06-00
Vascular System
06-00 Vascular System

06 Menu 1
06-00. Vascular System

06-16. Venule， transverse section. Rat pancreas， epon section， toluidinblue stain， x 400.

06-001. Blood Vessels. Capillaries， Arterioles， Venules，Small arteries and small veins.

06-17. Small vein， transverse section. Human， H-E section，x 400.

06-01. Capillary， longitudinal section. Human， H-E stain， x 125.

06-18. Small vein， transverse sectioned. Human， H-E stain， x 160.

06-02. Arteriole and capillaries. Human， H-E stain， x 100.

06-19. Small vein， transverse section. Human， H-E stain， x 160.

06-03. Capillaries and venule. Human， H-E stain， x 125.

06-20. Small vein， transverse section. Human， H-E stain， x 64.

06-04. Scheme showing two types of capillaries.

06-21. Small vein， longitudinal section. Human H-E stain， x 100.

06-05. Capillaries， transverse and longitudinal sections. Rat， epon section， toluidin-blue stain， x 400.

06-002. Valves of Veins

06-06. Capillaries in the subepitheliar connective tissue of the intestinal vilus. Human， H-E stain， x 400.

06-22. Valves of small vein， longitudinal section. Monkey， H-E stain， x 160.

06-07. Capillaries beneath the intestinal epithelium. Human， H-E stain， x 160.

06-23. Valves of femoral vein 1. Human， H-E stain， x 2.5.

06-08. Arteriole and venule， transverse section. H-E stain， x 250.

06-24. Valves of femoral vein 2. Human， H-E stain， x 25.

06-09. Arteriole. longitudinal section. H-E stain， x 160.

06-003. Arteries

06-10. Small artery， longitudinal section. Human ， H-E stain， x 64.

06-25. Artery of muscular type， transverse section. Monkey， H-E stain， x 30.

06-11. Small artery， longitudinal section. Bovine， resorcin-fuchsin and hematoxylin stain， x 160.

06-26. Arteria radialis， transverse section. Human， H-E stain， x 10.

06-12. Small artery， transverse section. Bovine， orcein and Kernechtrot stain， x 160.

06-27. A. femoralis， transverse section 1. Human， H-E stain，x 30.

06-13. Venule， longitudinal section. Human， H-E stain， x 160.

06-28. A. femoralis， transverse section 2. Human， resorcin-fuchsin stain， x 30.

06-14. Venule， surface view of the endothelial cells. Human， H-E stain， x 160.

06-29. Aorta， transverse section， 1. Human， H-E stain， x 25.

06-15. Venule， longitudinal section. Human， H-E stain， x 160.

06 Menu 2
06-30. Aorta， transverse section， 2. Human， resorcin-fuchsin stain， x 25.

06-006. Lymphatics

06-004. Veins

06-44. Lymphatic capillaries. Human， H-E stain， x 160.

06-31. V. cava inferior， transverse section， 1. Human， H-E stain， x 40.

06-45. Artery， vein and lymphatic vessel. Monkey， H-E stain，x 100.

06-32. V. cava inferior， transverse section， 2. Human， resorcin-fuchsin stain， x 40.

06-46. Small lymphatic vessel. Human， H-E stain， x 160.

06-33. V. cava superior， transverse section， 1. Human， H-E stain， x 40.

06-47. Valves of a small lymphatic vessel. Human， H-E stain，x 64.

06-34. V. cava superior， 2. Human， resorcin-fuchsin stain， x 40.

06-48. Lymphatic vessel， transverse section， 1. Human， H-E stain， x 100.

06-35. V. portae， transverse section， 1. Human， H-E stain，x 2.6.

06-49. Lymphatic vessel， transverse section， 2. Human， H-E stain， x 64.

06-36. V. portae， transverse section， 2. Human， H-E stain， x 40.

06-50. Ductus thoraticus， transverse section. Human， H-E stain， x 15.

06-37. V. basilica， transverse section. Human， H-E stain， x 10.

06-007. Heart

06-38. V. cephalica， transverse section. Human， H-E stain， x 10.

06-51. Wall of the left ventricle. Human， H-E stain， x 1.5.

06-39. V. saphena magna， transverse section. Human， H-E stain， x 10.

06-52. Wall of the right atrium. Human， H-E stain， x 2.5.

06-40. Vein in the spermatic cord， transverse section. Human， H-E stain， x 25.

06-53. Endocardium and myocardium. Human， H-E stain， x 25.

06-005. Large arteries and veins

06-54. Myocardium. Human， H-E stain， x 25.

06-41. A. carotis interna and V. juglaris interna， transverse section. Human， H-E stain， x
2.3.

06-55. Epicardium and myocardium. Human， H-E stain， x 25.

