Integumentary System: Embryology, Histology & Hair Flashcards
Where does the epidermis originate from?
Ectoderm
What does the dermis originate from?
Mesoderm
Where do sweat glands, sebaceous glands and hair follicles originate from?
Mesenchyme (which itself originates from mesoderm)
What does ‘thickness of skin’ depend on?
Thickness of epidermis
What are the 5 layers of the epidermis? (CLGSB)
Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale
What does the stratum corneum consist of?
Dead epithelial cells that are constantly sloughed off
What does the stratum lucidum consist of?
Dead, keratinised epithelial cells with no nucleus
What do stratum granulosum epithelial cells consist of?
Multiple layers of keratinised cells and keratohyaline granules
What does the stratum spinosum consist of?
Keratinocytes bound by desmosomes
Cytoplasm containing tonofilament
What does the stratum basale layer consist of?
Single layer of cuboidal cells
Stem cells which divide to become keratinocytes
What cells are found in the epidermis?
Merkel cells - free nerve endings. In basal layer
Keratinocytes - main type of cell
Melanocytes - between basal cites
Langerhans cells - for immunisation
What processes take place in the epidermis?
Squamous cells in stratum corneum sloughed off
Migration, differentiation and keratinisation of keratinocytes
Proliferation of keratinocytes on basal layer
What is the dermis composed of?
Loose, irregular connective tissue
Vessels and nerves
Hair follicles
What are the two layers of the dermis and how do they differ?
Reticulum layer - loose connective tissue
Papillary layer - dense connective tissue, contains glands & hair follicles
How is blood supplied to the dermis?
Vessels
Arteriovenous anastomoses
How is blood supplied to the epidermis?
Diffusion from blood vessels in dermis
What are the functions of hairs?
Mechanical protection
Sensory perception
Thermoregulation
What are the 3 main parts of a hair?
Shaft - 3 parts
Root - Similar structure to shaft
Bulb - mass at base of root
What are the 3 parts of the shaft of a hair? What makes up these layers?
Outer cuticle - single layer of keratinised cells
Cortex - compact dead layer
Medulla - cuboidal cells
What epithelium covers the bulb of a hair root?
Stratified squamous epithelium
What is the indent found in the bulb of a hair called?
Papilla
What is the life cycle of a hair?
Anagen (growth)
Cartagen (regressive, atrophy)
Telegenic (rest)
Repeats
What is secreted directly into the hair follicle to protect the hair?
Sebum
What are the 3 types of hair follicle?
Tactile - for tactile sense, innervated e.g. whiskers
Single follicles - group together in clusters of 2-4 (pigs)
Compound follicles - multiple hairs coming out of each follicle e.g. cat/dog
What is hyperkeratosis?
The thickening of the stratum cornea
Due to excessive keratin levels
On footpads/nose
What structures are composed of cornified epidermis?
Hooves, claws, beaks, shells, scales
What is the difference between 1st, 2nd and 3rd degree burns?
1st - damage just to epidermis
2nd - damage to epidermis and dermis
3rd degree - damage to epidermis, dermis and subcutaneous layer/hyperdermis
