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Large Animal Anatomy Winter/Spring 2008 Structures for First Laboratory Exam Lab 3 and 4 – Thorax Horse: Bones: 1. Tuber coxae (“hooks”) 2. Number of ribs (18) 8 – sternal, 10 - asternal 3. Costal arch – formed by asternal ribs 9-16/17 4. Floating ribs – not attached to costal arch, last 1-2 ribs 5. Rib shape – oval 6. Costochondral joints – all are synchondrotic (synchondrosis is a cartilaginous joint) in horse as well as carnivores Muscles: 1. Cutaneous trunci 2. Cutaneous omobrachialis (partially continuous with cutaneous trunci) 3. Pectoral muscles a. Descending b. Transverse c. Ascending (deep) – connected to cutaneous trunci, border defined by superficial thoracic (spur) vein d. Subclavius (considered a division of transverse pectoral), found cranial to supraspinatus m. 4. Serratus ventralis thoracis 5. Latissimus dorsi 6. External abdominal oblique (Note direction of muscle fibers, as well as position of muscular versus aponeurotic portions) a. Originates on ribs 4/5-18 b. Lumbar part originates from costal arch and thoracolumbar fascia c. Extends to tuber coxae 7. Trapezius – thoracic part 8. Rhomboideus cervicis and thoracis 9. Scalenus (horse has middle and ventral parts only) 10. Intercostal muscles - internal (cranioventral) and external (caudoventral), note direction of muscle fibers 11. Serratus dorsalis cranialis and caudalis Nerves: 1. Phrenic nerve (from roots C5-7) 2. Vagus nerve a. Left and right recurrent laryngeal nerves b. Cardiac plexus c. Dorsal and ventral esophageal branches 3. Vagosympathetic trunk 4. Sympathetic trunk Vessels: 1. Superficial thoracic vein (spur vein) (clinical significance) – found at border between cutaneous trunci m. and ascending pectoral m. 2. Cephalic vein (in cephalic groove between descending pectoral m. and brachiocephalicus [cleidocephalicus] m.) 3. Right azygous vein only (also only azygous vein in dog) 4. Right subclavian artery (position of right recurrent laryngeal nerve) 5. Caudal and cranial vena cava Structures: 1. Scapular cartilage 2. Dorsoscapular ligament – part of thoracolumbar deep fascia extending from the withers ventrally to insert on the medial surface of the scapula, interdigitating as elastic laminae among muscle bundles of serratus ventralis (clinical significance) 3. Supraspinous bursa 4. Caudal deep cervical lymph nodes (at thoracic inlet, ventrolateral to trachea). Note left and right recurrent laryngeal nerves related to these lymph nodes. 5. Ligamentum flava abdominis – modified deep fascia attached to aponeurosis of external abdominal oblique m. 6. Cupula plurae – apexes of left and right pleural sacs (clinical significance) a. Right side – forms 2 diverticulae dorsal and ventral to cranial vena cava; extends about 3 cm in front of first rib. b. Left cupula ends at level of first rib. 7. Thoracic thymus (in cranial mediastinal space) 8. Lungs (no distinct lobation or lobulation) (be able to identify in situ as well as when they are removed from the body cavity) a. Cardiac notches b. Pulmonary ligaments (from hilus to mediastinal pleura) c. Left lobes: cranial; caudal d. Right lobes: cranial; caudal; accessory (this lobe is medial to caudal lobe and encircles caudal vena cava and is located in the mediastinal recess). (Clinical significance of accessory lobe) e. Impressions: aortic (most dorsal), esophageal, diaphragmatic (on caudal lobe), cardiac and costal. f. Hilus (not covered with pleura) – contains: principal bronchus, pulmonary artery, pulmonary veins. g. Tracheo-bronchial lymph nodes 9. Mediastinal pleura (clinical significance), possibly fenestrated in horse 10. Thoracic esophagus - course, associated vagal branches 11. Thoracic trachea - level of bronchus entering lungs (approximately ICS 6/7) 12. Thoracic duct – course throughout thorax a. Has its own opening in diaphragm, dorsal to aortic hiatus[cow only] 13. Diaphragmatic openings: a. Aortic hiatus – between left and right crura of diaphragm; contains descending aorta, cisterni chili b. Esophageal hiatus - within right crus; contains esophagus, vagal nerve trunks c. Foramen vena cava – in tendinous center slightly to right; contains caudal vena cava 14. Liver (be able to ID in situ as well as when it is removed from the body cavity) (It is in the thorax section since it is important to ID this organ relative to the ribs and lungs) a. Coronary ligament b. Triangular ligament c. Cupula – extends to ICS 6/7; most cranial extent of diaphragm (uneven - more cranial extent right of midline due to larger