Living, your destination for ideas, inspiration and advice for you, your family and your home. This article is about the outer covering of animals. M skin skin in humans, see human skin. Skin is the soft outer tissue covering vertebrates.
Other animal coverings, such as the arthropod exoskeleton, have different developmental origin, structure and chemical composition. Primarily, fur augments the insulation the skin provides but can also serve as a secondary sexual characteristic or as camouflage. At the bottom superficial parts of the dermis. The epidermis is composed of the outermost layers of the skin. The epidermis and dermis are separated by a thin sheet of fibers called the basement membrane, and is made through the action of both tissues. The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The papillary region is composed of loose areolar connective tissue.
This is named for its fingerlike projections called papillae that extend toward the epidermis. The reticular region lies deep in the papillary region and is usually much thicker. Its purpose is to attach the skin to underlying bone and muscle as well as supplying it with blood vessels and nerves. Microorganisms like Staphylococcus epidermidis colonize the skin surface. The density of skin flora depends on region of the skin. The epidermis of fish and of most amphibians consists entirely of live cells, with only minimal quantities of keratin in the cells of the superficial layer.
Sweat glands and sebaceous glands are both unique to mammals, but other types of skin gland are found in other vertebrates. Although melanin is found in the skin of many species, in the reptiles, the amphibians, and fish, the epidermis is often relatively colourless. Both of these glands are part of the integument and thus considered cutaneous. Mucous and granular glands are both divided into three different sections which all connect to structure the gland as a whole. Granular glands can be identified as venomous and often differ in the type of toxin as well as the concentrations of secretions across various orders and species within the amphibians. They are located in clusters differing in concentration depending on amphibian taxa.
The toxins can be fatal to most vertebrates or have no effect against others. Structurally, the ducts of the granular gland initially maintain a cylindrical shape. However, when the ducts become mature and full of toxic fluid, the base of the ducts become swollen due to the pressure from the inside. This causes the epidermal layer to form a pit like opening on the surface of the duct in which the inner fluid will be secreted in an upwards fashion.