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McKinley/O’Loughlin
Human Anatomy, 2nd Edition
CHAPTER 11
Answers to “What Did You Learn?”
1.
The muscles of facial expression originate either in the superficial fascia or
on the surface of the skull.
2.
The pairs of extrinsic eye muscles include: (1) inferior and superior rectus
muscles, (2) lateral and medial rectus muscles, and (3) inferior and superior
oblique muscles. The superior rectus muscles move the eyes superiorly and
medially while the inferior rectus muscles move the eyes inferiorly and medially.
The medial rectus muscle pulls the eye medially (adducts the eye). The lateral
rectus muscle pulls the eye laterally (abducts the eye). The superior oblique
depresses the eye and turns the eye laterally.
3.
Depressor anguli oris pulls the corners of the mouth inferiorly
4.
The lateral and medial pterygoid muscles protract the mandible and move it sideto-side during chewing. The medial pterygoid also elevates the mandible.
5.
The left and right genioglossus muscles protract (stick out) the tongue.
6.
The suprahyoid muscles are the digastric, mylohyoid, geniohyoid and stylohyoid.
These muscles elevate the hyoid bone during swallowing and speaking.
7.
The sternocleidomastoid causes lateral flexion of the neck and rotation of the head
to the opposite side.
8.
The erector spinae is the largest muscle mass in the back. The muscles of the
erector spinae consist of three groups of muscles: iliocostalis [located laterally],
longissimus [located intermediately], and spinalis [located mediallyThe muscles
of the erector spinae are used to maintain posture and help us stand erect.
McKinley/O’Loughlin
9.
Human Anatomy, 2nd Edition
The external intercostal muscles elevate the ribs during inspiration. The internal
intercostals depress the ribs, but only during a forced expiration; a normal
exhalation takes no active muscular effort.
10.
The muscle of respiration that separates the thoracic and abdominal cavities is the
diaphragm. The structure to which all diaphragm muscle fibers converge is called
the central tendon.
11.
The muscles of the abdominal wall include: the external oblique, internal oblique,
transversus abdominis, and rectus abdominis.
Answers to “Content Review”
1.
Many muscles are used to smile. Levator anguli oris, zygomaticus major and
zygomaticus minor elevate the corners of the mouth. Risorius contracts as well if
you make a closed-mouth smile. The depressor anguli oris muscle contracts when
you frown, pulling the corners of the mouth inferiorly. If you frown and pout as
well, that also requires contraction of the depressor labii inferioris, mentalis, and
platysma.
2.
The extrinsic muscles of the tongue originate on head and neck structures and
insert on the tongue. The left and right genioglossus muscles originate on the
mandible and protract when you stick out your tongue. The styloglossus muscles
elevate and retract the tongue (pull the tongue back into the mouth), while the
hyoglossus muscles depress and flatten the tongue. The palatoglossus muscles
originate on the soft palate and elevate the posterior portion of the tongue.
McKinley/O’Loughlin
3.
Human Anatomy, 2nd Edition
Contraction of the superior or inferior rectus muscle moves the eye in the
direction indicated by the muscle’s name. However, neither the superior nor the
inferior rectus muscles pull directly parallel to the long axis of the eyeball; thus,
both muscles also move the eye slightly in the medial direction. So, the superior
rectus muscles move the eyes superiorly and medially, while the inferior rectus
muscles move the eyes inferiorly and medially.
4.
When food enters the pharynx, the three pharyngeal constrictors (superior,
middle, and inferior) contract sequentially to initiate swallowing and force the
food bolus inferiorly into the esophagus.
5.
The suprahyoid muscles are located superior to the hyoid bone, and the infrahyoid
muscles are located inferior to the hyoid bone. The suprahyoid muscles are
associated with the floor of the mouth. In general, these muscles o elevate the
hyoid bone during swallowing and speaking. The infrahyoid muscles contract
will either depress the hyoid bone or depress the thyroid cartilage of the larynx.
6.
Bilateral contraction of the splenius muscles extends the neck, whereas the
unilateral contraction of just one sternocleidomastoid muscle results in a lateral
flexion of the neck and rotation of the head to the same side.
7.
The muscle fibers of the diaphragm converge toward a central tendon. This is a
strong aponeurosis that functions as the insertion tendon for all peripheral muscle
fibers of the diaphragm. When the diaphragm contracts, the central tendon is
pulled inferiorly toward the abdominal cavity, which increases the vertical
dimensions of the thoracic cavity.
McKinley/O’Loughlin
8.
Human Anatomy, 2nd Edition
The external and internal oblique muscles laterally flex the vertebral column
(bend the body laterally) and rotate the vertebral column to the opposite side, if
they contract unilaterally. If these muscles bilaterally contract, they compress the
abdominal wall and flex the vertebral column
9.
Each rectus sheath is formed from the aponeuroses of the external oblique,
internal oblique, and transversus abdominis muscles. The linea alba serves as a
connecting region between the left and right rectus sheaths.
10.
The pelvic diaphragm muscles form the pelvic floor and support the pelvic
viscera. These muscles include coccygeus, the external anal sphincter, and the
levator ani (iliococcygeus, pubococcygeus and puborectalis.)