Functions of Tadarammana and Cuti - The last citta in life

All the time cittas arise and fall away, performing different functions. The last function of citta in life is the function of cuti (dying). When we say in conventional language that a person has died, the cuti-citta (dying- consciousness), which is the last citta of that life, has fallen away. The cuti- citta is succeeded by the patisandhi-citta (rebirth-consciousness) of the following life.
Death is unavoidable. Everybody, no matter whether he is in one of the hell planes, in the human-being plane or in one of the heavenly planes has to  have cuti-citta. We read in the teachings about birth, old age, sickness and death. Old age is mentioned immediately after birth, before sickness is mentioned. The reason is that as soon as we are born, we are already ageing, we are already on our way to death.
We read in the 'Khuddaka Nikāya' ('sutta-Nipāta', 'Woven Cadences’, Ch.lll, The Great Chapter, par. 8, The Dart, vs. 574-583)

How insignificant is man's lot here,

How brief, obscure, how troubled, fraught with ill!

there is no means whereby man shall not die:

Death follows on decay: such is life's course.

The early ripening fruit hazards the fall:

Ever death's hazard haunts the lives of men.

Just as the potter's earthen vessel end

In shards, so too man's life. Young and mature,

The fool and sage, come all within the power 

Of death : death is for all the common lot;

And of death's victims passing to yond world,

No father saves his son, no kith his kin.

See! while they crowd and gaze and weep, their kin

Are one by one, as ox to slaughter, borne.

Thus smitten is the world by old age and death,

The wise world-plight discern, lamenting not. T

hou knowest not the 'whence' or 'whither' way

And, seeing neither course, grievest in vain!