integumentary system

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HUMAN ANATOMY THE INTEGUMENTARY SYSTEM:

HUMAN ANATOMY THE INTEGUMENTARY SYSTEM

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INTEGUMENTARY is comes from the Latin word integumentum , meaning “ cove r” or “ enclosure”. In animals and plants, an integument is any natural outer covering such as skin, shell, membrane, or husk. The human integumentary system is an external body covering, but also much more. It protects, nourishes, insulates, and cushions. It is absolutely essential to life. Without it, an individual would be attacked immediately by bacteria and die from heat and water loss. The integumentary system is composed primarily of the skin and accessory structures. Those structures include hair, nails, and certain exocrine glands (glands that have ducts or tubes that carry their secretions to the surface of the skin or into body cavities for elimination)

The skin or integument is the largest organ in the body in terms of surface area, covers about two square meters or 2.2 square feet of the adult human body. It is also the heaviest, with an average weight of 4.5-5.0 kg or 10-11 lbs, and account for approximately seven percent of our body weight. It has an average thickness of 1.5 mm, thickest in areas exposed to wear and abrasion (palms and soles) , and is thinnest on the eyelids, external genitalia, and ear drum.:

The skin or integument is the largest organ in the body in terms of surface area, covers about two square meters or 2.2 square feet of the adult human body. It is also the heaviest, with an average weight of 4.5-5.0 kg or 10-11 lbs, and account for approximately seven percent of our body weight. It has an average thickness of 1.5 mm, thickest in areas exposed to wear and abrasion (palms and soles) , and is thinnest on the eyelids, external genitalia, and ear drum.

Together with its accessory organs such as hair, nail, sebaceous and sweat glands, the skin performs the following functions: 1. Protects the body by acting as barriers to microorganisms, water and excessive sunlight; 2. Protects it against dehydration (dessication) and water absorption); 3. Regulates body temperature through heat loss from dilated vessels, evaporation from perspiration, and retention from constricted vessels; 4. Serves for cutaneous sensation by its sensory receptors that respond to heat, cold, pressure, vibration and pain; 5. Performs metabolic function as in the synthesis of melanin, keratin and vitamin D; 6. Contains organs like the sweat glands responsible for the excretion of nitrogenous wastes ; and 7. Acts as blood reservoir. :

Together with its accessory organs such as hair, nail, sebaceous and sweat glands, the skin performs the following functions: 1. Protects the body by acting as barriers to microorganisms, water and excessive sunlight; 2. Protects it against dehydration (dessication) and water absorption); 3. Regulates body temperature through heat loss from dilated vessels, evaporation from perspiration, and retention from constricted vessels; 4. Serves for cutaneous sensation by its sensory receptors that respond to heat, cold, pressure, vibration and pain; 5. Performs metabolic function as in the synthesis of melanin, keratin and vitamin D; 6. Contains organs like the sweat glands responsible for the excretion of nitrogenous wastes ; and 7. Acts as blood reservoir.

SKIN LAYERS:

SKIN LAYERS

EPIDERMIS :

EPIDERMIS The epidermis or surface skin is the outer protective layer of the skin. It is between 30-50 cell layers thick. Epidermal cells are closely packed and highly mitotic. Four types of cells are present in the epidermis: keratinocytes produce keratin – waterproof materials; melanocytes , melanin-pigmentation; Langerhans cells , machrophages -garbage patrol; and Merkel cells, photoreceptors. The epidermis is composed of five layers: Stratum corneum, Stratum lucidum, Stratum granulosum, Stratum spinosum and stratum basale. A thick layer skin consists of five layers while a thin skin has only four. Only the stratum lucidum is not found in thin skin.

EPIDERMIAL LAYER:

EPIDERMIAL LAYER

THICK AND THIN SKIN:

THICK AND THIN SKIN

DERMIS:

DERMIS The dermis is composed of elastic and collagenous fibers which function for stretch and strength, respectively. It also contains sweat glands, sebaceous glands, nerve endings, and hair follicles, and is composed of two layers: the papillary layer is composed of loose connective tissues with lots of blood vessels. It also contains papillae , fingerlike projections which bring blood vessels near the epidermis and help hold the two layers together. It determines fingerprints. The reticular layer is deeper and thicker than the papillary layer and is composed of dense and stretchable connective tissues.

DERMIS LAYER:

DERMIS LAYER

SUBCUTANEOUS LAYER :

SUBCUTANEOUS LAYER The hypodermis , also called the hypoderm , subcutaneous tissue , or superficial fascia is the lowermost layer of the integumentary system in vertebrates . ( Hypoderm and subcutaneous are from Greek and Latin words, respectively, for "beneath the skin." [1] )Types of cells that are found in the hypodermis are fibroblasts , adipose cells , and macrophages . It is derived from the mesoderm , but unlike the dermis , it is not derived from the dermatome region of the mesoderm. In arthropods, the hypodermis is an epidermal layer of cells that secretes the chitinous cuticle . The term also refers to a layer of cells lying immediately below the epidermis of plants. The hypodermis is actually not a part of the skin but connects the dermis to the other organs. This cell is also used to supervise the outer skin from burns and other such articulates. The hypodermis is used mainly for fat storage. A layer of tissue lies immediately below the dermis of vertebrate skin. It is often referred to as subcutaneous tissue though this is a less precise and anatomically inaccurate term. The hypodermis consists primarily of loose connective tissue and lobules of fat. It contains larger blood vessels and nerves than those found in the dermis.

