Transcript The Integumentary System

THE INTEGUMENTARY SYSTEM
Dr Idara
SUBTOPICS
• Skin (cutaneous membrane)
• Subcutaneous tissue below the skin
• Accessory Structures
• Sweat glands
• Sebaceous or oil glands
• Hair
• Nails
THE INTEGUMENTARY SYSTEM
• Integument is skin
• Skin and its appendages make up the integumentary
system
• A fatty layer (hypodermis) lies deep to it
• Two distinct regions
• Epidermis
• Dermis
FUNCTIONS OF SKIN
• Protection
• Cushions and insulates and is waterproof
• Protects from chemicals, heat, cold, bacteria
• Screens UV
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Synthesizes vitamin D with UV
Regulates body heat
Prevents unnecessary water loss
Sensory reception (nerve endings)
The melanocytes contain melanin, which absorbs UV radiation,
and also distributes the pigment to neighboring cells. Skin
exposed to sunlight becomes wrinkled and creased. Changes
seem to be due to disruption of collagen and elastin in dermis,
and loss of fibroblasts which make new proteins.
EPIDERMIS
• Avascular as it has no blood supply of its own
• Oxygen and nutrients diffuse from the underlying
dermis
• The epidermis is a keratinized stratified squamous
epithelium. Oxygen and nutrients diffuse from the
underlying dermis. Five structurally different layers can
be identified:
•
Layers (from deep to superficial)
• Stratum basale or germinativum – stem cells
or mitotic cells. Cells here are constantly
dividing and as new cells form, older ones are
pushed toward the skin surface.
• Stratum spinosum – Consist of prickle cells
that interlock to support the skin.
• Stratum granulosum - This layer initiates
Keratinization. This process starts the death of
epithelial cells ( cells that make up the skin)
• Stratum lucidum- This layer is made up of
translucent cells. This thick layer appears only in
frequently used areas used areas such as the
palms of the hands and the soles of the feet.
• Stratum corneum – horny layer (cells dead, many
layers thick). The cells here are filled with keratin
which keeps the skin elastic and protects
underlying cells from drying out.
• Four types of cells
• Keratinocytes – deepest, produce keratin (tough
fibrous protein)
• Melanocytes - make dark skin pigment melanin
• Merkel cells – associated with sensory nerve
endings for touch sensations
• Langerhans cells – macrophage-like dendritic cells,
which helps the immune system.
THE STRATUM BASALE
• is the deepest layer of the epidermis (closest to the dermis).
• It is found close to the dermal blood supply.
• It consists of a single layer of columnar or cuboidal cells which rest
on the basement membrane.
• Basal cells are the stem cells of the epidermis.
• Their mitotic activity replenishes the cells in more superficial layers
as these are eventually shed from the epidermis.
STRATUM CORNEUM
• cells are keratinized and form a layer that is about 30
cells thick.
• Closest to the surface of the epidermis,
• Cells are constantly shed from this part of the stratum
corneum. This layer makes up three fourths of the
epidermal thickness. The protection of the body by the
epidermis is due to the functional features of the
stratum corneum.
• The renewal of the epidermis takes about 3 to 4 weeks
in humans as millions of cells are produced daily.
• Cells die as they are pushed away from the source of
nourishment. Cells undergo keratinization as a tough
protein, keratin, is deposited within the cell.
• Keratin hardens and flattens the cells as they move
outward and it waterproofs the skin.
SKIN COLOR
• Three skin pigments
• Melanin: the most important
• Carotene: from carrots and yellow veggies
• Hemoglobin: the pink of light skin
OTHER PIGMENTS IN SKIN
• Carotene – a yellow
pigment in skin usually
hidden by the effects of
melanin. Asians have little
melanin which allows the
yellow to show more than
other nationalities.
• Pinkish color – seen in fairskinned persons because
the vascular dermis is
visible.
• Cyanosis – blue look to
skin due to poorly
oxygenated blood
• Blushing – caused by
dilation of blood vessels
• Pale by fright – caused
by constriction of vessels
RESPONSE TO DISEASE
•
Jaundice – caused when
Bilirubin is deposited in skin
because a diseased liver is
unable to excrete this
pigment
•
A bruise indicates that blood
has escaped from the blood
vessels and has clotted under
the skin.
