Gallbladder is lined by the columnar epithelium with brush border (irregularly placed microvilli).

Q4. An early term embryo spontaneously aborts due to incomplete
lateral body wall folding and failure of the primitive paired
endocardial tubes to merge and form the primitive heart tube.
The endocardial tubes are derived from which of the following
embryonic sources?

Cardiac progenitor cells migrate from the epiblast into the cranial portion of the
splanchnic layer of the lateral plate mesoderm. In the mesoderm,
the progenitor cells ultimately form paired cardiac primordia,
that is, the endocardial tubes. Subsequent lateral and
cephalocaudal folding of the embryo causes merging of the
paired endocardial tubes plus caudal shifting of the primitive
heart tube and pericardial cavity. Choice A (Paraxial mesoderm)
is incorrect. The paraxial mesoderm segments into
somites along the long axis of the body wall. Each somite
ultimately differentiates into three portions: sclerotome, myotome,
and dermatome. Choice B (Intermediate mesoderm)
is incorrect. The intermediate mesoderm is the small portion
of mesoderm that connects the paraxial and lateral plate
mesodermal areas. It differentiates into urogenital organs.
Choice D (Parietal mesoderm) is incorrect. The lateral plate
mesoderm splits into parietal (somatic) and visceral (splanchnic)
parts, separated by the intraembryonic body cavity. The
parietal layer becomes associated with the overlying ectoderm
to form the lateral body wall folds. Choice E (Extraembryonic
mesoderm) is incorrect. This cell population appears outside
the embryonic body proper. It forms a loose connective tissue
zone that eventually results in the chorionic cavity.

Q5 Diagram of fourth ventricle is given with the facial colliculus
marked. Damage to the structure producing the elevation
marked leads to paralysis of which of the following muscle?

• Facial colliculus is a rounded elevation formed by the axons of facial nerve (and not by the abducent nucleus deep to it).
• Damage to the facial nerve axons paralyses muscles of facial expression like risorius.

In this patient, herpes
zoster, or shingles, is a painful skin rash affecting the dermatome
distribution pattern of the left 10th thoracic (T10)
nerve, as evidenced by the involvement of the umbilicus.
Shingles is seen in patients who have had previous exposure
to the varicella zoster virus, which causes chickenpox in children
or young adults. After the initial exposure to chickenpox,
this virus can reside latent in ganglia of an individual for years.
If this individual becomes immunocompromised, the skin (or
dermatomes supplied by the infected ganglia) can develop
shingles, a painful skin rash, which blisters, breaks open,
crusts over, and then disappears. In this patient, the herpetic
lesions were found in the sensory distribution of the left T10
nerve, which means the virus resides in this nerve’s sensory
ganglion, or the spinal ganglion of T10. Remember that two
types of ganglia exist: sensory (afferent) and autonomic. The
sensory ganglia, which are most often affected by shingles, are
equivalent to the spinal (dorsal root) ganglia of spinal nerves
in that they house typical pseudounipolar cell bodies of afferent
neurons and do not contain synapses. If a spinal ganglion
were infected by the varicella zoster virus, shingles may present
in its dermatome distribution patterns when the patient is
immunocompromised. Choice A (Paravertebral ganglion) is
incorrect. The paravertebral (sympathetic) ganglia are located
within the sympathetic trunk. They receive efferent fi bers
from the presynaptic (preganglionic) sympathetic neuro originating in the intermediolateral (IML) cell column of the
thoracic and upper lumbar segments (T1-L2). Due to their
location, these sympathetic ganglia are called paravertebral
ganglia. Before it causes shingles (or herpes zoster), the varicella
zoster virus resides latent in sensory ganglia for many
years. Because the paravertebral ganglia are autonomic ganglia,
it is unlikely they would be responsible for the skin rash
in this patient. Choice B (Prevertebral ganglion) is incorrect.
The prevertebral ganglia are sympathetic ganglia that receive
their name as they are located anterior to the vertebral column,
as distinguished from the ganglia of the sympathetic trunk
(paravertebral ganglia). Prevertebral ganglia exist near major
branches of the abdominal aorta in the abdominopelvic cavity.
These ganglia send postsynaptic (postganglionic) sympathetic
fi bers to the abdominopelvic organs with periarterial plexuses.
Before it causes shingles (or herpes zoster), the varicella zoster
virus resides latent in sensory ganglia for many years. Because
the prevertebral ganglia are autonomic ganglia, it is unlikely
they would be responsible for the skin rash in this patient.
Choice C (Lumbar ganglion) is incorrect. The lumbar ganglia
are paravertebral ganglia located in the abdominopelvic part
of the sympathetic trunk. Before it causes shingles (or herpes
zoster), the varicella zoster virus resides latent in sensory ganglia
for many years. Because the lumbar ganglia are autonomic
ganglia, it is unlikely they would be responsible for the skin
rash in this patient. Choice E (Spinal ganglion of L2) is incorrect.
The spinal (posterior root) ganglion is a sensory ganglion,
so it could be infected by the varicella zoster virus and present
with a painful, skin rash along its dermatome distribution pattern.
The sensory distribution of L2 would extend along the
back, hip, and extend into the anterior and medial aspects of
the thigh. Because this patient presents with a skin rash at the
level of the umbilicus, the spinal ganglion of T10 would be the
source of this painful skin rash

