Download Essentials of Human Anatomy

Essentials of Human Anatomy
Skin and Body Membranes
Chapter 4
Dr Fadel Naim
Ass. Prof. Faculty of Medicine
IUG
1
Body Membranes
• Thin tissue layers that cover surfaces, line
cavities, and divide spaces or organs
• Epithelial membranes are most common type
– Cutaneous membrane (skin)
• Primary organ of integumentary system
• One of the most important organs
• Composes approximately 16% of body weight
– Serous membrane (serosa)
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Parietal membranes—line closed body cavities
Visceral membranes—cover visceral organs
Pleura—surrounds a lung and lines the thoracic cavity
Peritoneum—covers the abdominal viscera and lines the
abdominal cavity
Slide 2
Body Membranes
• Mucous membrane (mucosa)
– Lines and protects organs that open to the exterior of the body
– Found lining ducts and passageways of respiratory, digestive, other
tracts
– Lamina propria—fibrous connective tissue underlying mucous
epithelium
– Mucus is made up mostly of water and mucins—proteoglycans that
form a double-layer protection against environmental microbes
• Connective tissue membranes
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Do not contain epithelial components
Synovial membranes—line the spaces between bone in joints
Have smooth and slick membranes that secrete synovial fluid
Help reduce friction between opposing surfaces in a moveable joint
Synovial membranes also line bursae
Slide 3
Ventral Body Cavity Membranes
• Parietal serosa lines internal body walls
• Visceral serosa covers the internal organs
• Serous fluid separates the serosae
Serous Membranes
Anatomy of Skin
• Skin (integument) is body’s largest organ
• Approximately 1.6 to 1.9 m2 in average-sized
adult
• Integumentary system describes the skin
and its appendages—the hair, nails, and
skin glands
• Thin and thick skin
– “Thin skin”—covers most of body surface
(1 to 3 mm thick)
– “Thick skin”—soles and palms
(4 to 5 mm thick)
Slide 6
Functions of Skin
Function of Integumentary System
A. Regulation of Body Temperature
B. Protection from Dehydration and Infection
C. Respond to Temperature, Pressure, Pain
D. Excretion of Water, Salts, Urea (nitrogenous waste)
E. Synthesis Vitamin D (essential for Ca + P absorption)
F. First Defensive Barrier of Immune Response
Functions of the Skin
• Protection
– Physical barrier to microorganisms
– Barrier to chemical hazards
– Reduces potential for mechanical trauma
– Prevents dehydration
– Protects (via melanin) excess UV exposure
Slide 8
Functions of the Skin
• Sensation
– Skin acts as a sophisticated sense organ
– Somatic sensory receptors detect stimuli that
permit us to detect pressure, touch,
temperature, pain, and other general
sensations
Slide 9
Functions of the Skin
• Flexibility
– Skin is supple and elastic, thus permitting
change in body contours without injury
• Excretion
– Water
– Urea/ammonia/uric acid
Slide 10
Functions of the Skin
• Hormone (Vitamin D) production
– Exposure of skin to UV light converts
7-dehydrocholesterol to cholecalciferol—
a precursor to vitamin D
– Blood transports precursor to liver and
kidneys, where vitamin D is produced
– Process and end result fulfill the necessary
steps required for vitamin D to be classified as
a hormone
Slide 11
Functions of the Skin
• Immunity
– Phagocytic cells destroy bacteria
– Langerhans cells trigger helpful immune
reaction working with “helper T cells”
Slide 12
Functions of the Skin
– Heat loss
• approximately 80% of heat loss occurs through the
skin; remaining 20% occurs through the mucosa of
the respiratory, digestive, and urinary tracts
Slide 13
Layers of Skin
• Epidermis
• Dermis
• Subcutaneous layer
• beneath dermis
• not part of skin
Epidermis
• Lacks blood vessels