•
Malignant melanoma – a
cancerous change in a mole
that may metastasize
(spread) rapidly and is most
difficult to treat. Exposure
to sunlight increases risk.
•
Skin may appear bronzed due
to the deposit of excess
melanin when a person’s
adrenal gland is functioning
poorly.
DERMIS
• The dermis, or corium, consists of dense
fibrous connective tissue with numerous
collagenous and elastic fibers.
• The dermis is much thicker than the
epidermis. In thick skin, dermal papillae create
a very irregular border between epidermis and
dermis.
• Blood vessels, nervous tissue, some muscle
tissue, certain glands, hair and nails are found
in the dermis.
• Strong, flexible connective tissue: your
“hide”
• Fiber types: collagen, elastic, reticular
• Critical role in temperature regulation (the
vessels)
• Nerve endings allow us to sense pain,
temperature, pressure, and touch.
DIVISIONS OF THE DERMIS
1. The Papillary Layer: has loose connective tissue
This layer lies directly beneath the epidermis and
connects to it via Papillae ( fingerlike projections).
Some papillae contain capillaries that nourish the
epidermis; others contain Meissner’s Corpuscles(
touch receptors).
A double row of papillae in finger pads produces the
ridged fingerprints on finger tips.
2. The Reticular layer which has dense connective
tissue
These layers are so closely connected that they are
difficult to differentiate.
GLANDS
EXOCRINE GLANDS
• Sebaceous glands or oil glands are simple
branched areolar glands. They secrete the
sebum (seb = oil) an oily product.
• Sebum is usually secreted into a hair follicle.
Sebum is a natural skin cream: it helps hair
from becoming brittle, prevents excessive
evaporation of water from the skin, keeps the
skin soft and contains a bactericidal agent that
inhibits the growth of certain bacteria.
• Sebaceous glands are scattered all
over the surface of the skin except in
the palms, soles and the side of the
feet.
• When the sebaceous glands
oversecretes and bacteria acts on the
secretions, a blackhead or pimple
results.
SWEAT GLANDS
• Sweat glands or sudoriferous glands are simple
coiled tubular glands. They are divided into two
principal types: eccrine and apocrine.
• Apocrine glands are found mainly in the skin of
the armpits, of the anogenital areas and of the
areola of the breasts. Their secretory portion
can be located in the dermis or in the
hypodermis. Their excretory ducts open into
hair follicles. Their secretion is more viscous
than that of the eccrine glands. They start
secreting at puberty and may be analogous to
the sexual scent glands of other animals.
• Eccrine glands are the most common.
• Their secretory portion can be located in
the dermis or in the hypodermis. They
produce sweat, a watery mixture of salts,
antibodies and metabolic wastes. Sweat
prevents overheating of the body and thus
helps regulate body temperature.
ACCESSORY STRUCTURES OF THE
SKIN
Hair
• A characteristic feature of the human skin is
the apparent lack of hair on most of the body
surface. This is actually not quite true. Most
of the skin is haired although the hair in most
areas is short, fine and only lightly pigmented.
• Truly hairless are only the palms of hands and
soles of feet, the distal phalanges and sides
of fingers and toes and parts of the external
genitalia.
• Hair development begins in the third fetal month
( 17th - 20th week) .
• By the fifth month of fetal life( 25 th – 28th week),
Lanugo ( fetal hair) covers the fetus.
• At 5 months after birth, lanugo disappears from
every area except the scalp and eyebrows where
coarser hair replaces it.
• Vellus ( a film of delicate hair) eventually covers
the rest of the body.
• Terminal hair is the early coarse scalp and
eyebrow hair and later armpit and genital hair
that grow during puberty.
ACCESSORY STRUCTURES OF THE SKIN
• In those parts of the skin which we perceive as
"hairy" we find terminal hairs. The free part of
each hair is called the shaft.
• The root of each hair is anchored in a tubular
invagination of the epidermis, the hair follicle,
which extends down into the dermis and,
usually, a short distance into the hypodermis.
• The hair that you groom daily is actually dead
keratinized cells.