Q7) A 27-year-old man was admitted to the emergency
department after an automobile collision in which he
suffered a fracture of the lateral border of the scapula.
Six weeks after the accident, physical examination reveals
weakness in medial rotation and adduction of the
humerus. Which nerve was most likely injured?

Lower subscapular nerves arise from the cervical
spinal nerves 5 and 6. It innervates the subscapularis
and teres major muscles. The subscapularis and
teres major are both responsible for adducting and
medially rotating the arm. A lesion of this nerve
would result in weakness in these motions. The axillary
nerve also arises from cervical spinal nerves 5
and 6 and innervates the deltoid and teres minor
muscles. The deltoid muscle is large and covers the
entire surface of the shoulder, and contributes to arm
movement in any plane. The teres minor is a lateral
rotator and a member of the rotator cuff group of
muscles. The radial nerve arises from the posterior
cord of the brachial plexus. It is the largest branch,
and it innervates the triceps brachii and anconeus in
the arm. The spinal accessory nerve is cranial nerve
XI, and it innervates the trapezius muscle, which elevates
and depresses the scapula. The ulnar nerve arises from the medial cord of the brachial plexus and
runs down the medial aspect of the arm. It innervates
muscles of the forearm and hand.

The lateral pterygoid
muscle acts on the temporomandibular joint (TMJ) to cause
protrusion (or protraction) of the mandible. During the contraction
of the lateral pterygoid muscle, the mandibular condyle
slides anterior (translation) to be located inferior to the
articular eminence of the temporal bone, which enables the
mouth to open passively due to gravity. Acting unilaterally,
the lateral pterygoid muscle produces side-to-side movements.
So, the patient has all of the signs of a paralyzed lateral
pterygoid muscle on the left side, including weakness protruding
the mandible, weakness opening the oral fi ssure (or
mouth), and the lateral deviation of the mandible during protrusion.
In this patient, herpes zoster, or shingles, is a painful
skin rash affecting the mandibular division (or motor root)
of the trigeminal nerve (CN V3). Shingles is seen in patients
who have had previous exposure to the varicella zoster virus,
which causes chickenpox in children or young adults. After
the initial exposure to chickenpox, this virus can reside latent
in ganglia of an individual for years. If this individual becomes
immunocompromised, the skin (or dermatomes supplied
by the infected ganglia) can develop shingles, a painful skin
rash, which blisters, breaks open, crusts over, and then disappears.
In this patient, the herpetic lesions were found in the
sensory distribution of the left CN V3, which means the virus
resides in the trigeminal (or semilunar) ganglion. This herpes
zoster infection also affected the motor root of CN V3, which
is why the lateral pterygoid muscle displayed weakness in this
patient. Choice A (Anterior belly of digastric) is incorrect. The
anterior belly of the digastric muscle is a suprahyoid muscle
that assists in the elevation of the hyoid bone during swallowing.
It has no role in the deviation of the mandible during
protrusion. Choice C (Masseter) is incorrect. The masseter
primarily works to close the jaw. Though its superfi cial fi bers
may play a limited role in protrusion of the mandible, it is the
deviation of the mandible to the left that signals involvement
of the left lateral pterygoid muscle. Choice D (Medial pterygoid)
is incorrect. The medial pterygoid functions to elevate
the mandible. Though it may play a limited role in protrusion
of the mandible, it is the deviation of the mandible to the left
that signals involvement of the left lateral pterygoid muscle.
Choice E (Temporalis) is incorrect. The temporalis muscle is
also involved with elevation of the mandible leading to closure
of the jaw; however, its middle and oblique fi bers are the primary
retractors of the mandible. These actions did not display
weakness in this patien

