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Podiatry
Epidermis podiatry
| Question | Answer |
|---|---|
| Thickness range? | 0.06mm - 0.15mm |
| Arrangement of cells? | Closely packed with little extracellular material between them, continous sheets in simple or stratified layers |
| Describe epithelial cell surfaces | Apical surface - exposed to exterior of body. Lateral surface - face adjacent cells. Basal surface - attached to basement membrane. |
| What is basement membrane? | Thin extracellular layer between epithelium and connective tissue. Consists of basal lamina and reticular lamina. Composed mainly of protein fibers. |
| Epidermis is..? | Stratified squamous epithelium |
| How long does it take for epidermis to renew? | 15-30 days |
| Does epidermis have blood supply? | No, avascular. |
| Name the two types of Epidermal cells | Kerinocytes and non-keratinocytes. |
| How much of epidermis is made from Keratinocytes? | 90% |
| What produces keratin? | Keratinocytes |
| What is keratin? | Tough, fibrous protein. |
| What does keratin do? | Protects skin and underlying tissues from abrasions, heat, microbes and chemicals. ALso helps to waterproof skin preventing water loss. |
| Main component of hair, skin and nails? | Keratin. |
| Produces lamellar granules? | Keratinocytes. |
| What do lamellar granules do? | Produce water-repellant sealant. |
| Name the 3 non-keratinocyte cells. | Melanocytes, Langerhans cells and Merkel cells. |
| Produce melanin? | Melanocytes. |
| Where are melanocytes found mainly? | Stratum Germinativum. |
| Which cells do not form desmosomes? | Melanocytes and Langerhans cells. |
| Which cells do form desmosomes? | Merkel cells and keratinocytes |
| Which cells participate in immune response? | Langerhans cells. |
| What do Merkel cells do? | Contact flattened disc of neuron called tactile (Merkel) disc. They detect touch sensations. |
| Where are Merkel cells found? | Stratum Germinativum. |
| Which cells are easily damaged by UV light? | Langerhans and melanocytes, keratinocytes are afforded some protestion by melanin granules but they do degrade melanin so it is usually absent in superficial layers of skin. |
| Name the five layers of the epidermis, superficial to deepest. | St. Corneum, St.Lucidum, St Granulosm, St Spinosum, St Germinativum. |
| How many layers of cells has each of the epidemal layers? | Corneum - 25-30, Lucidum 3-5, Granulosum - 3-5, Spinosum 8-10, Germinativum - 1 |
| -corne = ? | Horn or horny |
| lucid = ? | Clear. |
| granulos = ? | Little grains |
| spinos = ? | Thorn-like |
| germinate = ? | New life |
| % water in St Corneum? | Normally 15%, less than 10% natural functions do not work as well. |
| Which layer has a key role in preventing water loss? | St Corneum |
| Describe arrangement of cells in St Corneum | Dead flattened keratinocytes. Bricks and mortar arrangement. Intracellular spaces filled with 'cement' which holds cells together. Lipids between them help conserve moisture since water cannot pass through them easily. |
| Which layer is only found in thick skin? | St Lucidum |
| What does St Lucidum do? | Protective shield to UV light, remember that palms and soles contain few melanocytes, so prevents sunburn to these areas. |
| Contains protein eleidin? | St Lucidum. |
| Which layer does apoptosis occur? | St Granulosm. |
| What is apoptosis? | Programmed cell death. Organelles and nuclei breakdown. |
| Which layer does keratinization begin? | St Granulosm. |
| In which layer do cells become flattened and accumulate large granules of keratohyaline and lamellar granules? | St Granulosm. |
| Which layer provides strength and flexibility? | St Spinosum. |
| What gives St Spinosum its 'spiny' appearance? | Large amounts of keratin filiment bundles called tonofiliments. |
| Which layer contains Langerhans cells? | St Spinosum. |
| Describe St Germinativum. | Simple cuboidal or columnar epithelium. |
| What does St Germinativum sit on? | Basement membrane next to dermis. |
| What attaches St Germinativum? | Hemidesmosomes. |
| What happens in St Germinativum? | Keratinocytes are formed by stem cells, cells undergo cell division by mitosis and push older layers up. |
| Where are melanocytes and Merkel cells present? | St Germinativum. |
| What makes up cornified zone? | Granulosum, Lucidum and Corneum. |
| What makes up Malpighian layer? | Germinativum and Spinosum. |
| What is the Malpighian layer? | Strata of metabolically active cells |
| The shedding or peeling of the epidermis in scales is? | Desquamation. |
| Formation of the epidermis is called? | Epidermopoiesis. |
| The process by which cells become horny due to deposition of protein within them? | Keratinization. |
| Fissuring occurs if? | Skin is too dry. |
| Maceration occurs if? | Skin is too wet. |
| Skin colour is determined by? | Haemoglobin, red and yellow; Carotenes, orange; Melanin, brown. |
| Does number of melanocytes affect skin pigment? | No skin pigment is determined by number of melanosomes, the organelle which produces melanin. Number of melanocytes in most human skin is the same. |
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HbombG41
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