消化道排出食物残渣

肾脏排出尿液

肺呼出CO2

皮肤分泌汗液

make it

to make it

making

making it

呼吸

排汗

排尿

排便

排便

排尿

呼气

排汗

食物残渣由消化系统排出体外

尿液通过泌尿系统排出体外

二氧化碳由呼吸系统排出体外

汗液由皮肤经汗腺排出体外

出汗

排尿

呼出二氧化碳

排便

Cell communication: each type of specialized cell continually monitors its environment for signals from other cells and adjusts its behavior accordingly; the proliferation and even the survival of most vertebrate cells depends on such social signals. This communication ensures that new cells are produced and survive only when and where they are required.

Selective cell adhesion: because different cell types have different cadherins and other cell adhesion molecules in their plasma membrane, they tend to stick selectively, by homophilic binding, to other cells of the same type. They may also form selective attachments to certain other cell types and to specific extracellular matrix components. The selectivity of these cell adhesions keeps cells in their proper positions.

Cell memory: specialized patterns of gene expression, evoked by signals that acted during embryonic development, are afterward stably maintained, so that cells autonomously preserve their distinctive character and pass it on to their progeny. A fibroblast divides to produce more fibroblasts, an endothelial cell divides to produce more endothelial cells, and so on.

all the above.