NEET 2021 Zoology Question 173 Solution

The digestive tract of *Periplaneta americana* is divided into three distinct morphological regions: - Foregut (Stomodaeum): Comprises mouth, pharynx, oesophagus, crop (food storage), and gizzard / proventriculus (cuticular teeth for grinding). - Junction of Foregut and Midgut: Possesses a ring of 6–8 blind tubules termed hepatic or gastric caeca, which secrete digestive juices into the mesenteron. - Midgut (Mesenteron): True secretory and absorptive epithelial stomach. - Junction of Midgut and Hindgut: Possesses a ring of 100–150 yellow-coloured, thin filamentous Malpighian tubules, which perform excretion by extracting uric acid and potassium urate from the haemolymph. - Hindgut (Proctodaeum): Differentiated into ileum, colon, and rectum.

- Option (2): The hypopharynx is a median flexible lobe acting as the tongue, situated within the preoral cavity enclosed by labrum, mandibles, maxillae, and labium (True). - Option (3): In females, the 7th sternum is boat-shaped and, together with the 8th and 9th sterna, forms a female genital pouch (gynatrium) enclosing the gonopore, spermathecal pores, and collateral glands (True). - Option (4): The 10th abdominal segment in both males and females bears a pair of jointed filamentous sensory structures called anal cerci (True; while anal styles are present only on the 9th sternum of males).