• Each hair follicle has an associated bundle of
smooth muscle, the arrector pili muscle. This
muscle inserts with one end to the papillary layer
of the dermis and with the other end to the
dermal sheath of the hair follicle. This makes your
hair stand up on its end.
HAIR COLOR AND TEXTURE
• Hair color is determined by the amount and
type of melanin present.
• Melanocytes become less active with age (and
hydrogen peroxide is produced by hair follicle
neutralized by an enzyme). Gray hair is a
mixture of pigmented and non-pigmented hairs.
• Red hair results from a modified type of
melanin that contains iron.
• The shape of the hair shaft determines
texture.
• Round shaft – straight hair
• Oval shaft – wavy hair
• Flat shafts – curly or kinky hair
Alopecia is the term for hair loss.
• Functions of hair
• Warmth – less in man than other mammals
• Sense light touch of the skin
• Protection - scalp
ACCESSORY STRUCTURES OF THE
SKIN
• Nails
• Plates of stratified squamous epithelial cells
with hard keratin
• Protect distal ends of phalanges
• Cells are keratinized in the nail root
• Nail growth occurs in the lunula
• Cuticle is a fold of stratum corneum on the
proximal end of nail
DISORDERS OF THE INTEGUMENTARY SYSTEM
• Burns
• Threat to life
• Catastrophic loss of body fluids
• Dehydration and fatal circulatory shock
• Infection
• Types
• First degree – epidermis: redness (e.g. sunburn)
• Second degree – epidermis and upper dermis:
blister
• Third degree - full thickness
• Infections
• Fluid loss
• Heat loss
BURNS
First-degree
(epidermis only;
redness)
Second-degree
(epidermis and dermis,
with blistering)
Third-degree
(full thickness, destroying
epidermis, dermis, often part
of hypodermis)
Estimate by “rule of 9’s”
CRITICAL BURNS
• Over 10% of the
body has thirddegree burns
• 25 % of the body
has seconddegree burns
• Third-degree
burns on face,
hands, or feet
HOW SKIN HEALS
• When your skin gets cut, your body springs
into action to heal the wound. First, the body
works to limit blood loss by reducing the
amount of blood flowing to the wounded area.
• For wound healing to occur, certain factors
are needed. A good nutritional status which
includes adequate blood supply to provide
oxygen and nutrients and also remove
wastes.
PRIMARY HEALING ( WOUND HEALING
BY PRIMARY INTENTION)
This method applies when there is minimal tissue destruction and
when the wound edges are apposed. There are three (3)
stages which overlap.
a. Inflammation
b. Proliferation
c. Maturation
Inflammation:
The cut surface becomes inflammed and cell debris and blood
clot fills the gap between the cut surfaces in the first few
hours. Phagocytes ( neutrophils, macrophages) and fibroblasts
migrate into the blood clot.
The phagocytes begin to remove the clot and cell debris.
PROLIFERATION
Epithelial cells proliferate across the wound, through
the clot. The epidermis meets and grows upwards
until full thickness is restored.
The clot above the new tissue becomes the scab and is
shed after 3- 10 days.
Granulation tissue and collagen is secreted by the
fibroblasts. This invades the clot, restoring blood
supply to the wound.
Phagocytes remove the debris and bacteria.
MATURATION
• The granulation tissue ( type 3 collagen) is
then replaced by fibrous scar tissue.
• The collagen fibers are then rearranged
and wound strength increases.
• The scar becomes less vascular, appearing
after a few months as a fine line.
WOUND HEALING BY SECONDARY
INTENTION
This method follows destruction of a large amount of tissue or when the
wound edges can’t be apposed. E.g. large ulcers
The stages for wound healing are the same in primary healing.
Inflammation
Inflammation develops on the surface of healthy tissue and the necrotic
tissue sloughs off due mainly to the action of phagocytes.
Proliferation
Granulation tissue is deposited at the base of the cavity and grows upwards
towards the surface.
Phagocytes prevent infection by ingesting bacteria.
Granulation tissue can’t contract like normal skin tissue.
When granulation tissue reaches the level of the dermis, epithelial cells at
the edges proliferate and grow towards the center.
