Chapter 4
Applied Learning Outcomes
Use the terminology associated with the
integumentary system
Learn about skin structure, function,
appendages, glands, and care
Understand the aging and pathology of
the integumentary system
Chapter 4 – The Skin and Its Parts
Overview
The integumentary system is a dynamic
continuous body covering composed
of:
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Blood vessels
Connective tissue structures
Glands
Hair
Nails
Skin
It is the largest organ system of the
human body.
Chapter 4 – The Skin and Its Parts
Overview
The skin has inherent or inborn features.
An example would be-nails only grow in the upper tips of fingers
and toes.-under genetic control.
Skin also has adaptive features-this refers to the ability of an
organism’s genes to respond to the environment.
Calluses on feet to protect underlying tissue and bone.
Blister on skin
Skin will darken when exposed to light
Skin will stretch as we grow
Skin can also shrink back as a person loses weight and after a
woman has a baby.
The Integumentary System
Develops from two embryological germ layers: the ectoderm and mesoderm.
Ectoderm forms outermost layer of skin from a simple squamous tissue-it becomes
stratified as embryo develops.
In some areas-the ectoderm forms nervous system which later becomes integrated into
the skin.
Development of Integumentary System
Dynamic continuous body covering that includes the skin and mucous membranes.
4 to 5 weeks after the egg is fertilized the integumentary system begins to develop.
6 to 7 weeks Deeper part of skin forms from mesoderm.
 8 to 9 weeks stem cells called mesenchyme (embryonic connective tissue) develop.
Fibroblasts develop from certain mesenchyme cells. Fibroblasts are cells that
secrete proteins that form collagen and elastin fibers)
10 weeks small ridges start to form between inner and outer layers of skin.
They ensure a large surface area of contact between these layers. -prevents separation of
layers when skin is stretched or rubbed.
11 weeks small nails at tips of fingers and toes start forming.
20 weeks glandular structures start forming -produce oil and sweat glands.
25 weeks embryo is able to produce skin coloration (pigmentation) Melanoblasts
differentiate in the mesenchyme. Few more weeks mature into melanocytes.
Also forming are the nervous tissue structures that help skin perceive pain, temp, and
touch.
What are the major
characteristics of the skin?
• Waterproof, stretchable,washable, and
permanent-press, that automatically
repairs small cuts, rips and burns and is
guaranteed to last a lifetime.
• Surface area of up to 2.2 square meters
• 11 pounds
• 7% of total body weight
• Pliable yet tough
What are the 3 major layers of
the skin?
• Epidermis (epi-upon)
– Composed of epithelial tissue (stratified squamous)
– Non-vascularized
• Dermis – underlies the epidermis
– Tough leathery layer composed of fibrous connective tissue
– Good supply of blood
• Hypodermis (Subcutaneous layer)
– Made of adipose and areolar tissue
– Stores fat, anchors skin, protects against blows
Epidermis
Dermis
Basement membrane
The Integumentary System
At birth:
The integument (skin)
has three distinct
layers: the epidermis,
the dermis, and the
hypodermis.
Chapter 4 – The Skin and Its Parts
Epidermis
Dermis
Hypodermis (Subcutaneous layer)
Skin Structure
Epidermis – Outermost layer, where new skin cells are continually produced
Composed of stratified squamous epithelium.
--Older cells on the outside
--Innermost layer (Stratum basale or Stratum germinativium) is made of metabolically active cells undergoing
mitosis.
It takes 60-75 days for these cells to reach outermost surface.
Cells of this layer are bound tight to the ridged layer of the dermis
(dermal papillae)
Malpighian layer is the layer of epidermis containing melanocytes.
It is found in and above the stratum germinativium.
Melanocytes- are cells that secrete black to brown colored chemical
called melanin.
--Stratum spinosum (prickly layer)-second innermost layer of the epidermis.
In this layer Langerhans cells (immune cells) important in fighting skin
infections and healing injured skin.
--Stratum granulosum- has granules in cytoplasm that reflect an accumulation of yellowish sulfur rich
protein called keratin. Keratin is a tough protein that gives skin its strength.
Keratocytes also produce a substance that acts as waterproofing material.-prevents free flow of water
into and out of skin.
--Stratum compactum -layer of dying cells that are filled with keratin.
