Cytokinesis is the physical division of one cell body into two daughter cells. It is distinct from mitosis: mitosis segregates chromosomes into daughter nuclei, while cytokinesis partitions the cytoplasm and plasma membrane.

The two processes are coordinated and often overlap in time, but one can conceptually occur without successful completion of the other.

Animal cells use an actomyosin contractile ring

In many animal cells, signals from the mitotic spindle specify a division plane near the cell equator. Actin filaments and myosin motors assemble into a contractile ring beneath the plasma membrane.

Actomyosin contraction pulls the cell cortex inward, producing a cleavage furrow.

one cell
   ↓ equatorial actomyosin contraction
hourglass-shaped cleavage furrow
   ↓ furrow ingression
narrow intercellular bridge
   ↓ final separation
 two daughter cells

The final membrane-separation event is called abscission.

Plant cells solve a different mechanical problem

Plant cells cannot simply pinch inward through a rigid cell wall. Instead, small membrane-bounded vesicles accumulate between the daughter nuclei and fuse to form a growing cell plate.

The cell plate expands outward until it connects with the existing plasma membrane and cell wall, creating new partitioning material between the daughters.

Thus animal and plant cytokinesis achieve the same topological outcome by different mechanisms:

• animal cells constrict an existing membrane inward;
• plant cells build a new partition outward from the cell center.

Cytokinesis must be positioned relative to chromosome segregation

A misplaced or premature cleavage plane can partition chromosomes incorrectly. Cells therefore coordinate cytokinesis with spindle position and late mitotic events.

The key distinction is:

mitosis      → segregates nuclear genetic material
cytokinesis  → separates the cell body

Successful proliferative cell division normally requires both, but they are different physical problems with different molecular machinery.