Skin Structure and Function Flashcards by Martha Innes

What makes up the skin?

Epidermis
Dermo-epidermal junction
Dermis
Sub-cutis
Appendages

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What are examples of appendages?

Nails
Hair
Glands

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How is the epidermis formed in an embryo?

From the ectoderm
Ectoderm cells forma single layer called periderm
Gradual increase in layers of cells
Periderm cells cast off

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How is the dermis formed in an embryo?

From mesoderm below ectoderm

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How are melanocytes formed in an embryo?

From the neural crest

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What are melanocytes?

Melanin pigment producing dendritic cells

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At what stage of development is the skin at in week 4, 16 and 26 of development?

4 - Periderm above the basal layer and dermis
16 - Epidermis fully formed but without appendages
26 - skin fully formed, including appendages and melanocytes

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What are Blashco’s lines?

Lines that show the developmental growth pattern of skin

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What type of cell is the epidermis made up of?

Stratified squamous

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What are the layers of the epidermis?

Keratin layer
Granular layer
Prickle cell layer
Basal layer

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What is the keratin layer made of (and what are these cells)?

Corneocytes

Overlapping non-nucleated cell remnants

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What proteins are corneocytes mostly made up of?

Keratin and filaggrin

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How does the keratin layer form a waterproof barrier?

Contains lipids released by lamellar granules
Filaggrin fragments hold onto water, lipids repel them
Amino acids bind water on the inside

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What is the granular layer of the epidermis?

2-3 layers of flatter cells

Nuclei are lost so they are no longer proper cells

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What is the prickle cell layer?

Layer of larger polyhedral cells

Cells are migrating upwards from the basal layer to the granular layer

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Why are desmosomes present in the prickle cell layer?

Allow both adhesion (for stability) and flexibility (so cells can move upwards)

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What is the basal layer?

Usually one cell thick layer of small cuboidal cells

Highly metabolically active

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How do cells move to the surface of skin?

Basal layer contains stem cells
Daughter cells are produced, one stays in the basal layer and one moves up to prickle cell layer
From there they differentiate into the granular layer
Top layer of cells are dead - sloughed off and held together with a layer that stops water loss

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Roughly how long does it take a cell to move from the basal layer to the surface of skin?

28 days

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What factors control epidermal turnover?

Growth factors
Cell death
Hormones

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When is there loss of control of epidermal turnover?

Skin cancer

Psoriasis

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What is the difference between psoriatic skin and normal skin?

Thick keratin layer

Irregular dermo-epidermal junction

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What other cells are in the epidermis?

Melanocytes
Langerhans cells
Merkel cells

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What causes warts?

HPV infection of keratinocytes

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Where are mucosal membranes present?

Eyes, mouth, nose, genito-urinary and GI tracts | Basically anywhere that produces mucus

What is different about oral mucosa?

Masticatory mucosa is keratinised to deal with friction Lining mucosa is non-keratinised Has specialised mucosa in the tongue papillae for taste

Where are the non-keratinocyte cells located in the epidermis?

Melanocytes - basal and suprabasal Langerhans - suprabasal Merkel cells - basal

From what do melanocytes produce melanin pigment?

Tyrosine

What organelle do melanocytes contain?

Melanosomes

What is the function of melanosomes?

Melanosomes extend to the tip of the desmosome to be taken up by neighbouring melanocytes

What is the function of melanin?

Forms a thick brownish cap that doesn't let light penetrate to protect the nuclear DNA in basal cells from radiation

What conditions affect melanocytes?

Vitiligo Albanism Malignant melanoma

Where are langerhans cells formed?

Bone marrow

Where are langerhans cells found?

Prickle cell layer Dermis Lymph nodes

What is the function of langerhans cells?

Immune cells Antigen presenting Circulate to lymph nodes via lymphatics

What is the function of merkel cells?

