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Chapter 6 ZOOLOGY 200
THE INTEGUMENTARY SYSTEM Skin and its Derivatives DERMATOLOGY • STUDY OF THE STRUCTURE, COMPOSITION, AND FUNCTIONS OF THE SKIN • DERMA- SKIN • SKIN/INTEGUMENT – the largest organ of the body, approximately 5 kg of the body weight • thick in palms and soles, thin in eyelids and scrotum Functions of Skin • Protects from injuries • Acts as barrier and regulates what enters/leaves body. • Regulates body temperature. • Synthesizes, stores vitamins. • Sensory functions • Excretion • Absorption Main layers of the Skin 1. Epidermis – outermost skin layer 2. Dermis – true skin layer 3. Hypodermis – the subcutaneous layer DIFFERENCES OF THE SKIN LAYERS BASIS 1. LOCATION 2.THICKNESS 3. HISTOLOGICAL COMPONENT 4. VASCULARIZATION 5. LAYERS EPIDERMIS OUTERMOST THIN HIGHLY EPITHELIAL DERMIS SUB EPIDERMAL THICK CONNECTIVE, MUSCULAR,NERVOUS, VASCULAR VASCULAR 2 SUB LAYERS 1.S. PAPILLAROSUM 2.S. RETICULAROSUM HYPODERMIS SUBCUTANEOUS RELATIVE CONNECTIVE

AVASCULAR 5 SUB LAYERS 1.S. CORNEUM 2.S. LUCIDUM 3.S. GRAULOSUM 4. S. SPINOSUM 5. S. GERMINATIVUM ABSENT AGLANDULAR

VASCULAR RELATIVE

6. NERVE ENDINGS 7. GLANDS

PRESENT GLANDULAR – SWEAT,SEBACEOUS, MAMMARY GLANDS

PRESENT GLANDULAR – SECRETES LEPTIN GLAND

8. DERIVATIVES

HAIRS AND NAILS

EPIDERMAL DIFFERENCES I. Epidermis of fishes and Aquatic amphibians • GLANDS 1.MUCOUS GLANDS • secretes gelatinous substance mucin • in frogs: for water absorption and respiration • in fish: defense mechanism for predations 2.SEROUS GLANDS • -secretes poisonous alkaloids for protection against predators. 3.PHOTOPHORES GLANDS • -contains light-emitting substance II. EPIDERMIS OF TERRESRIAL OR LAND VERTERATES • GLANDS 1.MAMMARY GLANDS • secretes milk-feed the young • both sexes: male-non functional, female-functional 2. SWEAT GLANDS / SUDORIFEROUS GLANDS • produce sweat/perspiration cooling mechanism to regulate body temp 3.OIL/ SEBACEOUS GLANDS • secretes oil/sebum for lubrication/make skin moist/shiny 4.UROPYGIAL GLAND [BIRDS] • tail or uropygium • secretes oil for preening 5.SEROUS GLANDS [SNAKE] • secretes poison/toxic alkaloids 6.CERUMINOUS GLANDS [MAN] • -secretes cerumen 7.GLANDS OF ZEIS • -moist the eyelashes 8.MEIBOMIAN GLANDS • -moist the eyelids TYPES OF GLANDS ACCDG. TO MANNER OF SECRETION 1.MEROCRINE GLANDS [TRUE GLAND] • release secretion through memrbrane/cells remain intact. • ex. unicellular integumentary glands, sweat glands 2.HOLOCRINE GLANDS • cells themselves constitute the secretion • cells goes with secretion • ex. sebaceous gland

APOCRINE SWEAT GLAND

3.APOCRINE GLANDS • intermediate in position • secretions gathers at the tip or apical portion of the cell • part of the cyptoplasm are pinched off with the secretion & then repair itself. • ex. mammary glands

EPIDERMAL DERIVATIVES 1.MAMMALS • HAIR-fowicve, bulb, root • NAILS-lunula, nail, bed, root • CLAWS-cats, monkeys, bird, etc, • HOOVES-ungulates • TUSKS-elephants, source of plastics 2.BIRDS BEAKS – preening, nesting, & food acquisition

FEATHERS – insulation, flight, & body contour parts: shaft, barbs, barbules, calamus Types; 1. flight feathers 2. covert feathers 3. pin feathers 4. filoplumers 5. hair feathers

3.REPTILES – epidermal scales - molting – Exoskeleton – turtle scutes -carapace - plastron 4.AMPHIBIAN - rough/coarse skin 5.FISHES –with dermal scales Types of scales 1.CYCLOID SCALES-concentric ridges-milkfish 2.CTENOID SCALES-w/spines or ctenii 3.GANIOD SCALES-rhomboid shape, ganoin sub. 4. PLACOID SCALES-spines directed caudally (sharks & skates) 5. COMOID SCALES-extinct fishes dermal armor COMPARATIVE ANATOMY OF THE SKIN CHORDATE EPIDERMIS DERMIS

1. AGNATHANS

* multi-layered and is rich w/mucous glands * slime eels lack scales * Layers are mitotic including surface cells horny denticles in the buccal funnel is the only cormfied structure,shed replaced * more layered and cells are compactly arranged * unicellular glands excepting chaemiras * stingrays-goblet toxins. * multicellular cells at the base secretes toxins Multicelullar cells are conc. at the base of the claspers of males

