BIOLOGY 453 - COMPARATIVE VERT. ANATOMY
BIOLOGY 453 - COMPARATIVE VERT. ANATOMY
LAB 9 - SHARK MUSCLES
1. Identify the red (aerobic) fibers in the shark by making a new cut through the tail region.
2. Identify these special connective tissues associated with muscles: fascia, raphe & myosepta.
3. Know the terms for muscle actions below: e.g. flexion, extension, abduction, etc.
4. Learn 1 origin & 1 insertion point for each muscle.
5. Learn at least 1 action for each muscle from the summary table.
6. Know the evolutionary origin of each muscle in the homologies table:
a. Epaxial & Hypaxial.
b. Appendicular: dorsal or ventral & pectoral or pelvic.
d. Branchiomeric arch 1, branchiomeric arch 2, or branchiomeric arches 3-7.
Topic General Red-White Fiber Skinning Shark Muscles
Kardong & Zalisko 90 90 91-97
Fishbeck & Sebastiani pg. 51-54 Fig. 17.4 pg 143 141 142-151
MUSCLE ACTION & TERMINOLOGY
Heithaus, P. 1999. Muscle Functions. Cat Anatomy Tutorial. Dept. of Biology, Kenyon College.
Dauzvardis, M.F. et. al. 1996-1998. Master Muscle List. Loyola Univ. Med. Educ. Network (LUMEN)
Univ. of Michigan. Learning Center. 1994. Hypermuscle: Muscles in Action. (Short film clips).
Univ. of Minnesota. 2003. Muscle / Joint Actions. Veterinary Medicine Web.
Burnett, S.C. 2007. More Shark Muscles. Biology 3650. Clayton State Univ.
Peters, S. 2009. Course Handouts (see Lateral, Ventral & Hypobranchial muscles of shark). Comparative Vertebrate
Anatomy, Biol. 4293/5293. Department of Biology, University of North Carolina at Charlotte.
York, H. 2001. Vertebrate Anatomy Lab. Labeled shark muscles. Kent Univ.
Lateral View: http://fp.dl.kent.edu/hyork/shmuslt.htm
Ventral view: http://fp.dl.kent.edu/hyork/shmusv.htm
Western Kentucky University. 1999. Shark Musculature. Digital Anatomy Online.
Muscle Attachments: Typically, a muscle is attached to two different bones. For a given body movement, one bone (origin)
is fixed in some way, the other (insertion) moves as a result of muscle contraction. The origin is often the proximal bone and the
insertion the distal bone. There are many exceptions. Some muscles have several origins (called "heads"), which may be on more than 1
bone. Multiple insertions occur on the fingers or toes.
Connective Tissues: Typically muscles attach to bones via a slender, cord-like unit of dense, regularly arranged connective
tissue called a tendon [tend = stretch]. Some muscles attach to other muscles directly on broad insertion points. Sheets of connective
tissues that surround a muscle are called fascia [= bundle]. An aponeurosis [apo = from, neuro = sinew, cord] is a broad thin, sheet-
like tendon that attaches a muscle onto a bone. Two mirror-image muscles, on either side of the mid-dorsal or midventral line may attach
to each other along a long, thin line of connective tissue, called a raphe. Thus, a raphe is a long, seam-like tendon such as the linea
alba. In fishes, axial muscles are divided by myosepta. A horizontal septum divides the epaxial & hypaxial muscles of the shark. In
addition, most of these terms are defined in your lab manual pg. 87.
Muscle Actions: Depending on the orientation and attachment of their fibers, muscles may act in one or several directions.
Long muscles are usually kinetic (able to produce highly visible external motion). Short, deep muscles tend to be responsible for precise,
small-scale adjustments rather than gross movements. When we speak of a particular movement, the muscle that produces it is called
an agonist. A muscle that produces the opposite movement is called an antagonist. Mutually opposing muscles often function together
to fix or stabilize a bone. Different muscles that cooperate to produce the same action are called synergetic.
