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Shoulder Region and Thorax Part 1

Gross Anatomy IIPages17-20

Lec # 301-18-07

2007

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ANNOUNCEMENTS

2. If not already done, skin the thoracic wall and remaining portion of the shoulder as described on page 17 and in figure 2-1 of the lab guide. Always be careful around the rope in the neck, and be sure to keep the ligamentum nuchae intact to prevent the horse from tearing loose and falling.

3. In Monday’s lab (Jan 22nd pages 20-22) Be sure to identify the nerves of the brachial plexus on page 22, and leave the limb on until after the lab quiz. These nerves are potential candidates for the # 2 Lab quiz.

4. After lab quiz # 2 (on Monday) complete the removal of the forelimb, bag it, identify it and place it on the cart for your wing.

1. A reminder, we will split the heads on Thursday, January 25, 2007.

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ANNOUNCEMENTS con’t

5. It is probably easier to initially identify the dorsoscapular ligament if you will apply medial traction to the distal portion of the thoracic limb as you scrape off the rhomboideus muscle. Then just deep to the rhomboideus muscle (especially the thoracic portion) you will see the yellow dorsoscapular ligament, a structure unique to the horse, and important in drainage patterns for fistulous withers. After you transect the dorsoscapular ligament, in the process of transecting the origin of the serratus ventralis, the ligament will be mainly visible as laminae passing through the serratus ventralis. Consider the dorsoscapular ligament to be in bold print.

6. Be sure to complete the last paragraph of the left column on page 20 of the lab guide as the last portion of today’s assignment. This will prepare you to begin on page 20 (Thoracic Wall) at the top of the right column tomorrow.

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Extrinsic Muscles of the Forelimb

• Extrinsic muscles of the forelimb: Syssarcosis– Brachiocephalicus– Omotransversarius– Omohyoideus (+/-)– Trapezius– Rhomboideus– Serratus Ventralis– Latissimus Dorsi– Pectorals

• Pectoralis Descendens (cranial superficial pectoral)• Transverse Pectoral (caudal superficial pectoral)• Subclavius (cranial deep pectoral)• Pectoralis Ascendens (caudal deep pectoral)

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Review Question

• Name two extrinsic muscles of the forelimb found in the horse that are not found in the dog.

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PI124

Extrinsic Muscles of the Forelimb (See next Slide for

Pectoral Muscles)

PII124

Omohyoideus (Not Pictured)

9 Cleidomastoideus10 Omotransversarius

5&5’ Trapezius (Cervical & Thoracic)

3 Rhomboideus (Cervical & Thoracic) Not pictured

7 Latissimus Dorsi

6&6’ Serratus Ventralis (Cervical & Thoracic)

Lateral View

9&10 Brachiocephalicus

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PI124

PII124Pectoral Muscles,Pectoral Groove,“Heave Lines”

Transverse Pectoral (Caudal Superficial Pectoral) (Not Pictured)

Lateral View

11 Subclavius (Cranial Deep Pectoral)

23 Ascending Pectoral (Caudal Deep Pectoral)

Descending Pectoral (Cranial Superficial Pectoral) (Not Numbered)

Cephalic Vein in Lateral Pectoral Groove

Possible Heave Lines

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Clarification Question

• The “Heave Line” is formed by ______________ of the _________ muscle in response to “exercise” as result of RAO (Recurrent Airway Obstruction) COPD (Chronic Obstructive Pulmonary Disease) that requires especially forced expiration/inspiration.

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PI164

CleidomastoideusOmotransversarius

Omohyoideus (Not Pictured)Extrinsic Muscles of the Forelimb (See next Slide for

Pectoral Muscles)

Craniolateral View

Lateral Pectoral Groove, with Cephalic Vein

and on deep side the Deltoid br. of the Sup. Cer. A.

1 Brachiocephalicus

PI164

20 Rhomboideus (Cervical) & (Thoracic, Not Pictured))

3&4 Trapezius (Thoracic & Cervical )

11 Latissimus Dorsi

6 Serratus Ventralis (Cervical) & (Thoracic, Not Pictured)

Ext. Jugular Vein,

Cutaneous Colli

Removed

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Review Question

• What superficial vein passing over the brachiocephalicus muscle and dumping into the external jugular vein did you see in the dog that is not present in the horse?

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PI164

Pectoral Muscles

Ascending Pectoral (Caudal Deep Pectoral) (Not Pictured) Craniolateral View

14 Descending Pectoral (Cranial Superficial Pectoral)

16 Transverse Pectoral (Caudal Superficial Pectoral)

7 Subclavius (Cranial Deep Pectoral)

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Superficial Surface of the Thorax• Cutaneous Muscles

– Omobrachialis M.– Cutaneous Trunci M.