--Stratum corneum- uppermost layer of the skin. It is composed of flattened dead cells that regularly shed
What are the layers of the
epidermis?
• Stratum basale or stratum germinativum: deepest layer
of the epidermis, undergoes rapid cell division.
• Stratum spinosum: intermediate layer, contain spiny
shaped keratinocytes, Langerhans cells (immune cells)
• Stratum corneum: outermost layer 20-30 cells thick of
dead keratinized cells.
– Dandruff
– Average person shed 40 pounds of these cells in their lifetime.
What are the different types of
cells in the epidermis?
• Keratocytes
– Produce a fibrous protein
called keratin
– Are formed in the lowest levels
of the epidermis.
– Pushed upward by the
production of new cells
beneath them.
– Become dead and scale-like
-- Gives skin strength and
waterproofing.
– Millions rub off everyday
What are the different types of
cells in the epidermis?
• Melanocytes
– Synthesizes the
pigment melanin
– Melan-black
– Protects skin from
ultraviolet light.
melanocyte
Melanin in
keratinocytes
What are the different types of
cells in the epidermis?
• Langerhans’ cells
– Formed in bone
marrow.
– Move to the skin
– Found in stratum
spinosum
– Macrophages
Langerhans’
cell
What are the characteristics of
the dermis?
• Made up of connective tissue
• Richly supplied with blood vessels and
lymph vessels
• Has hair follicles, oil and sweat glands and
sensory receptors
What causes the color of skin?
• 3 pigments contribute to skin color
– Melanin- protein pigment (natural sunscreen)
• Can range in color from yellow to reddish-brown to black
• Everyone has the same number of melanocytes but make varying
amounts and colors (differences in skin color)
• Increased melanin production can caused by sunlight.
– Carotene-yellow to orange pigment found in carrots.
• Most commonly found in the palms or soles. Most intense when large
amounts of carotene-rich foods are eaten.
– Hemoglobin- Red blood gives a pinkish hue to fair skin
Dermis – middle layer, composed mostly of connective tissue
attached to the stratum germinativum by hemidesmosomes
(specialized junctions between an epithelial cell and the basement
membrane) along the dermal papilla.
Dense, irregular connective tissue makes up the bulk of the dermis.
It also contains loose connective tissue called areolar connective
tissue.
Areolar connective tissue is found throughout the body. It binds
blood vessels, membranes, muscles, nerves, and skin to other
structures.
Hypodermis (or Subcutaneous layer) – innermost layer
It is absent or very thin in the eyelids, penis, scrotum, and nipples.
After puberty- it is responsible for increase in size of female breasts
and hips.
--Composition- loosely arranged elastic fibers that anchor the skin to
underlying fascia (fibrous connective tissue covering muscle, the skull,
and some organs).
Also has a large amount of adipose tissue
Has a lot of blood and lymphatic vessels.
Has deep nerves
Sometimes microbes enter this layer and cause fasciitis. It can also be caused by
injury that leaves fragments of bone or other material in the skin.
What are the major appendages
of the skin?
• Sweat glands
• Sebaceous glands
• Nerves
• Hairs
• Nails
They are any complex structure that assists
the skin with its functions.
• What are the types of glands found in the skin?
• Sweat glands-sudoriferous
– Apocrine- produce sweat plus a milky or yellowish substance
composed of fat and protein.
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Found in the arm pits and genitalia
Thought to be scent glands.
Inactive until puberty
Secrete chemicals called pheromones
Secretions readily broken down by bacteria-causes body odor
– Eccrine-found mostly on skin of armpits, forehead, palms, soles
• Eccrine sweat composed mainly of water, many chemicals causing
food odor leak out of body by eccrine sweat.(Most numerous)
• These secretions also cause body odor due to bacterial breakdown
– Ceruminous- produce cerumen (ear wax)
• Apocrine gland
• Large glands found in skin lining the ear canal
Types of Glands (cont’d)
• Sebaceous glands- oil glands (sebum)
- Holocrine-means they secret whole dead cells
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Softens and lubricates hair and skin
Produce and store a lot of fat
Once secreted in the gland ducts they burst open and die
Releases fats on the surface of skin as an oily secretion.
