Bio 201 Lecture 2 PDF

Integumentary system Integumentary system – Consists of The skin and its accessory organs; – hair, – nails, – and cutaneous glands (sweat gland and sebaceous glands) 6-1 Hair  Hair and Nails Hair, nails, and cutaneous gl...

Integumentary system Integumentary system – Consists of The skin and its accessory organs; – hair, – nails, – and cutaneous glands (sweat gland and sebaceous glands) 6-1 Hair  Hair and Nails Hair, nails, and cutaneous glands are accessory organs 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 cross- linkages between keratin molecules 6-3  Hair and Nails Pilus—another name for hair; pili—plural of pilus Hair—a slender filament of keratinized cells that grows from an oblique tube in the skin called a hair follicle 6-4 Hair Hair shaft Keratinocytes  Hair Hair is found almost everywhere on the body except: – Palms and soles – Ventral and lateral surfaces of fingers and toes – Distal segment of the finger – Lips, nipples, and parts of genitals Limbs and trunk have 55 to 70 hairs per – 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 6-6  Hair Three kinds of hair grow over the course of our lives 1. Lanugo 2. Vellus 3. Terminal 6-7  Hair Three kinds of hair grow over the course of our lives – Lanugo: fine, downy, unpigmented hair that appears on the fetus in the last 3 months of development – Vellus: fine, pale hair that replaces lanugo by time of birth Two-thirds of the hair of women One-tenth of the hair of men All of hair of children except eyebrows, eyelashes, and hair of the scalp – Terminal: longer, coarser, and usually more heavily pigmented Forms eyebrows, eyelashes, and the hair of the scalp After puberty, forms the axillary and pubic hair Male facial hair and some of the hair on the trunk and limbs 6-8  Structure of the Hair and Follicle Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Hair is divisible into three zones along its length – Bulb: a swelling at the Hair shaft base where hair originates in dermis or hypodermis Only living hair cells are in or near bulb Sebaceous gland Piloerector muscle – Root: the remainder of the Hair receptor Hair root Bulge Hair matrix hair in the follicle Apocrine sweat gland Hair bulb Dermal – Shaft: the portion above Blood papilla the skin surface capillaries in dermal papilla (a) Figure 6.7a 6-9  Structure of the Hair and Follicle Dermal papilla—bud of vascular connective tissue Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. encased by bulb Connective – Provides the hair with its sole tissue root sheath source of nutrition Epithelial root sheath Hair medulla Hair matrix—region of Hair cortex mitotically active cells Hair matrix immediately above papilla Hair bulb Dermal papilla – Hair’s growth center (b) 0.5 mm © CBS/Phototake Figure 6.7b 6-10  Structure of the Hair and Follicle Three layers of the hair in cross section – Medulla Core of loosely arranged cells and air spaces – Cortex Constitutes bulk of the hair Consists of several layers of elongated keratinized cells – Cuticle Composed of multiple layers of very thin, scaly cells that overlap each other Free edges directed upward  Structure of the Hair and Follicle Follicle—diagonal tube contains the hair root that extends into dermis and possibly hypodermis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Follicle has 2 principle layers: Connective tissue root sheath – Epithelial root sheath Epithelial root Extension of the epidermis lying sheath adjacent to hair root Hair cortex Widens at deep end into bulge— Hair matrix source of stem cells for follicle growth Hair bulb Dermal papilla – Connective tissue root sheath Derived from dermis but a bit denser (b) 0.5 mm Surrounds epithelial root sheath 6-12  Structure of the Hair and Follicle Hair receptors – Nerve fibers that entwine each follicle – Respond to hair movement Piloerector muscle (arrector pili) – Bundles of smooth muscle cells – Extends from dermal collagen to connective tissue root sheath – Goose bumps 6-13  Hair Texture and Color Texture—related to cross-sectional shape of hair – Straight hair is round – Wavy hair is oval – Curly