The Integumentary System
Unit 4
Unit 4 Objectives:
1. Define all vocabulary words. (BLM 1)
2. Describe the functions of the skin. (BLM 1)
3. Describe the three major divisions of the spin (epidermis, dermis, hypodermis), and explain the major
anatomy and physiology of each division. (BLM 1 -3)
4. Name the five layers of the epidermis, and describe the unique structural characteristics of each layer.
Relate the structure of each layer to its function. State the cell types found in each layer, and whether
those cells are alive or dead. (BLM 1-3)
5. Label the five layers of the epidermis on a diagram. (BLM 1)
6. Explain what causes skin pigmentation from an anatomy and physiology perspective. (BLM 1-3)
7. Describe the structure, function, purpose and locations of the various accessory organ structures in the
dermis (hair, glands, nerve endings, dermal papillae). (BLM 1-4)
8. Compare and contrast eccrine, apocrine and sebaceous glands. (BLM 3)
9. Identify which nerve receptors respond to which particular type of stimulus. (BLM 1)
10. Explain the process your body goes through in order to regulate a too-low temperature. (BLM 4)
11. Explain the process your body goes through in order to regulate a too-high temperature. (BLM 4)
12. Compare and contrast 1st, 2nd, and 3rd degree burns in terms of layers of skin involved, short term and
long term damage. (BLM 1-3)
13. Describe the symptoms, causative agent, affected areas, and prognosis for various diseases of the skin
(acne, contact dermatitis, tinea, warts, impetigo, chickenpox, ulcers, psoriasis, skin cancer). (BLM 1 – 4)
Unit 4: Integumentary System
1)
2)
3)
4)
5)
6)
7)
Functions of the Skin
Divisions of the Skin
The Structure of the Epidermis
Structures of the Dermis
The Hypodermis
Temperature Regulation
Diseases of the Integumentary System
1. Functions of the Skin
i. Forms the primary barrier which protects the
body against infectious agents (bacteria,
viruses, protozoan, and fungi)
ii. Protects the body against damaging ultraviolet
(UV) radiation from the sun.
iii. Regulation of body temperature
iv. Sensory input from the environment
v. Production of vitamin D
vi. Prevents desiccation (drying out)
Unit 4: Integumentary System
1)
2)
3)
4)
5)
6)
7)
Functions of the Skin
Divisions of the Skin
The Structure of the Epidermis
Structures of the Dermis
The Hypodermis
Temperature Regulation
Diseases of the Integumentary System
2. Divisions of the Skin
Hypodermis
2. Divisions of the skin
• The skin is composed of three layers:
epidermis, dermis, hypodermis
1. Epidermis - (outer layer)
a. Composed of stratified squamous keratinized
epithelium
b. Avascular.
c. Most cells are keratinocytes
2. Divisions of the skin
2. Dermis – (middle layer)
a. Composed of dense irregular connective tissue
b. Contains “accessory organs” such as:
•
•
•
•
•
•
•
Hair follicles
Eccrine and apocrine glands(sweat glands)
Sebaceous glands (oil glands)
Blood vessels
Nerve endings
Arrector pili muscles
Capillary beds
2. Divisions of the skin
3. Hypodermis – (lower layer or subcutaneous
layer, deep to the dermis)
a.
b.
c.
d.
Composed of mostly adipose tissue
Contains arteries, veins, and large nerves
Anchors skin to underlying organs
Also called the subcutaneous layer
Unit 4: Integumentary System
1)
2)
3)
4)
5)
6)
7)
Functions of the Skin
Divisions of the Skin
The Structure of the Epidermis
Structures of the Dermis
The Hypodermis
Temperature Regulation
Diseases of the Integumentary System
3. Structure of the Epidermis
• The epidermis can be divided into several layers
because it is stratified.
• Divisions are dependent on the characteristics of
the cells found in each layer.
