Define the following terms:
$(1)$ Sarcomere
$(2)$ Acromion process

(N/A) $(1)$ In a muscle fibre,the region between two consecutive $Z$-lines is termed as a sarcomere. Each sarcomere contains one $A$-band and two half $I$-bands. It is the structural and functional unit of a muscle fibre.
$(2)$ The scapula of the pectoral girdle is a large,flat,triangular bone. The flattened,expanded process present on the spine of the scapula is called the acromion process.