A&P Chapter 5 Flashcards
What is the epidermis?
The superficial region of the skin.
What does the epidermis consist of?
Epithelial tissue, and is avascular
Where is the dermis?
Underlies the epidermis
What does the dermis consist of?
Fibrous connective tissue, and is vascular
What is another name for the hypodermis?
Superficial fascia, SubQ layer
Where is the hypodermis?
Subcutaneous layer deep to the skin
Is the hypodermis part of the skin?
No
What is the hypodermis made of?
Adipose tissue that absorbs shock and insulates
What does the hypodermis do?
Anchors skin to underlying structures: mostly muscles
What tissue does the epidermis consist of?
Mostly keratinized stratified squamous epithelium
What are the four cell types found in the epidermis?
Keratinocytes, Melanocytes, Langerhands/Dendritic cells, and tactile cells
What are keratinocytes?
Cells that produce fibrous keratin, and is the main cell type of the epidermis that is tightly packed
What is keratin?
A protein that gives skin its protective properties
What are melanocytes?
Cells that produce the pigment melanin, which is packaged into melanosomes
Melanosomes are transferred to ______
Keratinocytes, where they protect the nucleus from UV damage
Where are melanocytes found in the skin?
The deepest epidermis
What are tactile cells?
Sensory receptors that sense touch
The epidermis consists of _________ distinct layers
Four or five
Thick skin contains ______
five layers (strata)
Where is thick skin found?
High abrasion areas (hands/feet)
Thin skin contains ____ layers
Four
What are the five layers of skin, deep to superficial?
Stratum Basale –> Stratum spinosum –> Stratum granulosum –> Stratum lucidum –> Stratum corneum
Which layer of skin is only in thick skin?
Stratum Lucidum
What is the stratum basale
Basal layer, which is the deepest of all of the epidermal layers. It is firmly attatched to the dermis
What does the stratum basale consist of?
Single row of stem cells that actively divide, producing two daughter cells each time
How long does it take a daughter cell to go from basal layer to the surface?
25-45 days
The daughter cell _____ as it reaches the suface
Dies
Where does the other daughter cell remain?
In the stratum basale as a stem cell
What is the stratum basale composed of?
Mostly keratinocytes, 10-25% of the layer is composed of melanocytes and tactile cells
What is the stratum spinosum also called?
The prickly layer
What is the stratum spinosum?
Layer of the skin that is several cell layers thick
What do cells in the stratum spinosum contain?
Weblike system of intermediate prekeratin filaments attached to desmosomes. This allows them to resist tension and pulling
How do keratinocytes appear in the stratum spinosum?
Spikey, which is why they are called prickle cells
What is scattered among keratinocytes in the stratum spinosum?
Abundant melanosomes and dendritic cells
What is the stratum granulosum?
A layer of the cell that is four to six cells thick. The cells are flattened so the layer is thin
How does the cell appearance change in the stratum granulosum?
Cells flatten, nuclei and organelles disintegrate, keratinization begins, cells accumulate lamellar granules
What are lamellar granules?
A water-resistant glycolipid that slows water loss
In the stratum granulosum, cells above that layer _____
Die, they’re too far from dermal capillaries to survive
What is the stratum lucidum consisted of?
Thin, translucent band of two to three rows of clear, flat, and dead keratinocytes. Also filled with eleidin
What is eleidin?
Translucent protein that is an intermediate in keratin maturation
What is the stratum corneum?
20-30 rows of flat, anucleated, keratinized dead cells
The stratum corneum accounts for _______ of the epidermal thickness
Three quarters
Even though the cells are dead in the stratum corneum layer, they still function to
Protect deeper cells from the environment, prevent water loss, protect from abrasion and penetration, and act as a barrier against biological, chemical, and physical assaults
Cells change by going through ______
apoptosis
Dead cells come off as ______
Dandruff and dander
Humans can shed _______ cells every minute
~50,000 cells every minute
What is the dermis?
The strong flexible connective tissue
What cells are included in the dermis?
Fibroblasts, macrophages, and occasionally mast cells and white blood cells
Fibers in the matrix _____ the body together
Binds
The dermis contains
Nerves, blood vessels, lymphatic vessels, epidermal hair follicles, oil glands, and sweat glands
What are the two layers of the dermis?
