BSC 2085 Lesson 7: The Integumentary System PDF

Because learning changes everything. ® BSC 2085: A&P I Fall 2024 Instructor: Dr. Yung Su Lesson 7: Chapter 06 The Integumentary System ANATOMY & PHYSIOLOGY The Unity of Form and Function TENTH EDITION KENNETH S. SALADIN © McGraw Hill LLC. All rights reserved. N...

Because learning changes everything. ® BSC 2085: A&P I Fall 2024 Instructor: Dr. Yung Su Lesson 7: Chapter 06 The Integumentary System ANATOMY & PHYSIOLOGY The Unity of Form and Function TENTH EDITION KENNETH S. SALADIN © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.  Introduction Inspection of the skin, hair, and nails is significant part of a physical exam Skin is the most vulnerable organ Exposed to radiation, trauma, infection, and chemicals Receives more medical treatment than any other organ system Dermatology – scientific study and medical treatment of integumentary system © McGraw Hill, LLC 2  6.1 The Skin and Subcutaneous Tissue 1 Expected Learning Outcomes: List the functions of the skin and relate them to its structure. Describe the histological structure of the epidermis, dermis, and subcutaneous tissue. Describe the normal and pathological colors that the skin can have, and explain their causes. Describe the common markings of the skin. © McGraw Hill, LLC 3  6.1 The Skin and Subcutaneous Tissue 2 The integumentary system consists of the cutaneous membrane (skin) & accessory structures (hair, nails, glands) The skin (integument) is body’s largest and heaviest organ Covers area 1.5 to 2.0 m2 Composes 8% of body weight Skin consists of two layers: Epidermis: stratified squamous epithelium Dermis: deeper connective tissue layer – accessory structures originate in the dermis Below the dermis is the hypodermis (superficial fascia/ subcutaneous layer), not part of the skin but usually studied with it © McGraw Hill, LLC 4  Structure of the Skin and Subcutaneous Tissue Access the text alternative for slide images. Figure 6.1 © McGraw Hill, LLC 5  The Skin and Subcutaneous Tissue 3 Skin thickness ranges from 0.5 to 6 mm Thickness range mainly due to variation in dermis thickness, but skin is classified as thick or thin based on epidermis Thick skin covers palms, soles, and corresponding surfaces of fingers and toes Has sweat glands, but no hair follicles or sebaceous (oil) glands Epidermis about 0.5 mm thick, primarily due to thick stratum corneum Thin skin covers rest of the body Has hair follicles, sebaceous glands, and sweat glands Epidermis about 0.1 mm thick © McGraw Hill, LLC 6  6.1a Functions of the Skin 1 1. Protection – Resistance to trauma and infection Keratin provides physical protection Dermcidin, defensins, and acid mantle protect against bacteria Barrier to water, ultraviolet (UV) rays, harmful chemicals 2. Vitamin D synthesis UV radiation causes epidermal cell to produce cholecalciferol (vitamin D3) – converted to calcitriol by the liver and kidneys 3. Sensation Many nerve endings that react to various stimuli 4. Thermoregulation Alters blood flow to release or retain heat Cutaneous vasoconstriction, cutaneous vasodilation 5. Nonverbal communication Facial expressions © McGraw Hill, LLC 7  6.1b The Epidermis General features of the epidermis Keratinized stratified squamous epithelium Includes dead cells at skin surface packed with tough keratin protein Avascular (lacks blood vessels) Depends on the diffusion of nutrients from underlying connective tissue Contains sparse nerve endings for touch and pain © McGraw Hill, LLC 8  Cells of the Epidermis 1 Five epidermal cell types: 1. Keratinocytes Great majority of epidermal cells Synthesize keratin 2. Stem cells Undifferentiated cells that give rise to keratinocytes In deepest layer of epidermis, stratum basale 3. Melanocytes Synthesize pigment melanin that shields DNA from ultraviolet radiation Occur only in stratum basale but have branched processes that spread among keratinocytes and distribute melanin via melanosomes © McGraw Hill, LLC 9  Cells of the Epidermis 2 Five epidermal cell