1. Cardiac muscle

2. Elastic artery

3. Muscular artery

4. Large vein

5. The Cardiovascular system: Histology of heart & blood vessels

6. Learning objectives
Describe the histology (microscopic anatomy) of heart (cardiac muscle).
Describe the histology (microscopic anatomy) of arteries (large, medium sized & small).
Explain the histology (microscopic anatomy) of veins (small, medium, sized & large).

7. Cardiovascular system
Heart
Arteries
Veins
Capillaries

8. Cardiac muscle Form of striated muscle, found only in the heart.
Structurally similar to skeletal, but some differences.
Cells are smaller having specialized communication structures.
Contraction is an inherent property, no direct neural stimulation needed.
No neuro muscular junction.

9. Heart- right atrium and ventricle
Epicardium (Visceral layer of serous pericardium)
Myocardium (cardiac muscle)
Endocardium (Endothelial cells)

10. Cardiac muscle Desmosomes Gap junctions
Cardiac muscle fibre is 15 m wide X 100 m long, shows cross striations.
Uninucleated and oval nucleus in the centre of the cell.
Branched.
Presence of Intercalated discs.
Desmosomes
Gap junctions

11. Cardiac muscle • Unique structure, the intercalated disc.
• Striations are present.
• Unique structure, the intercalated disc.

12. Intercalated disc structure for communication & adhesion.
Special
structure for
communication & adhesion.
Includes adhering junctions & gap
Junctions.

13. Cardiac muscle -Regeneration & repair
Cardiac muscle cells can’t divide.
Injury causes some loss of material, part or all of a myofiber.
Scarring “fills in” the space with non-contractile collagen.
A scanty reserve of myoblasts exists in skeletal muscle not in smooth or cardiac.
Limited regeneration in skeletal muscle – but not in cardiac muscle.

14. OSPE Uninucleated,oval nucleus in the centre.
Presence of branches and intercalated disc.

15. Histology of blood vessels

16. General structure of the blood vessels
Blood vessels are composed of 3 layers or tunics.
1.Tunica Intima:
- Consists of a layer of endothelial cells lining interior surface which rest on a basal lamina. Endothelial cells are specialized mesenchymal cells and not an epithelial tissue. Endothelium normally provides a non-thrombogenic surface because it contains heparan sulfate.
- Beneath the endothelium is the sub endothelial layer, consisting of loose connective tissue and smooth muscle cells, arranged longitudinally.

17. General structure of the blood vessels
2.Tunica Media
- Consists chiefly of concentric layers of helically arranged smooth muscle cells. Interposed among the smooth muscle cells are variable amounts of elastic and reticular fibers, type I collagen, and proteoglycans.
- In arteries, the intima separated from the media by internal elastic lamina , composed of elastin, has gaps that allows substances to diffuse to and nourish cells.
- In arteries, a thinner external elastic lamina is found separating the media from the outer layer.

18. General structure of the blood vessels
3.Tunica adventitia:
Made up of loose connective tissue,consists of longitudinally oriented collagen and elastic fibres.
Contains vasa vasorum (vessels of the vessel)-In large vessels, vasa vasorum branch profusely in the adventitia and the outer part of the media.
- Vaso vasorum supply blood to the tunica media and the tunica adventitia.

19. General structure of the blood vessels

20. Arteries - Types
Elastic Arteries: e.g., aorta, brachiocephalic artery, carotid artery.
Muscular Arteries: (medium-sized,
distributing) e.g., superior mesenteric artery,
radial artery,
Small Arteries: the last of the distributing
arteries.
Arterioles: tunica media consisting of 1 or 2 layers of smooth muscle cells.

