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The integumentary system
- 1. The Integumentary System by shadrack Kioko
- 2. The Integumentary System Integument(covering) is skin Skin and its appendages(hair, nails, and exocrine glands) make up the integumentary system A fatty layer (hypodermis) lies deep to it Two distinct regions Epidermis Dermis
- 3. Functions of skin Protection Cushions and insulates and is waterproof Protects from chemicals, heat, cold, bacteria Screens UV Synthesizes vitamin D with UV Regulates body heat Prevents unnecessary water loss Sensory reception (nerve endings) excretion
- 4. Layers of the skin EPIDERMIS DERMIS HYPODERMIS The skin is about 1.5 – 2.0 square meters ~20sq. ft
- 5. Epidermis Keratinized stratified squamous epithelium Four types of cells Keratinocytes – deepest, produce keratin (tough fibrous protein) Melanocytes - make dark skin pigment melanin Merkel cells – associated with sensory nerve endings Langerhans cells – macrophage-like dendritic cells Layers (from deep to superficial) Stratum basale or germinativum – single row of cells attached to dermis; youngest cells Stratum spinosum – spinyness is artifactual; tonofilaments (bundles of protein) resist tension Stratum granulosum – layers of flattened keratinocytes producing keratin (hair and nails made of it also) Stratum lucidum (only on palms and soles) Stratum corneum – horny layer (cells dead, many layers thick) (see figure on next slide)
- 6. Epithelium: layers (on left) and cell types (on right)
- 7. Remember… Four basic types of tissue Epithelium – epidermis just discussed Connective tissue - dermis Muscle tissue Nervous tissue
- 8. Dermis Strong, flexible connective tissue: your “hide” Cells: fibroblasts, macrophages, mast cells, WBCs Fiber types: collagen, elastic, reticular Rich supply of nerves and vessels Critical role in temperature regulation (the vessels) Two layers (see next slides) Papillary – areolar connective tissue; includes dermal papillae Reticular – “reticulum” (network) of collagen and reticular fibers
- 10. Epidermis and dermis of (a) thick skin and (b) thin skin (which one makes the difference?)
- 11. Fingerprints, palmprints, footprints Dermal papillae lie atop dermal ridges Elevate the overlying epidermis into epidermal ridges Are “sweat films” because of sweat pores Genetically determined Flexion creases Deep dermis, from continual folding Fibers Collagen: strength and resilience Elastic fibers: stretch-recoil Striae: stretch marks Tension lines (or lines of cleavage) The direction the bundles of fibers are directed The dermis is the receptive site for the pigment of tattoos
- 12. Hypodermis “Hypodermis” (Gk) = below the skin “Subcutaneous” (Latin) = below the skin Also called “superficial fascia” “fascia” (Latin) =band; in anatomy: sheet of connective tissue Fatty tissue which stores fat and anchors skin (areolar tissue and adipose cells) Different patterns of accumulation (male/female)
- 14. Skin color Three skin pigments Melanin: the most important Carotene: from carrots and yellow vegies Hemoglobin: the pink of light skin Melanin in granules passes from melanocytes (same number in all races) to keratinocytes in stratum basale Digested by lysosomes Variations in color Protection from UV light vs vitamin D?
