Transcript The Human Body in Health and Illness

Chapter 7:
Skin and Appendages
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Lesson 7-1 Objectives
• List six functions of the skin.
• Define stratum germinativum and stratum
corneum.
• Describe the two layers of the
skinepidermis and dermis.
• List the two major functions of the
subcutaneous layer.
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Introduction
Skin (integument) is body’s
largest organ
 Integumentary system describes
the skin and its appendages—the
hair, nails, and skin glands
 You shed about 1.5 lbs per year
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Skin Perspective
• On average, 1 cm2 of
skin contains:
– 3,000,000 cells
– 10 hairs
– 15 sebaceous glands
– 3 feet of blood vessels
– 700 sweat glands
– 3000 sensory cells at
nerve endings
– 12 feet of nerves
• 200 pain receptors
• 2 cold receptors
• 12 sensors for heat
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Functions of the Skin
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Serves as mechanical barrier
Protects internal structures
Participates in the immune response
Acts as a gland for vitamin D synthesis
Performs excretory function
Performs sensory role
Helps regulate body temperature
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Structure of the Skin
• Layers
– Epidermis
• (lays upon dermis)
– Dermis (skin)
• Subcutaneous
• a.k.a: Hypodermis
• Accessory
structures
• Hair, nails,
glands..etc.
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Overview Structure of the Skin
Skin classified as cutaneous membrane
Two primary layers—epidermis and dermis;
joined by dermoepidermal junction
Hypodermis lies beneath dermis
Thin and thick skin (Figure 7-3)
“Thin skin” —covers most of body surface (1 to 3
mm thick); has hair and smooth surface
 “Thick skin”—soles and palms (4 to 5 mm thick);
ridged surface with no hair
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Layers of Epidermis
From Superfical to deep:
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1. Stratum Corneum
2. Stratum Lucidum**
3. Stratum Granulosum
4. Stratum Spinosum
5. Stratum Germinativum
• A.k.a Stratum Basale
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Layers uncovered
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Epidermis: Outer Layer continued…
• Layers of the epidermis
– Stratum corneum (surface layer); composed of
dead, flattened cells that slough off , our horns
– Stratum germinativum (deepest), a.k.a. stratum
basale: cells continuously dividing and moving
toward surface
• Keratinization: The protein keratin makes skin
cells hard, flat, and water resistant.
• (Keratinocytes…cells that actually produce
protein)
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Epidermal growth and repair
• Shortened turnover time increase thickness of
the stratum corneum; results in callus
formation
• Normally 10% to 12% of all cells in stratum
basale enter mitosis daily
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Structure of the Skin
Dermopidermal junction (DEJ)
 A basement membrane
 Polysaccharide gel serve to “glue” the
epidermis to the dermis below
 Partial barrier to the passage of some
cells and large molecules
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Dermis
• Our “hide”, strong and stretchy
– “true skin”
• Lies under and supports the epidermis
– Gives strength
• Sits on the subcutaneous layer or hypodermis
• Embedded with accessory structures
– Includes blood vessels that nourish epidermis
– Reservoir storage for water and electrolytes
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Dermis continued…
• 2 major regions:
– Papillary: upper/superficial dermal layer
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Pain receptors (free nerve endings)
Touch receptors: Meissner’s corpuscles
Allow for grip
Genetically unique= fingerprints
Arrector pili (goose bumps)
– Reticular: Deepest of skin layer
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Blood vessel, sweat glands, oil glands
Pacinian corpuscles: Deep pressure receptors
Last line of defense
Leather
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Dermis (cont)
During wound healing
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fibroblasts begin forming an unusually
dense mass of new connective fibers
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if not replaced by normal tissue, this
mass remains a scar
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Cleavage lines (Figure 7-7)—patterns
formed by the collagenous fibers of the
reticular layer of the dermis
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also called Langer’s lines
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Langer’s lines
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Scar formation
• Cleavage lines - patterns formed by the
collagenous fibers of the reticular layer of the
dermis
– also called Langer’s lines
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Subcutaneous Layer: Hypodermis
• A.k.a = subcutaneous layer
• Connection point to tissue that lies beneath
skin
• Highly vascularized
• Two main roles:
– Its fat insulates body from extreme temperature
changes.
