CVA Chapter 4 (Integument)

Hypodermis

The deepest layer of the integument. Also a connective tissue layer derived from mesoderm, serves to connect the integument to underlying structures such as muscle.

Dermis

The deepest layer of the skin and middle layer of the integument. It is a connective tissue layer derived from mesoderm.

Exteroception

A variety of integumentary sensory structures allow vertebrates to monitor the external environment. These senses include pain, touch, temperature, and pressure.

Hypodermis Components

Adipocytes for nutrient storage Collagen fibers to anchor the integument to underlying structures Blood vessels Nerves

Afterfeather

Arising from the superior umbilicus, it's a smaller feather arising from the base of the first feather. In emus and cassowaries the afterfeather and main feather are the same size causing them to be called "Double Feather"

Mammals Epidermis

Arranged into layers based on the life stage of the keratinocytes present, 4 layers in thin skin, 5 layers in thick skin.

Apocrine Glands

Associated with Hair Follicles and may release pheromones along with sweat. They are turned on with the onset of puberty.

Inferior Umbilicus

When the feather is full grown the dermal papilla dies. This leaves an opening into the shaft called _____________.

Two Types of Sudoriferous Glands

eccrine and apocrine

Dermal Pipillae

evaginations of the dermis that interdigitate with the abovelying dermis. They will be well vascularized and will induce mitosis in epidermal cells.

Feather Development

Initiated by the formation of the dermal papilla.

Cortex

Middle layer of the hair

Cuticle

Outermost layer of the hair

Maintenance of Homeostasis

1) Chloride secreting glands dump excess chloride in marine reptiles and birds. 2) The epidermis protects from dehydration in terrestrial species. 3) Dermal scales in some fishes serve ass reservoirs for calcium and phosphate. 4) Due to influences of the posterior pituitary the skin of aestivating lungfishes and some toads absorb water from the surrounding mud.

Thermoregulation

1) In endothermic vertebrate species cutaneous appendages such as fur and feathers insulate the body to reduce heat loss. 2) The hypodermis will also aid in insulation (ex; blubber). 3) The integument is well vascularized. a] Through vasodilation and vasoconstriction of cutaneous blood vessels the body can regulate temperature.

Communication

1) It is involved in the production of pheromones for such as dominance, alarms, or sexual cues. 2) Sex-linked skin coloration serves in intraspecific communication.

Keratin production is typically low or nonexistent in aquatic vertebrates.

1) Most fishes synthesize little or no keratin. 2) Some aquatic urodeles, particularly those that venture on to land, have a thin covering of keratinized cells to decrease dehydration. 3) Lampreys possess cornified epidermal spines and "teeth" to aid in feeding.

Nourishment

1) Some animals, such as primates, derive vitamin D from photic stimulation of the skin. 2) All mammal species produce milk from integumentary glands. 3) Some teleosts fishes secrete a nutritive mucus for their young

Epidermis Features

1) composed of tightly packed cells 2) there will be numerous intercellular junctions between these cells 3) avascular 4) highly regenerative

Variations in the Morphological Features of the Integument among the various vertebrates involve:

1) extent of differentiation and specialization of the epidermis 2) relative number and complexity of skin glands 3) extent of bone development in the dermis 4) the nature and presence of the hypodermis

Glands also vary in the manner by which they secrete their products.

1] Merocrine - product is released by typical exocytosis. 2] Apocrine - a portion of the cell is lost when the product is released. 3] Holocrine - the cell is either destroyed with the release of the product or is itself the product.

New Feathers and Old Feathers

1] New feathers are produced by reactivated dermal papillae (which had previously given rise to feathers). 2] Typically old feathers are passively pushed out of follicles by incoming new feathers.

Epidermal Glands Can be Classified on their Duct System

1] They can be Simple, having unbranching ducts. 2] They can be Compound, having branching ducts.

Arrector Plumarum

A bundle of smooth muscle associated with each contour feather follicle. Similar to the mammalian arrector pili muscle, allows a bird to ruffle its feathers.

Antlers

A characteristic feature of the deer family. Composed of dermal bone attached to the frontal bone of the skull, covered by a sheath of vascularized skin called velvet when they are growing. Most species, only males have them, the entire structure is seasonally shed.

Pin Feather

A feather that is still ensheathed by the feather sheath

Respiration

A function of the integument in many amphibian species where the skin supplements the gills/lungs. Some salamanders use only the skin for respiration and lack gills/lungs. The integument in these species will lack keratinization (and obviously scales) and will be thin. Both adaptation will increase the diffusion of gasses across the skin.