06-42. A. iliaca externa and V. iliaca externa， transverse section. Human， H-E stain， x
2.3.
06-43. A. femoralis and V. femoralis， transverse section. Human， H-E stain， x 2.3.

06-56. Sinus node. Human， M-G stain， x 4.0.

06-001
Blood Vessels.
Capillaries,Arterioles,Venules,
Small arteries and small veins.
06-001 Blood Vessels.

06-01 Capillary， longitudinal section. Human， H-E stain， x 125.

06-02 Arteriole and capillaries. Human， H-E stain， x 100.

Venule06-03 Capillaries and venule. Human， H-E stain， x 125.

Nucleus

Basement lamina
Pores
Cytoplasm ofendothelial cell06-04 Scheme showing two types of capillaries.

NucleusJunction ofendothelial cells

06-05 Capillaries， transverse and longitudinal sections. Rat， epon
section， toluidin-blue stain， x 400.

06-06 Capillaries in the subepitheliar connective tissue of the intestinal vilus. Human，
H-E stain， x 400.

06-07 Capillaries beneath the intestinal epithelium. Human， H-E stain， x 160.

VA

06-08 Arteriole and venule， transverse section. H-E stain， x 250.

A

V

06-09 Arteriole. longitudinal section. H-E stain， x 160.

06-10 Small artery， longitudinal section. Human ， H-E stain， x 64.

Lumen06-11 Small artery， longitudinal section. Bovine， resorcin-fuchsin andhematoxylin stain， x 160.

06-12 Small artery， transverse section. Bovine， orcein and Kernechtrot stain， x 160.

Nerve06-13 Venule， longitudinal section. Human， H-E stain， x 160.

06-14 Venule， surface view of the endothelial cells. Human， H-E stain， x 160.

06-15 Venule， longitudinal section. Human， H-E stain， x 160.

06-16 Venule, transverse section. Rat pancreas, epon section, toluidinblue stain, x 400.

06-17 Small vein， transverse section. Human， H-E section， x 400.

06-47 Valves of a small lymphatic vessel. Human， H-E stain， x 64.

06-19 Small vein， transverse section. Human， H-E stain， x 160.

06-20 Small vein， transverse section. Human， H-E stain， x 64.

06-21 Small vein， longitudinal section. Human H-E stain， x 100.

06-002
Valves of Veins
06-002 Valves of Veins

06-22 Valves of small vein， longitudinal section. Monkey， H-E stain， x 160.

06-23 Valves of femoral vein 1. Human， H-E stain， x 2.5.

06-24 Valves of femoral vein 2. Human， H-E stain， x 25.

06-003
Arteries
06-003 Arteries

A

M

I

①
06-25 Artery of muscular type， transverse section. Monkey， H-E stain， x 30.

②

06-26 Arteria radialis， transverse section. Human， H-E stain， x 10.

Lamina elastica interna

Lamina elastica
externa

06-27 A. femoralis， transverse section 1. Human， H-E stain， x 30.

Lamina elastica interna

Laminaelastica
externa

06-28 A. femoralis， transverse section 2. Human， resorcin-fuchsin stain， x 30.

Tunica intima

Tunica media

Tunica avdentitia

06-29 Aorta， transverse section， 1. Human， H-E stain， x 25.

Tunica intima

Tunica media

Tunica adventitia

06-30 Aorta， transverse section， 2. Human， resorcin-fuchsin stain， x 25.

06-004
Veins
06-004 Veins

Tunica adventitia

06-31 V. cava inferior， transverse section， 1. Human， H-E stain， x 40.

Tunica adventitia

06-32 V. cava inferior， transverse section， 2. Human， resorcin-fuchsin stain， x 40.

Tunica adventitia

06-33 V. cava superior， transverse section， 1. Human， H-E stain， x 40.

06-34 V. cava superior， 2. Human， resorcin-fuchsin stain， x 40.

06-35 V. portae， transverse section， 1. Human， H-E stain， x 2.6.

06-36 V. portae， transverse section， 2. Human， H-E stain， x 40.

06-37 V. basilica， transverse section. Human， H-E stain， x 10.

06-38 V. cephalica， transverse section. Human， H-E stain， x 10.

06-39 V. saphena magna， transverse section. Human， H-E stain， x 10.

06-40 Vein in the spermatic cord， transverse section. Human， H-E stain， x 25.

06-005
Large arteries
and veins
06-005 Large arteries and veins

06-41 A. carotis interna and V. juglaris interna， transverse section. Human，
H-E stain， x 2.3.

06-42 A. iliaca externa and V. iliaca externa， transverse section. Human， H-E stain， x 2.3.

06-43 A. femoralis and V. femoralis， transverse section. Human， H-E stain， x 2.3.

06-006
Lymphatics
06-006 Lymphatics

06-44 Lymphatic capillaries. Human， H-E stain， x 160.

V
L
A

06-45 Artery， vein and lymphatic vessel. Monkey， H-E stain， x 100.

