| The microstructure on the alveoli and alveoli septum between Datong yak(elevation 3800～4800m) with one fourth wild blood and plain yellow cattle(below elevation 500 meters) with same growth stages in different growth stage(1 day old ,30 days old ,180 days old and adult) were observed and measured in morphology by light microscopy and computer image colleting and analyzing system on the growth science in this research paper. The result indicated as follows:The mean single pulmonary alveoli area of yak is increasing from newborn to adult, In the corresponding of mean pulmonary alveoli number in unit area is gradually decreasing; alveoli septum is thickest (P<0.05)and cell component in alveoli septum is the most obvious; The thickness of alveoli septum in 1 day old is thinnest(P<0.05),The thickness of alveoli septum in 180 days old is thickest than that in 1day old(P<0.05),but thinner than that in 30 days old and adult(P<0.05). Alveoli area in unit area in 30 days old is the smallest (P<0.05) and the difference between other three groups is not obvious(P>0.05).There are a lot of structure like alveolar sac in 1 day old yak lung and secondary septa is short and small in that sacs.Mean single pulmonary alveoli area of plain yellow cattle also is increasing along with the age increaseing, in the corresponding to the pulmonary alveoli number in the unit area decreases gradually; The alveoli septum is the thickest (P<0.05)in 30 days old and is the thinnest (P<0.05) in 1 day old, but the alveoli septum thickness is not significance between 180th day and adult (P>0.05);cell component is very obvious in 30 days old;In the unit area pulmonary alveoli area of adult is biggest (P<0.05), other three groups are not significance (P>0.05); When in 30 olds day there is same structure to resemble alveolar sac near pulmonary pleura and secondary septa also is short and small. To compare same developmental stage yak and plain yellow cattle, yak's unit area pulmonary alveoli number are less than the plain yellow cattle's (P<0.05) between 1st day and 30th day, but single pulmonary alveoli area is more(P<0.05). Between 180th day and adult results are not obviously significance (P>0.05); Except 180th day yak's mean alveoli septum thickness is more than yellow cattle's (P<0.05); Alveoli area in the unit area yak and yellow cattle significance is not obvious between 30th day and adult (P>0.05), but in 1 old day and in 180 olds day yak is bigger than yellow cattle (P<0.05); In lung development and growth stage there are gather structure that resemble alveolar sac in yak and yellow cattle lung, but former appear on 1st day, latter appears on 30th day.Conclusion: After birth the process and manner of alveolar growth in the yak and yellow cattle is similar in same aspects. Both alveolar is maturation essentially, has good breath ability.On 30th day both alveolar have a growth accumulation process. Alveolar will gradually expand along with body growing, as a result, single alveolar area will unceasingly increase. To compare alveolar growth between yak and yellow cattle, results are incomplete same and there are a lot of different morphology structures about yak to adapt high altitude hypoxia. At yak birth, its breath is very fierce, obviously expand, rapidly entered into the growth state; but newborn yellow cattle can satisfy to need oxygen when the alveoli is not transferred fully to breath, observing result is than the alveoli expanded incompetely. Obvious alveoli growth appears after 30th day. Besides growth transitional stage on 180th day, other age group yak's alveoli septa is thicker than plain yellow cattle, because capillary and elastic fiber should be rich and this situation provided the good histology basic to adapt high altitude hypoxia for yak.
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