Pleural Membranes, Reflections & Recesses & Mediastinum

Question 1

how is the mediastinum divided

Answer 1

subdivided into cranial, middle and caudal

Question 2

which mediastinum contains the heart

Answer 2

middle mediastinum

Question 3

what are the structures

Answer 3

Question 4

what is the plica vena cava

Answer 4

the caudal vena cava runs outside the mediastinum –> burrows between the caudal lobe of the right lung and the accessory lobe –> it has its own reflection of the pleura called the plica vena cavae (covering and supporting the caudal vena cava)

Question 5

what is the pericardium

Answer 5

serous sac surrounding the heart

Question 6

what are the structures associated with the cranial mediastinum

Answer 6

esophagus, thoracic duct, branches of aorta, thymus, trachea, cranial vena cava

Question 7

where is the thymus found

Answer 7

ventral part of the cranial mediastinum

Question 8

what are the structures in the cranial mediastinum

Answer 8

Question 9

what structures are associated with the middle mediastinum

Answer 9

thoracic duct, aorta, esophagus, azygos vein, pulmonary trunk, principle bronchi, heart, pericardium

Question 10

what are the structures

Answer 10

Question 11

what comprises the largest part of the middle mediastinum

Answer 11

heart within the pericardium

Question 12

what are the structures associated with the caudal mediastinum

Answer 12

the liver projects cranially up under the diaphragm

Question 13

what occurs to the plica vena cava in the caudal mediastinum

Answer 13

plica vena cava-parietal pleura of right sac is reflected over the caudal vena cava –> forms the mediastinal recess, the accessory lobe of the right lung sits in this recess

Question 14

what are the structures of the caudal mediastinum

Answer 14

Question 15

what does the visceral pleura form

Answer 15

the pulmonary ligament

Question 16

how does the pulmonary ligament form

Answer 16

reflection of the visceral pleura at the medial surface of each lung as it continues onto the mediastinum

forms the pulmonary ligament which attaches caudal lobe of each lung to the diaphragm

Question 17

what is the pleural reflection

Answer 17

line or curvature that occurs when a fold is made so that the pleura can change direction

Question 18

what and where is the costomediastinal recess

Answer 18

where the costal and mediastinal (parietal) pleura meet ventrally

ventral border of the lung moves into this during inspiration

Question 19

what is this structure

Answer 19

Question 20

what is the blue shaded area

Answer 20

costal/diaphragmatic pleura

Question 21

what is the costodiaphragmatic reccess

Answer 21

parietal pleura

basal border of lung moves in and out of this recess

costodiaphragmatic line of pleura reflection is the most caudal extent of this recess

Question 22

what is the pleural cupula

Answer 22

parietal pleura recess

reflection of costal pleura and mediastinal pleura

projects beyond first rib –> apex of each lung moves into this space during inspiration

vulnerable to trauma

Question 23

what are the parietal pleura regions

Answer 23

costomediastinal recess

costodiaphragmatic recess

pleural cupula

Question 24

what are these structures

Answer 24

Question 25

what are these structures

Answer 25

Question 26

what is the clinical importance of the costodiaphragmatic line (CDL) of pleural reflection

Answer 26

in horses and dogs the CDL follows the curve of the costal arch but is about a hands breadth more cranial and dorsal

in the bovine the line is placed more cranial and dorsal to the costal arch than in other species

Question 28

what are these structures

Answer 28

extent of the peritoneal cavity that is in direct contact with the thoracic wall

implications for surgery

Question 29

what are anatomical obstacles to percussion and ausuculation of the lungs

Answer 29

1. cranial boundary: caudal edge of the triceps brachii muscle
2. dorsal boundary: runs parallel to the vertebral column but is restricted by epaxial muscles –> horse and bovine: line from the tuber coxae to the caudal angle of the scapula
3. caudoventral boundary: corresponds to basal border of the lung at the end of expiration. Line from the 5th costochondral junction to the dorsal end of the 2nd last rib. Cranially ends near the olecranon process in the standing animal

Question 30

what is the minimum area for ausculation and percussion of the lungs

Answer 30

area of contact between the lung and thoracic wall at the end of expiration

Question 31

what occurs to the minimum area in the diseased state

Answer 31

decreases if the lung partially collapsed (pneumothorax or pleural effusion)

increases if the lung becomes enlarged (alveolar emphysema)

Question 32

what influences the min area for asuculation and percussion

Answer 32

variations in rib # and conformation of the thorax

large in horse, small in bovine, intermediate in dog and pig