Right Ventricle a muscular chamber that will receive blood from the right atrium and then contract to send it to the lungs to get oxygen. Left Atrium a filling chamber where oxygenated blood from the lungs enters the heart. Left Ventricle the largest mass chamber that receives blood from the left atrium. The muscle is wrapped in connective tissue, which eventually becomes the tendon that attaches to the bone.
Muscle fibers are also highly vascularized and innervated by nerves.
A muscle fiber and a muscle cell are the same thing. Myofibril A muscle fiber is split into functional units called myofibrils. The myofibrils contain filaments with the contractile proteins. The distinction between sarcomeres is made by a z line. The actin and myosin filaments are arranged in sarcomeres, which are THE functional unit of the muscle cell.