The Structure and Function of the Skin Flashcards
Where is the epidermis?
The outer layer
Describe the epidermis
Stratified cellular epithelium
Where is the dermis?
Beneath the epidermis
Describe the dermis
Connective tissue
Where does the epidermis come from and how does it form?
Ectoderm cells form a single layer periderm. This gradually increases in layers of cells and the periderm cells cast off
How is the dermis formed?
From mesoderm below ectoderm
What are melanocytes
Pigment producing cells
Where do melanocytes migrate from
The neural crest
What 5 things does the skin consist of?
Epidermis Appendages Dermo-epidermal junction Dermis Sub-cutis
Give 4 examples of Appendages
Nails
Hair
Glands
Mucosae
What is the majority of the epidermis made up of and what does it contain?
keratinocytes. It contains structural keratins
What are the 4 types of epidermal cell layers
Keratin
Granular
Prickle cell
Basal
How is the regulation of epidermal turnover controlled
Growth factors
Cell death
Hormones
In what two scenarios is there a loss of control in the epidermal turnover
Skin Cancer
Psoriasis
Histologically, what happens to the cells in psoriasis
They migrate
Where do keratinocytes migrate from?
The basement membrane
How thick is the basal layer
One cell thick
What type of cell makes up the basal layer
Small cuboidal
What is the main feature of the basal layer
It is highly metabolically active
What are there lots of in the prickle cell layer
desmosomes (connections)
What connects to desmosomes
Intermediate filaments
What is the granular layer made up of
2-3 layers of flatter cells
High lipid content
What is unusual about the cells in the granular layer
Cell nuclei are lost
What is the main function of the keratin layer
To provide a tight waterproof barrier to keep you from losing water
What common skin disease affects keratinocytes and what does it cause?
HPV - causes warts
Where are the mucosal membranes in the body
Eyes Mouth Nose Genito-urinary tract Gi tract
What are the 3 other types of epidermal cells
Melanocytes (basal & suprabasal) Langerhans cells (suprabasal) Merkel cells (basal)
At what stage do melanocytes migrate from the epidermis to the neural crest
In the first 3 months of foetal development
What are the organelles called that melanocytes contain
Melanosomes
What is the function of melanocytes
To convert tyrosine to melanin
What absorbs light
Melanin
How are melanosomes transferred to adjacent keratinocyte
Via dendrites
What do melanin caps protect?
The nuclear DNA in basal cells
What represents an autoimmune disease with loss of melanocytes
Vitiligo
What happens in Albinism
A genetic partial loss of pigment production
What happens in Nelson’s syndrome
Melanin stimulating hormone is produced in excess by the pituitary
What is the function of Langerhans cells
Involved in the skin immune system
What is the appearance of Birbeck granules
Racket organelles
Where are Merkel cells found
Between keratinocytes and nerve fibres
What do Merkel cells act as
Mechanoreceptors
Describe Merkel cell cancer
Rare
Caused by viral infection
High mortality
What is there always next to a hair follicle
Adjacent sebaceous gland
What are the 3 phases of hair follicle growth
Anagen (growing)
Catagen (involuting)
Telogen (resting)
Describe Alopecia areata
Autoimmune hair loss
What 3 sections make up the nail plate
Ventral
Intermediate
Dorsal
What is the Dermo-epidermal Junction
The interface between epidermis and dermis
What does the dermo-epidermal junction play a key role in
Epithelial mesenchymal interactions
Support, anchorage, adhesion, growth and differentiation of epidermal cells
Semi-permeable membrane acting as barrier and filter
What are present in the dermo-epidermal junction
Lots of proteins, fibrils and keratins