1. Department of Histology & Embryology Sichuan University
Circulatory system
Department of Histology & Embryology
Sichuan University

2. I. The components of the Circulatory system
Cardiovascular System
Lymphatic vascular system

3. Arteries Heart Capillaries Tissues Veins ← ← Thoracic duct
Right lymphatic duct
Lymphatic
vessels
Lymphatic
capillaries ← ←

4. function: transport nutrient,oxygen,carbon dioxide
and waste metabolic product

5. II. General Structure of the Blood Vessels
tunica intima
tunica adventitia
tunica media

6. III. Arteries
Large artery
Medium-sized artery
Small artery
Arteriole

7. Medium-sized artery
Muscular A.

8. Medium-sized artery Muscular A. Structural characters Function
1. Very much (10~40 layers) smooth muscle cells
intermingled with collagenous F., elastic F.
2. Very evident internal and external elastic lamina
3. Very defined 3 layers
Function
regulate blood flow to various organs

9. Large artery elastic A.

10. Structural characters
Large artery elastic A.
Structural characters
1. tunica media consists of elastic membranes mainly
abundant (40~70 layers) elastic laminas
and a few smooth muscle cells in media
2. internal and external elastic membranes
are not prominent
3. three layers are not distinguished

11. Functions of large A. 1.transport blood from heart
2.store blood during ventricle contraction
3.elastic recoil keep continuous blood flow

12. Small artery and arteriole muscular A.
Structural characters
1.Diameter<1mm
2. Present internal elastic lamina
3. A few layers of smooth muscle F.
4. No external elastic lamina
5.Arteriole: diameter < 0.3mm
1~2layers of smooth muscle F.
Functions
1. regulate blood flow to organs and tissues
2. regulate blood pressure

13. Comparison
LA MA SA
Internal elastic lamina not evident evident present
media elastic laminas S.M.F S.M.F.
external elastic lamina not evident evident absent
another name elastic A muscular A.
function

14. Capillary A diffuse network of thin tubules between A. and V.
the main place for substance interchange

15. ? Characters 1. distribution (everywhere) -----very wide
total length (60,000 km) very long
total area(6000 m2 ) very large
2. lumen (6~8μm) very narrow
3. blood current very slow
4. wall very thin ?

16. Structure of the wall
-Endothelium
-Basal membrane
-Pericyte周细胞

17. 3 Types Of Capillaries in EM
Continuous capillary 连续性毛细血管
Fenestrated capillary有孔毛细血管
Sinusoid血窦

18. Fenestrated capillary Sinusoid
endothelium
basal membrane
cell junction
Continuous capillary
Fenestrated capillary
Sinusoid
connective T.,muscle T.,nervous T.
kidney, intestine,
endocrine gland
liver, spleen, bone marrow

19. Continuous capillary
Fenestrated capillary
Sinusoid

20. Heart endocardium—L. C.T. myocardium-- the thickest layer
endothelium: simple squamous epi.
subendothelium: L.C.T.
subendocardium: L.C.T.
Purkinje fiber
myocardium-- the thickest layer
abundant cardiac muscle cells
Epicardium--L. C.T.
coronary blood vessels, nerves
mesothelium
( visceral layer of the pericardium)

21. En endothelium
SEn subendocardial layer
P conducting (Purkinje) fibers
M muscle fibers

22. Mes mesothelium
N autonomic nerves
M myocardium
CT loose connective tissue
Ep epicardium F
fat

23. Development of Cardiovascular System
It derives from mesoderm 中胚层
Establishment of
the early blood circulation
Development of the heart *
Congenital malformation *

24. Establishment of the
early blood circulation (3rd week)

25. endothelium blood stem cell
blood islands
endothelium blood stem cell

27. extraembryonic
embryonic
blood stem cells

28. these capillaries differentiate to:
arteries, veins & capillaries

29. 2. Development of the heart★
formation of endocardial heart tubes
change of location of heart tube
establishment of heart’s shape
partition of the heart
the congenital malformations

30. (1) Formation of endocardial heart tubes
cardiogenic area
生心区

31. *endocardial heart tubes
*paired tubes fuse into single

32. *heart tube link up with blood vessels
(embryo, connecting stalk, chorion & yolk sac)
－primitive cardiovascular system

