What are sebaceous glands?
Secrete sebum onto hair through holocrine secretion.
What is the eponychium?
The thickened layer of skin/fold surrounding the base of the nails.
Where are the papillae found?
On the tongue. Projections of the dermis.
What are the 3 main layers of the skin?
- Epidermis: The outermost layer of the skin, providing a waterproof barrier.
- Dermis: Tough connective tissue, hair follicles and sweat glands.
- Hypodermis/subcutaneous tissue: The deeper tissue made of fat and connective tissue.
What is the epidermis composed of and what cells are present?
- Keratinised stratified squamous cells make up the epithelium
The cells present are mainly keratinocytes but there are also melanocytes in smaller amounts.
What is the order of the sub-layers in the epidermis?
- Stratum Corneum
- Stratum Lucidum
- Stratum Granulosum
- Stratum Spinosum
- Stratum Basale
Remember: Chicken or Lamb with Ground Spice is Brilliant
What is the role of melanocytes?
To produce melanin which provides protection against UV.
What is the role of keratinocytes?
Produce keratin to prevent water loss through the secretion of lipids.
What are the features of the stratum corneum (the first layer of the epidermis)?
- Dead keratinocytes here
- No nucleus/ cell organelles
- Desquamation (cell shredding) occurs here
Describe Stratum lucidum
- This extra layer allows the skin to turn from thin to thick which is found on the palms and soles.
- Contains eleidin (type of keratin)
- Anucleate cells
What is the reason for the darker colour in the Stratum Granulosum?
A protein called keratohyalin
The Stratum Spinosum has 8/10 layers of __1__ attached by desmosomes and cadherin proteins. It provides __2__ and strength to the skin. The cells present here are melanocytes and __3__ but the most abundant being __4__.
- Keratinocytes
- Flexibility
- Intraepidermal
- macrophages/Langerhans (dendritic)
What type of cells is present in the stratum basale? What is the other name for this layer?
- Single-layer of cuboidal/columnar cells
- Stem cells that produce keratinocytes
- Melanocytes (to produce pigment melanin)
- Merkel/tactile cells
The other name is germinativum
Remember the base forms the SSteMM
What are Merkel/tactile cells?
Touch receptive (like tactile TOUCH).
Where does keratinisation begin?
Stratum Granulosum
What are the 2 sub-layers for the dermis?
- Papillary
- Reticular
The superficial part of the dermis is called the __1__ and consists of __2__ connective tissue. Mostly consists of __3__ cells. Contains __4__ corpuscles which are a mechanoreceptor for detecting __5__. They are rapidly adapting which for e.g allows clothes to become unfelt. The finger-like projections of the __6__ extend through the epidermis which strengthens the connection between the two layers. This layer is thinner compared to the deeper reticular layer.
- Papillary layer
- Loose areolar
- Fibroblasts
- Meissner’s
- Light touch
- Papillae
The reticular layer of the dermis consists of __1__ connective tissue. Ducts of __2__ sebaceous glands are here as well as merocrine __3__ (sweat) glands. Hair follicles are also present. There are 2 mechanoreceptors __4__ and __5__ which allow for deep touch (rapidly adapting) and stretch (slowly adapting) respectively. The reticular layer is much thicker than the papillary. There are also blood vessels here.
- Dense irregular
- Holocrine
- sudoriferous
- Pacinian
- Ruffini
What are sebaceous glands connected to?
Hair follicles
What is the role of keratin?
To produce the extracellular matrix, provide overall strength to the skin and to provide waterproofing to the skin (this prevents dehydration so water is not lost).
How is the epidermis nourished without blood vessels?
Diffusion from blood capillaries at the deeper levels.
How is the dermis connected to the epidermis?
Through the basement membrane.
Is the hypodermis/subcutaneous tissue a part of the skin?
No, it lies just under the dermis. It attaches the skin to underlying bone and muscle. It is made of loose connective tissue.
What is the difference between thick and thin skin?
- Thick skin = No hair, therefore no sebaceous glands or arrector pili muscles. It thus has a thinner dermis than thin skin. Found in areas prone to abrasion, that’s why our palms have no hair. 5 Epidermis layers. Fewer eccrine sweat glands.
- Thin skin = Hairy has all of the above. 4 Epidermis layers as stratum lucidum is missing.
