| ZP | zona pellucida |
|---|---|
| ZR | zona reticularis |
| PaO2 | partial oxygen tension in arterial blood; partial pressure of oxygen in arterial blood |
| PH | parathyroid hormone; partial hepatectomy; partial hysterectomy; passive hemagglutination; past histo... |
| PS | pacemaker syndrome; paired stimulation; paradoxical sleep; paraspinal; parasympathetic; Parkinson sy... |