An end effector comprising: a first jaw member having a first tissue contacting surface; a second jaw member having a second tissue contacting surface opposing the first tissue contacting surface of the first jaw member, the first and second jaw members moveable relative to one another between an open position and a clamped position; a knife configured to be movable through the first and second jaw members along a longitudinal axis of the end effector; and a staple cartridge coupled to one of the first or second jaw members for performing a function of firing staples through tissue between the first and second jaw members; a detection assembly disposed within one of the first or second jaw members configured to detect an attribute of tissue clamped between the first and second jaw members, the detection assembly comprising: an ultrasound energy emitter for emitting energy from the one jaw member towards the other jaw member; an ultrasound sensor for sensing a property indicative of the tissue attribute of the tissue clamped between the first and second jaw members, the sensor configured to transmit the sensed property to a processor; and a processor, the processor being configured for receiving a signal from the sensor of the property indicative of the tissue attribute; the processor being configured for determining the tissue attribute from the signal; wherein the processor is configured to compare the calculated tissue attribute to predetermined accepted values; and prevent actuation of the knife when the calculated tissue attribute is not within the predetermined range of acceptable values. a first jaw member having a first tissue contacting surface; a second jaw member having a second tissue contacting surface opposing the first tissue contacting surface of the first jaw member, the first and second jaw members moveable relative to one another between an open position and a clamped position; a knife configured to be movable through the first and second jaw members along a longitudinal axis of the end effector; and a staple cartridge coupled to one of the first or second jaw members for performing a function of firing staples through tissue between the first and second jaw members; a detection assembly disposed within one of the first or second jaw members configured to detect an attribute of tissue clamped between the first and second jaw members, the detection assembly comprising: an ultrasound energy emitter for emitting energy from the one jaw member towards the other jaw member; an ultrasound sensor for sensing a property indicative of the tissue attribute of the tissue clamped between the first and second jaw members, the sensor configured to transmit the sensed property to a processor; and a processor, the processor being configured for receiving a signal from the sensor of the property indicative of the tissue attribute; the processor being configured for determining the tissue attribute from the signal; wherein the processor is configured to compare the calculated tissue attribute to predetermined accepted values; and prevent actuation of the knife when the calculated tissue attribute is not within the predetermined range of acceptable values. an ultrasound energy emitter for emitting energy from the one jaw member towards the other jaw member; an ultrasound sensor for sensing a property indicative of the tissue attribute of the tissue clamped between the first and second jaw members, the sensor configured to transmit the sensed property to a processor; and a processor, the processor being configured for receiving a signal from the sensor of the property indicative of the tissue attribute; the processor being configured for determining the tissue attribute from the signal; wherein the processor is configured to compare the calculated tissue attribute to predetermined accepted values; and prevent actuation of the knife when the calculated tissue attribute is not within the predetermined range of acceptable values.