Arrangement of Fascicles
Remember: a fascicle is several
sheathed muscle fibers wrapped
by a coarse fibrous membrane
Arrangement of Fascicles
• Common fascicle patterns:
– Circular
• When fascicles are arranged in concentric rings (sphincters)
– Convergent
• When the fascicles converge to a single insertion
• Triangular or fan-shaped
– Parallel
• The length of the muscle runs parallel to the long axis of the
muscle
• Strap like
Arrangement of Fascicles
• Common fascicle patterns:
– Fusiform
• Modified parallel form
• Has a spindle-shaped muscle
• Has an expanded belly or gastor
– Pennate
• Short fascicles
• Attach obliquely to a central tendon
– Unipennate – insert into one side of the tendon
– Bipennate – inserts into opposite sides of the tendon
– Multipennate – inserts into multiple places of the tendon
Head and Neck Muscles
• Facial Muscles
– Frontalis – covers the frontal bone from the
cranial aponeurosis to the skin of the eyebrow
• Raises the eyebrows
– Occipitalis – covers the posterior aspect of the
skull
• Pulls the scalp
– Orbicularis Oculi – fibers run in circles around
the eyes
• Allows eye closing, squinting, blinking and winking
Frontalis
Frontalis
Occipitalis
Orbicularis Oculi
Orbicularis Oculi
Head and Neck Muscles
• Facial Muscles
– Orbicularis Oris – the circular muscle of the
lips
• Opens the mouth and protrudes the lips (kissing
muscle)
– Buccinator – fleshy, runs horizontally across
the cheek
• Inserts into the orbicularis oris
• Flattens the cheek
• Doubles as a chewing muscle
Orbicularis Oris
Buccinator
Head and Neck Muscles
• Facial Muscles
– Zygomaticus – extends from the corner of the
mouth to the cheek
• “smiling muscle”
• Raises the corners of the mouth
Head and Neck Muscles
• Chewing Muscles
– Buccinator – already mentioned
– Masseter – covers the angle of the lower jaw
• Runs from the zygomatic process of the temporal
bone to the mandible
• Closes the jaw
– Temporalis – fan-shaped, overlying the
temporal bone
• Inserts into the mandible and is a synergist to the
masseter
Masseter
Temporalis
Head and Neck Muscles
• Neck muscles
– Platysma – single sheet-like muscle
• Covers the anterolateral neck
• Originates from the connective tissue of the chest muscle
and inserts in the area around the mouth
• Pulls the corners of the mouth inferiorly
– Sternocleidomastoid – paired muscle
• Two headed muscles, one on each side of the neck
• One head arises from the sternum, the other from the clavicle
• Head fuses before insertion into the mastoid process of the
temporal bone
• Flex the neck
Platysma
Sternocleidomastoid
Trunk Muscles
• Divided into Anterior and Posterior
muscles
– Anterior
• Pectoralis Major – large fan-shaped muscle
covering the upper part of the chest
• Origin is in the sternum, should girdle, and first 6
ribs
• Insertion is on the proximal end of the humerus
• Flexes the arm
Trunk Muscle
– Anterior Muscles
• Intercostal Muscles – deep muscles of the ribs
– External intercostal muscles are used in breathing
» Raise the rib cage (air in)
– Internal intercostal muscles deeper than the external
– Used in breathing
» Lower the rib cage (air out)
• Muscles of the Abdominal Girdle – reinforce the body trunk
– Consists of : rectus abdominis, external and internal obliques,
and transverse abdominis.
– Look like plywood
– Muscles run in different directions
Intercostal Muscles
Trunk Muscle
– Anterior
• Rectus oblique – strap-like muscles
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Most superficial muscles of the abdomen
Run from the pubis to the rib cage
Flex the vertebral column
Depress the abdomen during defecation and child birth
• External oblique – paired superficial muscles
– Make up the lateral walls of the abdomen
– Fibers run downward and medially from the ribs to the
illium
– Flex the vertebral column, and rotate the trunk
Trunk Muscles
– Anterior
• Internal oblique – paired muscles
– Deep to the external obliques
– Fibers run at right angles to those of the external
obliques
– Rise out of the iliac crest and insert into the last 3 ribs
• Transversus abdominis – deepest muscle of the
abdomen
– Fibers run horizontally across the abdomen
– Arises from the lower ribs and iliac crest
– Inserts into the pubis
Internal Oblique
Trunk Muscles
• Posterior Muscles
– Trapezius
• Most superficial muscles of the posterior neck and
upper trunk
• Together form a diamond shape
• Have a broad origin
– From the occipital bone of the skull to the end of the
vertebral column
– Flare to insert into the scapular spine and clavicle
Trunk Muscles
• Posterior Muscles
– Latissimus Dorsi
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Large flat muscle pair which covers the lower back
Origin is in the lower spine and ilium
Inserts into the proximal end of the humerus
Extends and abducts the humerus
Trunk Muscle
• Posterior Muscle
– Erector Spinae
• Back extension prime mover
• Deep muscles of the back
• Have 3 muscle columns
– Longissimus
– Iliocostalis
– Spinalis
» They span the entire length of the vertebral column
» They are back extensors and help bending at the
waist
Trunk Muscles
• Posterior Muscles
– Deltoid
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Fleshy triangular shaped
Form the shoulder
Origin is in the spine of the scapula to the clavicle
Insertion is at the proximal end of the humerus
Prime mover of arm abduction