Body wall is composed of two layers skin and muscular layer.
Skin
It consists of epidermis and dermis.
Epidermis
The epidermis is composed of a single layer of columnar epithelial cells which are covered by a thin cuticle. Some cells of epidermis are sensory while others are glandular in nature.
Dermis:
The dermis lies below the epidermis and consist of a layer of tough fibrous connective tissues.
Muscular Layer:
The muscular layer forms the greater part of the body wall and consists of metamerically arranged muscle blocks called myomeres. There are nearly 60 myomeres separated from one another by connective tissue partition called mycoma. The myomeres are visible externally as a series of shaped lines around the side of the body. Each myomere is composed of the striated muscle fibers, which are arranged longitudinally along the axis of the body. This kind of arrangement is very useful because:
It provides greater strength and smoothness in action.
The body can be bent rhythmically from side to side and helps in swimming. There is a set of transverse muscles lying in the floor of the arterial cavity which extend across the ventral surface of the anterior two third of the body.
Skin
It consists of epidermis and dermis.
Epidermis
The epidermis is composed of a single layer of columnar epithelial cells which are covered by a thin cuticle. Some cells of epidermis are sensory while others are glandular in nature.
Dermis:
The dermis lies below the epidermis and consist of a layer of tough fibrous connective tissues.
Muscular Layer:
The muscular layer forms the greater part of the body wall and consists of metamerically arranged muscle blocks called myomeres. There are nearly 60 myomeres separated from one another by connective tissue partition called mycoma. The myomeres are visible externally as a series of shaped lines around the side of the body. Each myomere is composed of the striated muscle fibers, which are arranged longitudinally along the axis of the body. This kind of arrangement is very useful because:
It provides greater strength and smoothness in action.
The body can be bent rhythmically from side to side and helps in swimming. There is a set of transverse muscles lying in the floor of the arterial cavity which extend across the ventral surface of the anterior two third of the body.