Muscle Physiology: Red muscle fibers are aerobic which means they have long endurance. Red fibers have a higher
myoglobin content that gives them a red color (myoglobin stores oxygen). Red fibers have a richer blood supply & more mitochondria in
their cells. Vertebrates use red muscle for locomotion at low to moderate speeds or for endurance activities. This tissue forms thin sheets
on the outermost edges of the trunk & tail in most fishes. White muscle fibers are anaerobic and are used for short bursts of speed or
power. White muscle fibers are usually larger in diameter than red fibers & thus are stronger. However, they produce most of their
force anaerobically causing a build-up of lactic acid. High levels of lactic acid can induce muscle fatigue, thus the short-term
effectiveness of white fibers. In typical fishes, white fibers make up most of the body mass in the trunk & tail.
Greek & Latin Roots Indicating Direction, Relative to Axes of Body
dorsi - dorsal intrinsic - inside superficialis - superficial
externus- superficial lateralis - lateral superioris - superior (dorsal)
extrinsic - outside medialis - medial, middle transversus - transverse
internus - deep, internal obliquus - oblique ventralis - ventral
Greek & Latin Roots Indicating Specific Regions of the Body
acromio - tip coraco - coracoid hyomandibulae - hyomandibular scapularis - scapula
abdominis - abdomen femoris - femur ilio - ilium spino - spine
capitus - head genio - chin mandibular - mandible sterno - sternum
cervicis - neck gluteo - rump mastoid - breast shaped temporalis - temples
cleido/clavo - clavicle hyoid/hyoideus - hyoid palatoquadrati - palatoquadrate cart. thoracis - thoracic region
Greek & Latin Roots Indicating Shape, Size, or Color of Muscle
deltoid - triangle longissimus - longest platys - flat serratus - serrated
digastric - two "bellies" magnus/major - larger rectus - straight, parallel teres - long & round
gracilis - short, slender maximus - largest rhomboideus - rhomboid trapezius - trapezoid
latissimus - widest minimus - smallest semi - half, partly vastus - great
Roots Describing Muscle Actions
masseter - chewing mylo - mill, molar sartorius - " sits" like a tailor
Muscle Homologies & Evolutionary Origins
Cranial Muscles: Branchiomeric muscles formed as a series of repeated elements that controlled movement of the gills of
jawless fishes. Some of the gill muscles moved with the jaws and the hyoid arch when these skeletal changes were made. With the loss
of the gills in most tetrapods, many muscles were lost, but some took on new functions in the throat and laryngeal region, and even as
an appendicular muscle.
Hypobranchial muscles evolved as a series of long muscles that ran anterior-posterior from the jaws to the pectoral girdle.
Their primary functions are opening the mouth or expansion of the gill chamber. In mammals, these muscles are reduced in size, but still
run anterior-posterior from the pectoral girdle forward to the larynx, hyoid or chin.
Trunk Muscles: Epaxial muscles in a shark are large and show their original metameric design. The muscles are held
together with tough sheets of connective tissues (myosepta). The myosepta divide the muscle segments (myomeres) that are major
locomotory structures (for lateral undulation.) In mammals, these muscles are greatly reduced and highly modified. Most epaxial muscles
extend across many vertebrae and aid support & extension of the back. These muscles attach to neural spines and transverse
processes on the vertebrae. They are most readily seen in the lumbar region. They are present in the neck and thoracic area as well, but
are often covered by pectoral muscles.
The hypaxial muscles run below the horizontal septum. They are also important for lateral undulation, but show a less
complex arrangement & form thinner sheets in the trunk to support the viscera. Mammals have reduced these muscles to several very
thin sheets in the abdominal region. These muscles aid flexion of the trunk, and support the viscera. They are still relatively strong
because the sheets run in different directions (i.e. plywood effect). In the thoracic region these muscles are deep to the pectoral
musculature, and are often divided into small units by the ribs.
