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Term Paper on Human Skin
Term Paper Contents:
- Term Paper on the Definition and Functions of Human Skin
- Term Paper on the Surface Area of Human Skin
- Term Paper on the Pigmentation of Human Skin
- Term Paper on the Structure of Human Skin
- Term Paper on Human Skin Appendages
Term Paper # 1.
Definition and Functions of Human Skin:
ADVERTISEMENTS:
Skin is the general covering of the entire external surface of the body. It is continuous with the mucous membrane at the orifices of the body.
Synonyms of skin are – cutis (L), derma (G) – integument.
Example:
Cutaneous, dermatology, dermatomes etc.
ADVERTISEMENTS:
Functions of Human Skin:
1. Protection from mechanical injuries, bacterial infections, heat and cold, wet and drought, acid and alkali and rays of Sun.
2. Sensory- to touch, pain and temperature.
3. Regulation of body temperature- heat is lost through evaporation of sweat and conserved by fat and hair.
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4. Absorption of oily substances.
5. Secretion of sweat and sebum.
6. Excretion of excess of water, salts and waste products through sweat.
7. Regulation of pH by excretion of acid in sweat.
ADVERTISEMENTS:
8. Synthesis of vitamin D from ergosterol by action of ultraviolet rays of Sun.
9. Storage of chlorides.
10. Reparative- cuts and wounds heal quickly.
Term Paper # 2.
Surface Area of Human Skin:
ADVERTISEMENTS:
In an adult total surface area of skin is 1.5 to 2 sq. meters.
Area involved in cases of burns can be assessed by following:
Rule of Nine:
Head and neck – 9%
ADVERTISEMENTS:
Each upper limb – 9%
Front of the trunk – 18%
Back of the trunk (including buttocks) – 18%
Each lower limb – 18%
Perineum – 1%
Dubois Formula:
For calculation of skin surface area of a person- Surface area in sq. cm = weight in kg × height in cm. × 71.84
A = W × H × 71.84
Term Paper # 3.
Pigmentation of Human Skin:
Five pigments present at different levels and places of skin – which gives colour to it are:
1. Melanin:
Brown in colour and present in germinative zone of the epidermis.
2. Melanoid:
Resembles melanin, present diffusely throughout the epidermis.
3. Carotene:
Yellow to orange in colour, present in stratum corneum and fat cells of dermis and superficial fascia.
4. Haemoglobin:
Purple.
5. Oxyhaemoglobin:
i. Red, present in cutaneous vessels.
ii. Pigment vary with race, age and part of body
iii. Colour of skin depends on – pigments and vascularity of dermis
iv. Thickness of keratin
v. Colour is red – where keratin is thin, e.g., lips
vi. Colour is white – where keratin is thick, e.g., palms and soles
vii. Thickness of skin varies from about 0.5 – 3 mm.
Term Paper # 4.
Structure of Human Skin:
Human skin structure is composed of two layers:
I. Epidermis and
II. Dermis.
I. Epidermis:
It is superficial, avascular layer of stratified squamous keratinized epithelium.
Ectodermal in origin.
Gives rise to appendages of skin, e.g., hair, nails, sweat gland and sebaceous gland.
It has:
a. Superficial – Cornified Zone:
Stratum corneum
Stratum lucidum
Stratum granulosum.
b. Deep – Germinative Zone:
Stratum spinosum (polyhedral cells).
Stratum basale (columnar cells).
Cells of basal layer – proliferate and pass towards surface to replace cornified cells lost due to wear and tear.
Basal cells also contain – melanocytes. These synthesis the pigment melanin.
It synthesizes – melanin.
II. Dermis:
It is deep and vascular layer which is derived from mesoderm.
This is made-up of connective tissue – with variable elastic fibres mixed with blood vessels, lymphatics and nerves.
Connective tissue is arranged into a superficial papillary layer and deep reticular layer (white fibrous tissue in parallel bundles).
Direction of bundles – constitute cleavage lines (Langer’s line) longitudinal in limbs and horizontal on trunk and neck.
In old age elastic fibres atrophy and skin becomes wrinkled.
Over stretching of skin leads to rupture of fibres and scar formation which form white streaks on skin. For example- Linea gravida.
Surface Irregularities of the Human Skin:
i. Tension Lines:
Form a network of linear – furrows – which divide the surface into polygonal areas.
Correspond to variations in the pattern of fibres in dermis.
ii. Flexure Lines (Skin Creases or Skin Joints):
Skin folds during flexion – skin is thin and firmly bound to deep fascia, e.g., skin of soles, palms and digits.
iii. Papillary Ridges (Friction Ridges):
Confined to palms, soles and their digits – form narrow ridges separated by fine parallel grooves arranged in curved arrays.
They correspond to dermal papillae.
Helps in finger prints recognition – loops, whorls and arch controlled – genetically by multifactorial inheritance.
Term Paper # 5. Human
Skin Appendages:
Human skin appendages are:
I. Nails,
II. Hairs,
III. Sweat and
IV. Sebaceous glands.
I. Nail:
Nails are hardened keratin plates on the dorsal surface of fingers.
Parts of Nail:
(a) Root:
Is proximal hidden part, buried into nail groove and is overlapped by nail fold of skin.
(b) Free Border:
Distal free part of nail.
(c) Body:
Exposed part of nail adherent to underlying skin. Proximal part of body has a white opaque crescent – called Lunule.
(d) Nail Wall:
Lateral border of nail body is overlapped by a fold of skin.
