There are many different types of cat skin diseases, which will also show different symptoms. In the final analysis, skin diseases are diseases whose symptoms are manifested on the skin. When making a diagnosis of skin diseases, we should first diagnose the cat A preliminary understanding of the skin structure, including what layers the skin is divided into, what different physiological structures it has, and what the functions of each part are. This is not only helpful for the judgment of skin diseases, but also helpful for treatment and medication.

1. Epidermal layer

The epidermis forms the outermost layer of the skin, which serves to isolate the harsh external environment and protect the body from various chemical, physical and biological factors. Although the epidermis is very thin, it has a strong protective effect on the body with the help of hair, keratinocytes and glands. The epidermis and dermis are closely combined, exchanging cells and body fluids to obtain adequate nutrient supply. The epidermis is composed of stratified squamous (flat) epithelium, and its thickness is only 0.2-0.5mm. The thickest epidermis is found on the nose and foot pads (1.5mm). The epidermis is composed of keratinocytes, pigment cells, Langerhans cells, etc. Keratinocytes account for 85% of epidermal cells, and the shapes of each layer in the epidermis are slightly different. The basal layer shows a tightly connected columnar epithelium, which is connected to the basement membrane area. As the cells divide, the daughter cells enter the spinous layer, which is polyhedral in shape, and the granular layer is flat.

The stratum corneum appears as a flat shape with missing cell nuclei. Keratinocytes are both an important structural component of the skin and an important member of the skin's immune system. Their ability to phagocytose and process antigens is even higher than that of Langerhans cells, the specialized immune cells in the epidermis. Under the influence of gamma-interferon, keratinocytes have a stimulating and buffering effect on T lymphocytes. After interacting with the antigen, they produce interleukin-1, which further stimulates the production of broader cytokines that stimulate and suppress immune responses. Interleukin-1 can also be released into the dermis to cause an inflammatory response.

2. Dermo-epidermal junction - basement membrane

The basement membrane is the foundation of the epidermis. The epidermis is firmly fixed to the dermis through it, maintaining the normal function and proliferation of the epidermis, maintaining tissue structure, and helping wound healing. It is also a barrier between the dermis and epidermis, maintaining the exchange of cells and body fluids between the epidermis and dermis. The role of elements.

The basement membrane consists of four parts:

　(1) Tension filaments-hemidesmosome complex (attached to basal layer cells);

　(2) The main components of the transparent plate are collagen XVII (i.e. 180kDa bullous pemphigoid antigen, BP180) and fixed fibers;

　(3) The dense plate contains type IV collagen, laminin isoforms, nestin, and basement membrane proteoglycans;

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

3. Dermis layer

It is the main part of the skin, with a strong, pliable and elastic 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 dispersed in it. Most of the accessory structures in the skin are located within the dermis.

(1) Dermal fibers: collagen and elastin.

(2) Soluble polymers: proteoglycans and hyaluronan.

(3) Cells in the dermis: fibroblasts and dendritic cells.

(4) Accessory structures: follicular units, arrector pili muscles, blood vessels, lymphatic vessels and nerves. Intradermal lesions frequently occur intravascularly and perivascularly. Other dermal component lesions are very rare, such as: skin lesions caused by abnormalities in collagen structure - Ehlers-Denbach disease (also known as: systemic elastic fiber dysplasia syndrome), which is an inherited disorder of collagen synthesis and distribution. Abnormality, mainly manifested as excessive stretching of the skin.