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Anatomy & physiology of skin & lair
Topics: Epidermis, Skin / Pages: 13 (3013 words) / Published: Dec 18th, 2013


1. Draw and label a diagram of the Epidermis.

2. Draw and label a diagram of the dermal and subcutaneous layer
Of the skin

Please make sure that you include all the things from the table below.

3. Fill in the following table:

Papillary layer Upper layer of dermis Provides nutrients for the living cells of epidermis
Reticular layer Second layer of dermis Collagen, elastic & reticular fibbers gives skin strength elasticity and support which all help to maintain skin’s tone.

Subcutaneous layer Situated below the dermis, consists of Adipose tissue(fat) and areola tissue Adipose tissue protects against injury and insulates keeping body warm.
Areola tissue elastic fibbers making layer strong and flexible
Eccrine glands Coiled tubular glands open directly onto skins surface Regulate body temperature, help eliminate waste
Apocrine glands Connected to hair follicles, only found in genital and underarm regions Produce a fatty secretion. Breakdown of secretion by bacteria and leads to body odour
Hair follicles Sac or sheath of epidermal cells and connective tissue, surrounds root of hair Holds hair in place and enclose the hair shaft, provides hair with vital nourishment – contains dermal papilla which supplies blood to hair
Sebaceous glands Small sac-like pouches Produce an oily substance known as Sebum (contains fat, cholesterol and cellular debris) coats surface of skin and hair shaft preventing excess water loss

Arrector pili Smooth muscle of sensory fibbers attached at angle to base of hair follicle Makes hair stand erect in response to cold or experiencing emotions as fright and anxiety
Blood vessels Runs through dermis and subcutaneous layers Brings nutrients and oxygen to germinating cells in the epidermis and remove waste products.
Sensory nerve ending All over body more on finger tips and lips Stimuli sends messages through sensory nerves to brain – aware of pain, touch, heat and cold
Motor nerve ending dermis Transmit impulses to the effector organs: muscles and glands.
Capillaries Throughout dermis and subcutaneous layer The site of where exchange of substances between blood and body tissues take place

4. List and discuss the functions of the skin
Sensation: contains sensory nerve endings which send messages to the brain. A nerve respond to touch, pressure, pain, and cold, hot and allows us to recognise things from their shape and feel.
Heat regulation: regulates body temperature by –
• Losing too much heat the blood capillaries near skins surface contract, keeping warm blood away from skins surface and closer to major organs.
• When body is too warn blood capillaries dilate allowing warm blood to flow near skins surface to cool the body.
• Evaporation of sweat from skins surface also assist in the cooling of the body.
• Arector pili muscles raise hairs and trap air next to the skin when heat is needed to be retained.
• Adipose tissue of the dermis and subcutaneous layers help insulate body against heat loss.
Absorption: skin is mostly waterproof and has limited absorption properties. However substances which the epidermis can absorb include fat soluble substances such as oxygen, carbon dioxide, fat soluble vitamins, steroids, along with small amounts of water.
Protection: acts as a protective organ –
• Fat cells of the subcutaneous layer protect bones and major organs from injury.
• Melanin – produced in basal layer, helps protect the body from harmful effects of ultra violet radiation.
• Cells located in the Horny layer overlap like scales prevent micro-organisms penetrating the skin and prevent excessive water loss from body.
• A film of sebum and sweat on the skins surface (acid mantle) acts as an anti-bacterial agent helping to prevent the multiplication of micro-organisms on the skin.
Excretion: eccrine glands produce sweat this helps to remove waste materials from the skin like uric acid, ammonia and lactic acid.
This is done through perspiration.
Secretion: sebum a fatty substance that’s secreted from the sebaceous gland on the skins surface. Keeps the skin supply and helps to waterproof it.
Vitamin D: A UV ray from the sun penetrate through skin layers and activates a chemical found in the skin known as Ergosterol, this changes into Vitamin D – this is essential for healthy bones and the absorption of calcium and phosphorus in the diet.

