Histological Structures And Numerical Analysis On Pulmonary Artery Of Yak At Different Ages

Several staining methods and microscope techniques were used to study the structure of yak's pulmonary artery at different ages to provide morphologically material to the mechanism of adapting chronic hypoxia. The results were as follows:1. The percentage of medial muscle thickness of pulmonary artery (MT%)in different age yaks increased at different levels when compared with other animals . The average percentage of medial muscle thickness of pulmonary artery in five-month-old yak was the highest and reached 13.84%. The MT% in one-day-old yak was lower than five-month-old yak and reached 13.66%. The MT% in adult yak was the lowest and reached 12.66%. When the outer diameter was less than 50μm, the MT% became the highest of 20.82%. The smooth muscles were abundant. It showed that hypoxia could affect the structure of artery. The change of pulmonary artery structure became most in diameter less than 50μm in five-month-old yak.2. We measured and analyzed the outer diameter in bronchus and its accompanied pulmonary arteries in different age yak. The outer diameters in bronchus and its accompanied pulmonary arteries in one-day-old, five-month-old and adult yaks were 642.19±443.16μm, 501.83±239.42μm and 736.30±309.97μm respectively. The outer diameter in primary bronchiole and its accompanied pulmonary arteries in one-day-old, five-month-old and adult yaks were 168.88±62.56μm, 217.71±131.32μm and 369.41±131.95μm respectively. The outer diameters in secondary bronchiole and its accompanied pulmonary arteries in one-day-old, five-month-old and adult yaks were 87.26±46.71μm, 91.38±28.70μm and 177.31±73.62μm, respectively. The outer diameters in terminal bronchiole and its accompanied pulmonary arteries in one-day-old, five-month-old and adult yaks were 51.32±17.65μm, 64.45±17.98μm and 136.59±64.41μm, respectively. The outer diameter in respiratory bronchiole and its accompanied pulmonary arteries in one-day-old, five-month-old and adult yaks were 35.37±12.48μm, 35.34±10.95μm and 64.70±23.36μm, respectively. The results showed that the outer diameter in primary bronchus, secondary bronchiole, terminal bronchiole and their accompanied pulmonary arteries increased with ages in yak. The outer diameters in bronchiole, respiratory bronchiole and accompany pulmonary arteries were different, highest in adult yak, lower in one-day yak, and lowest in five-month-old yak.3. Pulmonary arteries contained predominantly smooth muscle, till to the caliber of 17μm also had. The internal and external elastic laminae were clear in the pulmonary artery. The smooth muscle, elastic fibers and collagen fibers in the pulmonary artery were positively correlated with its outer diameter. The layer of smooth muscle in adult pulmonary artery was similar to that of five-month-old yak, and the layer of smooth muscle in one-day-old was the thinnest.4. The pulmonary arteries in different age yaks were mainly composed of the muscular and the elastic arteries. The proportion of the muscular and the elastic arteries was similar in different age yaks. There was a complete connective tissue lamina when the yak's pulmonary arteries'outer diameter was more than 101μm. The diameters of pulmonary arteries were positively correlated with the outer diameter of different bronchi. The muscular arteries were separated from their accompanied bronchi. The elastic arteries and transitional arteries were normally accompanied by bronchi and had a conjunct connective tissue sheath.