We're talking about the pectoralis major and the pectoralis minor, commonly called the pecs.
From the smh.com.au
The smaller pectoralis minor lies beneath the pec major and connects on top of the shoulder blade.
From the smh.com.au
Early effectiveness of isolated pectoralis minor tenotomy in selected patients with neurogenic thoracic outlet syndrome.
From the sciencedaily.com
Pectoralis minor is largely responsible for the great upper-body development of many competitive freestyle swimmers.
From the smh.com.au
When symptoms occurred exclusively under the collarbone, patients only received detachment of the pectoralis minor tendon as a minimally invasive procedure.