Association of various bodily organs to Lord Shivas AsthaMurty form (8 forms) are mentioned in YajurVeda. Here is passage from YajurVeda Taittariya Samhita 1.4.36:
चित्तम् संतानेन भवं यक्ना रुद्र तनिम्ना पशुपतिम् स्थूलहृदयेनाग्नीम् हृदयन रुद्रं लोहितेन शर्वम् मतस्नाभ्याम् महादेवम् अन्तःपार्श्वेनौषिष्ठहनम् शिंगीनिकोश्याभ्याम् ।। (Yajurveda 1.4.36)
Chitta with the sinew, Bhava with the liver, Rudra with the taniman, Pashupati with the thick heart, Agni with the heart, Rudra with the blood, Sarva with the kidneys, Mahadeva with the intestinal flesh, him that slayest most quickly with the entrails.
Are these parts associated with offerings of animal organs of the sacrificed animals of Yajna? Or it is about association with living organs like, Bhava is associated with liver, Pashupati with thick heart etc.. etc...?
If it is about offering of animal parts from Vedic Yajna, then in which Yajnas are these parts offered?
As a sidenote I guess that these are offered also in Ashwamedha Yajna, because as discussed in answer here, Ramayana states 'Ashwamedha Yajna is the highest worship of Rudra.'