«tasdiqlayman» Tabiiy fanlar fakulteti dekani K. Asqarov

Fissures[edit]
The fissures are formed in early prenatal development by invaginations of the visceral pleura that divide the lobar bronchi, and section the lungs into lobes that helps in their expansion.^[6][7] The right lung is divided into three lobes by a horizontal fissure, and an oblique fissure. The left lung is divided into two lobes by an oblique fissure which is closely aligned with the oblique fissure in the right lung. In the right lung the upper horizontal fissure, separates the upper (superior) lobe from the middle lobe. The lower, oblique fissure separates the lower lobe from the middle and upper lobes.^[1][7]
Variations in the fissures are fairly common being either incompletely formed or present as an extra fissure as in the azygos fissure, or absent. Incomplete fissures are responsible for interlobar collateral ventilation, airflow between lobes which is unwanted in some lung volume reduction procedures.^[6]
Segments[edit]
The main or primary bronchi enter the lungs at the hilum and initially branch into secondary bronchi also known as lobar bronchi that supply air to each lobe of the lung. The lobar bronchi branch into tertiary bronchi also known as segmental bronchi and these supply air to the further divisions of the lobes known as bronchopulmonary segments. Each bronchopulmonary segment has its own (segmental) bronchus and arterial supply.^[8] Segments for the left and right lung are shown in the table.^[5] The segmental anatomy is useful clinically for localising disease processes in the lungs.^[5] A segment is a discrete unit that can be surgically removed without seriously affecting surrounding tissue.^[9]
Right lung[edit]
The right lung has both more lobes and segments than the left. It is divided into three lobes, an upper, middle, and a lower lobe by two fissures, one oblique and one horizontal.^[10] The upper, horizontal fissure, separates the upper from the middle lobe. It begins in the lower oblique fissure near the posterior border of the lung, and, running horizontally forward, cuts the anterior border on a level with the sternal end of the fourth costal cartilage; on the mediastinal surface it may be traced back to the hilum.^[1] The lower, oblique fissure, separates the lower from the middle and upper lobes and is closely aligned with the oblique fissure in the left lung.^[1][7]
The mediastinal surface of the right lung is indented by a number of nearby structures. The heart sits in an impression called the cardiac impression. Above the hilum of the lung is an arched groove for the azygos vein, and above this is a wide groove for the superior vena cava and right brachiocephalic vein; behind this, and close to the top of the lung is a groove for the brachiocephalic artery. There is a groove for the esophagus behind the hilum and the pulmonary ligament, and near the lower part of the esophageal groove is a deeper groove for the inferior vena cava before it enters the heart.^[3]
The weight of the right lung varies between individuals, with a standard reference range in men of 155–720 g (0.342–1.587 lb)^[11] and in women of 100–590 g (0.22–1.30 lb).^[12]