Mini excavators comprise the smallest models available. This category includes: micro excavators that weigh as little as 800 kg or less; mini excavators that average around 3,000 kg; and midi versions that may be upwards of 6 tonnes. Mini excavators are perfect for construction jobs in small spaces and other lighter work.
The inner layer of the pericardium is attached to the heart muscle. A coating of fluid separates the two layers of membrane, letting the heart move as it beats. Your heart has 4 chambers. The upper chambers are called the left and right atria, and the lower chambers are called the left and right ventricles. A wall of muscle called the septum separates the left and right atria and the left and right ventricles.
The Heart. Structure. The heart is divided into four chambers: the right atrium and right ventricle, and the left atrium and left ventricle. The walls of the chambers are made of a special muscle, the myocardium, which contracts rhythmically under the stimulation of electrical currents.