3. Structure of the Epidermis
The layers are listed from the innermost (deep) to
outermost (superficial):
1. Stratum basale (deepest)
2. Stratum spinosum
3. Stratum granulosum
4. Stratum lucidum (found only on the
palms of the hands and the soles of the feet)
5. Stratum corneum (most superficial)
3. Structure of the Epidermis:
1. Stratum Basale
1. Stratum basale: “base layer”
– Deepest layer of the epidermis (next to the dermis)
– Germ cells actively dividing (mitosis) and producing new
layers of epidermis
– Daughter cells are pushed upward to become more
superficial layers
– Contains specialized cells called melanocytes which produce
the brown pigment melanin responsible for protection
against UV radiation and responsible for the skin’s color.
3. Structure of the Epidermis:
2. Stratum Spinosum
2. Stratum spinosum: “spiny layer”
– This layer gets its name because the cells have
sharp or spine-like projections that interlock
to form a mesh-like layer.
– The cells are still alive
– Cells contain pre-keratin materials
3. Structure of the Epidermis:
3. Stratum Granulosum
3. Stratum granulosum: “grainy layer”
– The cells are dying and their organelles are
degenerating (breaking down)
– The cytoplasm contains lipids and keratohylaine
granules, which will become keratin.
– Looks grainy under the microscope
3. Structure of the Epidermis:
4. Stratum Lucidum
4. Stratum lucidum: “clear layer”
– This layer is found only where the epidermis
is thick (palms of hands and soles of feet)
– It is composed of a clear layer of dead cells
that are indistinguishable one from another.
3. Structure of the Epidermis:
5. Stratum Corneum
5. Stratum Corneum: “horny layer”
– Cells are dead
– The dead cells’ membranes form sacs which
contain keratin
– Waterproof layer
– Dead cell membranes dry and peel away at the
surface of the epithelium (dry/ashy skin)
Modified Epidermis: The Nail
• The nail is a scale-like structure composed of
keratin located at the end of the digits.
• It is secreted by the nail matrix.
• The nail has a free edge and is covered in part by
skin folds.
• The proximal fold of epidermis that projects
onto the nail body is called the cuticle.
Modified Epidermis: The Nail
• The lunula is a lighter area that is crescent
shaped and covers the thick nail matrix.
Lateral
nail fold
Lunule
(a)
Free edge
of nail
Body
of nail
Cuticle
Root of nail
Proximal
nail fold
(b)
Nail bed
Nail
matrix
Bone of fingertip
Figu
Skin Pigmentation
The color of a person’s skin comes from three sources:
• Melanin (primary source)
– Brown, or black pigments
• Carotene
– Orange-yellow pigment from some vegetables
• Pheomelanin
– Red pigment in lips, nipples and genital areas
• Hemoglobin
– Red coloring from blood cells in dermal capillaries
– Oxygen content determines the extent of red
coloring
Skin Pigmentation
• Melanocytes are found mostly in the stratum basale
• The pigment melanin, a protein, is produced by
melanocytes
• Melanin functions to block UV absorption by the skin
• Color is yellow to brown to black
• Amount of melanin produced depends upon genetics and
exposure to sunlight
• The more melanin produced, the darker the color of the
skin
Skin Pigmentation - Alterations in
Skin Color
• Redness (erythema)—due to embarrassment,
inflammation, hypertension, fever, or allergy
• Pallor (blanching)—due to emotional stress such
as fear, anemia, low blood pressure, impaired
blood flow to an area
• Jaundice (yellowing)—liver disorder
• Bruises—hematomas
Unit 4: Integumentary System
1)
2)
3)
4)
5)
6)
7)
Functions of the Skin
Divisions of the Skin
The Structure of the Epidermis
Structures of the Dermis
The Hypodermis
Temperature Regulation
Diseases of the Integumentary System
4. Structures of the Dermis
General Characteristics
• Overall dermis structure:
– Collagen and elastic fibers located throughout
the dermis
• Collagen fibers give skin its toughness
• Elastic fibers give skin elasticity
– Blood vessels play a role in body temperature
regulation
4. Structures of the Dermis
• The dermis of the skin is where the accessory
organs (hair, glands, pili arrector muscles,
nerves, nerve receptors and blood vessels) are
located.
A. Hair
B. Glands
C. Nerve Endings
D. Dermal Papillae
4. Structures of the Dermis
A. Hair
• Hair: Hair is produced
in structures called
follicles and is
composed of dead
keratinized cells.
