Thoracic Wall Flashcards
how can the body be divided
into 3 internal cavities
- thoracic
- abdominal
- pelvic
where does the thoracic cavity extend
from the thoracic inlet cranially to the diaphragm caudally
enclosed by bones of ribcage
what are the boundaries of the thoracic cavity
dorsal: thoracic vertebrae
ventral: sternum
cranial: thoracic inlet
caudal: diaphragm
what does it mean that the thoracic cavity is laterally compressed
its greatest dimension is in a dorsoventral direction –> deep and narrow
how does the shape of the thoracic cavity vary in breeds of dogs
some breeds like the deerhound have narrow thoracic cavities
bulldog –> barrel chested
where does the abdominal cavity run
from diaphragm cranially to the pelvic inlet caudally
dorsal roof: lumbar vertebrae and wall is composed entirely of muscle
where does the pelvic cavity run
through the pelvis
passing ventral to sacrum
extends from pelvic inelt cranially to the pelvic diaphragm or perinuem caudally
what are the functions of the thoracic and abdominal walls
support and protection for the vital organs (in thorax –> heart, lungs and major blood vessels such as aorta. in abdomen –> liver, GI tract, urinary system)
respiration (abdominal wall muscles have attachments along the caudal aspect of ribcage and therefore have an influence on its movement)
what are the body wall components
1. skin
2. cutaneous trunci muscle (closely adhered to it, twitching the skin –> present dorsally and laterally like a blanket but does not extend to midline, not present ventrally)
3. superficial fasci–> composed of loose CT and fat (glue that holds the skin and cutaneous trunci muscle onto underlying structures of trunk)
4. deep fascia & muscle: various muscles associated with thoracic and abdominal walls –> covered by and enclosed within layers of fibrous tissues
what are the thorax components
deep to the fascia and muscles
4. ribcage & intercostal muscles
5. pleura: fine layer of cells called the pleura that lines the thoracic cavity and encases all of its components
what are the abdominal wall components
6. peritoneum: fine layer of cells lining the cavity and encasing its contents –> adherent to inner surface of abdominal wall muscles
what are the components of the ribcage
13 thoracic vertebrae
13 pairs of ribs
12 intercostal spaces
8 sternebrae = sternum
ribs articulate with vertebrae and sternum
what is the dorsal roof of the ribcage composed of
13 thoracic vertebrae
what are the lateral walls of the ribcage composed of
13 pairs of ribs
what are the spaces between adjacent ribs called
intercostal spaces –> 12 of them on each side of the dog numbered from cranial to caudal
(1st intercostal space = is caudal to 1st rib and so on)
what is the ventral floor of the ribcage formed by
sternum and in the dog made up from 8 individual bones called sternebrae
where do the ribs articulate
articulate with vertebral column dorsally and the sternum ventrally
what is the proximal 2/3 and distal 1/3 component of each rib
proximal 2/3: bone
distal 1/3: cartilage –> costal cartilage
what is the boundary between the bone and costal cartilage called
costochondral junction
how do ribs articulate
the proximal end of the rib has a rounded head for articulation with the relevant vertebrae
short neck with a small boney bump or tuberculum for articulation with transverse process of relevant vertebra
the rest of the bone is referred to as the body of the rib
what do the distal end of the costal cartilages of ribs 1-9 articulate with
intersternebral cartilages
located between the adjacent sternebrae in the sternum
what do the costal cartilages of ribs 10-12 run together to form
the costal arch which helps contribute to the flexibility of the ribcage
what is the costal cartilage of rib 13 associated with
not associated with anything –> floating rib
palpable in dog
what does the head of ribs 1-10 articulate with
head articulates with:
cranial costal fovea of thoracic vertebrae of same number
caudal costal fovea of thoracic vertebra immediately cranial to it (head of rib 5 articulates with cranial costal fovea of the 5th thoracic vertebra and caudal costal fovea of the 4th thoracic vertebra)
what are each components of the rib
proximal end = bone
head = blue
tuberculum = light blue
body
distal end = cartilage
costal cartilage
what does the tuberculum of ribs 1-10 articulate with
transverse process of the thoracic vertebra of same number
what does the head of the 1st rib articulate with
T1 and also C7 (last cervical vertebra –> has a pair of caudal costal fovea to accomodate this)
what do the head and the tuberculum of ribs 11-13 articulate with
the head articulates only with thoracic vertebra of same number and no longer bridges over intervertebral disc space –> movement is possible between adjacent vertebra towards the caudal part of the thoracic region and the thoracolumbar junction
what are the ligaments that hold the ribs in place
- intercapital ligament
- costo-transverse ligament
- radiate ligament
where does the intercapital ligament run and what does it merge with
runs between the heads of each pair of corresponding right and left ribs
runs over the dorsal surface of the intervertebral disc space and merges with