5. a. Name the 5 layers of the epidermis( common names)and make sure that you include in each:
i. Their functional significance ii. Cell regeneration and how each layer plays a part
Horny layer: - Stratum Corneum, most superficial outer layer of skin, consisting of 20-30 rows of flattened, keratinised and dead cells. Cells in this layer are shed and replaced continuously taking approximately a month to travel from the germinating layer. Also a protective barrier against light, heat, bacteria and many chemicals.
Clear Layer: - Stratum Lucidum, there are about 3-5 layers of flat dead cells filled with keratin – note these cells have no nuclei as they have undergone mitosis. This layer has transparent cells permitting light to pass through. The skins density varies as the facial skin is very shallow, but the soles of feet and palms of hands are thick and generally is absent in hairy skin.
Granular Layer: - Stratum Granulosum, 3-5 layers of flattened keratinocytes. Cells in this layer are distinctly shaped containing a number of granules that are involved in the hardening of cells by the process of keratinisation and in turn begin to die. This layer links the living cells of the epidermis to the dead cells above.
Prickle Cell Layer:- Stratum Spinosum, this layer is named after the shape of the cells because each rounded cell contained within it have short projections which make contact with neighbouring cells which give them a prickly appearance. 8-10 rows that are closely packed together, their long projections of melanocytes extend among keratinocytes this enables the transfer of melanin. The cells in this layer are living and are capable of dividing by the process of mitosis.
Basal Layer: - Stratum Germinativum, the deepest layer of the Epidermis consisting of a single layer of column cells on a basement membrane separating it from the Dermis. New epidermal cells are constantly being produced, these cells last approximately for 6 weeks from reproduction or when mitosis takes place before being discarded into the horny layer. New cells are formed by division, pushing adjacent cells towards skins surface, intervals between column cells that divide to reproduce are larger star-shaped cells called melanocytes, and these form the pigment melanin – main colouring agent for the skin.

b.What is desquamation ?
The continual process of shedding the dead cells from the Horny layer is known as desquamation.

6. What is Keratin? Its nature and function in relation to hair and skin.
A tough fibrous protein found in the epidermis, the hair and the nails. With regards to the skin: Keratin it found in the skin been constantly she. Keratinisation is the process cells undergo when change from living with nucleus to dead, horny cells without a nucleolus. The cells that have undergone keratinisation are therefore dead. Keratin has a protective function as the keratinised cells form a waterproof covering, helping to stop the penetration of bacteria and protects the body against minor injury.
Hairs are elongated keratinized structures, like other proteins in the body Keratin is also a large molecule made up of smaller units called Amino Acids, which are joined together in a chain (like beads on a string). Each hair arises from and indentation of the epidermis. The hair has two parts – Hair Follicle and Hair Shaft, the shaft is made up of dead cell that have turned into keratin and binding material, together with small amounts of water. This structure explains why we do not feel pain while hair is been cut. There are 3 layers that form the shaft – innermost is called Medulla which is only seen in large thick hairs, middle layer (cortex) made from keratin fibbers provides the strength, colour and texture of hair. The outermost layer (cuticle) thin and colourless made up of 6-10 overlapping layers of long cell remnants serving as a protection to the cortex – Keratin is not present in the follicle as this is the point from which the hair grows – living cell.

