Otázka: Integumentary system
The integumentary system is an organ system consisting of the skin, hair, nails, and exocrine glands. The skin is only a few millimetres thick yet is by far the largest organ in the body. The average person’s skin weighs 10 pounds and has a surface area of almost 20 square feet. Skin forms the body’s outer covering and forms a barrier to protect the body from chemicals, disease, UV light, and physical damage. Hair and nails extend from the skin to reinforce the skin and protect it from environmental damage. The exocrine glands of the integumentary system produce sweat, oil, and wax to cool, protect, and moisturize the skin’s surface.
The epidermis has several strata (layers) that contain four cell types. Keratinocytes produce keratin, a protein that gives skin its strength and flexibility and waterproofs the skin surface. Melanocytes produce melanin, the dark pigment that gives skin its colour. Merkel’s cells are probably involved with touch reception. Langerhans’ cells help the immune system by processing antigens. The epidermis is an avascular region of the body, meaning that it does not contain any blood or blood vessels. The cells of the epidermis receive all of their nutrients via diffusion of fluids from the dermis.
The dermis is the deep layer of the skin found under the epidermis. The dermis is mostly made of dense irregular connective tissue along with nervous tissue, blood, and blood vessels. The dermis is much thicker than the epidermis and gives the skin its strength and elasticity. Within the dermis there are two distinct regions: the papillary layer and the reticular layer.
The papillary layer contains many finger-like extensions called dermal papillae that protrude superficially towards the epidermis.
The reticular layer is made of dense irregular connective tissue that contains many tough collagen and stretchy elastic fibres running in all directions to provide strength and elasticity to the skin. The reticular layer also contains blood vessels to support the skin cells and nerve tissue to sense pressure and pain in the skin.
Deep to the dermis is a layer of loose connective tissues known as the hypodermis, sub cutis, or subcutaneous tissue. The hypodermis serves as the flexible connection between the skin and the underlying muscles and bones as well as a fat storage area. Fatty adipose tissue in the hypodermis stores energy in the form of triglycerides. Adipose also helps to insulate the body by trapping body heat produced by the underlying muscles.
Hair is an accessory organ of the skin made of columns of tightly packed dead keratinocytes found in most regions of the body. The few hairless parts of the body include the palmer surface of the hands, plantar surface of the feet, lips, labia minora, and gland penis. Hair helps to protect the body from UV radiation by preventing sunlight from striking the skin. Hair also insulates the body by trapping warm air around the skin.
The structure of hair can be broken down into 3 major parts: the follicle, root, and shaft.
Nails are accessory organs of the skin made of sheets of hardened keratinocytes and found on the distal ends of the fingers and toes. There are 3 main parts of a nail: the root, body, and free edge.
Nails grow from a deep layer of epidermal tissue known as the nail matrix, which surrounds the nail root.
Sudoriferous glands are exocrine glands found in the dermis of the skin and commonly known as sweat glands. There are 2 major types of sudoriferous glands: eccrine sweat glands and apocrine sweat glands. Eccrine sweat glands are found in almost every region of the skin and produce a secretion of water and sodium chloride.
Apocrine sweat glands are found in mainly in the axillary and pubic regions of the body.
Sebaceous glands are exocrine glands found in the dermis of the skin that produce an oily secretion known as sebum. Sebaceous glands are found in every part of the skin except for the thick skin of the palms of the hands and soles of the feet. Sebum is produced in the sebaceous glands and carried through ducts to the surface of the skin or to hair follicles. Sebum acts to waterproof and increase the elasticity of the skin.
Ceruminous glands are special exocrine glands found only in the dermis of the ear canals. Ceruminous glands produce a waxy secretion known as cerumen to protect the ear canals and lubricate the eardrum. Cerumen protects the ears by trapping foreign material such as dust and airborne pathogens that enter the ear canal.
The amazing facts about skin
- Your skin drops up to 30,000 to 40,000 dead skin cells each minute of the daytime. That’s up to 4kg of skin for every year!
- We “shed” our skin and replace it with a new one every 2-4 weeks!
- On a hot day, the skin sometimes releases as much as 3 gallons of sweat!
- The skin’s thinnest area on the human body is on the eyelids.
- Contains a pigment called Melanin. The more melanin the darker the skin, less makes it lighter.
- The skin is the body’s largest organ.
- A square inch of the human body has approximately 19,000,000 skin cells.and up to 300 sweat glands.