thoracic skeleton (ribs & sternum)

what are the 3 parts of the thoracic skeleton?

thoracic vertebrae

ribs & costal cartilages

sternum

features of the thorax

cranial small thoracic inlet

middle bony thorax

caudal wide thoracic outlet

features of the bony thorax

cranial thoracic cavity

caudal intra-thoracic abdominal cavity

features of thoracic inlet

manubrium & first thoracic vertebrae/pair of ribs

passageway for esophagus & trachea

passageway for arteries & veins to head, neck & forelimbs

features of thoracic outlet

xiphoid process, last thoracic vertebrae & pair of ribs, & costal arch

closed by diaphragm

features of the rib

paired structures of "ribbons of bone"

articulate with 2 successive vertebrae

bony dorsal part (head, tubercle, neck, body)

cartilaginous ventral part

costochondral junction

What is the costochondral junction?

end of the rib where the bony body meets the costal cartilage

how does a rib articulate with thoracic vertebrae?

head- articulates with the socket between the two adjacent vertebrae

tubercle- articulates with the articular surface of the caudal vertebrae

what structures create the socket for rib head articulation?

cranial costal fovea

caudal costal fovea

intervertebral disc

what is the costo-central joint?

synovial joint between rib head & body of adjacent thoracic vertebrae

allows adduction & abduction during respiration

changes width of thoracic cavity

what is the costo-transverse joint?

synovial joint between rib tubercle and transverse process of thoracic vertebrae

features of the intercapital ligament

attaches the non-articular part of rib heads to each other in a pair

passes through intervertebral foramen & floor of vertebral canal

runs below dorsal longitudinal ligament & spinal cord

features of a true (sternal) rib

articulate directly with sternum via costal cartilage

vertical synovial costo-sternal joint

forward & backward movement

(first 9 pairs or ribs in canine)

features of a false (asternal) rib

attaches indirectly to sternum via other ribs & costal cartilage

greater degree of adduction & abduction

(10-12th pairs of ribs in canine)

features of a floating rib

costal cartilage is not attached to the sternum

end freely in abdominal musculature

(last pair/13th of ribs in canine)

features of cranial end of ribcage

protect heart & lungs- flat rib body

free front limb movement- flat rib body

restricted rib movement- large distance between rib head & tubercle

stable muscle attachment

features of caudal end of ribcage

less rigidly anchored- indirectly attached to sternum

greater movement- small distance between rib head & tubercle

adduction & abduction at costo-central joints

what is the sternum?

median unpaired segmented bone that forms the thorax floor & allows some flexibility

what are sternebrae?

bony segments that make up the sternum united by intersternebral fibrocartilage joints

how does an avian sternum differ?

it is a single unsegmented bone for attachment of major flight muscles

what is the manubrium?

the first sternebra

articulates with the first pair of ribs

(palpable in canine)

what is the xiphoid process?

the last sternebra

HORSES

how many pairs of ribs?

how many sternal ribs?

how many asternal ribs?

how many sternebrae?

18

8

10

7

RUMINANTS

how many pairs of ribs?

how many sternal ribs?

how many asternal ribs?

how many sternebrae?

18

8

5

7

PIGS

how many pairs of ribs?

how many sternal ribs?

how many asternal ribs?

how many sternebrae?

14

7

7

6

DOGS & CATS

how many pairs of ribs?

how many sternal ribs?

how many asternal ribs?

how many sternebrae?

13

9

4

8

what do the 2nd-9th ribs articulate with?

the intersternebral fibrocartilage between the sternebrae

what is the costal arch?

the costal cartilages of the 10-12th ribs uniting with each other

(palpable in canine)