Integumentary System (cueto).pdf

Integumentary System By : Marc Anthony Cueto MD Learning Objectives 1. Identify the layers of the integumentary system from the most superficial layer to the deepest layer. 2. Recognize the different types and parts of the skin appendages. 3. Classify the modes of secret...

Integumentary System By : Marc Anthony Cueto MD Learning Objectives 1. Identify the layers of the integumentary system from the most superficial layer to the deepest layer. 2. Recognize the different types and parts of the skin appendages. 3. Classify the modes of secretion of the different cutaneous glands and locate their areas. Integumentary System  Derivedfrom the latin word “INTEGUMENTUM” which means “a covering”.  Integument is the natural covering of an organism or an organ, such as its skin, husk, shell, or rind.  Skin  Skin is the largest organ of the human body (20 square feet)  The skin is divided into two parts: the superficial part, the epidermis, and the deep part, the dermis Epidermis  The epidermis is a stratified epithelium with cells that flatten as they mature and rise to the surface.  On the palms of the hands and the soles of the feet, the epidermis is extremely thick to withstand the wear and tear that occurs in these regions.  In other areas of the body, such as on the anterior surface of the arm and forearm, it is thin. Epidermis : The Basal Cell Layer  The basal layer is the innermost layer of the epidermis, and contains small round cells called basal cells.  The basal cells continually divide, and new cells constantly push older ones up toward the surface of the skin, where they are eventually shed.  The basal cell layer is also known as the stratum germinativum due to the fact that it is constantly germinating (producing) new cells.  The basal cell layer contains cells called melanocytes. Epidermis : The Basal Cell Layer  Melanocytes produce the skin coloring or pigment known as melanin, which gives skin its tan or brown color and helps protect the deeper layers of the skin from the harmful effects of the sun.  Sun exposure causes melanocytes to increase production of melanin in order to protect the skin from damaging ultraviolet rays, producing a suntan. Patches of melanin in the skin cause birthmarks, freckles and age spots.  Melanoma develops when melanocytes undergo malignant transformation.  Merkel cells, which are tactile cells of neuroectodermal origin, are also located in the basal layer of the epidermis. They function as touch receptors. Epidermis : The Squamous Cell Layer  The squamous cell layer is located above the basal layer, and is also known as the stratum spinosum or "spiny layer" due to the fact that the cells are held together with spiny projections.  Within this layer are the basal cells that have been pushed upward, however these maturing cells are now called squamous cells, or keratinocytes.  Keratinocytes produce keratin, a tough, protective protein that makes up the majority of the structure of the skin, hair, and nails.  The squamous cell layer is the thickest layer of the epidermis, and is involved in the transfer of certain substances in and out of the body.  The squamous cell layer also contains cells called Langerhans cells. These cells attach themselves to antigens that invade damaged skin and alert the immune system to their presence. Epidermis : The Stratum Granulosum & the Stratum Lucidum  The keratinocytes from the squamous layer are then pushed up through two thin epidermal layers called the stratum granulosum and the stratum lucidum.  As these cells move further towards the surface of the skin, they get bigger and flatter and adhere together, and then eventually become dehydrated and die.  This process results in the cells fusing together into layers of tough, durable material, which continue to migrate up to the surface of the skin. Epidermis : The Stratum Corneum  The stratum corneum is the outermost layer of the epidermis, and is made up of 10 to 30 thin layers of continually shedding, dead keratinocytes.  The stratum corneum is also known as the "horny layer," because its cells are toughened like an animal's horn. As the outermost cells age and wear down, they are replaced by new layers of strong, long-wearing cells.  The stratum corneum is sloughed off continually as new cells take its place, but this shedding process slows down with age.  Complete cell turnover occurs every 28 to 30 days in young adults, while the same process takes 45 to 50 days in elderly adults. Epidermis : Layers Dermis  The Dermis beneath the epidermis is a connective tissue layer, the dermis.  It is composed mainly of collagen, but also contains elastic and reticular fibers, fibroblasts, and the other cells typical of fibrous connective tissue.  It is well supplied with blood vessels, sweat glands, sebaceous glands, and nerve endings. Dermis : The Papillary Layer  The upper, papillary layer, contains a thin arrangement of collagen fibers.  The papillary layer supplies nutrients to select layers of the epidermis and regulates temperature. Both of these functions are accomplished with a thin, extensive vascular system that operates similarly to other vascular systems in the body.  