Thoracic Cavity Anatomy 1 Flashcards
What is a part of the thoracic cage? (4)
• Thoracic vertebrae
• Ribs & intercostal mm
• Sternum
• Thoracic outlet
What are the borders of the thoracic inlet? (3)
• T1 vertebra & longus colli m.
• first pair of ribs
• manubrium of sternum
What are the 7 structures that pass through the thoracic inlet
• Esophagus
• Trachea
• External jugular vv
• Common carotid aa
• Vagosympathetic trunks
• Recurrent laryngeal nn
• Roots of the phrenic nn
Boundaries of the thoracic outlet (4)
• Last thoracic vertebra
• Last pair of ribs
• Xiphoid
• Diaphragm
External intercostal muscles run…
caudoventrally
Internal intercostals run…
cranioventrally
What muscles act to increase (inspire) the volume within the thoracic cavity? (6)
❶ External intercostal
❷ Serratus dorsalis cranialis
❸ Scalenus
❹ Rectus thoracis
❻ Diaphragm
what innervates the inspiratory and expiratory muscles?
Ventral branches of thoracic spinal (intercostal) nerves
What are the 3 muscles to decrease (expire) the volume of the thoracic cavity?
1 Internal intercostal
2 Serratus dorsalis caudalis
3 Transversus thoracis
2 intercostal arteries
ventral and dorsal intercostal arteries
what does the dorsal intercostal veins lead into?
Azygous vein
where do the ventral intercostal veins lead into?
internal thoracic vein
Where would you place an intercostal nerve block
the (proximal) CAUDAL part of the rib
- for thoracotomy pain
(the ICS VAN runs along the caudal border,
poor placement = hemorrhage/pain)
What is the connective tissue of the mediastinum made of?
endothoracic fasia
what is the diaphragm innervated by?
phrenic nerve
2 Parts of the diaphragm
tendinous center (V-shape) and muscle (periphery)
3 parts of the muscle part of the diaphragm
lumber (R and L crura L3 &L4)
Costal
sternal
3 openings of the diaphragm
- Aortic hiatus
-Esophageal Hiatus
-Caval foramen
What is the diaphragmatic cupula
the most cranial portion of the diaphragm
What happens during a traumatic diaphragmatic rupture?
dogs and cats (automobile)
costal part = high mortality
liver is also usually herniated along with the diaphragm
Losing 1 or both phrenic nerves cause?
nothing at first, but causes hypertrophy of inspiratory muscles to compensate for the paralyzed diaphragm
What are the 4 body serous membranes
pleura
pericardium
peritoneum
vaginal tunic
*with respective cavities - and no viscera!!!
what is the peritoneum
serous membrane in the abdominal and pelvic cavities
what is the vaginal tunic
serous membrane surrounding the testicles
2 regions of the parietal pleura
costal pleura - lines ribs and intercostal muscles
diaphragmatic pleura - covers diaphragm
4 regions of the pleura
- visceral pleura
- parietal pleura
- mediastinal pleura
- pericardial pleura
Which species is the mediastinal pleura the biggest
the ox
why do dogs and cats rarely present with unilateral pneumothorax
the mediastinum pleura is weak and thin (described at fenestrated) so if one lung collapses, the other has a high probability of collapse
What are the pleural cupulae
the most cranial part of the pleural sacs
cup-shaped bubbled - protrude into the thoracic inlet
what is the clinical importance of the pleural cupula
it can be injured by penetrating wounds at the base of the neck, and result in pneumothorax and lung collapse
(keep the cupula in mind when performing surgery in the caudal portion of the neck)
What is the plica venae cavae
a fold in the mediastinal pleural on the RIGHT side that surrounds the caudal vena cava and right phrenic nerve
What is the mediastinal recess
small space medial to the plica venae cavae and is occupied by the accessory lobe
2 regions of the mediastinum
cranial (inlet to heart), middle (cardiac), and caudal (heart to diaphragm)
Cranial mediastinum contents
Dorsal portion
• esophagus, trachea, great vessels of heart (Brachiocephalic trunk and cranial vena cava)
Middle and ventral portions:
• Thymus (in young then regress)
• Internal thoracic arteries and veins
• Cranial mediastinal lymph nodes
contents of the middle mediastinum
Contents in the dorsal portion:
• esophagus, tracheal bifurcation and root of lung
• tracheobronchial lymph nodes, aortic arch
(trachea ends here)
Contents in the middle and ventral portions:
• Heart and pericardium, folds of pleural tissue
contents of the caudal mediastinum
Contents in the dorsal portion:
• Esophagus, aorta & right azygos vein
Contents in the middle portion: caudal vena cava
• The ventral portion is reduced to the potential space between the layers of pleura.
