"Intestine" - what is it, definition of the term
The word «Intestine» designates the elongated, muscular conduit of the digestive system that extends from the stomach to the rectum, comprising the small and large sections; its primary functions include the breakdown of ingested material, absorption of nutrients and electrolytes, reclamation of water, and the formation and propulsion of fecal matter toward excretion.
Detailed information
The digestive system of blood‑feeding ectoparasites such as ticks, true bugs, lice and fleas consists of a foregut, a midgut and an hindgut, each specialized for processing ingested blood. The foregut, formed by the pharynx and esophagus, functions as a conduit, delivering the meal to the midgut while preventing premature digestion. The midgut, often referred to as the alimentary canal, contains enzyme‑rich cells that break down proteins, lipids and carbohydrates; it also houses peritrophic membranes that protect epithelial tissue from mechanical damage and pathogen invasion. The hindgut, comprising the ileum and rectum, reabsorbs water and electrolytes, concentrating the remaining waste for excretion.
Key anatomical and physiological characteristics include:
- Peritrophic matrix – a chitinous layer lining the midgut lumen, providing a barrier against microbes and facilitating enzyme diffusion.
- Midgut epithelial cells – equipped with microvilli to increase surface area for nutrient absorption; in many species, these cells secrete anticoagulant and anti‑inflammatory compounds to maintain blood flow.
- Hindgut ion transporters – regulate osmotic balance, allowing rapid dehydration of the blood meal and reducing the parasite’s weight for mobility.
- Symbiotic bacteria – reside within the gut lumen or intracellularly, contributing to synthesis of essential vitamins such as B‑complex nutrients absent in blood.
Physiological adaptations differ among the groups. Ticks possess a highly expandable midgut capable of storing multiple times their unfed body weight, supported by a flexible cuticle. True bugs (e.g., Cimicidae) exhibit a rapid digestion cycle, completing blood processing within hours to minimize exposure to host defenses. Lice maintain a continuous, low‑volume intake, with a short gut length reflecting their small size and obligate ectoparasitic lifestyle. Fleas, adapted for intermittent feeding, have a compact gut that rapidly concentrates blood, enabling swift excretion of excess fluid.
Understanding these digestive mechanisms informs control strategies. Disruption of midgut enzyme activity, interference with peritrophic membrane formation, or targeting symbiotic microbes can impair nutrient acquisition, reducing survival and reproductive capacity of the parasites.