That is part of the pectoralis major.
Chest
The following muscles are used: Chest (upper chest specifically) Triceps Shoulders
It is called orbicularis orus. Yes, it is a sphincter muscle.
The four main intramuscular injection muscles are the deltoid muscle, vastus lateralis muscle, ventrogluteal muscle, and dorsogluteal muscle. While the deltoid muscle site is the upper arm region, the vastus lateralis muscle site is on the thigh. The ventrogluteal muscle is the hip, and the dorsogluteal muscle is situated on the buttock area.
The main symptom of angina pectoris is sharp pain on the left side of the chest that may radiate throughout the upper body.
Lungs
A spurt muscle is one that has an attachment, called the insertion, close to a joint. This allows them to be the main movers, usually referred to as prime movers. An example of a spurt muscle is the biceps in your upper arm, also called the bicep brachii.
The main muscles used are biceps, rear delts, and upper back. With the dip you ad triceps and chest. Of course all the other muscles that involve griping the bar or rings, and the kipping motion using core muscles.
The bench press is a compound exercise that is performed with a barbell or dumbells and weight bench. During this exercise, you lift the weight to and from the chest from a face-up position. Being that this is a compound exercise, it works multiple muscle groups at once.Pectoral MusclesThe anatomical name for the chest muscles is the pectorals. The pectoralis major is the part of the chest that gets activated when you are pushing the bar straight up. The pectoralis minor gets recruited when your shoulders shrug forward. Of the two muscle parts, the main emphasis is placed on the pectoralis major. By changing the angle of your bench press to a declined or inclined position, you would place more emphasis on the lower chest and upper chest respectivelyBy Adewunmi Adejumo
the chest is made out of 4 main muscles, to get a square chest you simply must build all four muscles the two main are the upper and lower pectorial if you only work on the lower pecs you will end up with round shaped chest, most people say its genetics but don't have a clue what there going on about, you simply have to build all 4 chest muscles to get the natural square shape underneath. for the upper chest you must do more incline press, for the lower try simple bench press or press ups. LJ
While one muscle contracts, the other muscle in the pair returns to its original length. The main muscle that bends your upper arm is called the Biceps brachii. The action is called flexion at the elbow. This muscle is on the "front" of the arm. The muscle that acts against this one is called the Triceps brachii. Its' action is extension at the elbow. This muscle is on the "back" of the arm. See the link below:
The main purpose of the trapezius muscle if to stabilize the shoulder blade (scapula); provide a base for the movements of the arm, and to create the shoulder girdle for stability to the upper body.