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Types of Synovial Joints There are seven types of synovial joints in the body.
Each of the different synovial joints has the basic
structural features common to all synovial joints but is
further classifi ed based on the shape of and motion that occurs at the articular surfaces of the joint. The different types of
synovial joint are depicted below and on the opposite page. Note the shapes of the reciprocal surfaces as you study these
photos.
Hinge joint example
Humero-ulnar joint of elbow
Plane joint examples
Intertarsal joints Pivot joint examples
Proximal radio-ulnar joint of elbow
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Bicondylar joint example
Knee joint
Condylar joint example
Wrist joint
Saddle joint example
Metacarpal-carpal joint of thumb
Ball and socket joint example
Shoulder joint
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Temporomandibular Joint The complex temporomandibular joint differs from
other synovial joints by having an articular disc
that usually separates the joint into two separate
synovial capsules, one above and one below the disc. The articular surfaces have a covering of dense fi brocartilage rather
than the typical hyaline cartilage of most synovial joints. With its associated ligaments this joint structure accounts for the
complex series of movements that are essential during the activities of eating and speech. Each temporomandibular joint is
a condylar joint and both joints together form a bicondylar joint. The fi brous membrane of the articular capsule spans from
temporal bone to mandible only on the lateral side. Anteriorly, medially, and posteriorly the fi bers attach from mandible and
temporal bone to the articular disc. Extrinsic ligaments that help stabilize the joint are the lateral temporomandibular ligament, sphenomandibular ligament, and stylomandibular ligament.
1 Mandibular condyle
2 Mandibular ramus
3 Articular tubercle of temporal bone
4 Mastoid process of temporal bone
5 Mastoid air cells
6 Superior compartment of articular cavity
7 Inferior compartment of articular cavity
8 Articular disc
9 Joint (articular) capsule
10 Masseter muscle
11 Parotid gland
12 Brain
13 External acoustic meatus
14 Sigmoid venous sinus
Section of right temporomandibular joint
Lateral view of sagittal section
Bones of temporomandibular joint
Lateral view
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Glenohumeral Joint The glenohumeral or shoulder joint is a ball and socket joint and is
the most mobile joint in the body. The tremendous range of motion
at this joint is the result of few external ligaments that present little
limitation to movement, and shallow, ovoid articular surfaces that make movements in all planes of space possible. In fact,
surrounding muscles and tendons play a more signifi cant role in joint support than do the joint structures. The capsular ligament is extremely lax, providing limited support to the joint. Blending with the capsule are the tendons of four muscles.
Together the capsule and tendons form the rotator cuff, which is the major support structure of the joint.
1 Articular cartilage
2 Synovial membrane
3 Fibrous membrane
4 Glenoid labrum
5 Acromioclavicular ligament
6 Clavicle
7 Humerus
8 Glenoid of scapula
9 Acromion of scapula
10 Supraspinatus muscle
11 Subscapularis muscle
12 Deltoid muscle
13 Tendon of long head of biceps brachii
14 Skin
15 Subcutaneous layer
Section of left glenohumeral joint
Anterior view of frontal section
Bones of glenohumeral joint
Anterior view
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Elbow Joint The elbow joint is a complex joint comprised of multiple articular surfaces within one articular
capsule. The elbow joint can be subdivided into three distinct articular interfaces —
the humero-ulnar joint (hinge), the humeroradial joint (combined hinge and pivot), and
1 Articular cartilage
2 Joint (articular) capsule
3 Articular (synovial) cavity
4 Capitulum of humerus
5 Olecranon of ulna
6 Head of radius
7 Anular ligament
8 Biceps brachii muscle
9 Brachialis muscle
10 Triceps brachii muscle
11 Brachioradialis muscle
Section of pronated left elbow joint
Medial view of sagittal section
Bones of elbow joint
Anterior view
the proximal radioulnar joint (pivot). Two distinct pairs of movements occur as a result of the articulations within the elbow
joint — the hinged movements of fl exion and extension, and the rotational movements of pronation and supination. Unlike
the shoulder joint, the joints fo the elbow have strong extrinsic ligaments that limit movemnts and stabilize the articulating
bones. The fi brous capsule is thin anteriorly and posteriorly, allowing for free range of motion during fl exion and extension.