Reticular Layer of the Dermis

A much thicker layer composed of dense irregular C.T. that serves to attach the skin to underlying structures.

Superior Umbilicus

A notch at the base of the rachis

Milk Lines

A pair of elevated ribbons of ectoderm extending veterolaterally from axis to groin.

Structures Associated with Each Hair Follicle

A sebaceous gland associated with each follicle, its duct will open up into the hair follicle. An arrector pili will be associated for thermoregulation and threat displays. Each follicle will have a root hair plexus for sensation.

Velvet

A sheath of vascularized skin that covers antlers.

Papillary Layer of the Dermis

A thin superficial layer composed of loose C.T., it serves to nourish the avascular epidermis.

Amphibians Dermis

Although the dermis attaches the skin to underlying muscles, between the dermis and those muscles is a broad sheet of lymph sinuses.

Birds Dermis

Anchors the skin to underlying muscles and supports the feathers. Lacks dermal bone in these animals.

Hair Bulb

At the base of the root the hair expands to give a bulb-like structure called the _______________. Is a site of mitosis and will continually produce new keratinocytes to lengthen the hair and to replace shed hairs. Associated with each hair bulb is a dermal papilla that will be well vascularized.

Hooklets

Barbules have hooklets that will interlock with the flanges of adjacent feathers, stiffening the vane. During preening birds lock hooklets between feathers, this decreases ruffling. Hooklets will be lacking in the barbules of smaller contour feathers.

Avian Oil Glands

Birds have few epidermal glands, oil glands in birds are of limited distribution but they are important for feather maintenance. 1] Uropygial Gland is a large oil gland at the base of the tail. a} Its secretions are distributed to all of the feathers during preening. b} Uropygial glands are largest in aquatic birds. 2] Smaller oil glands line the ear canal and surround the vent in some bird groups.

What does the Dermis contain?

Blood vessels, small nerves, sense receptors, pigment cells, and the base of epidermal evaginations (ex; hair, feathers) as well as their associated structures. The dermis also possesses an ancient and persistent potential to produce bone.

Lipophores

Both xanthophores and erythrophores are known as this because they are soluble in lipid solvents.

Bovine Horns and Pronghorn Horns

Bovine horns are found in the Artiodactyl family Bovidae (ex; true antelopes, cattle, sheep, and goats) and are true horns. 1] Although they are not true antelopes, pronghorns do have true horns. 2] Bovine horns are found in both genders but may show sexual dimorphism. Both bovine and pronghorn horns have a central core of dermal bone covered by a sheath of horn. 1] The horns of pronghorns are branched. 2] Unlike bovine horns, the horny sheath of pronghorn horns are shed annually.

Birds Skin

Can afford to be thinner since feathers do the protective role. Thin everywhere except feet and areas of the head.

Granular Glands

Can secrete a variety of substances in reptiles and some amphibians. They secrete alkaloids that are toxic to deter predators, they can also secrete pheromones. They are not found in all terrestrial vertebrates, they are absent in birds and mammals. They are found in toads where they are abundant but do not show much variation. They are found in reptiles where they are not abundant but do show a great deal of variety.

Chromatophores

Cells containing pigment. Found throughout the body, most of them are located in the dermis except for some mammals.

Sudoriferous Glands

Coiled, tubular glands. Aka Sweat Glands. Allow for thermoregulation, distribution of these glands varies among mammals. Found in the less hirsute (hairy) area of furry species. Humans are the least hirsute and have the most sweat glands. Many mammalian glands are modified sudoriferous glands including ceruminous and mammary glands.

Hair Horns

Composed of agglutinized, keratinized, hair-like epidermal fibers forming a solid "bone" Found in rhinoceros.

Panniculus Adiposus

Composed primarily of adipose and lacks muscle fibers. The primary type of hypodermis in humans.

Iridophores

Contain guanine that is a prismatic substance that reflects or disperses light producing a silvery sheen or an iridescent appearance

Eryhtrophores

Contain red granules

Xanthophores

Contain yellow granules

Panniculus Carnosus

Contains some adipose but most notable has muscle fibers, these muscles are skeletal and function to move the skin.

Feathers

Cornified appendages of the epidermis that evolved from epidermal scales.

Terrestrial Species Epidermis

Covered by keratinized cells

Aquatic Species Epidermis

Covered by mucus type epithelium

The Integument

Covers all surfaces of the body and is directly continuous with the mucus membranes lining all internal passageways that open on to the surface of the body.

