The hypodermis ✪ It is loose connective tissue which will connect the skin to the underlying organs and which will allow the skin to slide over these underlying organs. This hypodermis contains vessels, nerve endings, collagen fibers and adipocytes in varying quantities, these masses are called the adipose panicle. ✪ The vascularization of the skin. This vascularization does not exist in the epidermis because the epidermis are avascular structures and we only observe this vascularization in the dermis and hypodermis. 1- vascularization, the arterial plexus: we describe two of them. A superficial plexus located roughly between the papillary layer and the reticular layer of the dermis and a deep plexus located between the dermis and the hypodermis. These two plexuses are connected to each other by branches and from the superficial plexus between the papillary dermis and reticular dermis, there are numerous branches which leave and which vascularized the dermal papillae. 2- The venous plexuses: there are 3 of them. Two are strictly parallel to the arterial plexus, one between the hypodermis and the dermis and the other between the reticular dermis and the papillary dermis and another which is located between the two previous ones so here again there are veinlets which will arrive at the level of these plexuses. What is particular at the level of this dermis, it is the existence of arteriovenous anastomosis users who have the appearance of a tortuous canal which joins the arteriole to the venule without passing through the capillaries and which will connect these different plexuses. These arteriovenous anastomoses are common in thick skin, they are sometimes called glomus and these arteriovenous anastomoses will make it possible to short-circuit a certain vascular territory and this will make it possible to significantly vary the skin flow and therefore to vary the skin temperature. For example. So the activation of these anastomoses allows temperature regulation. ✪ Lymphatic vascularization These are blind bags located in the dermis and which roughly form networks parallel to the arterial plexus. So we saw what concerns the skin by the epidermal layer that, the dermis, the hypodermis and apart from the cells which constitute the dermis which are present in the dermis, there are annexes skin which we will describe one after the other: ✪ The pilot device-sebaceous is made up of hair and the sebaceous gland. These pilot devices sebaceous cells do not exist everywhere and in particular hair is only found in certain areas of the skin and not at the level of the palms or soles of the feet therefore not at the level of the thick skin.
✪ The hair is a keratinized structure which only exists in mammals and which is derived from the epidermis and therefore from an invagination of the epidermis. At the scalp level, there are approximately 500 hairs per cm². There are several areas in this coat:the stem is what is visible on the outside and the root is what is buried obliquely in the skin, in the epidermis. The upper is made up of 3 zones:the marrow or medulla which is in the center is the axis.