Thorax Part II
Interior of the chambers of the heart
The right atrium The right atrium has a smooth and a rough part which are separated by a vertical ridge, the crista terminalis, extending between the superior and inferior venae cavae which bring systemic venous blood into the smooth part of the atrium. The coronary sinus opens anterior to the opening of the inferior vena cava. Developmentally the smooth part of the atrium is derived from the sinus venosus of the primitive cardiac tube and the rough part which has muscular ridges known as musculae pectinatae from the primitive atrium. The fossa ovalis, an oval depression on the interatrial wall, is the remnant of the foramen ovale in the fetus. Thorax Part I
THE THORACIC CAGE AND THE INTERCOSTAL SPACE
The bony thoracic cage is formed by the 12 thoracic vertebrae at the back, the sternum in front and 12 pairs of ribs in between. The upper seven pairs of ribs articulate anteriorly direct with the sternum through their respective costal cartilages. The costal cartilage of ribs 8, 9 and 10 articulates with that of the rib above. These ribs with the xiphisternum form the lower costal margin. The lowermost point of the thoracic cage is the tenth costal cartilage. Back and Nervous System
VERTEBRAL COLUMN
Embryology During the fourth week, sclerotome cells migrate medially to surround the spinal cord and notochord. After proliferation of the caudal portion of the sclerotomes, the vertebrae are formed, each consisting of the caudal part of one sclerotome and the cephalic part of the next. The notochord persists in the areas between the vertebral bodies, forming the nucleus pulposus. The latter, together with surrounding circular fibers of the anulus fibrosis, forms the intervertebral disc. |
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