(e) Nail Bed:
Germinative zone and corium beneath the root and body of nail is nail bed.
Germinative zone beneath the root and lunule is thick and proliferative is responsible for growth of nail.
Rest of the nail bed is thin (sterile matrix) over which growing nail glides.
1. In anaemia – Nails are pale, white thin, brittle and spoon shaped (koilonychias).
2. Clubbing – Hypertrophy of nail bed occurs in chronic suppurative disease, e.g., lung abscess, osteomyelitis, bronchiectasis.
3. Cyanosis – Nails become blue due to lack of oxygen.
Average growth of nail is about 0.1 mm per day or 3 mm per month.
Growth is faster in summer than winter. Growth is faster in fingers than toes.
Whole nail grows in 90-129 days.
4. In fungal infections of nail – Course of treatment should be for 3-4 months.
II. Hair:
Hair is keratinous filaments derived from invaginations of the germinative layer of epidermis into dermis.
Help in conservation of body heat.
Distributed all over the body except – palms, soles, dorsal surface of distal phalanges, umblicus etc.
Length, thickness and colour of hair – vary in different, parts of body and in different individuals.
Parts of Hair:
1. Root is implanted part
2. Shaft is projecting part.
Hair Follicle:
It is formed by expanded proximal end of root which is invaginated by a tuft of neurovascular connective tissue and its sheath.
Hair grows by proliferation of cells capping the papilla.
Arrectores pilorum – smooth muscle fibres connect the hair follicles to dermal papilla. Contraction leads to erection of hair and squeezes out sebum.
Shaft of hair – is made up of medulla, cortex and cuticle.
III. Sweat Glands:
(Sudoriferous) are distributed all over the body except – lips, glans penis, nail bed etc.
Types:
i. Eccrine
ii. Apocirne.
i. Eccrine Glands:
Abundant and present in every part of skin. It has a single tube (duct) deep part is coiled called body of the gland which lies in deeper part of skin or in subcutaneous tissue.
Produce – thin watery secretion.
Help in regulation of body temperature by evaporation of sweat.
Supplied by sympathetic nerves.
Excreting body salts.
ii. Apocrine Glands:
Confined to axilla, eyelids, nipple and areola of breast, perianal region and external genitalia.
Glands are larger and produce thicker secretion having a characteristic odour (chemical signals or pheromones).
On an average – 1 liter sweat is secreted per day.
Through lungs – 400 ml of water lost.
In faeces – 100 ml of water lost.
Total water loss per day from a person is about 1500 ml.
In summer – increase sweating – water loss 3-10 liters/day.
Regeneration of skin – occurs if sweat glands are intact
Skin is dry in – dhatura poisoning, heat stroke, diabetics
Sweating – in coma, shock, hypoglycaemic coma, M.I. (Myocardial Ischemia)
IV. Sebaceous Glands:
Produce oily secretion widely distributed all over dermis of skin except – palms and soles, abundant – in scalp and face, around apertures of ear, nose, mouth and anus.
i. Superficial Fascia:
Subcuteneous tissue or hypodermis or tela subcutanea or panniculus adiposus
It is a general coating beneath the skin.
Made up of loose areolar tissue with varying amount of fat (adipose tissue).
Distribution of Fat in this Fascia:
1. Fat is abundant in gluteal region, lumbar region, anterior abdominal wall lower part, mammary gland etc.
2. In females – fat is more and evenly distributed.
3. Fat is absent in eyelids, external ear, penis and scrotum.
4. Subcutaneous layer of fat is called panniculus – adiposus.
5. Fat fills hollow spaces, e.g., orbits, axilla, ischio rectal fossa.
6. Fat is present around kidneys and supports it.
Types of Fat:
a. Yellow – most of fat is yellow.
b. Brown fat – found in hibernating animals.
Important Features:
1. Most distinct in lower part of anterior abdominal wall etc.
2. It is very thin on dorsal aspect of hand and feet, sides of neck and face etc.
3. Very dense in scalp, palms and soles.
4. It contains- Muscles in face, neck and scrotum, Mammary gland, Lymph nodes, Cutaneous nerves and vessels, Sweat glands.
Functions of Superficial Fascia:
1. Facilitates movements of skin.
2. It serves as soft medium for passage of vessels and nerves to skin.
3. Conserves body heat – fat is a bad conductor of heat.
ii. Deep Fascia:
It is a fibrous sheet which invests the body beneath the superficial fascia. It is devoid of fat usually – inelastic and tough.
Distribution Deep Fascia:
Best defined in limbs – it forms tough and tight sleeves.
Ill-defined on trunk and face.
Important Features Deep Fascia:
1. Extensions of deep fascia form – intramuscular septa – divide the muscle into compartments.
2. Thickenings – form – retinacula – are retention bands around wrist and ankle joints. Palmar and planter aponeurosis for protection.
3. Interruptions in deep fascia on subcutaneous bones.
4. Deep fascia forms sheaths around large arteries and veins, e.g., carotid sheath, axillary sheath etc.
5. Forms capsule, synovial membrane and bursae in relation to joints.
6. Forms tendon sheath and bursae where tendon cross over a joint – prevents wear and tear of tendon.
Functions of Deep Fascia:
1. It keeps underlying structures in position and preserves the surface contour of limbs.
2. Provides extra surface for muscular attachment.
3. Helps in venous and lymphatic return.
4. Retinacula – acts as pulley and prevent the loss of power.
5. Assists muscles in their action by degree of tension and pressure it exerts upon their surfaces.