integumentary system the skin and related structures
TRANSCRIPT
Integumentary System
The skin and related structures
Functions of Your Skin
• Barrier against microorganisms• Prevents water loss• Thermoregulation - helps control body temperature (click
for link)• Cutaneous sensation (for sensing your environment)• Excretion of wastes (sweating)• Aids in vitamin D production (helps body absorb calcium
and protects against some cancers)• Stores 5% of body’s blood
Layers of the skin
• Epidermis (outer most layer)
• Dermis (below epidermis)
• Hypodermis (consists of adipose tissue (fat) - separates skin from muscles (technically not part of skin))
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See Figure 5.1 on pg 153
Epidermis (see figure 5.2 on pg 154)
• Top portion of the skin
• Avascular (has no blood vessels - nutrients diffuse from the blood vessels in dermis)
• Contains four types of cells:
• Melanocytes (produce melanin (pigment) - blocks UV radiation)
• Keratinocytes (produce keratin - helps prevent water loss and acts as “tough” covering)
• Langerhans’ (dendritic) cells (part of immune system - prevents infection in the skin)
• Merkel cells (sensory receptors for touch)
Epidermal layers (see figure 5.2 on pg 154)
Outer (superficial) to inner (deep)• Stratum corneum (dead cells filled with
keratin - makes resistant to penetration and abrasions)
• Stratum lucidium (only in thick skin)• Stratum granulosum• Stratum spinosum • Stratum basale (bottom layer) - new cells
arise from this layer through mitosis (cell division). Melanocytes found here
Epidermal Layers
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Dermis• Contains blood
vessels supplying cells of epidermis
• Contains nerve endings, sweat glands, hair follicles, sebaceous (oil) glands
• Composed of the proteins collagen (strength) and elastin (stretch & recoil)
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Dermal Layers
Papillary layer - top portion- forms ridges called
dermal papillae (forms fingerprints)
- Rich in blood vesselsReticular layer- mostly collagen and
elastin fibers- Hair rooted here - Contains coiled portion of
sweat glands
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Appendages of the skin
• Sudoriferous (sweat glands)
• Sebaceous (oil) glands
• Hair
• Nails
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Sudoriferous Glands (main types)
Eccrine (merocrine) glands
• Most abundant type• Most numerous on
forehead, palms and soles of feet
• Empty secretion on skin surface
• Secretion is 99% water, some salts, and small amounts of urea, ammonia, lactic acid
Apocrine glandsFound in axillary (armpit) and anogenital regionEmpty secretions onto hair folliclesSecretions also have fatty acids and proteins (broken down by bacteria - causes body odor)
Other Sudoriferous Glands
Ceruminous glands• Make cerumen (earwax)Mammary glands• Produce milk in females
Sebaceous (oil) glands
• Attached to hair follicle: release sebum (oil) onto hair
• Found throughout skin, but most numerous on face, neck, upper chest
• Help to moisturize and waterproof hair and skin
• A pimple results when a sebaceous gland is infected
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Hair- Shaft - part of hair
extending out of the skin- hair follicle (pinching in of
the epidermis - surrounds hair)
- Hair matrix (area of dividing new cells)
- Papilla - dermal tissue at the hair root which supplies nutrients to the matrix
- Hair follicle receptor - nerve ending surrounding base of follicle
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Hair Growth
Growth phase:- last from weeks to years (scalp)- Gets shorter (especially for men)
after 40s*- Regulated by hormones and
nutritionRegressive phase:- follicle shrinks, matrix cells die,
hair falls out
*Hair loss occurs when growth phase becomes too short for new hair to emerge from scalp
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Homeostatic Imbalances of the Skin
• Skin cancers (3 main types)• Burns (1st, 2nd, and 3rd)
Genes that Control Cell Division
Proto-Oncogenes
• Initiate mitosis (accelerator)
Tumor suppressor
genes• Inhibit mitosis
(brake)*mutations must occur to both types of genes for cancer to develop
Skin CancersBasal Cell
carcinoma• most common (30%
of fair skinned people will get it
• 99% cure rate (surgically removed)
• involves stratum basale cells
• slow to metastasize
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Skin CancersSquamous Cell
carcinoma• common on head and
hands (but can happen on any exposed area)
• Can appear as red scaly elevated bump
• Can spread rapidly if not detected early
• arises from cells in stratum spinosum (keratinocytes)
Skin CancersMelanoma
• metastasizes (spreads) quickly/ highest mortality rate
• Appears as spreading brown/black patch
• one-third of cases arise from pre-existing moles QuickTime™ and a
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Self-examination for melanoma
ABCD(E) rule• Asymmetry (sides are not
the same)• Border (has
indentations/bumpy texture)
• Color (variation in the same patch)
• Diameter (larger than a pencil eraser)
• Evolution (the patch changes)
Second Degree Burns
• Epidermis and papillary layer of dermis (or deeper into dermis)
• Blistering occurs due to damaged blood vessels
• Skin heals in 3-4 weeks on average
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Third Degree Burns
• Involves full thickness of skin (dermis, epidermis, hypodermis)
• Dehydration most immediate threat
• Low blood pressure due to fluid loss
• Threat of infection• Skin grafts often
necessary
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