06-46 Small lymphatic vessel. Human， H-E stain， x 160.

06-47 Valves of a small lymphatic vessel. Human， H-E stain， x 64.

06-48 Lymphatic vessel， transverse section， 1. Human， H-E stain， x 100.

06-49 Lymphatic vessel， transverse section， 2. Human， H-E stain， x 64.

06-50 Ductus thoraticus， transverse section. Human， H-E stain， x 15.

06-007Heart
06-007 Heart06-51 Wall of the left ventricle. Human， H-E stain， x 1.5.

06-52 Wall of the right atrium. Human， H-E stain， x 2.5.

06-53 Endocardium and myocardium. Human， H-E stain， x 25.

06-54 Myocardium. Human， H-E stain， x 25.

N

L
L

06-55 Epicardium and myocardium. Human， H-E stain， x 25.

06-56 Sinus node. Human， M-G stain， x 4.0.

06-00 Vascular System• The vascular system circulates the blood throughout the whole body and throughthis carries oxygen， nutritive materials， hormones， and other signaling
molecules to the tissues and collects from them carbon dioxide and othermetabolic waste products to be transported to the excretory organs forelimination. This system is made up of muscular pump， the heart and two
vascular systems. The one is pulmonary circulation， which carries blood to andfrom the lung， where the exchange oxygen and carbon dioxide between bloodand air takes place. The other is the systemic circulation， which distributes the
blood to and collects from all of the other tissues and organs of the body.
• In both of these circulation the blood is pumped from the heart， passes
successively through large arteries， small arteries， arterioles capillaries，
venules， small veins， and large veins， and back to the heart. The actual
exchange between the blood and the tissues takes place in the minute thin-walledcapillaries and venules.
• The liquid component of the blood partly exudes from the capillaries and becomes
lymph filling the tissue space and enters in the lymph capillaries.

06-001 Blood Vessels. Capillaries， Arterioles， Venules，Small arteries and small veins.

06-01 Capillary， longitudinal section. Human， H-E stain， x 125.

• This is a longitudinally sectioned capillary found in the subcutaneousconnective tissue. The capillaries are about 8μｍ in caliber and its wallconsists exclusively of the endothelial cells， whose cytoplasm is extremely
attenuated looking in sections as a thin line and nuclei ( en ) are fusi-form orlong elliptic in shape and extrude outside as well as inside. Here and there
capillaries are encircled by pericytes ( pc ). The empty circles in the right halfof this figure are fat cells ( fat ).

06-02 Arteriole and capillaries. Human， H-E stain， x 100.

• This is an arteriole passing into the capillaries found in the dermis of human
lip. An arteriole goes from bottom left of this figure right upward and at thearrow， the last smooth muscle fiber of the arteriole， passes into a
capillary running right ward and dividing two and each arriving at the top
right corner and bottom right corner of this figure respectively. The arteriole
has transversely enclosing smooth muscle fibers， whereas the capillaries
have not.

06-03 Capillaries and venule. Human， H-E stain， x 125.

• Here three capillaries， being in the right half of the figure， meet together
and become a venule with about double caliber (in the left half of the figure).
The capillaries are encircled exclusively by the endothelium but around thevenule beside the endothelium some pericytes are seen. Empty circles are
fat cells.

06-04 Scheme showing two types of capillaries.

• In the electron micrographs two types of capillaries are identified.
①. Capillaries without fenestration: In this type cytoplasm of the endotheliar
cells has no pores， fenestrations， and encloses the lumen completely.
Capillaries of this type are found in the pulmonary alveoli and in the brain.
②. Capillaries with fenestration: In this type cytoplasm of the endothelial
cells has large number of minute pores， fenestrations. The caliber of thepores vary greatly according to the organs. Capillaries of this type are found in
the renal glomeruri， in the endocrine glands， and in the intestinal vili.

06-05 Capillaries， transverse and longitudinal sections. Rat， epon section，
toluidin-blue stain， x 400.

• In this figure a transverse section ( center ) and a longitudinal section ( upper
left corner ) of capillary， found in the rat pancreas， are shown. The
transverse section， containing two erythrocytes， shows the nucleus
extruding out side and very thin cytoplasm enclosing the lumen. The
longitudinal section shows a long lumen limited by the thin cytoplasm and avery elongated nucleus.

06-06 Capillaries in the subepitheliar connective tissue of the intestinal vilus.
Human， H-E stain， x 400.

• In this figure， directly beneath the epithelium， simple columnar withstriated border， two capillaries ( arrows ) are seen. The right one
containing one erythrocyte consists of a single endothelial cell， nucleus ofwhich extrude downwards and the cytoplasm encloses the lumen as a thin
faint circle. The left one containing four erythrocytes consists of two
endothelial cells and their nuclei locate at the bottom and top of the lumen，
respectively. These capillaries are surrounded by a very loose connective
tissue.

