OUTLINES: INTEGUMENTARY SYSTEM
INTRODUCTION
1) Integumentary system consists of :
a) Skin &
b) Accessory structures(appendages)
i) Hairs
ii) Nails
iii) Exocrine glands
(1) Sudoriferous
(2) Ceruminous
(3) Sebaceous
FUNCTIONS
A. Protection:
a. as physical barrier,
b. contains Langerhans cells (resident macrophages)=immunity
c. by retarding water
d. from UV radiation by producing melanin. Pigment melanin is produces by melanocytes.
B. Thermoregulation - the homeostatic control of body temperature
a. skin liberating sweat at its surface &
b. by adjusting the flow of blood in the dermis.
C. Synthesis of Vitamin D:
a. activation of a precursor molecule in the skin by UV light
b. enzymes in the liver and kidneys modifying the activated molecule to produce calcitriol, the most active
form of vitamin D.
D. Houses sensory receptors: touch, pressure, vibration, tickle, heat, cold, and pain
E. Minor roles in excretion: elimination of wastes from the body.
STRUCTURE OF THE SKIN
The skin is the largest organ of the body.
Skin consists of two layers: epidermis & dermis
1. The superficial portion of the
skin is the EPIDERMIS. It is
composed of epithelial tissue
(keratinized stratified squamous
epithelium).
2. The deeper layer of the skin is
the DERMIS; Itis primarily
composed of connective tissue.
3. Deep to the dermis is the
subcutaneous layer or hypodermis.
a. It is NOT a part of the skin.
b. It consists of areolar and
adipose tissue.
c. It serves as a fat storage area,
an area for blood vessel passage.
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EPIDERMIS
a. The epidermis is composed of keratinized stratified squamous epithelium
b. Lacks blood supply
1. Receives nutrients & oxygen by passive transport (diffusion, filtration) from dermis (directly from
papillary region)
c. Has 4 major types of cells
1. Keratinocytes:-the most abundant
 produce the protein keratin
 protects from heat, microbes, & chemicals
 Produce lamellar granules, which release oily
substance acting as a waterproof sealant
2. Merkel cells
 In stratum basale
 Together with nerve ending it forms Merkel’s
disk which function is to detect soft touch.
3. Melanocytes: in stratum basale
 produce the pigment melanin which
contributes to skin color & absorbs damaging
ultraviolet (UV) light protecting DNA from
mutation
4. Langerhans cells :
 Found in stratum spinosum
 Resident macrophages –phagocytize pathogens, important in immunity
d. There are four (thin skin) or five (thick skin) layers of the epidermis,
From the most superficial to the deepest layers of the epidermis are:
External environment
stratum Corneum
stratum Lucidum (only in palms and soles),
stratum Granulosum,
stratum Spinosum,
stratum Basale (stratum germinativum),

The stratum corneum
a. 25-30 layers of dead keratinized squamous cells
b. continuously shed
c. Protect from chemical & physical stress
d. repels water
2) The stratum lucidum
a. present only in the thick skin.
b. 3-5 layers
c. appears translucent
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3) The stratum granulosum
a. 3-5 layers
b. cells undergo apoptosis
c. Lamella granules
d. Keratinozation starts
4) The stratum spinosum
a. 8-10 layers of cells
b. Langerhans cells
5) The stratum basale
a. the Deepest layer
b. single row of cuboidal
c. constant mitosis
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DERMIS
The dermis is composed of connective tissue containing collagen and elastic fibers and has two regions.
1) The papillary layers:
a. Top 20% of dermis
b. areolar connective tissue
c. dermal papillaed. blood vessels
e. Meissner’s corpuscles .
f. free nerve endings
2) The reticular region:

Deep 80% of dermis

attached to hypodermis

Dense irregular CT

Sudoriferous glands

Sebaceous gland

Hair follicles

Arrector pili muscles
(smooth muscle, goose pumps)

Hair root plexus

Pacinian corpuscles, Ruffini corpuscle
SENSORY RECEPTORS
They belong to NERVOUS SYSTEM but many are found in the skin.
1) Free nerve endings
a. Naked dendrites
b.Pain and temperature
c. In deep EPIDERMIS & superficial dermis
2) Merkel disc
a. very sensitive
b. Detects soft touch
c. Deep epidermis (stratum basale)
3) Meissner’s (tactile) corpuscle
a. encapsulated
b. Detects Soft touch
c. In dermal papillae of papillary region (dermis)
4) Ruffini corpuscle
a. Encapsulated
b. Deep dermis
c. Crude touch, stretch
5) Pacinian (lamellated)corpuscle
a. encapsulated
b. In DEEP DERMIS or HYPODERMIS
c. Pressure, vibration, crude touch
6) Hair root plexus
a. naked dendrite
b. around hair follicle
c. detects movement of hair (wind or insect)
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TYPES OF SKIN
External environment
A. THIN SKIN covers all parts of the body except for the palms
soles.