• Keratinized
• Thickest on palms and soles (0.8-1.4mm)
• Melanocytes provide melanin
• Rests on basement membrane
• Stratified squamous
Epidermis
Layers of Epidermis
• stratum corneum
• stratum lucidum
• stratum granulosum
• stratum spinosum
• stratum basale
Structure of the Skin
• Epidermis
– Cell types
• Keratinocytes— constitute over 90% of cells present;
principal structural element of the outer skin
• Melanocytes— pigment-producing cells (5% of the total);
contribute to skin color; filter ultraviolet light
• Langerhans cells— dendritic (branched) antigen-presenting
cells (APCs), they play a role in immune response
Slide 17
Structure of the Skin
• Epidermis
– Cell layers
• Stratum germinativum (growth layer)—
describes the stratum spinosum and stratum
basale together
– Stratum basale (base layer)—single layer of
columnar cells; only these cells undergo mitosis, then
migrate through the other layers until they
are shed
– Stratum spinosum (spiny layer)—cells arranged in 8
to 10 layers with desmosomes that pull cells into spiny
shapes; cells rich in RNA
Slide 18
Structure of the Skin
– Cell layers
• Stratum granulosum (granular layer)—cells
arranged in two to four layers and filled with
keratohyalin granules; contain high levels of
lysosomal enzymes
• Stratum lucidum (clear layer)—cells filled with
keratin precursor called eleidin; absent in thin skin
• Stratum corneum (horny layer)—most superficial
layer; dead cells filled with keratin (barrier area)
Slide 19
Structure of the Skin
– Epidermal growth and repair
• Turnover or regeneration time refers to time required for
epidermal cells to form in the stratum basale and migrate
to the skin surface—about 35 days
• Shortened turnover time will increase the thickness of the
stratum corneum and result in callus formation
• Normally 10% to 12% of all cells in stratum basale enter
mitosis daily
• Each group of 8 to 10 basal cells in mitosis with their
vertical columns of migrating keratinocytes is called an
epidermal proliferating unit, or EPU
Slide 20
Structure of the Skin
• Dermal-epidermal junction
– A definite basement membrane,
specialized fibrous elements, and a
polysaccharide gel serve to “glue” the
epidermis to the dermis below
– The junction serves as a partial barrier to
the passage of some cells and large
molecules
Slide 21
Structure of the Skin
• Dermis
– Sometimes called “true skin”—much thicker
than the epidermis and lies beneath it
– Gives strength to the skin
– Serves as a reservoir area for storage of
water and electrolytes
Slide 22
Dermis
• On average 1.0-2.0mm thick
• Contains dermal papillae
• Binds epidermis to underlying tissues
• Irregular dense connective tissue
• Muscle cells
• Nerve cell processes
• Specialized sensory receptors
• Blood vessels
• Hair follicles
• Glands
Structure of the Skin
• Dermis
– Contains various structures:
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Arrector pili muscles and hair follicles
Sensory receptors
Sweat and sebaceous glands
Blood vessels
– Rich vascular supply plays a critical role in
temperature regulation
Slide 24
Structure of the Skin
• Dermis
– Layers of dermis:
• Papillary layer— composed of dermal papillae
that project into the epidermis; contains fine
collagenous and elastic fibers; contains the
dermal-epidermal junction; forms a unique pattern
that gives individual fingerprints
• Reticular layer— contains dense, interlacing white
collagenous fibers and elastic fibers to make the
skin tough yet stretchable; when processed from
animal skin, produces leather
Slide 25
Lines of Cleavage
• Tension lines in the skin identify the predominant
orientation of collagen fiber bundles.
• Clinically and surgically significant because cuts
can result in slow healing and increased
scarring.
