Integument System PDF

11/18/2024 Integument Integument is the outer covering of the body Performs a great variety of functions and gives rise to such Syste...

11/18/2024 Integument Integument is the outer covering of the body Performs a great variety of functions and gives rise to such System diverse structures as shell, arthropod cuticle, scutes, hair, feathers, and horn The integument of craniates including aquatic and terrestrial forms, conforms to a basic morphologic pattern, consisting of a multilayered epidermis derived from ectoderm and a dermis derived chiefly from mesoderm Functions: protection Functions: exteroceptive ◦ Sensitivity to environment conditions ◦ Dermal armor protects the internal organs from mechanical ◦ Naked nerve endings are stimulated when a foreign object comes in contact with skin = danger alert injury ◦ Glands secrete slimy or noxious substances ◦ Pigments provide protective coloration and a barrier to the rays of sun ◦ Bristling fur or ruffled plumage for ominous appearance, appendages : claws, horns, spiny protuberances and needles.  11/18/2024 Functions: respiration Functions: excretion excretion of metabolic frogs use the skin, wastes (cutaneous which is highly glands) impregnated with Sweat glands for excretion blood vessels, as an of nitrogenous wastes in mammals accessory organ or respiration Fishes diffuses ammonia across the gill epithelium Functions: thermoregulation Functions: Locomotion Keeping the body temperature within the Adhesive pads assist in limits even when climbing, scutes that environmental temperature assist in slithering, varies feathers provide an airfoil for flight, Fur and feathers insulators integumentary webs in against cold, sweat cools digits for locomotion in by evaporation, dilation of sand, mud, or water small blood vessels within and flight (bats) the dermis increases heat loss by radiation  11/18/2024 Functions: nourishment Functions: skin coloration ◦ Teleost hatchlings feed Function in on mucus secreted by concealment, warming the mother’s skin and recognition ◦ Mammary glands for newborn mammals Signal the sex or serve for species identification by other members; serves as alarm General Features of the Integument General Features of EPIDERMIS the Integument DERMIS 1. The outer, thinner but stratified layer of the skin 1. The inner, thicker layer of the skin 2. Consists primarily of cells (cellular) 2. Made up mostly of connective tissue fibers, smooth muscles, blood vessels and sensory nerve endings, 3. Ectodermal in origin especially tactile corpuscles (specialized nerve endings 4. Epidermal derivatives – hair, that respond to tactile, thermal and pain stimuli) nails, claws, scutes, hoofs, beaks and bills, horny scales (reptiles 3. Mesodermal in origin (dermatome, epimere) and birds), feathers, spines, 4. Dermal derivatives of the skin – scales of fishes, enamel of the teeth, glands, antlers (horns of deer) horns (hollow and true horns of ruminants)  11/18/2024 Characteristics of epidermis Characteristics of epidermis Layers of the Epidermis: In thick skin (palms, fingertips, soles of feet) the Stratum lucidum (clear layer): translucent epidermis consists of five layers or strata: (from band just above the S. granulosum. Consists deep to superficial) stratum basale, stratum spinosum, stratum granulosum, stratum of a few rows of flattened dead keratinocytes lucidum, stratum corneum. Thin skin, which with indistinct boundaries. Present only in covers the rest of the body has only 4 layers, thick skin. with the stratum lucidum absent. Stratum granulosum: thin zone consisting of Stratum corneum: outermost layer; a broad 3-5 layers of flattened cells. Keratinization zone 20-30 cell layers thick. Accounts for about begins in this third epidermal layer. The 3/4 of the epidermal thickness. The shingle-like plasma membranes of these cells also thicken dead cells are remnants, completely filled with so that they become more resistant to keratin fibrils, and are referred to as cornified or destruction. Langerhans cells are also found horny cells. Keratin provides a durable in this layer. At the upper border of this layer, abrasion resistant and water-repellent "overcoat" protecting deeper cells from the the cells die and lysosomes begin to digest environment. their organelles. Characteristics of epidermis Epidermis of Fishes and Aquatic Larval Amphibians (Unicellular epidermal glands) Stratum spinosum: contains 5-10 rows of cells fitted closely together. The surface of the cells display minute spiney projections. Mitosis occurs here but not as frequently.  