01 ch5 integmentery system.pptxsssssssssssssssss

Ch5 The Integumentary System
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The integumentary system and homeostasis
The integumentary system contributes to homeostasis by protecting
the body and helping regulate body temperature. It also allows you
to sense pleasurable, painful, and other stimuli in your external
environment.

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The integumentary system is composed of:
the skin, hair, oil and sweat glands, nails, and sensory
receptors. Represented in:
• Cutaneous membrane (skin)
• Accessory structures
The integument is the largest system of the human body
It forms:
- 16% of body weight
- 1.5 to 2 m2
in area

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Dermatology : Is the medical specialty that deals with the
structure, function, and disorders of the integumentary system.
Dermatologist is the doctor that treats skin disorders.

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The integumentary system functions to:
(Also see 5.4 Functions of the Skin)
1. Maintains the body’s integrity/ Protection
2. Maintains temperature / Thermoregulation
3. Converts inactive vitamin D to its active form/ Synthesis of Vitamin D
4. Provides sensory information / Cutaneous Sensations
5. Maintains homeostasis/ Blood Reservoir, Excretion and Absorption

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Because of its visibility,
skin reflects our emotions (frowning, blushing) and some aspects
of normal physiology (such as sweating).
Changes in skin color may also indicate homeostatic imbalances in
the body.
For example,the bluish skin color associated with hypoxia (oxygen
deficiency at the tissue level) is one sign of heart failure as well as
other disorders.
Abnormal skin eruptions or rashes such as chickenpox, cold
sores, or measles may reveal systemic infections or diseases of
internal organs, while other conditions, such as warts, age spots, or
pimples, may involve the skin alone.

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5.1 Structure of the Skin
O B J E C T I V E S
• Describe the layers of the epidermis and the cells that
compose them.
• Compare the composition of the papillary and reticular
regions of the dermis.
• Explain the basis for different skin colors.

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Structures of the Skin
• The skin(cutaneous membrane) has 2 major
layers:
1. Outer is called the epidermis
 Superficial epithelium (epithelial tissues)
2. Inner is called the dermis
 Connective tissues
The subcutaneous layer (also called the hypodermis)
is located underneath the dermis, it connects the
dermis to the underlying tissue and its not part of
the skin.

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• The subcutaneous layer or hypodermis
– Lies below the integument
– Stabilizes the skin
– Allows separate movement
– Is made of elastic areolar and adipose tissues
– Is connected to the reticular layer of integument by
connective tissue fibers
– Has few capillaries and no vital organs
– Is the site of subcutaneous injections using
hypodermic needles

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• Deposits of subcutaneous fat
– Have distribution patterns determined by
hormones
– Are reduced by cosmetic liposuction
(lipoplasty)

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Epidermis
• The superficial thinner portion, which is
composed of epithelial tissue.
• Avascular
• The epidermis is composed of keratinized
stratified squamous epithelium.

The Epidermis
Contains four major
types of cells:
 Keratinocytes
 Melanocytes
 Intraepidermal
macrophages
 Tactile epithelial cells

- Keratinocytes produce keratin a tough fibrous protein that provides
protection. 90 % Keratinocytes also produce lamellar granules,
which release a water-repellent sealant that decreases water entry
and loss and inhibits the entry of foreign materials.
- Melanocytes produce the pigment melanin 8 %
- Intraepidermal macrophages are involved in the immune responses.
Langerhans cell. Their role in the immune response is to help other
cells of the immune system recognize an invading microbe and
destroy it.
- Tactile epithelial cells function in the sensation of touch.(merkel cell )
The Epidermis

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The Epidermis
• The epidermis is composed of four layers in thin
skin, and five layers in thick skin. They are (from
deep to superficial):
– The stratum basale
– The stratum spinosum
– The stratum granulosum
– The stratum lucidum (only present in thick skin)
– The stratum corneum