On either side the capsule is reinforced by strong extrinsic ligaments, the ulnar collateral and radial collateral ligaments.
Wrapping from the back of the ulna at the base of the olecranon to the front of the ulna at the lateral surface of the coronoid
process is the semicircular anular ligament. With the radial notch of the ulna this ligament forms a fi bro-osseous ring for the
pivoting action of the radial head.
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Hip Joint Like the shoulder joint the hip joint, also a ball and socket joint, allows for great freedom of motion, although the range of motion is not quite as great as that of the shoulder. This comparative
decrease in mobility results from the deep hip socket with its extended labrum, which almost
1 Ligament of head of femur
2 Joint (articular) capsule
3 Articular cartilage of acetabulum
4 Articular cartilage of femur
5 Articular (synovial) cavity
6 Acetabular labrum
7 Fovea capitis of femur
8 Head of femur
9 Greater trochanter of femur
10 Os coxae
11 Psoas major muscle
12 Iliacus muscle
13 Adductor muscles
14 Vastus lateralis muscle
15 Gluteus medius muscle
16 Gluteus minimis muscle
17 Obturator internus muscle
18 Obturator externus muscle
19 Skin
20 Subcutaneous layer
21 External iliac artery
22 Intestine
Bones of hip joint
Anterior view
Section of right hip joint
Anterior view of frontal section
completely engulfs the head of the femur. In addition, thick extrinsic ligaments tightly surround the joint to form a strong,
reinforced capsule. The three major ligaments of the hip joint, the iliofemoral, pubofemoral, and ischiofemoral, form a sheath
around the fi brous capsule. The iliofemoral ligament is argued to be the strongest ligament in the human body. Often called
the Y-shaped ligament it passes superior and anterior to the joint, running from the anterior inferior iliac spine to the intertrochanteric line. With the thinner pubofemoral and ischiofemoral ligaments it spirals around the joint to stabilize this powerful
joint. In additon to these large ligaments, a triangular fl at band, the ligament of the head of the femur, extends from the fovea
of the femoral head to the margins of the acetabular fossa. This ligament is also important because it functions as a pathway
for blood vessels that supply the bone tissue in the head of the femur.
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Knee Joint The knee joint is a combined bicondylar and saddle joint. The relationships between the
femur and the tibia provide no interlocking joint mechanisms or stability between the neighboring bones, and from this perspective the knee joint is completely unstable. The strength
of the knee joint is dependent on strong ligaments and surrounding muscles. Although its primary motions are of a hinge
nature, it is a complex joint with subtle rotational and sliding movements also. The major stabilizers of the joint are four
strong ligaments. Two collateral ligaments support the joint on either side, while two cruciate ligaments criss-cross through
the middle of the joint. The tibial or medial collateral ligament is a strong, fl at band that stretches from the femoral epicondyle
to the tibial condyle. Posteriorly it fi rmly attaches to the joint capsule and the medial meniscus, while anteriorly bursae
separate it from these structures. The fi bular or lateral collateral ligament is a strong cord that runs from the lateral femoral
1 Articular (synovial) cavity
2 Articular cartilage
3 Medial meniscus
4 Suprapatellar bursa
5 Prepatellar bursa
6 Infrapatellar bursa
7 Infrapatellar fat pad
8 Fibrous membrane of joint capsule
9 Synovial membrane of joint capsule
10 Lateral meniscus
11 Fibular collateral ligament
12 Tibial collateral ligament
13 Anterior cruciate ligament
14 Posterior cruciate ligament
15 Oblique popliteal ligament
16 Patellar ligament
17 Quadriceps tendon
18 Femur
19 Tibia
20 Fibula
21 Patella
22 Periosteum
23 Semimembranosus muscle
24 Gastrocnemius muscle
25 Soleus muscle
26 Popliteal fat
Bones of knee joint
Anterior view
Section of right knee joint
Lateral view of sagittal section
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epicondyle to the head of the fi bula. Unlike the tibial collateral ligament it does not attach to the lateral meniscus or joint
capsule. The cruciate ligaments stabilize the knee from excessive anterior-posterior and rotational movements. The anterior cruciate ligament ascends posterolaterally from the medial aspect of the intercondylar area to the medial aspect of the
lateral condyle of the femur. The shorter posterior cruciate ligament ascends from the posterior intercondylar area to the
medial femoral condyle. Both cruciates have fi bers that blend with the lateral meniscus. In additon to these ligamentous
structures, two semilunar menisci project into the capsule between the femoral condyles and the articular plateaus of the
tibia. The large, extensive articular capsule connects the femur, patella, and tibia.
