Integumentary System
Basic Knowledge
Skin
largest organ in the body
makes up approximately 15% of the body’s total weight
has two layers which are the epidermis and the dermis
Epidermis
is the skin’s most superficial layer
composed of squamous epithelial muscle
Dermis
composed of loose/areolar connective tissue over dense irregular connective tissue.
the cutaneous glands, the hair follicles, and most of the skin’s nerve endings can be seen in the dermis.
Hypodermis/ Subcutaneous Layer
Mainly composed of adipose connective tissue, the hypodermis serves as an insulating layer, a cushioning layer, and an energy source.
This layer is generally thicker in women than in men.
More Information
Epidermis
superficial layer of the skin
has four-five general layers called the strata.
Stratum Basale
contains a single layer of cuboidal cells.
it is the only stratum of the epidermis with cells that actively grow and divide to produce new epidermis.
Stratum Lucidum
only found on thick skin.
not found in thin skin
Stratum Corneum
is the most superficial stratum.
has as many as 20 layers of cells.
it is composed of tough, waterproof dead cells that flake off.
Layers of the Epidermis (in order)
Stratum Basale
Stratum Spinosum
Stratum Granulosum
Stratum Lucidum
Stratum Corneum
Cells of the Epidermis
Keratinocytes
begin in the Stratum Basale and make up the majority of the epidermal cells.
their purpose is to grow and divide
they fill them selves up with keratin as they move up to the surface.
cornification is when the keratin filled keratinocytes reach the surface and fall off.
Melanocytes
produces the skin pigment called melanin.
Tactile Cells
serves as receptors for fine touch only.
Dendritic Cells
are immune cells found in the stratum spinosum and stratum granulosum.
they alert the body’s immune system to the invasion of pathogens that could make it to the stratum corneum.
Dermis
sometimes called “true skin”.
blood vessels, fibers, nerve endings, hair follicles, and cutaneous glands are found in the dermis.
Papillae
bumps on the superficial edge of the dermis, which are in direct contact in the epidermis.
are arranged in a random pattern over most of the body, form individual-specific patterns of ridges on the palmar and plantar surfaces.
This unique arrangement creates fingerprints
The papillae’s numerous small blood vessels provide nearby stratum basale cells with nutrients they need to grow and divide.
Fibers
The dermis changes from loose/areolar tissue to dense irregular connective tissue with depth. Both of these tissue types are characterized by cells and fibers in a matrix, but they lack a neat dividing line between them
The cells (fibroblasts) of both tissues produce two types of protein fibers: collagen and elastin.
Collagen
gives the skin strength
Elastin
provide elasticity, which allows the skin to come back to shape if stretched.
Nerve Endings
Nerve cells have endings in the dermis that serve as receptors.
These receptors include warm receptors, cold receptors, pain receptors, and pressure receptors.
Cutaneous Glands
are considered as exocrine glands, are located throughout the dermis
produce and secrete products that are delivered to the appropriate locations through ducts.
2 Basic Types of Cutaneous Glands:
Sebaceous Glands
are associated with hair follicles.
The sebaceous gland duct leads to the hair follicle surrounding the hair root.
Sebum, a very oily, lipid-rich substance, is produced by the sebaceous gland to moisturize the skin and hair. Sebum exits the hair follicle to the skin’s surface with the emerging hair. You can remove sebum from your skin by washing with soap
Lanolin - sebum from sheep
P. acnes bacteria produces acne
Salicylic acid helps reduce the shedding of cells that line the sebaceous gland and hair follicles.
Benzoyl peroxide destroys P. acnes and may reduce sebum production
Vitamin A derivatives called retinoids unplug comedones (plural of comedo) to allow other topical medicines to enter the follicle.
Sweat Glands
3 Types of Sweat Glands
Merocrine Sweat Gland
This is the most numerous type of sweat gland
deliver their sweat to the surface of the skin through a duct whose opening is called a pore.
They are located all over the body and are highly concentrated in the palmar and plantar regions.
Product - Watery sweat composed of 99% water, lactic acid, nitrogenous waste called urea, and some salt.
Function - Helps cool the body through evaporation.
Apocrine Sweat Gland
This type of sweat gland delivers its sweat through a duct leading to a hair follicle.
are associated with axillary hair, pubic hair, and the beard. They begin to produce their sweat at puberty.
Product - Lipid-rich sweat that bacteria feed on. It is not the sweat itself but the waste from the bacteria feeding on the sweat that creates body odor.
Function - Serves as scent to influence the behavior of others.
Ceruminous Sweat Gland
This is a modified sweat gland, only found in the ear.
Product - earwax
Function - Keeps the eardrum flexible, waterproofs the ear canal, kills bacteria, and protects the ear canal from foreign debris
Mammary Gland
This is a modified sweat gland found in the breast
begin to develop at puberty and fully develop during pregnancy. They deliver their product to ducts that end at the
Product - Breast milk, which is composed of water, carbohydrates, lipids, proteins, and minerals.
Function - Nourishes an infant.
