biology notes

<<< WHAT IS HEART>>> ★ HEART IS A MUSCULAR ORGAN RESPONSIBLE FOR PUMPING BLOOD THROUGH    BLOOD VESSELS BY REPEATED CONTRACTIONS. CARDIAC; ★ CARDIAC MEANS "RELATED TO HEART"  CARDIAC MUSCLES; ★ THE BULK OF THE WALLS OF HEART IS MADE OF CARDIAC MUSCLES.CARDIAC     MUSCLES ARE INVOLUNTARY IN ACTION AND ARE COMPOSED OF BRANCHED     STRAIGHT CELLS, EACH WITH A SINGLE NUCLEUS. LOCATION OF HEART; ★ IN HUMAN BODY, HEART IS SITUATED BETWEEN LUNGS, IN THE MIDDLE OF CHEST    CAVITY (THORAX) UNDER BREASTBONE. PERICARDIUM PERICARDIAL FLUID; ★ THE HEART IS ENCLOSED IN A DOUBLE MEMBRANOUS SAC-THE PERICARDIAL    CAVITY, WHICH CONTAINS PERICARDIAL FLUID,BETWEEN PERICARDIUM AND    HEART WALLS. FUNCTION OF PERICARDIAL FLUID; ★ IT REDUCES FRICTION BETWEEN PERICARDIUM AND HEART DURING HEART   CONTRACTIONS.  CHAMBERS OF HEART; ★ HUMAN HEART CONSIST OF FOUR CHAMBERS LIKE THE HEART OF BIRD AND  ...