– Its connective tissue anchors the skin to
underlying structures.
• NOT PART OF THE SKIN
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Problems…
• Decubitus ulcers; Bed
sores
– Normal blood supply is
cut off
– Bedridden patients who
are not regularly moved
– Pressure of bone on skin
eventually cuts off
supply line
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Real life…
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Accessory Structures: Hair
• Functions: Detect
insects, protect eyes,
keep dust out of lungs
• Hormones affect
growth.
• Melanin influences
color.
• Hair arises in epidermis.
• Cosmetic role
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Accessory Structures: Nails
• Protect tips of fingers and toes from injury
• Condition affected by oxygenation of blood
supply, trauma, and nutritional deficiencies
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Accessory Structures: Glands
• Sebaceous glands:
– Oil glands
– Secrete sebum and in
fetus vernix caseosa
• Sudoriferous
– Sweat glands
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Sudoriferous Glands
• Apocrine glands: Usually associated with hair
follicles; more active at puberty
• Eccrine glands: Critical for temperature
regulation
• Types of modified sweat glands:
– Mammary glands: Secrete milk
– Ceruminous glands: Secrete ear wax (cerumen)
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Skin Color
• Determined by genes, physiology, and
sometimes pathology
• Dark pigment: Melanin
– Secreted by melanocytes in the epidermis
– Melanocyte malfunctions: Albinism, vitiligo, moles
• Yellow pigment: Carotene
– Presence of melanin overshadows carotene’s tint
in most people
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Skin Color (cont’d.)
• Physiological changes:
– Blushing: Blood vessel dilation
– Pallor: Blood vessel constriction
• Pathological changes:
– Cyanosis or bluish tint: Poor oxygenation
– Jaundice or yellowing: Bilirubin deposition
– Bronzing: Melanin overproduction
– Ecchymosis: Black and blue bruising
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Lesson 7-2 Objectives
• Explain four processes by which the
body loses heat.
• Describe how the skin helps
regulate temperature.
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Skin, Drugs, and Chemicals
• Skin can absorb many chemicals.
• Drug delivery systems:
• Hypodermic injections
• Transdermal patches
• Intradermal injections (allergy testing)
• Topical applications
• Danger of absorption of toxins
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Body Temperature: Key Terms
• Core temperature: The inner parts of the body
• Shell temperature: The surface areas of the
body
• Thermoregulation: Balance of heat production
and heat loss
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Heat Production
• Metabolism: basis of body temperature
• Blood disperses heat throughout the body.
• Most heat is produced by muscles, the liver,
and endocrine glands.
• Affected by food consumption, hormones,
disease, and physical activity
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Heat Loss
• Sites: Skin (80%), lungs, and excretory
products (20%)
• Types:
– Radiation
– Conduction
– Convection
– Evaporation
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Temperature Regulation
• Hypothalamus
– Heat lost by:
• Dilation of blood
vessels
• Sweating
– Heat conserved by
• Shivering
• Blood vessel
constriction
• Less sweat
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Temperature Regulation: Neonates
• Lose more heat than they produce
– Large surface area
– Large bald head
– Less insulation
– Must rely on nonshivering thermogenesis:
metabolism of brown adipose tissue (BAT)
• Have limited capacity to dissipate heat
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Issues in Temperature Regulation
• Hyperthermia: Syncope, cramps, heat
exhaustion, heat stroke
• Hypothermia: Slowed metabolism, fibrillation
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Burns: Classified by Depth
• Partial thickness
burns
– First-degree
– Second-degree
• Full-thickness burn
– Third-degree
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Burns: Classified by Extent
• “Rule of
nines”
• Eschar
– Acts like a
tourniquet
– Breeds
bacteria
– Secretes
toxins
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Skin Care
• All ages:
– Reduce exposure to UV radiation.
• Especially in older adults:
– Skin dries out more easily; retain moisture by
limiting excessive bathing and use of soap.
– Thinner skin bruises more easily and does not
insulate as well.
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