PHYLOGENY OF THE OUTER INTEGUMENT OF VERTEBRATES.pptx

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1. PHYLOGENY OF THE OUTER INTEGUMENT OF VERTEBRATES . SUBMITTED BY :KUMKUM BHATIA

2. INTEGUMENT Integument: The skin and its derivates Skin: external body covering, continuous with the mucus membrane lining of buccal cavity, rectum , eyelids, eye-conjunctiva and urogenital duct. Barrier between external and internal environment The type of external environment whether aquatic or terrestrial , influences the characters of skin. Evolution of vertebrate integument is correlated with the transition of vertebrates from aquatic to terrestrial environment.

3. General structure of integument Vertebrata skin bears 2 layers : Epidermis and Dermis Relative abundance of two layers depends on environment Epidermis and dermis are closely united but differ greatly in their nature and origin

4. Epidermis the outer layer; derived from embryonic ectoderm. It is stratified squamous epithelium (multilayered). Lowermost layer resting on basement membrane is a layer of columnar living cells called Stratum germinativum or stratum Malpighi. Cells of stratum germinativum divide mitotically forming upper layers. Outer region of many layers of flattened (squamous) keratinized cells is stratum corneum. Keratin: a kind of tough, insoluble and waterproof protein. Keratinization: replacement of cellular cytoplasm by keratin.

5. Epidermis(contd.) Stratum corneum provides protection against mechanical and chemical injuries, fungal/bacterial infection and loss of body moisture. Cells of stratum corneum are periodically moulted. It is thin, bearing mucous glands in aquatic vertebrates. It is thicker in terrestrial vertebrates with scales, feathers, hairs, nails, claws, horns etc. Epidermis is separated from dermis by a thin and noncellular bilayered basement membrane made of glycoproteinous substance (2 layers- basal lamina + reticular lamina).

6. Dermis/ Corium: It is thicker.  It bears fibrous connective tissue, blood vessels, lymph vessels, nerve fibres, sensory corpuscles, white collagen fibres and yellow elastic fibres. It also bears some branched/stellate cells Called Chromatophores. Chromatophores are of three types: : contain brown to black melanin. Lipophores/Xanthophores: contain yellow-red fatty pigment. Iridocytes/ Guanophores : contain crystals of guanine which refract light.

7. Major functions of integument 1. Protection  Against mechanical and chemical injuries Against loss of moisture Against bacterial/fungal infection Spine, claws, nails, hooves, horns etc. serve for offence and defense . Protective colouration serves to escape from enemies. Against solar radiation. 2 . Secretion • Mucous glands, poison glands, uropygial glands in birds, sebaceous glands, sweat glands, scent glands, mammary glands, lacrymal glands, ceruminous glands etc.

8. Major functions of integument 3 . Thermal regulation Fur, feathers, scales etc insulate and conserve body heat in cold climate. Sweat glands provide cooling by evaporation. For loss of heat- dermal blood vessels dilate, increase blood flow. Skin becomes radiator of heat and rate of perspiration also increases. For the conservation of heat- dermal blood vessels constrict. 4 . Locomotion  Fin rays of fishes; webs of frogs, turtles, aquatic birds etc. Adhesive pads, claws, digits etc on climbing and feathers of wings, patagia on flying.

9. Major functions of integument 5. Excretion  Excess of water, salts and urea- eliminated in sweat. Gills of marines fishes bear chloride secreting cells. During ecdysis, shedding of skin also gets rid off some metabolic wastes. 6. Storage Stores fat in blubber of whales and seals Fat is stored in subcutaneous fatty layer of the animals prior to hibernation and aestivation. Fat deposit on the hypodermis also helps in insulation and acts as cushion.

10. Major functions of integuments 6. Sensation : skin bears sensory corpuscles sensitive to touch, pain, pressure, temperature, moisture, chemicals etc.  7.Sexual selection : brilliantly coloured feathers, skin, antlers etc lead to sexual dimorphism and serve to attract opposite sex for mating. 8. Synthesis : of Vitamin D in mammals. 9. Cutaneous respiration in amphibians . 10.. Parental care : brood pouches under the skin of some fishes and amphibians protect unhatched eggs .

11. Derivates of integument Epidermal glands, Epidermal scales and scutes , dermal scales and scutes , digital cornifications , horns, feathers and hairs. A . Epidermal glands: Formed from Malpighian layer of epidermis often invade the dermis. They may be unicellular or multicellular; tubular or alveolar in shape and simple or compound (branched). Bear cuboidal or columnar secreting cells. 9 major types- mucous, poison, luminescent, femoral, uropygial, sweat, sebaceous, scent and mammary glands. Derivatives of Integument i )Mucous glands : unicellular (fishes) or multicellular, secrete mucin, forms slimy and sticky mucus when mixed in water. Mucus keeps the skin moist, slippery and protects against the bacteria and fungi. Abundant in fishes and amphibian skin. ii)Poison glands : in many fishes and amphibians, secreting bitter and irritating secretions. Parotoid glands of toad are aggregations of poison glands.

12. Derivates of integument iii) Luminescent glands/photophores : in deep sea luminous bony fishes, some multicellular glands emitting light. Superficial mucous cells form magnifying lens, basal part bears luminescent cells surrounded below by reflecting pigment cells.It serves to attract preys. iv) Femoral glands : Only the skin glands present in some male lizards. Present on ventral surface of thigh secreting sticky substance that serves to hold the female during copulation. Derivatives of Integument V)Uropygial glands : Only the integumentary glands found in birds, present as a prominent swelling just above the tail/uropygium. It is the branched alveolar gland secreting oily substance for lubricating beak, preening feathers and attracting opposite sex. *

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