Slows water loss and kills bacteria
Secrete sebum into hair follicles
Nerves in the Integumentary system
Sensory receptors- nerve cells found in all skin layers
are critical for the skin’s ability to
communicate information from the
environment to the body.
Types of Sensory Receptors
Free nerve endings-numerous pain-sensing structures
found in the lower part of the epidermis.
detect chemicals associated with tissue
damage and bleeding.
Merkel cells- nerves sensitive to gentle physical
sensations
found in small numbers in the stratum
germinativum.-most numerous in fingertips
Meissner’s corpuscles-(tactile) nerves found in upper region
of dermis (in dermal papilla). Responds to pressure.
They are nerve receptors surrounded by club-shaped
pile of connective tissues.
Nerves continued
Pacinian corpuscles (Lamellated)-look like onions, located in deeper parts
of the hypodermis, respond to hard pressure
Ruffini receptors-nerves that respond to pressure or constant touch
Krause end bulbs-nerves found in the mucous membrane of the mouth
sensitive to touch
Free nerve
Meissner
Krause
Ruffini
Pacinian
receptor endings
Free nerve endings
function
Different types respond
to mechanical, thermal,
or noxious stimulation
Responds to vibrations
and pressure
location
Various types found
throughout the skin
Dermis of Skin
(Dermal Papilla)
Messiner’s
Responds to hard pressure
Pacinian
Deeper part of hypodermis
in both hairy and glabrous skin
receptor endings
function
Responds to pressure
or touch
location
Dermis of both
hairy or glabrous
(smooth) skin.
Ruffini
Krause
Responds to pressure
or touch
In the stratum
germinativum
Merkel
Lips, tongue, and
genitals
Touch receptors
What are the parts of nails?
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A nail is a scale like modification of the epidermis
Made of tightly compressed keratinized cells
Useful tools to pick up small objects or scratch an itch.
Nails will grow back if removed as long as the nail root
and skin-nail folds are not damaged.
 Parts of the nail-
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Nail root-the area of nail where growth takes place.
Skin-nail folds-a fold of hardened overlapping the base of a fingernail or
toenail.
Nail body or matrix- is the fingernail or toenail.
Lunula-the white half moon shape at the base of the nail body.
Cuticle- an outgrowth of the skin-nail fold.
Why is hair useful?
• Senses insects that land on the skin.
• Hair on the head protects the head from a
blow, sunlight and heat loss.
• Eyelashes shield the eye
• Nose hairs filter the air
What are hairs?
• Modified stratum corneum formed by inward
protrusion of epidermis called the hair follicle.
• Made of dead keratinized skin cells
• Two parts shaft and root
• Shaft has 3 layers of cells
– Medulla (central core)
– Cortex (bulky layer)
– Cuticle (heavily keratinized; protects hair)
Parts of the hair
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Hair follicle- buried in the hypodermis. Each hair grows from a follicle
Hair papilla-the base of the hair follicle. Associated small blood vessels and a
nerve.
Hair shaft-the main part of the hair structure.
Most hair shafts are composed of two regions
– Outer hair cortex made dead, densely packed keratinized cells
– Hair cuticle-dried surface found on large hairs
– Hair medulla-found inside the hair cortex--composed of loosely arranged cells.
• Keratin-gives a yellow color to hair
• Melanocytes at base of the hair secrete the red, brown, and black pigmentation
• Differences in hair color are due to the amount and location of melanin deposited in the
cortex and medulla.
Accessory structures to the hair
• Arrector pili muscle
• Sebaceous gland
• Types of body hair
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Vellus hair-fine body hair-chest, face, stomach
Terminal hair- hair on the head
Pubic hair- around the genitals
Lanugo- temporary fine body hair found on fetuses and new born
babies
Functions of the Integumentary System
• Protection
• Acts as a barrier against three types of environmental damage:
• Chemical-any chemical including water that breaks down cells or
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connections between cells
Sweat, cerumen, and sebum help protect the skin from chemicals
Mechanical- damage caused by any force that compresses, erodes, or
stretches the skin. -shedding of stratum corneum reduces skin erosion, adipose
helps absorb shocks, callus minimize compression damage.
Microbial- damage caused by microorganisms on the skin. Microbes can
produce destructive secretions in sebum and sweat. These secretions are kept
in check by chemicals in sweat that assist beneficial bacteria-commensals.