Constriction and expansion control the amount of blood that flows through the skin and dictate whether body heat is dispelled when the skin is hot or conserved when it is cold. Dermis : The Reticular Layer  The lower, reticular layer, is thicker and made of thick collagen fibers that are arranged in parallel to the surface of the skin.  The reticular layer is denser than the papillary dermis, and it strengthens the skin, providing structure and elasticity.  It also supports other components of the skin, such as hair follicles, sweat glands, and sebaceous glands. Hypodermis  The subcutis is the innermost layer of the skin, and consists of a network of fat and collagen cells.  The subcutis is also known as the hypodermis or subcutaneous layer, and functions as both an insulator, conserving the body's heat, and as a shock-absorber, protecting the inner organs.  It also stores fat as an energy reserve for the body.  The blood vessels, nerves, lymph vessels, and hair follicles also cross through this layer. The thickness of the subcutis layer varies throughout the body and from person to person.  Drugs are introduced into the hypodermis by injection because the subcutaneous tissue is highly vascular and absorbs them quickly. Accessory Organs of the Skin Accessory Organs of the Skin  The hair, nails, and cutaneous glands are the accessory organs (appendages) of the skin.  Hair and nails are composed mostly of dead, keratinized cells. The stratum corneum of the skin is made of pliable soft keratin, but the hair and nails are composed mostly of hard keratin.  Hard keratin is more compact than soft keratin and is toughened by numerous cross-linkages between the keratin molecules. Hair  A hair is also known as a pilus; in the plural, pili.  It is a slender filament of keratinized cells that grows from an oblique tube in the skin called a hair follicle. Hair : Hair follicle  A hair follicle is a tube-like structure (pore) that surrounds the root and strand of a hair.  Hair follicles exist in the top two layers of your skin.  You’re born with over 5 million hair follicles in your body and over one million hair follicles on your head.  As you age, hair grows out of your hair follicles.  Your hair follicle is one of a few structures in your body that can stop functioning and begin functioning again (degenerate and regenerate). This process helps with hair growth on your body. Hair : Hair follicle  The hair follicle can be divided into 3 regions: the lower segment (bulb and suprabulb), the middle segment (isthmus), and the upper segment (infundibulum).  The lower segment extends from the base of the follicle to the insertion of the erector pili muscle (also known as the arrector pili muscle).  The middle segment is a short section that extends from the insertion of the erector pili muscle to the entrance of the sebaceous gland duct.  The upper segment extends from the entrance of the sebaceous gland duct to the follicular orifice. Hair follicle : Function  The function of a hair follicle is to grow your hair. In addition to promoting hair growth, your hair follicles do the following jobs:  Help repair your skin after a wound or an injury.  Form new blood vessels (angiogenesis).  Form new nervous system neuron cells (neurogenesis). How does hair grow out of a hair follicle? What are the common conditions that affect hair follicles?  Several conditions affect the health of your hair follicles. The most common conditions include:  Alopecia areata.  Baldness in women and people assigned female and male at birth.  Folliculitis.  Hidradenitis suppurativa.  Stress.  Telogen effluvium.  Whiteheads, blackheads or a dilated pore of Winer. Folliculitis  Folliculitis is a common skin condition that happens when hair follicles become inflamed.  It's often caused by an infection with bacteria. At first it may look like small pimples around the tiny pockets from where each hair grows (hair follicles).  The condition can be itchy, sore and embarrassing. The infection can spread and turn into crusty sores.  Mild folliculitis will likely heal without scarring in a few days with basic self-care.  More-serious or repeat infections may need prescription medicine. Left untreated, severe infections can cause permanent hair loss and scarring. Alopecia Areata  Alopecia areata is a disease that happens when the immune system attacks hair follicles and causes hair loss.  While hair can be lost from any part of the body, alopecia areata usually affects the head and face.  Hair typically falls out in small, round patches about the size of a quarter, but in some cases, hair loss is more extensive.  Most people with the disease are healthy and have no other symptoms.  The course of alopecia areata varies from person to person. Some have bouts of hair loss throughout their lives, while others only have one episode. Recovery is unpredictable too, with hair regrowing fully in some people but not others.  