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Stratum Basale
The deepest layer of the epidermis is the stratum basale ( basal= base),
composed of a single row of cuboidal or columnar keratinocytes. Some
cells in this layer are stem cells that undergo cell division to continually
produce new keratinocytes.
The cytoskeleton within keratinocytes of the stratum basale includes
scattered intermediate filaments, called keratin intermediate filaments
(tonofilaments).
Keratin intermediate filaments attach to desmosomes, which bind cells of
the stratum basale to each other and to the cells of the adjacent stratum
spinosum, and to hemidesmosomes, which bind the keratinocytes to the
basement membrane positioned between the epidermis and the dermis.
Melanocytes and Merkel cells with their associated Merkel discs are
scattered among the keratinocytes of the basal layer. The stratum basale
is also known as the stratum germinativum

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Stratum Spinosum
• Superficial to the stratum basale
• This stratum mainly consists of numerous keratinocytes
arranged in 8–10 layers.
• Cells in the more superficial layers become somewhat
flattened.
• At each spine like projection, bundles of keratin
intermediate filaments insert into desmosomes, which
tightly join the cells to one another. This arrangement
provides both strength and flexibility to the skin
• Langerhans cells and projections of melanocytes are also
present in the stratum spinosum

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Stratum Granulosum
• consists of three to five layers of flattened keratinocytes that
are undergoing apoptosis. nuclei and other organelles of
these cells begin to degenerate as they move farther from
their source of nutrition (the dermal blood vessels).
• A distinctive feature of cells in this layer is the presence of
darkly staining granules of a protein called keratohyalin
• Also present in the keratinocytes are membrane-enclosed
lamellar granules , which fuse with the plasma membrane
and release a lipid-rich secretion.

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Stratum Lucidum
• The stratum lucidum (LOO-si-dum; lucid- clear) is
present only in the thick skin of areas such as the
fingertips, palms, and soles.
• It consists of four to six layers of flattened clear, dead
keratinocytes that contain large amounts of keratin and
thickened plasma membranes.
• This probably provides an additional level of toughness
in this region of thick skin.

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Stratum Corneum
Consist on average of 25 to 30 layers of flattened dead
keratinocytes, but can range in thickness from a few
cells in thin skin to 50 or more cell layers in thick skin.
Constant exposure of skin to friction stimulates increased
cell production and keratin production that results in the
formation of a callus, an abnormal thickening of the
stratum corneum.

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Keratinization and Growth of the Epidermis
• Newly formed cells in the stratum basale are slowly pushed
to the surface. As the cells move from one epidermal layer to
the next, they accumulate more and more keratin, a process
called keratinization .
• Then they undergo apoptosis.
• Eventually the keratinized cells slough off and are replaced
by underlying cells that in turn become keratinized.
• The whole process by which cells form in the stratum basale,
rise to the surface, become keratinized, and slough off takes
about four to six weeks in an average epidermis of 0.1 mm.
• An excessive amount of keratinized cells shed from the skin of
the scalp is called dandruff.

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The Dermis
• The few cells present in the dermis include predominantly
fibroblasts, with some macrophages, and a few adipocytes
near its boundary with the subcutaneous layer.
• Blood vessels, nerves, glands, and hair follicles (epithelial
invaginations of the epidermis) are embedded in the
dermal layer.
• Based on its tissue structure, the dermis can be divided
into a thin superficial papillary region and a thick deeper
reticular region.

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papillary region
• Makes up about one-fifth of the thickness of the total layer.
• It consists of thin collagen and fine elastic fibers.
• Its surface area is greatly increased by dermal papillae which is
small, nipple-shaped structures that project into the undersurface of
the epidermis.
• All dermal papillae contain capillary loops (blood vessels). Some
also contain tactile receptors called Meissner corpuscles or
corpuscles of touch, nerve endings that are sensitive to touch.
• Still other dermal papillae also contain free nerve endings,
dendrites that lack any apparent structural specialization.
• Different free nerve endings initiate signals that give rise to
sensations of warmth, coolness, pain, tickling, and itching.

