Most Things Biology

Heart Histology

Despite popular opinion, the heart is not just made of contractile cardiac muscle tissue but contains a fibrous skeleton and nervous tissue.  Disappointingly, it is not shaped like the traditional heart that adorns Cupid’s underwear.  However, the myocardium, made of the contractile cardiac muscle tissue is engorged with blood from coronary vessels and takes up a red color with the traditional H&E stain. 

Fibrous Skeleton & Valves

A close-up image of the atrioventricular (AV) bundle stained with Masson's trichrome, illustrating distinctive lighter-stained Purkinje fibers surrounded by darker myocardial tissue and blue-stained collagen.

AV Bundle Histology

Histological section showing the epicardium as a thin outer layer over the myocardium, with delicate mesothelial cells, and adjacent pericardial fat with large adipocyte spaces.

Endocardium

Microscopic view of cardiac muscle fibers stained with Masson's trichrome, showing elongated, branching fibers in deep red, interspersed with blue connective tissue, alongside centrally located oval nuclei.

Myocardium and Cardiomyocytes

Histological slide of endomysium showing individual muscle fibers surrounded by blue-stained collagen. The purple-stained cells, likely muscle nuclei and fibroblasts, are scattered between the fibers within the connective tissue.

Cardiac Muscle Tissue