Integument: the external covering of an animal.

Protects the animal from: mechanical and chemical injury, and invasion by microorganisms.

Evolutionary Adaptations: regulation of body temperature, excretion of waste materials, vitamin D3 formation via UV radiation, reception of environmental stimuli (pain, temperature, and pressure), locomotion, and movement of nutrients and gas.

Vertebrate integument

Largest organ, why?

Grows with the animal

Epidermis: outer layer of epithelial tissue and is several cells thick.

Dermis: connective tissue beneath the epidermis and is made up of collagenous, reticular, and elastic fibers.

Hypodermis: below the skin and separates the skin from deeper tissues, loose connective tissue, adipose tissue, and nerve endings.

Lampreys and hagfishes

Relatively thick

Many glandular cuticles, but one secretes a protective cuticle.

Hagfishes: slime glands which produce copious amounts of slime that covers the body surface.

Slime functions: protection from parasites and prey capture.

Sharks and Rays

Multilayered and contains mucous and sensory cells.

Dermis: placoid scales called denticles (“little teeth”)

Denticles: contain blood vessels and nerves

Grows with animal

New denticles are produced to maintain enough of these protective layers. Once they reach maturity, they do not grow, but wear down and are lost.

Sandpaper texture

Scales composed of dermal bone and are not shed: grow at the margins and over the lower surface.

Thin layer of dermal tissue, overlaid by the superficial epidermis, typically covers the scales.

Scales have growth rings = used to age fish

Skin is permeable and functions in gas exchange.

Rich with capillary beds to help facilitate respiration.

Epidermis also has mucous glands= prevents bacterial and fungal infections, as well as reducing friction as the fish swims.

Granular glands= secrete an irritating / poisonous –alkaloid

Teleosts: fish that live in the deep sea have photophores /light emitting organs, that facilitate species recognition, act like lures, or send warning signals.

Stratified epidermis and a dermis, containing mucous and serous glands, along with pigmentation cells.

Early amphibians were actually covered in bony scales, and are considered to be transitional species between aquatic and terrestrial vertebrates.

Faced a lot of problems such as desiccation, UV damage, and physical abrasions.

Throughout evolution, amphibians started adapting, and their outer skin layers began developing more keratin (tough, impermeable protein that protects the skin).

Increased keratins also functions in protecting the cells, especially the nucleus from UV light.

The mucous glands help prevent desiccation, aid in gas exchange, and make the body slimy, which is advantageous when trying to escape predators.

Some amphibians have poisonous glands within their dermis.

Poisonous glands produce fluid that can be unpleasant in taste and toxic, which functions as a predator deterrent.

“Warts” of toads are specialized sensory structures.

Stratum corneum= outer layer of the epidermis, it is thick, lacks glands, and is modified into keratinized scales / scutes (thick scales), beaks in turtles, rattles on snakes, and claws, plaques, and spiny crests on others.

Thick, keratinized layer, functions in protection, slows down dehydration, and resists abrasions.

Reptiles, such as snakes and lizards, shed or molt the outer layer of the epidermis, diffusion of fluid between the layers assists in this molting process.

Molting process is also known as ecdysis.

Skin has no respiratory function.

Skin does excrete pheromones that function in sex recognition and defense.

Molting / shedding

No blood supply in the epidermis, therefore the outer epidermal layers lose contact with the blood supply and die.

Lymph moves between the inner and outer epidermal layers loosens the outer epidermis.

Ecdysis typically begins around the head and come off in one piece (snakes and most lizards).

Some shed in little pieces, and the skin simply flakes off.

Dermal in origin

Functions: cryptic coloration, mimicry, and aposematic coloration (warning coloration).

Color and color change can also occur during sexual recognition as well as when the animal is trying to thermoregulate.

Lizards: lack integumentary glands, which make them really dry.

Snakes: large belly scales, which provide contact with the substrate during locomotion.

Show many reptilian features, but lack epidermal glands.

Only have the uropygial or preen gland. This gland functions in oil production and is located in the back, near the base of the tail.

Oil gland is most developed in aquatic species.

Rub their bill over the gland / pore and transfer the oil all over their body and feathers.

May function in improving the health of the feathers, the bill, and the scales of the legs and feet.

Some research suggests that the oil may contain a substance that came from Vitamin D, which came from sunlight.

Thin, typically two or three cell layers thick

Outer layer is very soft

Most prominent feature of the epidermis are the feathers.

Dermis contains lots of blood vessels, lymphatic vessels, nerves, and sensory bodies.

Air pockets in the dermis that aid in thermal regulation.

Lots of dermal smooth muscle fibers that control the positioning of the feathers.

Aquatic birds may have fat deposits in the hypodermal layer, which may store energy and insulate the body.

Most complex of the vertebrate stratum corneum (outer layer of the skin).