06-07 Capillaries beneath the intestinal epithelium. Human， H-E stain， x 160.

• Beneath the intestinal epithelium there is a very dense capillary network toprovide the nutriment to the epithelium and at the same time to accept
glucose and amino acids from the epithelium. This figure shows the dense
network of the capillaries at the tip of an intestinal vilus. Numerous capillaries( arrows ) line the epithelium.

06-08 Arteriole and venule， transverse section. H-E stain， x 250.

• These arteriole (A) and venule (V) are found in the subcutaneous tissue ofhuman thumb tip. The wall of the arteriole consists of endothelial cells，transversely sectioned， four smooth muscle cells， encircling theendothelium， and some fibroblasts， surrounding the arteriole. The lumenof the venule is wide and encircled by endothelial cells， nuclei of which areflat fusiform， and collagenous fibers containing some pericytes.

06-09 Arteriole. longitudinal section. H-E stain， x 160.

• This is a longitudinally sectioned arteriole， of about the same caliber with
06-08.
• The lumen is limited by the endothelial cells. Their nuclei appear flat andlong spindle-shape， with long axis coincide with that of the arteriole. The
endothelial cells are encircled by a single layer of smooth muscle cells，sectioned transversely， and further outside wrapped by a thin layer of
longitudinally running collagenous fibers.

06-10 Small artery， longitudinal section. Human ， H-E stain， x 64.

• This is a longitudinal section of a small artery， of about 0.1 mm in caliber，
which shows already the typical structure of three layers: tunica intima，
tunica media and tunica adventitia.
• The tunica intima consists of endothelial cells and a small amount of
subendothelial connective tissue. The endothelial cells are flat long spindleshaped and arrange their long axis coinciding with that of the vessel.
• The tunica media consists of smooth muscle cells， encircling the lumen andmaking a thick layer. In this small artery， number of muscle cell layers isabout ten.
• The tunica adventitia is a layer of collagenous fibers running longitudinal andspiral.

06-11 Small artery， longitudinal section. Bovine， resorcin-fuchsin andhematoxylin stain， x 160.

• This is a longitudinally sectioned small artery. Resorcin-fuchsin stained elastic
fibers deep violet and hematoxylin nuclei deep blue. The longitudinalarrangement of the endothelial nuclei is evident. Beneath the endothelium
there is a thin layer consisting of elastic fibers， running loose spiral. This iscalled lamina elastica interna ( arrows ).
• The tunica media consists of smooth muscle cells， encircling the lumen，and contains elastic fibers very few. The nuclei of smooth muscle cells are
sectioned transversely.
• The tunica adventitia consists of loose connective tissue， whose fibers run
longitudi- nal or loose spiral. Directly neighboring with the media there is athin layer of longitu- dinally running fine elastic fibers. This is called lamina
elastica externa ( arrow heads ).

06-12 Small artery， transverse section. Bovine， orcein and Kernechtrot stain， x 160.

• This is a transversely sectioned small artery. Orcein stains elastic fibers deepbrown and Kernechtrot nuclei light pink.
• As a post mortem phenomenon， smooth muscle fibers of the media
contruct， so that the lumen and the intima are compressed， resulting in
the zigzagging of lamina elastica interna ( arrow ). As to the lamina elastica
extern such zigzagging is not conspicuous.

06-13 Venule， longitudinal section. Human， H-E stain， x 160.

• This is a longitudinally sectioned venule found in the subcutaneous tissue.
The wall of this venule consists of only endothelial cells and a few pericytes.
The connective tissue coat is only faint. At the left extremity of this venule，
three endothelial nuclei show the surface view ( arrow ). At lowermost partof this figure a thin nerve runs windling horizontally.

06-14 Venule， surface view of the endothelial cells. Human， H-E stain， x 160.

• This is the surface view of the endothelial cells of a venule. Nuclei of theendothelial cells appear lightly stained oval with the long axis roughly
coincide with that of venule， and cell boundary shows long hexagon.

06-15 Venule， longitudinal section. Human， H-E stain， x 160.

• This is a venule of about 20μｍ in caliber， whose wall is a little thicker than
06-13， but consists of mainly connective tissue. Attaching to theendothelium several pericytes are recognized.

06-16 Venule， transverse section. Rat pancreas， epon section， toluidinblue
stain， x 400.

• This is a transversely sectioned venule found in the pancreas， of about 30μｍ in caliber. The lumen is encircled by two endothelial cells and aconspicuous pericyte surrounds the lower half of this venule. Around thisvenule are the pancreatic acini， filled with secretion granules.

06-17 Small vein， transverse section. Human， H-E section， x 400.

• This is a higher magnification of a small vein， of about 50μm in caliber，
whose wall consists of only endothelium， two pericytes and a very thinlayer of collagenous fibers.

