part_of starts_at ends_at glans penis os penis anatomical_structure EMAPA:29769 The os penis (TS:28-28). Bone and cartilage located in the centre of the glans penis, dorsal to the penile urethra. The os penis is ~3.8mm long (although its size is variable) and overlaps the proximal end of the MUMP, located from the MUMP ridge groove to the junction of the glans penis and body of the penis. Comprised of proximal hyaline cartilage of os penis (proximally), which undergoes calcification to form the bone of os penis, distally, at ~6 months age. TS28