Appendicular Muscles: In a shark, extrinsic muscles form two thin, flat sheets that extend out onto the pterygiophores. The
dorsal sheet allows abduction or extension of the fin and the ventral sheet allows adduction or flexion of the fin. Mammals have a large
amount of intrinsic and extrinsic musculature associated with the limbs. The mammalian pectoral muscles are primarily associated with
the scapula. Muscles literally hold the pectoral girdle in suspension in a cat because the clavicle is reduced to a fragment. A few muscles
that now located on the pectoral girdle may have originated from branchiomeric or hypaxial muscle sources that from a ventral to a more
Learn which cat & shark muscles fall into the same evolutionary “groups”.
Muscle Evol. Origin Chondrichthyes: Shark Muscles Mammalia: Cat Muscles
Branchiomeric: 1st Arch Adductor mandibulae Masseter
Levator palatoquadrati Temporalis
Spiracularis Anterior digastric
Branchiomeric: 2 nd Arch Levator hyomandibulae none examined in lab
Branchiomeric: 3 rd - 7 th Cucullaris [cucull = hood] Clavotrapezius
Arches Dorsal & ventral constrictors Acromiotrapezius
Hypobranchial Coracomandibularis Geniohyoid
Axial: Epaxial Dorsal longitudinal bundles; myomeres Multifidus spinae
Axial: Hypaxial Lateral longitudinal bundles; myomeres Serratus ventralis & Rhomboideus
Ventral longitudinal bundles; myomeres External oblique & Rectus abdominus
Appendicular: Pectoral extensors (abductors) Latissimus dorsi & Teres major
Pectoral, dorsal Acromiodeltoid & Spinodeltoid
Appendicular: Pectoral flexors (adductors) Pectoralis major & Pectoralis minor
Pectoral, ventral Supraspinatus & Infraspinatus
Appendicular: Pelvic extensors (abductors) Gluteus maximus & Gluteus medius
Pelvic, dorsal Sartorius & Vastus lateralis
Appendicular: Pelvic flexors (adductors) Biceps femoris & Gracilis
Pelvic, ventral Adductor femoris & Semimembranosus
Muscle Action Terminology
Levator: elevate; lifts bone in vertical plane; move body part to a superior position.
Depressor: lowers bone in vertical plane; move body part to an inferior position.
Extension: to open, or unfold; increase angle of a joint to its normal anatomical position;
or movement in a sagittal plane that takes part of the body backward from anatomical position.
Hyperextension: increase the angle of a joint beyond its normal anatomical position.
Flexion: to fold or decrease the angle between articulating bones or body regions; movement in a sagittal plane takes a limb forward
from anatomical position.
Lateral Flexion: for the trunk or neck, movement in the frontal plane away from the median also called side bending.
Adduction: to pull toward the midline, a movement in a frontal plane that takes a part of the body towards the midline.
Abduction: to pull away from midline, movement in a frontal plane that takes a part of the body away from midline.
Lateral Rotation: a movement in a transverse plane that takes a part of the body outward; or lateral (outward) movement on a limb's
Medial Rotation: movement in a transverse plane that takes a part of the body inward; or medial (inward) movement on a limb's long
Pronate: turn the ventral side down, e.g. forearm - palm of the hand faces backward.
Supinate: turn the ventral side up, e.g. forearm - palm faces forward.
Constrict: close or contract a circular muscle.
Dilate: open or relax a circular muscle.
Protract: drag forward in the horizontal plane.
Retract: drag back in the horizontal plane.
TECHNIQUE! As you make the first incision, pull up on the free edge of the skin with a pair of forceps. Go deeply enough to
see the yellowish muscle tissue clearly. If you are too shallow, you will only see the connective tissue of the dermis & the fascia that
covers the muscles. Shark skin is thin, it is easy to cut through the ventral body wall, so be careful. Once you are at the right "depth"
use the forceps to pull or peel the skin back from the muscle. Use a blunt probe to separate the skin from the muscle tissue if you can. If
necessary, cut the white fascia while pulling tightly on the skin to lift the fascia off the muscle before you cut. In general, remove skin in
the same direction as the pattern of the muscle fibers. You will be less likely to tear muscles.