Hair Follicle
Each hair follicle is positioned at an angle in the dermis with a dermal papilla at its base
The dermal papilla has a blood vessel, which feeds the keratinocytes and melanocytes contained in the hair follicle.
The keratinocytes produce the hair, while the melanocytes produce the hair’s pigment (color).
Active keratinocytes form the hair matrix just above the dermal papilla.
Dermal Papilla
is the hair’s growth center, and it contains important nerves and blood vessels that provide amino acids for keratin production
Arrector Pilli Muscle
This muscle attaches the hair follicle’s base to the epidermis at an angle. When this muscle contracts, it pulls on the hair follicle’s base, making the hair stand perpendicular (in an upright position) to the skin’s surface.
Hair
is present wherever there is thin skin on the body
Sections of the Hair
Bulb
thickening of the hair at the end of the hair follicle.
Root
extends from the bulb to the skin surface
Shaft
is the section of hair extending out from the skin surface
Matrix
growth zone of the hair bulb at the inferior end of the follicle
Medulla
central core of each hair
Cortex
surrounds the medulla
Cuticle
formed by a single layer of cells that overlap one another like shingles on a roof. It is the most keratinized region; it provides strength and helps the inner hair layers tightly compacted.
Three Types of Hair
Lanugo Hair
is very fine and unpigmented (colorless), forms on a fetus during the last 3 months of its development. This hair is usually replaced by birth.
Vellus Hair
which is also unpigmented and very fine, replaces lanugo hair around the time of birth.
Terminal Hair
is thick, coarse, and heavily pigmented, forms the eyebrows, eyelashes, and hair on the scalp. At puberty, terminal hair forms in the axillary and pubic regions of both sexes. It also forms on the face and possibly on the trunk and limbs of men.
Hair comes in a variety of sizes and shapes:
Hair shaft is oval, smooth and silky and the person has a wavy hair
Hair shaft is flat and ribbonlike, hair is curly and kinky
Hair shaft is perfectly round, the hair is straight and tends to be coarse
Epidermal Sheath
composed of epithelial tissues and forms the hair
Dermal Sheath
is dermal connective tissue that supplies blood vessels to the epidermal portion and reinforces it.
Cross Sectional Layers of Skin:
Inner Medulla
the central core, composed of soft keratin
Middle Cortex
surrounds the medulla, composed of hard keratin
Outer Cuticle
encloses the cortex, appears as interlocking scaly plates like shingles of the roof.
it is the most heavily keratinized region.
it provides strength and helps keep the inner hair layers tightly compacted.
Split Ends
a phenomenon in which the keratin fibrils in the inner hair region frizzes out.
Hair Cycle:
Anagen (growing)
the state which the grows (0.5 inch in a month). This phase can last approximately 3 years. It can be shorten through factors including stress and diet.
Catagen (detaching)
period of time which hair detaches from the blood vessels and dermal papilla.
Telogen (resting)
hair detached and resting in skin.
Catagen and Telogen lasts about 1 to 2 years
Exogen (shedding)
extension of telogen phase characterized by the shedding of telogen hair. The old hair sheds, new hair grows simultaneously and new anagen phase begins.
Hair Pigment
is made by melanocytes in the hair bulb, and varying amounts of different melanin (yellow, rust, brown, and black) combine to produce all varieties of hair color from pale blond to black.
Grey to White color
lack of melanin in the hair’s cortex and from the possible presence of air in the medulla.
it is perfectly fine to lose 50-100 hairs from your scalp everyday. NOT ALL of the hair undergo cycle on the same schedule.
Alopecia
or baldness, is characterized by an excessive loss of hair.
Nail
form on the distal end (away from the attachment point) of the fingers and toes.
scalelike modification of the epidermis that corresponds to the hoof or claw of the other animals.
Anatomy of a Nail:
Nail Root
found under the skin
Nail Plate
visible part of the nail
Free Edge - nail plate that extends out of the skin
Nail Body - nail plate on the surface of the skin.
Nail Bed
where the nail plate lies
Nail Fold
rise or bump of the skin over the nail’s lateral edge
Nail Groove
where the nail fits into
Cuticle or Eponychium
at the proximal edge of the nail body, is composed of stratum corneum cells extending unto the nail bed.
Nail Matrix
responsible for nail growth. it is composed of active keratinocytes in the stratum basale.
Lunula or Lunule - (white crescent) this is where the nail matrix is thick enough to hide blood vessels of the dermis deep to it.
Physiology of the Skin
1 square inch of skin you have on your own hand is typically composed of:
20 blood vessels
65 hairs and arrector pili muscles
78 nerve endings for heat
13 nerve endings for cold
160 to 165 sensors for pressure
100 sebaceous glands
650 sweat glands
19,500,000 cells
Function of the Skin:
Protection
Vitamin D Production
Temperature Regulation
Sensation
Non Verbal Communication
Water Retention
Pathophysiology of the Skin:
Regeneration vs. Fibrosis
Regeneration
the wound is healed with the same tissue that was damaged and normal function is returned
Fibrosis
the wound is healed with scar tissue and normal function is not returned.