- 15. Skin appendages Derived from epidermis but extend into dermis Include Hair and hair follicles Sebaceous (oil) glands Sweat (sudoiferous) glands Nails
- 17. Nails Of hard keratin Corresponds to hooves and claws Grows from nail matrix
- 18. Hair and hair follicles: complex Derived from epidermis and dermis Everywhere but palms, soles, nipples, parts of genitalia *“arrector pili” is smooth muscle * Hair papilla is connective tissue________________ Hair bulb: epithelial cells surrounding papilla
- 19. Functions of hair Warmth – less in man than other mammals Sense light touch of the skin Protection - scalp Parts Root imbedded in skin Shaft projecting above skin surface Make up of hair – hard keratin Three concentric layers Medulla (core) Cortex (surrounds medulla) Cuticle (single layers, overlapping)
- 21. Types of hair Vellus: fine, short hairs Intermediate hairs Terminal: longer, courser hair Hair growth: averages 2 mm/week Active: growing Resting phase then shed Hair loss Thinning – age related Male pattern baldness Hair color Amount of melanin for black or brown; distinct form of melanin for red White: decreased melanin and air bubbles in the medulla Genetically determined though influenced by hormones and environment
- 22. Sebaceous (oil) glands Entire body except palms and soles Produce sebum by holocrine secretion Oils and lubricates
- 23. Sweat glands Entire skin surface except nipples and part of external genitalia Prevent overheating 500 cc to 12 l/day! (is mostly water) Humans most efficient (only mammals have) Produced in response to stress as well as heat
- 24. Types of sweat glands Eccrine or merocrine Most numerous True sweat: 99% water, some salts, traces of waste Open through pores Apocrine Axillary, anal and genital areas only Ducts open into hair follices The organic molecules in it decompose with time - odor Modified apocrine glands Ceruminous – secrete earwax Mammary – secrete milk
- 25. Ceruminous Glands special exocrine glands found only in the dermis of the ear canals. Protect ear and lubricate ear drum
- 26. Sensation The body feels pain, heat, and cold because the integumentary system has sensory receptors in all its layers. For example, the epidermis and dermal papillae are well supplied with touch receptors. The dermis and deeper tissues contain pain, heat, cold, touch, and pressure receptors. Hair follicles (but not the hair) are well innervated, and movement of hair can be detected by sensory receptors surrounding the base of hair follicles.
- 27. Disorders of the integumentary system Burns Threat to life Catastrophic loss of body fluids Dehydration and fatal circulatory shock Infection Types First degree – epidermis: redness (e.g. sunburn) Second degree – epidermis and upper dermis: blister Third degree - full thickness Infections Skin cancer Congenital disorders e.g allbinism
- 28. Burns First-degree (epidermis only; redness) Second-degree (epidermis and dermis, with blistering) Third-degree (full thickness, destroying epidermis, dermis, often part of hypodermis)
- 29. Critical burns Over 10% of the body has third- degree burns 25 % of the body has second- degree burns Third-degree burns on face, joints, hands, or feet Estimate by “rule of 9’s”
- 31. Tumors of the skin Benign, e.g. warts Cancer – associated with UV exposure (also skin aging) Aktinic keratosis - premalignant Basal cell - cells of stratum basale Squamous cell - keratinocytes Melanoma – melanocytes: most dangerous; recognition: A - Asymmetry B - Border irregularity C - Colors D - Diameter larger than 6 mm
- 32. Basal cell carcinoma Sqaumous cell carcinoma Melanoma Skin Cancer
- 33. Effects of Aging on the Integumentary System 1. As the body ages, blood flow to the skin declines, the skin becomes thinner, and elasticity is lost. 2. Sweat and sebaceous glands are less active, and the number of melanocytes decreases.
- 34. thankyou
Editor's Notes
- EpidermisThe epidermis is the most superficial layer of the skin that covers almost the entire body surface. The epidermis rests upon and protects the deeper and thicker dermis layer of the skin. Structurally, the epidermis is only about a tenth of a millimeter thick but is made of 40 to 50 rows of stacked squamous epithelial cells. 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 epidermis is made of several specialized types of cells. Almost 90% of the epidermis is made of cells known as keratinocytes. Keratinocytes develop from stem cells at the base of the epidermis and begin to produce and store the protein keratin. Keratin makes the keratinocytes very tough, scaly and water-resistant. At about 8% of epidermal cells, melanocytes form the second most numerous cell type in the epidermis. Melanocytes produce the pigment melanin to protect the skin from ultraviolet radiation and sunburn. Langerhans cells are the third most common cells in the epidermis and make up just over 1% of all epidermal cells. Langerhans cells’ role is to detect and fight pathogens that attempt to enter the body through the skin. Finally, Merkel cells make up less than 1% of all epidermal cells but have the important function of sensing touch. Merkel cells form a disk along the deepest edge of the epidermis where they connect to nerve endings in the dermis to sense light touch. The epidermis in most of the body is arranged into 4 distinct layers. In the palmar surface of the hands and plantar surface of the feet, the skin is thicker than in the rest of the body and there is a fifth layer of epidermis. The deepest region of the epidermis is the stratum basale, which contains the stem cells that reproduce to form all of the other cells of the epidermis. The cells of the stratum basale include cuboidal keratinocytes, melanocytes, and Merkel cells. Superficial to stratum basale is the stratum spinosum layer where Langerhans cells are found along with many rows of spiny keratinocytes. The spines found here are cellular projections called desmosomes that form between keratinocytes to hold them together and resist friction. Just superficial to the stratum spinosum is the stratum granulosum, where keratinocytes begin to produce waxy lamellar granules to waterproof the skin. The keratinocytes in the stratum granulosum are so far removed from the dermis that they begin to die from lack of nutrients. In the thick skin of the hands and feet, there is a layer of skin superficial to the stratum granulosum known as the stratum lucidum. The stratum lucidum is made of several rows of clear, dead keratinocytes that protect the underlying layers. The outermost layer of skin is the stratum corneum. The stratum corneum is made of many rows of flattened, dead keratinocytes that protect the underlying layers. Dead keratinocytes are constantly being shed from the surface of the stratum corneum and being replaced by cells arriving from the deeper layers.
