outlet of thorax
DESCRIPTION
OUTLET OF THORAX. By- Dr Garima Sehgal. Components of thoracic cage. Thoracic vertebrae Ribs & costal cartilages Sternum. S uperior and inferior apertures of thorax. Outlet (inferior aperture) Closed by a diaphragm ?. Inlet (superior aperture) Closed by a diaphragm ?. - PowerPoint PPT PresentationTRANSCRIPT
OUTLET OF
THORAX
By-Dr Garima
Sehgal
Components of thoracic
cage•Thoracic
vertebrae•Ribs & costal
cartilages•Sternum
Inlet (superior aperture)
Closed by a diaphragm ?
Outlet (inferior aperture)
Closed by a diaphragm ?
Superior and inferior apertures of thorax
Location
Attachments (Origin) –inferior view
• Sternal
• Costal
• Lumbar
There are three large openings,
1) Aortic, 2) Oesophageal3) Vena caval
and a number of smaller ones.
Apertures of the diaphragm
osseo-aponeurotic opening
Lowest & most posterior
to the left of the midline
level -lower border of T-12
lies behind the diaphragm
Transmits aorta, thoracic duct, lymphatic trunks from the lower posterior thoracic wall and, sometimes, the azygos and hemiazygos veins
Aortic aperture
Oesophageal aperture Level T-10 in front and left of, the
aortic opening is bounded by muscle
fibres of the right crus. It transmits oesophagus, gastric nerves, oesophageal branches
of the left gastric vessels
lymphatics
Vena caval aperture Highest Level disc between
T-8 & T-9 quadrilateral, and
located in the central area of the tendon –so aponeurotic.
traversed by – inferior vena cava
and by some branches of the right phrenic nerve.
Two in each crus: one transmits the greater,other the lesser, splanchnic nerve.
Intercostal nerves and vessels pass in between the muscular slips of origin
Sympathetic trunks usually enter the abdominal cavity behind the medial arcuate ligament.
Subcostal nerves and vessels pass behind the Openings for minute veins frequently occur in
the central tendon
Lesser apertures
Thoracic aspect of diaphragm
Inferior view
Superior relations of diaphragm
Inferior relations of diaphragm
lower five intercostal & subcostal arteries
phrenic arteries 1. Superior phrenic2. inferior phrenic3. Musculophrenic4. Pericardiophrenic5. Superior
epigastric
Vascular supply and lymphatic drainage
The right phrenic vein ends in the inferior vena cava.
The left phrenic vein is often double:
Phrenic veins
one branch ends in the left renal or suprarenal vein, the other passes anterior to the oesophageal opening to join the inferior vena cava.
two phrenic nerves originate in the neck and
pass down between the lung and heart to reach the diaphragm.
Root value (C3-C5) predominantly C4.
The phrenic nerves contain motor, sensory, and sympathetic nerve fibers.
Phrenic nerve
Motor supply - the phrenic nerves
Sensory fibres –
periphery - lower six or seven intercostal nerves
central part - Phrenic
Innervation
•Right crus - both right and left phrenic nerves. •crural fibres contract slightly before the costal part, and this may be functionally significant.
Where do they pierce ?
phrenic nerve supplies the parietal pleura parietal peritoneum below, and the central diaphragm.
Phrenic nerves contd…..
The trunk divides into three branches - an anterior (sternal) branch
- anterolateral branch- - short posterior branch
in avoiding surgical damage.
Thoracoabdominal incisions in a circumferential manner do not involve any significant branches of the phrenic nerves and preserve diaphragmatic function.
incisions of the central tendon are safe.
Clinical importance
is the major muscle of inspiration (67% of the vital capacity)
diaphragm lends additional power to all expulsive efforts like sneezing, coughing, laughing, crying, urinating, defaecating etc.
in lifting heavy weights.
muscular pump
Sphincter to orifice
Functions of the diaphragm
Diaphragmatic excursion - 1.5 cm in quiet breathing. During deep ventilation - from 6 to 10 cm.
After a forced inspiration right cupola - level of T- 11left cupola – T-12
After a forced expirationright cupola -level anteriorly with the fourth costal cartilage, laterally with the fifth, sixth and seventh ribs, and posteriorly with the eighth and the left cupola is a little lower
Range of movement
Septum transversum
Pleuroperitoneal fold
Mesentry of oesophagus
Body wall
Development of diaphragm
APPLIED ANATOMY
Posterolateral diaphragmatic hernia
Sliding, or type I, hiatus hernia
laxity of the phreno-oesophageal membrane, allows the gastro-oesophageal junction to slide into the thorax
usually acquired, commonly occurs in the
fifth decade of life. found in more than 50% of
patients with gastro-oesophageal reflux.
Hiatus hernia
Para-oesophageal, or type II, hiatus hernia
When the stomach herniates into the thorax alongside the oesophagus
Reflux of gastric contents into the oesophagus,
risk of inhalation into the lungs prevented by a physiological antireflux
barrier located at the gastro-oesophageal junction
components of this barrier 1. specialized smooth muscle of the wall 2. fibres of the crura
Oesophageal reflux
Repeated stress may eventually compromise the integrity of the hiatus, so that the muscular hiatal tunnel widens.
Referred pain – pain arising from structures served by the phrenic nerve is often to other somatic regions served by spinal nerves C3-C5. (Kehr's sign ?).
A hiccough is a spasmodic contraction of the diaphragm, which pulls air against the closed folds of the larynx. Irritation of the phrenic nerve (or the tissues supplied by it) leads to the hiccough reflex.
Patients suffering spinal cord injuries below the neck are still able to breathe effectively, despite any paralysis of the lower limbs as the phrenic nerve arises from the neck (C3-C5)
The phrenic nerve may be involved in traumatic lesions of the upper brachial plexus. Cardiac surgery thoracic surgery, tumours of the lung or mediastinum infections such as typhoid and polio. Division in the neck completely paralyses the
corresponding half of the diaphragm, which atrophies.
leads to paradoxical movement of the diaphragm
best observed fluoroscopically
Lesions of the phrenic nerve