INTEGUMENTARY SYSTEM

Marsh

QUICK FACTS:

Largest organ of the body

Complex structure

Functions:Regulates body temperatureProtectsMakes Vitamin DSenses the external environment

Skin is the one of the first systems affected when an animal becomes sick

SKIN

SKIN

Comes in all kinds of textures and forms

Pigment in the skin can make the outer surface almost any color of the rainbow

Makes up 6-8% of the total body weight

Two layers: Epidermis-

Has no blood or nerves

Cells at the base continually divide and push the cells above them upwards

As cells move up they die and become dry flaky scales that fall off

Die because of keratin (protein)

Keratin makes the skin waterproof

Dermis

SKIN STRUCTURES MADE OF KERATINNails and Claws-used for protection, grasping, grooming and digging. They are continually worn away and grow continuously.

Hoofs-found in ungulate animals. These animals have “lost” toes in evolution and walk on the “nails” of the remaining toes.

SKIN STRUCTURES MADE OF KERATIN CONT.Horns-never branched and once grown are never shed. They are fused with the skull.

Antlers-not formed in the epidermis and do not have keratin. They are shed once a year and are often branched. Velvet forms the bone, while the antlers are growing.

SKIN STRUCTURES MADE OF KERATIN CONT.Hair-acts as an insulator and helps regulate body temperature. Melanin colors the skin and hair.

Feathers-Keratin provides the large airfoils necessary for flapping and gliding flight. The “fluffy” down feathers are great for insulation.

SKIN GLANDS

GLANDS-ORGANS THAT PRODUCE AND SECRETE FLUIDS

Exocrine Glands-have ducts and are found in the skinExample: Glands that produce digestive enzymes

Endocrine Glands-ductless and release their hormones directly into the blood streamExample: pituitary and adrenal glands

TYPES OF GLANDS

Mucus Gland-Slime on the skin of fish and frogs and some can produce poison from modified glands

Preen Gland-Located near the base of the bird’s tailProduces oil to help keep the feathers in good condition

Sebaceous Gland-Secrete an oily secretion into the hair follicle (known as sebum)Keeps the hair supple and prevents the growth of bacteria

Sweat Gland-Consists of coiled tube and duct leading onto the skin surfaceContains salt and waste productsEvaporation of sweat is one of the major mechanisms for cooling the body

Horses can sweat up to 30 litters of fluid a day during exercise

TYPES OF GLANDS

Mammary Gland-Only present in mammalsThought to be modified sebaceous glandsPresent in both sexes but are rarely seen active in malesThey open to the surface in well-developed nipples

SKIN & SUN

Moderate amount of UV is needed for skin to form Vitamin D

Vitamin D prevents bone disorders

Excessive exposure can be damaging to melanin

Melanin helps to protect the underlying layers of the skin from damage

THE DERMIS

Thicker and more uniform in structure than the epidermis

Composed of loose connective tissue with a felted mass of collagen and elastic fibers

This is the part of the skin that becomes commercial leather

Well supplied with blood vessels

In the lower level of the dermis is a layer of fat or adipose tissueAdipose tissues acts as an energy store

and is a great insulator (especially in mammals with little hair)

TEMPERATURE REGULATION

Cold-Blooded (amphibians)-body temperature follows that of the environment

Warm-Blooded (mammals)-body temperature is maintained despite fluctuations in the temperature of the outside environment

Heat is produced by biochemical reactions of the body (especially in the liver) and by muscle contraction

When animals need to reduce heat loss the erector muscles contract causing the hair to rise up and increase the layer of insulating air trapped by them

TEMPERATURE REGULATION CONT. Heat loss from the skin surface can be

reduced by contraction of the blood vessels that lie in the dermis

This takes blood flow to deeper levels, reducing heat loss and causing pale skin

TEMPERATURE REGULATION CONT. To increase heat loss animals:

Expand the blood vessels in the dermis so blood flows near the skin surface and heat loss to the environment can take place

Productoin of sweat. Evaporation of this liquid on the skin surface produces a cooling effect

Hypothalamus-acts like a thermostat Located at the base of the brain

The amount of heat that can be lost from the surface of the body is related to the area of skin an animal has in relation to the total volume of its body

Small animals (mice) have a large skin area compared to their volume, which means they loose large amounts of heat and vice versa for large animals