06-18 Small vein， transverse sectioned. Human， H-E stain， x 160.

• This is a small vein of about 80μｍ in caliber， whose wall is still very thinconsisting of only endothelium， several pericytes and thin wrapping ofcollagenous fibers. Around this vein several capillaries or venules arefollowing.

06-19 Small vein， transverse section. Human， H-E
stain， x 160.

• This is a small vein of about 150μｍ in caliber found in the subcutaneous
tissue of human lip. The wall of this vein consists of three layers， namelytunica intima， tunica media and tunica adventitia. The intima consists ofthe endothelium and underlying scant connective tissue. The media is
composed of loosely arranged circular smooth muscle cells， each of which
is separated by the connective tissue fibers. The adventitia is a relatively
thick layer of collagenous fibers running loosely spiral. Neither lamina
elastica interna nor lamina elastica externa exist.

06-20 Small vein， transverse section. Human， H-E stain， x 64.

• The wall of this vein is apparently densely composed but its constituents aremainly collagenous fibers and circular smooth muscle fibers are scant.

06-21 Small vein， longitudinal section. Human H-E stain， x 100.

• This is a longitudinally sectioned small vein， of about the same caliber of
06-20. The apparently thick composed wall consists mainly of collagenous
fibers running loosely spiral and the circular smooth muscle fibers are only
scattered.

06-002 Valves of Veins• Venous flow toward the heart is derived by the negative pressure caused by
the diastole of the right atrium. To facilitate this flow， medium-sized veinshave numerous valves that prevent flow of blood away from the heart. Eachof the two opposing semilunar valve leaflets is a thin fold of the intima，
consisting of endothelium and underlying connective tissue. The freemargins of valves project in the direction of blood flow. When blood is
flowing toward the heart， the cusps of the valves are flattened against thevessel wall， but if the blood flows backward， the edges of the valve
leaflets come into close apposition， preventing backflow. Valves areespecially numerous in the veins of the lower extremity where they facilitate
venous return. Valves are not formed in minute veins or in the very largeveins.

06-22 Valves of small vein， longitudinal section. Monkey， H-E stain， x 160.

• This is the longitudinally sectioned valves found in the intestinal submucosa.
Two valve leaflets are thin folds of the vein wall， consisting of connective
tissue covered by endothelium， starting from opposite regions. The space
between the valve leaflet and vein wall is called sinus of the valve， where
the wall is thin and often distended.

06-23 Valves of femoral vein 1. Human， H-E stain， x 2.5.

• This figure shows the femoral artery ( right ) and femoral vein ( left ). At
lower left corner two smaller veins confluent to the femoral vein， one ofwhich has typical valves ( arrow ). Higher magnification of these valves isshown in 06-24.

06-24 Valves of femoral vein 2. Human， H-E stain， x 25.

• Two thick valve leaflets consisting of connective tissue covered byendothelium project long into the lumen from the opposite regions of thevein wall. The connective tissue of the valves continues directly with that of
the intima of the vein..

06-003 Arteries

06-25 Artery of muscular type， transverse section. Monkey， H-E stain， x 30.

• This is a transversally sectioned artery of 0.5 mm in caliber showing typicalstructure of the muscular type artery. The wall of this artery consists of concentric
three layers: tunica intima ( I )， tunica media ( M )， and tunica adventitia ( A ).
• Tunica intima consists of endothelium and thin subendothelial connective tissue.
Beneath the endothelium there is a distinct refractive zizag line， lamina elastica
interna ( 1 ).
• Tunica media consists of densely packed circular smooth muscle fibers. The
thickness of this layer thickens roughly according to the caliber. Tunica media
contain scant elastic fibers.
• Tunca adventitia consists of collagen fibers running loose longitudinal spiral.
• In the innermost region elastic fibers intermingle with collagen fibers and thisregion is called lamina elastica externa ( 2 ). This is not conspicuous. Around theadventitia collagen fibers gradually merge with the surrounding connective tissue.

06-26 Arteria radialis， transverse section. Human， H-E stain， x 10.

• In this figure Arteria r4adialis and two concomitant veins are shown. A.
radialis， of muscular type， consists of three layers: tunica intoma ( I )，tunica media ( M ) and tunica adventitia ( A ). In this low magnification tunca
intima is difficult to perceive; tunica media is a thick layer of very densely
packed circular smooth muscle fibers; tunica adventitia consists of inner andouter sublayers: the inner sublayer contains fine elastic fibers amongcollafwnous fibers and shows in this figure reddish hue; the outer sublayer
consists of collagenous fibers showing dark reddish hue.

06-27 A. femoralis， transverse section 1. Human， H-E stain， x 30.