• The shaft of the hair is
the portion that sticks
above the skin
Figure 4.8c
4. Structures of the Dermis
A. Hair
• Notice how the scale-like cells of the cuticle
overlap one another in this hair shaft image
(660×)
Figure 4.9
4. Structures of the Dermis
A. Hair
• There are two types of
hair:
1. Vellus (fine)
2. Terminal (coarse)
4. Structures of the Dermis
A. Hair
1. Vellus hair:
• Very fine, pale, hair on
the body surface of
children and adult
females
• Little or no pigment
4. Structures of the Dermis
A. Hair
• 2. Terminal hair:
coarse, longer, darker
hair found in the
eyebrows, scalp,
axillary and pubic
regions of adult male
and females.
• This is the type of hair
present in the beard of
adult males.
4. Structures of the Dermis
A. Hair
• Each hair follicle has its own muscle associated
with it – these are called Arrector pili muscles
• Arrector pili muscles cause the hair to stand
upright to help create a layer of insulation using
the hair.
• They are involuntarily controlled and are
responsible for “goose bumps” when you are
cold or frightened.
Hair
shaft
Arrector
pili
Sebaceous
gland
Hair root
Hair bulb
in follicle
(a)
Figure 4.8a
4. Structures of the Dermis
B. Glands
• The dermis contains
two basic types of
glands:
1. Sweat Glands
2. Sebaceous (Oil)
Glands
4. Structures of the Dermis
B. Glands
1. Sweat glands: appear
as tubular structures
produce sweat.
Two types of Sweat
Glands:
A. Eccrine sweat glands
B. Apocrine sweat
glands
C. Modified apocrine
glands
4. Structures of the Dermis
B. Glands
A. Eccrine: watery
sweat found all over
body.
• Open via duct to pore
on surface of
epidermis
• Produce sweat (clear)
4. Structures of the Dermis
B. Glands
B. Apocrine glands: produce sweat, fatty
substances, and protein.
– Ducts empty into hair follicles
– Located in the axillary (armpit) and pubic
regions.
– Responsible for body odor (pheromones).
– Become active during puberty.
Sweat
pore
Eccrine
gland
Sebaceous
gland
Dermal connective
tissue
Eccrine
gland duct
Secretory cells
(b) Photomicrograph of a
sectioned eccrine
gland (180×)
Figure 4.7b
Sweat and Its Function
A. Composition
– Mostly water
– Salts and vitamin C
– Some metabolic waste
– Fatty acids and proteins (apocrine only)
B. Function
– Helps dissipate excess heat
– Excretes waste products
– Acidic nature inhibits bacteria growth
C. Odor is from associated bacteria
4. Structures of the Dermis
B. Glands
C. Modified aprocrine
glands:
– Ceruminous glands:
in the ear, produce
cerumen (ear wax)
– Mammary glands: in
the breasts, produce
and secrete
breastmilk
4. Structures of the Dermis
B. Glands
2. Sebaceous glands: (oil glands)
• Produce & secrete oil (sebum)
– Lubricant for skin
– Prevents brittle hair
– Kills bacteria
• Most have ducts that empty into hair follicles;
others open directly onto skin surface
• Glands are activated at puberty
Sweat
pore
Sebaceous
gland
Eccrine
gland
Dermal connective
tissue
Sebaceous
gland duct
Hair in
hair follicle
Secretory cells
(a) Photomicrograph of a sectioned
sebaceous gland (14×)
Figure 4.7a
4. Structures of the Dermis
C. Nerve Receptors
C. Nerve receptors:
The skin has receptors
for pressure, pain, and
temperature.
I.
Meissner’s
corpuscles
II. Pacinian Corpuscles
III. Root hair plexus
IV. Free nerve endings
4. Structures of the Dermis
C. Nerve Receptors
I. Meissner’s corpuscles:
• Located just below the
surface of the epidermis
• Sensitive to light pressure
or touch
• Associated with “tickling
sensations”
4. Structures of the Dermis
C. Nerve Receptors
II. Pacinian Corpuscles
• Located deep in the
dermis
• Associated with
strong touch and
pressure.