It lacks epidermal ridges
HAS 4 layer of epidermis, less sensory receptors than
thick skin.
It has hair with accessory structures(arrector pili muscle)
Dermis
External environment
B. THICK SKIN covers the palms, palmar surfaces of the digits, and
soles.
1. It HAS stratum lucidum, thick epidermal ridges, more
sensory receptors
2. It LACKS hair follicles, arrector pili muscles, and sebaceous
glands, and has more sweat glands than thin skin.
Dermis
C. Transdermal drug administration is a method of drug passage across
the epidermis and into the blood vessels of the dermis
a. lipid soluble substances are ideal for transdermal drugs
b. water soluble drugs have difficulties diffusing through epidermal layers due to water repellent properties of
epidermis.
ACCESSORY STRUCTURES OF THE SKIN
Accessory structures of the skin develop from the embryonic epidermis and include hair, glands, and nails.
GLANDS
1. Sebaceous (oil) glands
a. usually (but not always)connected to hair follicles
b. absent in the palms and soles
c. sebum, which moistens hairs, waterproofs and softens the skin, and
inhibits bacterial growth.
2. Sudoriferous (sweat)
glands are divided into
apocrine and eccrine types.
a. Eccrine sweat glands





widely distributed
ducts terminate at pores at the surface of the epidermis.
found in deep dermis
secrete watery sweat
main function is thermoregulation through evaporation.
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b. Apocrine sweat glands
 found in a skin of the axilla, pubis, and areolae;
 ducts open into hair follicles.
 found in deep dermis or hypodermis
 secrete thick sweat ( a lot of amino acids →epidermal bacteria metabolize it →excretion →bad odor)
 active after puberty
 ↑secretion during stress/ sexual excitement.
3. C e r u m i n o u s g l a n d s
 are modified sudoriferous glands
 produce a waxy substance called cerumen.
 found in the external auditory meatus
H A I R S , or pili,
 present on the most of skin surfaces, except the palms & soles
 Hair consists of:
1. a shaft- above the surface
2. a root - penetrates the dermis and subcutaneous layer
3. found in hair follicle
 Associated with hairs are sebaceous (oil) glands, arrector pili muscles, and root plexuses
 Hair color is due primarily to the amount and type of melanin.
MAINTAINING HOMEOSTASIS: THERMOREGULATION
Normal body temperature is 98.6°F or close to 37°C
HYPERTHERMIA – high body temperature; Thermoreceptors in the skin, brain, & liver detect ↑T & send
information to hypothalamus; hypothalamus evaluates input & sends command to effector organs: 1)sweat glands to
↑secretion of sweat →evaporation 2) dermal blood vessels to dilate (so more volume of blood at lower velocity will
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circulate closer to the surface giving off heat = radiation)
HYPOTHERMIA – low body temperature; Thermoreceptors in the skin & brain, detect  T & send information to
hypothalamus; hypothalamus evaluates input & sends command to effector organs: 1) sweat glands to inhibit sweating
2) blood vessels to constrict (less volume of blood at higher velocity will circulate close to surface of a skin →preserves
heat) 3) skeletal muscles to shiver ( involuntary small contraction of skeletal muscles produce heat) 4)medulla of
adrenal gland secretes more Epinephrine & norepinephrine →↑metabolism →↑body temperature 5) anterior
pituitary to secrete TSH →thyroid gland to secret T3 & T4 (increase basal metabolic rate →↑body temperature; long
term solution)
SKIN COLOR & PIGMENTS
1. The wide variety of colors in skin is due to three pigments melanin, carotene, and hemoglobin (in blood in capillaries in
the dermis)

melanin black/brown-eumelanin & yellow/red –
pheomelanin; color depend on AMOUNT of melanin
1.
Albinism is the inherited inability of an individual to
produce melanin

carotene – yellowish/orange color

hemoglobin – gives blood bright red color =pink hue
to the skin
1. People with fair skin blush = vasodilation;
vasoconstriction – pale)
2. The color of skin and mucous membranes can provide clues for diagnosing certain problems, such as cyanosis,
jaundice, and erythema.
cyanosis – bluish color due to hypoxia (tissue oxygen starvation)

jaundice – yellowish/greenish color due to pigment bilirubin

erythema - rash.
Erythema
Jaundice
Cyanosis
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