Its size is determined by its function as a glycogen and fat storage unit, and may change with the seasons as these reserves are built or used up.
ɪts sˈaɪz ɪz dɪtˈɜːmɪnd baɪ ɪts fˈʌŋkʃən æz ɐ ɡlˈaɪkədʒən ænd fˈæt stˈoːɹɪdʒ jˈuːnɪt, ænd mˈeɪ tʃˈeɪndʒ wɪððə sˈiːzənz æz ðiːz ɹɪzˈɜːvz ɑːɹ bˈɪlt ɔːɹ jˈuːzd ˈʌp.