Dissection of left knee joint
Anterior view
Dissection of left knee joint
Anterior view
Dissection of left knee joint
Posterior view
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Synovial Bursae and Sheaths A synovial bursa is a small sac-like structure interposed between structures that
generate signifi cant amounts of friction.
Bursae have a similar design to the articular capsule of a synovial joint. These small bags have an outer fi brous membrane
of dense irregular collagenous connective tissue and an inner lining of synovial membrane. The synovial membrane produces
a small amount of synovia as a lubricant inside the sac. The fi brous membrane binds to surrounding tissues, allowing the
juxtaposed walls of synovial membrane to rub together in a frictionless manner. Many bursae arise as outgrowths of synovial joint cavities. In some cases these pinch off from the joint forming sacs that are independent from the joint, while other
bursal sacs retain their connections with the joint cavity. A synovial sheath is a modifi ed bursa that wraps around a tendon
to protect it from friction on all sides. In the tight confi nes of the wrist, ankle, and digits, tendons often pass beneath fi brous
bands called retinacula. The retinaculum is a connective tissue band that crosses over the tendons and keeps them from
being displaced upward when the muscle shortens and bends the joints. Because the retinaculum and bone create a fi broosseous tunnel around the tendon, considerable friction can occur on all surfaces of the tendon at these locations. As the
tendon moves through the tunnel, the juxtaposed synovial membranes smoothly glide over each other with minimal friction.
1 Suprapatellar bursa
2 Prepatellar bursa
3 Infrapatellar bursa
4 Synovial (tendon) sheath
5 Retinaculum
6 Flexor digitorum superficialis tendon
7 Flexor digitorum profundus tendon
8 Lumbrical muscles
9 Flexor digiti minimi brevis muscle
10 Abductor digiti minimi muscle
Synovial bursae around the knee joint
Medial view of sagittal section
Tendon sheath of fi ngers
Anterior view, pin inserted into tendon sheath
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Bodies are designed to move! We move when we walk, jog,
or run, activities that transport our bodies from one location to another. In addition to moving
from location to location we also move in other ways. For example, think about grasping something with your hands and placing it in your mouth, or protecting yourself by kicking at
something with your lower limb. How about throwing something? All of
these activities are forms of movement that occur without moving
from one location to another, yet they are movements nonetheless. Like moving about, these other types of movements are
not only essential for survival, but defi ne the broad spectrum for the majority of human movement. Refl ect for
a moment on the wide variety of movements that you
make without moving from place to place. For example, think about the variety of intricate movements
required to eat a meal, movements such as grasping,
manipulating, cutting, chewing, and swallowing.
