Dermis and Epidermis - Function of Dermis

Dermis is profusely supplied with blood vessels. Dermis is divided into papillary and reticular dermis. It contains connective tissue fibres. cells and all dermal appendages. Connective tissue is formed by three main components

(1) collagen fibres

(2) elastic fibres

(3) ground substance.

The most abundant dermal constituent is collagen. All these are produced by master cell fibroblast. There are at least 13 known type of connective tissue collagen of which seven are detected in human skin. Type I collagen accounts for 80% of total collagen in skin and Type III makes up another 15% of total collagen.

Collagen is a protein and constitutes about 70% of dry weight of dermis.

A single collagen bundle 1.0 mm in diameter can sustain a load of 10 to 40 kg without breaking. Collagen molecule is termed as "tropocollagen". It consists of three polypeptide chains. Each chain consists of hydroxyproline, hydroxylysine and glycine.

Elastic fibres are smaller and offer extensibility to the skin.. In the papillary dermis, the fibres are vertically oriented. Its deeper parts merge imperceptibly into the hypodermis.

Beneath the basement membrane are'distributed many blood vessels forming a capillary network which sends up loops into the dermal papillae. These papillae are microscopic finger-like processes projecting into - the epidermis, which is moulded over and attached to them.

The connective tissue cells in the dermis are spindle-shaped and are more numerous in the superficial layers than in the deeper ones. Thickness of dermis is I to 3 mm.

In a microscopic section passing through the dermis, besides the structures mentioned above, are also seen hair follicles, various types of sebaceous and sweat glands, plain muscle fibres, sensory end-organs like Pacinian and Meissner's corpuscles and adipose tissue; the latter is present mostly in the deeper parts. There are a few round cells, an occasional fibrocyte and a few pigment-carrying histiocytes called melanophores.

Within the skin, the blood supply and drainage lie along well-determined pathways. There are rich capillary beds in the papillae and around the appendages and in sub-papillary plexus; deep reticular plexus is much less rich. In the deeper layer of the dermis, there is arterio-venous anastomosis surrounded by sphincter-like group of smooth muscles under autonomic control.

Skin is richly innervated by myelinated and non-myelinated sensory fibres and via non-myelinated autonomic fibres supplying blood vessels and appendages. Conspicuous nerve supply consists of plexuses in the papillae, Meissner's corpuscles, Pacinian corpuscles, Merkel's discs and nerve endings in the basal layer of the epidermis.

In addition to superficial and deep plexuses of rich vascular supply, arteriovenous anastomosesare present in the skin. These specialized segments are known as Sucquet-Hoyercanal. They are surrounded by ovoid-shaped smooth cells known as glomus cells. They are under the control of sympathetic nervous system.

A small nerve is associated with every glomus, and they respond to variety of pharmacologic agents and cause vasoconstriction. Thermoregulation is an important function of the skin vasculature.

Structure of Epidermis
Structure of Dermis
Sebaceous Glands
Sweat Glands

Caring for the Skin

• Hormones and their Effect on the Skin
• Caring for the Skin by Electric Therapy
• Light therapy
• Quick Home Facial
• Skin Care by Reflex therapy
• Skin Surgery
• Baby's Skin Care
• Oils and Your Skin

Healthy Skin