21. Histology of Arteries

22. Elastic artery - Aorta
Tunica intima: Thicker than in the muscular arteries. Endothelial cells line the lumen.Sub endothelial layer is thick. Internal elastic lamina is similar to the elastic lamina of the next layer. Hence not seen clearly.
Tunica media: Consists of concentrically arranged perforated elastic laminae. Between the elastic laminae are smooth muscle cells, reticular fibers. External elastic lamina not seen clearly.
Tunica adventitia: relatively undeveloped, contains elastic and collagen fibers. Vasa vasorum are seen.

23. Elastic artery - Aorta
Tunica Intima
Tunica media
Tunica adventitia

24. Elastic artery Elastic laminae
and smooth muscle (arrowheads) of Tunica media.
Vasa vasora (venule and arteriole)
in tunica adventitia.

25. Muscular artery- Medium sized artery
Tunica intima: endothelial cells & subendothelial layer - thicker than in the arterioles, few smooth muscle cells present. Internal elastic lamina prominent.
Tunica media: contain up to 40 layers of smooth muscle cells, intermingled with elastic lamellae. External elastic lamina seen clearly.
Tunica adventitia: consists of collagen and elastic fibers, few fibroblasts, and adipose cells.

26. Muscular artery- Medium sized artery
Elastic fibers in tunica media form the internal elastic lamina.
Tunica intima
Tunica media
Tunica adventitia

27. Muscular artery- Medium sized artery
Tunica intima
Internal elastic lamina
External elastic lamina
Tunica media
Tunica adventitia

28. Muscular artery - Medium sized artery

29. Internal elastic lamina
Small artery
Tunica adventitia
Internal elastic lamina
Tunica media
Endothelium

30. Small artery and vein
Artery
Capillary
Vein

31. Arteriole
Arteriole

32. Arteriole within subcutaneous connective tissue
Capillary

33. Capillary Blood from capillary bed passes into thin walled venules.
Are simple endothelial tubes. Connecting arterial & venous sides. Interchange of oxygen, nutrients waste products with extracellular fluid occurs.
Blood from capillary bed passes into thin walled venules.
Two types – fenestrated & continuous.

34. Histopathology of arteries
Degenerative changes in elastic and muscular arteries are strongly influenced by both genetics & life style.
Changes are present in the aorta and its branches in most individuals after 50 years. However, these can often be found as early as the late teens and early 20’s.
These degenerative changes are collectively designated as arteriosclerosis.
Degenerative changes do not occur in small arteries.

35. Arteriosclerotic changes in a medium-sized artery
External
Elastic membrane
Internal
Elastic membrane:
fragmented
Loss of elastic
fibers apparent
Lumen
T. media
T. intima
T. adventitia

36. Coronary artery arteriosclerosis & thrombosis
T. Adventitia
T. media
T. intima
thickened
Thrombus
Narrowed lumen
of artery

37. Histology of veins Small veins and venules. Medium-sized veins.
Large veins.

38. Companion arteriole & venule

39. Medium-sized vein Example : Basilic, cephalic & saphenous veins.
Tunica intima has a thin sub endothelial layer.
Tunica media consists of small bundles of smooth muscle cells intermixed with reticular and elastic fibers.
Tunica adventitia rich in collagen, well-developed.

40. Medium-sized vein (spermatic cord)
Tunica intima
Tunica media
Tunica adventitia

41. Medium-sized vein of leg
Tunica adventitia
Tunica media
Tunica intima

42. Medium-sized vein

43. Large vein
Tunica intima: Consists of endothelial cells and subendothelial layer made up of connective tissue.
Tunica media: Much thinner, with few layers of smooth muscle cells and abundant connective tissue.
Tunica adventitia: Thickest and best developed, contains longitudinal bundles of smooth muscle, present in the connective tissue.

44. Large vein (inferior vena cava)
Tunica intima
Tunica media
Tunica adventitia

45. Large vein (inferior vena cava)
Tunica media
Tunica adventitia

46. Comparison (A) artery and (B) vein

47. To sum up

48. Cardiac muscle

49. Elastic artery

50. Muscular artery

51. Large vein

52. Any questions ?

53. Thank you