types (continued): 4. Tactile cells Touch receptor cells associated with dermal nerve fibers Tactile/Merkel disc – collective term for tactile/Merkel cell and associated nerve fiber In basal layer of epidermis 5. Dendritic cells Phagocytic immune cells that guard against toxins, microbes Found in stratum spinosum and stratum granulosum © McGraw Hill, LLC 10  Layers and Cell Types of the Epidermis a: Biophoto Associates/Science Source Access the text alternative for slide images. Figure 6.3 © McGraw Hill, LLC 11  Layers of the Epidermis 1 Cells of epidermis arranged in four to five zones, or strata, listed here from deep to superficial: Stratum basale Single layer of stem cells and keratinocytes resting on the basement membrane Also contains scattered melanocytes and tactile cells Stratum spinosum Several layers of living keratinocytes joined by desmosomes and tight junctions Named for appearance of cells after histological preparation (spiny) Contains dendritic (Langerhans) cells that defend against invaders Stratum granulosum Three to five layers of flat, living keratinocytes that start to dehydrate and die Cells contain dark-staining keratohyalin granules © McGraw Hill, LLC 12  Layers of the Epidermis 2 Cells of epidermis (continued) Stratum lucidum Thin, pale layer found only in thick skin Keratinocytes packed with clear protein eleidin Cells here lack nucleus/organelles Stratum corneum Up to 30 layers of dead, scaly, keratinized cells Resists abrasion, penetration, water loss © McGraw Hill, LLC 13  The Life History of a Keratinocyte 1 Keratinocytes produced by mitosis in stratum basale or deepest part of stratum spinosum Mitosis requires abundant oxygen and nutrients Once cells migrate away from blood vessels of the dermis, mitosis cannot occur New keratinocytes push older ones toward the surface (stratum corneum) Over time, keratinocytes flatten, produce more keratin and lipid-filled lamellar granules In 30 to 40 days a keratinocyte makes its way to the skin surface and exfoliates (flakes off) as specks called dander (may combine with oil to become dandruff) Keratinocyte multiplication is slower in old age, faster in injured or stressed skin Calluses or corns are thick accumulations of dead keratinocytes on hands or feet © McGraw Hill, LLC 14  The Life History of a Keratinocyte 2 Life history of a keratinocyte (continued): Epidermal water barrier – located in the stratum granulosum, it is formed from lipids from keratinocytes as well as tight junctions between them Helps prevent dehydration Does not prevent the absorption of water by the stratum corneum when we soak in a bath (“prune fingers”) So why do our fingers get wrinkles when submerged in water? © McGraw Hill, LLC 15  6.1c The Dermis 1 Beneath the epidermis is the dermis General features: Connective tissue layer 0.2 mm to 4 mm thick Composed mainly of collagen; also contains elastic and reticular fibers Well supplied with blood vessels, sweat glands, sebaceous glands, and nerve endings Houses hair follicles and nail roots Muscles of facial expression attach to dermis Wavy, conspicuous boundary between dermis and epidermis Dermal papillae are upward, finger-like extensions of dermis Epidermal ridges are downward waves of epidermis © McGraw Hill, LLC 16  The Dermis 2 The dermis consists of two zones: Papillary layer Thin zone of areolar tissue in and near the dermal papillae Allows for mobility of leukocytes and other defense cells Rich in small blood vessels Reticular layer Deeper, thicker layer of dermis Composed of dense irregular connective tissue Stretch marks (striae) – tears in the collagen fibers caused by stretching of the skin due to pregnancy or obesity Damaged dermal blood vessels (burns, shoe friction) may cause serous fluid to seep out and form a blister between dermis and epidermis © McGraw Hill, LLC 17  The Dermis 3 Dermal strength and elasticity Two types of fibers found in the dermis 1. Collagen fibers Strong, resists stretching but can bend easily Provides flexibility 2. Elastic fibers Permits