Structure of the Skin
• Dermis remains a scar
• Dermal growth and repair
• The dermis does not continually shed and regenerate itself
as does the epidermis
• During wound healing, the fibroblasts begin forming an
unusually dense mass of new connective fibers; if not
replaced by normal tissue, this mass by the collagenous
fibers of the reticular layer of the dermis; also called Langer’s
lines
Slide 28
Subcutaneous Layer
• hypodermis
• loose connective tissue
• adipose tissue
• insulates
• major blood vessels
Structure of the Skin
• Hypodermis
– Also called subcutaneous layer or superficial
fascia
– Deep to the dermis, forming connection
between the skin and other structures
– Not part of the skin
Slide 30
Slide 31
Skin Color
Genetic Factors
Physiological Factors
• varying amounts of
• dilation of dermal blood
melanin
vessels
• varying size of melanin
• constriction of dermal blood
granules
vessels
• albinos lack melanin
• accumulation of carotene
• jaundice
Environmental Factors
• sunlight
• UV light from sunlamps
• X rays
• darkens melanin
Skin Color
– Melanin
• Basic determinant of skin color is quantity, type, and
distribution of melanin
– Beta carotene
• (group of yellowish pigments from food) can also
contribute to skin color
– Hemoglobin
• color changes also occur as a result of changes in blood
flow
– Redder skin color when blood flow to skin increases
– Cyanosis—bluish color caused by darkening of
hemoglobin when it loses oxygen and gains carbon
dioxide (Figure 6-9)
– Bruising can cause a rainbow of different colors to
appear in the skin
Slide 33
Basis of Skin Color
• The color of skin and mucous membranes
can provide clues for diagnosing certain
problems, such as
– Jaundice
• yellowish color to skin and whites of eyes
• buildup of yellow bilirubin in blood from liver disease
– Cyanosis
• bluish color to nail beds and skin
• hemoglobin depleted of oxygen looks purple-blue
– Erythema
• redness of skin due to enlargement of capillaries in
dermis
• during inflammation, infection, allergy or burns
Slide 34
Skin glands
Sebaceous glands
• Secrete sebum—oily substance that keeps hair
and skin soft and pliant; prevents excessive water
loss from the skin
• usually associated with hair follicles
• Lipid components have antifungal activity
• Simple, branched glands
• Found in dermis except in palms and soles
• Secretion increases in adolescence; may lead to
formation of pimples and blackheads
Slide 35
Sweat Glands
• Widespread in skin
• Originates in deeper dermis
Or hypodermis
• Eccrine glands
• Apocrine glands
• Ceruminous glands
• Mammary glands
Sweat glands
• Eccrine glands
–Most numerous sweat glands; quite
small
–Distributed over total body surface with
exception of a few small areas
–Simple, coiled, tubular glands
–Function throughout life
–Secrete perspiration or sweat; eliminate
wastes; and help maintain a constant
core temperature
Slide 37
Sweat glands
• Apocrine glands
–Located deep in subcutaneous layer
–Limited distribution—axilla, areola of breast,
and around anus
–Large (often more than 5 mm in diameter)
–Simple, branched, tubular glands
–Begin to function at puberty
–Secretion shows cyclic changes in female
with menstrual cycle
Slide 38
Sweat glands
Ceruminous glands
• Modified apocrine sweat glands
• Simple, coiled, tubular glands
• Empty contents into external ear canal alone or with
sebaceous glands
• Mixed secretions of sebaceous and ceruminous glands
called cerumen (wax)
• Function of cerumen to protect area from dehydration;
excess secretion can cause blockage of ear canal and
loss of hearing
Slide 39
Hair
• Distribution—over entire body except
palms of hands and soles of feet and a
few other small areas
• Fine and soft hair coat present before birth called
lanugo
• Coarse pubic and axillary hair that develops at
puberty called terminal hair
Slide 40
Functions of Hair
• Protection
• Heat retention
• Prevents the loss of conducted heat from the
scalp to the surrounding air
• Facial expression
• Sensory reception
• Visual identification
• Chemical signal dispersal
Hair Follicles
• Epidermal cells
• Tube-like depression
• Extends into dermis
• Hair root
• Hair shaft
• Hair papilla
• Dead epidermal cells
• Melanin
• Arrector pili muscle
A. Shaft - projects above surface of
epidermis
1. medulla - polyhedral cells with eleidin
2. cortex - elongated cells with/out
pigment
3. cuticle - outermost layer, like shingles
on roof
B. Root - below epidermis, penetrates
into the dermis
C. Hair Follicle - at the base a a single
hair
1.
external root sheath - basale and
spinosum extension
2.
internal root sheath - internal hair
cell layers
3.
bulb - base of hair cell
4.
papilla - in the bulb, provides
nourishment for hair
5.
