Organ Name: Heart (cardio-, cord-, corono-, atrio-)

Where it’s located: Between the right and left lungs, in the middle of the chest, oriented towards the left of the breastbone.

What System: Circulatory System

Main Function: The heart tends to be the same size as a fist, and weighs just under 1 pound, however, it can weigh more depending on how athletic an individual is. It is a hollow muscle enclosed by a two layer sac called the pericardium. The outer layer of the pericardium is made up of tissue and fat, and divided by only a tiny fluid-filled space, there is the inner layer which is attached directly to the heart muscle. There are coronary blood vessels on the outer surface of the heart muscle, under the inner layer of the pericardium, and they supply the heart with oxygen and nutrients. A wall, or septum, is what divides the heart into its two halves, each of which have two chambers called the atrium and ventricle. The right ventricle supplies the lungs with blood through the pulmonary artery, and the left ventricle pumps oxygen-rich blood into the body through the aorta. There are heart valves between the atria and ventricles, which is where blood leaves the heart through the arteries.
The heart muscle inside the peritoneum is made up of cells, known as the heart muscles cells, that contract rhythmically to create pulse. This process is made possible by an electrical system that enables the heart to beat in rhythm, and at the same pace. Each beat is triggered by a group of cells in the wall of the right atrium called the sinus node. Pathways of nerves carry these impulses to the muscle cells in the atria and ventricles and set the pace for the heartbeat.

Protective Bodies: The thoracic cage, or rib cage, protects the heart.

Germ Layer: Mesoderm layer gives rise to the heart.

Major Arteries, Veins, or Nerves: Pulmonary artery, aortic artery, superior vena cava, inferior vena cava, pulmonary veins, carotid artery, subclavian artery, inferior cardiac nerve, middle cardiac nerve, superior cardiac nerve, phrenic nerve, and the vagus nerve.

Diseases:
Congenital Heart Disease: (Or Congenital Heart Defect) are issues with the heart found at birth; defects that can involve the valves inside the heart, the walls of the heart, or the arteries and veins that carry blood through the body. This is the most common birth defect. Complex heart defects can be fatal, but modern medicine have made these more survivable.

Coronary Heart Disease: Plaque buildup inside the coronary arteries, which supply oxygenated blood to the heart muscle. Over time, plaque ruptures, and a blot clot can take its place and completely block any blood flow through the coronary artery. With this block, a heart attack or angina (chest pain) is more likely to occur. Eventually, Coronary Heart Disease can weaken the heart muscle and cause heart failure and/or arrhythmias. Preventable with medicine, diet, and different medical procedures.

Cardiomyopathy: This is a condition where the heart becomes weaker due to becoming enlarged, thick, or rigid. In very infrequent cases muscle tissue can be replaced by scar tissue as the condition worsens. Cardiomyopathy can lead to arrhythmias or heart failure. In the case of heart failure, fluid may begin to build up in the lungs, ankles, feet, or abdomen. It is a disease that can be inherited or acquired; acquired meaning that it has the possibility to develop due to other diseases or conditions. In some cases, if symptoms don’t appear, the patient may need no treatment. In other cases, however, symptoms can be severe, and the condition can act quickly and cause complications.