There is no cure for alopecia areata, but there are treatments that help hair grow back more quickly. Telogen Effluvium  Telogen effluvium is a common type of hair loss that affects people after they experience severe stress or a change to their body.  Symptoms include thinning hair, usually around the top of your head.  Telogen effluvium affects your hair when it’s in the telogen stage. After a stressor or change to your body, up to 70% of your hair in the anagen stage prematurely enters the telogen phase, which causes hair loss.  Treatment exists to reverse hair loss, but hair will typically grow back in three to six months without treatment. Hidradenitis Suppurativa  Hidradenitis suppurativa is a condition that causes small, painful lumps to form under the skin.  The lumps usually develop in areas where your skin rubs together, such as the armpits, groin, buttocks and breasts.  The lumps heal slowly, recur, and can lead to tunnels under the skin and scarring.  Hidradenitis suppurativa tends to start after puberty.  It can persist for many years and worsen over time, with serious effects on your daily life and emotional well-being.  Combined medical and surgical therapy can help manage the disease and prevent complications. Nails  The nail unit is a complex structure located on the dorsal surface of the fingers and toes.  Nails are homologous to the stratum corneum of the epidermis and contain a variety of minerals, such as calcium.  They consist of compacted and layered keratin- filled squames (scales).  The arrangement and cohesion of the squames are responsible for the hardness of nails.  It has two main functions:  Protection – protects the digits from trauma  Sensation – assists with tactile sensation Components of the Nail Unit  Nail plate – outer portion of the nail unit, formed by layers of keratin. It forms a hard, yet flexible, translucent plate.  Nail folds – skin that surrounds and protects the proximal and lateral margins of the nail plate  Nail bed (sterile matrix) – lies underneath the nail plate, attaching it to the distal phalanx. The nail bed provides a smooth surface for the growing nail plate to slide over (it does not contribute to plate growth itself). Components of the Nail Unit  Germinal matrix – area of soft tissue proximal to the sterile matrix. Cells within the germinal matrix divide and become keratinised to form the nail plate. Continuous cell division within the matrix ‘pushes’ the nail plate over the bed as it matures.  Hyponychium – the area distal to the nail bed, situated underneath the free edge of the nail plate.  Eponychium (cuticle) – layer of stratum corneum which extends between the skin of the finger and proximal nail plate.  Lunula – white ‘half-moon’ appearance of the germinal matrix through the proximal nail plate. Ingrown Toenail  Ingrown toenail is incurvation or impingement of a nail border into its adjacent nail fold, causing pain.  Causes include tight shoes, abnormal gait (eg, toe-walking), bulbous toe shape, excessive trimming of the nail plate, or congenital variations in nail contour (eg, congenital pincer nail deformity).  Pain occurs at the corner of the nail fold or, less commonly, along its entire lateral margin. Initially only mild discomfort may be present, especially when wearing certain shoes. In chronic cases, granulation tissue becomes visible, more often in the young.  Redness, swelling, and pain suggest paronychia.  Treatment includes nail excision and destruction of adjacent nail matrix. Onychomycosis  Onychomycosis is a fungal infection of the nails that causes discoloration, thickening, and separation from the nail bed.  Onychomycosis occurs in 10% of the general population, 20% of persons older than 60 years, and 50% of those older than 70 years.  It is caused by a variety of organisms, but most cases are caused by dermatophytes.  Accurate diagnosis involves physical and microscopic examination and culture.  Histologic evaluation using periodic acid–Schiff staining increases sensitivity for detecting infection.  Treatment is aimed at eradication of the causative organism and return to a normal appearance of the nail. Sweat Glands  The average person has about 3 million sweat glands. Sweat glands are classified according to two types:  Apocrine glands are specialized sweat glands that can be found only in the armpits and pubic region. These glands secrete a milky sweat that encourages the growth of the bacteria responsible for body odor.  Eccrine glands are the true sweat glands. Found over the entire body, these glands regulate body temperature by bringing water via the pores to the surface of the skin, where it evaporates and reduces skin temperature. These glands can produce up to two liters of sweat an hour, however, they secrete mostly water, which doesn't encourage the growth of odor-producing bacteria. Ceruminous Glands Mammary Glands  The mammary glands and breasts (mammae) are often mistakenly regarded as one and the same.  Breasts, however, are present in both sexes, and even in females they rarely contain more than small traces of mammary gland.  The mammary glands, by contrast, are the milk- producing glands that develop within the female breast only during pregnancy and lactation. Thank you !