Another example is getting dressed for the day. From
the simple movements of pulling on clothing to the
intricate movements of buttoning shirts and tying
shoelaces, getting dressed involves a wide variety of
movements. And here is something else to ponder —
how about all the movements involved in communication? Th ink of the wide array of movements
that you produce as you communicate with
others — whether the communication involves
writing a note on a piece of paper, typing a letter
on the keyboard of a computer, signaling pleasure
and happiness with a smile, or using your voice to
talk to a friend on the telephone.
We could go on and on discussing the wide
variety of movement and its importance, but the bottom
line is all movement results from the combined activity
of individual muscles. Th e most detailed movements you
make can be broken down into the simple actions of individual muscles moving the
bones of the skeleton at the joints. Th is chapter introduces the muscular system. On the
pages that follow you will see the structural design of a typical muscle and whole body views of
the muscles of the body. Our approach to the skeletal muscles of the body is based on their embryonic origins. Th e four chapters that follow this chapter cover each of the developmental
groups of muscles — muscles of the head, muscles of the trunk, muscles of the upper limb, and
muscles of the lower limb. Th e logic of this approach will be further discussed as we introduce
each chapter.
Find more information
about the muscular system in
REAL ANATOMY
8 Muscular System
139
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1 Muscle belly or body
2 Tendon of origin
3 Tendon of insertion
4 Collagen fiber
5 Muscle cell or fiber
6 Nucleus
Dissection of brachium highlighting biceps brachii
as example of muscle anatomy
Anterior view
Dense regular connective tissue of tendon
200x
While there is a wide variety to the shape, size, and architecture of the skeletal muscles of the body, most muscles share
a common basic design — a tendon of origin, a muscle body
Anatomy of a Muscle
7 Biceps brachii muscle
8 Brachialis muscle
9 Triceps brachii muscle
10 Epimysium
11 Perimysium
12 Endomysium
or belly, and a tendon of insertion. The tendons, projecting from the muscle belly, are a continuation of the connective tissue
surrounding the muscle cells within the belly of the muscle. As the connective tissue projects beyond the muscle cells, it
condenses to become the tendons, which merge and blend with the periosteum to attach the muscle to bone.
13 Blood vessels in perimysium
14 Nerve in perimysium
15 Fascia
16 Sucutaneous layer
17 Skin
18 Periosteum
Skeletal muscle tissue of muscle belly
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Photomicrograph of muscle fasciculus
Transverse section, 100x
Transverse section of left brachium at level of dashed line
Inferior (distal) view, anterior at top
Dashed line shows level of transverse section
Anterior view
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Skeletal muscles of the body
Anterior view
Skeletal muscles of the body
Lateral view
Skeletal muscles of the body
Posterior view
In the dissections below, the integument and fascia were removed to reveal
the superfi cial skeletal muscles. Some of the larger muscles are identifi ed
here. More detailed muscle labeling will occur in the next four chapters.
Skeletal Muscles
1 Platysma
2 Pectoralis major
3 Deltoid
4 Rectus abdominis
5 External oblique
6 Biceps brachii
7 Triceps brachii
8 Trapezius
9 Brachioradialis
10 Latissimus dorsi
11 Gluteus maximus
12 Biceps femoris
13 Sartorius
14 Vastus medialis
15 Rectus femoris
16 Adductor magnus
17 Tibialis anterior
18 Gastrocnemius
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Head muscles, like the platysma and risorius seen in
the photo on this page, arise from two sources during embryonic development. One source
is the pharyngeal arches, which give rise to the majority of the head muscles. Muscles of
the pharyngeal
arches include
the muscles
of mastication,
muscles of the
middle ear, muscles of facial expression, muscles
of the palate, muscles of the pharynx,
muscles of the larynx, and the sternocleidomastoid and
trapezius. Th e second
category of head muscles
includes those muscles that
arise from the pre-otic and occipital
somites. Th e pre-otic somites give rise to the extraocular muscles, and the occipital somites give rise
to the tongue muscles. Grouping muscles by their developmental origin is an eff ective way to understand the
muscles because muscles that share a developmental origin share a common nerve supply. For example, during
development all the muscles of the fi rst pharyngeal arch
are innervated by the mandibular branch of the trigeminal nerve; therefore the mandibular nerve and its
branches innervate all eight muscles that arise from the
fi rst pharyngeal arch. Th e same is true for each of the
other arches, as well as the head somites. Th is chapter
will showcase the muscles of the head and emphasize
their developmental origin and neuromuscular pairing. With a few exceptions, all of the head muscles are
depicted in the photos throughout this chapter. Th e
following page outlines the developmental groups of
head musculature and their nerve associations.