Two primary functions:

1. Form the flight surfaces that provide lift and aid steering.

2. Prevent excessive heat loss= allowing the endothermic maintenance of high metabolic rates.

3. Roles in courtship, incubation, and waterproofing.

Two types: pennaceous feathers and plumulaceous feathers.

Pennaceous feathers: flattened and tightly closed to promote aerodynamics. Wings and tails.

Prominent shaft (rachis): barbs branch off

Barbules branch off the barbs and overlap one another.

Hamuli (tiny hooks) interlock with grooves from nearby barbules to keep the feather firm and smooth.

Modified to meet the needs of the bird: Flight feathers: line the tip and trailing edge of the wing and are

asymmetrical

Contour feathers: symmetrical, line the body and cover the base of the flight feathers.

Provide: waterproofing, insulation, and streamlining (allows speed)

Barbs and barbules do not interlock and they give the feather a wispy appearance.

Example down feathers

Down feathers provide insulation and lie below contour feathers.

1. Epidermal cells grow, and form an elongated tube called the feather sheath.

2. Epidermal cells at the base of the sheath grow downward, creating a ringlike follicle that grows into the dermis.

3. Epidermal cells that line the sheath form the barbs of the feather. In pennaceous feathers, the barbs spiral around each other and form the shaft. In plumulaceous feathers, the barbs do not spiral and the shaft forms at the base of the feather.

4. The feather emerges and a tubelike structure called the calamus forms at the base.

Distinguished features:

1. Hair

2. Huge variety of epidermal glands (more than any other vertebrate)

3. Highly stratified, cornified epidermis

4. Dermis that is many times thicker than the epidermis.

Epidermis= stratified squamous epithelium and a variety of cells.

Cell division is quick: deeper cells reproduce and push up towards the surface of the skin.

As the cells move toward the surface they produce a “waterproofing” glycolipid, die, and become keratinized.

Keratinized= protein keratin

Keratin: tough, water resistant protein found in the epidermal cells of mammals, birds, and reptiles; in structures such as hair, nails, feathers, hooves, claws, bills, etc.

Insoluble in water

Prevents dehydration

First line of defense against many toxic substances and microorganisms.

Huge evolutionary adaptation= the ability to prevent dehydration. Allows them to colonize terrestrial environments.

The award goes to the DERMIS!

Made up of:

Blood vessels

Lymphatic vessels

Nerve endings

Hair follicles

Sensory receptors

Small muscles

Glands

Dermis

Under the dermis: this is where you and your pets get many injections (hypodermic needle).

Different from other vertebrates: made up of loose connective tissue, adipose tissue, and skeletal muscles.

Adipose tissue: stores energy in the form of fat and provides insulation.

Skeletal muscle: allows the skin above it to move somewhat independently of underlying tissues.

Skin regulates body temperature by opening and closing pores and releasing sweat / perspiring.

Not all mammals maintain body temperature through sweat glands (controlled by the hypothalamus).

Skins also screens out harmful UV radiation while absorbing some of the beneficial components, which are then converted into Vitamin D3.

Example: humans and horses

Humans have between 2-5 million sweat glands

The ability to sweat allows us to run faster and longer than other mammals.

This adaptation allowed humans to hunt during the hot days while other animals rested and slept, making primates a huge predator.

Some research suggests that this adaptation allowed humans to evolve a bigger, hotter brain.

Horse sweat has a natural detergent called latherin.

Latherin, a protein, actually lathers and functions much like soap, and acts like a surfactant.

Evolutionarily speaking: It is thought that latherin was first found in horse saliva to assist in the breaking down of dry food. As their bodies evolved and became larger, the function moved to their skin as well.

Latherin wets the oily pelt / hairs to facilitate water flow and evaporation.

1. Pooping: large birds such as storks and vultures, defecate on their legs to keep cool. When the fecal matter dries, heat is carried away from the body, and temperature decreases.

2. Mud: pigs, hippos, boars, and buffalo are some “wallowing” examples. Water from the mud evaporates from the animals skin, carrying heat way, and decreasing temperature. Water in mud evaporates a lot slower than clear water, allowing the animal to stay cooler, longer.

3. Ears

Examples: Jack rabbits and elephants

Have a large network of blood vessels in their ears that regulate body temperature.

Too cold: constrict to conserve heat

Too hot: dilate to increase SA:V ratio, allowing more flow

This also helps them conserve water so moisture isn’t lost.

Elephants: also flap their ears like fans as well as spray their ears with water. This can drop their temperature up to 14F.

4. Throat vibrations:

Gular fluttering / vibrating muscles /bones in the throat of birds.

Increases evaporation through membranes in the throat. The more the bird vibrates, the more moist throat membranes are exposed to the air.

Examples: pelicans, owls, herons, doves, quail, nighthawks

https://www.youtube.com/watch?v=Yv2Ir1p_Iuw

5. Estivation

Animals “sleep” through excessively hot temperatures.

By “sleeping,” it allows animals to lower their metabolism so that they don’t need to eat.

