Utilizing bioprinting to engineer spatially organized tissues from the bottom-up

Table 1 Repetitive units in living tissues or organs

Tissues/organs	Repetitive units	Structure	Function	References
Liver	Hepatic lobule	Hexagon or triangle island of hepatocytes interspaced by sinusoids	Metabolism	[16]
Kidney	Nephron	Composed of renal tubule and renal corpuscle, a tuft of capillary surrounded by bowman’s capsule	Filtering blood and regulate body fluid	[17, 18]
Lung	Pulmonary alveolus	Cavities of alveolar membrane surrounded by capillaries	Pulmonary gas exchange	[4]
Bone	Osteon	Cylindrical structures of concentric layers of bone tissues	Stability of bone and facilitating nutrient exchange	[19]
Skeletal muscle	Myofibril	Tubular fiber of long elastic proteins wrapped by sarcoplasmic reticulum	Muscle contraction	[20, 21]
Myocardium	Sarcomere	Aligned fibers between intercalated discs	Muscle contraction	[22]

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