For creatures that seem rather tiny in size, mollusks have a rather large importance in the ecosystem and for humans. Served as food by humans and used as decorations, mollusks have long been a part of society. With their importance in mind, it's critical to know what comprises a mollusk. The four main parts of a mollusk are the head, the foot, the visceral mass and the shell it resides in.
The head contains all of the sensory organs and the brain of the mollusk. Many mollusks also have a radula, a rough tongue that feels like sandpaper used for feeding. The radula is made of chitin, which also happens to be the same material that arthropod exoskeletons are made of. Some also include magnetite, which gives the mollusks better wear traits.
The foot is the muscular part of the body. The foot is used to move around and to dig up food in the dirt for mollusks to eat. The foot causes the body to move by utilizing muscular waves and cilia in combination with mucus.
The visceral mass houses all the primary organs of the body -- the heart, the nervous system and any other internal organs. Mollusks have well-developed organs and have strong respiratory, nervous and circulatory systems, but do not have defined body segments.
The mantle, also known as the pallium, is what secretes the shell. In some mollusks, such as slugs and octopuses, the mantle has no evolutionary value. In other mollusks, the mantle is used for critical activities such as respiration. The shell it creates can be used as protection for the mollusk. Oftentimes when people capture a mollusk, they keep the shell as a piece of art.
- Photo Credit Jupiterimages/Photos.com/Getty Images
How to Take Pulse on Various Parts of the Body
Pulse refers to the rhythmical throbbing of an artery caused by the regular contractions of the heart. It can be felt on...
Parts of Mollusk Shells
Mollusk shells come in a wide variety of shapes and sizes, from the two-sided clam shell, to the swirls of the giant...
General Characteristics of Mollusks
Mollusks are a diverse phylum of invertebrate animals found predominantly in the sea, but with some members having adapted to fresh-water and...
Four Main Parts of a Skeletal System
Although there are four general categories that the bones in the human body fall under, the human skeleton is actually divided into...