• This is a part of wall of the A. femoralis sectioned transversally. Tunica intima
consisting of the endothelium and scant subendothelial connective tissue.
Directly beneath the endothelium there is the distinctly refractive lamina
elastica interna ( arrow 1 ). Tunica media is a thick layer of densely packed
circular smooth muscle fibers. In the intern al half of the tunica adventitia
fine elastic fibers intermingle with collagenous fibers， so that this portion
shows light pink hue ( 2 ). The outer half of the tunica adventitia consists ofcollagenous fibers oriented loose longitudinal spirally and gradually merge
into the surrounding connective tissue.

06-28 A. femoralis， transverse section 2. Human， resorcin-fuchsin stain， x 30.

• This is the same specimen with 06-27， but stained the elastic fibers withresorcin- fuchsin. Both lamina elastica interna ( 1 ) and lamina elastica
externa ( 2 ) are very conspicuous. In the tunica media only very fine elastic
figers are seen， on the contrary， in the tunica adventitia there are
numerous elastic fibers beside the lamina elastica externa.

06-29 Aorta， transverse section， 1. Human， H-E stain， x 25.

• This is a part of wall of the transversely sectioned aorta. Aorta is the representativeof the elastic arteries. Their walls appear distinctly yellow in the fresh state due tothe abundance of elastin. The wall consists of also three layers: tunica intima，
tunica media and tunica adventitia.
• Tunica intima ( I ) consists of endothelium and underlying subendothelial
connective tissue， which is relatively thick and contains many medium sizedelastic fibers and in the deeper half longitudinally oriented smooth muscle fibers.
Because of these muscle fibers lamina elastica interna is difficult to perceive.
Arrow 1 indicates the endothelium and arrow 2， the border between tunica
intima and tunica media.
• Tunica media ( M ) is very thick and made up of multiple concentric， fenestrated
lamellae of elastin alternating with thin layers of circularly oriented smooth muscle
fibers. Compare with 06-30. .
• Tunica adventitia ( A ) is relatively thin and consists of collagenous fibers andelastic fibers. Lamina elastica interna ( 3 ) is not conspicuous.

06-30 Aorta， transverse section， 2. Human， resorcin-fuchsin stain， x 25.

• This is the same specimen with 06-29， but resorcin-fuchsin stained. Tunica
intima ( I ) contains many fine elastic fibers. Tunica media ( M ) is composedso densely of elastin lamellae， that the space of each smooth muscle fiberis hardly recognized. Tunica adventitia ( A ) contains many coarse elastic
fibers and lamina elastica externa is not evident.

06-004 Veins• Blood is carried back from the capillaries to the heart in veins. Veins
normally accompany the corresponding arteries， and as they progress
towward the heart they increase in diameter and their walls become thicker.
The walls of veins are thinner ， more supple， and less elastic than thoseof arteries. Veins show greater variations in their structure than do arteries，
and the same vein may vary in the wal of veins: tunica intima， tunica media
and tunica adventitia. But the boundaries of the layers are often indistinct.
The muscular and elastic components are not well developed in veins andconnective tissue components are more prominent.

06-31 V. cava inferior， transverse section， 1. Human， H-E stain， x 40.

• V. cava inferior is the largest vein and locates directly beneath the heart. The
wall of this vein is thick enough and consists of very thin tunica intima andtunica media and very thick tunica adventitia. Tunica intima (I) consists ofendothelium and scant subendothelial connective tissue. Tunica media（M）is thin and consists mainly of connective tissue intermingled withseveral circularly oriented thin smooth muscle fiber bundles. Tunicas
adventitia（A）is、 on the contrary、 very thick and consists of mainly
longitudinally and spirally oriented collagenous fibers and numerous
longitudinally oriented thick smooth muscle fiber bundles.

06-32 V. cava inferior， transverse section， 2. Human， resorcin-fuchsin stain， x 40.

• This is the same section as 06-31， but the elastic fibers are visualized byresorcin- fuchsin stain. The elastic fibers are in general fine and evenly
distributed throughout the wall， but directly beneath the endothelium
they are somewhat densely accumulated. The thick smooth muscle fiber
bundles in the tunica adventitia are each enclosed by elastic fibers.

06-33 V. cava superior， transverse section， 1. Human， H-E stain， x 40.

• Vena cava superior locates just up the heart and blood comes into the rightatrium derived by the force of gravity. The wall is apparently thick but
consists of mainly thick collagenous fiber bundles intermingled with a few
smooth muscle fiber bundles. Tunica intima consists of the endothelium andscant underlying connective tissue and continues without distinct boundarywith tunica media in which several thin smooth mucle fiber bundles are seen.
Tunica adventitia is very thick consisting mostly of circularly or spirally
oriented thick collagenous fiber bundles intermingled with a few spirally
oriented smooth muscle fiberbundles. Arrow indicates the boundary
between tunica media and tunica adventitia.

