1/12 Howard Integument Flashcards
What are the components of the integument?
- Skin
- Glands
- Nails
- Hair
Largest organ of the human body
Skin
The skin makes up ___ of body weight
16%
The skin covers ____ of area
2 square meters
Two types of skin
- thick skin
- thin skin
Thick skin is present where there is or is no hair present?
No hair present
Thin skin is present where there is or is no hair present?
Where there is hair present (hair follicles defining structure)
What are the functions of skin?
- Barrier function (physical, chemical, biological assaults)
- homeostatic function
- excretory function sebaceous and sweat glands)
- secretory function (vitamin D synthesis)
- sensory function
BHESS
What are the components of barrier function of the skin?
- general wear and tear
- waterproofing
- immunological defense
- protection against UV radiation
What are the components of homeostatic function of the skin?
- hydration
- heat regulation
Epidermis is derived from ____, while the dermis is derived from ____
Ectoderm (entirely); mesoderm
Epidermis is composed of what kind of epithelium?
Stratified squamous keratinized epithelium
____ is composed of dense irregular connective tissue
Dermis
The hypodermis consists of:
Loose connective tissue and adipocytes
True or false: The hypodermis is technically part of the skin
False - it is not, it is the underlying superficial fascia
What cell types are found in epidermis?
- keratinocytes
- melanocytes
- Langerhans cells
- Merkel cells
The dermis consists of what layers?
- Papillary layer (loose CT)
- Reticular layer (dense irregular CT)
The papillary layer of the dermis consists of?
- collagen fibers
- elastic fibers
- fibroblasts
loose connective tissue
The reticular layer of the dermis consists of?
- hair follicles
- smooth muscle
- glands
- nerves
- blood vessels
dense irrecular CT (reticular fibers)
Where is thick skin found?
- sole of foot
- palm of hand
Thick skin - thickness in mm
0.5mm
Thin skin is found where?
Everywhere else on the skin (except areas of thick skin)
How thick is thin skin?
0.1mm
Distinguishing feature of thin skin
Hair follicles
What are the layers of thick skin?
- stratum corneum
- stratum lucidum
- stratum granulosum
- stratum spinosum
- stratum basale
What are the layers of thin skin?
- Stratum corneum
- stratum spinosum
- stratum basale
Thin skin does not have what two layers?
No clearly defined stratum lucidum or stratum granulosum layers
Main cell type of epidermis
Keratinocytes (95%)
True or false: there are more layers of keratinocytes in the stratum corneum layer of thin skin compared to thick skin
False - more in thick skin (~50 layers compared to just 5 in thin skin)
True or false: in thin skin, there may be cells of the stratum lucidum/stratum granulosum but the layer would appear very thin or discontinuous
True
Stratum corneum is also known as:
Cornified cell layer
Describe the stratum corneum
- dead, anucleated
- contains flattened keratinocytes (squames)
- 5-50 layers thick (thick/thin skin)
- shed from surface
Stratum lucidum is also known as:
Clear cell layer
Describe the components of stratum lucidum
- contains clear keratinocytes
- no nuclei
- filled with keratin
mainly in thick skin
Stratum granulosum is also known as:
Granular cell layer
Describe the stratum granulosum (5)
- 3-5 cell layers thick
- nucleated keratinocytes
- produce keratohyalin granules
- make membrane-coating granules
- have desmosomes
What does nucleated keratinocytes mean?
- cells are still alive
- beginning the process of becoming keratinized
stratum granulosum
____ produce keratohyalin granules in the stratum granulosum
Keratinocytes
Stratum spinosum is also known as:
Prickle cell layer
Describe the components of the stratum spinosum
- mature keratinocytes
- produce membrane-coating granules
- contain tonofilaments
- Langerhans cells present
____ is the thickest layer of the epidermis and is mitotically active
Stratum spinosum
_____ shows reduced thickness in thin skin
Stratum spinosum
Which layers of the epidermis produce membrane-coating granules?
- stratum granulosum
- stratum spinosum
The stratum spinosum has a prickly appearance due to:
Presence of numerous desmosomes connecting the cells
Stratum basale contains how many cell layers?
One
In the stratum basale, keratinocytes go from ___ to ____
Cuboidal to columnar
____ makes the basement membrane of the epidermis
Stratum basale
____ contains progenitor cells that undergo cell renewal to create all keratinocytes
Stratum basale
Where can you find melanocytes and Merkel cells?
Stratum basale
Intermediate filaments in epithelial cells are ____ proteins called _____
Keratin; tonofilaments
Intermediate filaments are _____ that provide ____
cytoplasmic protein structures; cell structure and tensile strength
Keratins make up ____ distinct proteins, form ____, and make up ____ of cornified cells
30; intermediate filaments; 85%
Bundles of tonofilaments form a _____
tonofibril
How many tonofilaments are needed to form a tonofibril?
