Thoracic Wall & Topographical Features Practical Flashcards
How many ribs does a dog have and how does this relate to the number of thoracic vertebrae present?
13 – same number of ribs as thoracic vertebrae
How many ribs does a horse, cow and cat have and how does this relate to the number of thoracic vertebrae present?
18, 13, 13 – same number as thoracic vertebrae
Why is the distal end of each rib cartilage and not bone?
To allow flexibility so the ribcage can expand and contract during respiration
Which structure attaches around the costal arch?
Diaphragm
How many intercostal spaces are there in the dog? What occupies these spaces in life?
- Intercostal muscles.
What important structures pass through the thoracic inlet in life?
Oespohagus, trachea, major blood vessels
What are the functions of the thoracic wall?
Respiration, protection & support of thoracic structures, muscle attachment
Does every pair of ribs have an intercapital ligament?
No – present ribs 1-10 only.
Which other ligament is the intercapital ligament very closely associated with?
Closely associated with the dorsal longitudinal ligament of the vertebral column.
Which vertebra(e ) does rib 5 articulate with?
Body articulates with body of T4 and T5 and tuberculum articulates with T5
Which vertebra(e ) does rib 11 articulate with?
T11 only
What is the function of the latissimus dorsi muscle and where does it get its nerve supply from?
Forelimb retractor and shoulder flexor. Nerve supply from brachial plexus
What is the main function of the pectoral muscles and where do they get their nerve supply from?
Forelimb adductor. Nerve supply from brachial plexus
What is the function of the external abdominal oblique muscle in relation to the thorax? Briefly explain the mechanism that results in this. By looking at an animal, how would you be able to tell that the external abdominal muscle was functioning in this way?
Accessory expirator muscle. Contraction results in the ribcage being pulled in a caudo-ventral direction which compresses the thoracic cavity / reduces the intrathoracic volume therefore helps force air from the lungs.
Increased movement of the abdominal wall / increased abdominal effort during respiration / heaving flanks
What is the function of the serratus ventralis muscle in relation to the thorax? Briefly explain the mechanism that results in this. By looking at an animal, how would you be able to tell that the serratus ventralis muscle was functioning in this way?
Accessory inspirator muscle. Contraction results in the ribcage being pulled in a cranio-dorsal direction which expands the thoracic cavity / increases the intrathoracic volume therefore helps draw air into the lungs.
Elbows slightly abducted to allow muscle to function in this way
What other functions does the serratus ventralis muscle fulfil?
Support of the trunk between the forelimbs (part of stay apparatus in horse)
Forelimb protractor and retractor
Lateral flexion of the neck region
What is the function of the intercostal muscles?
Link the movement of each rib to its neighbour so the ribcage functions as a single unit during inspiration and expiration
What are the main functions of the abdominal wall?
Support and protection of the abdominal contents; Abdominal press ; Movement of the trunk ;
Expiration
How would you describe the fibre direction of each of these muscles?
EAO – caudoventral ; IAO – cranioventral ; TA – dorsoventral ; RA - craniocaudal
What structures form the inguinal canal and where are they located ?
Superficial inguinal ring – slit in caudoventral region of aponeurosis of external abdominal oblique muscle
Deep inguinal ring – opening at caudoventral aspect of aponeurosis of internal abdominal oblique muscle
How does the sex of the animal influence what structures run through the inguinal opening?
Both sexes - External pudendal artery and vein; Genitofemoral nerve
Bitch – vaginal process
Dog – cremaster muscle, testicular artery and vein, spermatic cord
What are the cranial and caudal attachments of the linea alba?
Cranial attachment – sternum (last sternebra = xiphoid)
Caudal attachment –pelvis (pubic bone)
What are the layers that you would incise down through when making a surgical incision through the lateral aspect of the thoracic wall?
Skin, Cutaneous trunci muscle, superficial fascia & fat, muscle surrounded by deep fascia (which muscles depends on where incision is being made), intercostal muscles, pleura
Where is relation to the ribs would you make your incision and why?
Down the middle of the intercostal space to avoid the blood and nerve supply that run down the caudal and then both aspects of the ribs
What are the layers that you would incise down through when making a surgical incision through the ventral aspect of the abdominal wall? Which species would you routinely employ this approach with
Skin, superficial fascia & fat, (tunica flava abdominus – horse), linea alba, peritoneum.
Dogs, horses, cats
What are the layers that you would incise down through when making a surgical incision through the lateral aspect of the abdominal wall?
Skin, superficial fascia & fat, (tunica flava abdominus – cow), muscle surrounded by deep fascia (external abdominal oblique, internal abdominal oblique, transverse abdominis) , peritoneum
Cows and cats
Which specific rib has been labelled?
3rd rib
Which specific intercostal space has been labelled?
7th intercostal space
Cartilage should not be well visualised on radiographs yet some of the costal cartilages are visible on this radiograph – why do you think this is the case? Is this normal in dogs?
The costal cartilages become increasingly mineralised as the dog ages and therefore become visible on radiographs – this is therefore a normal finding
What structures form the thoracic inlet?
T1, 1st pair of ribs+ manubrium
Which ribs contribute to the costal arch in the dog? Where do the other ribs attach?
T10-12 form costal arch. T1-9 attach to sternum. T13 is ‘floating’