stretching when pulled, when released, recoils back to original length Provides flexibility and stretching (though the stretching is dependent on the collagen fibers) Skin turgor – caused by H2O content in skin Dehydrated skin shows loss of turgor (flexibility and resilience) – pinched skin stays pinched after release © McGraw Hill, LLC 18  The Dermis 3 Skin turgor test © McGraw Hill, LLC 19  The Dermis 4 Dermatitis – inflammation of the papillary layer Characterized by pain/itchiness Inflammation can rapidly spread across the entire integument Caused by infection, radiation, mechanical or chemical (Ex: poison ivy) irritation Decubitus ulcers – bedsores caused by problems with dermal circulation Caused by compression of superficial blood vessels Sores common on skin covering joints or bony prominences Kills epithelial cells, erodes dermal tissue © McGraw Hill, LLC 20  Layers of the Dermis a: © Dennis Strete/McGraw-Hill; b: © David M. Phillips/Science Source; c: © Susumu Nishinaga/Science Source Access the text alternative for slide images. Figure 6.4 © McGraw Hill, LLC 21  6.1e Skin Color 1 Variations in skin and hair color due primarily to type and amount of melanin pigment Melanin produced in melanocytes, stored in melanosomes (vesicles) Melanosomes transferred to keratinocytes where they cluster around the cell nucleus to absorb UV radiation (radiation can damage DNA) Dark eumelanin and reddish-yellow pheomelanin Eumelanin varieties: brown and black eumelanin; responsible for tan, brown, and black skin Pheomelanin responsible for yellowish to reddish tones in some Asians and Native Americans, and pinkish tones of white skin © McGraw Hill, LLC 22  Skin Color 2 Skin color (continued): Other contributing factors: UV radiation stimulates melanin synthesis Degree of show-through of dermal vessels and white collagen Possible accumulation of carotene pigment from yellow and orange vegetables (carrots, squash) Carotene Accumulates in epidermal cells and fatty tissues of the dermis Used to produce vitamin A – needed for epithelial maintenance and pigment for photoreceptors for vision Lack of vitamin A can cause night blindness (nyctalopia) © McGraw Hill, LLC 23  Skin Color 3 Skin colors of diagnostic value: Cyanosis – blueness due to oxygen deficiency Erythema – redness due to increased blood flow to skin Pallor – paleness due to decreased blood flow to skin Albinism – white skin due to genetic lack of melanin Vitiligo – loss of skin color in patches due to loss of melanocytes, probably cause by autoimmune reaction to melanocytes Jaundice – yellowing due to bilirubin in blood Can be caused by compromised liver function Hematoma – bruising, blood clotting under skin © McGraw Hill, LLC 24  Two Abnormal Skin Colors Albinism Jaundice a: Iraidka/Shutterstock; b: Dr P. Marazzi/Science Source Figure 6.7 © McGraw Hill, LLC 25  6.1f Skin Markings 1 Skin has a variety of markings: Friction ridges – formed from dermal papillae Markings on the fingertips that leave oily fingerprints Everyone has a unique pattern formed during fetal development that remains unchanged throughout life; not even identical twins have identical fingerprints Enhance fingertip sensitivity; improve grip Flexion lines (flexion creases) Lines on the flexor surfaces of the digits, palms, wrists, elbows Mark sites where skin folds during flexion of joints © McGraw Hill, LLC 26  Skin Markings 2 Skin markings (continued): Freckle – flat, melanized patch Mole (nevus) – elevated, melanized patch, often with hair Should be watched for changes in color, diameter, or contour that may suggest cancer Hemangiomas (birthmarks) Patches of discolored skin caused by benign tumors of dermal capillaries Some disappear in childhood, others last for life Examples: capillary hemangioma (strawberry birthmark), cavernous hemangioma, port-wine stain © McGraw Hill, LLC 27  6.1d The Hypodermis Hypodermis (subcutaneous tissue) – layer of connective tissue beneath the skin Contains more areolar and adipose tissue than the dermis Pads body