Integumentary System Flashcards
2 layers of skin
Epidermis
Dermis
Is the hypodermis part of the skin?
No
Main functions of the skin
Protective
Immunological (has APCs)
Sensory
Exocrine (sweat, apocrine, sebum, mammary glands)
Endocrine (vitamin D synthesis)
Homeostasis (thermoregulation, water conservation, gas exchange, excretion)
Communication
Eccrine sweat glands
Throughout skin
Excrete water, salt, urea
Critical for cooling the body
Soles of feet and palms of hands - also underarms, groin, and forehead
Apocrine sweat glands
Axilla and groin only Develop during puberty Secrete water and lipids (glycoproteins) Break down the organic compounds in sweat causing body odor Pheromones for signalling
Sebaceous glands
Associated with hair follicles
Secrete oils that coat the hair and skin
Protective film
Sebum composed of lipids, triglycerides, waxes, squalene, cholesterol and cell remnants
Secretion controlled by testosterone/androgens
Langerhans cells
Immune cells responsible for picking up pathogens
Merkel cells
Nerve cells responsible for sensation
What are the only type of nerve endings in the epidermis?
Unencapsulated (free) nerve endings
5 layers of the skin
Stratum corneum S lucidum S granulosum S spinosum S basale
Thick skin
Made up of all 5 layers
Restricted to palms of hands and soles of feet
Lacks hairs and has abundant sweat glands
S spinosum is also thick
Thin skin
No stratum lucidum
Has hairs
Covers the rest of your body
S granulosum and corneum are pretty thin
Turnover of skin involves..
Cell renewal (mitosis)
Differentiation
Cell death
Exfoliation (sloughing off)
Stratum basale
Also called stratum germinativum Basal cell layer of epithelia Rests on basal lamina Single layer of columnar cells Has mitotically active keratinocytes, melanocytes, and Merkel cells
Melanocytes do not have..
Desmosomes
But they do have hemidesmosomes
Desmosome Structure
Adaptor proteins attach keratin filaments to the cytoplasmic plaque
Transmembrane linkers connect adjacent cells
Keratin filaments are also known as… (2 names)
Tonafilaments
Intermediate filaments
Stratum spinosum
Cuboidal to squamous cells with central nuclei
Contains aggregates of keratin called tonafilaments
Responsible for mechanical strength of epidermis
Variable number of cell layers depending on location
Malpighian layer
Includes the stratum basale and stratum spinosum
Nearly all the mitotic activity in the epidermis occurs here and cell division occurs only at night
Stratum granulosum
Keratinocytes mostly squamous
Contain membraneless keratohyalin granules in this layer
2 types of granules
Keratohyalin granules (membraneless) Lamellar granules (membrane)
Lamellar granules
Fuse with the plasma membrane and release their GAGs and phospholipids into intercellular spaces
May be important in sealing the deeper layers of the skin
Stratum lucidum
Only in thick skin
Narrow, acidophilic translucent band of flattened keratinocytes whose nuclei, organelles, and intercellular borders are not visible
Stratum corneum
Many layers of dead, plate-like keratinocytes with thickened plasma membranes
No nuclei
Filled with mature keratin
Permeability barrier
What layer do the nuclei begin to disintegrate in?
The outer layer of the stratum granulosum
Where are melanocytes found?
Stratum basale
Their dendrites go into the spinosum
Attached to basal lamina by hemidesmosomes
No desmosome attachment to keratinocytes
Highest concentration is found where?
In the cells that are more deeply localized because those are the cells that divide more rapidly
What has an impact on skin colour
Melanin and carotene
Thickness of the epidermis
Number of dermal blood vessels
Color of the blood (hemoglobin) in those vessels
Melanin
Brown-black pigment formed in cells called melanocytes
Amount of melanin is based on inheritance
Hemoglobin
Molecules found in RBC that gives blood its red coloraton
It is made of non-protein (heme which contains iron)
and the protein (globin)
Carotene
Yellowish pigment found in corneum and dermis
Plant pigment that enters the body via foood
Helps yield the yellow and red skin colors
Albinism
Condition where skin does not produce melanin
2 step process of tanning
- Physiochemical reaction darkens preexisiting melanin and releases it rapidly into the keratinocytes
- Higher rate of melanin synthesis by melanocytes, increases the amount of melanin
UVB vs UVA
UVA penetrates deeper into the dermis and damages dermal components
Promotes skin aging
Aging skin has…
Thinner epidermis and dermis
Disorganization
Loss of collagen
Reduced vascularization
Vitamin D synthesis
UVB required to activate 7-dehydrocholesterol in the epidermis to form pre-vitamin D
Langerhans cells
Star shaped immune cells
Occur mainly in the stratum spinosum
APCs that process and present to the lymphocytes any antigenic material that penetrates the skin’s surface
SALT
Skin associated lymphoid tissue
Merkel cells
Few in number
Found in basal layer of epidermis
Form macula adherens junctions with keratinocytes
Cells contain small dense granules similar to neuroendocrine cells
Function thought to be sensory or neuroendocrine in nature
Glabrous skin