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The reticular region (reticul- netlike)
Which is attached to the subcutaneous layer, consists of bundles of
thick collagen fibers, scattered fibroblasts, and macrophages).
Some adipose cells can be present in the deepest part of the layer, along
with some coarse elastic fibers .
The collagen fibers in the reticular region are arranged in a netlike
manner and have a more regular arrangement than those in the
papillary region.
The more regular orientation of the large collagen fibers helps the skin
resist stretching.
Blood vessels, nerves, hair follicles, sebaceous (oil) glands, and
sudoriferous (sweat) glands occupy the spaces between fibers.

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The Structural Basis of Skin Color
 Melanin, hemoglobin, and carotene are three pigments that impart a wide
variety of colors to skin.
 Because the number of melanocytes is about the same in all people,
differences in skin color are due mainly to the amount of pigment the
melanocytes produce and transfer to keratinocytes.
 A round, flat, or raised area that represents a benign localized overgrowth
of melanocytes and usually develops in childhood or adolescence is called
a nevus or a mole.
 Melanocytes synthesize melanin from the amino acid tyrosine in the
presence of an enzyme called tyrosinase.
 Synthesis occurs in an organelle called a melanosome .
 Exposure to ultraviolet (UV) light increases the enzymatic activity within
melanosomes and thus increases melanin production.

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• Dark-skinned individuals have large amounts of melanin in the
epidermis, so their skin color ranges from yellow to reddish brown to
black.
• Light-skinned individuals have little melanin in the epidermis.
• Thus, the epidermis appears translucent, and skin color ranges from
pink to red depending on the oxygen content of the blood moving
through capillaries in the dermis.
• The red color is due to hemoglobin .
• Carotene (carrot) is a yellow-orange pigment that gives egg yolks and
carrots their color.
• This precursor of vitamin A, which is used to synthesize pigments
needed for vision, is stored in the stratum corneum and fatty areas of
the dermis and subcutaneous layer in response to excessive dietary
intake.
• In fact, so much carotene may be deposited in the skin after eating
large amounts of carotene-rich foods that the skin actually turns
orange, which is especially apparent in light-skinned individuals.

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5.2 Accessory Structures of the Skin
O B J E C T I V E
• Contrast the structure, distribution, and functions of
hair, skin glands, and nails.
Accessory structures of the skin—hair, skin glands,
and nails— develop from the embryonic epidermis.
They have a host of important functions.
For example, hair and nails protect the body, and sweat
glands help regulate body temperature.

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• Hair, hair follicles, sebaceous glands,
sweat glands, and nails
– Are integumentary accessory structures
– Are located in dermis
– Project through the skin surface

Hair
Composed of dead, keratinized epidermal cells.
Genetics determines thickness and distribution.
• The human body is covered with hair, except
– Palms
– Soles
– Lips
– Portions of external genitalia
• Functions of Hair
– Protects and insulates
– Guards openings against particles and insects
– Is sensitive to very light touch

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Hair
• The parts of a hair include:
– The shaft (above the skin
surface)
– The follicle (below the level
of the skin)
– A root that penetrates into
the dermis includes:
• An epithelial root sheath
• A dermal root sheath

Anatomy of a Hair
 Each hair is composed of columns of dead, keratinized epidermal
cells bonded together by extracellular proteins.
 The shaft is the superficial portion of the hair, which projects above
the surface of the skin .
 The root is the portion of the hair deep to the shaft that penetrates
into the dermis, and sometimes into the subcutaneous layer.
 The shaft and root of the hair both consist of three concentric
layers of cells: medulla, cortex, and cuticle of the hair .
 The inner medulla, which may be lacking in thinner hair, is
composed of two or three rows of irregularly shaped cells that
contain large amounts of pigment granules in dark hair, small
amounts of pigment granules in gray hair, and a lack of pigment
granules and the presence of air bubbles in white hair.
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• The middle cortex forms the major part of the
shaft and consists of elongated cells.
• The cuticle of the hair, the outermost layer,
consists of a single layer of thin, flat cells that
are the most heavily keratinized.
• Cuticle cells on the shaft are arranged like
shingles on the side of a house, with their free
edges pointing toward the end of the hair.