Two subtypes of leptoid scales

Ctenoid - comb like free border. Cycloid - rounded free border.

Stratum Basale of Mammal Epidermis

Deepest layer of the epidermis and rests on the basement membrane. Composed of one layer of keratinocytes undergoing mitosis to produce more cells. All of these keratinocytes are in contact with melanocytes that transfer melanin to them.

Denticle Scale

Dentin added to enamel. This term also refers to spikes and projections on a scale.

Amphibians Skin

Differs from that of fish in three major ways: 1) Scales are absent in almost all species. 2) Epidermal glands are, in general, abundant and multicellular. 3) The epidermis has only a slight degree of cornification (except in toads).

Aid In Locomotion

Done through structures such as pads, scutes, claws, feathers, etc.

Root Hair Plexus

Each hair root is associated with a sensory nerve plexus called ____________.

Barbs

Each vane consists of parallel rows of barbs, each barb will have barbules and flanges.

The Bony Dermis of Fish

Early fishes had so much dermal bone they were called "armored fish." The bony armor consisted of huge bone plates and/or smaller bony plates covering most of the body and being located just deep to the epidermis.

Keratinocytes

Epidermal cells that produce keratin.

Birds Epidermis

Epidermal scales are limited to the feet and base of the beak. Beak is covered by a bony sheath. Epidermal glands are limited to a few sebaceous glands lining the outer ear and circling the vent in some species and the uropygial gland.

Hair Shaft

Exposed portion

Pterylae

Feather tracts

Dermal Papillae

Finger-like evaginations of the papillary layer that interdigitate with the epidermis. Serves to anchor the epidermis to the dermis.

Reptiles Skin

First truly terrestrial group to have skin adapted for life on land.

Dermal Scales

Fish have these

Dinosauria

Fossil impression of the skin of several species (ex; hardrosaur, carnotaurus) demonstrated a lumpy roughened appearance with scales. Osteoderms have been found. Some have been identified as belonging to a sauropod group called cetiosaurs. In 2006 in North Dakota a mummified Edmontosaurus was discovered. 1) Its integument was intact and demonstrated a more reptilian than avian pattern. a] The dermis had a very thick reticular layer and was extremely rich in collagen forming a strengthening meshwork. b] The epidermis had epidermal scales of varying sizes. 1] The size variation and patterns were similar to what can be seen in some extant reptiles and may indicate a striped pattern.

Ganoid Rhomboid Scales

Found in Paleozoic Actinopterygians and are still found in modern Chondrosteins (paddlefish) and Neopterygians (gars and bowfins) Only have 3 layers, lamellar bone, dentin, and enamel. They are structurally closer to modern scales than cosmoid scales. The enamel is a special type called Ganoine.

Placoid scales

Found in ancient and modern elasmobranchs. Structurally similar to the primitive condition ganoid scale seen in chondrosteins. Has 3 Layers, Lamellar Bone, Dentin, and Enameloid.

Sebaceous Glands

Found in mammals where integumentary glands reach their highest degree of variety and complexity. They are alveolar glands that secrete sebum, a type of oil. They release their products into ducts that are associated with hair follicles. There are some exceptions, those not associated with the hair follicles open directly onto the surface of the skin in the lips, prepuce, areola, glans penis, and labia minora. These glands are found on all body surfaces except for the soles and palms (frictional surfaces)

Tubular Epidermal Glands

Found only in mammalian skin. However, other types of tubular glands are found throughout the bodies of all vertebrates. (ex. pancreas)

Mammary Glands

Found only in mammals and produce milk to nourish the young. They are compound alveolar glands. They develop in the embryos of both genders as milk lines. Monotremes have mammary glands that are almost like sudoriferous glands, they lack nipples.

Amphibians Epidermis

Glandular, mucus glands are typically multicellular and numerous to keep the skin moist if going on land. Granular glands are common but not as abundant in toads. More terrestrial species will have a layer of cornified cells to reduce dehydration.

Filoplumes

Hair like feathers (peacock). They are innervated with tactile receptors and play a role in touch perception. They are scattered along the skin among the contour feathers.

Mammals Skin

Hair, great variety of epidermal glands, a relatively thick and cornified epidermis.

Reptiles Epidermis

Has a thick, water impermeable stratum corneum. This has many modification such as epdermal scales, scutes, claws, rattles, etc. The glands are almost exclusively granular and restricted to a few localized areas.

Reptiles Dermis

Has small dermal bones (ex; turtle shells) called osteoderms. It is rich in collagen.