* thinner than epidermis but tough due to interwoven collagenous fibers. * rich in the melanophores w/c adheres tightly to the underlying musculator myosepta * thicker than epidermis and w/2 more or less defined layers * placoid scales fr.the paleozioc shakers * sheet of melanophores derse dorsally than virtrally less illumnuscence * with ceratotrichia or fin rays

2.CHONDRICHTHYES

CHORDATE 3. OSTEICHTHYES

EPIDERMIS

DERMIS

-more mucous glands -presence of ancient ganoid or -presence of cycloid scales modern cycloid scale -with uicellular goblet cells w/c -flexible dermal fin rays which maintain mucous coat of the skin to stregthens the fins of bony fishes prevent dessication -with osteoderms -with poisonous granular gland -photophores serve as lures /warning

CHORDATE

EPIDERMIS

DERMIS

4.AMPHIBIA

* skin-w/o scales * with incipient stratum corneum * unicellular goblet cells secretes mucigens for semi-aquatic amphibians * mucous glands-mucin * poison glands-alkaloidal secretion * cornified skin prevents desication.

* with dermal chromatophores * firmly attached to the underlying musculature * voluminous bread subcutaneous lymph sinuses separates skin from muscles * bony dermal scales in caecilians

CHORDATE 5.REPTILES

EPIDERMIS * thick stratum corneum * with epidermal scales molts at regular interval * presence of unique horny surface features * integumentary glands are not abundant * scales, scutes, rattles, plaque, spiny crests

DERMIS * bony dermal bones are more abundant (osteoderms) * lizards - underlying the epidermal scales * Snakes – absent

CHORDATE 6.AVES

EPIDERMIS * thin-skinned * epidermal scales limited to feet and base of breaks * presence of sharp claws * integumentary glands are absent * uropygial gland caudal, oil the feathers * with feathers - down - filoplumes - contour - covert

DERMIS * dermis supports the feathers and arrectures pilorum/ plumarun * exceptionally thin * motility of skin is correlated to thermoregulatory function of feathers * no osteoderms * with spurs both sexes * tarsometatarsus * carpometacarpus in some

CHORDATE 7.MAMMALS

EPIDERMIS * hairs are present arising from hair follicles * epidermal glands - sebaceous-sebum - sudoriferous-sweat - mammary-milk * stratum germinativum is germinating * dense stratum corneum * derivatives - claws - horns - hairs - nails - baleen (whale)

DERMIS * presence of hair follicle, arrector muscles, sweat & sebaceous glands, & conn. tissues * highly vascularized * with nerve endings * has thermoregulatory functionhomiothermic * hypodermis or subcutaneous layer separates skin from muscles * with pigment cells

THE MAMMALIAN SKIN

EPIDERMIS

Stratum Basale • Lowest epidermal layer, near dermis • Good nutrient supply • Reproduces by mitosis • Cuboidal, columnar in shape • Moves to upper epidermis in 27 days. Stratum Spinosum • Living cells • Dividing • 8-10 cells thick • Polygonal in appearance Stratus Granulosum • Poor nutrient supply. • Flatten layer of cells. • 3-5 cells thick. • No cell division. • Keratin accumulates. Stratum Corneum • 25-30 cells thick. • Cells are filled with keratin and hardened. • Sloughed off. • Outer most layer of epidermis. • Keratinocytes Lucidum • Found only in very thick skin. • Translucent. • Highly keratinized. • Dead cells

Melanocyte • Produces melanin for protection from UV radiation. • Responsible for skin color. • Melanoma. DERMIS

Layers of the dermis 1. Stratum papillarosum - superficial region(1/5) of the dermis, consists of areolar connective tissues with elastic fibers - contains dermal papillae that house capillaries, touch corpuscles,& free nerve endings 2. Stratum reticularosum - the deeper portion (4/5 of the dermis) - with dense regular conn. Tissue with bundles of collagen and elastic fibers - spaces between fibers contain adipocytes, hair follicles, nerves, sebaceous glands, sudoriferous glands Comparison of thick and thin skin

DERIVATIVES OF THE EPIDERMIS HAIR (Parts) A. Hair Root/Follicle

B. Hair Shaft

TYPES OF HAIR A. ANGORA B. DEFINITIVE HAIR C. LANUGO 2. NAIL A. NAIL ROOT B. NAIL BED C. LUNULA TYPES OF HAIR

Structure of Nail

DERIVATIVES OF THE DERMIS Sebaceous Gland

Sweat Gland

Types of Sweat Glands (Sudoriferous Glands) • Merocrine glands: release fluid by exocytosis • Eccrine – Most common – Secretion is mostly water with solutes – Cools body down • Apocrine – Develops scent as bacteria metabolize secretion – Stimulated when frightened, during pain, during emotional upset APOCRINE SWEAT GLAND

ECCRINE SWEAT GLAND

Mammary gland

Sensory Structures of Dermis • Deep touch/pressure : • Light touch/pressure : • Warm temperature : • Cold temperature : • Pain :

Pacinian corpuscles Meisner’s corpuscles Free nerve endings Free nerve endings Free nerve endings

Hypodermis (Subcutaneous)

FACTORS INFLUENCING SKIN COLOR 1. GENETIC INFORMATION 2. AMOUNT OF MELANIN PIGMENTS 3. DEGREE OF OXYGENATION 4. HORMONES * MSH 5. EXPOSURE TO SUNLIGHT

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