7. Discuss the following. To include function, development and where it is found

An oily substance that produced from the sebaceous gland that opens into a hair follicle but also onto the skins surface except palms of hands and soles of feet this substance contains fats, cholesterol and cellular debris, is mildly antibacterial and antifungal. Also coats skins surface and hair shafts to prevent excess water loss, lubricates/softens hair and the horny layer of the epidermis.
The secretion of sebum is stimulated by the release of hormones, primarily androgens
A thin oily film that sits on the top of the outer most layer of skin (Epidermis). Our slightly acidic skin helps fight harmful bacteria and any atmospheric chemicals that might enter our skin (these are mainly alkaline in nature) as our natural acidity neutralizes these harmful bacteria and chemicals – a similar way as milk of magnesia neutralizes stomach acid when heartburn strikes. This is part of the body’s defence system, and maintains the skins Ph levels is vital in protecting ourselves from harmful bacteria which can lead to acne, infection or irritation.
A dark pigment derived from amino acid tyrosine and secreted by melanocytes located in the deep germinative layer absorbed by surrounding epithelial cells. Protects skin from harmful effects of sunlight, this exposure promotes synthesis of melanin. The amount of melanin is genetically determined and varies between parts of body and between people of same ethnic origin and ethnic groups. Differences in colour depends on the amount of melanin is secreted but the number of melanocytes is fairly constant. Excessive levels of bile pigments in blood and carotenes in subcutaneous fat gives skin a yellowish colour, where the percentage saturation of haemoglobin and amount of blood circulating in dermis given skin its pink colour.

8. Draw and label a cross section of a nail and discuss each labelled area. Cuticle:- a fold of overlapping skin that surrounds the base of the nail. There are different areas of cuticle-
Eponychium – dead cuticle that adheres to the base of nail, near the lanula.
Peronychium – the part of cuticle that outlines the nail bed.
Hyponychium –skin found under the free edge of nail.
The function of the cuticle is to protect the matrix and provide a protective seal against bacteria.
Nail bed: situated immediately below nail plate and is a continuation of the matrix and is the part of which the skin upon the nail plate rests. It’s richly supplied with blood vessels, lymph vessels and nerves from the underlying dermis. Functions are to provide nourishment and protection for nail.
Free edge: part of nail that extends beyond the nail bed. This is the part that is filed and usually the hardest.
Matrix: located immediately below cuticle and is the nails most important feature – this is where living cells are produced. The matrix receives rich supply of blood that supplies oxygen to the nail, and is vital to the production of new cells. This is the area from which the health of the nail is determined.
Lanula: a light-coloured semicircular area of nail – commonly known as the half moon, lies between the matrix and nail plate. Lanula is always present but not always visible as it may be obscured by the cuticle. The cells in this area start to harden and are in a transitional stage (between hard and soft) therefore a bridge between living cells of the matrix and dead cells of nail plate.
Nail plate: main visible part of nail that rests on the nail bed and ends at the free edge. Made up of layers of translucent dead, keratinised cells that made the nail hard and strong. The cell layers are packed very closely together, with fat but very little moisture. Key function is to offer protection for nail bed.
Nail walls: these are folds of skin overlapping the sides of nails. They surround three sides of nail which are firmly attached to sides of nail plate. These nail walls are to protect the edges of nail plate from external damage.
Nail grooves: deep ridges under the sides of nail. As nail grows along with nail bed it passes along the nail grooves, which guide it and helps it to grow straight.

9. Draw and label a diagram of the hair in its follicle with surrounding structures

10. Draw and label a diagram of the 3 stages of hair growth.
A. Discuss each stage and the process by which hair
Moves through the follicle

