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. Author manuscript; available in PMC: 2022 Sep 27.
Published in final edited form as: Curr Biol. 2021 Sep 27;31(18):R1098–R1110. doi: 10.1016/j.cub.2021.07.078

Figure 4. Mechanisms used to achieve branching of epithelial tissues.

Figure 4.

(A–D) Examples of branching morphogenesis. Icons of the cellular motifs introduced in Figures 2A and 3A indicate how epithelial branching is achieved at the respective developmental steps. (A) Airway branching in mouse lungs. Schematic of airway bifurcation and domain branching shaped by smooth muscle wrapping in the embryonic mouse lung. (B) Branching in mesenchyme-free cultures. Buckling of the airway epithelium can be studied in 3D culture in Matrigel after removal of the surrounding mesenchyme. (C) Airway branching in the embryonic chicken lung is driven by apical constriction of the epithelial cells. Note the absence of smooth muscle at this stage of development. (D) Branch elongation of mammary organoids. Radial intercalation of luminal cells drives the elongation of mammary organoids in the presence of circumferential tension exerted by the surrounding myoepithelium.