matrix - origin of new hair cells
D. arrector pili - smooth muscle, cause
hair to rise
nerve bundle responds to touch
E. hair root plexuses
Slide 44
Slide 45
Slide 46
Appearance of hair
• Color
– result of different amounts, distribution, types of melanin in
cortex of hair
• Growth
– hair growth and rest periods alternate; hair on head averages 5
inches of growth per year
• Sebaceous glands
– attach to and secrete sebum
(skin oil) into follicle
• Male pattern baldness results from combination of genetic
tendency and male sex hormones
Slide 47
Hair Thinning and Baldness
• Alopecia – hair thinning in both sexes
• True, or frank, baldness
– Genetically determined and sex-influenced
condition
Nails
– Consist of epidermal cells converted to hard
keratin
– Nail body—visible part of each nail
– Root—part of nail in groove hidden by fold of
skin, the cuticle
– Lunula—moon-shaped white area nearest
root
Slide 49
• Nail bed—layer of epithelium under nail body
– contains abundant blood vessels
• Appears pink under translucent nails
• Growth—nails grow by mitosis of cells in stratum germinativum
beneath the lunula; average growth about 0.5 mm per week, or
slightly over 1 inch per year
Slide 50
Burns
• Tissue damage from excessive heat, electricity, radioactivity,
or corrosive chemicals that destroys (denatures) proteins in
the exposed cells is called a burn.
• Generally, the systemic effects of a burn are a greater threat
to life than are the local effects.
• The seriousness of a burn is determined by
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Its depth
Extent
Area involved
The person’s age and general health.
• When the burn area exceeds 70%, over half of the victims die
Slide 51
Burns
• Destruction of proteins of the skin
– chemicals, electricity, heat
• Problems that result
– shock due to water, plasma and plasma
protein loss
– circulatory & kidney problems from loss of
plasma
– bacterial infection
Slide 52
Types of Burns
• First-degree
– only epidermis (sunburn)
Slide 53
Types of Burns
• Second-degree burn
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–
–
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destroys entire epidermis & part of dermis
fluid-filled blisters separate epidermis & dermis
epidermal derivatives are not damaged
heals without grafting in 3 to 4 weeks & may scar
Slide 54
Types of Burns
• Third-degree or full-thickness
– destroy epidermis, dermis & epidermal derivatives
– damaged area is numb due to loss of sensory nerves
Slide 55
Rule of Nines
Cycle of Life: Skin
• Children
– Skin is smooth, unwrinkled, and characterized
by elasticity and flexibility
– Few sweat glands
– Rapid healing
Slide 57
Cycle of Life: Skin
• Adults
– Development and activation of sebaceous
and sweat glands
– Increased sweat production
• Body odor
– Increased sebum production
• Acne
Slide 58
Cycle of Life: Skin
Aging
• Skin repair processes take longer due to
reduced number and activity of stem cells.
• Skin forms wrinkles and becomes less resilient.
• Skin’s immune responsiveness is diminished.
• Skin becomes drier due to decreased
sebaceous gland activity.
• Altered skin and hair pigmentation.
Cycle of Life: Skin
Aging
• Sweat production diminishes.
• Blood supply to the dermis is reduced
leading to impaired thermoregulation.
• Hair thinning and loss.
• Integumentary production of vitamin D3
diminishes.
• Development of skin cancers.
Skin and Aging Process
Skin Cancer
• The most common type of cancer.
• The greatest risk factor is exposure to UV
rays of the sun.
• The highest incidence is in people who
have had severe sunburns, especially as
children.
Skin Cancer
• Most skin tumors are benign and do not
metastasize
• The three major types of skin cancer are:
– Basal cell carcinoma
– Squamous cell carcinoma
– Melanoma
Basal Cell Carcinoma
• Least malignant and most common skin
cancer
• Stratum basale cells proliferate and invade
the dermis and hypodermis
• Slow growing and do not often
metastasize
• Can be cured by surgical excision in 99%
of the cases
Squamous Cell Carcinoma
• Arises from keratinocytes of stratum
spinosum
• Arise most often on scalp, ears, and lower
lip
• Grows rapidly and metastasizes if not
removed
• Prognosis is good if treated by radiation
therapy or removed surgically
Melanoma
Cancer of melanocytes is the most dangerous type
of skin cancer because it is:
– Highly metastatic
– Resistant to chemotherapy
Melanoma
Melanomas have these characteristics
(ABCD rule)
– A: Asymmetry; the two sides of the
pigmented area do not match
– B: Border is irregular and exhibits
indentations
– C: Color (pigmented area) is black, brown,
tan, and sometimes red or blue
– D: Diameter is larger than 6 mm (size of a
pencil eraser)
Melanoma
• Treated by wide surgical excision
accompanied by immunotherapy
• Chance of survival is poor if the lesion is
over 4 mm thick
THE END