Welcome back. Here are the answers to the Skin Quiz-1. In case, if you have come to this article without referring to the earlier one, here is the link to take the quiz - Link No.(1) http://www.suite101.com/article.cfm/our_...
Answers -
| Question No. | Correct Answer | Key words |
| 1 | (d) Vitamin.D | Vitamin synthesized in human skin |
| 2 | (c) ceruminous glands | ear wax producing glands |
| 3 | (d) Stratum lucidum | Epidermal layer with clear waterproof substance |
| 4 | (b) 3 strands | Number of Keratin molecule intertwined strands |
| 5 | (a) Langerhans cells | Skin cells involved in immune functions |
| 6 | (c) hair | Lanugo refers to |
| 7 | (b) tyrosine | Melanin making amino acid |
| 8 | (c) 20 sq.ft. | Skin (adult person) area (in square feet) |
| 9 | (a) ecdysis | Another name for molting |
| 10 | (b) scalp bears hair | Odd set amongst hairless parts |
One of the best studied examples of a freeliving platyhelminth is the planarian. It is as flat and narrow as leaflet of a fern. Take a look at whole body Link No.2- http://www.emporia.edu/biosci/invert/lab... and cross section of a planarian - Link No.3- http://www.emporia.edu/biosci/invert/lab...
The bodywall of planaria is almost transparent. You can see through it the gut of the animal. Please go back to Link No.2 above and convince yourself. The bodywall has two cellular layers - epidermis and the dermis. The epidermal cells are cubelike and their free surfaces bear tiny hairlike cilia.
The entire body may have ciliated epidermis or only the ventral (bellyside) surface. Epidermal gland cells secrete a bed of mucus on the soil. The cilia push onto the ground backwards. This propels the animal forward. So here is an animal in which skin helps in locomotion.
The epidermis rests on a basement membrane like floor-tiles on cement. A very special feature of epidermis in planaria like flatworms is the rhabdites. These are near transparent rodlike structures. Their exact role is not known but it is known that when planaria are stressed they are released out of the planarian skin. It seems they help in forming a protective coat. The muscle layer below the basement membrane can be regarded as the dermis. The myoblasts develop into muscle cells - both outer circular and inner longitudinal muscles. With their muscle fibers the animals crawl. The skin helps in sensory functions too as in the higher animals. It has ability to detect chemicals, light, currents of water, touch and pressure.
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