外套膜

軟體動物祖先的假想解剖圖。軟體動物的身體主要可分為头、足、内脏团3個部分，部分生物還具有從外套膜形成的殼[1]。

「外套膜腔」是軟體動物生物學的一個中心特徵，由外套膜的裙邊，即外套膜上一個由其雙重皺摺包裹起來的液體空間融形成。這個空間藏有軟體動物的鳃、肛门、osphradium、腎孔及 生殖孔。

不同物種的外套膜腔會作不同的變化。對於大多數軟體動物來說，牠們的外套膜腔以牠們的呼吸器官運作：特別是在腹足綱的真有肺類物種，外套膜腔更特化成外套膜肺（）；雙殼綱生物整個柔軟生體都在擴大的外套膜腔內[3]，包括其「外殼」，但其外套膜腔的主要功用在進食方面。In some molluscs the mantle cavity is a brood chamber, and in 头足纲 and some bivalves such as scallops, it is a locomotory organ. 在多類物種中，牠們的外套膜的上皮細胞都能分泌出碳酸鈣及貝殼素，並形成軟體動物的外殼。而在海蛞蝓，由於其外殼基本上已退化，其外套膜成為了動物的背部表面。

The mantle is highly muscular. In cephalopods the contraction of the mantle is used to force water through a tubular siphon, the 虹管, and this propels the animal very rapidly through the water. In gastropods it is used as a kind of "foot" for locomotion over the surface. In 歐洲帽貝屬 the foot includes the entire ventral surface of the animal. The foot of the 双壳纲 is a fleshy process adapted by its form to digging rather than to locomotion.

頭足類的神经系统是除了脊椎动物以外的有體腔動物當中最複雜的。頭足類的外套膜有的巨大神經纖維是神經生理学最合適的實驗材料。

In shelled molluscs, the mantle is the organ that forms the shell, and adds to the shell to increase its size and strength as the animal grows. Shell material is secreted by the 外胚层ic (上皮組織) 细胞 of the mantle tissue.[4]

不少腹足綱物種的外套膜都藏在其螺殼裡。以下圖片為一些例子：

• 
  海洋腹足纲物種中华宝螺（Cypraea chinensis）露出其部分延展的外套膜。
• 
  完全展開其外套膜的中华宝螺
• 
  The mantle of the land snail Indrella ampulla is off-white in color and partly visible under the shell. The head and foot are red, and the foot fringe is off-white with narrow black lines.
• 
  The mantle of the nudibranch Felimida purpurea has a marginal line of orange-yellow colour.

In species where the shell is small compared to the size of the body, more of the mantle shows. Shell-less 蛞蝓s have the mantle fully visible. The dorsal surface of the mantle is called the notum, while the ventral surface of the mantle is called the hyponotum. In the family Philomycidae, the mantle covers the whole back side of the body.[5]

• 
  The mantle and the head of this 蛞蝓 Bielzia coerulans is smooth, while the rest of the body is tubercled.
• 
  Megapallifera mutabilis from Philomycidae shows enormously developed mantle

Photo of 驴耳鲍螺 with the shell removed.

This drawing shows that the mantle (in gray) covers the majority of the dorsal surface of the animal.[6]

軟體動物，除了依靠牠們的口蓋之外，還可以透過分泌黏液來防止乾燥和掠食者。

• 外殼 (軟體動物)：由外套膜形成的部分
• 虹吸管：部分軟體動物分類的部分
• 船蛸
• 裸鰓類
• 軟體動物