Thoracic Cavity Contents Flashcards
What are the contents of the thoracic cavity?
two pleural sacs (right contains right lung and left contains left lung)
mediastinum - midline
Describe esophagus location in mediastinum
- has cervical, thoracic, short abdominal parts
- thoracic part: runs in dorsal mediastinum from thoracic inlet to esophageal hiatus
- cranial mediastinum: dorsolateral trachea on left side
- caudal mediastinum: ventral to ascending aorta and dorsal to caudal vena cava
What is structure 1 and 2?
esophagus
compare the muscle of esophagus in different species
- tunic muscularis skeletal m. throughout in ruminants and dog, but horse, pig, and cat it change to smooth m. caudal to heart
describe thoracic trachea
- starts as most dorsal visceral structure entering cavity (directly ventral to longus colli)
- in mediastinum inclines ventrally and attains position ventral to esophagus at aortic arch
- terminates near heart base and divides into two principal bronchi
What is tracheal bifurcation?
- trachea terminates near heart base, it divides into two principal bronchi (primary), occurs at T5
What is the order of respiratory passageways from largest to smallest?
- trachea –> principal bronchi (right and left) –> lobar bronchi (1/lobe) –> segmental bronchi (each serves one whole bronchopulmonary segment) –> subsegmental bronchi –> true and terminal bronchioles (lack cartilage) –> alveolar ductules –> alveoli
describe bronchopulmonary segments
- each lobar bronchus divides into many segmental bronchi
- each segmental bronchus and tissue it supplies with air a bronchopulmonary segment (self-contained unit)
- cone shaped with base toward pleura
- can remove a unit
What is the tracheal bronchus?
- in ruminants and pig
- starts cranial to bifurcation
- serves right cranial lobe
what is lung orientation?
- horizontal in thorax
what are the basic features of lungs?
- apex (directed cranial toward thoracic inlet)
- base (diaphragmatic surface)
- lobes (based on division of lobar bronchi within lung parenchyma
- interlobar fissures (separate between lobes)
name the lobes of the right lung
- right cranial lobe
- middle lobe
- right caudal lobe
- accessory lobe (medial to caudal lobe and surrounds caudal vena cava and phrenic n. see #3)
name the lobes of the left lung
- left cranial lobe (cranial part and caudal part)
- left caudal lobe
what is the hilus?
- area on medial surface where structures enter or exit lung
what structures enter/exit through hilus?
- enter: primary bronchus, bronchial artery, pulmonary artery, autonomic nerves
- exit: pulmonary veins, bronchial veins (satellites of bronchoesophageal artery), sensory nerves, lymphatics
what is the root of the lung?
- all the collected structures enter/exit hilus wrapped in pleura (double fold)
what lobe is most prone to lung lobe torsion and why?
- right middle lobe due to its freedom of movement and deep fissures that separate it from other lobes
- occurs in deep chested dogs
- lobectomy (dogs and cats) can survive up to 50% lung loss
what is lung lobe torsion?
- rotation of lobe along its axis - twists bronchus and pulmonary vessels leading to necrosis
discuss differences in ox lung lobes
- 2 left lung lobes are the same
- right cranial lobe is supplied by tracheal bronchus which comes off cranial to bifurcation
- right cranial lobe divided into cranial and caudal parts
- same with pigs and camels
discuss horse lung lobes
- 2 left lung lobes but cranial lobe is not divided into parts
- 3 right lung lobes - no middle lobe
what is the cardiac notch?
- region where the heart is not overlaid by lung tissue
- triangular space between cranial and middle lobes of rt. lung where borders diverge from each other leaving portion of pericardial wall uncovered by lung tissue
- apex of notch at distal quarter of 4th rib between sternum and CCJ
- a window for needle puncture of pericardium, heart and auscultation or ultrasound exams
- also cardiac notch on left side
- present in all species
Where does heavier particles such as fluid travel in lung?
- tends to land right cranial and middle lobes due to them being more ventral and gravity
where do lighter air-borne particles tend to travel in lung lobes?
- inhaled into accessory lobe due to straight trajectory
where is the auscultation triangle?
- cranial: caudal border of triceps brachii
- dorsal: epaxial muscles
- caudoventral: curved line from olecranon to intercostal space between ribs #16 and #17
what are the rules for pleurocentesis or thoracocentesis?
- puncture in middle of ICS
- dorsal to CCJ
- ox and horse at 7th ICS above the CCJ
- horse avoid superficial thoracic spur vein
which side of azygous vein is present in carnivores and horse?
- right v. azygos
which side of the azygous vein is present in ruminants and discuss its location
- they have both
- runs left dorsal surface of aorta and must make a u-turn to get to R ventricle
- drains into coronary sinus
discuss R. azygous vein
- unpaired (carnivores and horse)
- runs along right dorsal surface of aorta
- drains into cranial vena cava
- both veins develop in embryo but left atrophies
how many lymphocenters are present in thorax and name them?
