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Wk1 A&P


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Notes from week 1

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Wk1 A&P

  1. 1. Lesson Aims Recall names of the 3 layers of the skin Identify the layers of the Epidermis List the difference with the dermis & subcutaneous layer Label the appendages of the skin
  2. 2. The skin is made up of 3 main layers: Epidermis Dermis Subcutaneous layer
  3. 3. Epidermis This is the outermost layer of the skin (the part that you can see); it does not have a blood supply of its own and is made up of 5 layers: The Keratinisation Zone The skin cells begin to die in these layers. The cells become flatter, and harden. The Germinative Zone All these cells in the epidermis are living.
  4. 4. The stratum corneum This is the surface layer of skin, consisting of 25 to 30 cells deep of flattened irregular dead keratinised cells. This layer of skin is a waterproof protective covering, which prevents excessive dehydration of the tissues, hence the term horny layer. The stratum lucidum This layer lies below the stratum corneum and is four cells deep and a narrow transparent layer consisting of flattened and closely packed cells, with an indistinct outline and no nuclei hence the term clear layer. This layer is more pronounced in thick hairless skin, eg on the palms of the hands and soles of the feet. The stratum granulosum This is the third layer of the epidermis and is between one and three cells deep, consisting of flattened spindle shaped cells. The nucleus begins to breakdown here and granules of keratin appear, hence the term granular layer. This layer forms the main part of all horny tissue.
  5. 5. The stratum spinosum/prickle cell layer This layer is eight cells deep with round nucleated cells, which vary in size and shape and produce fibrils which interconnect them with neighbouring cells, hence often referred to as the prickle cell layer. The stratum germinativum/basal layer Within this layer cells are one cell deep, rounded and clearly defined with a nucleus, and rest on the papillae of the dermis. These epithelial cells are able to divide and reproduce themselves by a process called mitosis, hence the term germinative. As these cells form they push themselves up towards the skin surface. Within this layer there are also melanocyte cells, which produce the pigment melanin, which gives both the hair and skin its colour density. Langerhan cells are also found within this layer and absorb and remove foreign bodies that enter the skin.
  6. 6. Dermis This layer is often referred to as the true skin as it forms the bulk of the skin. It is composed of connective tissue, and is thicker than the epidermis. The dermis contains 2 layers: Papillary Layer This lies directly under the epidermis, it is quite thin and has cone. These contain nerve endings and blood capillaries. It provides nutrients and oxygen to the germinating layer of the epidermis Reticular Layer This lies below the papillary layer and is the main portion of the dermis. Within the reticular layer are collagen and elastin fibres. Read the description of dermis, and highlight key words on the notepad.
  7. 7. Hair Shaft Hair Follicle Arrector Pilli Muscle Blood Supply Subcutaneous Layer Dermis Epidermis Sensory nerve endings Sebaceous Gland Sweat Gland Hair Shaft Hair Follicle Arrector Pilli Muscles Blood Vessels Sebaceous Gland Nerve Endings Epidermis Dermis Subcutaneous Layer Sweet Gland