Structure And Function Of Skin Flashcards
What is integument?
Skin, hair and nails collectively
What are the functions of the skin?
Protection, thermoregulation, sensation, repair and vitamin D production
What are the 3 names of the layers of skin?
Epidermis, dermis and hypodermis
What are the functions of the epidermis?
Gives skin its colour, protects the body from pathogens and the environment and vitamin D production
What are the functions of the dermis?
Tensile strength and elasticity - also contains blood vessels, skin glands and sensory receptors
What are the functions of the hypodermis?
Insulate deeper tissue and anchors skin to the muscle
What is the epidermis made up of?
Multiple layers of different keratinocytes
What are the layers of the epidermis?
Basal layer, spiny layer, granular layer, cornified layer and stratum lucidum
What is the basal layer of the epidermis made up of?
Stem cells
What happens in the basal layer of the epidermis?
Daughter cells move up, differentiating as they go until they are shed from the outer surface
What happens in the spiny layer of the epidermis?
Desmosomes between keratinocytes
What does the granular layer of the epidermis contain?
Keratohyaline granules and lamellar bodies containing lipids
What is the function of the cornified layer of the epidermis?
Outer protective layer
What is special about the cornified layer of the epidermis?
Cells are keratinised, flattened, have lost the nucleus and non-polar lipids are between the cells
What do melanocytes look like?
Neurons (ish)
What is the function of melanocytes?
Synthesise melanosomes and transfers them to basal keratinocytes
What is the function of langerhans cells?
Antigen presenting cell - seeks and deals with invading microbes
What do langerhans cells look like?
Pale cells in non-basal epidermal layers
What is the function of merkel cells?
Sensation
How is melanin arranged in keratinocytes?
A cap distal to the nucleus
What is the dermis made up of?
Layers of connective tissue characterised by interconnected mesh of elastin and collagen fibres, produced by dermal fibroblasts
What are the principal cells of the dermis?
Fibroblasts
What are the two layers of the dermis?
Thin papillary layer and deeper reticular layer
What makes up the thin papillary layer of the dermis?
Finger-like protrusions into the epidermal layer
What makes up the dermis?
Dense, irregular connective tissue
What does collagen provide in the dermis?
Tensile strength - protection against abrasion and impact
What is collagen made by?
Fibroblasts
Why is the dermal-epidermal border often wavy?
To resist shear forces
What are dermal papillae?
Finger-like protrusions of the dermal connective tissue into the epidermal layer
What are rete ridges?
Extensions of the epidermis into the dermal layer
What does the verhoeff- van gieson stain show?
Collagen fibres in red and elastin fibres in black
What are some other names for the hypodermis?
Fascia or subcutis
What is the hypodermis made up of?
Well vascularised loose areolar connective and adipose tissue
What is the function of the hypodermis?
Fat storage, insulation and cushioning for the integument
What parts of skin do not have hair?
Palms, soles of feet and lips
What parts is a strand of hair made up of?
Shaft, root and bulb in a hair follicle
What is a hair follicle?
Epidermal tissue that dips down into the dermis and interacts with other structures
What other structures does the hair follicle interact with?
Apocrine glands, sebaceous glands, arrector pili muscle and nerve receptors
What does the hair follicle contain?
The hair matrix active site of hair growth and pigmentation
What are the two different cell types in a hair bulb?
Follicular keratinocytes and melanocytes
What do follicular keratinocytes do?
Produce hard keratin (= hair)
What causes baldness?
Follicular keratinocytes at the bulb replicate only a set number of times
Why does hair turn white?
Over time, melanocytes stop producing melanin
What are eccrine sweat glands?
Normal sweat glands
What do eccrine sweat glands secrete?
Watery secretion onto skin surface, cools body by evaporation
What are apocrine sweat glands and where are they found?
Secretes into hair follicles and found in the armpits and anogential region
What do sebaceous glands secrete?
Oily sebum into the hair follicle
What is the nail fold?
Where the skin seals the edge of the nail
What is the eponychium?
Proximal skin fold that gives rise to the cuticle
What is the cuticle?
Semi-circular layer of dead skin keratinocytes that covers the junctions where the nail enters the skin
What is the function of the cuticle?
Preventing the entry of pathogens
What is the nail matrix?
Creates the nail plate and contains special epidermal tissue and modified keratinocytes
What do free nerve endings sense?
Nociception, thermal sensation and light touch
What are examples of sensory receptors with encapsulated endings?
Pacinian corpuscles, merkels discs, meissner corpuscles, Ruffini endings, root hair plexuses and Krause end bulbs
What do pacinian corpuscles sense?
Vibration or brief touch
What do merkels discs sense?
Sustained touch/pressure
What do meissner corpuscules sense?
Moving touch or vibration
What do ruffini endings sense?
Steady pressure
What do root hair plexus’ detect?
Hair displacement
What do Krause end bulbs sense?
Touch/pressure
