The Morphological Structure And Development Of Hedgehog Quill

Hedgehog is a kind of animal with special shape, in order to curl into a ball to fightagainst enemies,it evolves its own unique structure and defense mechanism of skin.Theadult hedgehog has quills on the back and the side of the body, and the other part iscovered by hair. The differences between dorsal and ventral hair follicle make it a naturalmutant. It is helpful to further reveal the hair follicle morphogenesis mechanism byexploring the reasons to this difference. In this study, based on the accumulation ofmorphological observation, tissue sections, HE staining and immunohistochemicaltechnology,we try to describe its histological features,alkaline phosphatase expressionand cell proliferation. Using embryos of different periods, we do some further study fromthe developmental level of hedgehog spines to the subcutaneous muscle morphogenesisand function. Conclusions as the following:1.Judging from the embryonic development, the formation of back quill of hair folliclesis earlier, following is the thickening of the dermis layer, the subcutaneous muscledevelopment is slightly behind the hair follicles, and tend to complete gradually after birth.The development of the abdominal hair follicle lag behind the back, the dermal layer isvery thin, subcutaneous muscle is underdeveloped. The development process of quills hasgone through a period of the pre-placode stage, placode stage, hair germ stage, hair pegand hair follicles. It has the similar developmental form as ordinary hair follicles,just thehair bud has a larger size. When it comes to hair germ, forked channels appear in thedermal papilla,this is conducive to the migration of mesenchyme and build a large hairfollicles.2.ALP(alkaline phosphatase) is highly active in the anagen in dermal papilla anddermal sheath, migrating upper in hair germ period, and disappear with the apoptosis ofmedullary cell. In the early developmental stage of embryonic quills, the expression of theALP in the dermis covers a wide range of areas, but weakening gradually with thedevelopmental process with a strict limitations in the dermis of the individual after birth.The expression pattern and the activity of hair follicle growth is positively correlated,indicating that ALP expression and induction of hair follicles are closely linked.3.In the developmental process of the quill bulbs, medulla, dermal sheath and dermallayers all show a strong proliferation potential. However, the real active site for theproliferation is mesenchyme migrating to the front of the channel, which explains themigration of DP cells are of vital importance to the formation of the quills. 4.The arrector pili muscle is very well developed at the back of hedgehog quills,belonging to the smooth muscle, connecting with the adjacent quills, shrunken tractionerected quills in different directions, while there is no significant arrector pili muscle in thesubcutaneous abdomen. Arranged parallel to the subcutaneous muscle layer is very welldeveloped in the back,but is significantly thinner in the abdomen.Dorsal and abdominalsubcutaneous muscle layer both belong to skeletal muscle, and display the positive signalin fast skeletal muscle myosin, which may give hedgehog the ability to curl. It is the thecomplex subcutaneous muscular system providing organically cooperated to ensure theeffective defense mechanism of hedgehog.