Goblet cells – the most abundant Langerhans cells are scattered among the mucous gland; secrete only mucus keratinocytes. Because cells superficial to this and additional ingredients layer do not receive adequate nutrients, they become less viable and finally begin to die.  Slimy mucus is secreted in quantity in Stratum basale: single layer of cuboidal to response to stressful external stimuli columnar shaped cells. It is separated from the dermis by the basement membrane. Some  Mucus seems to afford some cells move toward the surface while others protection from bacterial infection and migrate into the dermis and gives rise to sweat helps ensure the laminar flow of water and oil glands. Many mitotic cells are seen. across the body surface About 25% of the cells in this layer are melanocytes.  11/18/2024 Epidermis of Adult Amphibians Epidermis of Fishes and Aquatic Larval and Amniotes (Multicellular Amphibians (Unicellular epidermal glands) Epidermal glands)  Mostly multicellular mucous or 2 types glandular glands  Mucus secretions keep the skin 1. Saccular glands moist in air, enabling respiration  Mucus also involved in aquatic  have a saclike secretory portion locomotion; surface coat smoothens the irregularities and  Sac are known as alveoli (are variously rough surface of the epidermis complex expansions of the simple thus reducing friction met by saccular glands of dipnoans and vertebrate swimming through amphibians) viscous water Epidermis of Adult Amphibians and Amniotes (Multicellular Multicellular Epidermal Epidermal glands) glands 2 types 3 Basic Categories of Epidermal Glands 2. Tubular gland 1. Merocrine gland  gland retains its shape as a tube  Uncommon in the skin of non-  Most common variety mammals but are abundant in  Secrete their secretions through the cell mammals membrane, and the cells remain intact  Sweat gland  11/18/2024 Multicellular Epidermal Multicellular Epidermal glands glands 3 Basic Categories of Epidermal Glands 3 Basic Categories of Epidermal Glands 2. Holocrine Glands 3. Apocrine Glands A gland releasing a secretion consisting of disintegrated cells and their secretory products into the lumen  The secretion accumulates in the The secretion of a holocrine gland is made up of apical portion of the cell, which is secretory products formed inside the cell, which then pinched off along with some are released when the plasma membrane ruptures cytoplasm  Mammary gland  Oil gland (birds); Sebacous gland (mammals) Epidermal glands of Terrestrial Photophores Vertebrates Light emitting organs Mucous gland  connective tissue cells which for lubrication make the animal luminous  moisture Upper part: consists of modified mucous cells that serves as Mucous glands on the feet of magnifying lens tree toads and frogs assist in Beneath the lens and other cells is climbing the source of light Swollen mucous glands on the thumb pad of male anurans assist in the restraining the female during mating  11/18/2024 Epidermal glands of Terrestrial Epidermal glands of Vertebrates Terrestrial Vertebrates  Granular gland  Secrete irritating or toxic alkaloids that Avian oil gland are defensive and they ward off  Uropygial gland – a prominent predators swelling at the rump immediately  Source of many pheromones behind the pygostyle (substance that when released into the environment affect the behavior or The secretion is transferred to physiology of other organisms of the feathers during preening same or different species)  Parotoid gland Epidermal glands of Terrestrial Epidermal glands of Terrestrial Vertebrates Vertebrates  Sebaceous gland  Sudoriferous gland or Sweat gland  Alveolar glands with an oily exudate  Coiled tubular gland that extend deep  They are present wherever there are into the dermis of mammals hairs, and the secretion, sebum, is  Secretions ooze onto the surface via usually exuded into the hair follicle  Fur and human hair glisten after tortuous canals that opens as pores brushing because of the oil  The cooling effect of the evaporation  Ceruminous gland – secretes ceruman, of sweat, their predominant with association with hair, traps foreign secretion, is thermoregulatory objects that would go deeper into the ear  In furry mammals, sweat glands are canal confined to the least furry regions;  Meibomian gland – assist on the feet on cats and dogs, lips on rabbits, conjunctiva of the eye snouts of cows and pigs  11/18/2024 Epidermal glands of Epidermal glands of Terrestrial Terrestrial Vertebrates Vertebrates  Scent gland  Mammary gland  Responsible for lactation, or the production  any of various specialized of milk. skin glands, occurring in many  Both males and females have glandular tissue within the breasts; however, in kinds of animals, females the glandular tissue begins to that emit an odor commonly develop after puberty in response to functioning as a social or estrogen release. sexual signal or a defensive  Mammary glands only produce milk after weapon childbirth.  