- fibres of dorsal longitudinal ligament
- annulus fibrosis of intervertebral disc
what does the intercapital ligament support
supports intervertebral disc
stabilizes the ribs
reduces chance of contents of the intervertebral disc space moving dorsally into the vertebral canal
what is the intercapital ligament associated with
ribs 1-10
why is the intercapital ligament not present in ribs 11-13
the vertebral body of corresponding vertebra and don’t span the intervertebral disc space so this ligament is absent
what is the function of the costo-transverse ligament
the tuberculum of each rib articulates with the short transverse process of the corresponding vertebra and is held in place by this ligament
#2
what is the function of radiate ligament
head of the rib is held in place ventrally by this ligament
supports the joint capsule and merges with the fibres of annulus fibrosus of intervertebral disc sapce (yellow)
identify the costal ligaments
- intercapital ligament (red on diagram and red pin)
- costo-transverse ligament (pink on diagram and yellow pin)
- radiate ligament (yellow on diagram and green pin)
what gives the rib cage flexibility
presence of cartilage components of the ribcage and the flexibility possible at the articulations between the ribs and the thoracic vertebrae and sternum
how does the diaphragm attach
around the caudal border of the ribcage and the last sternebra –> known as xiphoid
how does inspiration occur
its an active process
diaphragm contracts and flattens and ribs are pulled laterally and cranially by accessory inspiratory muscles
increases the volume of the thoracic cavity and therefore sucks air into the resp system
how does expiration occur
passive process
diaphragm relaxes and becomes dome shaped –> ribcage collapses caudally and medially which decreases the volume of the thoracic cavity and forces air out of the resp system
what is the function of the internal intercostal muscles and what direction do they run in
fill each space completely from dorsal to ventral and have fibres that run in a cranio-ventral direction
what is the function of the external intercostal muscle
ensure that ribs move together during inspiration and expiration and function as single unit
inspiration is an active process –> most important during this component of the resp cycle
where do the external intercostal muscles run to and what direction are there fibres
run as far distally as the costo-chondral junction
fibres run in a caudo-ventral direction
what are these structures
pink: external intercostal muscles
yellow: internal intercostal muscles
what are the superficial thoracic wall muscles
- foreleg: extrinsic muscles of forelimb (associated with producing movement)
- latisimmus dorsi (caudo-dorsally)
- pectoral muscles (ventrally)
- external abdominal oblique muscles (caudo-ventral portion)
what is the function of the external abdominal oblique muscles and how do intercostal muscles assist
- support weight of abdominal contents
- its origin along the caudal ribs means that it is exerting a constant force on the ribs in a caudal direction –> assists with passive collapse of ribcage during expiration
- following strenous exercise –> active contraction assits with increasing resp rate (intercostal muscles ensure that whole ribcage moves together in a caudal direction to compress the thoracic cavity and produce an increase expiratory effort) –> responsible for abdominal effort or “heaving flanks” observed after exercise
what is the blood supply to the thoracic cavity and where do they run
intercostal vein, artery: each intercostal space is associated with an intercostal artery and vein
run down caudal aspect of the rib to the level of the costochondral junction –> branch to run down both sides of rib
ventrally the intercostal arteries communicate with internal thoracic artery that runs along the length of the ventral aspect of the thorax
which arteries need to be taken into consideration during surgical incisions
if making a surgical incision in the intercostal space –> aim for middle of space because of the intercostal vein and arteries
the internal thoracic artery may be encountered if incision extends far distally in the intercostal space
what is the nerve supply to the thoracic cavity
intercostal nerves
what is the function of the serratus ventralis muscle
located between the limb and trunk with origins along the cervical vertebrae and ribs –> insertion onto the dorsal border of the scapula
suspends the weight of the animal’s thorax between the forelimbs
if increasing resp rate –> major accessory inspirator muscle –> pulls ribs cranially and laterally
if an animal is demonstrating an increased inspiratory effort either due to disease or exercise –> they will stand with elbows abducted (away from midline)
what are the thoracic wall muscles
- foreleg
- latissimus dorsi muscle
- pectoral muscles
- external abdominal oblique muscle
- serratus ventralis muscle
what are these structures
- cutaneous trunci muscle
- superficial fascia
- deep fascia and muscle
- ribcage and intercostal muscle
- pleura
- peritoneum
what are the superficial supply of the body wall
- cranial superficial epigastric artery
- caudal superficial epigastric artery