06-34 V. cava superior， 2. Human， resorcin-fuchsin stain， x 40.

• The same specimen as 06-33， but stained with resorcin-fuchsin. In thetunica intima there is a layer of densely composed elastic fibers. Between
the tunica media and tunica adventitia no distinct boundary is recognizedand both consist of thin smooth muscle fibers enclosed by thin elastic fibers.
In the outer half region of tunica adventitia there are several spirally
oriented thick smooth muscle fiber bundles.

06-35 V. portae， transverse section， 1. Human， H-E stain， x 2.6.

• This is the transversely sectioned V. portae. The wall shows local variation of
thickness caused by the varying volume of smooth muscle fibers. At lower
left corner there is a small lymph node.

06-36 V. portae， transverse section， 2. Human， H-E stain， x 40.

• In this figure no distinct boundary between tunica intima and tunica media isseen. Directly beneath the endothelium there are thin smooth muscle
bundles oriented spirally. These continues with the tunica media consistingof loosely arranged similar thin smooth muscle bundles. On the contrary tothese， tunica adventitia consists of densely arranged coarse collagenous
fibers and a thick layer of longitudinally oriented smooth muscle fiber
bundles.

06-37 V. basilica， transverse section. Human， H-E stain， x 10.

• In the wall of this vein there are numerous thin smooth muscle fibers
arranged loosely circular-spirally. Further outside thick smooth muscle fibers
run spirally and outermost encircle the collagenous fibers. The tunica intima
consisting of endothelium and scant underlying connective tissue encircles
the lumen with irregular contour caused by the contraction of the smoothmuscle fibers of tunica media.

06-38 V. cephalica， transverse section. Human， H-E stain， x 10.

• The wall of this vein consists of loosely spirally oriented thin smooth muscle
fiber bundles and collagenous fibers.

06-39 V. saphena magna， transverse section. Human， H-E stain， x 10.

• In the wall of V. saphena magna tunica media develops well and consists ofrelatively densely arranged thin smooth muscle fiber bundles oriented
spirally. Tunica adventitia consists of collagenous fiber bundles oriented
mainly longitudinally and of a few number of relatively thick smooth muscle
fiber bundles oriented longitudinally. Tunica intima is very thin consisting
endothelium and scant underlying connective tissue.
• At the left extremity of this vein a small vain comes into this vein， where
valves are conspicuous. The upper and lower wall of this region wall is verythin and consists of only thin connective tissue.

06-40 Vein in the spermatic cord， transverse section. Human， H-E stain， x 25.

• Through this vein blood flows against the force of gravity from the testis
upward. The wall of this vein is specifically composed， namely， out sideof thin tunica media (M)， consisting of mainly circularly oriented smoothmuscle fibers， there is very thick tunica adventitia (A) consisting mainly of
longitudinally oriented thick smooth muscle fiber bundles， that facilitates
the upward blood flow by contraction of these muscle fiber bundles.

06-005 Large arteries and veins

06-41 A. carotis interna and V. juglaris interna， transverse section. Human，
H-E stain， x 2.3.

• This figure shows A. carotis interna (A) and V. juglaris interna (V). A. carotis
interna Is a elastic type arteria， consisting very thick and compact tunica
media. V. juglaris Interna has relatively thin wall. At middle of the upper walla large vein comes to join， where no valves are seen.

06-42 A. iliaca externa and V. iliaca externa， transverse section. Human， H-E
stain， x 2.3.

• This figure shows A. iliaca externa (A)， of muscular type， and V. iliaca
externa (V) having thick wall. In the upper region of this field， in the fat
tissue， a small lymph node and numerous thin lymphtics (arrows) arerecognized.

06-43 A. femoralis and V. femoralis， transverse section. Human， H-E stain， x 2.3.

• This figure shows A. femoralis (A) and V. femoralis (V). A. femoralis is ofmuscular type. The wall of V. femoralis shows irregularity in thickness causedby the irregular distribution of smooth muscle fiber bundles in tunica media
and tunica adventitia. At the right and left side of this wall valves are seen. In
the surrounding fat tissue numerous lymphatics， thick and thin， arerecognized.

06-006 Lymphatics• The lymphatics are the vessels， that accept the tissue fluid and send backto the heart， composing independent tubular system beside the bloodvessel system. On the course of lymphatics many lymph nodes are inserted.

06-44 Lymphatic capillaries. Human， H-E stain， x 160.

• The smallest lymphatic vessels are called lymphatic capillaries and are thinwalled， blindly ending tubules， which form a dense network in most of
tissues of the body. They collect tissue fluid， which is called lymph as soon
as it enters these capillaries. Lymphatic capillaries consist only of
endothelium and not accompanied by pericyte. Lymphatic capillaries areoften mistaken as rents of tissue.
• This figure shows the interlobular connective tissue of sublingual gland，containing two lymphatic capillaries ( ly )， blood capillaries ( cap )， a small
vein ( ven ) and a thin nerve ( ner ).