where the costal pleura reflects onto the diaphragm, forms the
costodiaphragmatic recess
Read this slide
Where is the line of pleural reflection
extends from the 8th costal cartilage (sternum) along a curved angle to the last rib
Basal border of the lung
run from the 6th CCj to the second to last ICS at the border of the epaxial muscles
(parallel the pleural line of reflection
Clinical application of knowing the basal border of the lung
area for lung sound auscultation
safe area for thoracic puncture
what is the costodiaphragmatic recess
space where diaphragmatic and costal pleura are in direct contact without intervening lung
(bottom corner of the lung)
where would you complete a thoracocentesis (tapping pleural cavity)
done just dorsal to the superficial thoracic vein in the 7th ICS on the right side
and 8th or 9th ICS on the left side
insert needle midway between two ribs to avoid injury of intercostal veins
In the horse, the superficial thoracic or “spur” vein, which courses along the thoracic body wall at about the level of the olecranon, should be avoided.
clinical significance of superficial thoracic “spur” vein
may get injured by digging in of the spurs worn by riders→hematoma
The superficial thoracic vein is a good landmark to denote the CCJ
problems caused by pleural effusions
limits lung capacity, lung collapse, and difficult breathing
Types of pleural effusion
hydrothorax (serous fluid)
haemothorax (blood)
pyothorax (pus)
chylothorax (chyle)
How can pneumothorax be caused
Externally - penetrating wound
Internally - lung trauma and damage to pulmonary pleura
(x-ray appears blacker since air is all up in the thorax)
3 parts of the esophagus
cervical, thoracic, and short abdominal part
Borders of the thoracic part of the esophagus
Runs in the dorsal mediastinum from thoracic inlet to esophageal hiatus
❶ Cranial mediastinum- dorsolateral to trachea on the left side.
❷ Caudal mediastinum- ventral to descending aorta and dorsal to the caudal vena cava
What is the tracheal bifurcation
where the trachea splits near the heart base and divides into the primary bronchi
pathway from the primary bronchi
-> lobar bronchi -> segmental bronchi -> subsegmental bronchi -> terminal bronchioles -> alveolar ductules -> alveoli
What is a bronchopulmonary segment
each segmental bronchus and the tissue it supplies with air (cone shaped apex)
What species have tracheal bronchus
ruminants, pigs, and camels
Where does the tracheal bronchus exit into?
right cranial lobe
4 parts of a lung
apex, base, lobe, interlobar fissue(seperate between lobes)
How many lobes does the right lung vs left lung have
Right 4: cranial, middle, caudal, and accessory lobe
Left 2: cranial and caudal
(cranial left has cranial and caudal portion in dogs and cats)
hilus vs the root of the lung
hilus: area on medial surface where structures enter/exit the lung
root: all the structures that enter/exit the lung
What is lung lobe torsion and which lobe is the most prone?
