"Tissue" - what is it, definition of the term
Cellular material composed of similarly specialized cells organized to perform a common physiological function constitutes the structural and functional unit of multicellular organisms; it forms the body framework of arthropods such as ticks, bugs, lice, and fleas, providing the necessary architecture for growth, protection, and metabolic activity.
Detailed information
The external covering of these ectoparasites consists of a hardened chitinous layer that provides protection and limits water loss. Beneath this shield lies a thin epidermal sheet that secretes the cuticle and supports sensory setae. Muscular fibers attached to the inner surface of the exoskeleton enable locomotion and host attachment.
In ticks, the salivary apparatus occupies a substantial portion of the central body cavity, producing anticoagulant proteins that facilitate blood ingestion. The midgut epithelium contains specialized cells for rapid expansion during feeding and for processing large volumes of host plasma. Reproductive structures include paired ovaries with follicular tissue that mature eggs internally before deposition.
True bugs possess a foregut lined with a muscular membrane that pumps plant or animal fluids toward the digestive region. The filter chamber, composed of densely packed cells, concentrates nutrients while excreting excess water. Sensory organs such as antennae are embedded in a network of nerve tissue that transmits host cues.
Lice display a compact body plan where the ventral surface is covered by a thin, flexible epidermis that allows close adherence to hair shafts. Spiracular openings connect to a network of tracheal tubes lined with respiratory epithelium, delivering oxygen directly to muscular bundles. Ovarian tissue produces eggs that are cemented to host fibers.
Fleas exhibit a segmented exoskeleton with articulated joints surrounded by striated muscle layers that generate powerful jumps. The alimentary canal includes a foregut lined with cuticular cells, a midgut with absorptive epithelium, and a hindgut that reabsorbs water. Reproductive organs consist of paired testes with spermatogenic tissue that continuously produce sperm.
Common structural elements across these arthropods:
- Chitinous exoskeleton with underlying epidermal sheet
- Muscular system attached to the inner cuticle
- Digestive epithelium adapted for rapid nutrient uptake
- Respiratory tubes lined with thin epithelium
- Reproductive organs containing follicular or spermatogenic tissue