Structure & Function of Skin Flashcards by Hannah Mathias

Function of Epithelial tissue

Cover surfaces with sheets cells.
Have function in secretion, barrier & protection,
strength & support

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What is the epidermis ?

The most superficial layer of the skin. Avascular.

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What are the layers of the epidermis ?

The epidermis comprised of several layers (bottom to top)

stratum basale
stratum spinosum
stratum granulosum
stratum lucidum
stratum corneum

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What does the number of layers and thickness of the epidermis depend on ?

Location in the body

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What are the main cells of the epidermis ?

Keratinocytes

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Where do keratinocytes originate ?

In the basal layer and produce the main protein of the epidermis called keratin.

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What other cells are found in the epidermis ?

Melanocytes
Langerhan’s cells
Merkel’s cells

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What is the function of melanocytes ?

Produce skin pigment

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What is the function of Langerhan’s cells ?

Immune, antigen- presenting cells

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What is the function of Merkel’s cells ?

Mechanoreceptors for light-touch

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Function of the epidermis

Protection, skin regeneration, skin colour

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Stratum corneum

Outermost layer
Made up of mature keratinocytes.
Keratinised squamous epithelium.

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Stratum Lucidum

Only found in areas of thicker skin.

Clear on histological slides.

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Stratum granulosum

Mature keratinocytes, contains granules in the cytoplasm.
No nuclei

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Stratum spinosum

Connect by desmosomes
Langerhan’s cells are most abundant here.

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Stratum basale

Cells are attached to the basement membrane, hemidesmosomes.

Cell division and grow (mitosis)

Contains melanocytes.

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How is the dermis anchored to the basal lamina ?

By Collagen 7

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Where is the dermis located ?

Deep the the epidermis.
VASCULAR.

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Function of the dermis

To sustain and support the epidermis, as it has blood vessels to supply nutrients and oxygen.

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What does the dermis contain ?

Fibroblasts
Collagen

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What are the 2 layers of the dermis ?

Papillary dermis
Reticular dermis

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What is the papillary dermis ?

The most superficial layer of the dermis.

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Function of the papillary dermis

Increases the surface area for the transfer of oxygen and nutrients between the dermis and epidermis.

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What is the papillary dermis made up of ?

Fine collagen and elastin fibres.

Small blood vessels and nerves.

i.e. Loose connective tissue

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What is the reticular dermis ?

The deep layer of the dermis.

What is the reticular dermis made up of ?

Courses collagen & elastin fibres Large blood vessels and nerves i.e. thicker connective tissue

What does the reticular dermis surround ?

Hair follicles Sweat glands Sebaceous glands Nerves Plexus of blood vessels

Other structures in the dermis

Appendages

Name some appendages

Hair follicles Glands Arrector pili muscle Tactile corpuscles

What is a hair follicle ?

A sac-like down growth of the dermis and epidermis out of which hair grows.

Hair follicle structure

Hair follicles are anchored in the hypodermis. Hair shaft grows form the bulb and is made of keratin.

What other 2 structures are associated with the hair follicle ?

Sebaceous glands Arrector pili

What are the components of a Pilo-sebaceous unit ?

Hair follicle Sebaceous gland Arrector pili

What is the function of sebaceous glands ?

Exocrine glands that secrete sebum to lubricate hair and adjacent skin.

What is the function of the arrector pili ?

Contraction of smooth muscle attached to the papillary dermis and pulls the hair upright (goosebumps) controlled by the SNS.

What so the sebaceous glands look like ?

Raspberry shaped.

What are exocrine glands ?

Glands which have ducts that open to the outside of the body or to a cavity inside the body.

Sweat gland location

In the dermis and hypodermis. (ALL over the body)

Function of the sweat glands

Thermoregulation Also a response to 'Fight or Flight' - controlled by the SNS

Tactile corpuscle function (Meissner's corpuslce)

Facilitate the sensorial capabilities of the skin. e.g. Light touch Vibration Other sensations

Hypodermis location

Deep to the dermis

Hypodermis composition

Loose connective tissue Adipose tissue Blood vessels Nerve tissue etc.

Function of adipose tissue

Energy storage Shock absorption Helps keep in heat

What structures are found in the hypodermis ?

Deepest part of hair follicles Eccrine and apocrine glands

Subcutaneous vascular plexus function

Series of blood vessels that supply and drain the subcutis.

Subdermal vessel plexus location

Network of blood vessels found at the level of the dermis.

Vascular plexus function

Plays an important role in thermal regulation. These vessels are superficial to the layer of fat in the subcutis.

Why are the vascular plexus vessels superficial to the layer of fat in the subcutis ?

Otherwise the fat which is essential is insulation would prevent those blood vessels from releasing heat.

Cutaneous nerve function

Provide sensory innervation to the skin and have a number of sensory receptors.

What is underneath the hypodermis ?

A layer of fascia which separates the hypodermis from the underlying muscle.

Fascia meaning

Thin layer of fibrous connective tissue.

Function of melanocytes

Synthesise and release brown pigment melanin. Absorbs UV-B and prevents DNA damage to underlying cells of the hypodermis.

What is melanoma ?

Tumour of melanocytes and is caused by exposure to UV radiation. - lower incidence in those who have more melanin.

Function of Langerhan's cells

Express Langerin which helps bind and degrade viruses such as HIV in specialised endosomes called Birbeck granules.

Which intermediate filaments are expressed in the stratum spinosum ?

K1 and K10

What is the function of filaggrin ?

Maintains the optimal skin barrier Aids keratin filament aggregaation Inhibits water loss.

What is the precursor of filaggrin ?

Pro-filaggrin

How does filaggrin inhibit water loss ?

Filaggrin cleaved into amino acids which aid in maintaining moisture.

Key functions of the skin

Protection Sensation Homeostasis

Lamina densa

Type 4 collagen

Lamina reticulates

Type 7 collagen

Mutation in collagen 7

Dystrophic epidermolysis bullosa = blistering

Tyrosinase

Produced from RER and is responsible for synthesis of melanin Converts melanocyte into melanin

What is periodontal membrane ?

Periodontal membrane is a fibrous joint between the teeth and the skull.

What is meant by cornification ?

Epidermal keratinocytes undergo a unique form of terminal differentiation and programmed cell death known as cornification.

What happens in cornification ?

Cornification leads to the formation of the outermost skin barrier, i.e. the cornified layer, as well as to the formation of hair and nails

Functions of the cornfied layer of skin

It prevents the penetration of allergens, pathogens (viruses and bacteria), chemical irritants and UV radiation, and the loss of body fluids.

Results of filaggrin mutation

Mutations in the Filaggrin gene can cause absent or reduced filaggrin protein, leading to impaired keratinization and skin barrier defect.