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Skin

Layers, cells

QuestionAnswer
What are 2 main components of the integumentary system? Cutaneous membrane (skin) and the accessory structures (hair, nails, and multicellular exocrine glands)
What are the functions of the skin and hypodermis? Protection, excretion (of salts, water and organic wastes), maintenance of body temperature, production of melanin, production of keratin, synthesis of vitamin D3, storage of lipids in adipocytes, detection
What cells does the epidermis consist of? Stratified squamous epithelium
Why does the epidermis rely on the diffusion of nutrients and oxygen within the dermis? Epidermis is avascular
Which type of cell dominates the epidermis? Keratinocytes
How many layers of keratinocytes make up the thin skin? 4 (0.08mm thick)
Which extra layer does the thick skin have? Stratum lucidum
Where can thick akin be found? Palms of hands and soles of the feeet
How many layers of keratinocytes make up the thick skin? 5
What are the five layers of the epidermis? Stratum basale, stratum spinosum, stratum granulosum, statum lucidum, stratum corneum
Which layer lies closest to the dermis? Stratum basale
Which layer is much thicker in thick skin? Stratum corneum
What does the stratum basale form that extend into the dermis? Epidermal ridges
What projects from the dermis adjacent to these? Dermal papillae
Why are the ridges and papillae important? (Connecting stratum basale to dermis) Strength of the attachment is proportional to the surface area of the basement membrane
What type of cells make up the statum basale? Basal cells (germinative)
What are basal cells? Stem cells whose division replaces the more superficial keratinocytes
What type of cells do skin surfaces that lack hair contain? Tactile cells (Merkel cells)
Why are these cells important? Tactile cells are sensitive to touch, they release chemicals that stimulate nerve endings
How are layers of keratinocytes bound together in the stratum spinosum? Desmosomes
What cells are contained within the stratum spinosum that participate in the immune response? Dendritic (Langerhans) cells
How many layers of keratinocytes does the stratum granulosum consist of? 3-5
What have keratinocytes started doing by the time they reach the granulosum? Keratin or keratohyalin
What happens to cells as keratin develops? Cells grow thinner and flatter, their membranes thicken and become less permeable
What does keratohyalin form? Dense cytoplasmic granules that promote dehydration of the cell, as well as aggregation and cross-linking of keratin fibres
What are the cells that make up the stratum lucidum like? Flattened, densely packed, largely devoid of organelles and filled with keratin
What is keratinisation? Formation of protective superficial layers of cells filled with keratin
Where doesn't keratinisation occur? Anterior surface of the eyes
How many days does it take for a cell to move from the stratum basale to the stratum corneum? 7-10 days
What is insensible perspiration? When water from the intestinal fluids slowly penetrates to the surface to be evaporated into the surrounding air. (Unable to see or feel the water loss)
What is sensible perspiration? Water loss from active sweat glands, which people are usually aware of
What are the layers of the dermis? Papillary layer and reticular layer
Which layer has dermal papillae? Papillary layer
What does the papillary layer of skin consist of? Areolar tissue
What does the reticular layer of skin consist of? Collagen and elastic fibres
What tissues does the hypodermis consist of? Areolar and adipose tissues
What is a subcutaneous injection? Injection by means a hypodermic needle
What happens to the distribution of subcutaneous fat? At puberty its distribution changes; Men: Neck, arms, lower breath, buttocks Women: breasts, buttocks, hips, thighs
How do the skin secretions protect us from infection? Sebum and sweat are mostly acidic (pH 4-4.5). Sweat from apocrine glands and drug induced sweat has been found to be slightly basic
What are Langerhans cells? Dendritic cells that contain large granules called Birbeck granules
What is xerosis? Dry skin
What are potential causes of dry skin? Thyroid disorders, weather, central heating/air con, hot baths & showers, harsh soaps, sun exposure, sun exposure, atopic dermatitis and psoriasis
What are the two types of sweat glands? Eccrine and apocrine glands
What type of glands are they? Exocrine
Where are apocrine glands stimulated? Mainly in armpits, genital area and around the nipples
What does apocrine gland sweat contain? Proteins, fats, and other substances that often result in thicker and stickier sweat. This causes sweat odour.
Which sweat glands have the larger lumen? Apocrine glands
What do eccrine gland secretions do? Help to control body temperature
Where are eccrine glands located? All over the body, and in high density in the palms, soles of the feet, and scalp areas
What are emollients? Moisturising treatments applied directly to the skin that help reduce water loss
What are different forms of emollients? Soap substitutes, bath additives, moisturising creams and ointments
What is a humectant? A humectant is a substance that binds with water molecules to increase the water content in the skin itself. It increases the surface of the skin's capacity to hold water
What is the effect of occlusion on the skin? Provides a layer of oil on the skin's surface to slow down water loss
What does a lubricant do? Reduces friction whenever anything rubs against the skin
How does oestrogen affect sebaceous glands? Reduces the size and activity
How do androgens affect sebaceous glands? Increases their size and activity
What is the pruritus? Itching
Which neurons trigger itching? Somatosensory neurons expressing the channel TRVPI
Which neurotransmitters are related to itching? Gastrin-releasing peptide (GRP) -> only found in spinal cord Natriuretic polypeptide b (Nppb) -> released by heart and some somatosensory neurons
Which neurotransmitter is more abundant? Nppb
What are the cardinal signs of inflammation? Tumour, dolor, rubour, calour, (function laesa)
What is the first stage of inflammation? Irritation
What is the discharging of pus called? Suppuration
What happens during the granulation stage? Wounds of tiny, rounded tissue are formed during healing
What are the different types of inflammation? Acute and chronic inflammation
Describe the process of acute inflammation? -Arterioles that supply the damaged area with blood dilate which results in increased blood flow -Capillaries become more permeable, so fluid can move into interstitial spaces -Neutrophils and some macrophages migrate out of the capillaries and venules
What are corticosteroids? An anti-inflammatory medicine which is structurally similar to cortisol
What are the different forms of corticosteroids? Tablets, injections, inhalers and topical steroids
What are short-term anti-inflammatory effects of corticosteroids? -Reduced inflammatory cell activation -Decreased IgE synthesis -Reduced mucosal oedema and decreased local generation of inflammatory prostaglandins and leukotrienes by inhibition of phospholipase A2 -Beta-adrenoreceptor up-regulation
What are long-term effects of corticosteroids? -Reduced T-cell cytokine production, reduced dendritic cell signalling to T-cells -Reduced eosinophil and mast cell deposition in bronchial mucosa -Reversal of excess epithelial cell shedding and goblet cell hyperplasia
What are the five main types of topical corticosteroids? Solutions, lotions, creams, ointments, gels
What are the 4 classes of potency for topical corticosteroids? Mild topical corticosteroids, moderate topical corticosteroids, potent topical corticosteroids and very potent topical corticosteroids
When would mild topical corticosteroids be used? Mild cases of inflammation such as insect bites
What potency of corticosteroid would be used for atopic eczema? Moderate topical corticosteroids
What is potency? Measurement of how powerful the effect of the medication will be
Created by: SandersE