Integumentary System Flashcards
Integumentary system
Interface between the body and its external environment
Skin proper and its derivatives
Skin proper
2 main layers of the skin
Epidermis and dermis
Skin derivatives or appendages
Hair and nails
Sweat, sebaceous, and mammary glands
Epidermis
Upper layer of skin
Visible
Renewable population of keratinized stratified squamous cells
Made up of layers
Dermis
Lower layer of the skin
Dense regular and irregular fibrous CT containing sensory and motor nerve fibers
Consists of a papillary layer and a reticular layer
Hypodermis
Layer of white adipose and CT fibers underneath the dermis
Separates the skin proper from underlying muscle
NOT part of the skin
What are the layers of the epidermis?
- Stratum basale/germinativum
- Stratum spinosum
- Stratum granulosum
- Stratum lucidum
- Stratum corneum
Stratum basale/germinativum
Basal layer of epidermis
Gives rise to new cells at a constant rate
Some cells contain melanin
New cells move up as they differentiate
Stratum spinosum
Layer of epidermis above stratum basale
Cells have “spines” that come in contact with spines of other cells to form desmosomes called node of Bizzozero
Cells are keratinocytes
Cells and nuclei flatten as they move up from below
Stratum granulosum
Thin layer of epidermis above stratum spinosum
Cells are further differentiated
Cells have large granules called keratohyaline granules
Stratum lucidum
Thin layer of epidermis above stratum granulosum
Only found in thick skin
Cells are filled with aggregated keratin (clear appearance of cells)
Nuclei and organelles are broken down
Slowly dying cells due to lack of blood supply from the dermis
Stratum corneum
Uppermost layer of epidermis
Sloughs away
Renewed by cells coming up from the bottom layer
Keratohyaline granules
Large granules filled with the protein flaggrin that induces clumping of keratin
Increases waterproofing
Allowed evolution of aquatic to terrestrial animals
Found in keratinocytes of stratum granulosum
Melanocytes
Melanin-producing cells found in the epidermis
Derived from neural crest cells that broke off the neural tube and migrated to the skin
Melanin
Antioxidant with protective function
Protects against extreme temperature and chemical exposure; UV light radiation in the skin
2 types: eumelanin and pheomelanin
Eumelanin
Form of melanin
Brown
Most common form
Pheomelanin
Form of melanin
Red
Produced by some red-haired people
Not as common
Melanosome
Membrane-bound vesicle containing melanin
Found in melanocytes
How is melanin transferred to keratinocytes?
Keratinocytes phagocytize part of the melanocyte containing melanosomes, called cytokrine secretion
Melanocyte does not die
Langerhans cell
Stellate, APC found in the epidermis
Very active when skin is infected/exposed to infectious agents
Immunologically involved
Merkel’s cells
Cells found in the epidermis
Function is debated; may have something to do with mechanoreception
Dermatoglyphics
Genetically controlled pattern of the skin consisting of epidermal and dermal papillae
Unique to each person
Fingerprints
Papillary layer of the dermis
Upper layer, underneath the stratum basal of epidermis
Contains Meissners corpuscles
Reticular layer of the dermis
Lower layer of dermis, above the hypodermis
Contains Pacinian corpuscles
Meissners corpuscles
Encapsulated touch receptors found in dermal papillae
Pacinian corpuscles
Encapsulated pressure receptors found in the dermal reticulum
Also found in the pancreas and spleen
Consists of layers of concentric CT around a sensory nerve fiber
Encapsulated receptors
Receptors covered with CT or epithelial tissue
Loose function without capsule
Dermal sensory fibers
Free nerve endings that detect heat and cold
Dermal motor fibers
Autonomic innervation of dermis of skin, bv, swear glands, and arrector pili muscles
Anogen
Quick, active growth of a hair
Catogen
Brief period of cessation of hair growth
Telogen
Hair stops growing
Follicle atrophies and hair is lost
DHT
Dihydrotestosterone
Responsible for loss of vascularization of hair follicles, leading to hair death (telogen)
Arrector pili
Muscle that pulls on hair follicle to make it stand up
Vestigial in humans
Found in hairy mammals
Functions as a sympathetic response to make them look bigger in times of stress, and as an insulation against heat loss
Sebacceous gland
Secrete oil via holocrine secretion
Functions as a lubricant
Pilo-sebacceous apparatus
Hair follicle and sebaceous gland
Apocrine sweat gland
Apocrine secretion of pheromones and sweat
Thermoregulates in mammals but NOT in humans
Pheromones
Attraction hormones that affect the behavior of other organisms
Eccrine sweat glands
Thermoregulation
Development of this gland coincides with decreased hair in humans –> allowed us to be hairless
Nails
Accessory organ of the skin
Epithelial cells
Tyrosine
Essential amino acid that is the precursor to melanin
Lanula
Crescent-shaped structure of the nail
Capillaries are deeper so there is decreased blood flow and it appears lighter