Anagen: receives its nourishment to grow from dermal papilla and when removed it has a visibly developed bulb and inner root sheath intact the stages are:
• Active growing stage
• Lasts from a few months to several years
• Hair germ cells reproduce at matrix
• New follicle is produced which extends in depth and width
• The hair pass upwards to form hair bulb
• Hair cells continue rising up the follicle and as they pass through bulb they differentiate to form individual structures of hair.
• Inner root sheath grows up with hair, anchoring it into the follicle
• When cells reach upper part of bulb they become keratinised
• Two-thirds of the way up the follicle, hair leaves inner root sheath and emerges onto surface of skin.
Catagen: a column of epithelia cells remains in contact with the dermal papilla. As hair breaks from bulb its nourishment is received from the follicle wall. Catagen have no visible bulb when removed and appears shorted and dehydrated.
• Lasts approximately 2-4 weeks
• Transitional stage from active to resting
• Hair separates from dermal papilla and moves slowly up follicle
• Follicle below retreating hair shrinks
• Hair rises to just below level of sebaceous gland where inner root sheath dissolves and hair can be brushed out.
Telogen: hair has a is diminished blood supply, when removed has a small brim-like fibres at its end.
• Short resting stage
• Shortened follicle rest until stimulated again
• Hair is shed onto skin’s surface
• New replacement hair begins to grow
11. Draw and label a hair and describe all three sections Cuticle: outer layer that’s made up of transparent protective scales which overlap one another. Protects the cortex and gives hair its elasticity.
Cortex: middle layer that’s made up of tightly packed keratinised cells containing the pigment melanin (gives hair its colour). It also helps to give strength to the hair.
Medulla: inner layer, made up of loosely connected keratinised cells and tiny air spaces. This layer determines the sheen and colour of hair due to the reflection of light through the air spaces.

12. Name the types of hair found on the body Lanugo, Vellus and Terminal Hair
A. Where they are found
Lanugo – fine soft hair found on a foetus. Grows from around 3rd to 5th month of pregnancy, eventually shed and replaced by secondary vellus hairs around 8th & 9th month of pregnancy. Often unpigmented and lacks a medulla.
Vellus- Soft and downy found all over face and body except palms of hands and soles of feet, eyelids and lips. Again often unpigmented no medulla or a well developed bulb. They lie close to surface of skin therefore have shallow follicles. If hair is stimulated by increased blood circulation from hormonal charges like puberty, pregnancy or menopause or even medication, the vellus shallow hair follicle can grow downwards and become a coarse, dark terminal hair.
Terminal- These are longer and coarser hairs found on scalp, underarms, eyebrows, pubic areas, arms and legs and most are pigmented. Deeply seated in dermis and have well-defined bulbs. Varying greatly in its shape, diameter, length also colour and texture.
B. Discuss the difference between male and female
Hair growth
The Male hormone testosterones stimulate hair growth on face, pubic area, on the scalp and under arms and determine the thickness, the strength and how fast the hair will grow. These exact hormones may prompt the hair follicles on a man’s head to shrink, also hair is found to grow on the chest and back – here the hair is usually finer than hair on scalp face and pubic area. Where oestrogen is the dominate hormone found in females which promotes hair growth by counteracting the amount of testosterone produced. But if too many male hormones are produced then this could result in excessive hair growth this is known as HIRAUTISM. Again the strength, thickness and how fast it grows is determined on the amount of hormones produced.
Discuss differences in hair growth amongst various
Cultures i.e. Caucasian , Afro-Caribbean ,Asian, Chinese and Mediterranean
Caucasian: hair can be quite variable, as it can be straight, wavy or curly. Its fiber can be circular or oval in cross section and on average thinner than Asian. The hair follicle density also varies and can be approximately related to the colour of the hair. Red haired people have the least dense scalp hair growth, blonds been the most dense and brown haired people are somewhere in the middle. The density can range from 100,000 – 150,000 scalp hair follicles.
Afro-Caribbean: this type of hair is tightly coiled or spiral. The cross section is elliptical or almost flat and ribbon-like, this means there is more strength and rigidity to be fiber across the area of greatest cross section, but the hair is more pliable across the narrow section. Resulting in the curls of hair are all naturally flexing and coiling along the ribbon, while there is little or no coiling from side to side.
Asian: this is the thickest and most coursed hair compared to Caucasian & Afro-American. Its almost always straight and circular in cross section, been the lowest end of the spectrum the density of Asian hair may be just 90,000 scalp follicles and rarely gets above 12,000.
Chinese: characteristically hair is thick – up to 120 microns in diameter – round in shape and with relatively few twists per unit . Hair is uniform in colour (black) and usually straight.
Mediterranean: hair tends to contain more eumelanin, an apparent gradation of hair colour from light to dark. Hair is usually more greasy – humidity.

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