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• Surrounding the root of the hair is the hair follicle which
is made up of an external root sheath and an internal root
sheath, together referred to as an epithelial root sheath .
• The external root sheath is a downward continuation of
the epidermis.
• The internal root sheath is produced by the matrix
(described shortly) and forms a cellular tubular sheath of
epithelium between the external root sheath and the hair.
• The dense dermis surrounding the hair follicle is called
the dermal root sheath.

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• The base of each hair follicle and its surrounding dermal root
sheath is an onion-shaped structure, the bulb .
• This structure houses a nipple-shaped indentation, the papilla of
the hair, which contains areolar connective tissue and many
blood vessels that nourish the growing hair follicle.
• The bulb also contains a germinal layer of cells called the hair
matrix.
• The hair matrix cells arise from the stratum basale, the site of
cell division.
• Hence, hair matrix cells are responsible for the growth of
existing hairs, and they produce new hairs when old hairs are
shed.
• This replacement process occurs within the same follicle. Hair
matrix cells also give rise to the cells of the internal root sheath.

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• Sebaceous (oil) glands and a bundle of smooth
muscle cells are also associated with hairs .
• The smooth muscle is the arrector pili arrect- to
raise).
• It extends from the superficial dermis of the skin to
the dermal root sheath around the side of the hair
follicle.

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Hair Growth
Each hair follicle goes through a growth cycle, which
consists of :
 a growth stage,
 a regression stage, and
 a resting stage.

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Skin Glands
The skin contains 4 types of glands.
1. Sebaceous (oil) glands are connected to hair
follicles.
2. Eccrine sweat glands are the most numerous.
3. Apocrine sweat glands are located mainly in
hairy skin.
• Ceruminous glands are modified sweat
glands located in the ear canal.
produce a waxy lubricating
secretion.

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sebaceous glands or oil glands are simple, branched
acinar (rounded) glands. With few exceptions, they are connected
to hair follicles .
The secreting portion of a sebaceous gland lies in the dermis and
usually opens into the neck of a hair follicle.
In some locations, such as the lips, glans penis, labia minora, and
tarsal glands of the eyelids, sebaceous glands open directly onto
the surface of the skin.
Absent in the palms and soles, sebaceous glandsare small in most
areas of the trunk and limbs, but large in the skin of the breasts,
face, neck, and superior chest.

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• Sebaceous glands secrete an oily substance called
sebum , a mixture of triglycerides, cholesterol,
proteins, and inorganic salts.
• Sebum coats the surface of hairs and helps keep them
from drying and becoming brittle.
• Sebum also prevents excessive evaporation of water
from the skin, keeps the skin soft and pliable, and
inhibits the growth of some (but not all) bacteria.

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Sudoriferous Glands
 There are three million to four million sweat glands,
in the body.
 The cells of these glands release sweat, or
perspiration, into hair follicles or onto the skin
surface through pores.
 Sweat glands are divided into two main types, eccrine
and apocrine, based on their structure and type of
secretion.

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Eccrine sweat glands (EK-rin; eccrine secreting
outwardly) are simple, coiled tubular glands that are much
more common than apocrine sweat glands they are
distributed throughout the skin of most regions of the
body, especially in the skin of the forehead, palms, and
soles.
Eccrine sweat glands are not present, however, in the
margins of the lips, nail beds of the fingers and toes, glans
penis, glans clitoris, labia minora, or eardrums.
The secretory portion of eccrine sweat glands is located
mostly in

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The deep dermis (sometimes in the upper subcutaneous
layer).
The excretory duct projects through the dermis and
epidermis and ends as a pore at the surface of the
epidermis .

