Download Anatomy I: Lesson 10

Anatomy I: Lesson 10
Myologia – Part I
Objective: Students will examine the muscles of a canine
in order to identify the musculature of the body.
Practical Tasks

1) m. latissimus dorsi, m. trapezius, m.
rhomboideus, m. serratus ventralis, mm.
pectorales

2) extensors of the shoulder

3) flexors of the shoulder

4) extensors of the elbow

5) flexors of the elbow
Practical Task 1


M. latissimus dorsi
Origin: superficial layer of thoracolumbar
fascia (from spinous processes of the last 7-8
thoracic and lumbar vertebrae); also
muscular attachment proximally to the last
few ribs

Insertion: on teres major tuberosity
(together with m. teres major)

Action: draws free limb caudally; together
with m. teres major flexes shoulder
Musculature of the Pectoral Girdle
Extrinsic = Superficial Musculature
Origin
by aponeurois from the Fascia
thoracolumbalis
1) M. latissimus dorsi : one of the
largest muscles of the body, flat,
almost triangular in shape, on dorsal
and lateral side of thorax.
Insertion
Tuberositas teres major resp.
Crista tuberositas minoris (in
Ca.) of the humerus
Innervated by
N. thoracodorsalis and Nn.
pectorales caudales
Actions
antagonist to the M. brachiocephalicus.
It retracts the free limb when shoulder
is flexed; prevents arching of vertebral
column when pulling a load; it also
draws the trunk
forward over the fixed limb
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Musculature of the Pectoral Girdle
Extrinsic = Superficial Musculature
Origin
mid-dorsal raphe and
supraspinous ligament
Insertion
1) M.
trapezius :
immediately under the skin on lateral
surface of neck and withers region,
triangular when seen from the side
spine of the scapula
Body
two parts, cervical and thoracic
separated by aponeurosis
Innervated by
dorsal branch of N. Accessorius
Actions
stabilize shoulders
◦ raises scapula against the trunk
◦ lift and advance the limb
◦ abduct the limb when
sidestepping
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Musculature of the Pectoral Girdle
Intrinsic = Deep Musculature
4) M. serratus ventralis : covered
entirely by M. trapezius and M.
Insertion
latissimus dorsi; the strongest and most
important muscle of the „muscular
dorsal part of medial cartilagenous
sling“; all along fan shaped;
surface of scapula → Facies serrata
Body of two (2) parts:
• (cranially): cervicis
• (caudally): thoracis → most
important weight bearing
element of pectoral girdle
Origin
•
•
of pars cervicis: from transverse
processes of the: 1st to 7th
cervical vertebrae (Su) and 2nd3rd to 7th cervical vertebrae (Ca,
Bo, Eq)
of pars thoracis: from middle of
thoracal ribs 1st to 7th (to max.
9-10th)
Innervated by
N. thoracis longus (→ M.
ser.ventr.thoracis) and ventral
branches of long thoracic nerve
Actions
supporting the weight of the trunk.
At fixed limb the cervical part
raises the neck whole
the thoracic part lifts/propells the
trunk forewards; aid also in forced
inspiration when forelimbs
are abducted; the thoracic part can
move the unweighted limb
forewards.
Musculature of the Pectoral Girdle
Intrinsic = Deep Musculature
4) M. serratus ventralis
Musculature of the Pectoral Girdle
Extrinsic = Superficial Musculature
5) Mm. pectorales superficiales :
in domestic mammals less developed than the deep pectoral
muscle. With 2 heads:
 cranially: M. pectoralis descendens
 more caudally: M. pectoralis transversus
The superficial and deep pectoral muscles make a powerful ventral
sling between ventral chest wall and the forelimbs.
Musculature of the Pectoral Girdle
Extrinsic = Superficial Musculature
5) Mm. pectorales
superficiales :
Origin
• descendens → manubrium of
sternum
• transversus → ventrally
from 1st to 3rd costal
cartilages (in Ca)
→ from 1st to 6th costal
cartilages (Eq,
Bo, Su)
Insertion
• of descendens (cranial):
Crista humeri distal to the
deltoid tuberosity.
• Of transverse (caudal):
covers the elbow joint to
insert on → the medial Fascia
antebrachii (Ca), and →
Crista humeri (Ungulates)
Innervated by
Nn. pectorales
Actions
ventral connection between
thoracic limb and trunk;
abduct the forelimb, pull limb
either forwards or backwards
(depending on position); pulls
the trunk to the side when
limb is fixed
Musculature of the Pectoral Girdle
Intrinsic = Deep Musculature
Origin
sternum and cartilages of true
ribs, occasionally also xiphoid
region, or deep fascia of trunk
(Eq, Ca) Insertion
(varies from species to
species): → Ca: mainly to
Tuberculum majus of the
humerus
→ Su: only to Tuberculum
minus
→ Eq: both to Tuberculi majus
Actions
and minus
supporting trunk and retracting
unsupported limb (→ synergist
with latissimus dorsi); also extends
and fixes shoulder joint, and pulls
the trunk forward (when limb is
advanced and
fixed)
1) M. pectoralis profundus : In
domestic mammals much better
developed than the superficial ones.
With variations of the insertions
between species.
Practical Task 2

