Structural Organisation in Animals

The tissue can be defined as group of cells along with intercellular substances performing one or more functions in the body.

Based on structure and shape of cells, animal tissues can be classified into four types: Epithelial Tissue, connective tissue, muscle tissue and neural tissue

The epithelial tissue envelops the external and also the internal surfaces of hollow visceral organs. There are different types of epithelial tissue: simple squammous epithelial, simple cuboidal epithelial, simple columnar epithelium, ciliated epithelium, pseudostratified epithelium, compound epithelium, transitional epithelium and glandular epithelium

The connective tissue connects in all types of connective tissues. Few examples are cell fibres and matrix.
The different types of connective tissue are areolar connective tissue, adipose tissue, white fibrous tissue, bone, cartilage and liquid connective tissue.

The muscle cells are long cylindrical fibres made up of myofibrils. The myofibrils show numerous contractile units known as sarcomeres. The membrane of the muscle is called sarcolemma and the cytoplasm is called sarcoplasm.

There are three types of muscle cells striated muscle, unstriated muscle and cardiac muscle.

The neurons are the structural and functional units of nervous tissue. They show the property of excitability.

The body of Cockroach (Periplaneta americana) is covered by chitinous exoskeleton. Its body is divided into head, thorax and abdomen. The segments bear jointed legs. There are three segments of thorax, each bearing a pair of walking legs. The alimentary canal of cockroach is well developed and consists of mouth, a pharynx, oesophagus, crop, gizzard, midgut, hindgut and anus.

The Cockroach has an open blood-circulatory system where haemolymph fills up the modified body cavity, haemocoel.
The respiratory system consists of networks of tubes called tracheae.

The Cockroaches are unisexual and fertilisation is internal. During copulation, glued mass of sperms called spermatophores are transferred and temporarily stored in spermathecae. Fertilisation occurs in oviduct.

Nervous system of cockroach comprises of a nerve ring with supra oesophageal ganglia which represents the brain. It supplies nerves to antennae and compound eyes. Double ventral solid nerve cord is present. 9 pais of segmental ganglia are present.

Excretory system consists of malpighian tubules, nephrocytes and urecose glands and fat body. Uricotelic malpighian tubules extract the wastes from haemolymph and pour it into hindgut.

Sensory organs of cockroach include pair of antennae, compound eyes, maxillary palps, labial palps and anal cerci.

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