- 4
- dorsal thoracic
- ventral thoracic
- mediastinal
- bronchial
what lymph nodes are present in dorsal thoracic lymph center?
- intercostal lnn
what lymph nodes are in ventral thoracic LC?
- sternal lnn
what lymph nodes are present in mediastinal LC?
- represented by cranial mediastinal lnn in all species
- caudal mediastinal lnn (absent in carnivores, huge in ruminants)
what lymph nodes are in bronchial LC?
- rt. lt. and middle tracheobronchial lnn
what special lymph node do ruminants have and what is clinical significance?
- caudal mediastinal lymph node
- a single large elongated lnn between aorta and esophagus
- if enlarged it will press on esophagus and dorsal vagal trunk which causes vagal indigestion and no eructation (gas cannot exit)
- # 20 is vagus nerve
what are different in city dogs and how?
- tracheobronchial lnn. and pulmonary are darker
what is significant about sternal lymph node?
- lymph from peritoneal cavity drains into sternal ln. via afferent lymphatic duct which perforates diaphragm near costodiaphragmatic recess and runs along internal thoracic vessels covered by transversus thoracic m.
- may drain cranial mammary glands, so may take up tumor cells
what is unique about T6 as a landmark?
- longus colli m. arises from T6
- thoracic duct deviates from right to left at T6
- on lat rad carina shows up as circular dark spot at T6
- tracheobronchial lymph nodes located in relation to carina, can be ID if abnormal rad
describe thoracic duct and clinical significance
- transports fat absorbed from digestive tract to venous circulation, material within called chyle
- can be visible on left lat side of esophagus cranial to aortic arch - avoid in sx
What is at 1
- thoracic duct
- arises cisterna chyli between 2 crura and runs cranially along rt dorsal surface of aorta, at T6 crosses cranioventrally to left in groove between esophagus and left longus colli
- then opens in area where left sub and external jug veins join
what is chylothorax?
- when lymph accumulates in thorax cavity
- if lymph vessels cut they remain open due to lack of clotting factors in lymph
- will not resolved unless sx intervention taken to ligate duct
where is the heart in a dog?
- middle mediastinum and partially left to median
- ribs 3 to 6
- 45 degree axis
where is heart in the cat?
- middle mediastinum
- partially left to median
- ribs 4-7 (more caudal then dogs)
- 25-30 degree axis
where is heart in horse?
- ICS 2-6
- more perpendicular than carnivores
where is the heart in ox?
- ICS 2-5
what is the pericardium?
- triple fibroserous sac enclosing the heart and the beginnings of large blood vessels connected to it
- serous pericardium and fibrous pericardium
what is the fibrous pericardium?
- condensation of endothoracic fascia and it is tightly adhered to parietal serous pericardium
- mediastinal pleura is superficial to it
what is cardiac tamponade?
- pericardial sac fills with fluid
- fibrous nature of parietal pericardium prevents expansion and heart is compressed (especially thin R ventricle)
what is pericardiocentesis?
- insert needle or catheter from right side @ 4th or 5th ICS between sternum and CCJ
- dx or relieve inc pressure in cavity
what are the main structures of the heart
- base (2 atria)
- apex (left ventricle)
- 4 chambers: right and left atria, right and left ventricles
what part of heart is cranial?
right
what part of heart is caudal?
left
what are the grooves of the heart?
- coronary groove
- two interventricular grooves
- intermediate groove (ruminants)
what is the coronary groove?
- separation of atria and ventricle
what are the interventricular grooves?
- two of them indicate interventricular septum inside
- paraconal on left
- subsinuosal on right
what is the left side of heart called?
- auricular surface
- see auricles with pulmonary trunk in between
what is the right side of heart called?
- atrial surface
- see cranial and caudal venae cavae entering right atrium
what are the septa in heart?
- divide left and right sides
- interatrial septum
- interventricular septum
what are the valves of the heart?
- semilunar valves
- atrioventricular valves (AV)
what are the semilunar valves?
- between ventricles and great arteries
- aortic and pulmonary
what are the AV valves?
- between atria and ventricles
- tricuspid (right blue side) and mitral (left aka oxygenated side)
what is/are branch of aortic arch in horse?
brachiocephalic trunk
what is/are branches of the aortic arch in carnivores?
- brachiocephalic trunk
- left subclavian artery
what is the best places to auscultate heart in dog?
- PAM aka 345 on left side
- pulmonic valve in 3rd ICS at CCJ
- aortic valve in 4th ICS at point of shoulder
- mitral valve in 5th ICS low along sternal border
- tricuspid on right side in 4th ICS at CCJ
