Week 1 Flashcards
The layers of skin
Epidermis
Glands / hairs/ nails
Dermis
Sub cutis
What is the layer between epidermis and dermis called
Dermo-epidermal junction
Function of dermo-epidermal junction
Semi permeable membrane filtering substances that crosses
Anchors the epidermis to the dermis
The dermis is mainly
Connective tissue
The Sub cutis layer is mainly
Fat
The layers of epidermis (from top to low)
Keratin layer
Granular layer
Prickle cell layer
Basal layer
What are basal stem cells
Cells that can differentiate into a specific type of cell of the epidermis and migrate through it to replace it
Where are basal stem cells located at
Basal layer of epidermis
What cells are in the epidermis
Keratinocytes
Melanocytes
Langerhans cells
Merkel cells
Basal cells
Which type of cells make up the most of epidermis
Keratinocytes
Function of langerhans cells
Dendritic cells involved in immunological functions of the skin
Function of Merkel cells
Mechanoreceptor cells
Function of melanocytes
Pigment producing dendritic cells protecting against sun damage
Where are langerhan cells located at
Prickle cell layer of epidermis
Where are Merkel cells located at
Basal layer of epidermis
Where are melanocytes located at
Basal layer of epidermis
Basal cells at the basal layer are which type of cells
Cuboidal cells
Features of structure of prickle cell layer
Large polyhedral cells
with a lot of desmosomes in between the cells acting as connections
Features of granular layer
2-3 layers of flatter cells
Cells do not have nuclei
Lamellar bodies
Features of keratin layer
Mostly corneocytes (dead keratinocytes)
Lamellar granules
Waterproof barrier
Function of keratin layer
Prevents entry of unwanted substaces
Prevents excessive loss of water
The cells at the outermost layer of epidermis are
Dead cells (corneocytes) which are continually shed and replaced from below
What makes the keratin layer waterproof
Cells are close to each other
Lamellar granules release lipids which is hydrophobic
How do melanocytes protect us against sun damage
- Melanocytes produce melanin
- Melanin absorb light and are contained in melanosomes
- Melanosomes are then transported to adjacent keratinocytes by dendrites of the melanocytes
- This induces pigmentation and protect the basal cells against UV radiation by absorbing the UV light (because it is black)
What causes different skin colours
- Due to different activity level of melanocytes.
- e.g. melanocytes in black skin has higher activity level = produce more melanin = more pigmentation - Ratio between eumelanin and phenomelanin
What is vitiligo and what causes it
Vitiligo = patches of skin losing colour
Due to autoimmune destruction attacking melanocytes
What causes albinism
Genetic disorder reducing melanin production
What causes skin hyperpigmentation in Addison’s disease
High ACTH stimulating melanocytes to produce more melanin
Structure of hair follicles
Specialized keratins
Hair papilla is in the dermis layer and it extends into the epidermal layer and out of the skin
Sebaceous gland next to it
Arrector pili muscle attached to the hair follicles
Function of arrestor pili muscle
It contracts to erect the hair when you’re cold to provide thermal insulation
= causes goosebumps
What condition affects the arrestor pili muscle
Leprosy
What causes hair to be pigmented
Melanocytes in epidermis
What are the phases of growth of hair
Anagen
Catagen
Telogen
What is anagen
Growth of new hair
What is catagen
end of active hair growth and cuts individual hairs off from the blood supply and from the cells that produce new hair (forms club hair)
What is telogen
resting period when strands remain in their follicles till they shed
Most hair at any time are in which phase
Anagen
Why can animals’ fur shed at the same time whereas human hair does not
Because animals have synchronous telogen phase whereas in humans the telogen phase of each hair is different
List the outer structures of the nail
Nail plate
Nail folds
Eponychium
What are the nail folds
The skin around the nail that protects the margin of the nails
What is the eponychium
keratin layer of the skin that extends over the proximal nail plate
What are the structures underneath the nail plate
Nail bed
Germinal matrix
Hyponychium
What is the nail bed
Directly underneath the nail plate providing a smooth surface for the nail plate to glide over during growth
How do nail plates grow
Cells in germinal matrix divide and become keratinised. The continuous cell division pushes the nail plate, letting it glide over the nail bed = nail becomes longer
What is the hyponychium
The area underneath the free edge of nail plate
What are the 2 layers of dermis
Papillary dermis
Reticular dermis
Describe the papillary dermis and reticular dermis layers
Papillary dermis is thinner and it is just below the epidermis
Reticular dermis layer is thicker and contains several structures
What structures are in reticular dermis layer
Blood vessels
Pilosebaceous units (sebaceous gland + hair follicle)
Lymphatics
Nerves
Structures in dermis
Blood vessels
Lymphatics
Nerves
Collagen and elastin fibres
Hair follicles
Glands
Cells
What cells are present in dermis
Macrophage
Mast cells
Langerhans cells
Fibroblasts
What are the 2 types of aging
Intrinsic and extrinsic
What is intrinsic aging
Inevitable physiological process that causes skin to look more saggy and less firm, hollowed cheeks as you age
What is extrinsic aging
Skin aging due to external factors such as UV light, smoke particles, pollutants on top of intrinsic aging
If an area of skin aging is mostly due to extrinsic aging, what would the features be
Coarse wrinkles (deep wrinkles)
Loss of elasticity
Rough texture appearance
Hypertrophic photoaging
If an area of skin aging is mostly due to intrinsic aging, what would the features be
Fine wrinkles
Dry skin
Thin skin
Telangiectasia
Atrophic photoaging
Atrophic photoaging increases the risk of
Non melanoma skin cancer
What type of plexus do vessels in dermis form
horizontal plexuses
Dilation of lymphatic vessels in the dermis can cause
Chronic lymphoedema
Dilation of blood vessels in the dermis can cause
Angioma
What structures are responsible for the innervation of the skin
Free sensory nerve endings
Special receptors
Motor nerve fibre
What are the special receptors for sensory innervation of the skin
Pacinian corpuscle
Meissners corpuscle
Pacinian corpuscle is for what type of sensory
Pressure
Meissner corpuscle is for what type of sensory
Vibration
Where is Meissener’s corpuscle located at
Papillary layer of the dermis
Where is Pacinian corpuscle located at
Reticular layer of dermis
What is alopecia areata and what causes it
Patchy hair loss
Due to autoimmune destruction of hair papilla causing hair to fall out
Does hair grow back in affected areas in alopecia
Yes, because the stem cells are not attacked
What are the 3 types of glands present in skin
Apocrine
Eccrine
Sebaceous
What is eccrine gland
Sweat glands that open directly onto the skin surface
What is apocrine gland
glands that drain into hair follicles
What are sebaceous glands
Glands in hair follicles that secrete sebum
When do sebaceous glands become active and start producing sebum
During puberty