For example - if a user selects the value 2 from the picklist, an additional field will display that needs to be filled in. If a user selects the value 3 from the picklist, an additional two fields will display that need to be filled in.
Danielle Dean One workaround is you create few page layouts say for example you create multiple page layouts one with the 2 fields which you mentioned when the kidney has two arteries. similarly, a page layout with 3 fields when the kidney has three arteries. now you associate it with record types. by default, you don't show these fields on the master/default record type but once a record is created you can use workflow field update and update the record type based on picklist value so if the value is 2 you select record type having page layout with 2 fields. with this, you will not see many fields on the page layout but only required fields only if he selects 3 then the corresponding 3 fields page layout will be set by workflow update. this workaround requires multiple page layouts and record types.