Mechanoreceptors - detect touch and transmit a signal to the rain to perceive it

What causes merkel cell cancer?

Viral infection

What is a pilosebaceous unit?

Hair follicle plus its adjacent sebaceous glands

What do sebaceous glands produce?

Sebum

What are the phases of hair follicle growth?

Anagen - growing Catagen - involuting Telogen - resting

What are conditions affecting hair?

Virilisation (too much hair) | Alopecia areatica

What are the parts of a nail?

``` Nail matrix Lunula Nail plate Nail bed (below plate) Hyponychium ```

What is the function of the demo-epidermal junction?

Support, anchorage, adhesion and differentiation of basal cells Semi-permeable membrane acts as barrier and filter

What are conditions of the demo-epidermal junction?

Bullous pemphigoid | Epidermolysis bullosa

How is bullous pemphigoid diagnosed?

Immunofluorescence

Which layer of the skin contains connective tissue?

Dermis

What are the functions of the dermis?

Gives strength | Contains muscles, blood vessels, lymphatics and nerves

What cells make up the dermis?

``` Fibroblasts (mainly) Macrophages Mast cells Lymphocytes Langerhans cells ```

What fibres make up the dermis?

Collagen (90%) | Elastin

What are collagen and elastin made by?

Fibroblasts

What causes photoaging?

Years of UV exposure causes collagen to be lost - skin collapses Loss of elastic fibres leads to wrinkles

What is an examples of a skin condition affecting blood vessels?

Angioma

What is an examples of a skin condition affecting lymphatics?

Chronic lymphoedema

What is the function of Pacinian corpuscles?

Sense pressure

What is the function of Meissner's corpuscles?

Sense vibration

What do pacinian corpuscles look like histologically?

Onion rings

What is an example of a condition affecting nerves?

Neurofibromatosis

What are the different types of skin gland?

Sebaceous glands Apocrine glands Eccrine glands

What is the function of sebaceous glands?

Lubricate hair follicles Produce sebum Control moisture loss Protection from fungal infection

Which glands are hormone sensitive and dormant before puberty?

Sebaceous | Apocrine

What causes acne?

Sebaceous glands are too large and active, blocking follicles and causing acne

Where are sebaceous glands located?

Widely distributed, everywhere with hair | largest are in face and chest

Where are apocrine glands located?

In the axillae and perineum (underarms and groin)

Which hormone are apocrine glands dependant on?

Androgen

What is the function of apocrine glands?

Part of pilosebaceous gland, produce oily fluid which causes odour after bacterial decomposition

Where are eccrine glands located?

Whole skin surface but particularly palms, soles and axillae

What kind of stimulation activates eccrine sweat glands?

Mental, thermal and gustatory stimulation - e.g. sweaty when nervous, hot or eating spicy food

What are the functions of eccrine glands?

Ultrafiltration of fluids Cooling by evaporation Moisten palms/soles to aid grip

What is acute skin failure, and what often causes it?

Lifting up of the epidermis at the demo-epidermal junction due to toxic epidermal necrolysis Caused by medication - side effect

What are the functions of the skin?

``` Barrier Metabolism and detoxification Thermoregulation Immune defence Communication Sensory functions ```

What metabolism does the skin do?

Vitamin D metabolism | Thyroid hormone metabolism

What vascular changes happen when the skin is too hot or cold?

Too hot - vasodilation | Too cold - vasoconstriction

What happens if the skin's barrier function fails?

Fluid loss and dehydration Protein loss leading to hypoalbuminaemia Infection

What happens if the skin's thermoregulatory function fails?

Heat loss leading to hypothermia

What happens if the skin's immune defence fails?

Spread of infection

What happens if the skin's metabolic function fails?

Disordered thyroxine metabolism

What happens if the skin's communication function fails?

Inability to display healthy skin - stigma

What happens if the skin's sensory function fails?

Pain sensation

Skin Structure and Function Flashcards

(78 cards)