Blood Vessels and Nervous Apparatus of the Skin: Necessary Knowledge for a Permanent Maker

In the previous article, we talked about the structure of the skin, analyzing each of the layers in detail. In this article we will consider the circulatory and nervous system.

Blood vessels

Arteries, having entered the dermis from a wide-loop fascial network, branching and anastomosing, form a deep (subdermal) and superficial (on the border between the epidermis and dermis) parallel networks. From the first depart terminal arterioles, going to the skin papillae (one for several papillae). In the papilla there is a capillary in the form of a lady's hairpin, rising to the top of the papilla with an arterial knee and passing into a thicker venous knee. From the capillary loops, blood flows into the venules, which form a superficial fine-loop network just below the papillae. A little deeper is the second subpapillary network of venules, parallel to the first. The third venous network is located in the reticular layer of the dermis. In the hypodermis there is a large-mesh deep venous network. It lies parallel to the deep arterial plexus, with which it is connected by many arterio-venular anastomoses, which play an important role in the regulation of blood flow, thermoregulation, sweating, etc. There are two horizontal networks of lymphatic vessels in the dermis: superficial and deep. Blind outgrowths (papillary sinuses) extend from the superficial network into the papillae of the dermis. From the deep network, lymphatic vessels originate, which, gradually becoming larger and anastomosing with each other, form plexuses at the border with subcutaneous fatty tissue.

Nervous apparatus of the skin

The nervous apparatus of the skin is a large receptor field. Sensitive (afferent) nerve fibers come from skin receptors, are part of the cranial and spinal nerves. Perceiving irritations from the external environment, they are divided into mechano-, chemo-, thermo- and nocireceptors (pain). There are free (branched) and encapsulated skin receptors. Free nerve endings are the most functionally important; they are represented in all parts of the dermis by short and long branches, accompanied by Schwann cells. The source of free nerve endings are unmyelinated nerve fibers. Most of these fibers are tactile Merkel cells. Unmyelinated nerve endings in the papillary dermis perceive sensations of pain, itching, and temperature. Encapsulated nerve endings, consisting of an inner bulb and a capsule surrounding it, perform specific functions. So, Krause flasks, which are mechanoreceptors, are found in the subpapillary zone of the dermis of the hands and shoulders. forearms, feet and legs; lamellar bodies of Vater-Pacini - in the smooth skin of mainly fingers, nipples of the mammary glands; tactile bodies of Meissner - in the skin of the palms, especially fingers, lips, eyelids, genitals, in the nipples of the mammary glands, in the papillae of the tongue. Numerous autonomic nerve fibers enter the skin, innervating blood vessels, smooth muscles and glands. Moreover, pulpy and non-fleshy, sensitive and autonomic nerve fibers can be in the same trunk. Large nerve trunks entering the dermis from the subcutaneous fatty tissue form a deep nerve plexus at the border with the subcutaneous fatty tissue and a superficial nerve plexus in the lower part of the papillary dermis. From here, individual nerve fibers and their small bundles are sent to the papillae of the dermis, blood vessels, skin appendages and the epidermis. Approaching the epidermis, thin nerve fibers lose their myelin sheath and penetrate into the intercellular tubules of the basal and spinous layers in the form of bare axial cylinders. Myelinated (pulp) nerve fibers (axons) are 5 times more common than unmyelinated (pulpless).