Integumentum Flashcards
What constitutes to the integumentary system?
the skin (cutis) and its derivatives
How many layers does the skin consist of?
2 layers
What are the two main layers of the skin?
1) the epidermis
- keratinized stratified squamous epithelium
- grows continuously
- maintains normal thickness by desquamation
2) the dermis
- dense connective tissue
- imparts mechanical support, strength and thickness
- derived from the mesoderm
What is the dermis also called?
true skin
What is the epidermis composed of?
keratenized stratified squamous epithelium
What is the dermis composed of?
dense connective tissue
How does the epidermis maintain its thickness?
- grows continuously
- process: desquamation
What is the dermis derived from?
the mesoderm
What does the dermis contain?
- hair follicles
- glands
- sweat glands
- etc.
What lies below the dermis?
the hypodermis
What are the different epidermal derivatives of the skin?
- hair follicles
- hair
- sweat (sudoriferous) glands
- sebaceous glands
- mammary glands
What is the epidermis composed of? What are the distinct layers?
composed of: keratinized stratified squamous epithelium
4 distinct layers:
thick skin= 5 distinct layers (outside to inside):
- stratum corneum (keritinized cells)
- stratum lucidum (limited to thick skin!) (subdivision of stratum corneum)
- stratum granulosum (numeous intensely staining granules)
- stratum spinosum (light microscopic appearance of short process extending from cell to cell)
- stratum basale/stratum germinativum (mitotically active cells= stem cells))
What is the easiest way to indentify the different layers of the epidermis?
Look for stratum granulosum: darkest, deepest colour.
What epidermis layer is distinct to thick skin only?
stratum lucidum (part of stratum corneum)
State the 4 skin layers from the outside to the inside.
stratum corneum
stratum granulosum
stratum spinosum
stratum basale
What is the stratum basale? What is represented by? What does it contain?
stratum basale: most deepest layer of the dermis
represented by a single layer of cells laying on the basal lamina
contains:
- stem cells from which new cells (keratinocytes) arise by mitotic division.
- melanocytes in cytoplasm (produce melanin) (5% of cells in spidermis)
Where do all the epidermis layers come from?
Stratum basale stem cells divide mitotically generating new cells.
What cells arise from the stratum basale stem cells? how?
kerinocytes
by mitotic division
What else, except of stem cells, is present in the stratum basale?
melanin:
- transferred from neighbouring melanocytes
- intersperced in statum basale
Where are melanocytes located? What is their structure? What percentage do they make up of the epidermis?
location: stratum basale; stratum spinosum (processes)
structure: long processes that extend between keratinocytes into the stratum spinosum
5% of cells in the epidermis
What cells reside in the stratum basale?
melanocytes
What is the connection of skin colour to melanin?
The greater the melanin number the darker the skin colour.
What does melanin do?
Keeps all dividing cells protected (shields their nucleus= shielfing their genetic material).
What do the long processes of melanocytes extend into?
into stratum spinosum through the keratinocytes