1. INTEGUMENTARY SYSTEM Marsh

2. QUICK FACTS:  Largest organ of the body  Complex structure  Functions:  Regulates body temperature  Protects  Makes Vitamin D  Senses the external environment  Skin is the one of the first systems affected when an animal becomes sick

3. SKIN

4.  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

5. SKIN STRUCTURES MADE OF KERATIN Nails 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.

6. 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.

7. 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.

8. SKIN GLANDS

9. GLANDS-ORGANS THAT PRODUCE AND SECRETE FLUIDS  Exocrine Glands-have ducts and are found in the skin  Example: Glands that produce digestive enzymes  Endocrine Glands-ductless and release their hormones directly into the blood stream  Example: pituitary and adrenal glands

10. 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 tail  Produces 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 surface  Contains salt and waste products  Evaporation 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

11. TYPES OF GLANDS  Mammary Gland-  Only present in mammals  Thought to be modified sebaceous glands  Present in both sexes but are rarely seen active in males  They open to the surface in well-developed nipples

12. 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

13. 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 tissue  Adipose tissues acts as an energy store and is a great insulator (especially in mammals with little hair)

14. 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

15. 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

16. 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