What does a mouse’s heart look like? - briefly
A mouse heart is a tiny, elongated organ roughly 8–10 mm in length, comparable in size to a grain of rice, and contains the four chambers typical of mammals. It appears pinkish‑red with a smooth, thin‑walled surface.
What does a mouse’s heart look like? - in detail
A murine heart is a compact, four‑chambered organ roughly the size of a grape. In an adult laboratory mouse, the whole structure measures about 10 mm in length, 6 mm in width, and 5 mm in thickness, with an average mass of 120 mg. The exterior surface is smooth and glistening, covered by a thin pericardial sac that can be lifted easily during dissection.
The organ is divided into right and left atria at the superior aspect, each receiving blood through the superior and inferior vena cava (right) or pulmonary veins (left). Below the atria, the right and left ventricles occupy the majority of the cardiac mass. The right ventricle forms a crescent shape that wraps around the left ventricle, which appears more conical and occupies the left side of the chest cavity. The interventricular septum is thin but distinct, separating the two ventricles.
Three major valves are visible:
- Tricuspid valve at the right atrioventricular junction, composed of three thin leaflets.
- Mitral (bicuspid) valve at the left atrioventricular junction, consisting of two leaflets.
- Semilunar valves (pulmonary and aortic) at the arterial outflows, each with three cusps.
The myocardium is a deep reddish‑brown tissue, denser than skeletal muscle. The ventricular walls are proportionally thicker than the atrial walls; the left ventricular wall measures approximately 1.5 mm, while the right ventricular wall is about 1 mm. The endocardial lining is a smooth, pale layer that lines all chambers and is easily distinguished from the myocardium.
Major vessels emerge from the base of the heart:
- Pulmonary artery and aorta arise from the right and left ventricles, respectively, and are visible as short, thickened trunks.
- Superior and inferior vena cava enter the right atrium, while the pulmonary veins return to the left atrium.
In situ, the heart sits slightly tilted toward the left side of the thoracic cavity, nestled against the sternum and adjacent to the lungs. When removed, the organ retains its structural integrity, allowing clear observation of chamber geometry, valve architecture, and vascular connections without the need for extensive manipulation.