- angioblastic cords - Groups or ‘columns’ of embryonic precursor cells which will form the walls of both arteries and veins.
- aortic arch arteries - (Or pharyngeal arch arteries.) Each early developing pharyngeal arch contains a lateral pair of arteries arising from the aortic sac, above the heart, and running into the dorsal aorta. Later in development these arch arteries are extensively remodelled to form specific components of the vascular system.
- aortic valve - Three-leaflet valve located at the junction between the left ventricle and aortic entrance.
- bulbar ridges - Endocardial cushion tissue located in the bulbus cordis extending into the truncus arteriosus thus forming ridges. These fuse together to form the aorticopulmonary septum.
- bulbus cordis - A region of the early developing heart tube forming the common outflow tract, will differentiate to form three regions of the heart.
- cardiac jelly - Term used in early heart development to describe the initial gelatinous or sponge-like connective tissue separating the myocardium and heart tube endothelium.
- cardiogenic region - The area in the embryo where the precursor cells for heart development lie.
- connective tissue - Fibrous tissue that acts to support body structures or bind other forms of tissue.
- chordae tendineae - Cord-like tendons connecting the papillary muscles to the leaflets of the mitral and tricuspid valves.
- dorsal aortae - Two largest arteries either side of the midline which later fuse to form the descending portion of the aorta.
- endocardial heart tubes - Two tubes formed from the cardiogenic plate in the developing embryo. These form the primordium of the truncus arteriosus, the atrium and the ventricles; later invested with myocardium.
- endocardium - The epithelial membrane lining the inside surface of heart, which along with the endothelial layer forms a continuous lining of the entire cardiovascular system. The endocardium, like the majority of the heart is mesoderm in origin.
- endothelium - A simple squamous epithelium lining blood vessels.
- epicardium - The outer layer of heart tissue.
- fibrous trigone - (trigonum fibrosum) term describing the dense connective tissue between the aortic ring and the atrioventricular ring and has a left and right component. The right fibrous trigone (trigonum fibrosum dextrum) lies between the aortic ring and the right atrioventricular ring. The left fibrous trigone (trigonum fibrosum sinistrum) lies between the aortic ring and the left atrioventricular ring.
- left horn of sinus venosus - The left side of the sinus venosus (initially symmetrical with the right) collecting blood from half of the paired veins: common cardinal veins, umbilical veins and vitelline veins. Later the left horn diminishes and becomes the small coronary sinus.
- mitral valve - (Bicuspid valve) two leaflet valve located on the left side of the heart i.e. between the left atrium and ventricle.
- myocardium - The middle layer of the heart wall composed of cardiac muscle.
- papillary muscles - Small muscles found on the inner myocardium of the left and right ventricles. They are attached to the mitral and tricuspid valves via the chordae tendineae and serve to limit the movements of the valves.
- pericardial coelom - The anatomical body cavity in which the heart lies. The pericardial cavity forms in the lateral plate mesoderm above the buccopharyngeal membrane, as part of the early intraembryonic coelom. This cavity is initially continuous with the two early pleural cavities. Note the single intraembryonic coelom forms all three major body cavities: pericardial cavity, pleural cavity, peritoneal cavity.
- primordial atrium - Common cavity in the upper portion of the developing heart. Later divides to form the left and right atria.
- primordial ventricle - Common cavity in the lower portion of the developing heart. Later divides to form the left and right ventricles.
- pulmonary valve - Three-leaflet valve located at the junction between the right ventricle and the pulmonary trunk.
- right horn of sinus venosus - The right side of the sinus venosus (initially symmetrical with the left) collecting blood from half of the paired veins: common cardinal veins, umbilical veins and vitelline veins. Later the right horn dilates, receiving all the veins, and becomes the sinus venarum of the right atrium.
- semilunar valves - Flaps of endocardium and connective tissue reinforced by fibres which prevent the valves from turning inside out. They are shaped like a half moon, hence the name semilunar. The semilunar valves are located between the aorta and the left ventricle and between the pulmonary artery and the right ventricle.
- sinus venosus - An early developmental cardiovascular structure, thin walled cavity, forming the input to developing heart which has 3 venous inputs (vitelline vein, umbilical vein, common cardinal vein). Later in heart development this structure gets incorporated into the wall of the future right atrium.
- splanchnic mesoderm - Gastrointestinal tract (endoderm) associated mesoderm formed by the separation of the lateral plate mesoderm into two separate components by a cavity, the intraembryonic coelom. Splanchnic mesoderm is the embryonic origin of the gastrointestinal tract connective tissue, smooth muscle, blood vessels and contribute to organ development (pancreas, spleen, liver). The intraembryonic coelom will form the three major body cavities including the space surrounding the gut, the peritoneal cavity. The other half of the lateral plate mesoderm (somatic mesoderm) is associated with the ectoderm of the body wall.
- trabeculae - (trabeculations)Muscular beams located within the ventricles and parts of the atria of the heart.
- tricuspid valve - Three leaflet valve located in the right atrioventricular canal i.e. between the right atrium and ventricle.
- truncus arteriosus - An embryological heart outflow structure, that forms in early cardiac development and will later divides into the pulmonary artery and aorta. Term is also used clinically to describe the malformation of the cardiac outflow pattern, where only one artery arises from the heart and forms the aorta and pulmonary artery.
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