06-45 Artery， vein and lymphatic vessel. Monkey， H-E stain， x 100.

• These artery (A)， vein (V) and lymphatic vessel (L) are found in theinterlobular connective tissue of the submandibular gland. This figure shows
very well the structural differences of the wall of artery， vein and lymphatic
vessel.

06-46 Small lymphatic vessel. Human， H-E stain， x 160.

• The wall of this small lymphatic vessel， found in the subcutaneousconnective tissue， consists of only endothelium ( arrow ) accompanying
scant connective tissue. This vessel is filled with faintly pink stained
substance， this is a characteristic of the small lymphatic vessels.

06-47 Valves of a small lymphatic vessel. Human， H-E stain， x 64.

• This is found in the interlobular connective tissue of the submandibulal gland.
A thin lymphatic vessel comes from top right to down leftward and there
provides the valves. Two valve leaflets are thin， consisting endothelium andscant connective tissue. Distal portion of the valves lumen of the lymphatic
vessel is dilated.

06-48 Lymphatic vessel， transverse section， 1. Human， H-E stain， x 100.

• This small lymphatic vessel is found in the subcutaneous connective tissue ofthe lip， having a little thicker wall and containing the homogeneously lightpink stained substance. The wall consists of the endothelium and connective
tissue.

06-49 Lymphatic vessel， transverse section， 2. Human， H-E stain， x 64.

• This is found in the fat tissue surrounding the A. iliaca externa of 06-42. The
wall of this lymphatic vessel consists of three layers， i.e. tunica intima，
tunica media and tunica adventitia. Tunica intima consists of endothelium
and underlying connective tissue， tunica media of circularly oriented
smooth muscle fibers， and tunica adventitia of longitudinally and circularly
oriented collagenous fiber bundles.

06-50 Ductus thoraticus， transverse section. Human，
H-E stain， x 15.

• This is the transverse section of human ductus thoraticus. The lumen shows
irregular contour. The wall is irregularly composed: tunica intima consists ofthe endothelium and scant connective tissue， tunica media of mainly
longitudinally oriented smooth muscle fiber bundles， and tunica adventitia
of mainly longitudinally and spirally oriented smooth muscle fiber bundles
and coarse collagenous fiber bundles.

06-007 Heart• The heart is a muscular pump， which drives blood to circulate through thevessel system. The heart consists of four chambers: a right and left atrium
and a right and left ventricle. The venous blood comes into the right atrium
through the superior and inferior vena cava and from there passes to theright ventricle， then is send to the lung and aerated. The blood is broughtthen to the left atrium， and from hear to the left ventricle and thendistributed throughout the body by the aorta and its branches.
• The wall of the heart， in both the atria and the ventricles， consists ofthree layers: the internal， endometrium， the intermediate， myocardium，and the external， epicardium. The endocardium is in immediate contact
with the blood; the myocardium is the contractile layer; and the epicardium
is the visceral layer of the pericardium.

06-51 Wall of the left ventricle. Human， H-E stain， x 1.5.

• This is the transverse section of the left ventricle. Among the three layers the
myocardium is very thick， composing mostly the cardiac wall， andconsists exclusively of the meshworks of cardiac muscle fibers and very loose
connective tissue filling the meshes. The endocardium， contour at right，
and the epicardium， contour at left， are not perceived in thismagnification. The thick round sections at the right end of the wall aretransverse sections of papillary muscles.

06-52 Wall of the right atrium. Human， H-E stain， x 2.5.

• This is the transverse section of the right atrium. The upper contour is theendocardium and lower contour is the epicardium. The myocardium
occupies the wide space between the endocardium and the epicardium. The
thickness of the wall of the atrium is much thinner than that of the ventricle.

06-53 Endocardium and myocardium. Human， H-E stain， x 25.

• Except for the endocardium ( upper limit of this figure， indicated by a large
arrow)， all of this figure is occupied by the myocardium， upper one thirdof which is composed of the specialized conducting fibers. At right several
conducting fibers are connecting with the normal working cardiac muscle
fibers ( small arrows ). The lower two thirds of this figure consists of theworking cardiac muscle fibers.

06-54 Myocardium. Human， H-E stain， x 25.

• This figure shows the myocardium consisting of thick muscle fiber bundles，
among which in the fat tissue an artery runs tortuously.

06-55 Epicardium and myocardium. Human， H-E stain， x 25.

• The undermost limit of this figure， indicated by an arrow， is theendocardium， and the upper portion is myocardium， containing a thick
fat tissue layer in which a nerve and several lymph vessels ( L ) are seen.

06-56 Sinus node. Human， M-G stain， x 4.0.

• In the center the sinus node， occupying almost the whole thickness of wall，is shown.