Thoracic cavity and its contents
By Dr. K.Velaei
Assistant Prof. of Medical Anatomical Science
Thorax (chest) cavity
The thorax is an irregularly
shaped cylinder with a narrow
opening (superior thoracic
aperture) superiorly and a
relatively large opening (inferior
thoracic aperture) inferiorly
Sup. and Inf. thoracic apertures
Sup. thoracic aperture
The superior thoracic
aperture consists of:
The body of vertebra TI
posteriorly
The medial margin of rib I on
each side
The manubrium anteriorly
Sup. thoracic aperture
Structures that pass between the
upper limb and thorax pass over
rib I and the superior part of the
pleural cavity as they enter and
leave the mediastinum
Structures that pass between the
neck and head and the thorax
pass more vertically through the
superior thoracic aperture.
Inf. thoracic aperture
The Skeletal elements of the
inferior thoracic aperture are:
The body of vertebra TXII posteriorly
Rib XII and the distal end of rib XI
posterolaterally
The distal cartilaginous ends of ribs VII to X,
which unite to form the costal margin
anterolaterally
The xiphoid process anteriorly
Inf. thoracic aperture
The musculotendinous
diaphragm seals the
inferior thoracic aperture
Because of the oblique angle
of the inferior thoracic
aperture, the posterior
attachment of the diaphragm
is inferior to the anterior
attachment
Diaphragm
It consists of:
1. Central tendon
2. Peripheral muscle fibers
Diaphragm
Origin: Xiphoid process
(posterior surface), lower six
ribs and their costal cartilage
(inner surface) and upper three
lumbar vertebrae as right crus
and upper two lumbar vertebra
as left crus.
Insertion: central tendon
Diaphragm
The origin of muscle
fibers are grouped in 3
parts:
1. Sternocoatal part
2. Arcuate ligaments part
3. Lumbar part (crura)
crus (singular form), crura (plural form)
Crura of Diaphragm
Right and Left crura
Ligaments of Diaphragm
Medial and lateral arcuate ligaments
L
1
Major openings in
Diaphragm
Caval opening (T8 level):
Transmits the inferior vena cava
Esophageal opening (T10 level):
Transmits the esophagus
Aortic opening (T12 level):
Transmits the aorta
Main pathways through the Diaphragm
Innervations of
diaphragm
Phrenic nerve (C3,C4 and C5)
from cervical plexus: motor
to whole organ and sensory nerves
to central part of diaphragm
Lower 6 intercostal nerves: sensory
nerve to peripheral part of
diaphragm
Innervations of diaphragm
Function of Diaphragm
Main respiratory muscle
The diaphragm is also involved in
non-respiratory functions, helping
to expel vomit, faeces,
and urine from the body by
increasing intra-abdominal
pressure
The diaphragm prevents acid
reflux by exerting pressure on
the esophagus as it passes
through the esophageal hiatus.
diaphragmatic hernia
Summary of diaphragmatic hernia:
a. Congenitalb. Acquired
- Congenital hiatal (rolling hernia)
- Acquired hiatal (sliding hernia)
Hiatal hernia
- A congenital hiatal hernia: The stomach can roll upwards until it lies upside
down in the posterior mediastinum. It is, therefore, called a rolling type of hernia. It is a
junction
rare type of hernia where the normal relationship of the cardio-oesophageal to
the diaphragm is undisturbed, and, therefore, the mechanics of the cardio-oesophageal
junction
usually remains unaltered
- An acquired hiatal hernia: is the
commonest of all internal hernia.It is often caused
by obesity, or by operation in this area. The
cardiac end can slide up through the hiatus. In this
way the valvular mechanism at the cardio-
oesophageal junction is disturbed causing reflux of
gastric contents into the oesophagus.
Unilateral paralysis of the diaphragm
is due to a lesion of the phrenic nerve
anywhere in its long course, is a common
occurrence.
The paralyzed side moves opposite to the
normal side, paradoxical movements
Most patients with unilateral
diaphragmatic paralysis are asymptomatic
and require no treatment. Some may
report shortness of breath, particularly on
exertion.
Bilateral paralysis of the diaphragm is rare
but can cause significant respiratory
distress.