hair is relatively flat  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 a slight amount of eumelanin but a 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 in the cortex and the presence of air in the medulla 6-15  Hair Growth and Loss Hair cycle—consists of three developmental stages 1. Anagen 2. Catagen 3. Telogen 6-16  Hair Growth and Loss Three stages of hair cycle – Anagen: growth stage 90% of scalp follicles at a given time Stem cells multiply Root sheath cells above papilla form hair cells of hair matrix Hair cells make keratin and die as they are pushed upward – Catagen: degeneration stage Mitosis in hair matrix stops and sheath cells below bulge die Base of hair keratinizes into a hard club—club hair – Easily pulled out by brushing – Telogen: resting stage When papilla reaches the bulge  The Hair Cycle Copyright © McGraw-Hill Education. Permission required for reproduction or display. 1) Anagen (early) Anagen (mature) 2)Catagen 3)Telogen Stem cells multiply and follicle grows deeper into dermis; (Degenerative phase, 2-3 (Resting phase, 1-3 hair matrix cells multiply and keratinize, causing hair to grow weeks) months) upward; old club hair may persist temporarily alongside Hair growth ceases; hair bulb Dermal papilla has newly growing hair. keratinizes and forms club ascended to level of bulge; hair; lower follicle club hair falls out, usually degenerates. in telogen or next anagen.  Hair Growth and Loss We lose about 50-100 hairs daily – A club hair may fall out during catagen or telogen or be pushed out in the next anagen phase – In young adults, scalp follicles spend 6–8 years in anagen, 2–3 weeks in catagen, 1–2 months in telogen Hair growth—scalp hairs grow 1 mm per 3 days Alopecia—thinning of the hair or baldness Pattern baldness—hair lost from select regions – Baldness allele is dominant in males and expressed when testosterone levels are high – Testosterone causes terminal hair on top of scalp to be replaced by vellus hair Hirsutism—excessive or undesirable hairiness in areas that are not usually hairy  Functions of Hair Most hair on trunk and limbs is vestigial – Has little present function but kept ancestors warm Hair receptors alert us of parasites crawling on skin Scalp 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, preventing foreign particles entering easily Eyelashes and eyebrows – Keep the sweat and debris out-negligible – Nonverbal communication  Nails Fingernails and toenails—clear, hard derivatives of stratum corneum – Composed of thin, dead cells packed with hard keratin Functions: – Improve grooming, picking apart food, other manipulations – Provide a counterforce to enhance sensitivity of fleshy fingertips to tiny objects  Anatomy of a Fingernail Copyright © McGraw-Hill Education. Permission required for reproduction or display. Nail plate—hard part of the nail – Free edge: overhangs the fingertip – Nail body: visible attached part of nail – Nail root: extends proximally under overlying skin  Nails Nail fold—surrounding skin rising above nail Nail groove—separates nail fold from nail plate Nail bed—skin underlying the nail plate – Hyponychium—epidermis of the nail bed  Nails Nail matrix—growth zone (mitotic) of thickened stratum basale at proximal end of nail – 1 mm per week in fingernails, slightly slower in toenails – Lunule—opaque white crescent at proximal end of nail due to thickness of matrix Eponychium (cuticle)— narrow zone of dead skin overhanging proximal end of nail  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. 