Exam 2: Lecture 13: Horse Thoracic Cavity Flashcards by Matthew Irvin

What is different about the diaphragm in horses than in dogs?

-Diaphragm in horses is a very oblique muscle
-Diaphragm is between the very delicate lungs & the very healthy digestive organs (so the digestive organs could put pressure on the lungs)

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What part of the diaphragm is represented by “C” and what does it do?

-Costal parts
-Attached to the cartilages of the ribs

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What part of the diaphragm is represented by “S” and what does it do?

-Sternal part
-Dorsal surface of xiphoid cartilage

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What part of the diaphragm is represented by “L” and what does it do?

-Lumbar parts
-Right & left crura: lumbar vertebrae & ventral longitudinal ligament

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Where is the aortic hiatus located on the diaphragm?

-Between the two crura

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Where is the esophageal hiatus located on the diaphragm?

-Perforates the right crus near its junction with the central tendon

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Where is the cava foramen located on the diaphragm?

-Courses through central tendon toward the right side

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How is the mediastinum divided in horses?

-Divided into cranial and caudal mediastinum (both touch each other)

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What is important about the caudal mediastinum?

-It is fenestrated in horses

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What is this?

-Caudal mediastinum

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What is the cupula pleura?

-Cranial extend of the pleural cavity
-Extends cranial to the first rib, is larger on the right side

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What is the costodiaphragmatic recess?

-Space not occupied by lungs even when they are fully inflated

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What is the capacity (in liters) of the horse lungs?

-55 liters

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What are the lobes of the left and right lungs?

-Left lung = cranial & caudal
-Right lung = cranial, caudal & accessory

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What is indicated by the star (both blue arrows)?

-Cardiac notch of the right lung

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What is the hilus of the lung?

-Wedge-shaped region in the middle of each lung
-Where the main structures of the lung enter & exit (like bronchi, pulmonary arteries, veins, nerves, and lymphatic)

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What is indicated by the arrow (dashed blue lines)?

-Impression of the caudal vena cava

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What side is the accessory lobe on?

-Right lung
-Comes from the right side, but has a tendency to lay on the left if we draw a line dividing the lungs in half

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What is important about the cardiac notch on the left lung?

-It is much larger than the right
-Takes up 3 intercostal spaces (3rd, 4th, 5th)
-(b/c apex of the heart is more oriented on the left)

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What is different about the equine trachea compared to dogs?

-Tracheal muscles are attached internally (to the internal walls of the trachea)

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Where is the carina located?

-Located at the level of T4-T5

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What is the sympathetic effect on the trachea?

-Relax everything to make it more expanded

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What is indicated by the yellow arrow?

-Pulmonary ligament

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What are the borders of the lungs?

-Dorsal region of the 16th rib
-Middle of the 11th rib
-Costochondral junction of the 6th rib

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What are the borders to auscultate the lungs in a horse? (Where do you want to put your stethoscope)

-Caudal angle of scapula -Dorsal end of the 16th rib -Point of elbow (olecranon)

How much does an equine heart weigh?

-Around 0.7% of the horse weight -Average adult horse has a 3.6 kg (7.9 lb) heart

The average pulse is _____ bpm in a mature horse, but it can reach more than _____ bpm during maximum exertion

-Pulse is 28-45 bpm, can each more than 250 bpm

The left face of the heart is also called the

-Auricular face

The right face of the heart is also called the

-Atrial face

Which side of the heart?

-Auricular face (left)

Which side of the heart?

-Atrial face (right)

99% of venous blood that is returning through the heart goes through what structure?

-Coronary sinus

What is an important structure of the heart that should be checked during necropsy?

-Fossa ovalis

What artery of the heart is much larger in horses than in dogs?

-Right coronary artery

What is the top arrow indicating?

-Coronary sinus

What is the bottom arrow indicating?

-Great cardiac vein

What is indicated by the arrow on the left?