• Cutaneous Nerves: Branching patterns caudal to brachium vary– Lateral Thoracic N. to Omobrachialis and Cutaneous Trunci– Lateral Branches of at least T2 & T3 Intercostal Nerves– Intercostobrachial Nerve/Plexus, Cutaneous maybe Omobrachialis

• “Spur Vein” and Nerve– External Thoracic Vein, Lateral (external) Thoracic Nerve and probably

branches of the intercostobrachial plexus– In Popesko PI127, they have this vein mislabeled as cranial superficial

epigastric vein (#10) The picture is accurate however but the vein is the external thoracic vein that usually dumps into the axillary vein eventually

• Other Veins– Superficial Thoracic usually a branch of the thoracodorsal vein

– Cranial Superficial Epigastric, in the horse and especially in these ponies it

is very small so don’t spend much time looking for it

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PII127

Cutaneous Muscles, Cutaneous Nerves and Vein on the Lateral Surface of Trunk and Pectoral Limb

Appreciate the cutaneous nerves as you skin because many will not be obvious after this

1 Thoracic Dorsal Branches

2 Lateral branch of Iliohypogastric (L1)

3 Dorsal Branches of Lumbar N’s, (Cranial Clunial)

4,6 Cutaneous branches of Thoracic N’s (Lateral & Ventral from Intercostals and

Costoabdominal)5 Lateral branch of Ilioinguinal (L2)

8 Supraclavicular N. (C6)

7 Lateral Thoracic N. accompanies Ext. Thor. V. just caudal to brachium on deep

side of cutaneous trunci muscle

9 Cutaneous Trunci Muscle 10 External Thoracic V. (mislabeled in Popesko)

11 Omobrachialis Muscle

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Landmarks and Associated Structures:Be able to locate these Areas on the Palpation

Pony• Withers• Point of shoulder• Deltoid tuberosity• Scapular cartilage• Anticlinal vertebra

• End of spinal cord: In S2

• Caudal angle of scapula at 7th rib• Olecranon at 5th space

• C7, T18 (19), L6, S5, Ca15-21

• Ribs and Costal arch

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D489

T1L6

T16

DSW 2nd, 514

Palpable Landmarks & Areas to Appreciate

T16 Anticlinal Vertebra

Caudal Angle of Scapula at 7th Rib (+/-)

May have 19 ribs, if so may have only 5 lumbar vertebrae i.e. 5 without ribs

Withers

Costal Arch: Ribs 9-17 or 18, often no floating rib

Scapular Cartilage

S2 End of Spinal Cord

4 Point of Shoulder

5 Deltoid Tuberosity

6 Olecranon, proximal end at 5th space

10 6th Rib

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Review/Clarification Question

• The anticlinal vertebra in all the domestic animals regardless of their vertebral formula should usually be the _________________ vertebra.

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Anatomical Correlates, JAVMAmar01,00, pp722&723

Mid-cervical collapse of the trachea in a 2 year old thoroughbred filly via tracheal videoendoscopy. Present only during exercise. Left picture is standing at rest, Right picture is during exercise.

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Auscultation Triangle

• Cranial Border:– Caudal border of Triceps or Caudal Angle of scapula

to Olecranon (7th Rib to 5th space)

• Dorsal Border:– Lateral Edge of Epaxial Muscles or Caudal Angle of

Scapula to Tuber Coxae

• Caudoventral Border:– Olecranon through middle of 11th rib to proximal

end of 16th rib or Ventral end of 6th rib through middle of 11th rib to proximal end of 16th space

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D489T1L6

T16

Auscultation Triangle

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Review Question

• In the dog where did we auscultate for the puncta maxima of the left AV, Right AV, aortic and pulmonic valves ?

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Review and Preview• Ligamentum Nuchae

• Diseases of Bursas

• Scapular Cartilage

• Dorsal Scapular Ligament

• Regional Lymph Nodes

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Ligamentum Nuchae, D490B1

C7

FunicularLamellar

Ligamentum Nuchae & Bursae (Review)

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PI158

C6 Ventral Lamina

Scapular Cartilage

T7

Ligamentum Nuchae & Bursae (Review)

Identify “0”PI158

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SUPERFICIAL CERVICAL LN , S620

5”. Caudal deep cervical6. Superficial cervical6. Superficial cervical7. Nuchal8. Cranial mediastinal9. Axillary of 1st rib11. Proper axillary12. Cubital

Lymphatics of Shoulder and Forelimb

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Review Question

• The lymphatic duct that typically drains the left half of the head & neck, left forelimb, left half of the thorax and the caudal half of the body and pelvic limbs into the venous system is the _______________, and the lymphatic duct that typically drains the right half of the head, right half of the neck, right forelimb and right half of the thorax into the venous system is the ________________.