and binds skin to underlying tissues Common site of drug injection (hypodermic needles) due to many blood vessels Subcutaneous fat – refers to subcutaneous tissue that is comprised predominantly of adipose tissue Energy reservoir Thermal insulation Thicker in females; Thinner in infants and elderly © McGraw Hill, LLC 28  6.2 Hair and Nails Expected Learning Outcomes: Distinguish between three types of hair. Describe the histology of a hair and its follicle. Discuss some theories of the purposes served by various kinds of hair. Describe the structure and function of nails. © McGraw Hill, LLC 29  Hair and Nails Introduction Hair, nails, and cutaneous glands are the accessory organs (appendages) of the skin Hair and nails are composed of mostly dead, keratinized cells Pliable soft keratin makes up stratum corneum of skin Compact hard keratin makes up hair and nails Tougher and more compact due to numerous disulfide bridges between keratin molecules © McGraw Hill, LLC 30  Functions of Hair Hair function depends on body region and type of hair Hair receptors alert us of parasites crawling on skin Hair on trunk and limbs is mostly vestigial Scalp hair retains heat and protects against sunburn Pubic and axillary hair – signify sexual maturity and aid in transmission of sexual scents Guard hairs (vibrissae) guard nostrils and ear canals Eyelashes and eyebrows enhance facial expression and nonverbal communication © McGraw Hill, LLC 31  6.2a Hair 1 A hair is also called a pilus (plural: pili) Slender filament of keratinized cells growing from a tube in the skin called a hair follicle Hair covers most of the body Hair does not cover: palms, soles; palmar, plantar, and lateral surfaces and distal segments of fingers and toes; lips, nipples, and parts of genitals Limbs and trunk have 55 to 70 hairs per square cm; face has about 10 times as many; 100,000 hairs on an average person’s scalp Differences in hairiness across individuals is mainly due to differences in texture and pigment of hair © McGraw Hill, LLC 32  Hair 2 Three types of hair: Downy hair (lanugo) Fine, downy, unpigmented hair that appears on the fetus in the last 3 months of development Vellus hair Fine, pale hair that replaces lanugo by time of birth Two-thirds of the hair of females; one-tenth of the hair of males; all the hair of children except eyebrows, eyelashes, and scalp hair Terminal hair Longer, coarser, more heavily pigmented Eyebrows, eyelashes, and hair of the scalp After puberty, forms axillary and pubic hair Male facial hair and some of the hair on the trunk and limbs © McGraw Hill, LLC 33  Structure of the Hair and Follicle 1 Structure of a hair: Shaft is portion above skin surface, root is portion below skin surface In dermis or hypodermis, hair root ends with dilated bulb Bulb grows around dermal papilla – bud of vascular connective tissue, provides nutrition to hair Hair matrix – mitotically active cells immediately above the papilla; growth center for the hair Hair has up to three layers: Medulla – core of loosely arranged cells and air spaces Cortex – bulk of the hair; layers of elongated cells Cuticle – outermost region consisting of multiple layers of thin, scaly cells that overlap like roof shingles © McGraw Hill, LLC 34  Structure of a Hair and Its Follicle b: Ed Reschke/Stone/Getty Images Access the text alternative for slide images. Figure 6.8 © McGraw Hill, LLC 35  Structure of the Hair and Follicle 2 Structure of a follicle: Two principle layers Epithelial root sheath – extension of the epidermis lying adjacent to hair root; widens at deep end into bulge, a source of stem cells for follicle growth Connective tissue root sheath – derived from dermis but a bit denser; surrounds epithelial root sheath Associated with the follicle: Sensory nerve fibers entwine each follicle and respond to hair movements Arrector muscle – bundle of smooth muscle attaching follicle to dermis; contracts to make hair stand on end (piloerection) © McGraw Hill, LLC 36  Hair Texture and Color Color due to pigment granules