Anatomy right The<unk> s are located in the chest on either side of the heart in the rib cage. They are conical in shape with a narrow rounded apex at the top, and a broad concave base that rests on the convex surface of the diaphragm. The apex of the<unk>  extends into the root of the neck, reaching shortly above the level of the sternal end of the first rib. The<unk> s stretch from close to the backbone in the rib cage to the front of the chest and downwards from the lower part of the trachea to the diaphragm. The left<unk>  shares space with the heart, and has an indentation in its border called the cardiac notch of the left<unk>  to accommodate this. The front and outer sides of the<unk> s face the ribs, which make light indentations on their surfaces. The medial surfaces of the<unk> s face towards the centre of the chest, and lie against the heart, great vessels, and the carina where the trachea divides into the two main bronchi. The cardiac impression is an indentation formed on the surfaces of the<unk> s where they rest against the heart. Both<unk> s have a central recession called the hilum, where the blood vessels and airways pass into the<unk> s making up the root of the<unk> . There are also bronchopulmonary lymph nodes on the hilum. The<unk> s are surrounded by the pulmonary pleurae. The pleurae are two serous membranes; the outer parietal pleura lines the inner wall of the rib cage and the inner visceral pleura directly lines the surface of the<unk> s. Between the pleurae is a potential space called the pleural cavity containing a thin layer of lubricating pleural fluid. Lobes + Lobes and bronchopulmonary segments Right<unk>  Left<unk>  Upper * Apical * Posterior * Anterior ;Middle * Lateral * Medial ;Lower * Superior * Medial * Anterior * Lateral * Posterior Upper * Apicoposterior * Anterior Lingula * Superior * Inferior Lower * Superior * Anteriomedial * Lateral * Posterior Each<unk>  is divided into sections called lobes by the infoldings of the visceral pleura as fissures. Lobes are divided into segments, and segments have further divisions as lobules. There are three lobes in the right<unk>  and two lobes in the left<unk> . Fissures The fissures are formed in early prenatal development by invaginations of the visceral pleura that divide the lobar bronchi, and section the<unk> s into lobes that helps in their expansion. The right<unk>  is divided into three lobes by a horizontal fissure, and an oblique fissure. The left<unk>  is divided into two lobes by an oblique fissure which is closely aligned with the oblique fissure in the right<unk> . In the right<unk>  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. 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<unk>  volume reduction procedures. Segments The main or primary bronchi enter the<unk> s at the hilum and initially branch into secondary bronchi also known as lobar bronchi that supply air to each lobe of the<unk> . 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. Segments for the left and right<unk>  are shown in the table. The segmental anatomy is useful clinically for localising disease processes in the<unk> s. A segment is a discrete unit that can be surgically removed without seriously affecting surrounding tissue. Right<unk>  The right<unk>  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. The upper, horizontal fissure, separates the upper from the middle lobe. It begins in the lower oblique fissure near the posterior border of the<unk> , 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. The lower, oblique fissure, separates the lower from the middle and upper lobes and is closely aligned with the oblique fissure in the left<unk> . The mediastinal surface of the right<unk>  is indented by a number of nearby structures. The heart sits in an impression called the cardiac impression. Above the hilum of the<unk>  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<unk>  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. The weight of the right<unk>  varies between individuals, with a standard reference range in men of and in women of . Left<unk>  The left<unk>  is divided into two lobes, an upper and a lower lobe, by the oblique fissure, which extends from the costal to the mediastinal surface of the<unk>  both above and below the hilum. The left<unk> , unlike the right, does not have a middle lobe, though it does have a homologous feature, a projection of the upper lobe termed the lingula. Its name means "little tongue". The lingula on the left<unk>  serves as an anatomic parallel to the middle lobe on the right<unk> , with both areas being predisposed to similar infections and anatomic complications. There are two bronchopulmonary segments of the lingula: superior and inferior. The mediastinal surface of the left<unk>  has a large cardiac impression where the heart sits. This is deeper and larger than that on the right<unk> , at which level the heart projects to the left. On the same surface, immediately above the hilum, is a well-marked curved groove for the aortic arch, and a groove below it for the descending aorta. The left subclavian artery, a branch off the aortic arch, sits in a groove from the arch to near the apex of the<unk> . A shallower groove in front of the artery and near the edge of the<unk> , lodges the left brachiocephalic vein. The esophagus may sit in a wider shallow impression at the base of the<unk> . The weight of the left<unk> , by standard reference range, in men is in women . Illustrations File:CT-Thorax-5.0-B70f-Lungs.Chest CT (axial<unk>  window) File:COR-2-STND-CHEST-LUNGS.Chest CT (coronal<unk>  window) File:CT-Thorax-5.0-B70f.Chest CT (axial<unk>  window) File:COR-2-STND-CHEST.Chest CT (coronal<unk>  window) File:Meet the<unk> s."Meet the<unk> s" from Khan Academy File:MP1 Pulmonology.Pulmonology Video File:Lobes of the<unk>  ogg.mov (1).3D anatomy of the<unk>  lobes and fissures.
Lung
Kidney
Liver
Heart
Brain
Breast
Central nervous system
Peripheral nervous system