Note about Amia, the Bowfins

Have both ganoid scales and the Elasmoid scales of teleosts.

Medulla

Innermost layer of the hair

Feathers Basic Features

Shaft 2 Flattened Vanes

Hair

Keratinized cutaneous appendages, when dense enough they serve to insulate the body and play a role in tactile perception.

Cells of the Deeper Epidermal Layers

Lack keratin and are highly mitotic. Over time these cells are pushed towards the surface of of the epidermis by newly produced cells. As they migrate superficially they accumulate keratin and eventually die.

General Structure of Dermal Bone

Lamellar Bone (cortical or compact bone) deepest layer. Spongy bone (aka cancellous or diploe bone) 2nd deepest layer. Dentin (2nd most superficial layer) Enamel or Enameloid (an enamel like substance) most superficial layer.

Excretion

Many amphibians release carbon dioxide through the skin. This is also true for some species that do not use the skin for respiration. Many fishes release ammonia into the water via the skin and gills. Mammals release some nitrogenous waste into the environment through sweat.

Claws Nails and Hooves

Modifications of the stratum corneum located on the distal aspect of the digits. First appeared in amniotes and are not present in all amniotes. Evolved into hooves in ungulates and into nails in primates.

Epidermal Glands in Aquatic and Semiaquatic Amphibians

Most epidermal glands are multicellular granular glands and multicellular mucus glands. Tailed, semiaquatic amphibians that spend time on land will have the greatest number and broadest distribution of glands. This keeps them moist when exposed to the air which allows it to continue to serve in respiration while on land. Mucus glands in tree frogs and toads hands aid in grasping and holding onto limbs.

The Epidermis in Fishes

Most epidermal glands in fish are unicellular, many are goblet cells that produce mucus. Some are granular cells that also secrete mucus. Few epidermal glands are multicellular, they will often still secrete mucus though. Some produce a thick mucus or alkaloids to protect the organism from predators. Photophores are light emitting multicellular glands found in deep sea teleosts. Photophores are surrounded by blood vessels to nourish them and their associated melanophores (darkly pigmented cells)

Giraffe Horns

Much like stunted antlers. They have a solid core of dermal bone that, in effect, remains ensheathed in velvet throughout their lives. They are never shed, both genders have them.

Rhomboid Scales

Named for their shape, they have a primitive construction having the same four layers as does dermal bone. Two subclasses of this scale: Ganoid and Cosmoid.

Chondrichthyes Epidermis

Nonkeratinized stratified squamous epithelium. Compared to agnathans, this epidermis is thicker and has fewer glands (except in chimera)

Sarcopterygians and Actinopterygians Epidermis

Nonkeratinized stratified squamous epithelium. The glands are unicellular mucus glands that produce a mucus coating, multicellular glands are rare in these fishes.

Eccrine Glands

Not associated with a hair follicle and function only for sweating. Active throughout life

Cosmoid Rhomboid Scales

Not present in extant species, they were present in fishes of the the middle and lower Paleozoic including lobefins. Along with 4 typical dermal bone layers, these scales have Cosmine, a complex canal system associated with the dentin and enamel layers.

Other Cornified Structures

Pangolin Scales are agglutinized, keratinized, hair-like epidermal fibers arranged into overlapping plates. The baleen of toothless whales are thin, broad, horny sheaths of oral epithelium. Baleen is arranged into 100 to 400 sheets and each sheet is fringed by hair, baleen is designed to strain food from water. Corns and calluses on human hands and feet respectively. Ischial callosities in monkeys and apes, Tori, the epidermal pads on the feet of most nonungulate mammals. Tori at the ends of the digits are called apical pads.

Scutes

Polygonal or quadrilateral scales, found on the bellies of snakes where they are used for locomotion.

Hair Root

Portion embedded in the integument

Protection

Primary function of the integument. Keratinization of the epidermis protects from dehydration. It is the first line of defense against pathogens. Dermal armor protects the internal organs. Pigments of the integument provide protective coloration and protection from UV radiation.

Functions of the Integument

Protection Exteroception Respiration Excretion Thermoregulation Nourishment Maintenance of Homeostasis Aid in Locomotion Communication

Cornified Structures in Nonmammalian Tetrapods

Rattles of rattlesnakes Horney sheath of bird bills Comb of a rooster

Horns and Antlers

Refers to the surface being composed of keratinized/cornified. Three varieties of mammalian horns: bovine, hair, and pronghorn horns.

