1. For the 2-month-old infant:
Injection Site: It should be injected in the Vastus lateralis (lateral thigh).
Muscle Targeted: Vastus lateralis.
Origin: Greater trochanter and linea aspera of the femur.
Insertion: Patella via quadriceps tendon, tibial tuberosity via patellar ligament.
Action: Knee extension.
Location: It is located mid-thigh, outer side between the hip and knee.
For the 65-year-old grandfather:
Injection Site: Deltoid muscle (upper arm).
Muscle Targeted: Deltoid.
Origin: Lateral third of the clavicle, acromion, and scapular spine.
Insertion: Deltoid tuberosity of the humerus.
Action: Arm abduction, flexion, extension, and rotation.
Location: It is located two to three fingers below the acromion process in the upper arm.