right lobe of liver) d. Extent of coverage by ribs/lungs (basal border of lungs overlaps liver completely during inspiration) e. Position relative to diaphragm f. Lobes g. Impressions 15. Stomach – relative to ribs (ICS) (Clinical significance) 16. Spleen – relative to ribs (ICS) 17. Greater omentum – relative to ribs (ICS) 18. Heart (be able to ID in situ as well as when it is removed from the body cavity) a. Position relative to ribs (ICS) – extends from ICS 3-6 b. Sternopericardial ligament c. Paraconal groove - left side between left ventricle (caudal) and right ventricle (cranial) d. Subsinuosal groove - right side between left ventricle (caudal) and right ventricle (cranial) e. Pericardium, including layers: Pericardium (covered externally with pericardial mediastinal pleura) – parietal and visceral layers; pericardial cavity - between pericardium and epicardium of heart f. Conus arteriosus g. Ligamentum arteriosum (position of left recurrent laryngeal nerve) h. Coronary arteries: Right is predominant – gives off subsinuosal interventricular branch. i. Left and right ventricles, atria, and auricles j. Valves: Left and right AV, pulmonary, aortic (use windows if needed) k. Valves relative to ribs for auscultation (page 33 of syllabus) l. Aorta m. Pulmonary trunk n. Caudal and cranial vena cava Other: 1. Fold of the flank: at level of stifle, cutaneous trunci enclosed in a fold of skin. 2. Know 7 extrinsic muscles that attach pectoral leg to trunk (page 19, Dissection Guide) 3. Brachial plexus roots pierce middle scalenus m. 4. Know position of heart/valves relative to ICS a. Heart extends from ICS 3-6 b. Long head of triceps overlaps these ICS, making auscultation of heart more difficult than in cats and dogs. 5. Line of pleural reflection/diaphragmatic line of pleural reflection (costal pleura reflects to form diaphragmatic pleura); the space formed by this reflection is called the costo-diaphragmatic recess (extends from costal cartilage of rib 8/9 to middle of cranial border of last rib) (clinical significance) 6. Line of diaphragmatic attachment/line of costal attachment of the diaphragm (just ventral and parallel to line of pleural reflection) Goat: Bones: 1. Tuber coxae (“hooks”) 2. Number of ribs (13), 8 sternal, 5 asternal 3. Costal arch 4. Rib shape – flat, wider than in horses (therefore ICS narrower in the cow than in the horse) 5. Ribs of ruminants (ruminants only) have synovial joints (amphiarthroidal type), 2-10 in cow, 2-7 in small ruminants Muscles: 1. Cutaneous trunci 2. Cutaneous omobrachialis +/- connection with cutaneous trunci 3. Pectoral muscles a. Descending b. Transverse c. Ascending (deep) d. Subclavius – rudimentary, runs from manubrium to brachiocephalicus (level of clavicular intersection) 4. Serratus ventralis thoracis 5. Latissimus dorsi 6. External abdominal oblique (Note direction of muscle fibers, as well as position of muscular versus aponeurotic portions) 7. Trapezius – thoracic part 8. Rhomboideus cervicis and thoracis 9. Scalenus (cow and goat have 3 parts, sheep have middle and ventral parts only, Habel 1989) 10. Intercostal muscles (internal and external, note direction of muscle fibers) 11. Serratus dorsalis cranialis and caudalis Nerves: 1. Phrenic nerve (formed by branches of C5-7) 2. Vagus nerve a. Left and right recurrent laryngeal nerves (this section starts on bottom of page 28 in the Goat Dissection Guide) b. Cardiac branches c. Dorsal and ventral esophageal branches 3. Sympathetic trunk 4. Vagosympathetic trunk – (the ventral part is the vagus, and the dorsal part is the cervical part of the sympathetic trunk) 5. Please note that although the middle, cervical ganglion, cervicothoracic ganglion, and ansa subclavia are bolded in the Goat Dissection Guide, you are not responsible for these structures on the practical (bottom of page 26-bottom of page 28, these might be bonus questions). You should read this section in the Goat Dissection Guide (page 26-28) for the written part of the exam. You are responsible for the bottom of page 28 about the recurrent laryngeal nerves for the lab. Vessels: 1. Cephalic vein (in cephalic groove between descending pectoral m. and brachiocephalicus [cleidocephalicus] m.) 2. Left azygous vein (cow – usually left only); Note that the small ruminants can also have a well-formed right azygous vein in addition to the left azygous vein 3. Cephalic vein – in cephalic groove bordered by descending pectoral m. and cleidobrachialis m. 4. Right subclavian artery (position of right recurrent laryngeal nerve) 5. Caudal