3. Skin and related organs

1. 3. Skin and related organs

2. Skin (Integument) A two-part system Figure 5.1

3. Embryologicalorigins: Dermis is mesodermal in orgin. Epidermis isectodermal in orgin.

4. Stratum corneum – dead cells Stratum granulosum – dying cells Stratum basale – reproductive layer against the dermis Hair follicles and other structures are epidermal inclusions In the dermis.

6. Structure of a Nail • The stratum corneum will have varying concentrations of keratin which will determine how scaly the surface is. • Scale like modification of the epidermis on the distal, dorsal surface of fingers and toes Figure 5.4

7. epidermis combines with underlying dermal derivatives and the appendicular skeleton to produce complex structures like horses hooves.

8. Glands of several kinds are also epidermal derivatives • Like hair follicles they are epidermal inclusions in the dermis.

9. All glands are produced by epithelia • Either endoderm or ectoderm • Exocrine glands have ducts that deliver gland products • Endocrine glands are ductless; products are delivered by the blood stream.

10. Amphibian skin has lots of exocrine glands. Granular glands produce toxins. Mucous glands keep skin moist. Why?

11. Melanophores are pigment cells in the dermis that allow the animal to change color.

12. All snakes and most lizards have scales in which the protection is provided by the epidermis (keratin). • Certain lizards and many other groups have added dermal bone below the scales which greatly supplements the protection provided by (keratin).

13. The hardest skin structures are derived from dentine from mesoderm (dermis) and enamel produced by ectoderm (epidermis). • The papilla induces overlying ectoderm to form enamel organ which induces dentine production which provides a site on which enamel is secreted.

14. Two types of structures produced by this interaction are: • Placoid scales (shark) • Teeth • Teeth are very likely derived from placoid scales. • Primitively teeth are homodont and continuously replaced.

15. Bone formation Can occur two ways. • Endochondral • bone Also called cartilage replacement bone. During ossification (=mineralization with CaPO4) a cartilage model is replaced Dermal bone 2) Dermal Bone Think of this as skin bone Forms in the dermis of the skin No cartilage model or precursor

16. Dermal armor. Small amounts of dermal armor can be seen throughout the skin of this monitor lizard. CAT scan

17. Dermal armor in some forms can be extensive. The glass lizard or legless lizard Ophisaurus.

18. Dermal armor also extensive in crocodilians and dinosaurs. Individual units are osteoderms.

19. In armadillos and their extinct relatives the individual osteoderms are joined to form a carapace.

20. One theory is that the dermal part of the shell is fused osteoderms. Dermal bone makes up the majority of the shell in turtles. (Ribs and vertebrae are endochondral bone).

21. The dermatocranium or skull roof probably originated from large osteoderms. Amia, the mudfish or bowfin Buttneria, a Paleozoic amphibian

22. The dermatocranium or skull roof produces bony outgrowths with a variety of funtions • Horns have dermal and epidermal components • antlers have only a dermal component • What might the function be of tubular skull roof bones in hadrosaurs?

23. antlers are replaced annually • horns are permanent structures

24. What are these things? • Horns also occur in reptiles • Why is each species different?

25. What function of the integument is illustrated? Six Anolis lizard species from the Bahamas.

26. 1) Protection Functions of the integument a) physical b) osmoregulatory c) insulation d) infection e) radiation f) crypsis 2) communication 3) Respiration 4) Produce auxiliary structures

27. Necrotizing Fasciitis • Necrotizing Fasciitis is a decaying infection of the fascia. • Caused by Group A Streptococcus & mixed bacteria. • How do you get it? • After surgery, giving birth naturally, a C-section, from a paper cut, scratching a rash, blisters on hands or feet, after a broken arm or leg, rug burn, a friendly punch on the arm, or in some cases, from no trauma at all. • The disease was first described in 5th century B.C. by Greek physician Hippocrates.

28. Pathogenic Nature • Enters through a break in epidermis or dermis. • Reproduces & moves along fascia. The bacteria has proteins that stop phagocytosis of white blood cells. • Bacteria releases exotoxins that clot blood & leads to toxic shock syndrome. • Lack of blood causes organ failure. • Blood clots use a lot of thrombocytes so hemorrhages are common. • Unless treated, death is imminent.

29. Symptoms • Early Symptoms • A minor trauma • Some pain, disproportionate to injury • Dehydration • Flu-like symptoms (weakness, diarrhea, fever, dizziness) • Advanced Symptoms • Swelling of Limb/Area; purplish rash • Dark marks - blisters filled with black fluid • Wound may appear necrotic • Critical Symptoms • Blood Pressure drops severely • Toxic Shock • Unconsciousness

30. Treatment • Immediate aggressive surgical debridement of necrotic skin. • Intravenous antibodies. • Fluid Resuscitation & Nutritional Support. • No way to prevent it. • To Lower the Risks: • Use antibacterial soap, cover mouth when coughing, avoid people with sore throats, wash hands, clean & care for cuts, use sterile wound coverings.

31. References • http://inrmedweb.wfubmc.edu/grand_rounds/1998/necrotizing_fasciitis • http://www.nnff.org/nnff_what.html • http://www.emedicine.com/EMERG/topic332.html • http://www.wrongdiagnosis.com/n/necrotizing_fasciitis/intro.html • http://-cdu.dc.med.unipi.it/Archives/photogallery/NecrotizingFasciitis/index.html • http://www.historique.net/microbe/gas.html