Commensal bacteria and yeast reduce the chance that harmful
microorganisms will survive on your skin.
Functions of the Integumentary System
• Heat Regulation --Body’s ability to maintain a
constant temperature.
• Special network of blood vessels expands and contracts to
control body temperature.
• Evaporation of sweat lowers the body’s temperature
• Adipose tissue in the subcutaneous (hypodermis) keeps
body from lsing too much heat.
Functions of the Integumentary System
• Sensations-Received stimuli from the environment.
• Sensory receptors permit the skin to detect cold, heat, injury, pressure,
stretching, and touch.
• Waste Excretion-handled primarily by eccrine
sweat glands.
• Eccrine waste products are urea, organic chemicals, and excess salt.
• Other functions• Production of Vitamin D when exposed to sunlight.
Burns to the Skin
• Burns cause skin to lose its ability to maintain
homeostasis.
• Burns can be caused by sunlight, cooking accidents, acids,
bases, corrosive chemicals, electricity, and fires.
• First degree burns-involve superficial damage causing reddening
and swelling of the skin. Usually only upper layers of the epidermis
involved
• Second degree burns-damage to lower layers of epidermis and
top layer of dermis. Blisters, reddening, swelling, fluid build up are
indicators.
• Third degree burns-entire epidermis is charred or missing.
Usually damage to dermis that can cause permanent nerve cell loss.
Glands can be damaged. Adipose cells, muscle, and bone may be
affected. Person is susceptible to dehydration, loss of body heat, and
infection.
Wellness and Illness over
the Life Span
Aging is due to:
• intrinsic factors
• extrinsic factors
One’s lifestyle can accelerate aging.
Pathology can be categorized as:
• degenerative
• genetic
• infectious
Chapter 4 – The Skin and Its Parts
Pathology of the Integumentary System
Degenerative skin disorders- due to progressive deterioration of tissue
caused by continous injury from environmental and or physical stresses.
Solar lentigenes-freckles in people over 30 who overexpose their skin to
sunlight or tanning beds.
Dermatitis- an inflammation of the skin caused by an allergic reaction or
contact with an irritant.
Skin cancer- has an underlying genetic component- called precancerous
genes. If these genes are damaged by sunlight or certain
chemicals they can begin to divide abnormally.
Tumors not associated with cancer
Moles- flat squamous -cell tumors containing melanocytes
Skin tags- soft, colored, knob-shaped tumors that grow out of skin
Seborrhoeic keratosis- black or brown growth on the face or body.
Sebaceous hyperplasia- overgrowth of oil glands appear as small yellow
bumps with an opening in the center.
Syringomas- tumors of sweat gland ducts- appear as small lumps on
the cheek or eyelids.
Lipoma- fatty tumor under the skin.
Pathology of the Integumentary System
Genetic Skin Disorders -result of mutations that diminish skin function and
structure
Acne-believed to be stimulated by hormonal changes that cause overproduction
sebum.
Furuncle- (boil) inflammation of hair follicles that results in build up of cells
and blood components.
Psoriasis- inflammation of the skin accompanied by an increase in skin cell
production. Causes a build up of thick scales on the skin that appear red,
swollen and warm. The affected skin is dry and itchy.
Vitiligo- (hypopigmentation) Micheal Jackson. Found in 1% of the population
cause is unknown. Thought to be caused by an immune system attack on
the melanocytes. Treated with vitamins and drugs that are activated by U-V
light.
Albinism- genetic disease in which there is no melanin production in the eyes,
hair, or skin.
Melasma- brown patches on both sides of the face. Distribution usually
symmetrical. See on some pregnant women.
Types of Birthmarks
Port wine stains-looks like a spot of red wine spilled on the skin.
It is due to abnormality of skin blood vessels
Affects less than 1% of population
Spider veins- describes another type of enlarged blood vessel
condition of the skin.
Tend to see them in legs of older people
Strawberrry hemangiomas
Summary
The skin is composed of three distinct layers: the
epidermis, the dermis, and the hypodermis
(subcutaneous)
It contains many appendages, including several
kinds of glands, nerves, nails, and hair
The functions of the skin are: to protect the body
from damage, help regulate body temperature,
detect sensory cues, and assist in waste
removal
Chapter 4 – The Skin and Its Parts