Extrinsic Muscles Of Thoracic Limb Flashcards
Extrinsic vs. Intrinsic
Extrinsic: situated outside, coming from or originating on the outside
Intrinsic: situated entirely within
Pectoral muscles (dog)
Superficial pectoral m.
-descending
-transverse
Deep pectoral m. (ascending)
Superficial pectoral m. (descending)
Origin: first sternebrae
Insertion: crest of the greater tubercle
Innervation: cranial pectoral nn.
Action:
-when not bearing weight, adduct limb
-bearing weight, prevent limb for being abducted
Superficial pectoral m. (transverse)
Origin: sternebrae 1-3 and fibrous raphe on ventral midline
Insertion: crest of the greater tubercle
Innervation: cranial pectoral nn.
Action:
-when not bearing weight, adduct limb
-bearing weight, prevent limb for being abducted
Deep pectoral m.
Origin: stern brae 1-8 & fibrous raphe on the ventral midline, deep abdominal fascia in the region of xiphoid cartilage
Intersection: lesser tubercle, greater tubercle & crest greater tubercle via aponeurosis, medial brachial fascia
innervation: caudal pectoral nn.
Actions:
When the limb is advanced and fixed - pull the truck cranially
When the limb is not bearing weight - draw the limb caudally
Adduct the limb
Support the truck - the humeral insertion is dorsal to the sternal origin
Feline pectoral muscles
Pectoantebrachialis
origin: manubrium
Intersection: superficial fascia of proximal end ante brachium (ulna)
Action: draws the arm medically (adducts)
Xiphihumeralis
origin: xiphoid process
intersection: tendon on proximal end humerus
action: same as deep pectoral
Brachiocephalicus m.
Composition:
1. cleidocephalicus
a. cleidocervicalis
b. cleidomastoideus
2. cleidobrachialis
3. clavicular intersection
Brachiocephalicus m.
1a. cleidocervicalis
origin: clavicular intersection
Insertion: mid-dorsal cervical
1b. cleidomastoideus
origin: clavicular intersection
intersection: mastoid process
innervation: accessory n. and ventral brs. of cervical spinal nn.
Action: advance the limb, extend the shoulder jt., draw neck/head to side
Sternocephalicus m. (neck muscle)
- sterno-occipitalis m.
- steromastoideus m.
origin: first sternebra (manubrium)
insertion: - sterno-occipitalis: nuchal crest of occipital nerve
- steromastoideus: mastoid process of temporal bone
Innervation: accessory n. and ventral brs. of cervical spine nn.
Action: draw head/neck to side
Sternohyoideus m. (neck muscle)
Origin: manubrium and first costal cartilage
Insertion: basihyoid bone
innervation: ventral brs. of cervical spinal nn.
Action: draw tongue/larynx caudally
Omotransversarius m.
Origin: distal end of scapular spine and acromion
insertion: transverse process first cervical vertebra (wing atlas), basioccipital bone near tympanic bulla cat
trapezius m.
origin:
1. T. cervicis - median raphe neck (C3-C7)
2 T. thoracis - supraspinous ligament
insertion: spine scapula
innervation: Accessory n. (XI)
action:
T. cervicis - draw scapula craniodorsally
T. thoracis - draw scapula caudodorsally
together - elevate and abduct the thoracic limb
Rhomboideus m.
Origin:
1. R. capitis - nuchal crest occipital bone (substantial cat)
2. R. cervicis - median raphe neck
3. R. thoracis - spinous processes T1-T7
Insertion: dorsal border and adjacent surface scapula
Innervation: ventral brs. cervical and thoracic spinal nn.
Latissimus dorsi m.
origin: thoracolumbar fascia from spinous processes T7-L7 (dog), T4-L6 in cat. Last 2-3 ribs
Insertion: teres major tuberosity and teres major tendon
Innervation: Thoracodoral n.
Action: draw limb caudally, flex shoulder jt.
Serratus ventralis m.
Origin:
cervicis - transverse processes of C2/C3-C7
thoracis - first 7-8 ribs in dog, first 9-10 ribs in cat
thoracis - first 7-8 ribs in dog and first 9-10, ventral to middle region
insertion: serrated face
innervation: ventral brs. of cervical spinal nn. and long thoracic n.
Action: support truck by slinging body between forelimbs, depress scapula
Cutaneous muscles - platysma m.
origin: mid-dorsal cervical raphe and skin
insertion: commissure (corner) lip
action: draws lips caudally
Cutaneous muscle - cutaneus trunci m.
origin: superficial gluteal fascia
insertion: superficial fascia of truck and skin
innervation: lateral thoracic n.
action: moves the skin
cutaneous muscle - preputial m.
origin: xiphoid cartilage
insertion: prepuce
action: draws the prepuce over glans penis after erection (pulls prepuce cranially)
CATS - pulls erected penis cranial direction from caudal perineal position
Thoracic limbs attachment to truck (synsarcosis)
attached via serratus ventralis and deep pectoral mm. (sling body between the forelimbs, main supporters of truck)
Transverse humeral retinaculum (ligament)
connective tissue structure located medially between greater tubercles of the humerus
keeps biceps brachii tendon in intertubercular (bicipital) groove
If tore or displaced - biceps tendon to displace medially