MATURATION
This occurs by fibrosis, in which scar tissue replaces
the granulation tissue.
This occurs over several months until the full
thickness of the skin is restored.
Wound contraction is caused by increased numbers
of myofibroblasts.
Scar tissue is shiny and doesn’t contain sweat glands,
hair follicles or sebaceous glands.
TEMPERATURE REGULATION
• In hot conditions
• Sweat glands under the skin secrete sweat
(a fluid containing mostly water with some
dissolved ions) which travels up the sweat
duct, through the sweat pore and onto the
surface of the skin. This causes heat loss via
evaporative cooling however, a lot of
essential water is lost.
• The hairs on the skin lie flat, preventing
heat from being trapped by the layer of
still air between the hairs. This is caused
by tiny muscles under the surface of the
skin called arector pili muscles relaxing so
that their attached hair follicles are not
erect. These flat hairs increase the flow
of air next to the skin increasing heat loss
by radiation. When environmental
temperature is above core body
temperature, sweating is the only
physiological way for humans to lose heat.
• Arterioles Vasodilation occurs, this is the
process of relaxation of smooth muscle in
arteriole walls allowing increased blood
flow through the artery. This redirects
blood into the superficial capillaries in the
skin increasing heat loss.
COLD TEMPERATURES
• If the skin temperature drops below 37°C
a variety of responses are initiated to
conserve the heat in the body and to
increase heat production. These include
• Vasoconstriction to decrease the flow of
heat to the skin.
• Cessation of sweating.
• Shivering to increase heat production in
the muscles.
• In lower animals, the erection of the hairs
and fur to increase insulation.
SKIN LESIONS
• The major types of
primary lesions are:
• Macule: A small,
circular, flat spot
less than 0.4 in (1
cm) in diameter.
The color of a
macule is not the
same as that of
nearby skin.
• Vesicle: A raised lesion
less than 0.2 in (5 mm)
across and filled with a
clear fluid. Vesicles
that are more than 0.2
in (5 mm) across are
called bullae or blisters.
• Pustule: A raised lesion
filled with pus. A
pustule is usually the
result of an infection,
such as acne, impetigo,
or boils.
PAPULE
• A solid, raised lesion
less than 0.4 in (1 cm)
across. A patch of
closely grouped
papules more than 0.4
in (1 cm) across is
called a plaque.
Papules and plaques
can be rough in
texture and red, pink,
or brown in color.
Papules are
associated with such
conditions as warts,
seborrheic keratosis.
NODULE
• A solid lesion that has
distinct edges and that is
usually more deeply rooted
than a papule. It can be felt
as a hard mass distinct
from the tissue surrounding
it. A nodule more than
0.8 in (2 cm) in
diameter is called a
tumor. Ex: acne vulgaris
WHEAL
•
A skin elevation
caused by swelling
that can be itchy and
usually disappears
soon after erupting.
Wheals are generally
associated with an
allergic reaction,
such as to a drug or
an insect bite.
• Scale. A dry, horny
build-up of dead skin
cells that often flakes
off the surface of the
skin. Diseases that
promote scale include
fungal infections,
psoriasis.
• Crust. A dried collection
of blood, serum, or pus.
Also called a scab, a
crust is often part of
the normal healing
process of many
infectious lesions.
EROSION
• Lesion that
involves loss of
the epidermis.
ULCER
• Lesion that
involves loss of
the upper portion
of the skin
(epidermis) and
part of the lower
portion (dermis).
• An ulcer that
appears as a deep
crack that
extends to the
dermis is called a
fissure.
FUN FACTS
• House dust is mainly skin flakes!
• If you laid out all your skin on a flat surface, it would have an area of
about 2 square meters.
• Skin weighs about 2.5 kilograms - the largest organ in the
body.
• What hurts if you pull it, but doesn't hurt if you cut it?
Your hair, of course!
• Skin is elastic - it springs back into shape when stretched. Some
medicines (estrogen, nicotine) can pass through the skin, but others
cannot (insulin). Why is that? Because only fat-soluble substances can
enter the skin, not water-soluble ones.
• Your hair stands on end and you develop 'goose bumps' because there
are tiny muscles attached to the hair follicles and they contract when you
are frightened or cold.