Find more information
about the muscles of the
head in
REAL ANATOMY
9 Head Muscles
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of these muscles arise from the paraxial mesoderm of the embryonic head. Unlike many anatomy sources that mix these
muscles into multiple groups, with no logic to their innervation, we choose to present them based on their embryonic origins.
Taking this approach makes it very easy to learn the innervation patterns of the head muscles because each developmental
group is associated with a distinct cranial nerve or set of cranial nerves (see groups below). Accompanying each labeled
dissection photograph on the pages that follow are small reference photos that clearly depict each of the developmental
muscle groups of the head. Since some of the head muscles migrate into the neck, we also depict the somitic muscles of
the neck in the reference photos, to help distinguish them from the true head muscles. The somitic muscles of the neck will
be the subject of the next chapter. For example, the fi rst photo (see opposite page) labels numerous head muscles. The
reference photos clearly reveal that the labeled muscles are primarily from two sources — the fi rst pharyngeal arch and the
second pharyngeal arch (accounting for the majority of the muscles). The third reference photo shows that some muscles
are from neck somites.
This chapter presents numerous dissections of the head and neck that depict the
muscles of the head. We defi ne the head muscles as all muscles that arise from
the pharyngeal (branchial) arches or the head somites (pre-otic and occipital). All
Head Muscles
Muscles of the First Pharyngeal Arch
(Nerve supply - mandibular branch of the trigeminal nerve CN V)
Temporalis
Masseter
Medial pterygoid
Lateral pterygoid
Anterior digastricus
Mylohyoid
*Tensor tympani
Tensor veli palatini
Muscles of the Second Pharyngeal Arch
(Nerve supply - facial nerve CN VII)
Occipitofrontalis
Temporoparietalis
Transversus nuchae
Procerus
Nasalis
*Depressor septi nasi
Orbicularis oculi
Corrugator supercilii
Depressor supercilii
Auricularis anterior
Auricularis superior
Auriculalris posterior
Intrinsic auricular muscles
Helicis major muscle
Helicis minor muscle
Tragicus muscle
*Pyramidal muscle of auricle
Antitragicus muscle
*Transverse muscle of auricle
*Oblique muscle of auricle
Orbicularis oris
Depressor anguli oris
Transversus menti
Risorius
Zygomaticus major
Zygomaticus minor
Levator labii superioris
Levator labii superioris alaeque nasi
Depressor labii inferioris
Levator anguli oris
Buccinator
Mentalis
*Stapedius
Stylohyoid
Posterior digastricus
Platysma
Muscle of the Third Pharyngeal Arch
(Nerve supply - glossopharyngeal nerve CN IX)
Stylopharyngeus
Muscles of the Fourth Pharyngeal Arch
(Nerve supply - vagus nerve CN X)
Levator veli palatini
Palatoglossus
Palatopharyngeus
Musculus uvulae
Superior pharyngeal constrictor
Middle pharyngeal constrictor
Inferior pharyngeal constrictor
Cricothyroid
Salpingopharyngeus
Muscles of the Sixth Pharyngeal Arch
(Nerve supply - vagus nerve CN X)
Posterior crico-arytenoid
Lateral crico-arytenoid
Vocalis
Thyro-arytenoid
Oblique arytenoid
Transverse arytenoid
Muscles of the Posterior Pharyngeal Arch
(Nerve supply - accessory nerve CN XI)
Sternocleidomastoid
Trapezius
Muscles of the Pre-otic Somites
(Nerve supply - oculomotor CN III, trochlear CN IV, and abducens CVI)
Superior rectus
Inferior rectus
*Medial rectus
Lateral rectus
Superior oblique
Inferior oblique
Levator palpebrae superioris
Muscles of the Occipital Somites
(Nerve supply - hypoglossal nerve CN XII)
Genioglossus
Hyoglossus
Styloglossus
Superior longitudinal muscle
Inferior longitudinal muscle
Transverse muscle
Vertical muscle
All the muscles listed above are depicted in photos in this chapter except those marked with an asterisk.
