic fibres are staining up in the tunica adventitia, which is the thickest layer.
100 µm

51. SLIDE 59 Companion vein (elastic stain)
Again with the companion vein most of the elastic fibres are staining up in the tunica adventitia, which is the thickest layer.
endothelium of tunica intima
tunica media
elastic fibres in
tunica adventitia
100 µm

52. SLIDE 34 Arterioles and venules (stomach submucosa)
In this section of the stomach; identify the submucosa and locate arterioles and venules.
250 µm

53. SLIDE 34 Arterioles and venules (stomach submucosa)
In this section of the stomach; identify the submucosa and locate arterioles and venules.
mucosal layers
submucosa
muscularis
250 µm

54. SLIDE 34 Arterioles and venules (stomach submucosa)
Why is the lumen of the arteriole smaller than that of the venule?
100 µm

55. SLIDE 34 Arterioles and venules (stomach submucosa)
Why is the lumen of the arteriole smaller than that of the venule?
Compliance.
A : arteriole V
V : venule A A V
100 µm

56. SLIDE 34 Arterioles and venules (stomach submucosa)
The walls of the arterioles have distinct layers of smooth muscle and regulate the blood flow through the capillary bed.
The thin walls of venules may have a few smooth muscle cells.
50 µm

57. Arterioles and venules
Identify which of these structures contributes
a) most to peripheral resistance:
b) least to peripheral resistance:
Elastic artery arteriole capillary vein venule

58. Arterioles and venules
Identify which of these structures contributes
a) most to peripheral resistance:
b) least to peripheral resistance:
Elastic artery arteriole capillary vein venule a

59. Arterioles and venules
Identify which of these structures contributes
a) most to peripheral resistance:
b) least to peripheral resistance:
Elastic artery arteriole capillary vein venule
a b

60. Capillaries and sinusoids
Identify capillaries or sinusoids in the following slides:
Capillaries in loose connective tissue - slide 118.
Capillaries in skeletal muscle slide 6 (goat tongue).
- slide 103.
Capillaries in cardiac muscle slide 106.
Capillaries in loose connective tissue slide 58.
Locate sinusoids in the liver slide 49.
- slide 21.

61. SLIDE 118 Capillary in loose connective tissue Viewed under an oil immersion lens the flattened nature and single layer of simple squamous epithelium (endothelium) of the capillary wall can be seen. REVISION Simple Squamous Epithelium… a single layer of thin and flattened cells well adapted for active transport and movement of gases and metabolites.
N : nuclei of endothelial cells N N
25 µm

62. SLIDE 6 Skeletal muscle (goat)
Capillaries in the skeletal muscle of the tongue.
Low magnification view showing surface papillae, striated muscle layers and glandular units.
muscle
salivary
glands
1.0 mm

63. SLIDE 6 Skeletal muscle (goat)
The striated muscle fibres of the tongue run in many directions.
Sections of tongue muscle provide good examples of capillaries cut in longitudinal and in transverse section.
100 µm

64. SLIDE 6 Skeletal muscle (goat)
At high magnification the individual blood cells can be resolved in the capillaries.
25 µm

65. SLIDE 6 Skeletal muscle (goat)
At high magnification the individual blood cells can be resolved in the capillaries.
C : capillaries M
E : endothelial cells C
M : muscle nuclei C E M E
25 µm

66. SLIDE 103 Striated skeletal muscle (rat)
Shown : A-bands.
I- bands.
Z-lines
sarcomere
capillary in
the endomysium
10 µm

67. Capillaries in cardiac muscle.
SLIDE 106 Cardiac muscle
Capillaries in cardiac muscle.
red blood cells
in capillary
25 µm

68. Capillaries in cardiac muscle.
SLIDE 106 Cardiac muscle
Capillaries in cardiac muscle.
red blood cells
in capillary
50 µm

69. SLIDE 58 Loose connective tissue (spread)
Capillaries in loose (areolar) connective tissue.
This slide is a spread preparation.
C : capillaries
P : pericytes A C
A : adipocytes C P A P
50 µm

70. SLIDE 58 Loose connective tissue (spread)
Areolar connective tissue.
How can you distinguish the blood capillaries?
The capillaries are cellular, the endothelial cells forming the walls are visible as are often the circulating red and white blood cells. C C
C : capillaries F
adipocytes
F : fibroblasts C
25 µm

71. SLIDE 49 Adult liver (pig)
Sinusoids in liver lobules.
Hepatocytes form cords of cells with at least one surface against a sinusoid.
250 µm

72. SLIDE 49 Adult liver (pig)
Sinusoids in liver lobules.
Hepatocytes form cords of cells with at least one surface against a sinusoid.
hepatocyte cords
central vein
sinusoids
portal area
250 µm

73. SLIDE 49 Adult liver (pig)
Sinusoids in liver lobules.
100 µm

74. SLIDE 49 Adult liver (pig)
Sinusoids in liver lobules.
C : central vein
hepatocytes
sinusoids C
100 µm

75. SLIDE 21 Sinusoids in liver (Stained for reticular fibres)
Revision : Note the loose interwoven network created by the reticular fibres that are stained black.
What is this protein fibre composed of?
Collagen type III.
Why is this protein fibre most appropriate in these tissues?
Reticular fibres support tissues and organs, protecting cells and structures subjected to volume changes.
hepatocytes
reticular fibres
sinusoids
25 µm

76. Capillaries and sinusoids
State three differences between sinusoids and capillaries.

77. Capillaries and sinusoids
State three differences between sinusoids and capillaries.
Sinusoids usually larger and more varied shape than capillaries.
Sinusoids may be fenestrated, have gaps and pores in the endothelium.
They have a discontinuous basal lamina.
What structures connect individual endothelial cells?

78. Capillaries and sinusoids
State three differences between sinusoids and capillaries.
Sinusoids usually larger and more varied shape than capillaries.
Sinusoids may be fenestrated, have gaps and pores in the endothelium.
They have a discontinuous basal lamina.
What structures connect individual endothelial cells?
Gap or tight junctions.

79. Capillaries and sinusoids
What is an arteriovenous anastamosis?
How do capillaries resist collapse?
In which vessels are valves found, and why?

80. Capillaries and sinusoids
What is an arteriovenous anastamosis?
A by-pass of the capillary bed between an arteriole and a venule.
How do capillaries resist collapse?
In which vessels are valves found, and why?

81. Capillaries and sinusoids
What is an arteriovenous anastamosis?
A by-pass of the capillary bed between an arteriole and a venule.
How do capillaries resist collapse?
Arteriole blood pressure maintains capillary shape.
In which vessels are valves found, and why?

82. Capillaries and sinusoids
What is an arteriovenous anastamosis?
A by-pass of the capillary bed between an arteriole and a venule.
How do capillaries resist collapse?
Arteriole blood pressure maintains capillary shape.
In which vessels are valves found, and why?
In some veins. Particularly those draining the limbs.
They prevent backflow and back pressure.

83. Lectures Dr. C.Lawson.
First Year Histology Cardiovascular J.Bredl
Gross Anatomy Correlates S.Frean
Histology Slides and Stains Tanya Hopcroft.
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