4. Structures of the Dermis
C. Nerve Receptors
III. Root hair plexus
• One is associated
with each hair follicle
• Responsible for the
pain when your hair is
pulled.
4. Structures of the Dermis
C. Nerve Receptors
IV. Free nerve endings
• Scattered throughout the
dermis
• Specialized for the
reception of heat, cold,
or pain.
• Each nerve ending is
responsible for detecting
only one signal type.
4. Structures of the Dermis
D. Dermal Papillae
D. Dermal Papillae
• The upper surface of the dermis where the
epidermis joins, has ridges called dermal papillae.
• These ridges are your fingerprints
• They are unique to each individual
• Why don’t your fingerprints get sloughed off
and destroyed over time?
Structures of the Dermis
Structures of the Dermis
Unit 4: Integumentary System
1)
2)
3)
4)
5)
6)
7)
Functions of the Skin
Divisions of the Skin
The Structure of the Epidermis
Structures of the Dermis
The Hypodermis
Temperature Regulation
Diseases of the Integumentary System
5. The Hypodermis
A. Function
• The hypodermis functions in insulating the body
against cold temperatures due to the layer of
adipose tissue located here.
• It also functions in anchoring the skin to the
underlying organs (muscles).
• Sometimes it is referred to as the superficial
fascia.
5. The Hypodermis
B. Unique Characteristics
• It is this layer of the skin that thickens when one
puts on excessive weight.
• Females it accumulates first in the thighs and
breast, and in males it first accumulates in the
abdominal region (“pot belly”).
Unit 4: Integumentary System
1)
2)
3)
4)
5)
6)
7)
Functions of the Skin
Divisions of the Skin
The Structure of the Epidermis
Structures of the Dermis
The Hypodermis
Temperature Regulation
Diseases of the Integumentary System
6. Temperature Regulation
• Your skin acts similar to a radiator on a car to
disseminate heat that is produced by cellular
activity in your body and muscular contraction.
• When the body’s temperature goes above the set
homeostatic value, thermoreceptors in the skin
signal the hypothalamus.
6. Temperature Regulation
• The hypothalamus (in the brain) triggers several
changes to decrease body temperature.
1. The blood vessels (arterioles) in the dermis dilate,
increasing blood supply to the capillary beds in
the dermis
2. The eccrine glands begin to secrete watery
sweat which moves to the surface of the
epidermis.
6. Temperature Regulation
3. The heat is transferred from the blood in your
capillaries, through the dermis and epidermis, to
the surface of the epidermis, where it is absorbed
by the water in the sweat
4. The sweat then vaporizes or evaporates, taking
the heat with it.
5. The blood has now lost heat and is at a lower
temperature and returns to the inner body away
form the surface to cool the inner body structures.
• What type of feed-back mechanism is this?
6. Temperature Regulation
6. Temperature Regulation
• When the body’s temperature falls below the set
homeostatic value, thermoreceptors in the skin
signal the hypothalamus.
1. The hypothalamus responds by signaling the
arterioles to constrict, forcing blood toward the
interior organs necessary for survival.
2. The arrector pili muscles contract, generating
heat, and raising the hair trapping an insulating
layer of air between the skin and the environment.
6. Temperature Regulation
3. Shivering is the continuous contractions of
muscle to generate heat (from the use of ATP).
Unit 4: Integumentary System
1)
2)
3)
4)
5)
6)
7)
Functions of the Skin
Divisions of the Skin
The Structure of the Epidermis
Structures of the Dermis
The Hypodermis
Temperature Regulation
Diseases of the Integumentary System
7. Diseases and Disorders of the
Skin
• Burns: Burns can be
caused by heat,
chemicals, or
electricity.
• In all cases one or
more layers of the
skin is affected.
7. Diseases and Disorders of the
Skin
• 1st Degree burns:
Involve the epidermis
only and result in
redness and swelling
(edema).
• Usually no scarring of
tissue.
7. Diseases and Disorders of the
Skin
• 2nd Degree burns:
Involve the epidermis
and dermis, some
damage is done to
accessory organs,
blistering but usually
little scarring.