Compound alveolar gland that develop in  Anal glands both sexes from milk lines (a pair of elevated ribbons of ectoderm that extend along the ventrolateral body wall of the fetus from axilla to groin) Formation of the mammary gland Patches of future mammary tissues develop Cont’d: mammary along each milk line They later spread beneath the dermis and a gland nipple forms above Species with smaller litters have fewer As female approach sexual maturity, rising nipples titers of female steroid hormones cause the Humans, monkeys, and apes have one juvenile duct system to spread and branch pair where the nursing baby can be During pregnancy, a battery of hormones protected in the mother’s arm while induces the formation of enormous number of monitoring the environment for enemies alveoli at the ends of the branching duct Cetaceans have a single pair near the system groin, where the baby can hold on and The number and location of mammary nurse while the mother feeds, surfaces, and glands depend on the number of young that dives is typical to the species and on the survival value of one location over another  11/18/2024 Stratum corneum (outermost Keratinization layer of the epidermis) In terrestrial vertebrates, the epidermis Becomes increasingly specialized in covering the body often forms an outer keratinized or cornified layer, the stratum various regions of the body for protection corneum against abrasion, for offense and All cells in the stratum corneum are dead defense, and adjunct to cell During their demise, various protein thermoregulation products accumulate and collectively form Also serves to reduce water loss keratin in a process called keratinization through the skin in dry terrestrial Keratin is a class of proteins produced during keratinization and the main structural environments constituent of hair, feathers, hoofs, claws, Specializations: scales, claws and horny horns, etc protuberances, hairs, and feathers Specialization of SC: Specialization of SC: epidermal scales epidermal scales  Epidermal scales are repetitious  Crocodilians have small, heavily cornified, thickenings of the stratum corneum non-overlapping scales on the limbs and larger, regular thickening on the rest of the that are found only in amniotes body  Squamates (lizards and snakes) – the stratum corneum is disposed on  Scutes – large, thin quadrilateral or overlapping folds of epidermis. polygonal scales  Thinning of stratum corneum at scale Snakes – belly, used for locomotion Turtles – thick scutes on the plastron (for sliding joints permits mobility of skin along the ground); carapace - thinner  11/18/2024 Specialization of SC: epidermal scales Specialization of SC: Claws, hooves, and nails  Birds - epidermal scales develop where there are no  Modification of the stratum corneum feathers: facial area, legs at the end of digits or feet  Armadillos - have hair and  Basic structure: 2 curved parts: scales interspersed over the 1. unguis (horny dorsal plate) entire body, but the scales 2. subunguis (softer ventral plate) confined to the tail and legs  Beaver – epidermal scales  The two plates wrap partially around cover the tail the terminal phalanx (plural: phalanges) Claws Nails Nails are plates of tightly compacted, cornified epithelial cells on the surface of  Claws or talons are curved, laterally fingers and toes compressed keratinized projections from the tips of digits. The nail matrix forms new nail at the nail base by pushing the existing nail forward  They are seen in some amphibians and in most birds, reptiles, and to replace that which is worn or broken at mammals the free edge  Claws evolved into nails in primates Nails protect the tips of digits from and into hoofs in ungulates inadvertent mechanical injury  Birds - claws (often associated only They also help stabilize the skin at the with the feet) borne one or more digits tips of the fingers and toes, so that on the on the wings opposite side the skin can establish a  Ostrich, geese and shifts secure friction grip on objects grasped Only primates have nails  11/18/2024 Hooves Hooves are enlarged