●●●●● ●●●● ●●0 ●●● ●●●●
●●●●● ●●●● ●●0 血管:包括动脉、小动脉、毛细血管、小静脉和静脉等 ●●● ●●●● Endotheium Elastic tissue J Inner coat Connective tissue (outer coa Smooth muscle (middle coat Smooth muscle(middle coat) Basement membrane Connective tissue outer coat) Endothelum(inner coat brous (collagenous) tissue Artery Arteriole Figure 45.4 All blood vessels have an inner layer of endothelum, and capilaries are made of ittle more than endothelium, with no surrounding muscle Artenes and veins both have a layer of connective tissue and an elastic layer around the endothelium, a middle layer of smooth muscle which s much heavier in arteries, and an outer coat of connective tissue containing some smooth muscle cells. The arterial tree divides into small artenes, whose walls gradualy become thinner, the smallest artenes, called artenoles, have only a single layer of smooth musce around the endothelum, sometimes with collagen fibers and an elastic layer Venules, the smallest veins have a thin layer of collagen fibers: as they merge nto larger and larger veins, they acquire more and more smooth muscle and become typical veins
血管：包括动脉、小动脉、毛细血管、小静脉和静脉等
●●●●● ●●●● ●●0 Outer coat ●●●● emenI loose connective tissue Middle coat: elastic fibers and ARTERY addle basement smooth muscle Basement membrane: connective tissue elements including collagen fibers eBIc Somoni Figure 29.12 Structure of blood vessels The outer coat consists ot loose connective tissue The middle coat contains elastic fibers and smooth muscle The basement membrane consists of
Outer coat: loose connective tissue Middle coat: elastic fibers and smooth muscle Basement membrane: connective tissue elements including collagen fibers
●●●●● 静脉管壁内的辫膜 ●●●● ●●0 ●●●● 静脉中的血量比动脉中 的血量略多 静脉内壁上的辨膜可阻 止血液逆流 证ales Figure 45.5 The valves in veins are shaped ch that blood movino to cowar. the heam opens asch vaive As blood start to move as tre vale, thus rairaruing a
静脉管壁内的瓣膜 静脉中的血量比动脉中 的血量略多。 静脉内壁上的瓣膜可阻 止血液逆流
●●●●● 毛细血管( capillaries):血管中最纤细的部分,管径不过4-12μm, ●●●● ●●0 管壁只有一薄层内皮细胞。 ●●●● Endothelia 10. 4 nn wide Nucleus Pericapillary space Basement membrane wth inert tia fluid (mucooasaccharides and collagen fibers) rgure 45.16 koss secton through a capillary shows it is made of thin men ot the canary, an neen in this eiectron mere CHash. The spaces between the cotn function as roomeial ceis that fit together like arved paving bocks Materals Substances cross the canary war chuse easy over the short distances separating the biood from the en in semicon 1, and by
毛细血管（capillaries): 血管中最纤细的部分，管径不过4－12µm， 管壁只有一薄层内皮细胞