Chest x-ray, showing paralysis of the right hemi-
diaphragm
Thoracic cavity
The thoracic cavity enclosed
by the thoracic wall and the
diaphragm is subdivided into three
major compartments:
1,2- Left & right pleural cavities
3- Mediastinum
Pleura
The pleura (is lined by a single layer of
flat cells or mesothelium) is divided into
two major types, based on location:
Parietal pleura (associated with the walls
of a pleural cavity)
Visceral pleura (adheres to and covers
the lung)
Visceral pleura
The serous layer of the visceral pleura covers
the surfaces and fissures of the lung, except at
the hilum and along the attachment of the
pulmonary ligament
Parietal pleura
The names given to the parietal pleura
correspond to the parts of the wall that
they are associated with
1. Costal part
2. Mediastinal part
3. Diaphragmatic part
4. Cervical pleura
Parietal pleura
Pleura and Pleural Cavities
The potential space
between the serous
membrane layers is a
pleural cavity.
The pleural membranes
produce a thin, serous
pleural fluid that
circulates in the pleural
cavity and acts as a
lubricant, ensuring minimal
friction during breathing.
Pleural recesses
There are two recesses of parietal pleura, which act as 'reserve
spaces' for the lungs; to expand during deep inspiration
Costomediastinal recesses
Costodiaphragmatic recesses
recess
/rɪˈsɛs,ˈriːsɛs/
a small space created by building part of a wall further back from the
rest
Pleural recesses
Costodiaphragmatic
recesses: lies inferiorly
between the costal and
diaphragmatic pleura.
Vertically it measures about 5
cm, and extends from the
eighth to tenth ribs along the
midaxillary line 8
6
1
0
Pleural recesses
Costomediastinal
recesses: lies anteriorly,
behind the sternum and costal
cartilages, between the costal
and mediastinal pleurae,
particularly in relation to the
cardiac notch of the left lung
Lungs
Left lung
divided into 2 lobes by oblique
fissure
smaller than the right lung
cardiac notch accommodates the
heart
Right lung
divided into 3 lobes by oblique
and horizontal fissures
R. L.
Lung Lung
Ant Pos Pos Ant
. t. t. .
Lungs
Each lung has a half-cone shape,
with a base, apex, two surfaces, and
three borders:
Apex
Base
Surfaces: lateral(costal surface) &
medial (mediastinal surface)
Border(Ant & Pos & infer)
Lungs
Hilum
Pulmonary Lig.
Left Lungs
Cardiac Notch
Lingula
Root of Lung
Root of Lung
Within each root and located in the hilum are:
Pulmonary artery
Pulmonary vein
Main bronchus
Bronchial vessels
Pulmonary plexus
Lymphatics
Arrangement of structures in roots
R. Lung
Major structure related to R. Lung
L. Lung
Major structure related to L. Lung
Trachea
From C6 to
T4-T5
10- 12 cm
12 mm
diameter in
adult
Carina of
trachea
4
1
Bronchial tree
Main (primary) bronchi
Lobar (secondary) bronchi
Segmental (tertiary) bronchi
NOTE: Bronchus (singular form), bronchi (plural form)
Bronchial Tree
Bronchopulmonary segments
A bronchopulmonary segment is the area of lung supplied by a
segmental bronchus and its accompanying pulmonary artery branch.
Bronchopulmonary segments
There are ten
bronchopulmonary
segments in each lung
some of them fuse in the
left lung
Bronchopulmonary segments
Each bronchopulmonary segment
is shaped like an irregular cone
A bronchopulmonary segment is
the smallest functionally
independent region of a lung
The smallest area of lung that can
be isolated and removed without
affecting adjacent regions
Pulmonary innervation
Anterior and posterior
pulmonary plexuses
They are situated in front of
and behind the lung roots
Branches of vagus nerves and
sympathetic trunk form these
plexuses
Pulmonary innervation
1. Parasympathetic nerves are derived from the vagus.
These fibres are:
Slows rate of breath
Motor to the bronclrial muscles, and on stimulation cause bronchospasm.
Secretomotor to the mucous glands of the bronchial tree.
Sensory fibres are responsible for the stretch reflex of the lungs, and for the cough
reflex.
2. Sympathetic nerves are derived from second to fifth sympathetic
ganglia.
Increases breath rate
These are inhibitory to the smooth muscle and glands of the bronchial tree.
That is how sympathomimetic drugs, like adrenalin, cause bronchodilatation and
relieve symptoms of bronchial asthma
Lymphatic
drainage of lungs
Superficial, or subpleural, and
deep lymphatics of the lung drain
into lymph nodes called
tracheobronchial nodes
around the roots of lobar and
main bronchi and along the sides
of the trachea.
Pleural effusion
with too much fluid
Auscultation of lung
Upper lobe is auscultated above 4th rib on both sides
lower lobes are best heard on the back
Middle lobe is auscultated between 4th and 6th ribs on right side
