1 Consists of the skin, hair, oil, sweat glands, nails and sensory
1.1 Functions of the skin
1.1.1 Regulates body temperature
1.1.2 Stores blood
1.1.3 Protects body from external environment
184.108.40.206 E.g Chemicals. Sunlight. Water loss. Microbes.
1.1.4 Detects sensations
1.1.5 Excretes and absorbs substances
220.127.116.11 E.g. urea in sweat. Sebum.
1.1.6 Synthesises vitamin D
2 SKIN STRUCTURE
18.104.22.168.1 Subcutaneous layer of loose, fibrous connective tissue
22.214.171.124 Inside layer
2.1.2 Outside layer
2.1.3 Dermo-Epidermal junction
126.96.36.199 Basement membrane that joins the Epidermis & Dermis
188.8.131.52.1 Composed of 3 layers:(Top) lamina lucida, lamina densa and lamina fibroreticularis (Bottom)
184.108.40.206.1.1 RETE RIDGES - projections down the way form the epidermis to the dermis. DERMAL PAPILLAE -
nipple shaped structures project into the undersurface of the epidermis.
220.127.116.11.1.1.1 Rete Ridges increase surface area for molecules passing between dermis and epidermis. Networks of tiny
blood vessels run through the ridges, bringing food,
vitamins and oxygen to the epidermis.
18.104.22.168.22.214.171.124 Rete Ridges are not present in the skins of unborn babies. Ageing skin - rete ridges get smaller and flatter.
2.1.4 5 layers of the epidermis
126.96.36.199 Stratum Corneum
188.8.131.52.1 Consists of large, flat, dead cells (10-30 cells thick) - keratinocytes/corneocytes arranged in parallel rows
184.108.40.206.2 Cells have lost all organelles and most water content
220.127.116.11.3 Cells are continuously shed and replaced by cells from the deeper strata. It's key role is to
prevent loss of moisture from tissues through evaporation - Transepidermal water loss
18.104.22.168.4 Intercellular space filled with cement which holds the cells together.
22.214.171.124.5 This keratinised layer consists of a soft keratin which helps keep the skin elastic
126.96.36.199.6 CORNIFIED ZONE - DEAD OR DYING CELLS
188.8.131.52 Stratum Lucideum
184.108.40.206.1 Body has 'thick' (glabrous/non-hairy) skin
220.127.116.11.2 Only appears in palms of hands and soles of feet
18.104.22.168.3 Acts as a protective shield against UV rays
22.214.171.124.4 Consists of 3-5 layers of flattened, clear, dead cells.
126.96.36.199.5 Contains a protein called Eleidin
188.8.131.52 Stratum Granulosum
184.108.40.206.1 Usually 3 to 5 layers thick of flattened keratinocytes
220.127.116.11.2 Keratinisation process begins
18.104.22.168.2.1 Newly formed cells in the St. Basale are slowly
pushed to the surface. As the cells move from one
epidermal layer to the next, they accumulate more
and more keratin.
22.214.171.124.3 Cells begin to die - the nuclei begins to disintegrate (lysosomes) along with other cellular organelles
126.96.36.199.4 The cells become flattened and accumulate large granules called keratohyaline.
188.8.131.52 Stratum Spinosum
184.108.40.206.1 8-10 layers of many sided keratinocytes fit closely together
220.127.116.11.1.1 Linked by desmosomes
18.104.22.168.1.2 Provides strength and flexibility to skin
22.214.171.124.2 Cell division & growth occuring
126.96.36.199.2.1 Cells possess large amounts of keratin filament bundles
188.8.131.52.3 Spiny/prickly layer
184.108.40.206.4 Contains non-keratinocyte cells called Langerhans cells
220.127.116.11.1 Composed of a single row of cuboidal or
18.104.22.168.1.1 Cells have an oval nucleus, prominent nucleoli, little heterochromatin (responsible for DNA/genes).
22.214.171.124.1.2 Have many mitochondria, free ribosomes, nuclei, may also have cytoskeletal filaments (actin
micro filaments and keratin filament bundles) and Tonofilaments.
126.96.36.199.1.2.1 Mitochondria - powerhouses of cell
188.8.131.52.1.2.2 Cytoskeletal - filaments -
give the skeleton to the cell
184.108.40.206.1.2.3 Tonofilaments - made up of keratin
converge together at the site of the
220.127.116.11.2 Some cells in this layer
are stem cells that
undergo cell division
continually produce new
18.104.22.168.3 Sits on basement membrane next to the dermis
22.214.171.124.4 Cells attached to the basement membrane by HEMIDESMOSOMES
126.96.36.199.5 Also contains
Melanocytes and Merkel
cells - both are types of
188.8.131.52.6 MALPIGHIAN LAYER - ACTIVE/GROWING CELLS
184.108.40.206 Cells being made/cell growth
2.1.6 Consists of stratified squamous epithelium.
220.127.116.11 There is continuous replacement of cells. Renewed every 15-30 days.
18.104.22.168.1 Does not contain blood vessels - AVASCULAR
22.214.171.124.1.1 It is translucent.
126.96.36.199.1.1.1 The palms and soles are thicker
2.1.7 Cells of the Epidermis - Keratinocytes - 90% of epidermal cells. Melanocytes - 10% - found mainly in Basale layer.
2.1.8 Langherhans cells (dendritic cells) found in Spinosum layer - important in immune reactions. Merkel cells
(dendritic cells) are found in Basale layer - gather sensory information (touch). Form desmosomes with
3 Integumentum means COVER
4 4.5-5 Kilos - skin weight of a normal adult
4.1 2m2 - surface area of skin
4.1.1 0.5mm thick -eyelids to 5mm think - upper back.
188.8.131.52 We lose about 30-40k of cells every minute
184.108.40.206.1 19 million cells are in each square inch of human skin
220.127.116.11.1.1 32 million bacteria are found on each square inch of human skin
5 Langer's/Cleavage Lines - lines of
tension within the skin. Surgeons try
to follow when making incisions -
heaiing is faster and scarring is
6 SKIN PIGMENTATION
6.1 The difference in pigmentation that
determines racial types is in the number of
MELANOSOMES, i.e. the organelle within
the melanocyte that produces pigment.
6.2 Disorders of Pigmentation: Albinism (involves a lack of Tyrosine), Vitiligo, Freckles