- The papillary layer is the superficial layer of the dermis that borders on the epidermis. The papillary layer contains many finger-like extensions called dermal papillae that protrude superficially towards the epidermis. The dermal papillae increase the surface area of the dermis and contain many nerves and blood vessels that are projected toward the surface of the skin. Blood flowing through the dermal papillae provide nutrients and oxygen for the cells of the epidermis. The nerves of the dermal papillae are used to feel touch, pain, and temperature through the cells of the epidermis. The deeper layer of the dermis, the reticular layer, is the thicker and tougher part of the dermis. The reticular layer is made of dense irregular connective tissue that contains many tough collagen and stretchy elastin fibers 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.
- Thick and Thin Skin When we say a person has thick or thin skin, we are usually referring metaphorically to the person’s ability to take criticism. However, all of us in a literal sense have both thick and thin skin. Skin is classified as thick or thin on the basis of the structure of the epidermis.Thick skinhas all five epithelial strata, and the stratum corneum has many layers of cells. Thick skin is found in areas subject to pressure or friction, such as the palms of the hands, the soles of the feet, and the fingertips. Thin skincovers the rest of the body and is more flexible than thick skin. Each stratum contains fewer layers of cells than are found in thick skin; the stratum granulosum frequently consists of only one or two layers of cells, and the stratum lucidum generally is absent. The dermis under thin skin projects upward as separate papillae and does not produce the ridges seen in thick skin. Hair is found only in thin skin. The entire skin, including both the epidermis and the dermis, varies in thickness from 0.5 mm in the eyelids to 5.0 mm for the back and shoulders. The terms thin and thick,which refer to the epidermis only, should not be used when total skin thickness is considered. Most of the difference in total skin thickness results from variation in the thickness of the dermis. For example, the skin of the back is thin skin, whereas that of the palm is thick skin; however, the total skin thickness of the back is greater than that of the palm because more dermis exists in the skin of the back. In skin subjected to friction or pressure, the number of layers in the stratum corneum greatly increases to produce a thickened area called a callus (kalu˘s). The skin over bony prominences may develop a cone-shaped structure called a corn. The base of the cone is at the surface, but the apex extends deep into the epidermis, and pressure on the corn may be quite painful. Calluses and corns can develop in both thin and thick skin.
- The papillae of the dermis underlying thick skin are in parallel, curving ridges that shape the overlying epidermis into fingerprints and footprints. The ridges increase friction and improve the grip of the hands and feet. Fingerprints and Criminal Investigations Fingerprints were first used in criminal investigation in 1880 by Henry Faulds, a Scottish medical missionary. Faulds used a greasy fingerprint left on a bottle to identify a thief who had been drinking purified alcohol from the dispensary.
- HypodermisDeep to the dermis is a layer of loose connective tissues known as the hypodermis, subcutis, 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. Areolar connective tissue in the hypodermis contains elastin and collagen fibers loosely arranged to allow the skin to stretch and move independently of its underlying structures. 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.