Accessory Organs of the Skin :

Accessory Organs of the Skin

HAIR:

HAIR Hair is found everywhere in the body except in the palms, soles, lips, penis, and other parts of the female genitalia. There is a dense distribution of hair in the scalp, face, public area, and underarms, while a fair distribution is noticeable in other body areas. Primarily, they function for protection: from injury, sunlight and heat loss (the scalp hair’s function); from foreign particles (eyebrows and eyelashes); and from other airborne particles (hairs in the nostrils). A secondary function of the hair is as a sexual attractant. The hair is composed of the shaft, root, and bulb. The shaft is the dead portion of the hair that projects from the surface. The shaft of the hair determines the curliness of the hair: round shaft (straight hair), oval shaft of the hair determines the curliness of the hair: round shaft (straight hair), oval shaft (wavy hair), and flat shaft (kinky hair). The root, which is the terminal end of the hair shaft, is embedded in the skin. The bulb is the enlarged base of the follicle. The root is encased in an internal or epithelial root sheath, and an external or connective root sheath. It contains erector pili muscles whose contraction in hair mammals raises the hair and increases thickness of its coats.

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Like the skin, hair contains melanocytes which produce melanin. There are two types of hair found on humans: vellus hair - is the fine body hair of children and adult women; and terminal hair is the coarser hair of the scalp, eyebrows, etc. Hair on scalp protects the scalp from potentially harmful effects of solar radiation (i.e. sun damage). Eyebrows and eyelashes protect the eyes from small particles e.g. fine grains of sand or smoke - not total protection. Hair in the nostrils protects against inhalation of small particles such as dust, dirt, or even small insects .

GLANDS:

GLANDS Skin glands are referred to as exocrine glands because their secretions are released to the outside through the ducts. The skin glands include the sebaceous glands, sweat glands and ceruminous glands. Sebaceous glands are branched glands attached to the hair follicles . Sweat (sudoriferous) glands are coiled tubular glands which excrete perspiration or sweat onto the surface of the skin. Ceruminous glands or ear wax glands are found in the external auditory canal.

NAILS:

NAILS Nails are composed of hard plates of highly keratinized cells and are formed from the stratum corneum of the epidermis Aside from covering and protecting the dorsal surface of the fingernails and toenails, they also help in grasping and picking small objects. A nail has three parts: a body, free edge and a root. The nail body is the visible portion of the nail. It rests on a nail bed which is actually the stratum spinosum of the dermis. The free edge is also visible and that it extends over a thickened region of the stratum corneum. It is the portion which can be clipped every time. The root is attached to the based and embedded in the nail fold. It is covered by the eponychium or cuticle, which frequently splits, causing a hangnail. The nail matrix is a thick layer composed of stratum basale and lunula. The germinative layer is responsible for the proliferation of cells, making the nail matrix the site of nail growth. The lunula is a white crescent seen near the root of the nail, reflecting the presence of a thick matrix beneath.

THE FUNCTIONS IN SKIN:

THE FUNCTIONS IN SKIN Physical barrier. The skin provides a physical barrier between the internal and external environment. Protection. The skin forms a major part of the body’s external defense mechanisms against infection at harsh chemicals. The skin protects against fluid floss and ultra violet radiation. Sensation. The skin contains receptors for touch, pain, temperature, pressure and the vibration. Excretion. Waste products are excreted through the sweat glands in the skin. Water and sodium are the most obvious examples but other substances can be excreted if their normal excretory pathway fails. Body Shape. The skin contributes to the shape of the body as does the skeleton, the muscular system and adipose tissues.

SKIN COLOR:

SKIN COLOR Melanin. It can be found in shades of yellow, brown, and black. The melanocytes make the melanin, which is picked up by the keratinocytes via phagocytosis. Melanin is important because it protects the DNA in the nucleus from UV radiation. The amount and color of melanin is hereditary. All humans have roughly the same number of melanocytes, but some people’s melanocytes are “busier” than others. Carotene. It is a yellow-orange pigment that accumulates in the stratum corneum and in the adipose tissue found in the hypodermis. Hemoglobin. It is the oxygen-carrying protein found in our red blood cells. A pink color of a fair skin is due to oxygenated hemoglobin of the blood in underlying blood vessels. If the blood is not adequately oxygenated, the hemoglobin will be blue in color, and so the skin might also have a blue cast.

COURSE REQUIREMENT IN BIOLOGY:

COURSE REQUIREMENT IN BIOLOGY REFERENCES http://www.nahanniriverherbs.com http://www.buzzle.com Basic Concepts in Biology (BOOK) CREATED BY: Daisy Alcantara Gabriel John Coronado 1S BSED

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