Tissue thickness compensator comprising layers

A staple cartridge, comprising:

• a cartridge body, comprising:
• a deck comprising a top surface;
• and
• a plurality of staple cavities defined in said deck;
• a plurality of staples removably stored in said staple cavities, wherein each said staple of said plurality of staples comprises a base and legs extending from said base;
• a plurality of staple drivers movable from an unfired position to a fired position during a staple firing stroke to eject said staples from said staple cavities and implant said staples into patient tissue;
• a sled movable from a proximal position to a distal position during said staple firing stroke to move said staple drivers from said unfired position to said fired position;
• and
• a tissue thickness compensator removably attached to said top surface of said deck, wherein said legs move through said tissue thickness compensator as said staples are ejected from said staple cavities, wherein implanting said staples into said patient tissue secures said tissue thickness compensator to said patient tissue, and wherein said tissue thickness compensator comprises:
• a first layer having a first rate of bioabsorption, a first density, and a first uncompressed height, wherein a first portion of each said leg is exposed to said first layer when said staples are ejected from said staple cavities;
• and
• a second layer having a second rate of bioabsorption, a second density, and a second uncompressed height, wherein said second rate of bioabsorption is greater than said first rate of bioabsorption, wherein said first uncompressed height is greater than said second uncompressed height, wherein said second density is greater than said first density such that said first layer is more compressible than said second layer, wherein a second portion of each said leg is exposed to said second layer when said stapes are ejected from said staple cavities, and wherein said first portion is larger than said second portion.

A surgical staple cartridge, comprising:

• a cartridge body, comprising:
• a deck comprising a top surface;
• and
• a plurality of staple cavities defined in said deck;
• a plurality of staples removably stored in said staple cavities, wherein each said staple of said plurality of staples comprises a base and legs extending from said base;
• a plurality of staple drivers movable from an unfired position to a fired position during a staple firing stroke to eject said staples from said staple cavities and implant said staples into patient tissue;
• a sled movable from a proximal position to a distal position during said staple firing stroke to move said staple drivers from said unfired position to said fired position;
• and
• a compressible adjunct removably attached to said top surface of said deck, wherein said legs move through said compressible adjunct as said staples are ejected from said staple cavities, wherein implanting said staples into said patient tissue secures said compressible adjunct to said patient tissue, and wherein said compressible adjunct comprises:
• a first layer having a first rate of bioabsorption, a first density, and a first uncompressed height;
• and
• a second layer having a second rate of bioabsorption, a second density, and a second uncompressed height, wherein said second rate of bioabsorption is greater than said first rate of bioabsorption, wherein said first uncompressed height is greater than said second uncompressed height, wherein said second density is greater than said first density, and wherein a larger portion of each said leg is exposed to said first layer relative to said second layer after said staples are initially implanted into said patient tissue.