Anatomy for anasthesia Flashcards
Position of trachea
Beginnning:
End:
Length
Crossection
Position
• •Begins at inferior border of cricoid cartilage (C6/7) extending to the carina.
• •Carina is at T4/5 or T6 on deep inspiration (manubrio-sternal notch in adults). It is at the 3rdcostal cartilage in children.
• •It is 11–13 cm long (5 cm being above the suprasternal notch).
• •In 33% of population it has an elliptical cross section with the transverse diameter > AP.
• •It is equal in dimensions in 25%.
• •Funnel shaped in children/cylindrical in adults.
Tracheal rings
- •Incomplete rings are approx 4 mm wide 1 mm thick.
- •They range from 12 to 22 in number.
- •They calcify with age leaving them more susceptible to trauma.
blood supply to trachea
- •Blood supply is segmental from a lateral longitudinal anastomosis.
- •Fed by branches from the inferior thyroid and bronchial arteries.
- •Perforating branches feed a rich submucosal plexus that feeds the cartilage from the luminal surface.
- •Bronchial arterial supply ends at the terminal bronchioles leaving the alveoli relatively sparsely supplied during single lung ventilation.
- •
Therefore alveolar are at risk of ischaemia during OLV.
• •
Over inflation of a tracheal cuff can readily impair capillary perfusion leading to ischaemic damage to the mucosa and ultimately the cartilage.
important anterior relations to trachea
Anterior.
•Brachiocephalic artery.
•Thyroidea ima artery (particularly relevant if performing a percutaneous tracheostomy).
•Azygos vein.
important posterior relations to trachea
Posterior
•Recurrent laryngeal nerves.
•Oesophagus.
importnat lateral relations to trachea
Lateral •Thyroid gland. •Carotid sheath. •Anterior jugular arch. •Deep cervical fascia.
important physiological influences on trachea
Inspiration.
•Diameter increases reducing resistance.
Expiration.
•Diameter decreases increasing velocity.
•Cilia beat 160–1500 times/min moving mucous 166 mm/min (impaired muco-ciliary escalator with smoking)
difference between bronchi
Right main bronchus
• •Wider, shorter (2cm), steeper and in line with the trachea.
•Gives rise to 10 segments
Left main bronchus
• •Narrower, longer (5cm) and more horizontal.
• •Gives rise to 8 segments
surgical points re trachea
Special points
• •Adult male trachea diameter 2.3cm, female trachea 2/3 diameter.
• •Blood supplies to cartilage via vulnerable submucosal plexus, remember endobronchial cuffs can cause ulceration!
• •Trachea is enveloped in connective tissue sheath facilitating descent of infections.
• •Cervical trachea susceptible to direct injury and deceleration injury.
• •Thoracic trachea susceptible to compression and barotrauma.
• •Right endobronchial tube more difficult to place due to RULMB
• •Tubes and aspirated material tend to go down the right bronchus.
• •Anomalous tracheal origin of RULMB in 0.5% (frequently only apical segment).
• •RLLMB is susceptible to flooding when a prone patient aspirates.
• •Right pneumonectomy is a risk factor for a bronchopleural fistula.
Top
Ascending aorta
Location:
Relations:
Branches
LOCATION • •Lying in the middle mediastinum, approximately 5 cm long, beginning at the base of the left ventricle and curving forwards and right behind the sternum to the 2nd right costal cartilage. RELATIONS • Anterior. • •Pulmonary trunk. • Posterior. • •Right pulmonary artery/left atrium/right main bronchus. • Anatomical left. • •Pulmonary trunk/left atrium. • Anatomical right. • •SVC/right atrium. BRANCHES • •Right and Left coronary arteries.
aortic arch
location
relations
branches
LOCATION
• •In continuation with the ascending aorta, lying in the superior mediastinum.
• •Arches backwards and to the left behind the manubrium, over the right pulmonary artery and left main bronchus, ending at the level of the 2ndleft costal cartilage.
RELATIONS
• •Anterior.
• •Left vagus nerve/left phrenic nerve.
• •Posterior.
• •Left recurrent laryngeal nerve (loops from vagus)/trachea/oesphagus.
BRANCHES
• •Brachiocephalic artery.
• •Left common carotid.
•Left subclavian artery.
descending thoracic aorta
location
relations
branches
LOCATION • •In continuation with the arch, beginning at the level of the 4ththoracic vertebra and lying in the posterior mediastinum. • •Initially lying to the left of the vertebrae, it inclines medially lying anterior to 12th vertebral body as it passes behind the diaphragm becoming the abdominal aorta. RELATIONS • •Anterior. • •Left hilum/left atrium. • •Posterior. • •Vertebral column/hemiazygous veins • •Anatomical right. • •Azygous vein/thoracic duct/oesphagus. • •Anatomical left. • •Pleura and left lung. BRANCHES • •Pericardial. • •Right and left bronchial arteries. • •Oesophageal arteries. • •Nine paired posterior intercostal arteries. • •Paired subcostal arteries.
superior vena cava
location
relations
LOCATION
• •Returns blood from all structures above the diaphragm except the lungs and the heart.
• •Formed from the union of the right and left brachiocephalic veins at the first right costal cartilage.
• •Terminates when it enters the right atrium at the level of the third costal cartilage.
• •The superior part lies in the right superior mediastinum while the terminal part is in the middle mediastinum.
• •The Azygous vein also drains into the SVC just prior to it entering the pericardium.
RELATIONS
• Anterior.
• •Pleura/right lung.
• Posterior.
• •Right pulmonary hilum.
• Anatomical right.
• •Right phrenic nerve/right lung.
• Anatomical left.
• •Trachea(posterior)/right vagus nerve.
brachiocephalic veins
Brachiocephalic veins
• •The Brachiocephalic veins are formed by the union of the internal jugular and subclavian veins on each side.
• •Due to the SVC being right of the midline, the left brachiocephalic vein must pass obliquely and downward behind the manubrium sternum anterior to the branches of the aortic arch.
IVC describe function and location, relations
- •Returns blood from all structures below the diaphragm.
- •It is formed by the union of the common iliac veins and ascends anterior to the vertebral bodies to the right of the aorta.
- •It pierces the tendonous part of diaphragm at the level of T8 vertebra and almost immediately enters the right atrium.
Hemiazygous and accessory hemiazygous veins
• •These veins are analogous to the azygous vein but ascend and descend respectively to the left of the vertebral column, crossing posterior to the aorta at variable levels to drain into the azygous vein.