The anterior
longitudinal ligament is a vertical connective tissue band that
attaches along the anterior aspects of the vertebral bodies. Its
peripheral fi bers have strong attachments to the intervertebral
discs. The anterior longitudinal ligament resists hyperextension
of the vertebral column. However, in this patient, the
extreme forces involved with the hyperextension of the neck
overpowers the resistance of this ligament, rupturing it as well
as displacing part of the C4-5 intervertebral disc. In the given
T2-weighted MRI, the anterior longitudinal ligament is represented
by a hypointense (dark band) signal located anterior to
the vertebral column. However, the locations where the anterior
longitudinal ligament is interrupted appear as an abnormal
hyperintense (white) signal, which is evident anterior to the C5 vertebral body. Choice B (Posterior longitudinal ligament)
is incorrect. The posterior longitudinal ligament runs vertically
along the posterior aspect of the vertebral column,
mirroring the position of the anterior longitudinal ligament
located along the anterior aspect of the vertebral column. The
posterior longitudinal ligament resists fl exion of the vertebral
column. Posterolateral herniation of the gelatinous nucleus
pulposus through the anulus fi brosus of an intervertebral
disc most often projects lateral to the strong attachment sites
of the posterior longitudinal ligament. If the herniated disc
compresses spinal nerve roots, then neck, back, and/or limb
pain may be present. The T2-weighted MRI clearly shows disruption
of the anterior longitudinal ligament, evident by the
abnormal hyperintense (white) signal located anterior to the
C5 vertebral body. Choice C (Ligamentum fl avum) is incorrect.
The ligamenta fl ava (L: yellow ligament) are paired ligaments
of yellow elastic fi brous tissue, which bind together
the laminae of adjoining vertebrae and form the posterior
wall of the vertebral canal. Because these ligaments resist
fl exion of the vertebral column, it is unlikely the ligamenta
fl ava were damaged in this hyperextension injury of the neck.
Choice D (Interspinous ligament) is incorrect. The interspinous
ligament is composed of fi brous bands that connect
the spinous processes of adjacent vertebrae. Because these
ligaments resist fl exion of the vertebral column, it is unlikely
the interspinous ligaments were damaged in this hyperextension
injury of the neck. Choice E (Intertransverse ligament)
is incorrect. The intertransverse ligament is one ligament
that connects the transverse processes of adjacent vertebrae.
Because the intertransverse ligaments resist contralateral bending
(abduction; lateral fl exion) of the vertebrae, it is unlikely
the intertransverse ligaments were damaged in this hyperextension
injury of the neck.

Q10) A radiologist orders a posteroanterior (PA) plain fi lm of the
chest. This image should provide the greatest resolution of
which of the following structures?

The PA plain fi lm is the standard
radiographic view of the thorax, and probably the most
commonly obtained medical image. In basic terminology, a
PA radiograph is one in which the X-ray beam penetrates from
the patient’s posterior side to the anterior side, as shown in
the given illustration. The X-ray projector is located posterior
to the patient, and the X-ray fi lm is positioned anterior. The
part of the body under study should be as close as possible to
the X-ray fi lm in order to optimize the resolution of that part
and minimize magnifi cation artifacts. Thus, in the PA orientation,
the heart is closest to the X-ray fi lm and appears sharper
than the other structures in question. Choice A (Transverse
processes of the vertebrae) is incorrect. In the PA orientation,
the vertebral column (being in the posterior aspect of
the body) is further away from the X-ray fi lm. Also, the vertebrae
are in line with several other overlapping structures (e.g., the heart, esophagus, and aorta) that add rad

Q11) A research scientist at a pharmaceutical company discovers a
new drug that selectively blocks the release of norepinephrine
from nerve endings. At which of the following sites would this
drug have the greatest effect on normal synaptic transmission?
(A) Somatic neuron motor end plates
(B) Postsynaptic parasympathetic nerve terminals
(C) Postsynaptic sympathetic nerve terminals
(D) Synapses between presynaptic and postsynaptic parasympathetic
neurons
(E) Synapses between presynaptic and postsynaptic sympathetic
neurons