Step 1: Midventral, near posterior border of pectoral fins
Begin on the ventral body wall, between the pectoral fins, this is usually easy to skin. As your skill improves, you will reach the more
difficult parts of the body. Make a short, very thin, transverse incision in line with the posterior border of the pectoral girdles. Thin means
a few mm only. Lift up the skin & then start a mid-sagittal incision so you have a corner of skin to pull on. Thus you can "peel" back the
skin on the right & left sides of the ventral body wall in this region easily. You will be exposing the hypaxial myotomes that form the
ventral longitudinal bundle, are in series down the abdomen.
Muscle Body Region Relative location in that Region Origin & Insertion Actions
Hypaxial myomeres: ventral trunk, caudal mid-ventral o: myosepta lateral undulation, support
longitudinal bundles i: post. myosepta viscera
Superficial, Anterior Superficial, Posterior
Step 2: Pectoral fin
Cleaning the dorsal & ventral sides of 1 pectoral fin is relatively easy. We’ll wait & do pelvic fins with the reproductive system.
Just follow the orientation of the muscle fibers as you pull. Don’t pull so hard that the pectoral muscles pull off of the body wall.
Muscle Body Relative location Origin & Insertion Actions
Region in that Region
Pectoral pectoral fin dorsal, superficial o: scapular portion of scapulocoracoid extend or abduct
extensors i: dorsal side of pterygiophores pectoral fin
Pectoral Extensor Pectoral Flexor
Pectoral pectoral fin ventral, superficial o: coracoid portion of scapulocoracoid flex or adduct pectoral fin
flexors i: ventral side of pterygiophores
Pelvic pelvic fin dorsal, superficial o: trunk myomere, ischiopubic bar extend or abduct pelvic
extensors i: dorsal side of pterygiophores fin
Pelvic Extensor Pelvic Flexor (deep to siphon on male shark)
Pelvic pelvic fin ventral superficial o: ischiopubic bar flex or adduct pelvic fin
flexors i: ventral side of pterygiophores
Step 3: Chest, gills & throat
When you near the throat, you will find a pair of large, triangular shaped muscles called the coracoarcuals. Anterior to the
coracoarcuals, the muscle fibers run transversely across the jaws from right to left, forming the intermandibularis. You will need to
change directions & perhaps make a new incision to clean this muscle. You don't need to remove all of the skin that covers the gill slits.
Just remove enough so you can ID the ventral superficial constrictors. We may have half of the class stop their dissection of the
throat after these superficial muscles are exposed, because the intermandibularis must be cut to see the other muscles in this region.
Get help from a TA before you start exposing the interhyoideus & other branchial muscles. The interhyoideus is another thin sheet just
beneath the intermandibularis, but the two muscles are difficult to separate. The fibers of the interhyoideus run at slightly different angles
to the intermandibularis. The mid-ventral raphe is continuous with a sheath of connective tissue that encloses the very thin, whitish
coracomandibularis. The fibers of the coracomandibularis run anteriorly-posteriorly & it attaches to the middle of the coracoarcuals.
This is the easiest muscle to miss or destroy because of this sheathing. Deep to the coracomandibularis lie the large, paired,
Muscle Body Relative location in that Region Origin & Insertion Actions
Ventral constrictors branchial lateral, superficial, below gill slits o: ventral gill raphe compress gills
(vc) i: next ventral raphe
Coracoarcuals chest superficial; paired; posterior to o - coracoid of depress Meckel’s cart., expand
(ca) intermandibularis scapulocoracoid oral cavity
i - coracohyoid ms.
