Thorax Flashcards
Limits of thoracic cavity
Dorsal - veterbral column
Ventral - sternum
Caudal - costal arch
Cranial - thoracic inlet, T1, manubrium (1st sternebrae)
Name the components of the ribs
Bony vertebral part Cartilaginous (costal) sterna part Costochondral junction Asternal ribs Sternal ribs Costal arch = border where of the rib cage where the asternal ribs fuse Floating rib
Name the articulations of the ribs
Thoracic vertebrae dorsally
Junction of two sternebrae ventrally
Both articulations comprise synovial joints
Movement is like a bucket handle
As ribs move cranially, they move laterally
Name the components of the sternum
Sternal ribs Manubrium Sternebrae Xipisternum Xiphoid cartilage (caudal to the sternum)
What is the inter capital ligament
2 fibular heads are attached by inter capital fusion
To keep them in that position and prevent disc protrusion
If nucleus purposes expands it will protrude through annulus fibrosis and affect spinal cord by prolapse
What are the roles of muscles during inspiration
Increase in volume of thoracic cavity, diaphragm has convex protection doming up, external intercostal muscles and minor muscled are involved
Role of muscles during expiration
Decrease in volume of thoracic cavity, elastic recoil of lungs, relaxation and re-doming of diaphragm, internal intercostrals, abdominal muscles contract to pus the viscera up for forced expiration, minor muscles bring ribs back to resting position
External intercostals
Most superficial, fibres run dorso-cranially to ventral-caudally same direction as EAO
Action of external intercostal
Longer lever arm allows greater movement
Leverage on rib B greater than rib A
Rib b moves forward relative to rib A
Net result is whole rib cage is levered cranially and laterally
Increase in volume of thoracic cavity
Allows inspiration
What are the components of internal intercostal
Deep, fibres run dorso-caudally to ventral-cranially
Action of internal intercostal
Longer lever arm allows greater movement Leverage on rib A greater than rib B Rib A moves backwards relative to rib B Net result is whole rib cage levered caudally and medially Decreases volume of thoracic cavity Expiration
Components diaphragm
Muscular partition between thoracic and abdominal cavities
Consists of muscular periphery and Y shaped tendinous centre
Name the components of the diaphragm
Lumbar = right and left crura originate from lumbar vertebrae 3 and 4 via strong tendons
Costal = originates from medial surface of caudal ribs 8-13 in dogs
Sternal = dorsal surface of caudal sternum
All parts insert on the central tendon y shape centre
Passageways through the diaphragm
Oesophageal hiatus: oesophagus and vagus run through
Aortic hiatus: between 2 crura allows passage through diaphragm containing aorta, thoracic duct and azygous vein
Caval hiatus contains caudal vena cava
Clinical hiatal hernia
- stomach herniates through the oesophagus hiatus
- the stomach therefore protrudes out of the diaphragm
- more common in brachycephalic breeds or breeds hit by cars due to rapid increase in pressure in the thorax