Thick skin
Merkel cell is in close apposition to a plate like nerve ending from a neuron
Interpapillary peg
Narrow downgrowth of the epidermis
Divides dermal ridge into 2 secondary dermal ridges
Dermis
Vascular connective tissue
Variable thickness over different regions
Much thicker than the overlying epidermis
4 cell types found in the dermis
Fibroblasts
Lymphocytes
Macrophages
Mast cells
3 typical structures found in the dermis
Sweat glands
Sebaceous glands
Hair follicles
Most arise from the epidermis
2 dermal layers
Papillary layer
Reticular layer
Papillary dermal layer
Uneven and forms dermal papillae which increases contact area with the epidermis
Composed of loose CT
Mainly collagen type 3
Smally immature elastic fibers
Contains capillary loops and Meissner corpuscles which are fine touch receptors
Reticular dermal layer
Dense irregular connective tissue
Gives skin overall strength and elasticity
Mainly collagen type 1
Larger elastic fibers
Houses glands and hair follicles
Rich supply of nerves in both free and encapsulated endings
Shunts to control blood flow
Arteriovenous anastomoses
In reticular dermal layer
Control the amount of blood reaching the papillary capillaries, aiding in regulating heat loos and blood pressure
Hypodermis
Subcutaneous layer or fascia Not a true layer of skin Links skin to body proper Variable thickness in different regions of the body Allows for movement of skin over body Full of adipocytes More nerve endings Contains the lymphatics
Hair follicle
Invagination of the epidermis extending into the dermis
Hair shaft
In the center of the follicle
Extends above the surface of the epidermis
Consists of an inner medulla, cortex, and outer cuticle of the hair
Hair bulb
Terminal expanded region of the hair follicle in which the hair is rooted
Internal vs external root sheath
Internal: lies deep to the entrance of the sebaceous gland
External: direct continuation of the surrounding malpighan layer of the epidermis
Glassy membrane
Noncellular layer
Thickening of the basement membrane
Separates the hair follicle from the surrounding dermal sheath
4 types of hair
Lanugo: neonatal, fine, soft hair with no medulla
Vellus: post-natal, short, fine shaft, no medulla
Intermediate: post natal to 2 years
Terminal: post natal and on, long, course shaft, medullated (pigmentated), most common
Nail root
Stratum basale and spinosum of epidermis
Forms nail matrix whose cells synthesize the nail plate or body
Nail bed
Stratum basale and spinosum of nail
Does not contribute to nail synthesis
Nail plate
Closely compacted, keratin enriched with hard interfibrillar material
Stratum corneum of the nail
Eponychium
Cuticle
Junction between skin and stratum corneum and base of the nail plate
3 glands in the skin
Eccrine sweat glands
Apocrine sweat glands
Sebaceous glands
Mammary gland
Modified apocrine sweat glands
Milk producing glands that develop during pregnancy and lactation
Functional unit of breast tissue
Terminal duct lobular unit
Meissner’s corpuscle
Encapsulated unmyelinated nerve ending in the dermal papilla of skin
Senses deformation of skin
Rapidly adapting
Throughout skin, but concentrated in areas sensitive to light tough
Pacinian Corpuscle
Lie deep in the dermis, and hypodermis
Present in some mucous membranes and joints
Mechanoreceptors
Respond to pressure or any kind of mechanical stimulus
Contact hypersensitivity
Due to allergic reaction to chemical or compound
Hapten specific T cell recognizes the hapten in the skin and causes cell injury = inflammation
Psoriasis
Chronic, reoccuring skin disease
Produces red, scaly, well defined, patches affecting any part of the skin on your body
Areas in inflammation and excessive skin production
- Hyperkeratosis
2. Parakeratosis
- Thickening of the stratum corneum
2. Retained nuclei in the stratum corneum
Ehlers-Danlos syndrome
Rare genetic disorder Caused by defective collagen synthesis Fragile skin Hyperextensible joints Can affect organs
Bullous pemphigoid
Chronic blistering of the skin
Generally in the elderly
Autoimmune disorder
Caused by loss of attachment of basal keratinocytes to the underlying basement membrane
Associated with deposition of immunoreactants at the dermal-epidermal junction
Vitiligo
Loss of skin colour
Melanocytes are being destroyed or not functioning properly
ABCDEs of skin cancer
A: asymmetry B: border C: colour D: diameter E: evolving
Skin cancer is caused/associated with chronic inflammation of the skin from things such as… (3)
- Sunburn or excessive sun damage, especially early in life (both UVA/B)
- Chronic non healing wounds, especially burns
- Genetic predisposition, including Congenital Melanocytic Nevi Syndrome
3 most common types of skin cancer and where the originate from
Basal cell carcinoma: stratum basale keratinocytes
Squamous cell carcinoma: stratume spinosum, squamous keratinocytes
Melanoma: malignant, stratum basale melanocytes
Where are most breast cancers from?
The ducts
Epithelial mesenchymal transition
When the breast cancer cells get the ability to invade out of the duct
Desmosomes vs Hemidesmosomes
D: linker protein is cadherin
H: linker proteins are integrins
