integumentary system Flashcards
what are the 2 distinct layers
- epidermis
- dermis
what type of epithelium is the epidermis
keratinized, stratified squamous epithelium
what are the 3 types of cells that occupy the stratum basale
- keratinocytes
- melanocytes
- tactile cells
what is keratin
a tough and insoluble protein that strengthens the epidermis
what are the keratin proteins found in keratinocytes called
cytokeratins
what is the most abundant cell type in epidermis
keratinocytes
what are the functions of melanocytes
produce and store the pigment melanin in response to UV light
what are the granules in which cytoplasmic pigment transfer occurs in called
melanosomes
what 4 colours can the pigment of melanocytes appear
- black
- brown
- tan
- yellow-brown
how does pigment protect keratinocyte DNA
the pigment accumulates around the nucleus of the keratinocyte which shields the nuclear DNA from UV radiation
what does blocking UV light achieve
preventing mutations in keratinocyte DNA (in epidermis) and fibroblasts (dermis)
what is tactile cells also known as
merkel cells
where can tactile cells be found
scattered among the cells in the stratum basale
what do tactile cells do in response to touch
release chemicals that stimulate sensory nerve endings, providing info about objects touching the skin
in order of superficial to deep, what are the 5 layers of the epidermal strata
- stratum corneum
- stratum lucidum
- stratum granulosum
- stratum spinosum
- stratum basale
what are the 3 strata which are composed of living keratinocytes
- stratum basale
- stratum spinosum
- stratum granulosum
what forms the stratum spinosum
several layers of polygonal keratinocytes
what happens when a stem cell divides in the stratum basale
- a daughter cell is pushed to the stratum spinosum and begins to differentiate into a non-dividing, highly-specialized keratinocyte
- the other daughter cell remains in the stratum basale
what are desmosomes
membrane junctions which keratinocytes in the stratum spinosum use to attach to their neighbours
what’s the other cell is found in the stratum spinosum
epidermal dendritic cells (langerhans)
where can epidermal dendritic cells be located
in the stratum spinosum and granulosum
how many layers of keratinocytes is the stratum granulosum consisting of
3 to 5
what process begins in stratum granulosum
keratinization
describe the process of keratinization
keratinocytes fill up with the protein, keratin which causes the cell’s nucleus and organelles to disintegrate so the cell dies
when is keratinization complete
when the keratinocytes reach the more superficial epidermal layers
how many layers of keratinocytes are there in stratum lucidum
2 to 3
where is stratum lucidum found
thick skin
description of keratinocytes in stratum lucidum
flattened, pale cells
what translucent protein are keratinocytes filled with in the stratum lucidum
eleiden
where is eleiden produced
it’s an intermediate product of the process of keratin maturation
what does thick skin contain
sweat glands
what does thick skin not contain
hair follicles or sebaceous (oil) glands
what tissue is the papillary layer composed of
areolar connective tissue
what are the projections of the dermis called
dermal papillae
what do the epidermal ridges and dermal papillae do together
they increase the area of contact between 2 layers and interlock them
what do the capillaries in the dermal papillae do
supply nutrients to the cells of the epidermis
what connective tissue is the reticular layer consisting of
dense irregular connective tissue
how are collagen fibers structured in the reticular layer of the dermis
they are interwoven into a meshwork that surrounds structures in the dermis
how are collagen and elastic fibers in the skin oriented
in parallel bundles at specific body locations
what do the lines of cleavage do
identify the predominant orientation of collagen fiber bundles
what is the hypodermis
subcutaneous layer
what does the subcutaneous layer consist of
areolar connective tissue and adipose connective tissue
functions of the integument (7)
- protection
- prevention of water loss and water gain
- metabolic regulation
- secretion and absorption
- immune function
- temperature regulation
- sensory reception
what are the 3 types of epidermal derivatives
- nails
- hair
- exocrine glands
what are the 3 parts which form the nail plate
- free edge
- nail body
- nail root
what does the nail body cover
- a layer of epidermis called the nail bed
what are the 3 types of hair
- lanugo
- vellus
- terminal
what stimulates to ‘raise hair’
arrector pili
4 functions of hair
- protection
- heat retention
- sensory reception
- visual identification
what are the 2 most common types of exocrine glands
- sweat glands
- sebaceous glands
