Transcript Chapter 6 Skin and the Integumentary System

Chapter 6
Skin and the
Integumentary System
You will be able to: ACOS 5
 Identify anatomical structures and functions of the
integumentary system
 Identify accessory organs
 Recognize diseases and disorders of the integumentary
system (examples: decubitus ulcer, melanoma, psoriasis)
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Integumentary system: skin and its
accessory organ
Includes two distinct layers
1. epidermis—outer layer
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composed of stratified squamous epithelium
2. dermis—inner layer
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thicker than the epidermis
contains dense connective tissue consisting of
collagenous and elastic fibers, epithelial tissue,
smooth muscle tissue, nervous tissue, and blood
• A basement membrane anchors the epidermis to
the dermis and separates these two skin layers.
• Beneath the dermis are masses of loose
connective tissue and adipose tissues that bind
the skin to the underlying organs called the
subcutaneous layer (or hypodermis).
– This is beneath the skin and not a true layer of skin.
– It also serves as a shock absorber or insulator.
Epidermis
• Composed of five zones or strata
– stratum basale
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deepest cell layer
close to the dermis and is nourished by
dermal blood vessels
constantly undergoing cell division
– stratum spinosum
– stratum granulosum
Keratinization
• The older cells being pushed toward the
surface harden in a process called
keratinization.
• The cytoplasm fills with strands of tough,
fibrous, waterproof keratin protein.
• As a result, many layers of tough, tightly
packed cells accumulate in the outermost
areas, stratum lucidum and stratum
corneum.
– stratum lucidum
* found only on hands and soles of feet
– stratum corneum
* outermost layer
* 20 to 30 cell layers thick
* dead cells that form this layer eventually
are shed
Melanin
• pigment that ranges in color from yellow to
brown to black
• produced by special cells called melanocytes
found mostly in the stratum basale
• Freckles and moles are concentrated spots of
melanin.
• How do we tan?
• What happens when we receive excessive
exposure to the sun?
Skin Color
• Differences in skin color result from differences in the
amount of melanin that melanocytes produce and in the
distribution and size of the pigment granules.
• Skin color is mostly genetically determined—if genes
instruct melanocytes to produce abundant melanin, then
the skin is dark.
William Bryant Stafford—with
jaundice (sun tanning)
Dermis
• strong, stretchy envelope that helps hold
the body together (your “hide”)
• dense, fibrous connective tissue of the
dermis consists of two major regions
1. papillary layer—upper region
2. reticular layer—deepest skin layer
1. Papillary Layer
• dermal papillae—fingerlike projections from the
superior surface of the papillary layer that cause
it to be uneven; contain capillary loops, pain
receptors or touch receptors
• Meissner’s corpuscles—touch receptors
• Papillary patterns are genetically determined.
Fingerprints are unique, identifying films of
sweat caused by the ridges of the fingertips.
2. Reticular Layer
• contains blood vessels, sweat and oil glands,
and deep pressure receptors called Pacinian
corpuscles
• contains many phagocytes that act to prevent
bacteria that have gotten through the epidermis
from penetrating any deeper into the body
• contains collagen and elastic fibers
• abundantly supplied with blood vessels that play
a role in maintaining body temperature
• What are decubitus ulcers? Blue Box page 116
Skin Section
Subcutaneous Layer (Hypodermis)
• consists of loose connective tissue and
adipose tissue
• no sharp boundary between the dermis
and subcutaneous layer
• provides insulation, helping to conserve
body heat and impeding the entrance of
heat from the outside
Accessory Organs of the Skin—Nails
• scalelike modification of the epidermis
• has a free edge, a body (visible attached portion), and a
root (embedded in the skin)
• nail folds—skin folds that overlap the borders of the nails
• cuticle—thick proximal nail fold
• nail bed—stratum basale that extends beneath the nail
• nail matrix—thickened proximal area responsible for nail
growth
• lunula—region over the thickened nail matrix that
appears as a white crescent
Accessory Organs of the Skin—Hair
• millions scattered all over the body
• serves only a few functions—guarding the head from
bumps, shielding the eyes, and helping to keep foreign
objects out of the respiratory tract
• produced by a hair follicle
• parts of a hair:
1. medulla—central core
2. cortex—bulky layer that surrounds the core
3. cuticle—outermost layer that encloses the cortex;
formed by a single layer of cells that overlap one
another
Hair Follicle
• root—part of the hair enclosed in the follicle
• shaft—part of the hair projecting from the surface of the
scalp or skin
• hair bulb matrix—growth zone at the end of the follicle
where hair is formed by the division of stratum basale
epithelial cells
• arrector pili—small bands of smooth muscle cells that
connect each side of the hair follicle to the dermal tissue
Sebaceous (Oil) Glands
• found all over the skin expect palms of the
hands and soles of the feet
• ducts usually empty into a hair follicle but
some open directly to skin surface
• sebum—mixture of oily substances and
fragmented cells that acts as a lubricant to
keep skin soft and moist and prevent hair
from becoming too brittle
• sebum contains chemicals that kill bacteria
so it acts as a protectant
Sudoriferous (Sweat) Glands
• widely distributed in the skin—more than
2.5 million per person
• two types:
A. eccrine glands—far more numerous
and found all over the body; produce
sweat when hot
B. apocrine sweat glands—largely
confined to the axillary and genital areas
of the body; activated at puberty
Regulation of Body Temperature—page 120
Write and answer the following questions.
• What is the normal temperature of deep body
parts?
• What body part plays a key role in regulating
body temperature?
• How does the body react when the body
temperature rises?
• How does the body react when the body
temperature drops?
• Where does 80% of the body’s heat escape?
Healing of Wounds—pages 120-121
• inflammation: when a wound becomes red and
swollen due to fluids entering the damaged
tissues
• scab: blood clot and dried tissue fluids that cover
and protect underlying, damaged tissue
• scar: connective tissue that forms on the
surface of the skin of extensive wounds
• granulations: small, rounded masses consisting
of a new branch of a blood vessel and a cluster
of collagen-secreting fibroblasts