6-25  Sweat Glands Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Lumen Secretory Myoepithelial Lumen cells cells Gland Hair follicle Secretory cells (c) Sebaceous gland © The McGraw-Hill Companies, Inc./Joe DeGrandis, photographer (a) Apocrine gland © The McGraw-Hill Companies, Inc./Joe DeGrandis, photographer (b) Merocrine gland © The McGraw-Hill Companies, Inc./Joe DeGrandis, photographer The skin has five types of glands: 1. Sweat glands merocrine sweat glands, apocrine sweat glands, 2. sebaceous glands, 3. ceruminous glands, 4. and mammary glands 6-26  Sweat Glands Two kinds of sweat (sudoriferous) glands – Merocrine (eccrine) sweat glands Most numerous skin glands—3 to 4 million in adult skin Simple tubular glands Watery perspiration that helps cool the body Myoepithelial cells—contract in response to stimulation by sympathetic nervous system and squeeze perspiration up the duct 6-27  Merocrine Sweat Epidermis Gland Low Magnification Merocrine sweat gland and duct Dermis Merocrine sweat gland Hypodermis Duct of merocrine sweat gland  Merocrine Sweat Gland High Magnification Epithelial cells of Merocrine sweat gland sweat gland Lumen of sweat gland Myoepithelial cells Basal lamina of merocrine sweat gland Duct of Sweat Gland High Magnification Epidermis Dermis Duct of sweat gland  Sweat Glands Cont. – Apocrine sweat glands Unfortunately they are misnamed Because they do not use the apocrine mode of secretion They use merocrine mode of secretion Endocrine glands, exocrine glands Modes of secretions: 6-31  Sweat Glands Cont. – Apocrine sweat glands Occur in groin, anal region, axilla, areola, bearded area in mature males Ducts lead to nearby hair follicles Produce sweat that is thicker, milky, and contains fatty acids Scent glands that respond to stress and sexual stimulation Develop at puberty (Absent) from axillary regions of Koreans/east Asian ABCC11 gene, allele (A and G) and sparse in Japanese Pheromones—chemicals that influence the physiology of behavior of other members of the species Bromhidrosis—disagreeable body odor produced by bacterial action on fatty acids 6-32  Epithelium Apocrine Sweat Gland Low Magnification Lumen Apocrine sweat gland  Apocrine Sweat Gland High Magnification Apocrine sweat gland Lumen Epithelial cells Myoepthelial cells  Sweat Glands Sweat—begins as a protein-free filtrate of blood plasma produced by deep secretory portion of gland – Potassium ions, urea, lactic acid, ammonia, and some sodium chloride remain in the sweat, most sodium chloride reabsorbed by duct – Some drugs are also excreted in sweat – On average, 99% water, with pH range of 4 to 6 Acid mantle—inhibits bacterial growth – Insensible perspiration—500 mL/day Does not produce visible wetness of skin – Diaphoresis—sweating with wetness of the skin Exercise—may lose 1 L sweat per hour 6-35  Sebaceous Glands Sebum—oily secretion produced by sebaceous glands Flask-shaped glands with short ducts opening into hair follicle Holocrine gland—secretion consists of broken- down cells – Replaced by mitosis at base of gland Keeps skin and hair from becoming dry, brittle, and cracked Lanolin—sheep sebum 6-36  Basal cell of Sebaceous gland sebaceous gland Duct of Secretory cells sebaceous gland Hair follicle Sebaceous gland High Magnification  Mammary Glands Breast (mammae) present in both sexes but Mammary glands—milk-producing glands that develop only during pregnancy and lactation – Modified apocrine sweat glands – Rich secretion released through ducts opening at 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)  Mammary Glands Primates kept only two glands, but a few people have additional nipples along the milk line (polythelia) 6-39  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. 6-40  Skin Cancer Skin cancer—induced by the UV rays of the sun – Most often on the head and neck – Most common in fair-skinned people and the elderly – One of the most common cancer – One of the easiest to treat – Has one of the highest survival rates if detected and treated early Three types of skin cancer named for the epidermal cells in which they originate 1. Basal cell carcinoma, 2. squamous cell carcinoma, 3. and malignant melanoma 6-41  Skin Cancer Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (a) Basal cell carcinoma © NMSB/Custom Medical Stock Photo, Inc. Basal cell carcinoma - Most common type - Least dangerous because it seldom metastasizes - Forms from cells in stratum basale - Lesion is small, shiny bump with central depression and beaded edges 6-42  Skin Cancer Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (b) Squamous cell carcinoma © Biophoto Associates/Photo Researchers, Inc. Squamous cell carcinoma - Arise