8 keratin IFs
Keratohyalin granules are made up of:
- tonofibril
- proteins such as profilaggrin, loricrin, trichohyalin
assembly of IFs bundled with other proteins then become keratinized
Synthesis of keratin 5 and 14 occur in:
Stratum basale
Synthesis of keratin 1 and 10 occur in:
Stratum spinosum
In the stratum spinosum, ____ are formed and are enveloped in ____. ____ merge with ____ forming keratin
tonofilaments; keratohyalin; keratohyalin granules; tonofilaments
Apoptosis starts in what layer of the epidermis?
Stratum granulosum
Granular cells become cornified cells in what layer?
Stratum corneum (takes 2-6 days, nucleus lost)
Waterproofing of skin: ____ produce the hydrophobic barrier
Lipids
Waterproofing of skin: keratinocytes produce _____ called ____ which contain ____
membrane coated granules; lamellar bodies; glycophospholipids
Lipid contents of lamellar bodies are extruded in ____ which form a ____
Stratum granulosum; lipid envelope
____ + ____ produces compound cornified cell envelope
lipid envelope; cornified envelope
What is the internal aspect of cell membrane in stratum corneum?
Cornified cell envelope
True or false: keratinocytes are active in the immune response
True - capable of producing interleukins, colony-stimulating factors, interferons, tumor necrosis factors, platelet and fibroblast stimulating growth factors
Melanocytes are derived from:
Neural crest cells
Melanin is derived from:
Tyrosine
In melanocytes, ____ penetrate the stratum spinosum
Dendrites
Melanocytes manufacture ___ by organelles called ____
Melanin; melanosomes
Dark brown to black pigment
Eumelanin
Red pigment in red and blond individuals is called:
Pheomelanin
Melanosomes are ____ containing vesicles
Tyrosinase
Enzyme that converts tyrosine to melanin
Tyrosinase
Tyrosinase is activated by:
UV light
Process of melanin production
- Melanin excreted via dendritic processes into extracellular space
- Endocytosed by keratinocytes of the stratum spinosum
- Migrate to nuclear region of keratinocytes and form protective umbrella shielding nucleus/chromosomes from UV
True or false: once melanin is made by melanosomes, they remain to repeat the process of melanin production
False - melanosomes are eventually destroyed by lysosomes, then the process is repeated
UV ____ rates of darkening of melanin and ____ tyrosinase activity and melanin production
Increase; enhance
True or false: melanosomes are produced and excreted quickly
True
Melanosomes appearance in H&E stain
- seen and stored in keratinocytes (not melanocytes)
- clear cytoplasm
Densities of melanocytes are dependent on what components?
- density of vascularization
- proximity of blood vessels to surface
Fewer melanocytes are found in:
- insides of thighs
- undersides of arms and face
Skin color is produced by the amount of ____ not the number of ____
Melanin; melanocytes
Langerhans cells are primary sites of ___ infection
HIV
Langerhans cells are derived from:
Bone marrow
Where are langerhans cells found?
Stratum spinosum and all mucous membranes (ex. oral epithelium)
Langerhans cells are ____ cells and activate ____
Antigen presenting; T-cell circuit
To activate the immune response, Langerhans cells:
- phagocytose antigens
- migrate to lymph vessel of dermis to enter nearby lymph node
Langerhans Cell histiocytosis
Rare syndrome that involves tissue infiltration with mitotically active Langerhans cells
Langerhans Cell histiocytosis commonly develops in:
Children 1-3 years (but can develop at any age)
Langerhans Cell histiocytosis is more common in:
Boys (2:1 ratio boys to girls)
Langerhans Cell histiocytosis can damage ____ and form ____
Adjacent tissues; large lesions
Where are Merkel cells found in the epidermis?
Stratum basale (receptor portion)
Merkel cells in the skin are most abundant in:
Fingertips
Merkel cells contain ____ receptors
Mechanoreceptors/touch receptors
Merkel cells send mechanical stimulus from the ____ to axon terminals of ____
surface of the skin; free nerve endings
What are free nerve endings?
- simplest receptors, free dendrites of unipolar neurons
- respond to physical/chemical disturbance, perceived as pain
Dermis is derived from:
Mesoderm
Two layers of the dermis
- papillary layer
- reticular layer
Papillary dermis contains what kind of tissue?
Loose connective tissue
Papillary dermis forms ____ which interpose with epidermal ____
Invaginations of dermal papillae; pegs
Papillary layer of dermis contains:
- blood vessels
- lymphatics
- sensory receptors
What is the deepest layer of skin?