145
First arch muscles
Somitic muscles
Superfi cial head muscles of neck
Anterolateral view
1 Masseter
2 Anterior belly of digastricus (cut)
3 Mylohyoid
4 Frontal belly of occipitofrontalis
5 Temporoparietalis
6 Procerus
7 Nasalis
8 Orbicularis oculi
9 Corrugator supercilii
10 Depressor supercilii
11 Auricularis anterior
12 Auricularis superior
13 Orbicularis oris
14 Depressor anguli oris
15 Transversus menti
16 Zygomaticus major
17 Zygomaticus minor
18 Levator labii superioris
19 Levator labii superioris alaeque nasi
20 Depressor labii inferioris
21 Levator anguli oris
22 Buccinator
23 Mentalis
24 Posterior digastricus
25 Epicranial aponeurosis
26 Temporal fascia
27 Parotid gland (cut)
Second arch muscles
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The dissections depicted on this page and the facing page represent two stages Head Muscles in a dissection of the head. Below is a superfi cial dissection with the integument
1 Temporalis
2 Masseter
3 Mylohyoid
4 Anterior belly of digastricus
5 Frontal belly of occipitofrontalis
6 Temporoparietalis
7 Orbicularis oculi
8 Procerus
9 Levator labii superioris alaeque nasi
10 Nasalis
11 Levator labii superioris
12 Zygomaticus major
13 Levator anguli oris
14 Orbicularis oris
15 Buccinator
16 Depressor anguli oris
17 Depressor labii inferioris
18 Mentalis
First arch muscles
Second arch muscles
Somitic muscles
of neck
Fourth arch muscles
Posterior arch muscles
Head muscles, superfi cial dissection
Lateral view
and some fascia removed. On the opposing page some superfi cial muscles were removed. Most of the
head muscle groups are represented. Note also the somitic muscles of the neck that are visible.
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19 Auricularis anterior
20 Auricularis superior
21 Auricularis posterior
22 Occipital belly of occipitofrontalis
23 Transversus nuchae
24 Epicranial aponeurosis
25 Helicis major
26 Helicis minor
27 Tragicus
28 Antitragicus
29 Posterior belly of digastricus
30 Stylohyoid
31 Middle pharyngeal constrictor
32 Inferior pharyngeal constrictor
33 Sternocleidomastoid
34 Trapezius
35 Styloglossus
36 Temporal fascia
37 Parotid gland
38 Submandibular gland
39 Thyroid cartilage
40 Sternohyoid
41 Omohyoid
42 Thyrohyoid
43 Longus colli
44 Middle scalene
45 Posterior scalene
46 Levator scapulae
47 Splenius capitis
48 Deltoid
First arch muscles
Second arch muscles
Somitic muscles
of head and neck
Fourth arch muscles
Posterior arch muscles
Head muscles, masticatory muscles exposed
Lateral view
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44
45
46
47
48
148
The lateral head dissections below and opposite are deeper
dissections that expose the deep masticatory muscles (below) and the extraocular muscles (opposite).