Extensors of the Shoulder
Muscles of the Shoulder Joint
General considerations:
There are four (4) muscles of the a) LATERAL group:
 1, supraspinatus, 2, infraspinatus, 3, deltoid, 4, teres minor and
also four (4) of the b) MEDIAL group:
 1, teres major, 2, articularis humeri, 3, subscapular, 4,
coracobrachialis
Muscles of the Shoulder Joint
Lateral muscles
1) M. Supraspinatus: a strong muscle
Origin
fossa supraspinata of scapula
Insertion
Ca
Su, Bo
Eq
Tuberculum
majus of
humeri (with
one tendon)
Tuberculum
Medial and
majus
lateral
humeri (with tuberosites
branched
humeri
tendon); in
Un. also onto
Tuberculum
minus
Innervated
by
humeri
N. suprascapularis
Actions
fix and extend shoulder joint, and helps in
bearing weight of body
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Muscles of the Shoulder Joint
Lateral muscles
2) M. infraspinatus : also a
strong
muscle
Origin
infraspinous fossa of and spine of
the scapula Insertion
Tubercles majus of the humerus
Innervated by
N. suprascapularis of the brachial
plexus
Actions
can act as contractile collateral
ligament assist in flexion or
extension (according to position of
insertion points) in Ca: assists
supination and abduction of
humerus also a flexor when joint is
fixed.
Practical Task 3

Flexors of the Shoulder
◦ M. supraspinatus and M. Infraspinatus
described in task 2
◦ Act as both a flexor and extensor
Muscles of the Shoulder Joint
Lateral muscles
3) M. deltoideus : a flattened muscle directly under the skin
Body of two (2) parts in Ca, Ru:
• pars acromialis
• pars scapularis
◦ in animals without distinct acromion
(Eq, Su) the two parts are fused
Origin
(of pars acromialis): the spine and the
caudal margin of the scapula
Insertion
deltoid tuberosity of the humerus
Innervated by
N. axillaris of the brachial plexus
Actions
flexor of shoulder joint and abducting
the limb
Muscles of the Shoulder Joint
Lateral muscles
4) M. teres minor : a small muscle on caudolateral aspect
of shoulder joint under the deltoid
Origin
distal third of caudal margin of
the scapula
Insertion
just above deltoid tuberosity of
humerus or on the tricipital line
Innervated by
humerus or on the tricipital line
Actions
to flex shoulder joint
Muscles of the Shoulder Joint
Medial muscles
1) M. teres major : a long, flattened, fleshy muscle
Origin
dorsal part of the caudal
scapula
Insertion
Tuberositis teres majoris of
humerus
Innervated by
N. axillaris of the brachial
plexus
Actions
flex shoulder joint; to a small
degree also adducting the limb
Practical Task 4:

Extensors of the Elbow
◦ M. triceps brachii
 Caput
 Caput
 Caput
 Caput
longum
laterale
mediale
accessorium
◦ M. tensor fasciae antebrachii
◦ M. anconeus
Muscles of the Elbow Joint
Extensors
1) M. triceps brachii : the strongest muscle of the thorcic limb;
activates two joints
Body :
in all domestic mammals with
four (4) heads except Eq, (3
heads)
◦ caput longum
◦ caput laterale
◦ caput mediale
◦ caput accesory
(not in Eq)
Origin
◦ of caput longum: → caudal
border of scapula
◦ of caput laterale: → laterally
from humerus near the deltoid
tuberosity
◦ of caput mediale: → medial
aspect of shaft of humerus near
the teres tubercle
◦ of caput accessorium: →
caudally near head of the
Insertion
on olecranon process of ulna
(by all 4 heads)
Innervated by
N. radialis from the brachial
plexus
Actions
extend the elbow joint; the
long head also flexes the
shoulder joint; in standing
animal
it greatly participates in the
passive „stay apparatus“ by
fixing the elbow.
Muscles of the Elbow Joint
Flexors
1) M. triceps brachii : the strongest muscle of the thoracic limb;
activates two joints
Muscles of the Elbow Joint
Flexors
2) M. anconeus : a small, powerful muscle covered by
triceps; could be viewed as part of triceps brachii
Origin
distal half of caudal border of
humerus and lateral and medial
epicondylesInsertion
laterally on olecranon
Innervated by
N. radialis of the brachial
plexus
Actions
extending the elbow joint
Practical Task 4

Flexors of the Elbow
◦ M. Biceps brachii
◦ M. Brachialis
Origin
supraglenoid tuberosity of the
scapula
Insertion
after the elbow joint its distal
tendon dividing into two,
inserting to medial tuberosity
of both the proximal radius and
adjacent ulna
Innervated by
N. musculocutaneus from the
brachial plexus
Actions
flex elbow joint and also to
extend the shoulder; in Eq: a
long superficial tendin (→
lacertus fibrosus) joining the
antebrachial fascia, eventually
inserting on metacarpal
tuberosity
→ transmitting action of biceps
into carpal joint → functioning
Muscles of the Elbow
Joint
Flexors
2) M. biceps brachii : a spindle-shaped
muscle, acting on two (2) joints; its
proximal tendon crosses the capsule of the
shoulder joint (in: Ca, Su and sheep), resp.
it is protected by large intertuberal bursa
(in: goat, Bo, Eq)
Muscles of the Elbow Joint
Flexors
1) M. brachialis : fleshy, long-fibred muscle, winding over lateral
surfce of humerus and crossing the biceps obliquely
Origin
caudally below the head of the
humerus
Insertion
on both radius and ulna
between M. biceps femoris and
M. extensor carpi radialis
Innervated by
N. musculocutaneus of the
brachial plexus
Actions
flex and lift elbow joint