WEEK 2: Integumaentr Flashcards
what are the 2 types of skin?
thick (palm and sole), thin
what are some differences between thick and thin skin?
Thick skin has a thinner dermis than thin skin, and does not contain hairs, sebaceous glands, or apocrine sweat glands.
list functions of the skin. (6)
*Barrier: physical, chemical and biological agents
*Immunologic: antigen processing to the appropriate effector cells in the lymphatic system
*Homeostasis: body temperature and water loss
*Conveys sensory information: about the external environment to the nervous system
*Endocrine: secreting hormones, cytokines and growth factors and converting precursor molecules into hormonally active molecules vitamin D
*Excretion: sweat
what are the integument layers?
epidermis, dermis, hypodermis
what does the epidermis consist of?
consists of:
- stratified squamous keratinised epithelium
- several layers (stratum)
- melanin pigment – colour of skin
what does the dermis consist of?
blood/lymph vessels
appendages
nerves
sensory nerve endings
what does the hypodermis consist of?
(not considered part of the skin)
layer of the subcutaneous loose connective tissue
presence of adipose tissue
what are the 6 layers of the epidermis? come lets get sun burn ! CLGSB
1) stratum corneum - dead keratized cells
2) stratum lucidum - thick skin only, clear layer of dead skin cells
3) stratum granulosum - cells about to die
4) stratum spinosum - maturing and slowly dying cells, keratinocytes produce keratin filaments
5) stratum basale - stem cells that are capable of differentiation
which layer does not exist in thin skin?
stratum lucidum
how does the epidermis obtain nutrients?
there are no blood vessels in the epidermis, so cells get their nutrients from connective tissue below because the cells of this outermost layer are dead.
which layer does tattoo ink go to?
dermis
what cells comprise the epidermis?
Keratinocytes
Melanocytes
Langerhans
Merkel
what percentage of keratinocytes make up the epidermis?
~ 85%
where do keratinocytes originate?
stratum basale
what are the 2 essential functions of keratinocytes?
to produce keratins (cytokeratins)
to participate in the formation of epidermal water barrier
describe the life cycle of keratinocytes.
_ the basal cell layer origiinate new cells with keratin filaments
- as cells mature, they move upwards
- In the upper part of the spinous layer, the cells begin to produce keratohyalin granules and glycolipid-containing lamellar bodies to form the water barrier
- pH is low enough to digest desmosomal proteins promoting detachment of the most superficial layer of keratinocytes.
describe the process of epidermal cell differentiation. (4)
*Division of stem cells in the stratum basale.
*Newly formed cells move upward as they differentiate into keratinized cells.
*Keratinized cell are lost by exfoliation on the skin surface.
*The process takes 47 days and it is maintained in equilibrium (cell divisions vs cell loss)
how long is the normal epidermal turnover time?
~47 days
how long is the epidermal turnover time in psoriasis?
8 to 10 days
what is the main function of Merkel’s cells?
to detect touch sensations
where are Merkel cells most abundant?
where sensory perception is acute (fingertips)
what is a primary role of keratin filaments?
to resist chemical stresses and assist the cell in maintaining a polarized cytoarchitecture
describe the structure of the Merkel cell.
*Have desmosomes and contain keratin filaments
*Nucleus is lobed
*Cytoplasm contains neurosecretory granules
*Closely associated with the expanded terminal bulb of afferent myelinated nerve fibres = merkel’s corpuscle
what determines skin colour?
amount of melanin present
what ability do darken skin individuals show?
they have slower melanin degradation
what is the function of melanin?
to protect cells DNA against damaging effects of UV radiation.
what is albinism?
Inability of melanocytes to synthetize melanin
what is the inability of melanocytes to synthetize melanin called?
albinism
what is virtiligo?
The degeneration and disappearance of entire melanocyte
what is the the degeneration and disappearance of entire melanocyte called?
virtiligo
what is a melanoma?
Tumor formed by proliferation of melanocytes
how is a darker colour produced in the skin?
Increased number of melanocytes in a small area leads to increased production in melanin in the area
where do Langerhans cells originate?
common lymphoid progenitor (CLP)
what is the main function of Langerhans cells?
They are antigen presenting cells. They encounter, process and express antigens. Migrates to the lymph node to present the antigen to T-lymphocytes.
what are epithelial appendages?
Epithelial appendages are derivatives of epithelia that elaborate to form specialized structures and functions. They are outgrowths of the epidermis and extend into the dermis.
.what are the 3 epithelial appendages?
1.Hair follicle and hair
2.Nails
3.Glands
what is the function of the sebaceous gland?
to hydrate hair follicle. The sebaceous secretion is rich in lipid.
what does the pilosebaceous unit consists of?
the hair shaft, the hair follicle, the sebaceous gland, and the erector pili muscle
how is hair colour determined?
Colour is determined by the amount of melanin produced by the melanocytes in the bulb
what are the 3 layers of hair?
medulla (middle), cortex, cuticle (outer layer)
what kind of cells make up the cortex layer of the hair?
cuboidal cells undergo differentiation into keratin-filled cells
what kind of cells make up the cuticle layer of the hair?
squamous cells that form the outermost layer
the skin has 3 types of glands. These are…
*Sebaceous
*Eccrine(sweat)
*Apocrine (sweat)
where are eccrine sweat glands distributed?
they are distributed over the entire body surface. They are especially numerous in the thick skin of the hands and feet.
where are apocrine sweat glands distributed?
they are localized in the armpit and perineum.
what cells do nails consist of?
Hard plates of epidermal keratinized cells
what are the skin sensorial receptors?
free nerve endings
Merkel’s corpuscle
encapsulated nerve endings
what is Merkel’s corpuscle?
a dendritic cell for cutaneous sensation, such as the fingertips.
