TOB Session 6 Flashcards
Skin
What variations can you have in the macroscopic structure of the skin?
Colour (e.g. Ethnicity, Site, UV exposure)
Hair (e.g. Site, Sex, Age, Ethinicity)
Thickness (e.g. Site)
Laxity/Wrinkling (e.g. Site, Age, UV Exposure)
Oiliness (e.g. Puberty, Site)
Name three skin diseases that can be influenced by some of these macroscopic variations
Vitiligo
Alopecia Areata
Melanoma (Skin Cancer)
What is Vitiligo?
Depigmentation of Skin, less of a problem in fair skinned people. It is an autoimmune disorder where the melanocytes are attacked. There are no effective treatments.
What is Alopecia Areata?
An autoimmune response leading to hairloss. There are no effective treatments..
What is a malignant melanoma?
An invasive tumour of melanocytes. The cells divide rapidly, penetrating the basal lamina and eventually invading the blood and lymphatic vessels to distribute throughout the body.
What are the four layers of the epidermis?
Horny Layer (Stratum Corneum) Granular Layer (Stratum Granulosum) Prickle Cell Layer (Stratum Spinosum) Basal Layer (Stratum Basale)
Describe the process of kerantinocyte differentiation.
Keratinocyte mitosis begins in the basal layer. Daughter keratinocytes move up into the prickle cell layer where they lose their ability to divide and terminal differentiation begins. They lose their plasma membrane in the granular layer and differentiate into corneocytes which make up the stratum corneum.
What do keratinocytes synthesise?
They synthesise keratins (heterodimeric fibrous proteins) which contribute to the strength of the epidermis and are the main constituent of hair and nails.
What are keratohyalin granules and where would you find them?
They are aggregations of keratins, other fibrous proteins and enzymes and are found in the granular layer.
How long does it take for a keratinocyte to move from the basal layer to the stratum corneum?
Approximately 30-40 days
What are melanocytes?
Melanocytes are dendritic cells of neural crest origin that occur at intervals along the basal layer of the epidermis. Melanocytes produce melanin (the skin pigment).
What are langerhans cells?
Dendritic cells of bone marrow origin. They present antigens to T lymphocytes and mediate immune reactions.
Where would you find Langerhans cells?
Spaced through the prickle cell layer.
What is the dermo-epidermal junction?
The epidermal basement membrane just below the basal layer of the epidermis. It is visible clearly with a PAS stain.
What are the properties of the dermis?
It is tough, fibrous and vascular.
The extracellular matrix makes up the main part of the dermis. What is this synthesised by?
Fibroblasts.
What is a fibroblast?
A spindle shaped cell scattered through the dermis that synthesises the extracellular matrix.
Name 4 other components of the dermis.
Blood Vessels
Nerves
Mast Cells
Lymphatic Vessels
What is the extracellular matrix made up of?
Collagen, Elastin and Ground Substance
What is the main function of the dermis?
To bind the epidermis to the subtending connective tissue.
Where do we find small and large blood vessels in the dermis?
Small blood vessels are found in the superficial dermis, large blood vessels are found deeper in the dermis.
What is a birthmark?
A malformation of blood vessels.
Where are mast cells found?
They are distributed around dermal blood vessels in the skin.
What do mast cells do?
When activated (during type I immediate hypersensitivity reactions) they release histamine, causing increased vascular permeability and leakage of plasma into extravascular sites.