Reticular dermis
Reticular dermis contains what kind of tissue?
Dense irregular connective tissue
What fibers are found in dermis?
- Type I collagen
- elastic fibers
- reticular fibers
Reticular dermis contains:
- sweat glands and ducts
- hair follicles
- arrector pili muscles
- sebaceous glands
- sensory receptors
How does the skin keep the body warm?
- barrier of the epidermis
- insulating layer of adipose tissue from hypodermis
- insulating layer of hair
- vasoconstriction of blood vessels to reduce blood flow
How does the skin keep the body cool?
- sweat (protein secretion from coiled tubular sweat glands) - evaporates to cool the skin
- vasodilation of blood vessels to increase blood flow
Sweat glands: secretory cells are ____ in shape, and the ducts have ___
low cuboidal to columnar; stratified cuboidal epithelium
What types of sweat glands are found in the body?
- eccrine sweat glands
- apocrine sweat glands
Eccrine sweat glands are found:
Throughout the body, mainly dermis and hypodermis
Function of eccrine sweat glands
- thermoregulation
- excrete in a merocrine fashion (secretion of product into a lumen via exocytosis)
Eccrine sweat glands are stimulated via:
sympathetic nervous system
Where are apocrine sweat glands found?
- axilla
- areola of nipple
- anus
- external auditory canal
- eyelids
Apocrine sweat glands open into:
canals of hair follicles superficial to entry of sebaceous glands
____ with bacteria produce distinctive odors
Apocrine sweat glands (otherwise odorless)
____ thought to possibly be vestigial scent glands
Apocrine sweat glands
Sebaceous glands are found:
Throughout the body but not palms, soles and sides of feet
Sebaceous glands secrete:
Sebum (wax like substance containing cholesterol, triglycerides, cell debris)
Function of sebaceous glands
Maintenance of skin texture and hair flexibility
____ are influences by sex hormones and output increases after puberty
Sebaceous glands
In sebaceous glands feeding into hair follicles, what happens to cells?
Apoptosis/disintegrate to release cell contents
Skin, as a sensory organ, contains:
- Merkel cells (fine touch, mechanoreception)
- free nerve endings (pain)
- Meissner’s corpuscle (touch and pain)
- Pacinian corpuscle (pressure only)
Where is Meissner’s corpuscle found?
In the dermal papillae at the junction of epidermis and underlying connective tissue
Pacinian corpuscle is found in the ____ surrounded by ____
Hypodermis; fat cells
looks like onion layers
What muscle is associated with hair follicles?
Arrector pili muscles
What are freckles?
- Hyperpigmented spots primarily locates in sun exposed areas of the body
- increased melanin production and accumulation in stratum basalis
Freckles are demonstrated by:
3 years of age
Freckles do not result from:
Increase in number of melanocytes
Freckles tend to fade in:
Winter
What is psoriasis?
- patchy lesions
- hyperplasia of keratinocytes in stratum basale/spinosum
- accumulation of keratinocytes and abnormal growth of stratum corneum
True or false: in psoriasis, there is an accelerated cell cycle
True - may increase as much as 7x normal
Psoriasis lesions common on:
- scalp
- elbow and knees
- but can occur anywhere
Psoriasis is ____ but manageable ___ condition
Incurable; chronic
What are warts?
- benign epidermal growths
- epidermal hyperplasia thickens epidermis with scaling
- infection of keratinocytes with papillomaviruses
True or false: warts are not contagious
False - contagious due to papillomavirus
Warts are common in:
- children
- young adults
- immunosuppressed patients
Types of skin cancers
- basal cell carcinoma
- squamous cell carcinoma
- malignant melanoma
Most common human malignancy
Basal cell carcinoma
Basal cell carcinoma can occur due to
Exposure to UV radiation in cells of stratum basalis
____ do not metastasize but are destructive to local tissues
Basal cell carcinoma
Basal cell carcinoma can be fixed with:
Surgery (90% recover)
2nd most common skin cancer
Squamous cell carcinoma
Squamous cell carcinoma occurs in _____ and can ____
keratinocytes of epidermis; metastasize (locally invasive)
Squamous cell carcinoma can occur due to:
exposure to UV radiation, x-irradiation, soot, chemical carcinogens, arsenic
____ most prevalent in fair-skinned individuals
Malignant melanoma
True or false: prevalence is increasing in malignant melanoma
True
Malignant melanoma can occur due to:
Excessive exposure to sun (transforms melanocytes)
Malignant melanoma is the worst skin cancer because:
- metastatic, very invasive
- penetrates dermis and crosses basement membrane to enter lymphatic vessels and bloodstream to travel throughout body