keratinized plates on the tips of the ungulate digits The horse hoof consists of the hoof wall, Hooves sole, and the frog Hooves are enlarged keratinized The hoof wall is U-shaped and open at the plates on the tips of the ungulate heel, a derivative of the integument digits The bottom of the hoof, the ground surface, includes the wedge-shaped frog, a mostly The forces from the sole, frog, and keratinized derivative of the integument that digital cushion, and the outward fills the opening in the heel of the hoof movement of the lateral cartilages, The sole fills the ground surface space create a hydraulic component of between the wall and triangular frog. Deep shock absorption to the sole is the fatty digital cushion, or pad, a derivative of the hypodermis Specialization of SC: feathers Development of feather  nonliving cornified products 1. Feather development is initiated of the epidermis that by formation of a dermal conserve body heat, protect papillae against abrasion, smooth contours, and provide 2. Growth of the papilla, and its streamlining inductor effect on the overlying epidermis, resulting to the feather primordium on the  3 morphological varieties surface of the skin Contour feather Down feathers 3. As the feather primordium Hairlike feathers elongates a feather follicle develops  11/18/2024 Development of feather 4. At the base of the feather follicle, a Contour feather Conspicuous feathers that give a bird its mitotically active growth zone contour or general shape proliferates tall columns of Consists of a horny shaft and two flattened epidermal cells that push towards vanes the distal tip of the growing feather The base of the shaft is the calamus (quill) between the dermal papilla and the The vane-bearing segment is the rachis epidermis and a feather sheath Each vane consists of parallel rows of barbs that have barbules and flanges 5. When the feather sheath splits The barbules have hooklets that interlock with open, the fluffy barbs stretch out of the flanges on the next barb, stiffening the vane their cramped quarters Arising from the superior umbilicus (a notch 6. When the feather is full grown the at the base of the rachis of a contour feather), is an after feather dermal papilla in the shift dies and becomes a pulp Filoplumes Down feather  Small, fluffy feathers lying  Hair like feathers underneath and between contour consisting of a shaft and a feathers few barbs and associated  Down feathers lie close to the skin as barbules at the tip thermal insulation  They are associated with  Young birds are covered with down contour feathers and may  Short calamus with a crown of barbs be sensory or decorative in that lack hooklets function  11/18/2024 Additional type Additional type feathers: Bristles feathers: Semiplumes  Bristles – resembles Semiplumes have a developed filoplumes, they are simple central rachis but no hooks on the feathers with stiff rachis but barbules, creating a fluffy they lack any terminal insulating structure barbs Semiplume feathers are a cross Its occurs on the head and between down and contour neck where they screen feathers eyes, ears and nasal Mostly hidden beneath other opening of foreign matter feathers on the body Specialization of SC: hair Hair is a keratinous filament growing out of the epidermis and it is primarily made of dead, Development of the hair keratinized cells 1.The first manifestation of a developing hair The base of a hair is the root is a cylindrical ingrowth of epidermis into Its remaining length constitutes the non living the dermis shaft. 2.Soon thereafter a dermal papilla, The outer surface of the shaft often forms a organizes at the base of the ingrowth, and scaly cuticle. the two become intimately associated Beneath this is the hair cortex, and at its 3.the hair primordium grows deeper and core is the hair medulla deeper into the dermis Inserted on the wall of each hair follicle is a tiny smooth muscle, the arrector pili (is 4.The base of the primordium eventually attached to the follicle and makes the hair becomes bulbous, cornified cells begin to form at that site, and a hair shaft begins to stand erect in response to cold, fear, or anger) rise out of a hair follicle  11/18/2024 Specialization of Fur SC: Hair  A thick covering of hair, fur, or  As humans (and many other mammals) pelage, is generally composed of age their hair becomes gray, no matter guard hairs and underfur what their original youthful color.  The guard hairs, the larger,  This occurs because special stem cells coarse hairs, are the most responsible for hair color within the hair apparent on the outer surface of the fur follicle begin to die.  