Exam 2 (Lecture 2) - Muscles and Lungs

Question 1

What is the projection of pleura cranial to the first rib called? Is it on both sides in the large animal? What is the clinical significance of this?

Answer 1

• Cupulae pleurae
• ONLY on the RIGHT side in large animals
• If we have a deep penetrating wound on the base of the neck on the right side, we have to be considering the possibility that the thoracic cavity on the right side could have potentially been entered.

Question 2

Explain the costodiaphragmatic recess.

Answer 2

The lungs never completely fill the pleural cavity; so the costal pleura and diaphragmatic pleura are in contact in with each other in this region.

When the animal inhales and the lungs expand, this recess is where the caudal margin of the lungs move into .

Question 3

What is the costal mediastinal recess?

Answer 3

The ventral part of the pleural cavity; where the costal and mediastinal pleura are in contact with each other.

Question 4

What is the diaphragmatic line of pleural reflection?

Answer 4

It marks the caudal most extent of the pleural cavity; this is important because if we think about advancing a needle dorsal to this line, we will be entering the pleural cavity; ventral to this line, we will be entering the peritoneal cavity.

Question 5

Describe the diaphragmatic line of pleural reflection in the horse.

Answer 5

• Begins around the 8th/9th costal cartilage
• Terminates at the middle part of the last rib
• Cranial to caudal, the line is slowly moving away from the costal cartilage (gradually sweeping away)

Question 6

Describe the diaphragmatic line of pleural reflection in the ruminant.

Answer 6

• Begins at the 7th/8th costochondral junction
• Traverses the middle part of the 11th rib
• Terminates at the angle of the 13th rib
• Cranial to caudal, the line is moving away from the costal cartilage at a sharper angle than in the horse

Question 7

What are the boundaries for the area of auscultation in the horse?

Answer 7

• Cranial boundary = caudal margin of long head of triceps (5th rib/5th intercostal space)
• Dorsal boundary = caudal angle of the scapula to the tuber coxae
• Caudoventral boundary = Olecranon process to the dorsal part of the 16th rib

**The thin margin of lung over the diaphragm is not useful for auscultation

Question 8

What are the boundaries for the area of auscultation in the ruminant?

Answer 8

• Cranial boundary = caudal margin of long head of triceps
• Dorsal boundary = lateral to epaxial muscles
• Caudoventral boundary = Olecranon process to the dorsal part of the 11th rib

Question 9

How do the boundaries of the thoracic cavity, pleural cavity, and area of pulmonary auscultation compare?

Answer 9

The thoracic cavity is the largest area of the three
- the pleural cavity is smaller
- the area of pulmonary auscultation is smaller still

Question 10

Which species have fenestrated (delicate) mediastinum? What is the clinical significance of this?

Answer 10

1) Horse and carnivore
- RARE in sheep (sheep have mediastinum that isn’t as delicate as horse/carnivore, but not as strong as cattle, goats, and pigs; so good chance of disease being present in both sides)

2) A pneumothorax in the R pleural cavity can spread to the L pleural cavity

Question 11

Which species have non-fenestrated (strong) mediastinum?

Answer 11

Cattle, goats, and pigs

Question 12

What structures are present in the mediastinum?

Answer 12

1) Heart
2) Trachea
3) Esophagus
4) Great vessels
5) Thymus
6) Thoracic duct
7) Lymph nodes
8) Nerves

Question 13

What is the plica vena cava? What travels in the plica vena cava?

Answer 13

• Plica vena cava IS part of the mediastinum (its just a branch away from it)
• Caudal vena cava and right phrenic nerve travel in the plica vena cava

Question 14

What sits in the mediastinal recess?

Answer 14

The accessory lobe of the right lung

Question 15

Why don’t we see the cupulae pleurae on the left side of the body?

Answer 15

Because the mediastinum fuses with the left first rib cranially.

Question 16

What makes up the cervicothoracic ganglion?