Intermandibularis throat superficial; transverse across lower o: Meckel’s cart. elevate floor of mouth,
(im) jaws i: mid-ventral raphe compress oral cavity
Superficial, Anterior Superficial, Anterior
ca vc vc ca
Interhyoideus throat deep to intermandibularis o: hyoid arch compress gills
(ih) i: midventral raphe
Coracomandibularis throat deep to interhyoideus, anterior to o: coracoarcuals depress Meckel's cart. (open mouth)
(cm) coracoarcuals, i: Meckel's cart.
Coracohyoideus hyoid paired; deep to o: coracoarcual ms. depress Meckel's cart.; depress hyoid
(ch) coracomandibularis i: hyoid arch
ch cm ch
Step 4: Lateral side of jaw & head
The adductor mandibulae is the largest of the muscles here. It cleans relatively easily, but it does have lots of connective tissue &
nerves running over it. Try to get this region clean enough to see the muscle fibers. The levator hyomandibulae is dorsal to the
adductor mandibular & forms a thin sheet along the side of the head. The other muscles can only be seen by shaving away part of the
top of the neurocranium between the spiracle & the orbit. Do this gradually so that you don’t cut the muscles. Both the spiracularis and
the levator palatoquadrati are on the anterior to the spiracle. The spiracularis is smaller & posterior to the levator palatoquadrati. Look
at the TA shark first to see where these muscles are located.
Muscle Body Relative location in that Origin & Insertion Actions
Adductor mandibulae head lateral, superficial o: palatoquadrate elevate Meckel's cartilage
(am) i: Meckel's cart. (close jaws)
Levator hyomandibulae head lateral, superficial o: otic capsule compress gills
(lh) i: hyomandibular
sp lh sp lh
Levator palatoquadrati head lateral, deep to fascia, o: otic capsule elevate palatoquadrate
(lp) anterior to spiracularis i: palatoquadrate
Spiracularis head lateral, deep to fascia, just in o: otic capsule elevate palatoquadrate
(sp) front of spiracle i: palatoquadrate
Cucullaris branchial lateral, superficial o: epaxial fascia elevate scapulocoracoid
(cc) i: scapular process on
Dorsal constrictors branchial lateral, superficial, above o: dorsal gill slit raphe compress gills
(dc) gills i: post., dorsal gill raphe
Lateral view Lateral view
dc dc dc
dc dc dc dc
Step 5: Dorsal to the gills
Put a new blade on your scalpel if you have not done so yet. The skin acts like sandpaper because of the small placoid scales & it
quickly dulls your blades. The epaxial myomeres that form the dorsal longitudinal bundle are the most challenging to skin. The
muscles have large tendons that attach to the skin & the muscle fibers change direction frequently. Work slowly & carefully. Pull the
skin to lift the fascia & then cut the line between the muscle & the raised skin, cut into the white fascia. If you cut the muscle, you aren't
pulling up enough on the skin or you are cutting too deep. If you don’t remove enough of the fascia, you won’t see the muscle fibers. If
you run into trouble (cutting deep into muscle, you may need to change directions or start at a new point to get back on track. Be
particularly careful of the cucullaris, a triangular muscle below the myomeres & just above the gills. The dorsal constrictors muscle
fibers run between gill raphes. These are very thin sheets & tear easily, so don’t try to expose these muscles down to the top of the gill
slits. When you are posterior to the cucullaris, you will see the hypaxial myomeres that form the lateral longitudinal bundle. The
lateral bundle is a narrow strip with fibers that run laterally along the body, simpler than the dorsal longitudinal bundle. The lateral
longitudinal bundle is dark because it is composed of red muscle fibers.
Muscle Body Relative location in that Origin & Insertion Actions
Epaxial myomeres: dorsal trunk, tail lateral & then to dorsal o: myosepta lateral undulation; white fibers
longitudinal bundle midline, above lateral line i: post. myosepta
Hypaxial myomeres: lateral trunk, tail below epaxial myomeres & o: myosepta lateral undulation; red fibers
longitudinal bundle below lateral line i: post. myosepta
Lateral view, past pectoral fin
hypaxial lateral longitudinal bundle
Dark regions show red muscle distribution Transverse section through tail
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