This document discusses the anatomy of the thorax, specifically the lungs and their lobes and segments. It states that each lung is divided into lobes by fissures, with the right lung having 3 lobes and the left having 2. Each lobe further divides into segments, with the right lung having 10 segments total and the left having around 8-9 segments. It then proceeds to describe the specific lobes and segments of each lung in detail, highlighting their locations, boundaries, and vascular supply. In summary, it provides an overview of the gross anatomical structure and subdivisions of the lungs.

1. ANATOMY OF THORAX
KELVIN JOSE
B.Sc MIT 2ND YEAR

2. LUNG
The lungs lie in the thoracic cavity,
separated by the heart and mediastinum.
While the two lungs are similar, they are
not completely symmetrical, having a
different number of lobes and a different
bronchial and vascular anatomy. In most
individuals, the right lung is composed of
three lobes subdivided into 10 segments
and the left is composed of two lobes and
eight segments. They are surrounded by
the pleura which separates them from the
chest wall.

3. LOBES OF LUNG
The right lung consists of three lobes
the superior, middle, and
inferior lobes. The left lung consists
of two lobes the superior and
inferior lobes. A bronchopulmonary
segment is a division of a lobe, and
each lobe houses multiple
bronchopulmonary segments.

4. LUNG FISSURES
 Lung fissures are a double-fold of
visceral pleura that either
completely or incompletely
invaginate lung parenchyma to
form the lung lobes.
 Each lung has an oblique fissure
separating the upper lobes from
the lower lobes and the right lung
has a horizontal fissure that
separates the right upper lobe
from the middle lobe.

5. LUNG SEGMENTS
 The lungs can be further
subdivided into
bronchopulmonary segments.
There are ten such segments
located within the right lung, and
roughly 8 – 9 on the left side as
some of the segments may fuse
together. Each bronchopulmonary
segment is served by
corresponding branches of the
bronchial tree, along with their
own arterial supply.

6. RIGHT BRONCHOPULMONARY SEGMENTS
 The superior lobe of the right lung has
three bronchopulmonary segments. The
pinnacle of the superior lobe forms the
apical segment or segment I (S I). Below
and posterior to the apical segment is
the posterior segment (S II). When
viewed from the costal surface, this
segment is limited inferiorly by the
posterosuperior part of the right oblique
fissure and posterior part of the
horizontal fissure. As the name
suggests, the anterior segment (S III) is
anterior to the posterior segment and
anteroinferior to the apical segment. It
is limited inferiorly by the horizontal
fissure.

7.  The middle lobe of the right lung lies
between the horizontal (superiorly) and
the anteroinferior part of the oblique
fissures (inferiorly). It is subdivided into
lateral (S IV) and medial (S V)
bronchopulmonary segments. The
lateral segment is best represented on
the costal surface of the lung, while the
superficial boundary of the medial
segment wraps around the anterior
border of the lung. It tapers off at the
hilum and is superiorly related to the
oblique fissure.

8.  The inferior lobe of the right lung has five
bronchopulmonary segments. The superior
segment (S VI) is represented on both the costal
and mediastinal surfaces of the right lung; as the
segment also includes a portion of the posterior
border of the right lung. The medial basal
segment (S VII) is best represented on the
mediastinal surface of the lung, as it lies below
the hilum. It is anteriorly related to the posterior
basal segment (S X), which abuts the lateral basal
segment (S IX) around the posterior border of the
lung. The anterior basal segment (S VIII) is limited
anteriorly by the caudal part of the oblique
fissure and is juxtaposed with the lateral basal
segment posteriorly.

9. LEFT BRONCHOPULMONARY SEGMENTS
 The superior lobe of the left lung contains four
bronchopulmonary segments. The apicoposterior
segment (S I + II) represents the fusion of the
apical and posterior segments. It is limited
posteroinferiorly by the superior aspect of the
left oblique fissure and is adjacent to the
anterior segment (S III) of the superior lobe.
Although the lingular lobe of the left lung is
considered a part of the superior lobe, it is
analogous to the middle lobe of the right lung.
Similarly, it is divided into two
bronchopulmonary segments, namely the
superior (S IV) and inferior (S V) lingular
segments. The superior lingular segment is
located between the caudal boundary of the
anterior segment and the superior boundary of
the inferior lingular segment. Both are anterior
to the hilum of the left lung, and the inferior
segment is limited inferiorly by the inferior half

10.  The bronchopulmonary segments of the
left inferior lobe are almost analogous
to that of its right counterpart. There
are four (instead of five) segments on
the inferior lobe. The anteromedial
basal segment (S VII + VIII) represents
the fusion of the anterior basal and
medial basal segments. The other
segments (superior [S VI], posterior
basal [S X], and lateral basal [S IX])
maintain the same relative positions as
observed in the right lung

11. B D CHAURASIA'S HUMAN ANATOMY
REFERENCE

12. THANK YOU