Lecture: Anatomy 4: The integumentary system Flashcards
What is the epidermis?
Superficial layer of keratinocytes.
What is the dermis?
Deeper layer of connective tissue and skin appendages.
Where does the epidermis originate from?
The ectoderm
Where does the dermis originate from?
The mesoderm
What are keratinocytes?
Keratinized squamous cells
What are melanocytes?
Melanin producing cell; delivers melanin to keratinocytes via dendrites, and lie near the BM. Melanin protects against UV radiation.
Where do melanocytes originate from?
Originate from the neural crest cells
How many melanocytes for each keratinocyte?
1 melanocyte to roughly 36 keratinocytes.
What are Langerhans cells?
Cells that house antigen presenting cells (APCs) and immune sentinels which survey the microbiome of the skin
Where do Langerhans cells originate from?
Originate from the bone marrow
What are Merkel cells?
Cells that mediate tactile sensation to light and touch
Where do Merkel cells originate from?
Originate from neural crest cells
What are the functions of the skin?
- Mechanical barrier
- Waterproofing
- Protection from injury
- Protection from infection
- Cushioning and insulation
- UV protection
- Thermoregulation
Describe the composition of the epidermis
Composed of stratified squamous epithelium with keratinocytes undergoing terminal differentiation. Has a basement membrane (collagen layer) at the junction with the dermis.
What are the 4 layers of the epidermis?
- Horn cell layer (stratum corneum)
- Granular cell layer (stratum granulosum)
- Prickle cell layer (stratum spinosum)
- Basal cell layer (stratum basale)
Describe the composition of the basement membrane
Layer below epidermis that is resistant to shearing forces and composed of collage type IV.
What is the purpose of the basement layer?
Protect against shearing forces and control mesenchymal/stromal interactions (e.g. invasion) of epithelium.
What are the consequence of damage to the basement membrane?
Damage to basement membrane can mean that cancerous cells in the epithelium have the potential to migrate and metastasize.
Describe the composition of the dermis
Dense connective tissue containing supportive structures
What are the 4 layers of the dermis?
- Collagen, elastin, and extracellular matrix
- Nerves, blood vessels and lymphatics
- Mechanoreceptors, etc.
- Subcutaneous fat
What is the purpose of the reticular dermis?
Makes the skin sensitive to touch and pressure
What is the purpose of the papillary dermis?
Forms fingerprints
What are basal cell carcinomas?
Tumours that originate in the hair follicle and are caused by exposure to UV. Invasive and locally destructive but very unlikely to metastasize.