in the cells of the cortex Brown and black hair is rich in eumelanin Red hair has high concentration of pheomelanin Blond hair has an intermediate amount of pheomelanin and very little eumelanin Gray and white hair have little or no melanin; air present in medulla Texture related to cross-sectional shape of hair Straight hair is round Wavy hair is oval Curly hair is relatively flat © McGraw Hill, LLC 37  6.2b Nails 1 Fingernails and toenails Clear, hard derivatives of stratum corneum Composed of thin, dead cells packed with hard keratin Functions of nails Improve grooming, picking apart food, other manipulations Provide a counterforce to enhance sensitivity of fleshy fingertips to tiny objects Structure of the nail: Nail plate – hard part of nail; includes overhanging free edge, nail body (visible attached part), and nail root under overlying skin Surrounding skin rises as a nail fold, separated from the margin of the nail plate by the nail groove © McGraw Hill, LLC 38  Nails 2 Structure of the nail (continued): Nail bed – skin underlying the nail plate Nail matrix – growth zone at proximal end of nail; its thickness obscures underlying vessels and appears as white lunule Cuticle (eponychium) – narrow zone of dead skin that overhangs proximal end of nail Appearance of nails can be valuable in medical diagnosis Swollen, clubbed fingertips in oxygen deficiency Dietary deficiencies © McGraw Hill, LLC 39  Anatomy of a Fingernail Access the text alternative for slide images. Figure 6.10 © McGraw Hill, LLC 40  6.3 Cutaneous Glands Expected Learning Outcomes: Name two types of sweat glands, and describe the structure and function of each. Describe the location, structure, and function of sebaceous and ceruminous glands. Discuss the distinction between breasts and mammary glands, and explain their respective functions. © McGraw Hill, LLC 41  6.3a Sweat Glands 1 Two kinds of sweat glands: apocrine and eccrine (Note: both apocrine and eccrine sweat glands use exocytosis for their mode of secretion) Apocrine sweat glands Groin, anal region, axilla, areola, beard area in males Ducts lead to nearby hair follicles; produce sweat that is milky and contains fatty acids Inactive until puberty; respond to stress and sexual stimulation Bromhidrosis – disagreeable body odor; usually inadequate hygiene © McGraw Hill, LLC 42  Sweat Glands 2 Types of sweat glands (continued) Eccrine (merocrine) sweat glands Most numerous skin glands – 3 to 4 million in adult skin, especially dense on palms, soles, and forehead Simple tubular glands produce watery perspiration that helps cool the body Myoepithelial cells Found in both apocrine and eccrine glands Contract in response to stimulation by sympathetic nervous system and squeeze perspiration up the duct © McGraw Hill, LLC 43  Cutaneous Glands (a-c): © Dennis Strete/McGraw-Hill Access the text alternative for slide images. Figure 6.11 © McGraw Hill, LLC 44  Sweat Glands 3 Sweat production and composition 99% water pH range of 4 to 6 Acid mantle – inhibits bacterial growth Begins as a protein-free filtrate of blood plasma produced by deep secretory portion of gland Some sodium chloride reabsorbed by duct, but some sodium chloride and other small solutes (potassium, urea, lactic acid, ammonia) remain in the sweat Some drugs are excreted in sweat (alcohol, cocaine, heroin, amphetamines) © McGraw Hill, LLC 45  Sweat Glands 4 Types of perspiration Insensible perspiration – not noticed; does not produce visible wetness of skin. Lose approx. 