Integumentary system

integumentary system, akin and its appendages

1. INTEGUMENTARY SYSTEM BY SONI KUMARI SHAH

2. Integumentary System Integumentary system i s an organ of our body which protects the body from damage. It consists of skin and its appendages which are nails, hair, sweat gland and sebaceous gland.

3. Functions Of Integumentary System It protects the underlying structures from injury and from invasion by microbes. It contains sensory nerve endings that enable discrimination of pain, temperature and touch It is involved in the regulation of body temperature . It is also a source of vitamin D synthesis. It excretes wastes.

4. Skin The skin completely covers the body and is continuous with the membranes lining the body orifices. Largest organ Constitutes 15-20% of total body mass Total area of body surface covered by skin is about 2 m 2 Thickness of skin varies from 0.3 mm to 3mm

5. Skin Receptors Nociceptors- physical, mechanical or chemical stimulus Merkle’s disc- light touch Pacinian corpuscles-pressure or fast vibration ruffini’s end bulb-heat Krause end bulb-cold

6. Pigmentation of Skin: Determined by five pigments present at different level and place of skin Melanin (brown) Melanoid (brown) Carotene (yellow to orange) Haemoglobin (purple) Oxyhaemoglobin (red)

7. Functions Of Skin: Protection Sensory Regulation of body temperature Absorption Secretion Excretion Regulation of pH Synthesis

8. The main functions of the skin include: A. support, nourishment, and sensation. B. protection, sensory perception, and temperature regulation. C. fluid transport, sensory perception, and aging regulation. D. protection, motor response, and filtration . Which of the following is NOT a sensory receptor of the skin? A. Meissner corpuscle B. A pocrine gland C. R oot hair plexus D. N ociceptor Which one of the following cell types is responsible for forming the skin’s ability to tan on exposure to sunlight? A. Melanocytes . B. Keratinocytes . C. D endrocytes . D. Lymphocytes .

9. Structure of Skin: Two layers a. Superficial layer, the epidermis b. Deeper layer, the dermis Below the dermis lies subcutaneous layer or hypodermis

10. The Epidermis: It is the outer layer of skin formed by stratified squamous keratinized epithelium. It does not have blood vessels so nutrition is provided by capillaries of dermis. Five layers: 1. Stratum Basale 2. Stratum spinosum 3. Stratum granulosum 4. Stratum lucidum 5. Stratum corneum

11. Stratum Basale : It is the thickest layer made up of superficially polygonal cells and in deeper parts columnar cells. T he skin color depends on the cells of this layer which contain melanin pigment. 2. Stratum Spinosum: I t is also known as prickle cell layer as cells of this layer possess spine like cytoplasmic projections. 3. Stratum Granulosum: It is a thin layer with 2-5 row of flattened rhomboidal cells. 4. Stratum Lucidum : It is made up of flattened epithelial cells. Many cells have degenerated nucleus and in some cells the nucleus are absent. These cells exhibit shiny appearance. 5. Stratum Corneum : It is known as horny layer. It is the outermost layer and consists of dead cells known as keratin cells.

12. Cells of Epidermis: Keratinocytes Melanocytes Dendritic cells of Langerhans Cells of M erkel

13. Healthy epidermis depends upon three processes being synchronized : D esquamation (shedding) of the keratinized cells from the surface. E ffective keratinization of cells approaching the surface. C ontinual cell division in the deeper layers with newly formed cells being pushed upwards to the surface.

14. The Dermis It is the inner vascular layer of skin made up of connective tissue and collagen fibers Two layers: Papillary layer(outer layer): I t projects into epidermis and contains blood vessels, lymph vessels and nerve fibers. Reticular layer(inner layer): I t is made up of elastic and reticular fibers and consists of mast cells, nerve fibers, lymph vessels, epidermal appendages and fibroblast.

15. Subcutaneous Layer Or Hypodermis It lies below the dermis. It is a loose connective tissue which connects skin with internal structures of the body. It serves as an insulator to protect the body from excessive heat or cold of the environment.

16. Differences Between Epidermis And Dermis SN Epidermis Dermis 1. It is the outer layer of skin. It is the inner layer of skin. 2. It is avascular. It is vascular. 3. It is formed by keratinized stratified squamous epithelium. It is formed by connective tissue and collagen fibers. 4. It is made up of five layers: stratum corneum , stratum lucidum , stratum granulosum, stratum spinosum and stratum basale . It is made up of two layer: papillary layer and reticular layer.

17. Types of Skin Thin Hairy skin Thick Glabrous Skin

18. Thin Hairy Skin Epidermis is very thin. It contains hair. Found in all other parts except palms and sole

19. Thick Glabrous Skin Epidermis is very thick. It has thick layer of Stratum corneum . It has no hair. Found in palms of hand and soles of foot.

