Biology詞匯一問

Biology詞匯
A blind-ended vessel (盲端管)is a vessel that is closed at one end(掘頭), or has a'dead end'(唔通).
dead end n. an end of a passage, such as a street or pipe, that affords no exit.
blind adj. closed at one end: a blind alley, having no opening: a blind wall.
Lymphatic capillaries(毛细淋巴管) are blind-ended tubes(盲端管)呢句個blind-ended(盲端)意思係「掘頭嘅,通唔到嘅」。



Lymphatic capillaries(毛细淋巴管) are blind-ended tubes(盲端管)in which adjacent endothelial cells overlap each other, forming flaplike minivalves.
Although they are similar to blood capillaries, lymphatic capillaries are so permeable that scientists used to think they were open at one end like a straw. Now, scientists have discovered that they owe their unique permeability to two specific structural modifications.The endothelial cells that form the walls of lymphatic capillaries are not tightly joined. Instead, the cells edges overlap each other loosely, forming easy opening flaplike minivalves.
Collagen filaments anchor the endothelial cells to surrounding structures so that any increase in interstitial fluid volume opens the minivalves, rather than causing the lymphatic capillaries to collapse.
So, what we have is a system with blind-ended tubes which is very similar to a bunch of one-way swinging doors. When fluid pressure in the interstitial space is greater than the pressure in the lymphatic capillaries, the minivalve flaps open, allowing fluid to enter the lymphatic capillary. However, when the pressure is greater inside the lymphatic capillary, it forces the endothelial minivalve flaps shut, preventing lymph from leaking back out as the pressure moves it through the vessel.

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Distibution and special features of lymphatic capillaries. (a) Structural relationship between a capillary bed of the blood vascular system and lymphatic capillaries. (b) Lymphatic capillaries are blind-ended tubes in which adjecent endothelial cells overlap each other, forming flaplike minivalves.

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