Integumentary system

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1. INTEGUMENTARY SYSTEM

2. Introduction The integumentary system is the organ system that protects the body from various kinds of damage, such as loss of water or abrasion from outside. The system comprises the skin and its appendages (including hair, scales, feathers, hooves, and nails).

3. Functions Protects the body's internal living tissues and organs Protects against invasion by infectious organisms Protects the body from dehydration Protects the body against abrupt changes in temperature Helps dispose of waste materials Acts as a receptor for touch, pressure, pain, heat, and cold Stores water and fat

4. INTRODUCTION Largest organ of the body Covers an area of 2 square mtrs Weighs 4.5-5 kg

5. THICKNESS OF SKIN Average thickness is 1-2 mm 5mm – sole of the foot, palm of the hand & interscapular region 0.5 mm – over the eyelids and penis

6. Layers of the Epidermis Stratum basale : consist of predominantly single row of keratinocytes ; some melanocytes (10-25%) and Merkel cells; Stratum spinosum : several layers thick; Contains flattened irregularly-shaped keratinocytes , pre-keratin intermediate filaments. Stratum granulasum : consist of flattened keratinocytes which accumulate keratohyaline granules (granules form keratin) and lamellated granules (produce water-resistant chemical).

7. Stratum lucidum : present only in thick skin and made up of a few rows of clear, flat, dead keratinocytes . Stratum corneum : outermost layer, conts many layers of cells ( cornified or horny cells). Dead skins slough off.

8. EPIDERMAL CELLS Keratinocytes Melanocytes Langerhans cells Merkel cells

9. KERATINOCYTES 90% Produce the protein keratin Helps protects the skin & underlying tissues from heat, microbes & chemicals.

10. MELANOCYTES 8% Produce the pigment melanin Melanin is a yellow-red or brown-black pigment Skin colour Absorbs UV light

11. Langerhans cells: star-shaped cells from bone marrow. Function to activate the immune system as macrophages. Merkel cells: function as sensory receptors

12. THIN & THICK SKIN THIN:- Absence of stratum lucidum THICK:- 5 layers

13. DERMIS Is composed of blood vessels, nerves, glands and hair follicles Layers : Superficial papillary Deeper reticular

14. Papillary layer : Consists of areolar connective tissue made up of loose collagen and elastic fibers , projections called papillae which contain touch and pain receptors ( Messsner’s corpusles ). The papillae also form epidermal ridges found on the surfaces of palms, fingers and feet. On the palm and fingers they form the fingerprints (genetic markers of individualilty ). 

15. Reticular layer : account for about 80% of thickness of dermis; consist of dense irregular connective tissue . The ECM of this layer consist of bundles of collagenous fibers which run in parallel and opposite directions. The fibers give strength and resilience (toughness) and recoil, while collagen absorbs water and keep the skin hydrated. Stretch marks found on the buttocks, thighs, abdomen and breast are due to these fibers. Disturbances of the skin Stretch and tear; blisters

16. SUBCUTANEOUS Also called as hypodermis Consist of adipose tissues & large blood vessels

17. It invaginates into the dermis and is attached to the latter, immediately above it, by collagen and elastin fibres . It is essentially composed of a type of cell known as adipocytes specialised in accumulating and storing fats. These cells are grouped together in lobules separated by connective tissue.

18. The hypodermis acts as an energy reserve. The fats contained in the adipocytes can be put back into circulation, via the venous route, during intense effort or when there is a lack of energy providing substances, and are then transformed into energy. The hypodermis participates, passively at least, in thermoregulation since fat is a heat insulator.

19. SKIN COLOUR Melanin Hemoglobin Carotene

20. Melanin is a brown-black pigmentation formed in cells called melanocytes . Cells are found in the stratum basale and spinosum . The amount of melanin produced by an individuals is based on inheritance. Freckles are small patches of Melanin on the skin due to uneven distribution. Hemoglobin is the molecules found in RBC that gives blood its red coloration. It is made of non-protein ( heme which contains iron) and the protein ( globin ).

21. Carotene is the yellowish pigment found in the corneum and the dermis. Skin color of human races occur as a result of the relative abundance of melanin and carotene. Dark-skin coloration is due to melanin. Caucacians produce more carotene than melanin. Melanin protects the skin and cells of the skin by shielding the UV light of the sun against the nucleus.

22. ACCESSORY STRUCTURES Hair Skin glands Nails

23. HAIR Pilli Heavily distributed on scalp, eyebrows, axillae & external genitalia formed of keratinized cells and consist of two parts: a shaft and root. The shaft is above the skin and root embedded in the dermis, in a hair follicle connected to blood supplies and arrector muscle.

24. ANATOMY OF A HAIR Shaft Root Parts of the root Medulla Cortex Cuticle Hair follicle

25. Internal root sheath External root sheath Dermal root sheath Onion shaped base Papilla – nourishes the follicle Matrix – growth & produce new hair

26. HAIR GROWTH Growth stage – 2 to 6 yrs, 85% of hairs Resting stage – 3 months Normal hair loss – 70 to 100 hairs per day. Alopecia

27. HAIR TYPES Lanugo Vellus hairs Terminal hairs

28. Nail   Nail : they are formed of keratinized epidermal cells and occur on the finger and toes. Consist of a visible area (body) and the root (embedded in the dermis).

29. SKIN GLANDS Sebaceous Sudoriferous Ceruminous

30. SEBACEOUS GLANDS Sebaceous or oil glands are simple or branched alveolar glands situated in the dermis of the skin. Secretes sebum Ovoid or spherical in shape

31. COMPOSITION OF SEBUM Free fatty acids Triglycerides Squalene Sterols Waxes Paraffin

32. FUNCTIONS OF SEBUM Prevents the hair from drying & becoming brittle Prevents excessive evaporation of water Inhibits the growth of bacteria

33. SUDORIFEROUS GLANDS Otherwise called as sweat glands 3-4 millions are present Releases sweat or perspiration through pores TYPES:- Eccrine Apocrine

34. APOCRINE Non functional till puberty Secretions are thick Odour

35. APOCRINE Axilla Groin Areolae Bearded regions in male Pubis Umbilicus

36. CERUMINOUS They are modified sweat glands in the ear producing a waxy secretions called as cerumen or earwax Prevents entry of foreign bodies

37. NAILS Nail body Free edge Nail root Nail matrix – it growths 1mm per weak

38. FUNCTIONS Grasp & manipulate small objects Protects against trauma to the ends of the digits To scratch various parts of the body