20. Histology of skin

21. The outermost layer of the skin is the: A. epidermis. B. dermis. C. hypodermis. D. papillary dermis . Which of the following layer of skin does not contain blood vessels? Dermis Cutis Epidermis All of above The layer of epidermis that sheds keratin cells that are constantly replaced is Stratum lucidum Stratum corneum Stratum mucosum Stratum granulosum

22. Stratum corneum is composed of Melanin Granules Keratin cells Squamous cells In human body, the thickest skin is located on Thigh Buttocks Abdomen Palm and soles Which part of the skin is often referred as true skin? Stratum corneum Stratum spinosum Dermis Epidermis

23. Regulation Of Body Temperature By Skin Nervous Control The temperature regulating center in the hypothalamus is sensitive to the temperature of circulating blood. The vasomotor center in the medulla oblongata controls the diameter of small arteries and arterioles. The vasomotor center is influenced by the temperature of its blood supply and by nerve impulses from the hypothalamus. Activity Of The Sweat Glands When body temperature is increased by 0.25 to 0.5°C the sweat glands secrete sweat onto the skin surface. Evaporation of sweat cools the body.

24. Effects Of Vasoconstriction And Vasodilation As body temperature rises , the arterioles dilate and more blood enters the capillary network in the skin. The skin is warm and pink in color. In addition to increasing the amount of sweat produced , the temperature of the skin rises and more heat is lost by radiation, conduction and convection. If the environmental temperature is low or if heat production is decreased, the arterioles in the dermis are constricted. This reduces blood flow to the body surface, conserving heat. The skin appears paler and feels cool.

25. Regulation of Increase in Body Temperature Body temperature increased Stimulation of heat loss center (anterior hypothalamus) No shivering Inhibition of sympathetic activity Decreased adrenal secretion and metabolic rate Vasodilation of blood vessels suppling skin Increase in blood flow to skin Stimulate sweat gland Increase in sweat production Evaporation of sweat from skin takes the heat away from the body Decrease in heat production Decrease body temperature Body temperature becomes normal

26. Regulation o f D ecrease in Body Temperature Body temperature decreased Stimulation of heat gain center (posterior hypothalamus) S hivering Increased sympathetic activity Increased adrenal secretion and metabolic rate Vasoconstriction of blood vessels suppling skin Decrease in blood flow to skin S weat gland is inactive Decrease in sweat production Body heat is conserved Increase in heat production Increase body temperature Body temperature becomes normal

27. Formation of Vitamin D 7-Dehydrocholesterol is a lipid-based substance in the skin and is converted to vitamin D by sunlight. This vitamin is used with calcium and phosphate in the formation and maintenance of bone.

28. The skin begins the production of vitamin D in which of the following situations? When A. Exposed to ultraviolet radiation. B. S ignaled to by the hormone PTH. C. Calcium is present. D. It adds an hydroxyl group to a cholesterol molecule.

29. Appendages of Skin Hairs Sebaceous glands Sweat glands Nails

30. Hairs Hairs grow from hair follicles , downgrowths of epidermal cells into the dermis or subcutaneous tissue. At the base of the follicle is a cluster of cells called the hair papilla or bulb . The part of the hair above the skin is the shaft and the remainder , the root . Hair color is genetically determined and depends on the amount and type of melanin present. White hair is the result of the replacement of melanin by tiny air bubbles .

31. Hair

32. Arrector pili These are little bundles of smooth muscle fibers attached to the hair follicles. Contraction makes the hair stand erect and raises the skin around the hair , causing ‘goose flesh ’ or ‘goose bumps’. The muscles are stimulated by sympathetic nerve fibers in response to fear and cold .

33. Sebaceous Glands These consist of secretory epithelial cells derived from the same tissue as the hair follicles . They secrete an oily antimicrobial substance, sebum , a mixture of keratin, fat, and cellulose debris into the hair follicles and are present in the skin of all parts of the body except the palms of the hands and the soles of the feet . Sebum keeps the hair soft and pliable and gives it a shiny appearance . It also prevents drying and cracking of skin, especially on exposure to heat and sunlight.

34. Sebaceous Gland The activity of these glands increases at puberty and is less at the extremes of age, rendering the skin of infants and older adults prone to the effects of excessive moisture ( maceration ). Composition Of Sebum Free fatty acids, Triglycerides, Squalene, Sterol, waxes and paraffin.

35. Sebaceous Glands

36. Sweat Glands Sweat glands are widely distributed throughout the skin and are most numerous in the palms of the hands, soles of the feet , axillae and groins. They are formed from epithelial cells . The bodies of the glands lie coiled in the subcutaneous tissue . There are two types of sweat gland: E ccrine sweat gland A pocrine sweat gland

37. Types Of Sweat Glands Eccrine sweat glands are the more common type and open onto the skin surface through tiny pores, and the sweat produced here is a clear, watery fluid important in regulating body temperature. Apocrine sweat glands open into hair follicles and become active at puberty. They may play a role in sexual arousal. These glands are found, for example, in the axilla. Bacterial decomposition of their secretions causes an unpleasant odor . A specialized example of this type of gland is the ceruminous gland of the outer ear, which secretes earwax

38. Sweat Glands

39. Sweat Gland continued….. The most important function of sweat is in the regulation of body temperature. Excessive sweating may lead to dehydration and serious depletion of sodium chloride unless intake of water and salt is appropriately increased. Composition Of Sweat Water, sodium chloride, urea and lactic acid.

