Snail Skin and Mucas

HURTADO, A., 2008. Making of Super Snail [7 November 2015]. 
Available from: http://www.cgarena.com/freestuff/tutorials/misc/supersnail/index3.html

The part of the snail which can been seen outside the shell consists of its head and foot, with no clear definition between the two parts, so it's often called the head-foot. Snails use the foot to crawl along, which is how most snails move (some water snails have other ways of moving).

The exposed part of the snail is always slimy, as its body surface contains many gland cells which are constantly producing mucus all over the snail's body. The mucus is usually very viscous and is difficult to wash off.  It is made of muco-proteins, which absorb water and swell up like a sponge, rather than dissolving in it. This mucus has various functions:-

-  It helps the snail to attach itself to surfaces, but also protects it as it glides over the ground - a Roman snail can climb over a sharp knife and is protected by its mucus.

-  It keeps the snail hydrated and stops it drying out.

This mucus produces the slime trail left behind by snails.

RODRIGUES, M., 2015. Stock Photography: Snail Skin [7 November 2015]. Available from: 
http://www.dreamstime.com/stock-photography-snail-skin-image20164172

The close-up images of a snail's skin shows that the texture has very small irregular bumps, but the bumps are very smooth looking. The bumps almost look like bubbles, or maybe like the texture of a raspberry or strawberry, without the pips. The skin looks very slimy and wet looking, filling in some of the indentations.

SHEWSBURY, D., 2010. Snail. In: Shewsbury Land. 25 June 2010 [7 November 2015]. Available from: http://shewsburycam.blogspot.co.uk/2010/06/snail.html

The underneath of a snail's foot is very smooth and slimy. It produces mucus to make it easier for the snail to move across the ground and it also stops the snail from getting any injuries from crawling over sharp objects. The snail moves by slowly rippling the foot along the ground to move the body of the snail with it. The move at approximately 1mm/s on land. The underneath of a snail is usually all one colour, with a very even surface.

NORDSIECK, R., 2015. The Living World of Molluscs [7 November 2015]. Available from:
http://www.molluscs.at/gastropoda/terrestrial/helix.html?/gastropoda/terrestrial/helix/morphology.html

A Roman snail, showing the foam snails can produce. They produce watery mucus full of bubbles to stop insects such as ants attacking them, as they get caught in the slime, or if they come in contact with harmful substances, to wash the substance off. 

My Own Photos
I wanted to see what the snail skin and the mucus looked like in person so I went outside and found some of my own snails to take photos of. The photos are shown below. 

Resources:
SHEWSBURYCAM, D., 2010. Snail [7 November 2015]. Available from: http://shewsburycam.blogspot.co.uk/2010/06/snail.html

NORDSIECK, R., 2015. The Locomotion of Gastropods [7 November 2015]. Available from: http://www.molluscs.at/gastropoda/index.html?/gastropoda/morphology/tentacles.html