Skin Anatomy and Function Flashcards
Skin is divided into two fundamental types
Glabrous (hairless)
Nonglabrous (hair bearing)
Primary feature of glabarous is what
The presence of arteriovenous anastomosis
Allows for shunting of blood from the periphery to the core during exposure to cold
Skin is home to what type of cells
Langerhan
Langerhan cells are considered to be what
antigen presenting cells
they find pathogens that have invaded the dermis and present these to lymphocytes for destruction
Largest sensory organ
skin
Vit D is needed for what
Bone health
Immune function
Cell growth
neuromuscular health
What triggers vit D synthesis
UV
UVB
Vit D synthesis
Skin contains 7-dehyfroxycholesterol which converts to Vit D3 when exposed to sunlight
THe inactive compound is then acted on by the liver and then the kidney to transform it into vit D
Main layers of the skin
Epidermis
Dermis
Subcutaneous tissue
Epidermis
outer layer of skin
composed of 5 layres
thickness varies
continues to thicken into 40s and then starts to thin
Epidermis - turnover
14 to 21 days
Epidermis - primary cell type
keratinocyte
Dermis
made of 2 layers
thickest component of the skin
Dermis - primary cell type
fibroblast, also contains mast cells, macrophages, lymphocytes
Dermis - Extracellular matrix of the dermis is primarily
collagen (the rest is elastin)
Dermis - what percent is collagen and why
90% - improves integrity, anchoring, and general skin strength
Subcutaneous tissue -
adipose cells
Keratinocytes
Squamous cells
Synthesize keratin
Keratin
a protein that is the primary structural component of skin, hair, and nails
Keratinocytes - migrate from where to where
from the stratum basale through to the stratum corneum
Takes about 28 days and at this point thery are anucleated and dead - they then act as a moisture barrier
Desmosomes
a type of junctional connection between keratinocytes holding them together
They do not exist in cancers - that is why cells are more able to metastasize
Melanocytes
account for the pigmentation of skin
Dendritic cells that supply melanin, via melanosomes, to the cells around them
Melanocytes are found where
Found in basal layer of epidermis within hair follicles
Melanocytes - Account for what percent of cells in epidermis
5%
1 melanocyte to every 35 keratinocytes
Melanomas originate from
melanocytes
Skin tone and pigmentation are related to
the size and amount of melanosomes
the amount of melanin is greater in darker pigmented skin (the number of melanocytes is the same though)
Langerhan cells - what are they
part of immune system
They are mobilized by antigens produced by various substances that make contact with the skin
Cell takes up the antigen and moves it into the lymph system
What is a postulated theory about Langerhan cells
A dysfunction of their migration may be involved in development of psoriasis
Merkel cells are part of the
sensory system
Merkel cells are located where
in the basal portion of the epidermis
connect to the sensory nerve fiber located in the dermis layers of the skin
Merkel cells are considered to be
slow adapting touch receptors
often grouped in clusters - they are the site of a rare aggressive cancer called merkel cell carcinoma
Basement membrane does what
Anchors the erpidermis and dermis via hemidesmosomes
Basement membrane is primarily composed of
collagen fibers
Blisters generate secondary to frictional forces at this level!
Basement membrane - what is located here
Terminal nerve endings - unmyelinated C fibers (slow pain)
Myelinated A delta fibers (sharp acute pain)
unmyelinated C fibers respond to
mechanical, thermal and chemical induced pain
Myelinated A delta fibers respond to
sharp acute pain
respond to pressure and cold
Aging does what to basement membrane
flattens and dec level of contact between the dermis and epidermis - this is what the basement membrane is responsible for controlling - increases the risk of separation (skin tears)
Genetic skin disorders sometimes occur in this layer as well
What is the thickest part of the skin
Reticular layer of the dermis
Upper part of the dermis AKA
papillary layer
Lower part of the dermis is AKA
reticular layer
Papillary dermis
Collagen and reticular fibers
loose CT
Thin, very vascular, well hydrated
Papillary dermis projects into
the epidermis giving unique patterns to the skin (fingerprints)
Papillary dermis - primary function
cushion
Reticular layer -
accounts for 80% of the thickness of the dermis
Highly structured irregular dense CT
Contains dermal appendages
Reticular layer - functions
shock absorber
Subcutaneous tissue AKA
hypodermis
Subcutanous tissue - thickness
Varies according to location mostly loose CT (aerolar tissue) Fat cells (adipocytes) - cushion, storage, insulation Collagen - fascia Blood vessels
Dermal appendages - sensory nerves
Meissner, Pacini, and Rafiini
Non of these extend into epidermis
Free nerve endings do extend into the lower epidermis - they amplify pain and temp signals
Dermal appendages - sebaceous glands
Exocrine glands
not found in palms, soles, dorsum of feet
Provide - moisture with their oily, waxy secretion of sebum
Associated with hair follicles - allows sebum to travel along follicles to reach skin surface
Dermis appendages - hair follicle - function
Lined with erpidermal cells that go deep into the dermis
Offer source of epithelization in partial thickness injuries
Provide route for flow of sebum
Dermis appendages - sweat gland - two types
Eccrine
Appocrine
Dermis appendages - sweat gland - eccrine
ALL areas of skin
deposit water/Na mixture onto skin surface
Acts as temp regulator in warmer environments
Dermis appendages - sweat gland - apocrine
Found in axilla, perineal and ubic areas, genitalia, nasal flares, eyelids
Inactive until puberty
Excrete protein rich secretions into hair follicles in that area
Odorless until microbial activity and then will smell