40. Nails Human nails are equivalent to the claws, horns and hooves of animals. Derived from the same cells as epidermis and hair these are hard, horny keratin plates that protect the tips of the fingers and toes . The root of the nail is embedded in the skin and covered by the cuticle, which forms the hemispherical pale area called the lunula . The nail plate is the exposed part that has grown out from the nail bed , the germinative zone of the epidermis. Finger nails grow more quickly than toe nails and growth is faster when the environmental temperature is high.

41. Nails

42. Which integumentary system structure is considered an epidermal appendage ? A. Blood vessel B. Nerve C. Stratum basale D. Hair Sebum is a mixture of: A. cellulose debris, fat, and keratin. B. collagen and elastin. C. watery fluid and sodium. D. protein, water, and electrolytes . The sweat glands that are widely distributed throughout the body are: A. apocrine. B. eccrine. C. adipose. D. sebaceous.

43. Which glands secrete “oil” into a hair follicle? A. apocrine B. eccrine C. ceruminous D. Sebaceous What do the apocrine glands of the skin secrete? A. apocrine B. ceruminous C. milk D. sweat

44. Wound Healing Conditions required for wound healing Systemic factors These include good nutritional status and general health. Infection, impaired immunity, poor blood supply and systemic conditions, e.g. diabetes mellitus and cancer, reduce the rate of wound healing. Local factors Local factors that facilitate wound healing include a good blood supply to provide oxygen and nutrients and remove waste products, and freedom from contamination by, e.g., microbes, foreign bodies or toxic chemicals .

45. Primary Healing (Healing By First Intention) This type of healing follows minimal destruction of tissue when the damaged edges of a wound are in close apposition, e.g . a surgical incision. There are several overlapping stages in the repair process.

46. Secondary Healing (Healing By Second Intention) This type of healing follows extensive tissue destruction or when the edges of a wound cannot be brought into apposition , e.g. varicose ulcers and pressure ( decubitus) ulcers . The stages of secondary healing are the same as in primary healing; healing time depends on effective removal of the cause and the size of the wound.

47. Burns These may be caused by many types of trauma including: heat , cold, electricity, ionizing radiation and corrosive chemicals , including strong acids or alkalis (bases). Local damage occurs disrupting the structure and functions of the skin.

48. Types Of Burn First degree when only the epidermis is involved, the surface is moist and there are signs of inflammation including redness, swelling and pain. There are no blisters and tissue damage is minimal. Second degree when the epidermis and upper dermis are affected. In addition to the signs and symptoms above , blistering is usually present. Third degree (deep or full thickness) when the epidermis and dermis are destroyed. These burns are usually relatively painless as the sensory nerve endings in the dermis are destroyed. After a few days the destroyed tissue coagulates and forms an eschar , or thick scab, which sloughs off after 2 to 3 weeks .

49. Burns In circumferential burns , which encircle any area of the body, complications may arise from constriction of the part by eschar, e.g. respiratory impairment may follow circumferential burns of the chest, or the circulation to the distal part of an affected limb may be seriously impaired. Skin grafting is required except for small injuries. Healing , which is prolonged, occurs by secondary intention and there is no regeneration of sweat glands, hair follicles or sebaceous glands. Resultant scar tissue often limits movement of affected joints.

50. Burns The extent of burns in adults is roughly estimated using the ‘ rule of nines ’. In adults, hypovolaemic shock usually develops when 15% of the surface area is affected . Fatality is likely in adults with third degree burns if the surface area affected is added to the patient’s age and the total is greater than 80.

51. Complications Of Burns Although burns affect the skin, when extensive, their systemic consequences can also be life-threatening or fatal. Dehydration and H ypovolemia These may occur in extensive burns when there is excessive leakage of water and plasma proteins from the damaged skin surface. Shock This may accompany severe hypovolemia . Hypothermia This develops when excessive heat is lost in leakage from burns.

52. Complications Of Burns Infection This occurs easily when subcutaneous tissue is exposed to the environment and may result in septicaemia . Renal failure This occurs when the kidney tubules cannot deal with the large amount of waste from haemolyzed erythrocytes and damaged tissue. Contractures These may develop later as fibrous scar tissue contracts distorting joints, e.g. the hands, restricting their range of motion.

53. Management Of Burns First Aid Stop the burning process Remove the person from source of burn Removal of cloth Ensure adequate airway Remove from smoke Cover the burn surface with clean dresses as quicklyS as possible Transfer to hospital for definite treatment

54. People with full thickness burns to more than 20 % of their body are in a life threatening situation . This is due to which of the following? A. The body’s inability to thermoregulate . B. The loss of the ability to produce vitamin D. C. The buildup of urea and uric acid which would otherwise have been excreted by the skin. D. The body’s inability to prevent water loss