Stomach

The Twelfth Doctor claimed to know of a race with sixty-four stomachs who talked to each other by disembowelling. (TV: Flatline)

Jocrassa Fel-Fotch Passameer-Day Slitheen, in the skin suit of Joseph Green, blamed his loud farting on a nervous stomach. (TV: Aliens of London)

Two Slitheen-Blathereen were killed when an alarm bell ringing destroyed the Rakweed in their stomachs, causing an explosive build-up of methane gas; Clyde Langer summarised that they had "farted themselves to death." (TV: The Gift)

The Qetesh's stomachs existed out of their bodies. (TV: Goodbye, Sarah Jane Smith)

Gifftans had stomach sacs. (TV: The Tsuranga Conundrum)

Other references

Queen Elizabeth I observed that the Tenth Doctor had a "stomach for war". (TV: The Day of the Doctor)