Wound Contracture
A scab forms and pulls the edges of the wound closer together as it dries.
Keloid
is a raised scar that extends beyond the margins of the wound.
Burns
are a common skin injury. Heat damage
Types of Burns:
First Degree Burn
are the most common burns. Sunburns are often first-degree burns. Symptoms are redness, pain, and swelling.
Second Degree Burn
sometimes called partial-thickness burns, symptoms are redness, pain, swelling, and blisters.
Third Degree Burn
sometimes called full-thickness burns, are the most serious burns. The symptoms are charring and no pain. There is no pain at the site of a third-degree burn because all of the nerve endings have been destroyed in the dermis.
Diagnostic Test for Integumentary System:
Skin Biopsy
The removal of a piece of tissue or a sample of cells from a body so that it can be analyzed in a laboratory
Skin Scraping
The taking of skin cell scrapings so that the cells can be viewed under a microscope
Wood’s Light
The use of a black light to view pigment changes in the skin.
Integumentary System Disorders
Skin Cancer
is the most common type of cancer
is usually associated with sun exposure and it is more common in older, light-skinned people.
Basal Cell Carcinoma
is the most common form of skin cancer.
It starts in stratum basale cells and first appears as a small, shiny bump on the face, hands, ears, and neck. As it progresses, it develops a central depression and a pearly edge.
Squamous Cell Carcinoma
starts from keratinocytes in the stratum spinosum. First appearing as a red, scaly patch that develops a central crust, it commonly forms on the face, hands, ears, and neck.
Malignant Melanoma
is the rarest but deadliest form of skin cancer
It starts with melanocytes, usually in a preexisting mole. Malignant melanoma may be seen as a dark spot under a nail or as a mole that is asymmetrical and has uneven color and scalloped borders.
Bacterial Skin Infections
Impetigo
is an infectious skin disease caused by the bacterium Staphylococcus or Streptococcus. Impetigo appears as a cluster of vesicles, which are fluid-filled blisters that burst and crust over.
Cellulitis
commonly occurs on the face and lower legs, characterized by redness and swelling of an area of the skin that increases in size rapidly. The infected area has a tight, glossy appearance and is tender or painful.
Viral Skin Infections
Warts
are growths caused by an infection of the skin produced by the human papillomavirus (HPV).
Types of warts include common warts, plantar warts, genital warts, and flat warts.
Herpes Simplex Virus (HSV)
This virus is characterized by small, painful blisters that appear on the skin and on the mucous membranes of the mouth or genitals. Although these blisters eventually subside, the virus remains dormant in the body for life.
2 Forms of HSV:
HSV - 1
causes viral herpes infections seen on the lips or mouth.
HSV - 2
causes viral herpes infection on the genitals.
Herpes Varicella-Zoster Virus
another type of herpes infection, causes chicken pox in children and shingles in adults
Chicken Pox - is a common childhood disorder characterized by red, itchy, fluid filled vesicles or pox that appear on the skin. The rash is also accompanied by fever, headache, and malaise. Is contagious and can be contracted through direct or indirect contact.
Shingles - occurs in adults and is similar in appearance to chicken pox. It is characterized by small, painful vesicles that usually follow a path along an area of skin supplied by a spinal nerve.
Fungal Skin Infections
Tinea Infections
are caused by a fungus. Contact with an infected person, damp surfaces like shower floors or pool decks, or even pets can transmit the fungus.
Ringworms - is a circular rash that clears from the center, giving it a ringlike appearance.
Athletes Foot - causes burning, itching, and cracking of the skin between the toes.
Jock Itch - causes an itchy, burning rash in the groin region.
Onychomycosis - fungal infection of the nails.
Parasitic Skin Infections
Scabies
is a parasitic infection of the skin caused by an infestation of mites. Scabies causes small red bumps on the skin that itch severely.
Other Common Skin Disorders
Psoriasis
This is a common skin disease characterized by the overgrowth of skin cells and improper keratinization of the epidermis and nails. Is a hereditary autoimmune disorder that runs in families.
Dermatitis
is characterized by inflammation of the skin and may also show symptoms of redness, swelling, oozing, crusting, scaling, pimples or vesicles, and itching.
Contact Dermatitis - is inflammation of the skin caused by direct contact with a substance that can be categorized as either a skin irritant or one that causes an allergic reaction.
Atopic Dermatitis - also known as atopic eczema, is an allergic reaction that causes an infection. Can also cause the skin to have a leathery appearance and be discolored.
Hives
This skin condition, also known as urticaria, is a skin reaction that can be caused by insect bites or by contact with substances that cause an allergic reaction, such as certain foods or drugs. Symptoms of hives include raised areas of the skin, redness, and itching
Decubitus Ulcers
also known as pressure ulcers or bedsores. They are areas of nerotic or ulcerated tissue caused by the pressure of a bony prominence in the body and another surface.
Scleroderma
This disease involves the accumulation of excess connective tissue in the skin and various organs. It is characterized by increased collagen production in these connective tissues.