Ex- lungfish: lives underground for months during the dry season.

Earthworms are also known to do this.

Survival adaptation.

6. Panting:

Expelling hot air and taking in cooler air.

Cooler air comes in contact with the moist lining of the lungs and throat, which lowers body temperature.

Examples: dogs and some birds

Dogs also use their paws

7. Hiding:

Reptiles

Get out of the sun

Sun increases metabolism

Shade lowers metabolism

Don’t spend a lot of time worrying about temperature, they just don’t eat much = conserving energy.

Susceptible to environmental changes

Suboriferous glands: sweat glands

Sweat is secreted via perspiration

Perspiration is how humans maintain homeostasis through evaporative cooling

Eccrine glands: release watery secretions in evaporative cooling

Appocrine glands: secrete a mixture of salt, urea, and water, which micro-organisms on the skin convert to odorous products.

Sebaceous glands: simple glands connected to hair follicles in the dermis. Lubricate and protect by secreting

sebum.

Sebum: oily, skin softening agent that acts as a barrier for protection. It can also act as a pheromone.

Makes skin and hair wateproof.

Some sweat glands produce pheromones.

Pheromones: chemical that an animal secretes and that communicates with other members of the same species to elicit certain behavioral responses.

Scent or musk glands:

Located around the face, feet, or anus

Secrete pheromones

Function: defense, species recognition, sex, and territorial behavior

Only functional in female mammals

Secrete milk that contains water, carbohydrates, fat, protein, minerals, and antibodies.

May be derived from apocrine glands and usually contain fatty deposits.

Monotremes (egg layers, such as the duck billed platypus and four species of echidna, aka anteaters) have mammary glands but lack nipples. The glands discharge milk into depressions on the belly and the young lap it up.

Other mammals, nipples or teats are suckled for nourishment.

Color is due to pigments or to anatomical structures that absorb or reflect light.

Location: within the cells of the epidermal layer, in hair, or in specialized cells like chromatophores.

Color: Some skin color is due to the color of blood in

superficial blood vessels reflected through the dermis.

Bright colors: venomous, toxic, or bad tasting animals

Camouflage animals

Colors serve as a means of communication, identification among like species, sex, reproductive status, or social rank.

Choose two vertebrates and research how that specific species utilizes its pigmentation.

Describe the evolutionary history as to why this pigment evolved as a beneficial adaptation.

How does the pigment increase the organisms survival?

Research the difference between albinism and leucism. Provide solid examples.

What cool things did you learn?

Composed of keratin and dead cells

Hair shaft: hair that protrudes from the skin

Root: embedded beneath the skin

A coat of hair= pelage, typically consisting of long guard hairs that protect a dense coat of shorter, insulating underhairs.

Hair is mostly dead, therefore molting or shedding has to occur. Fall: many mammals grow a thick coat of insulating underhair,

and the pelage changes color.

Example: Arctic fox: in the fall it takes on a white or cream color, which helps it blend into the snowy environment. In the spring , it molts and its pelage takes on a gray and yellow color.

Arrector pili muscle: smooth muscle, attaches to the connective tissue sheath of a hair follicle surrounding the bulb of the hair root. When the muscle contracts, it pulls the follicle and its hair to an erect position. “Goose bumps” in humans

Other mammals: helps warm them by producing an insulating layer of warm air between the erect hair and skin.

If hair is erect because the animal is afraid, it makes the animal look more intimidating, larger, and less likely to get attacked.

Mechanical displacement of hair stimulates nerve cells associated with the roots.

Guard hairs are sometimes modified into vibrissae, which are thick shafted hairs.

Roots are extremely sensitive and richly innervated (lots of nerve)

Legs

Nose

Mouth

Eyes

Tactile discrimination

Locomotion

Localizing, orientating, tracking

Social behaviors

Deer family: Cervidae

Branched, solid bone

Annual spring growth: develop beneath a highly vascular soft skin= velvet

Males only, except for caribou

Remove velvet just before fall breeding season by rubbing them on a tree

Shed antlers after breeding season, new buds form a few months later

Family Bovidae: sheep, cattle

Hollow sheaths of keratinized epidermis, that attaches to a core of bone arising from the skull.

Don’t shed, not branched, grow continuously, both sexes

Rhinos: hair- like, keratinized filaments that arise from the dermal papulae, are cemented together- not attached to the skull. Horns have pushed them to extinction.

Modifications of the epidermis

Flat, horny plates (fingers and toes in primates)

Claws and hooves

Horns (not to be confused with antler, made of bone)

Baleen plates in whales

1. Which of the following is / are notable features of mammalian skin?

A. the presence of hair

B. a greater variety of epidermal glands than in any other vetebrate class

C. a highly stratified, cornified epithelium

D. A dermis many times thicker than the epidermis

E. All of these are notable features

2. How does the structure of skin relate to its functions of protection, temperature control, waste removal, water conservation, radiation protection, vitamin production, and environmental responsiveness?