As an individual grows older, these cells  The underfur is stationed beneath the guard hairs and is die off, eliminating a source of pigments, usually much finer and shorter. and adding no color to the hair shaft, leaving only its intrinsic gray or silver  Both guard hairs and underfur color function largely as insulators Vibrissae Quill Vibrissae, or “whiskers,” are long stiff  Quills or spines are modified hairs hairs growing around the mouth or coated with thick plates of keratin, and elsewhere on the face of many mammals embedded in the skin musculature Vibrissae are considered to mediate a Functionally, most spines serve as tactile sense, complementary to that of defense from predators, but spines skin. are also important tools for This is presumed to be advantageous in communication, shock absorption, particular to animals that cannot always and rain protection rely on sight to navigate or to find food  11/18/2024 Bovine Horns Specialization of SC: Bovine Horns or True horns are Horns found among members of the family Bovidae (e.g., cattle, antelope, sheep,  The term horn means that the surface is goats, bison, wildebeests) composed of keratin.  They consist of a core of dermal bone  Their core, however, is bone, which is of covered by a tough, cornified layer of dermal origin. the integument.  Three varieties of mammalian horns meet  Bovine horns occur in both males and this criterion: females, are retained year-round, and a) Bovine horns continue to grow throughout the life of the individual b) Rhinoceros hair horns c) Horns of pronghorn antelopes  Bovine horns are usually curved or recurved Horns of pronghorn antelopes Rhinoceros Hair Horn  The chief difference between bovine  Rhinoceroses have hair horns horns and pronghorns is that pronghorns  composed of agglutinated keratinized are branched hairlike epidermal fibers that form a solid  The old outer cornified sheath, but not horn perched on a roughened area of the the bony core, is shed annually nasal bone  Horns of the pronghorn, family Antilocapridae, are forked in adult males  The rhinoceros horn does not include a  Female pronghorns also have horns bony core, so it is exclusively a product of whose keratinized sheath is replaced the integument. annually, but these are usually much  It forms from compacted keratinous fibers smaller and only slightly forked  11/18/2024 Specialization of SC: other Specialization of SC: cornified structures Baleen  Rattlesnake rattles are rings of horny stratum corneum that  Broad, thin, horny sheets of oral epithelium remain attached to the tail alter that hang into the oral cavity from the palate each molt  Each sheet is fringed along the edge, and the  Beaks are covered with a horny fringes act like combs or sieves that strain sheath food out of the water passing between them  Roosters' combs are covered with a thick, warty stratum  3 m in height corneum  Baleen is continually being worn away and  Monkeys and apes sit on thick replaced, like hair or fingernails ischial callosities, and camels kneel on knee pads Specialization of SC: other cornified Dermis structures The basic component of dermis is collagenous connective tissue that holds the  Tori are epidermal pads that other components in place and provides most mammals other than tensile strength ungulates walk on Other components includes blood vessels,  At the ends of digits, tori are small nerves, pigment cells, lymphatics, called apical pads naked and encapsulated exteroceptors, and  Corns and calluses are in endotherms, the bases of hairs or feathers temporary thickenings of the and their erector muscles stratum corneum that develop the dermis has on ancient and persistent where the skin has been potential to form bone, these bones are subjected to unusual friction. called dermal bones  11/18/2024 Collagen Fibers the fibrous connective tissue composed mostly of collagen Dermal Bone  Collagen fibers may be woven into distinct layers called plies The bony armor of early fishes was disposed as broad bony plates or smaller  Sharks: the bundles of collagen lie at angles to each bony scales over most of the body, other, giving the skin a bias, the skin stretches when it is immediately beneath the epidermis pulled at an angle oblique to the direction of the bundles The structure of this dermal bone varied in As a result, the skin stretches without wrinkling, water histologic details, but a generalized pattern flows smoothly and without