"Abdomen" - what is it, definition of the term
«Abdomen» designates the central cavity of the vertebrate body situated between the thorax and pelvis, enclosing the stomach, intestines, liver, pancreas, spleen, kidneys and associated vascular and nervous structures; it is bounded superiorly by the diaphragm and inferiorly by the pelvic floor, with a muscular wall that supplies support and enables movement.
Detailed information
The abdominal cavity houses major digestive organs, vascular structures, and lymphatic tissue. Muscular layers—external oblique, internal oblique, transversus abdominis, and rectus abdominis—provide protection and support for intra‑abdominal contents. Nerve supply derives from thoracolumbar segments, transmitting sensory and autonomic signals. Blood flow is delivered by the superior and inferior mesenteric arteries and drained by the portal and systemic venous systems.
Parasitic arthropods frequently target this region because skin is thin and richly vascularized. Attachment sites often correspond to areas of reduced hair density, facilitating feeding and oviposition.
- Ticks: employ cheliceral mouthparts to pierce epidermis, insert a hypostome, and secrete anticoagulant saliva. Engorgement may expand the abdomen of the host, causing localized swelling and erythema.
- Bed bugs (Cimex spp.): insert a proboscis into the epidermis, delivering saliva that induces a pruritic wheal. Bites commonly appear on the lower abdomen, especially during nocturnal activity.
- Body lice (Pediculus humanus corporis): lay eggs within clothing seams; nymphs migrate to the abdominal skin to feed, producing excoriated papules and secondary bacterial infection.
- Fleas (Siphonaptera): use spines on the tibiae to grasp hair shafts, then inject saliva containing anticoagulants. Bites concentrate on the pelvic and abdominal area, leading to punctate hemorrhagic lesions.
Clinical manifestations include erythema, edema, and potential secondary infection. Systemic effects arise when vectors transmit pathogens; for example, ticks can transmit Borrelia burgdorferi, while fleas may carry Yersinia pestis. Prompt removal of the arthropod, thorough cleansing of the site, and monitoring for signs of infection constitute standard management.