33. (2) Change of location of heart tube
*ventral to the foregut 前肠
*caudal to the oropharyngeal membrane

34. (3) Establishment of heart’s shape
① elongation
bulbus cordis 心球
Ventricle 心室
Atrium心房
sinus venosus 静脉窦
② dilatation
bulbus cordis － truncus arteriosus 动脉干
sinus venosus － veins

35. truncus arteriosus
bulbus cordis
ventricle
atrium
sinus venosus
veins

36. bulboventricular loop 球室袢
③ curvature formation
bulboventricular
loop 球室袢
( U-shaped )

37. bulbus cordis
*atrium
foregut

38. ④ narrowing atrium – ventricle atrioventricular canal 房室管

39. (4) Partition of the heart *
primitive heart：one atrium
one ventricle
atrioventricular canal
atrium
ventricle
bulbus cordis
partition of

40. dorsal endocardial cushion 心内膜垫 ventral endocardial cushion
① partition of the atrioventricular canal 房室管
dorsal endocardial cushion 心内膜垫
ventral endocardial cushion

41. septum primum 第一房间隔（原发隔） foramen primum 第一房间孔（原发孔）
② partition of the primitive atrium
septum primum 第一房间隔（原发隔）
foramen primum 第一房间孔（原发孔）
foramen secundum 第二房间孔（继发孔）
septum secundum 第二房间隔（继发隔）
foramen ovale 卵圆孔

42. * thin membrane from dorsocranial wall
* caudal free edge & the endocardial cushion
septum primum
foramen primum

43. * foramen secundum appears in the
cranial part of the septum primum
* foramen primum is closed
foramen secundum

44. septum secundum foramen ovale
*ventrocranial wall *thick membrane
*on the right side *covers the foramen
secundum from the right side
腹颅侧壁
心脏模型

45. foramen primum
(disappear)
septum primum :
(thin membrane)
foramen secundum
(cranial part)
septum secundum :
(thick membrane)
foramen ovale
(caudal part)

46. Before birth
blood in right atrium
foramen ovale
left atrium

47. After birth pulmonary blood circulation starts to work
pressure in left
atrium increase

48. foramen ovale - close - by valve
valve fuses with the
septum secundum
- interatrial septum

49. interventricular septum 室间隔
③ Partition of the primitive ventricle
interventricular septum 室间隔
muscular interventricular septum
membranous interventricular septum

50. muscular interventricular septum
endocardial cushions
interventricular foramen 室间孔
apex

51. membranous interventricular septum
bulbar ridges 球嵴 (left & right)
muscular interventricular septum
endocardial cushions

53. & the truncus arteriosus 动脉干
④ Partition of the bulbus cordis 心球
& the truncus arteriosus 动脉干
two large arteries: aorta
pulmonary trunk

54. two ridges － in the walls of the
bulbus cordis & truncus arteriosus
－bulbar ridges ( left & right )

55. two ridges grow & fuse together
aorta
pulmonary trunk
two ridges grow & fuse together
－ aorticopulmonary septum 主肺动脉隔

56. ascending aorta & pulmonary trunk twist around each other

57. aorticopulmonary septum is not coronal
but spiral
aorticopulmonary septum is not coronal
or sagittal in orientation

58. (5) The congenital malformations

59. ① atrial septal defects 房间隔缺损
normally

60. § The septum primum is absorbed excessively

61. § The septum secundum developed poorly

63. § The septum primum is fenestrated

64. * The septum primum can’t cover the foramen ovale completely
* interatrial shunting of blood
blood left → right
pulmonary circulation↑ infection
body circulation↓ development

65. ② ventricular septal defects 室间隔缺损
muscular *membranous
septal defects

66. a combination of four cardiac defects:
③ Tetralogy of Follot 法乐四联症
a combination of four cardiac defects:
*pulmonary stenosis 肺动脉狭窄
*membranous ventricular septal defect 室间隔膜部缺损
*overriding aorta 主动脉骑跨
*hypertrophy of the right ventricle
右心室肥大

68. This malformation results from the right
of bulbus cordis partition
(aorticopulmonary septum)

69. right → left blood diversion

70. Clinical symptom:
* Cyanosis of the lips and fingernails
“blue baby”
* Short of oxygen, easy to be tired.
* Poor growth and development

71. The end