500 ml/day Cutaneous transpiration – water loss from skin not due to sweating. Water diffuses between the keratinocytes and evaporates from the skin surface Diaphoresis – sensible perspiration; sweating with wetness of the skin, in response to heat, exercise, circulatory shock 1 L or more of sweat per hour may be lost during exercise © McGraw Hill, LLC 46  6.3b Sebaceous Glands Sebaceous glands produce oily secretion called sebum Gland structure: Flask-shaped, short ducts open into hair follicles Holocrine mode of secretion Keeps skin and hair from becoming dry, brittle, and cracked © McGraw Hill, LLC 47  6.3c Ceruminous Glands Ceruminous glands – modified apocrine glands found only in the external ear canal Coiled, simple tubular glands Produce cerumen (earwax) Yellow, waxy secretion combined with sebum and dead epithelial cells; waterproofs the canal Keeps eardrum pliable Kills bacteria Makes guard hairs of ear sticky to help block foreign particles from entering auditory canal © McGraw Hill, LLC 48  6.3d Mammary Glands Mammary glands – milk-producing glands that develop in female during pregnancy and lactation Modified apocrine sweat glands Rich secretion released through ducts opening at the nipple Mammary ridges or milk lines – two rows of mammary glands in most mammals Primates kept only two glands, but a few people have additional nipples along the milk line (polythelia) © McGraw Hill, LLC 49  6.4 Skin Disorders Expected Learning Outcomes: Describe the three most common forms of skin cancer. Describe the three classes of burns and the priorities in burn treatment. © McGraw Hill, LLC 50  6.4a Skin Cancer Most skin cancer is caused by exposure to UV rays of the sun Most often on the head, neck, and hands. Most common in fair-skinned people and the elderly One of the most common, easily treated cancers Highest survival rates if detected and treated early Three types of skin cancer named for the epidermal cells in which they originate: Basal cell carcinoma Squamous cell carcinoma Malignant melanoma © McGraw Hill, LLC 51  Basal Cell Carcinoma Most common type Least dangerous because it seldom metastasizes Forms from cells in stratum basale Small, shiny bump with central depression and beaded edges a: jax10289/Shutterstock Figure 6.12a © McGraw Hill, LLC 52  Squamous Cell Carcinoma Arises from keratinocytes of stratum spinosum Lesions usually on scalp, ears, lower lip, or back of the hand Raised, reddened, scaly appearance later forming a concave ulcer Chance of recovery good with early detection and removal Tends to metastasize to lymph nodes and may become lethal b: DR P. Marazzi/Science Photo Library/Alamy Stock Photo Figure 6.12b © McGraw Hill, LLC 53  Melanoma Arises from melanocytes Less than 5% of skin cancers Can be successfully removed if caught early, but usually fatal if metastasizes Greatest risk factor is familial history Highest incidence in males, redheads, people who had severe sunburn as a child ABCDE Rule for detecting melanomas: Asymmetry (in shape), Border irregularity, Color c: Source: National Cancer Institute (NCI) (mix of brown, black, tan, red/blue), Diameter (greater than 6 mm), Evolving (size, shape, Figure 6.12c color) © McGraw Hill, LLC 54  6.4b Burns Burns can result in death due to fluid loss, infection, and toxic effects of eschar – the burned, dead tissue Classified according to depth of tissue involvement: First-degree burn – only involves the epidermis Redness, slight edema, and pain Heals within days Second-degree burn (partial-thickness burn) – involves part of dermis May appear red, tan, or white; blistered and painful Two weeks to several months to heal and may leave scars Third-degree burn (full-thickness burn) – involves all of dermis and often some deeper tissues Often requires skin grafts; need fluid replacement, infection control, supplemental nutrition © McGraw Hill, LLC 55  Skin Grafts Third-degree burns often require skin grafts Autograft – tissue from another location on the same person’s body Allograft – tissue from unrelated person, usually deceased donors Artificial and lab-based approaches under development Epidermal growth factor (EGF) – peptide growth factor that: Promote division of germinative cells Accelerates keratin production Stimulates epidermal repair Stimulates glandular secretions Figure 6.5 A Meshed Skin Graft © McGraw Hill, LLC 56  Burns a: Dmitrii Kotin/Alamy Stock Photo; b: thawatchai_bandit/Shutterstock; c: Anukool Manoton/Shutterstock Access the text alternative for slide images. Figure 6.13 © McGraw Hill, LLC 57