Answer 16

The caudal cervical ganglion and first 2 thoracic ganglia.

Question 17

What is the nerve branch that loops around the subclavian artery? What is the area called where the two branches re-join?

Answer 17

1) Ansa subclavia

2) Middle cervical ganglion

Question 18

Discuss where the nerve courses from the middle cervical ganglion cranially toward the head.

Answer 18

The sympathetic trunk will join the vagus nerve to form the vagosympathetic trunk in the neck region.

Question 19

As you move caudally, what are the branches of the vagus nerve, and where does it begin branching?

Answer 19

1) Vagus nerve begins branching at the level of the base of the heart

2) The most ventral branch of the vagus nerve is the left recurrent laryngeal (courses around the ligamentum arteriosum) and then moves to a more medial orientation where it traverses back cranially to innervate the larynx.

3) After giving off the left recurrent laryngeal, the vagus gives off the dorsal and ventral vagal trunks (on both L and R sides)
- the R and L dorsal branches join together dorsal to the esophagus to form the dorsal vagal trunk
- the R and L ventral branches join together ventral to the esophagus to from the ventral vagal trunk
- dorsal vagal trunk is LARGER of the two trunks

Question 20

Which spinal segments is the phrenic nerve derived from?

Answer 20

C5, C6, and C7 spinal segments

Question 21

Where does the thoracic duct open up? (Side of the body and specific location).

Answer 21

1) Opens up on the left side of the body

2) In the cranial venous confluence (where the cranial and caudal vena cava come together).
- will shift to the right side at approximately the aortic arch; this shift along with the fact that there is no
branching, helps to indicate that it’s the thoracic duct when looking at it grossly.

Question 22

What are the groups of mediastinal lymph nodes and where are they found? Which species have which lymph nodes?

Answer 22

1) Cranial mediastinal lymph nodes (found in all species)
2) Middle mediastinal lymph nodes (horses and ruminants)
3) Caudal mediastinal lymph nodes (ruminants; typically have one large one with several smaller ones)

• Mediastinal lymph nodes are organized immediately around the esophagus (can be dorsal, ventral, or lateral)
• Found to the RIGHT of the aorta; will not see them on the left side

Question 23

What are the species differences in the left lung?

Answer 23

1) Carnivore, pig and ruminant all have divided left cranial lung lobes
- they have UNDIVIDED caudal lung lobes

2) Horse has undivided cranial and caudal lobes

Question 24

What are the species differences in the right lung?

Answer 24

1) Carnivore, pig, and ruminant have cranial, middle, caudal, and accessory right lung lobes
- the ruminant has a divided cranial lobe on the right as well

2) Horse does NOT have middle lung lobe

3) In the ruminant and the pig, the cranial right lung lobe is supplied by a tracheal bronchus
- this tracheal bronchus is cranial to the tracheal bifurcation

Question 25

What are the branching patterns of the trachea?

Answer 25

1) At the tracheal bifurcation, you have the principal bronchi (R and L side)

2) The principal bronchi give off R and L cranial lobar branches
- in species with divided cranial lobes, the cranial lobar branches give off 2 more branches to supply the
cranial and caudal parts of the cranial lobe

3) The left principle bronchus then gives off the caudal lobar bronchus that supplies the caudal lobe

4) The right principle bronchus gives off a middle lobar bronchus that supplies the middle lobe of the right lung

5) The right principle bronchus then gives off caudal and accessory lobar bronchi branches

Question 26

Describe where you find the tracheobronchial lymph nodes.

Answer 26

1) In species without a tracheal bronchus:
- Right and left tracheobronchial lymph nodes (cranial to tracheal bifurcation)
- Middle tracheobronchial lymph nodes (caudal to tracheal bifurcation)

2) In species with a tracheal bronchus:
- Same as above PLUS
- Cranial tracheobronchial lymph nodes (cranial to tracheal bronchus)