Head Muscles
Head muscles, deep masticatory muscles exposed
Lateral view, portion of mandible removed
First arch muscles
Second arch muscles
Somitic muscles
of head and neck
Fourth arch muscles
Posterior arch muscles
1 Temporalis
2 Masseter
3 Medial pterygoid
4 Lateral pterygoid
5 Anterior belly of digastricus
6 Mylohyoid
7 Frontal belly of occipitofrontalis
8 Occipital belly of occipitofrontalis
9 Transversus nuchae
10 Procerus
11 Nasalis
12 Orbicularis oculi
13 Auricularis anterior (cut)
14 Auricularis superior (cut)
15 Auricularis posterior
3
4
5
1
7
10
26
11
12
14
13
20
29
21
27
43
32
48
35
15
16
17
18
9 19
8
53
54
49
44
50
51
36
34
47
46
45
30
2
6
23 25
28
31
33
59
3
4
5
1
7
10
26
11
12
14
13
20
29
21
27
43
32
48
35
15
16
17
18
9 19
8
53
49
44
50
51
36
34
47
46
45
30
2
6
23 25
28
31
33
59
149
Head muscles, extraocular muscels exposed
Lateral view, lateral wall of orbit removed
First arch muscles
Second arch muscles
Posterior arch muscles
Somitic muscles
of head and neck
16 Helicis major
17 Helicis minor
18 Tragicus
19 Antitragicus
20 Orbicularis oris
21 Depressor anguli oris
22 Transversus menti
23 Zygomaticus major
24 Zygomaticus minor
25 Levator labii superioris
26 Levator labii superioris alaeque nasi
27 Depressor labii inferioris
28 Levator anguli oris
29 Buccinator
30 Mentalis
31 Stylohyoid
32 Posterior belly of digastricus
33 Middle pharyngeal constrictor
34 Inferior pharyngeal constrictor
35 Sternocleidomastoid
36 Trapezius
37 Superior rectus
38 Inferior rectus
39 Lateral rectus
40 Supra-orbital nerve
41 Inferior oblique
42 Levator palpebrae superioris
43 Styloglossus
44 Hyoglossus
45 Sternohyoid
46 Omohyoid
47 Thyrohyoid
48 Longus colli
49 Splenius capitis
50 Levator scapulae
51 Posterior scalene
52 Middle scalene
53 Epicranial aponeurosis
54 Temporal fascia (cut)
55 Parotid gland
56 Submandibular gland
57 Skin
58 Subcutaneous layer
59 Thyroid cartilage
1
5
6
7
8
10
20
29
21
27
22
35
24
15
53
54
49
50
51
52
30
2
23
25
26
28
37
39
38
41
42
40
55
56
57
58
1
5
6
7
8
10
20
29
21
27
22
35
24
15
53
49
50
51
52
30
2
23
25
26
28
37
39
41
57
58
150
The dissections on this and the opposing page are
deep dissections of the head and neck that expose
many of the muscles of the palate, pharynx, and
Head Muscles
tongue. The palatal and pharyngeal muscles, along with the muscles of the larynx, are the deepest of the head muscles. These groups arise from the third, fourth, and sixth arches and form the
muscular walls to the upper regions of the embryonic gut tube. All of the “true” tongue muscles
(the palatoglossus is included by many with the tongue muscles, but it is a muscle of the palate
from fourth arch origin) arise from the occipital somites and are innervated by the cranial nerve
XII, the hypoglossal nerve. The hypoglossal nerve is the lowest of the ventral motor nerves arising from the brainstem and is developmentally paired with the occipital somites.
First arch muscles
Second arch muscles
Somitic muscles
of head
Third arch muscles
Fourth arch muscles
Head muscles, palatal and pharyngeal muscles exposed
Lateral view, mandibular ramus removed
1
2
3
4
5
6
8
9
10
11
12
13
14
15
17
18
22
23
24
25
26
27
28
29
1
2
3
4
5
6
8
9
10
11
12
13
14
15
17
18
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