Exam 2 (Lecture 1) - Thoracic Cavity Flashcards
What does the thoracic region correspond to?
Where the ribs are located.
Describe the shape of the vertebral bodies as we move cranially.
They are directed ventrally as we move cranially.
Describe the orientation of the spinous processes as we move cranially.
The spinous processes get longer as we move cranially.
Why do the spinous processes get longer as we move cranially?
There needs to be more surface area for epaxial muscle attachment and this orientation provides that surface area.
Does the thoracic limb cover any of the thoracic cavity?
Yes, a fair amount cranially.
What does the point of elbow (olecranon process) correspond to?
The 5th rib or 5th intercostal space.
In large animals, what is the muscle attachment called that attaches the thoracic limb to the body wall?
Muscles of synsarcosis.
What percentage of body weight is carried on the thoracic limb? Provide and example.
About 60% of their body weight is carried on the thoracic limb (and 40% on the pelvic limb).
If a cow weighs 1500 lbs, she’s carrying 900 lbs on her front end; or 450 pounds on each thoracic limb
What are the EXTRINSIC muscles of synsarcosis?
1) Trapezius cervicis
2) Trapezius thoracic
3) Omotransversarius
4) Cleidooccipitalis
5) Cleidomastoideus
6) Latissimus dorsi
What are the INTRINSIC muscles of synsarcosis?
1) Subclavius (largest in the pig and the horse; thin in cattle)
2) Pectoral muscles
- Ascending (deep) pectoral
- Superficial pectorals (transverse and descending)
3) Serratus ventralis cervicis
4) Serratus ventralis thoracis
5) Rhomboideus cervicis
6) Rhomboideus thoracis
What is the superficial vein on the thoracic cavity (caudal to the olecranon process) and what is its clinical significance?
1) In cattle, it’s called the superficial thoracic vein
2) In horses, it’s called the spur vein
3) We utilize it as a site for blood draws in horses (not so much in cattle)
Which INTRINSIC muscle of snysarcosis are the most significant in the attachment of the thoracic limb to the body wall?
1) Pectoral muscles
2) Serratus ventralis
What happens to the shape of the thoracic cavity as we move cranially?
It gets narrow (so, the thoracic cavity is triangular shaped)
What are the boundaries of the thoracic cavity?
1) Dorsal Boundary: thoracic vertebrae
2) Lateral Boundaries: ribs and costal cartilage (each pair of ribs will articulate with a different vertebrae)
3) Ventral Boundary: sternum
In the newborn animal, what is the sternum comprised of? Are any still visible in the adult?
1) Sternebrae (fuse to form the sternum)
2) Yes; in the adult we have the manubrium sterni and the xyphoid process of the sternum
What are true ribs?
True ribs are the sternal ribs; they join the coastal cartilage ventrally and is then connected to the sternum.
What are false ribs?
False ribs are the asternal ribs; the costal cartilage from multiple asternal ribs forms the costal arch (so the rib is connected to the costal arch, NOT the sternum).
How many cervical vertebrae are there?
7 in ALL species.
How many thoracic vertebrae/pairs of ribs do dogs and cats have?
13
How many thoracic vertebrae/pairs of ribs do cattle, sheep, and goats have?
13
How many thoracic vertebrae/pairs of ribs do pigs have?
14
How many thoracic vertebrae/pairs of ribs do horses have?
18
How many true ribs do dogs and cats have?
9
How many true ribs do cattle, sheep, and goats have?
8
How many true ribs do pigs have?
7
How many true ribs do horses have?
8
How do you figure out how many false ribs a species has?
Number of ribs - number of true ribs = number of false ribs
How do you figure out how many sternebrae a species has?
Number of true ribs - 1 = number of sternebrae
Describe the thoracic vertebrae.
Shorter vertebral body than the cervical vertebrae; spinous processes are also bigger than those one the cervical vertebrae.
Where does the head of the ribs articulate?
Cranial and caudal costal fovea of the thoracic vertebrae
Where does the tubercle of the ribs articulate?
Costal fovea of the transverse process.
What is unique about the mammillary process of the thoracic vertebrae?
Its location changes as we move from a cranial to caudal direction.
In the cranial region, it is associated with the transverse process; in the caudal region, it’s associated with the cranial articular surface.
What is the intervertebral foramen made up of? What passes through it?
1) Made up of cranial and caudal vertebral notches (caudal notch is the deeper of the two)
2) Spinal nerves, veins, and arteries pass through it
In the large animal, where is the tallest spinous process?
T3-T4; NOT on the first thoracic vertebrae like in the carnivore
**This is AKA the withers
Which direction do the internal intercostal muscles run?
Caudodorsally
Which direction do the external intercostal muscles run?
Caudoventrally
In domestic mammals, where does the cranial projection of the diaphragm project to?
6th rib/6th intercostal space
What is the term for the part of the abdominal cavity that’s in the thoracic region?
Intrathoracic part of the abdominal cavity
Discuss the crura of the diaphragm.
- Right crus is larger than the left crus (b/c right pleural cavity is larger than the left)
- Both right and left crura take their origin from the ventral aspect of the 3rd and 4th lumbar vertebrae (L3 and L4); that’s why this is the lumbar part of the diaphragm.
What lies between the right and left crura? What passes through here?
- Hiatus aorticus
- Thoracic aorta, thoracic duct and azygous vein(s)
Which hiatus is ventral to the hiatus aorticus? What passes through it?
- Esophageal hiatus
- Esophagus and supporting vasculature
- the vagus nerve also passes through here from the thoracic to the abdominal region
What passes through the caval foramen?
Only the caudal vena cava
What are the lumbosacral arches?
- Small area dorsally where the diaphragm doesn’t contact the body wall (R and L sides)
- The pleura on the thoracic side and the peritoneum on the peritoneal side reflect here; there is a little bit of connective tissue between the two serosal layers.
- This area is where we find the sympathetic innervation to the abdominal viscera
- sympathetic trunk
- splanchnic nerves
What are the boundaries of the thoracic inlet?
- Dorsally: T1
- Ventrally: Manubrium sterni
- Laterally: First pair of ribs
** Completely rigid/bony boundary, so anything that can cause swelling of any of the structures of the thoracic inlet are going to further occlude the already narrow inlet. (Ex: swelling of lymph nodes in this area can impinge and close off the trachea.
How big is the thoracic inlet?
In a QH, it is about 10 cm wide by 20 cm tall. (Very small)
What structures are present in the thoracic inlet?
1) Trachea
2) Esophagus
3) Lymph nodes
4) Thyroid gland (pig)
5) Vago-sympathetic trunk
6) Phrenic nerve
7) Jugular vein
8) Recurrent laryngeal nerve
9) Common carotid artery
10) Subclavian artery and vein
11) Cupulae pleurae
12) Thymus (in young animal)
13) Thoracic duct
14) Longus colli muscle
What is the space in between the visceral and parietal pleura called?
Pleural cavity