Papillary and reticular
What is the papillary layer of the dermis?
The superficial layer of areolar connective tissue
Loose fibers allow phagocytes to ______
patrol for microorganisms
What is the dermal papillae?
The superficial region of the dermis that sends fingerlike projections into the epidermis
What do the protections contain?
Capillary loops, free nerve endings, and touch receptors
What are touch receptors also called?
Tactile corpuscles
What are friction ridges?
In thick skin, dermal papillae lie on top of thermal ridges, which give rise to epidermal ridges. Collectively, ridges are called friction ridges
What do friction ridges do?
Enhance gripping ability, contribute to sense of touch
Sweat pores in ridges leave a _____
unique fingerprint pattern
How much of the dermal thickness does the reticular layer make up?
~80%
What does the reticular layer consist of?
Coarse, dense irregular connective tissue
Elastic fibers provide ______
stretch-recoil properties
Collagen fibers provide ______
Strength and resiliency. They bind water and keep the skin hydrated
What is the cutaneous plexus?
A network of blood vessels between reticular layer and the hypodermis
The extracellular matrix contains ______
Pockets of adipose cells
Where are cleavage lines?
Reticular layer
What are cleavage lines also called?
Tension lines
What are cleavage lines caused by?
Collagen fibers running parallel to the skin surface
Cleavage lines are _____
Externally invisible, and important to surgeons because incisions parallel to cleavage lines heal better
Where are flexure lines?
Reticular layer
What are flexure lines?
Dermal folds at or near joints
The dermis is ______ to deeper structures in flexure lines
Tightly secured
How are flexure lines formed?
The skin’s inability to slide easily for joint movement causes deep creases
Flexure lines are visible on _____
Hands, wrists, fingers, soles, and toes
The SubQ layer is
Not part of the integument, and is made of adipose connective tissue
The functions of the SubQ layer are
Pads and protects body, acts as an energy reservoir and provides thermal insulation
Which layer of the skin is a site for drug injection?
SubQ
What are the three pigments that contribute to skin color?
Melanin, carotene, and hemoglobin
What is melanin?
The only pigment made in the skin, made up of melanocytes
Melanin are packaged into ______
melanosomes that are sent to shield the DNA of keratinocytes from damaging UV sunlight
If there’s more sun, more protection needed so ____ melanin will be produced
More
What are the two forms of melanin?
Reddish yellow to brownish black
Skin color differences are from
The amount and form of melanin
Freckles and pigmented moles are ____
Local accumulations of melanin
What is carotene?
Yellow to orange pigment acquired from yellow-orange vegetables
What is hemoglobin?
Pinkish hue of fair skin that is due to lower levels of melanin and hemoglobin binding of oxygen
Alterations in skin color can indicate _____
Disease
What is cyanosis?
Blue skin color, from low oxygenation of hemoglobin
What is pallor?
Blanching or pale color
What does pallor indicate?
Anemia, low blood pressure, fear, and anger
What is erythema?
Redness
What does erythema indicate?
Fever, hypertension, inflammation, and allergy
What is jaundice?
Yellow cast
What does jaundice indicate?
Liver disorders
What is the hair bulb?
Expanded area at the deep end of the follicle
What is the hair follicle receptor?
Sensory nerve endings that wrap around the bulb
What are hair follicle receptors also known as?
Root hair plexus
Is hair a sensory touch receptor?
Yes
What is a hair matrix?
Actively dividing area of bulb that produces hair cells.
As the matrix makes new cells, it __________
pushes older ones upward
What is the arrector pili, and what is it responsible for?
Small band of smooth muscle attached to follicle, responsible for goose bumps
Hair pigments are made by ______
Melanocytes in hair follicles
What creates all the hair colors?
Combinations of different melanins (yellow, rust, brown, and black)
What is additional in red hair?
Pheomelanin pigment
What is gray/white hair resulted from?
When melanin production decreases and air bubbles replace melanin in shaft
What is male pattern baldness caused by?
Follicular response to DHT
What’s DHT?
Dihydrotestosterone
What do nails act as?
Protective cover for distal and dorsal surface of fingers and toes
What is the nail matrix?
