lacunae of morgagni lacunae of morgagni lacunae of morgagni, also called the urethral lacunae of the male urethra (lacunae urethralis, urethrae masculinae or the crypts of morgagni), are small depressions or recesses on the surface of the mucous membrane of the urethra. their openings are usually directed distally. the largest of these recesses is called lacuna magna (or the sinus of guérin, or guérin's sinus), which is situated on the upper surface of the fossa navicularis. lacunae of morgagnidetailsidentifierslatinlacunae urethralesta98a09.4.02.024 a09.2.03.014ta23463fma76588anatomical terminology located deeper within the lacunae are branching mucous tubules called the glands of littre. the lacunae of morgagni are named after italian anatomist giovanni battista morgagni (1682–1771).