and cranial vena cava Structures: 1. Scapular cartilage 2. Dorsoscapular ligament – is not prominent in the ruminants (review this structure in the horse) 3. Caudal deep cervical lymph nodes (at thoracic inlet, ventrolateral to trachea) 4. Thoracic thymus (in cranial mediastinal space) 5. Diaphragmatic openings a. Aortic hiatus – between left and right crura of diaphragm; contains descending aorta, cisterna chili, azygous vein. b. Esophageal hiatus – within right crus, contains esophagus, ventral and dorsal branches of the vagus. c. Foramen vena cava – pierces tendinous center, to right of midline, contains caudal vena cava. d. Hiatus of thoracic duct – in ruminants only. This opening is found dorsal to the aortic hiatus, lateral to the right crus. 6. Lungs: a. Left lung – cranial (in ruminants this lobe is divided into a cranial and caudal part) and caudal lobes b. Right lung – cranial (in ruminants this lobe is divided into a cranial and caudal part), middle, accessory, caudal. Note that the right cranial lobe encroaches to the left of midline (ID right cranial lung from left side). Note the relationship of the accessory lobe to the caudal vena cava. c. Tracheal bronchus (pigs and ruminants) – separate bronchus off trachea, in ruminants, ventilates the right cranial lobe (both cranial and caudal parts of cranial lobe) d. Cardiac notches (divide both cranial lobes into cranial and caudal parts, larger on left) e. Polyhedral patterning of lungs: sheep – none, goat – on cranial lobes, large ruminants – present on all lobes. f. Pulmonary ligaments g. Tracheobronchial lymph nodes – left between aorta and left pulmonary artery, right cranial to origin of tracheal bronchus. 7. Caudal mediastinal lymph node (ruminants only, not found in horse) (clinical significance) 8. Cranial mediastinal lymph nodes – cranial to heart 9. Heart a. Location of heart valves in the goat relative to ribs (for auscultation): Left side – PAM=ICS 3 (1/2 way between shoulder joint and deltoid tuberosity), 4 (same level as P), 5 (level with shoulder joint); Right side – Right AV – ICS 3 (line between olecranon and shoulder joint); cow – see page 33 of syllabus. b. Pericardium (covered externally with pericardial mediastinal pleura) – parietal and visceral layers c. Pericardial cavity - between pericardium and epicardium of heart d. Sternopericardial ligament e. Ligamentum arteriosum (position of left recurrent laryngeal nerve) f. Coronary arteries – left is larger (more extensive) in ruminant s and dogs, and gives off subsinuosal interventricular branch as well as the paraconal branch. g. Great cardiac vein (not in horses) – in intermediate groove of left ventricle (between paraconal and subsinuosal interventricular grooves) h. Paraconal interventricular groove – on left side between left ventricle (caudal) and right ventricle (cranial) i. Subsinuosal interventricular groove – on right side between left ventricle (caudal) and right ventricle (cranial). Coronary sinus is located dorsal to this groove. j. Conus arteriosus k. Pulmonary trunk l. Aorta m. Left and right ventricles, atria, and auricles n. Valves: Left and right AV, pulmonary, aortic (use windows if needed) o. Os cordia (cow only) – calcification of fibrous annulus surrounding the aortic valve p. Caudal and cranial vena cava 10. Liver (be able to ID in situ as well as when it is removed from the body cavity) (It is in the thorax section since it is important to ID this organ relative to the ribs and lungs) a. Coronary ligament b. Triangular ligament c. Extent of coverage by ribs/position within chest/abdominal cavity d. Position relative to diaphragm e. Lobes f. Impressions Other: 1. Line of pleural reflection - from rib ICS 8 - rib 13 (also called diaphragmatic line of pleural reflection) (Clinical significance) 2. Costo-diaphragmatic recess – recess/area formed where the costal pleura reflects to cover the diaphragm (now called the diaphragmatic pleura). During inspiration, the basal border of the lungs can enter this space (thus the space is “obliterated”). 3. Line of diaphragmatic attachment (just ventral and parallel to line of pleural reflection) 4. Structures found in the mediastinal space: thoracic part of thymus, mediastinal lymph nodes, thoracic aorta, trachea, vagus (including cardiac branches and esophageal branches), and phrenic nerve (right phrenic follows caudal vena cava into pleural fold – plica vena cava). 5. Fold of the flank: at level of stifle, cutaneous trunci enclosed in a fold of skin.
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