Thickened portion of bed responsible for nail growth
All skin surfaces except _____ contain sweat glands
The nipples and parts of external genitalia
About how many sweat glands does a person have?
3 million
What are the two main types of sweat glands?
Eccrine (merocrine) and Apocrine
What are ceruminous glands?
Lining of external ear canal
What do mammary glands do?
Secrete milk
What are the eccrine sweat glands function?
Temperature control, and some antibacterial properties
What is the type of secretion in eccrine sweat glands?
Hypotonic filtrate of blood plasma
What is the method of secretion for eccrine glands?
Merocrine (exocytosis)
Where does the secretion exit the duct at in eccrine glands?
Skin surface
Where are eccrine glands?
Everywhere, but especially palms, soles, and forehead
What do apocrine sweat glands function as?
Sexual scent glands
What is the type of secretion in apocrine sweat glands?
Filtrate of blood plasma with added proteins and fatty substances
What is the method of secretion for apocrine sweat glands?
Meocrine (exocytosis)
Where does the secretion exit the duct at in apocrine sweat glands?
Usually the upper part of the hair follicle, and rarely at the skin surface
Where are apocrine sweat glands located?
Mostly axillary and anogenital regions
What are the functions of sebaceous glands?
Lubricates skin and hair, helps prevent water loss, and antibacterial properties
What is the type of secretion for sebaceous glands?
Sebum (an oily secretion)
What is the method of secretion for sebaceous glands?
Holocrine
Where does the secretion exit the duct at in sebaceous glands?
Usually the upper part of the hair follicle, and sometimes the skin surface
Where are sebaceous glands located?
Everywhere except palms and soles
Skin is first and foremost a _____
Barrier
What are the main functions of the skin?
Protection, body temperature regulation, cutaneous sensations, metabolic functions, blood reservoir, and excretion of wastes
How does skin protect?
Constitutes three barriers, chemical (antimicrobials, sebum, low pH), physical, and biological (phagocytes)
How does the skin regulate body temperature?
Change in vessels and perspiration
What are cutaneous sensations
Sensing pain
What are metabolic functions of the skin?
Synthesize vitamin D, activate hormones, and stimulate collagen
The skin can hold up to ______ of the body’s total blood volume
5%
The skin can secrete _______ of ______ wastes
Limited amounts of nitrogenous wastes, such as ammonia, urea, and uric acid
Sweat causes the loss of ______
Salt and water
Most skin tumors are _______ and do not _______
Benign, and do not metastasize
Risk factors for skin cancer are
Overexposure to UV radiation and frequent irritation
What are the three major types of skin cancer?
Basal cell carcinoma, squamous cell carcinoma, and melanoma
What is basal cell carcinoma?
Least malignant and most common, stratum basale cells proliferate and slowly invade dermis and hypodermis. Cured by surgical excision in 99% of cases
What is squamous cell carcinoma?
Second most common type, can metastasize, involves keratinocytes of stratum spinosum, usually is a scaly reddened papule on scalp, ears, lower lips, or hands. Has a good prognosis if treated by radiation therapy or removed surgically
What is melanoma?
Cancer of melanocytes, it is the most dangerous type because it’s highly metastatic and resistant to chemotherapy. Treated by wide surgical excision accompanied by immunotherapy
The key to survival of melanoma is early detection, what is the ABCD rule?
A = Asymmetry, the two sides of the pigmented area do not match B = Border irregularity, exhibits indentations C = Color, contains several colors D = Diameter, larger than 6mm
What is the immediate threat for burns?
Dehydration and electrolyte imbalance
Where is the damage in first-degree burns?
Just the epidermis
Where is the damage in second-degree/partial-thickness burns, and what appears in this type of burn?
The epidermis and upper dermis. Blisters appear
Where is the damage in third-degree/full-thickness burns and what is usually needed for these burns?
All layers of the skin are damaged, and skin grafting is usually necessary
What is special about third-degree burns?
They are not painful because nerve endings are destroyed
When is a fetus’ skin developed?
By the end of the 4th month
What is the lanugo coat, and when does it appear in a fetus’ development?
Delicate hairs that appear in the 5th and 6th month