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 Compared to eccrine sweat, apocrine sweat appears milky or
yellowish in color.
 Apocrine sweat contains the same components as eccrine sweat
plus lipids and proteins. Sweat secreted from apocrine sweat
glands is odorless. However, when apocrine sweat interacts with
bacteria on the surface of the skin, the bacteria metabolize its
components, causing apocrine sweat to have a musky odor that is
often referred to as body odor.
 Eccrine sweat glands start to function soon after birth, but
apocrine sweat glands do not begin to function until puberty.

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Nails
• Nails are plates of tightly packed, hard, dead, keratinized
epidermal cells that form a clear, solid covering over the
dorsal surfaces of the distal portions of the digits.
• Made of keratinized epidermal cells
• Nail structures include:
– Free edge
– Transparent nail body (plate)
with a whitish lunula at its
base
– Nail root embedded in a
fold of skin

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 The average growth in the length of fingernails is about 1 mm (0.04
in.) per week.
 The growth rate is somewhat slower in toenails.
 The longer the digit the faster the nail grows.
Nails have a variety of functions:
1. They protect the distal end of the digits.
2. They provide support and counterpressure to the palmar
surface of the fingers to enhance touch perception and manipulation.
3. They allow us to grasp and manipulate small objects, and they
can be used to scratch and groom the body in various ways.

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5.3 Types of Skin
Objective
• Compare structural and functional differences in thin
and thick skin.
1. Thin (hairy) skin and,
2. Thick (hairless) skin (see also section 5.1).

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5.5 Maintaining Homeostasis:
Skin Wound Healing
O B J E C T I V E
• Explain how epidermal wounds and deep wounds heal.

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Wound Healing
• Two kinds of wound-healing processes can
occur, depending on the depth of the injury.
– Epidermal wound healing occurs following
superficial wounds that affect only the epidermis.

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Wound Healing
– Deep wound healing occurs when an injury
extends to the dermis and subcutaneous layer.

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Development of the Integumentary System
• The epidermis develops from the ectoderm.
– Nails, hair, and skin glands are epidermal
derivatives.

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Development of the Integumentary System
• The dermis develops from the mesoderm.

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Aging
The integumentary system changes with age:
1. Wrinkles develop.
2. Dehydration and cracking occurs.
3. Sweat production decreases.
4. A decrease in the numbers of functional melanocytes
results in gray hair and atypical skin pigmentation.
5. Subcutaneous fat is lost, and there is a general
decrease in skin thickness.
6. Nails may also become more brittle.

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Aging
• With age, there is also an increased susceptibility
to pressure ulcers (“bed sores”).

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Skin Cancer
• Excessive exposure to
ultraviolet light (from the
sun or tanning salons) is
the most common cause
of skin cancer. The three
major types are basal cell
carcinoma, squamous cell
carcinoma and malignant
melanoma.

A burn is tissue damage caused by excessive
heat, electricity, radioactivity, or corrosive
chemicals that denature (break down) the
proteins in the skin cells.
Burns are graded according to their severity.
Burns

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Burns
• A first-degree burn
involves only the
epidermis (sunburn).

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Burns
• A second-degree
burn destroys the
epidermis and part
of the dermis
(blister).

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Burns
• A third-degree burn is a full-
thickness burn (destroys the
epidermis, dermis, and
subcutaneous layer).

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Burns
• The rule of nines is
used to estimate
the surface area of
an adult affected
by a burn.

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Sensory Receptors
• The skin contains different types of sensory
receptors found in different layers:
– Superficially
• Type I cutaneous mechanoreceptors, free nerve
endings, corpuscles of touch and hair root plexuses
– Deep
• Lamellated corpuscles

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‫الذاتي‬ ‫لالطالع‬ ‫التالية‬ ‫المادة‬
‫واستمتع‬ ‫اقرأ‬
‫الوظيفة‬ ‫او‬ ‫االمتحان‬ ‫في‬ ‫سؤال‬ ‫منها‬ ‫يأتي‬ ‫قد‬


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