•
7. Diseases and Disorders of the
Skin
3rd Degree burns:
Involve the epidermis,
dermis, and hypodermis,
destruction of dermal
accessory organs, burn is
raw or blackened in
appearance.
• Severe scarring occurs,
long healing period,
usually involving skin
grafting.
7. Diseases and Disorders of the Skin
Immunological
• Acne vulgaris: Due to
formation of sebum plugs
(white heads) or (black heads oxidized oil plug) which block
the sebaceous gland and often
trap bacteria within the gland.
• It becomes inflamed.
• This can lead to the secondary
infections of sweat gland or
hair follicle forming pustules or
pimples.
• Common in adolescents.
7. Diseases and Disorders of the Skin
Immunological
• Chicken pox:
Chicken pox is due to
a viral infection
(Herpes zoster) of the
skin which affects the
nerve ending.
• This results in the
formation of blisters
that itch.
Diseases and Disorders of the Skin
Immunological
• Tinea: Ring worm,
Athlete’s foot, and Jock
itch are all the result of a
fungal infection of the
skin.
• This results in scaling,
erythema (reddening),
and occasional cracking
of the skin that burns or
itches.
Ring worm
Diseases and Disorders of the Skin
• Warts: Warts are due to
infection by the human
papilloma virus.
• The virus causes abnormal
growth of the epidermal layer.
• Normally warts are benign but
some forms can transform and
become malignant (cervical
cancer).
• Warts are transmitted by direct
contact from one person to
another.
Diseases and Disorders of the Skin
Immunological
• Impetigo: Impetigo is
caused by an infection of the
epidermis by Staphlococcus
or Streptococcus bacteria.
• It results in erythema,
formation of weeping blisters,
that form a yellow crusting on
their surface.
• It is highly contagious and
common in children.
Diseases and Disorders of the Skin
• Contact dermatitis: This is
due to an allergic reaction
with materials which the
skin has made contact.
• It is characterized by
erythema, edema, blistering
and scaling of the skin.
• Itching is usually associated
with the area affected.
• Poison Ivy is an example of
this disorder.
Diseases and Disorders of the Skin
Decubitus Ulcer or Bedsores Sores
• This condition is due to the cut off of blood to
the skin due pressure applied due to weight to
areas where the bones are close to the surface
• ankles, heels, knees, cheek, elbows, wrists, iliac
of pelvis.
• The tissue begins to die and infections set in.
Diseases and Disorders of the Skin
Decubitus Ulcer or Bedsores Sores
• These sores are common in patients who are
bed ridden or can not move.
• Frequent changes in body position and or
support cushions (air-foam mattresses) help
prevent decubitus ulcers.
Diseases and Disorders of the Skin
Psoriasis
• This disorder is believed be
congenital.
• The epithelial basal cell layer
grows too rapidly and this
produces large swollen,
erythmatic, scaly patches of
skin.
• The skin covering the joints
of the appendages are often
affected by this disorder.
Diseases and Disorders of the Skin
Skin Cancers
• Basal cell carcinoma: is
the least malignant and
most common skin
cancer.
• Basal cells grow
abnormally and invade
the dermis and
hypodermis. 99%
curable by surgical
excision.
Diseases and Disorders of the Skin
Skin Cancers
• Squamous Cell
Carcinoma: This cancer
develops from the cells
of stratum spinosum
appears as a scaly
reddened elevation that
grows rapidly and
metastasizes if not
removed surgically or
treated with radiation.
Diseases and Disorders of the Skin
Skin Cancers
• Melanoma: Most
dangerous of all skin
cancers. It affects the
melanocytes of the
stratum basale.
• It grows and
metastasizes rapidly
and is resistant to many
forms of treatments.
• They can develop from
moles which are dark
pigmented areas of the
skin.
Diseases and Disorders of the Skin
Skin Cancers
• The best treatment is early detection.
• The ABCD Rule of Melanoma:
Asymmetry: The two sides of the
pigmented mole does not match.
Border irregularity: The border is not
smooth but has indentations.
Color: The pigmented spot contains
several colors (black, brown, tans, blues,
purples, and reds)
Diameter: The spot is larger than 6mm.
The diameter of a pencil eraser.