The knowledge of the physiological structure of the cat's skin, what little secrets are hidden in the cat's body? There are many different types of cat skin diseases, and they will also show different symptoms, so skin diseases In the final analysis, it is a disease whose symptoms appear on the skin. When diagnosing skin diseases, we should first have a preliminary understanding of the cat's skin structure, and understand which layers the skin is divided into and what are the different physiological structures. What is the function of each part, which is not only conducive to the judgment of skin diseases, but also helpful to the treatment and medication.

I. Epidermis

Epidermal formation The outermost layer of the skin plays a role in isolating the harsh external environment and protecting the body from various chemical, physical and biological factors. Although the epidermis is thin, it has a strong protective effect on the body with the help of the coat, keratinocytes and glands. The epidermis and the dermis are closely combined, exchange cells and body fluids, and can obtain sufficient nutrient supply. The epidermis is composed of stratified squamous (flat) epithelium, which is only 0.2-0.5 mm thick. The thickest epidermis is distributed on the nose and footpads (1.5mm). The epidermis is composed of keratinocytes, pigment cells, Langerial cells, etc. Keratinocytes account for 85% of epidermal cells, and the morphology of each layer in the epidermis is slightly different. In the basal layer, it appears as a tightly connected columnar epithelium, which is connected with the basement membrane area. With the cell division, the daughter cells enter the spinous layer, and the morphology is polyhedral, and the granular layer is flat. The stratum corneum appears as a flattened shape with disappearing nuclei. Keratinocytes are both an important structural component of the skin and an important member of the skin's immune system. They are even more effective at engulfing and processing antigens than specialized immune cells in the epidermis, Langer cells. Under the influence of γ-interferon, keratinocytes stimulate and buffer T lymphocytes. After interacting with the antigen, they make interleukin-1, which further stimulates the production of a wider range of cytokines, which stimulate and suppress immune responses. Interleukin-1 can also be released into the dermis to cause an inflammatory response.

Second, dermis-epidermal junction - basement membrane

The basement membrane is the basis of the epidermis, through which the epidermis is firmly fixed on the dermis, maintains the normal function and proliferation of the epidermis, maintains tissue structure, helps wound healing, and is also the barrier between the dermis and the epidermis, maintaining the role of the epidermis and dermis to exchange cells and humoral elements .

The basement membrane is composed of four parts:

(1) Tension filament - hemidesmosome Complex (attached to the basal layer cells);

(2) The main component of the transparent plate is collagen XVII (ie 180kDa bullous pemphigoid antigen, BP180) and fixed fibers;

(3) The dense plate contains collagen IV, laminin isoform, nestin and basement membrane proteoglycan, etc.;

(4) Under the basement membrane: the extension of the fixed fibers and acid-resistant filaments formed by the dense thin layer to the superficial dermis. In very rare bullous pemphigoid, the main target of autoantibody attack is collagen XVII (BP180).   

Third, the dermis

Yes The main part of the skin, which is firm, flexible and elastic in texture. The dermis provides physical, blood and neurological support to the epidermis and is the complete connective tissue of the body. The dermis is mainly composed of dermal fibers and soluble aggregates, with cells interspersed therein. The majority of the appendages in the skin are located within the dermis.

(1) Dermal fibers: collagen and elastin.

(2) Soluble polymer: proteoglycan and hyaluronan.

(3) Intradermal cells: fibroblasts and dendritic cells.

(4) Accessory structures: hair follicle unit, erector muscle, blood vessels, lymphatic vessels and nerves. Intradermal lesions frequently occur in and around blood vessels. The lesions of other dermal components are very rare, such as: skin lesions caused by abnormal collagen structure - Elliott-Danner's disease (also known as: systemic fibroelastosis syndrome), is a hereditary poor synthesis and distribution of collagen Abnormal, mainly manifested as hyperextension of the skin.