- Pigments in the skin, blood circulating through the skin, and the thickness of the stratum corneum together determine skin color. Melanin is the term used to describe a group of pigments responsible for skin, hair, and eye color. Melanin is believed To provide protection against ultraviolet light from the sun. Large Amounts of melanin are found in certain regions of the skin, such As freckles, moles, nipples, areolae of the breasts, the axillae, and the Genitalia. Other areas of the body, such as the lips, the palms of the Hands, and the soles of the feet, contain less melanin. Melanin production is determined by genetic factors, hormones, and exposure to light. Albinism a recesive genetic trait causing an inability to produce tyrosinase. The result is a deficiency or absence of pigment in the skin, hair, and eyes The location of pigments and other substances in the skin affects the color produced. If a dark pigment is located in the dermis or hypodermis, light reflected off the dark pigment can be scattered by collagen fibers of the dermis to produce a blue color. The same effect produces the blue color of the sky as light is reflected from dust particles in the air. The deeper within the dermis or hypodermis any dark pigment is located, the bluer the pigment appears because of the light-scattering effect of the overlying tissue. This effect causes the blue color of tattoos, bruises, and some superficial blood vessels
- HairHair 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 palmar surface of the hands, plantar surface of the feet, lips, labia minora, and glans 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. The hair follicle is a depression of epidermal cells deep into the dermis. Stem cells in the follicle reproduce to form the keratinocytes that eventually form the hair while melanocytes produce pigment that gives the hair its color. Within the follicle is the hair root, the portion of the hair below the skin’s surface. As the follicle produces new hair, the cells in the root push up to the surface until they exit the skin. The hair shaft consists of the part of the hair that is found outside of the skin.
- Hair Structure A hair is divided into the shaft and root(figure 5.6a). The shaft protrudes above the surface of the skin, and the root is located below the surface. The base of the root is expanded to form the hair bulb(figure 5.6b). Most of the root and the shaft of the hair are composed of columns of dead keratinized epithelial cells arranged in three concentric layers: the medulla, the cortex, and the cuticle (figure 5.6c). Themedulla is the central axis of the hair and consists of two or three layers of cells containing soft keratin. The cortex forms the bulk of the hair and consists of cells containing hard keratin. The cuticle is a single layer of cells that forms the hair surface. The cuticle cells contain hard keratin, and the edges of the cuticle cells overlap like shingles on a roof. Hard keratin contains more sulfur than does soft keratin. When hair burns, the sulfur combines with hydrogen to form hydrogen sulfide, which produces the unpleasant odor of rotten eggs. In some animals such as sheep, the cuticle edges of the hair are raised and during textile manufacture catch each other and hold together to form threads
- 1. Lanugo (fetal hair) is replaced near the time of birth by terminal hairs (scalp, eyelids, and eyebrows) and vellus hairs. At puberty vellus hairs can be replaced with terminal hairs. 2. Hair is dead keratinized epithelial cells consisting of a central axis of cells with soft keratin, known as the medulla, which is surrounded by a cortex of cells with hard keratin. The cortex is covered by the cuticle, a single layer of cells filled with hard keratin. 3. A hair has three parts: the shaft, the root, and the hair bulb. 4. The hair bulb produces the hair in cycles involving a growth stage and a resting stage. 5. Hair color is determined by the amount and kind of melanin present. 6. Contraction of the arrector pili muscles, which are smooth muscles, causes hair to “stand on end” and produces “gooseflesh.”
- 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. Sebum also lubricates and protects the cuticles of hairs as they pass through the follicles to the exterior of the body.
- . 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. Eccrine sweat is delivered via a duct to the surface of the skin and is used to lower the body’s temperature through evaporative cooling. Apocrine sweat glands are found in mainly in the axillary and pubic regions of the body. The ducts of apocrine sweat glands extend into the follicles of hairs so that the sweat produced by these glands exits the body along the surface of the hair shaft. Apocrine sweat glands are inactive until puberty, at which point they produce a thick, oily liquid that is consumed by bacteria living on the skin. The digestion of apocrine sweat by bacteria produces body odor.
- 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. Cerumen is made continuously and slowly pushes older cerumen outward toward the exterior of the ear canal where it falls out of the ear or is manually removed.