chest drain and the thoracic cavity Flashcards
describe thoracic wall anatomy
- cone-shaped with thoracic inlet at apex
- walls formed by ribs and intercostal muscles laterally and diaphragm caudally
Laterally- ribs and intercostal spaces
Dorsally- vertebral column
Ventrally- sternum and costal cartilages
Caudally- diaphragm
Describe the structure of the ribs
- Dorsal bony part & a cartilaginous ventral part articulating at a costo-chondral junction.
- Head with 2 articular facets for articulation with vertebrae.
- Neck
- Tubercle with facet for articulation with transverse process of the more caudal vertebra
- Angle
- Body
- Cartilage
Describe the difference between true and false ribs
True ribs- articulating directly with the sternum.
False ribs- articulating indirectly through connection of the cartilage with that in front (costal arch)
Last rib may not have contact with neighbour.
How many (pairs of) ribs does a horse, dog, cat and cow have?
Horse- 18
Dog- 13
Cat- 13
Cow- 13
Describe the structure of the intercostal muscles
- External and internal intercostal muscles between the ribs.
- Intercostal vein/artery/nerve caudal to the rib.
- External and internal muscles occupy the intercostal spaces.
- External intercostal lie superficially and fibres run obliquely, downward and forward, from the rib above to the rib below.
- External intercostal - inspiratory action “expand”.
- Internal intercostals- two components- Interosseous (expiratory)- situated between bones, interchondral (inspiratory)- between cartilage.
describe the innervation of intercostal muscle
- innervated by the corresponding thoracic spinal nerves
describe the structure of the diaphragm
- major muscle of inspiration
- striated musculature
- motor and sensory innervation by the phrenic nerve (originates from C4 with some fibres from C5 and the cervical plexus)
- insertion at inner aspect of thorax, ribs and sternum and via two crura to lumbar vertebrae (tendinous structures that extends below the diaphragm to the vertebral column. There is a right crus and a left crus, which together form a tether for muscular contraction.)
name the openings in the diaphragm for the caudal vena cava, esophagus, aorta and thoracic duct
- The caval foramen allows the caudal vena cava to pass through the diaphragm.
- Oesophageal Hiatus- oesophagus
- Aortic Hiatus- aorta and thoracic duct
Describe the lung field and how it varies between species
Projection of lungs on the surface of the body caudal to forelimb. Recognising lung fields is important in auscultation. The lung fields in a cow are particularly small due to the steep angle of the diaphragm.
identify:
heart in pericardium
lungs
arteries and veins, including aorta
esophagus
nerves and ganglia
diaphragm
phrenic nerve
vagus nerve
thymus
thoracic duct
- Heart in pericardium
- Lungs (largely removed)
- Arteries & veins, including aorta (3*)
- Oesophagus
- Nerves & ganglia
- Diaphragm
- Phrenic nerve
- Thymus
Label the structures seen in this dissection of the right thoracic cavity
- Heart
- Lungs
- Trachea
- Arteries and veins
- Sympathetic trunk
- Diaphragm
- Phrenic nerve
- Brachial plexus
Describe the role and structure of the serous membrane
- the surface of the inner wall of the body cavities is lined by a serous membrane
- single layered flat epithelium with thin underlying connective tissue
- the membrane is named pleura in the thoracic cavity and peritoneum in the abdominal and pelvic cavities`
describe the structure and function of the pleura
- each lung has around it a serous membrane called pleura
- two pleural membranes are arranged as closed pleural sacs
- the contact region between the right and left pleural sac is the mediastinum
- pleura covering the surface of the lung is called the visceral/pulmonary pleura. it is reflected around the root of the lung where it joins the bronchi and becomes continuous with the mediastinal pleura.
- this in turn continues with the diaphragmatic parietal pleura and then costal pleura
- visceral pleura coats the lung
- parietal pleura lines the thoracic cavity
Describe the structure and function of the pleural cavity
- the narrow space between the parietal and viscera pleura is the pleural cavity
- it contains a small amount of serous fluid spread over the surface of the pleura
- establishes adhesion with the thoracic wall (think 2 glass slides with fluid in between them
- facilitates smooth movement
- lung follows movements of diaphragm and thoracic wall
- sub-atmospheric pressure
what is pneumothorax
an accumulation of air in the pleural space an is a frequent cause of dyspnoea in dogs and cats
- causes an increase in intrathoracic pressure and collapse of the lungs
- Causes of pneumothorax- trauma e.g. hit by car (HBC/RTA); spontaneous, iatrogenic, cysts, abscesses, migrating foreign body, secondary to other disease.
indicate the mediastinum