turbulence across the consisted of lamellar bone, spongy bone, surface of the body dentin, and a surface layer of an enamel  Fishes and aquatic vertebrates: collagen fibers of the like substance of one physical nature or dermis are usually arranged in orderly plies that form a another recognizable stratum compactum and they are much Dermal plates and scales are classified as less regularly ordered and usually do not form distinct placoid, rhomboid and elasmoid plies Rhomboid/ Ganoid scale Placoid scales Are usually rhomboid in shape and have articulating peg and socket joints Placoid scales (or denticles) are between them spiny, toothlike projections seen only in cartilaginous fishes Ganoid scales are modified cosmoid scales which consist of a bony basal Consisting of lamellar bone, dentin, layer, dentine, and an outer layer of and an enamel covering ganoine (a form of enamel) Placoid scales are rough to the found in fishes such as touch and the structure they form is the bichirs (Polypteridae), Bowfin nearly impossible to penetrate. (Amia calva), paddlefishes (Polyodontidae), gars (Lepisosteidae), These scales function to protect a and sturgeons (Acipenseridae) fish from predators and can even be Dermal bone forms the foundation of used to injure or kill prey the ganoid scale  Placoid scales become teeth at the Ganoid scales are shiny (because of edge of the jaws the enamel), overlapping, and interlocking  11/18/2024 Elasmoid scales Elasmoid scales  the most prominent dermal  the most prominent dermal armor among living vertebrates armor among living vertebrates  Elasmoid scales lack enamel, dentine, and vascular bone Two subtypes layer. Ctenoid scales - have a comb-like free border;  Their scales are formed of lamellar bone, which is acellular flexible and translucent and noncalcified Cycloid scales - thin and shows concentric lines of Two subtypes growth, without serrations Ctenoid scales - have a on the margin comb-like free border; flexible and translucent  they are overlapping which Cycloid scales - thin and allow for greater flexibility in shows concentric lines of movement growth, without serrations on the margin Antlers Dermal Armor: Shell of Turtles The dorsal half of the shell is the carapace, formed by fusion of dermal bone with expanded ribs and vertebrae  They are not cornified structures but dermal bone attached to the frontal bone Ventrally, the plastron represents  New growing antlers are said to be "in velvet" because they are covered with a soft fused dermal bones along the belly. vascular skin and velvety hair On the surface of both carapace  the overlying living skin (called “velvet”) apparently shapes and provides vascular supply and plastron, keratinized plates of to the growing bone. epidermis cover this underlying bone.  Eventually the velvet falls away to unsheathe the bare bone, the actual material of the finished antlers that is branched  Antlers develop only in males, with the exception of caribou and reindeer  11/18/2024 Giraffe horns Dermal pigments  Chromatophores are cells that contain pigment  The "horns“ (not true granules horns) of giraffes resemble They are found in many locations of the body, but stunted antlers those in the skin are in the dermis and are responsible for skin coloration  They develop from Chromatophores with dispersible granules are separate, cartilaginous responsible for physiologic color changes, which are rapid changes like in chameleons processes that ossify, fuse Four groups of chromatophores are currently to the top of the skull, and recognized: remain covered with living, Melanophore non-cornified skin Iridophore Xanthophore Erythrophore Melanophore Melanophore Melanophore contains the pigment  Hairs receive only melanin granules melanin and hair color attributable to both the specific distribution and density of the  Cellular organelles called granules and to the presence of two melanosomes house these melanin structural forms of melanin granules that intercept sunlight striking the surface of an animal to prevent  Gray or white hair is the result of penetration of harmful radiation. large numbers of air vacuoles and few melanin granules By contributing melanosomes, it adds color to keratinocytes, hair, and  Feathers receive brown, yellow, and feathers red pigments  11/18/2024 Chromatophores  Iridophore, which contains light- reflecting, crystalline guanine platelets and it is found in ectothermic vertebrates and in the iris of the eye of some birds  Xanthophore, containing yellow pigments  Erythrophore, containing red pigments