Skin Histology Flashcards
What are the main functions of the skin?
Protection
Sensation perception
Thermoregulation
Metabolism
What are the 3 main layers of the skin?
Epidermis
Dermis
Hypodermis/subcutaneous layer
What are the layers of the skin epidermis?
Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basalis
What is the most superficial layer of the skin epidermis?
Stratum corneum
What is the deepest layer of the skin epidermis?
Stratum basalis
What does the stratum corneum consist of?
5-50 layers of dead keratinocytes that continuously slough off and regenerate very 4-6 weeks
What does the stratum lucidum consist of?
Dead cells that do not contain any nuclei or organelle
-found on palms and soles of feet
What does the stratum granulosum consist of?
3-5 layers containing granules. These granules contain a lipid rich secretion which acts as a water sealent
What does the stratum spinulosum consist of?
Full of keratinocytes with a spiny appearence. Have lots of desmosomes which anchor the cells to one another (improves strength)
What does the stratum basalis consist of?
Mitotically active tall cuboidal stem cells
What are the different cell types in the epidermis of the skin?
Keratinocytes
Melanocytes
Langerhans cells
Merkel cells
What are melanocytes?
- located in stratum basale
- responsible for skin pigmentation
- melanosomes in the cell make melanin in the cytoplasm which is then transferred into the cytoplasm of stratum spinulosum keratinocytes
What are langerhans cells?
- present in all layers but most prominent in the stratum spinosum
- they are tissue resident dendritic cells of the skin
What are merkel cells?
- located in the stratum basale
- is a nerve cell that forms a merkel disc
- they are mechanoreceptors that perceives light touch and helps discriminate shapes and textures
What is the dermo-epidermal junction?
The junction between the epidermis and dermis
What marks the dermo-epidermal junction of the skin?
Marked by downwards folds of epidermis known as rete ridges
What are hemidesmosomes and what is their function?
Small stud like structures found in keratinocytes of the epidermis of the skin
-facilitate the stable adhesion of basal epithelial cells to the underlying basement membrane
What are rete ridges and what are their function?
They are downward folds of epidermis at the dermo-epidermal junction
-increase surface area of the junction, enhancng adhesion. Less chance the epidermis slides off
What are the 2 layers of the dermis of the skin?
Papillary layer- loose connective tissue
Reticular layer- dense irregular connective tissue
What appendages sit in the dermis of the skin?
Pilosebaceous unit
Sweat glands
What is a pilosebaceous unit?
A unit containing the hair shaft, hair follicle, sebaceous gland and the erector pilli muscle
Describe the structures in a pilosebaceous unit?
- Hair- which is a highly modified keritinised structure
- Growth occurs in the hair follicle
- Arector pilli muscles sits in papillary layer- sympathetic innervation can cause pilo-erection by cold or fear
- Each follicle has a sebaceous gland which secretes sebum that acts as waterproofing and a lubricant for the skin
What are the 2 different types of sweat glands?
Merocrine
Apocrine
What is merocrine sweat?
Main type of sweat
- a watery fluid that aids in thermoregulation
- drains directly to external environment through a pore