twisting of the bronchus and pulmonary vessels causing necrosis
The right middle lobe - due to its freedom of movement and that its more separate from other lobes (more often in deep-chested dogs)
Dogs and cats can survive with up to ____ % lung loss during a lobectomy
50%
differences in ox lungs
both right and left cranial lobes are divided into cranial and caudal parts
Horse lung difference
3 Right lung lobes
- cranial, caudal, accessory
2 left lung lobes
- cranial (undivided), and caudal
clinical significance for cardiac notch
window for needle puncture of the pericardium (pericardiocentesis), cardiac puncture, and auscultation or ultrasound exams
What is the cardiac notch
the region where the heart is not overlaid by lung tissue (on both R and L sides)
- apex is at the distal quarter of the 4th rib between sternum and CCJ
Aspirated materials (fluids, heavy solid particles) gravitate towards which lobes
right cranial and middle lobes
lighter airborne particles gravitate towards which lobe
accessory lobe
What are the borders of the auscultation triangle
• Cranial – caudal border of triceps brachii (along the humerus)
• Dorsal – epaxial muscles (near spine)
• Caudoventral – curved line from olecranon to intercostal space between ribs # 16 & 17 (end of rib cage)
General rule for pleurocentesis or thoracocentesis: (4)
• puncture the middle of an ics (avoid cranial & caudal branches of ventral intercostal vessels)
• dorsal to the ccj
• Ox and Horse @ 7th ics above the the ccj
• in the horse avoid the superficial thoracic “spur” vein.
Right vein azygos (3)
unpaired
right-dorsal surface of the aorta
drains into cranial vena cava
what species is the left vein azygos in?
ruminants only (left-dorsal surface of aorta into coronary sinus)
What is a lymph center (LC)?
a lymph node(s) that occur constantly in the same region of ALL species and drain in similar regions
4 main lymph centers of the thorax
Dorsal thoracic LC
Ventral thoracic LC
Mediastinal LC
Bronchial LC
Clinical significance of caudal mediastinal lymph node in ruminants
-very large, between aorta and esophagus
-if enlarged can press on esophagus and dorsal vagal trunk
- will cause difficultly swallowing, vagal indigestion, and bloat
4 thoracic lymphocenters in the dog
intercostal (5-6th space)
cranial mediastinal
tracheobronchial
sternal
(city dogs= darker lymph nodes due to carbon particles)
Why locate the sternal lymph node?
lymph from peritoneal cavity drains into sternal Ln (through diaphragm)
sternal ln drains into cranial mammary glands.
Tumor cells can reach the sternal lymph node through this passage
Why is T6 an anatomical landmark?
• The longus colli m arises from T6 vertebra
• The thoracic duct deviates from right to left @ T6
• On lateral radiographs, the carina shows up as a circular dark spot @ T6
• The tracheobronchial lymph nodes are near the carina, and can be identified in abnormal radiographs.
The thoracic duct…
A. Area draining to right lymphatic duct.
B. Area draining to thoracic duct. (~75% of the body)
In addition to lymphatic drainage, the thoracic duct transports fat absorbed from the digestive tract to venous circulation.
Because of this fat, the material within the thoracic duct is known as chyle.
should be avoided during surgery
What is a chylothorax and why is it a problem?
when lymph vessels are cut, the remain open for a while (no clotting factors). Will need medical or surgical intervention
location of the heart
middle mediastinum, partially left, attaches lowkey to the sternum
ICS 2 to 5(ox)6 (horse)
What are the 3 fibroserous layers of the pericardium
fibrous pericardium
parietal layer
visceral layer
mediastinal pleura connects to the _____ of the heart
fibrous pericardium
What is the cardiac tamponade
When the pericardial sac becomes filled with fluid
(can not expand and will compress the heart)
What is pericardiocentesis
inserting a needle from the right side along the 4-5th ICS between sternum and CCJ
relieves increased pressure in the cavity from a cardiac tamponade
base vs the apex of the heart
base is made by the 2 atrium
apex is made by the left ventricle
(right side is more cranial)
grooves of the heart
coronary groove (atria to ventricle)
2 interventricular grooves (interventricular septum, paraconal and subsinuosal)
intermediate groove (ruminants)
what are other names for the left and right side of the heart
left: auricular surface
right: atrial surface
What are the 2 septa in the heart
divide into right and left sides
interatrial septum
Interventricular septum
think PAM and what ICS they are associated with
Pulmonic valve = 3rd ICS
Aortic valve= 4th ICS
Mitral = 5th ICS
the heart feeds itself via
2 coronary arteries (R/L)
blood circulation pathway
Venous blood (venae cavae)
Right atrium
Tricuspid valve
Right ventricle
Pulmonic valve
Pulmonary trunk
Pulmonary arteries
Lungs →
Pulmonary veins
Left atrium
Mitral valve
Left ventricle
Aortic valve→Aorta→The body