from keratinocytes from stratum spinosum - Lesions usually appear on scalp, ears, lower lip, or back of the hand - Have raised, reddened, scaly appearance later forming a concave ulcer - Chance of recovery good with early detection and surgical removal - Tends to metastasize to lymph nodes and may become lethal 6-43  Skin Cancer Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (c) Malignant melanoma © James Stevenson/SPL/Photo Researchers, Inc. Malignant melanoma - Skin cancer that arises from melanocytes; often in a preexisting mole - Less than 5% of skin cancers, but most deadly form - Treated surgically if caught early - Metastasizes rapidly; unresponsive to chemotherapy; usually fatal 6-44  Skin Cancer Cont. - Person with metastatic melanoma lives only 6 months from diagnosis - 5% to 14% survive 5 years - Greatest risk factor: familial history of malignant melanoma - High incidence in men, redheads, people who experience severe - sunburn in childhood 6-45  Skin Cancer - The American Cancer Society suggest an “ABCD” rule - A: Asymmetry - B: Border irregularity - C: Color (mixture of brown/black, sometimes red and blue) - D: Diameter (greater than 6 mm) 6-46  UVA, UVB and Sunscreens UV radiation is divided into two wavelength: UVA and UVB UVA so called “tanning rays” longer wavelength and lower energy UVB rays so called “burning rays” shorter wavelength and higher energy Tanning salons advertise to use UVA but this can burn and it is involved in photoaging of the skin Both UVA and UVB can initiate skin cancer Dermatologist: There is not such a thing as health tanning 6-47  UVA, UVB and Sunscreens Sunscreens protect you from sunburn – Sun protection factor (SPF) is laboratory measure of protection from UVB radiation – Minimum SPF should be 15 (protect skin from 93% of UVB) – SPF 30 does not protect twice as much (protect skin 97% of UVB) – SPF factors above 30 considered to be misleading by Australian government – Effectiveness depends on the amount applied and frequency – Protects from the burn but sometimes not from cancer. – Zinc oxide and titanium oxide damage DNA.. 6-48  Burns Burns—leading cause of accidental death – Fires, kitchen spills, sunlight, ionizing radiation, strong acids or bases, or electrical shock – Deaths result primarily from fluid loss, infection, and toxic effects of eschar (burned, dead tissue) – Debridement: removal of eschar  Burns Classified according to the depth of tissue involvement – First-degree burn: involves only the epidermis – Second-degree burn: partial-thickness burn – Third-degree burn: full-thickness burn 6-50  Burns – First-degree burn: involves only the epidermis Marked by redness, slight edema, and pain Heals in a few days Most sunburns are first-degree burns – Second-degree burn: partial-thickness burn; involves the epidermis and part of the dermis Leaves part of the dermis intact Red, tan, or white Two weeks to several months to heal and may leave scars Blistered and very painful – Third-degree burn: full-thickness burn; the epidermis and all of the dermis, and often some deeper tissues (muscles or bones) are destroyed Often requires skin grafts Needs fluid replacement and infection control 6-51  Degrees of Burn Injuries Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Partial-thickness burns Full-thickness burns (a) First degree (b) Second degree (c) Third degree a: © SPL/Custom Medical Stock Photo, Inc.; b-c: © John Radcliffe/Photo Researchers, Inc. Figure 6.13 6-52  Skin Grafts and Artificial Skin Third-degree burns require skin grafts Graft options – Autograft: tissue taken from another location on the same person’s body Split-skin graft—taking epidermis and part of the dermis from an undamaged area such as the thigh or buttocks and grafting it into the burned area – Isograft: skin from identical twin 6-53  Skin Grafts and Artificial Skin Temporary grafts (immune system rejection) – Homograft (allograft): from unrelated person – Heterograft (xenograft): from another species – Sometimes burns are temporarily covered with Amnion (from afterbirth) – Artificial skin from silicone and collagen 6-54