Epidermal Scales

Repetitious thickenings of the epidermis, they occur only in amniotes

Hair Root Sheath

Root surrounded by a sheath of epidermal cells.

Osteoderms

Small dermal plates in tetra pods

Down Feathers

Small fluffy feathers found between contour feathers. Young birds only have these feathers, they have a short calamus and their barbs lack hooklets.

Agnathans Epidermis

Stratified squamous, mucus type epithelium in which all layers are mitotically active and keratinization does not occur. Only the oral denticles are keratinized.

Two Major Types of Mammal Epidermal Glands

Sudoriferous and Sebaceous

Sarcopterygians and Actinopterygians Dermis

The dermis in these fishes contain dermal scales, either ganoid or elasmoid.

Feather Sheath

The epidermal cells of the feather follicle that are now above the epidermal surface

Feather Follicle

The feather primordium will elongate and an epidermally lined it forms along the base of the feather primordium.

Stratum Corneum of Mammal Epidermis

The most superficial layer of the epidermis. This is called the "horny layer" because it is made up by many layers of flattened, dead, keratin rich cells. These cells are being continuously shed and replaced.

Cutaneous Maximus

The muscle of the hypodermis

Platysma

The panniculus carnosus is restricted to the anterior neck in humans, it is called _____________. Our muscles of facial expression evolved from panniculus carnosus as well.

Rachis

The portion that supports the vanes

Hair Follicle

The root and the root sheath together make up this structure.

Epidermis

The superficial most layer of the skin/integument. It is a multilayered epithelium derived from ectoderm.

Stratum Corneum

The superficialmost layer of epidermis, composed of flattened, dead, keratin rich cells. Over time it has developed into scales, claws, and horny projections in reptiles. Gave rise to feathers in birds and hair in mammals.

Mucus Glands

These epidermal glands are absent in most terrestrial vertebrates, they're found in some mammals in a few localized regions of the body to serve in lubrication. The reason they're absent is likely due to cornification of the skin.

Epidermal Glands in Tetrapods

They're based on the shape of their secretory units so either Alveolar (Acinar or Saccular) or they are Tubular. Some glands have secretory units which are a combination of the two called Tubuloacinar or Tubuloalveolar.

Chondrichthyes Dermis

Thicker than that of agnathans, two layered, unique in having placoid scales (Chimera have lost most of their scales) immediately deep to the epidermis is a sheet of melanophores, this sheet is denser dorsally to allow for contralateral shading.

Leptoid Scales

Thin flexible scales composed of a thin layer of lamellar bone on top of a layer of collagen. Covered by a thin layer of epidermis. Found in most teleosts and present in Amia, Latimeria, and the Dipnoans.

Agnathans Dermis

Thinner than the epidermis, only really has a reticular layer, rich in collagen bundles to increase strength, has multiple melanophores.

Stratum Granulosum of Mammal Epidermis

This layer consists of 3-5 layers of flattened keratinocytes beginning to undergo keratinization. The more superficial the layer, the greater the extent of keratinization. The more superficial layers are also too far removed from the underlying dermis to receive nourishment from the blood and so the keratinocytes are dead.

Stratum Lucidum of Mammal Epidermis

This layer is ONLY found in thick skin. A translucent layer of flattened dead keratin rich cells.

Stratum Spinosum of Mammal Epidermis

This layer is named for an artifact, in early slides the cells of this layer had spine-like extensions due to over dehydration of the tissue. This is several cell layers thick. Its keratinocytes are undergoing some mitosis but not to the extent of the stratum basale.

Contour Feathers

Typical flight feathers of birds.

Claw Nails and Hooves Structure

Unguis - outer layer Subunguis - inner (ventral not center) layer Pad - contact area Hoof also has a cuneus, softer than subunguis and located in the U or V shaped portion of the hoof.

Mammals Dermis

Unusually thick due to the presence of many glands, hair follicles, and their supportive structures. It is very well vascularized to allow for thermoregulation.

Calamus or Quill

at the base of the shaft

Melanophores

contain melanin granules which are various shades of brown

Mammal Scales

some mammals have scales, when present they are separate from hairs. (ex tails of beavers and rats) Armadillos have a rare condition where hair and scales interspersed around the body. *Pangolin scales are actually compressed hair*

Vibrissae

specialized hairs used only for sensation

Feather Primordium

the growth of the dermal papilla and its inductive effect will cause the formation of this. A "pimple like" elevation of the skin composed of epidermis and dermis. The amount of vascularization in the dermal papilla will increase so as to be able to nourish the developing feather and to remove metabolic wastes.