-Coronary sinus

What is indicated by the pink circle?

-The opening of the coronary sinus into the right atrium

What is indicated by the arrow on the right?

-Middle cardiac vein

What does the middle cardiac vein join?

-Joins coronary sinus to open into the right atrium

Where would you auscultate the pulmonary valve?

-Left side, 3rd or 4th intercostal space, craniodorsal to the olecranon

Where would you auscultate the aortic valve?

-Left side, 4th intercostal space, ventral to the shoulder joint

Where would you auscultate the left atrioventricular valve?

-Left side, 5th intercostal space, caudodorsal to the olecranon

Where would you auscultate the right atrioventricular valve?

-Right side, 4th intercostal space, caudodorsal to the olecranon

What is different between horses and dogs when talking about the branching of the aortic arch?

-Horses only have one big branch (the brachiocephalic trunk)

What is indicated by the blue star?

-Brachiocephalic trunk

What is indicated by the blue star?

-Left subclavian a.

What is indicated by the blue star?

-Right subclavian a.

What is indicated by the blue star?

-Bicarotid trunk *Another difference between horses than dogs (this is not in dogs)*

What is indicated by the blue star?

-Left common carotid a.

What is indicated by the blue star?

-Right common carotid a.

What is the first branch off the left subclavian a?

-Costocervical trunk

What is the artery indicated by the star?

-Costocervial trunk

What is important about the costocervical trunk?

-Will go up & provide branches to thoracic limb and to at least 4 intercostal arteries

What is the second branch off the left subclavian a?

-Deep cervical a.

What artery is indicated by the blue star?

-Deep cervical a.

Where does the deep cervical a. come form and where is it located?

-Comes from costocervical trunk on the right side subclavian a. on the **left side** -Runs at level of T1 and goes immediately deep & medial in the neck -> **very close to nuchal ligament**

What does the deep cervical a. supply?

-Courses to head to supply cervical structures & musculature in the caudal neck region

What artery and vein needs to be carefully avoided in small horses?

-Deep cervical a. & v.

What artery is indicated by the blue star?

-Vertebral a.

What is the third branch off the left subclavian a.?

-Vertebral a.

What artery courses cranially through the transverse foramen of cervical vertebrae and courses through the alar foramen & lateral vertebral foramen of the atlas and enters the vertebral canal?

-Vertebral a.

What artery and vein is shown here?

-Vertebral a. & v.

What artery lives in the area known as the jugular fossa and runs just past the thoracic inlet to the outside?

-Superficial cervical a.

What artery is indicated by the blue star?

-Superficial cervical a.

What does the superficial cervical a. supply?

-Supplies structures in the craniolateral shoulder region

What artery is indicated by the blue star?

-Internal thoracic a.

What are the branches of the internal thoracic a.?

-Ventral intercostal aa. (supply ventral part of thoracic wall) -Cranial epigastric a. (supplies ventral abdominal wall)

What artery is indicated by the blue star?

-Axillary a.

What artery is indicated by the blue arrow? (and what does it branch into?)

-Bronchoesophageal a. (branches into bronchial a. & esophageal a.)

What artery is indicated by the blue star?

-Descending thoracic aorta

What artery is indicated by the blue star?

-Dorsal intercostal aa.

What is different between the dog and cat venous branching near the cranial vena cava?

-Dog = both brachiocephalic veins join together to form the cranial vena cava -Horse = have bijugular trunk, then 2 subclavian vv., then cranial vena cava

What thorax view can you see veins?

-Right

What thorax view can you see arteries?

-Left

What vein is indicated by the blue star?

-Caudal vena cava

What vein is indicated by the blue star?

-Cranial vena cava

What vein is indicated by the blue star?

-Superficial cervical v.

What vein is indicated by the blue star?

-Vertebral v.

What vein is indicated by the blue star?

-Costocervical v.

What vein is indicated by the blue star?