📚 Question Bank

The cross-section shown in the image is at the level of T3-T4.

The cross-section shows a large vascular opening of the arch of the aorta, along with three small openings corresponding to the brachiocephalic trunk, left common carotid artery and left subclavian artery. This suggests that the section was taken at the level between T3 and T4.

The inability to abduct the arm is most likely due to a lesion of the C5 root.

The deltoid muscle is the main muscle involved in the abduction of the arm. It is innervated by the C5 root of the axillary nerve. So, a lesion involving the C5 causes inability to abduct the arm.

The table below shows the movements and muscles tested to determine the location of the lesion in the upper limb.

Arm movement Shoulder abduction Elbow extension Elbow flexion

Radial wrist extenso r

Finger extensors Finger flexors

Finger abduction

Muscle Deltoid Triceps

BicepsBrachioradialis

Extensor carpi radialis longu s

Extensor digitorum

Flexor pollicis longus and fle xor digitorum profundus, ind exFlexor digitorum profundu s, ring and little

First dorsal interosseusAbdu ctor pollicis brevis

Root C5 C7

C5/6 C6

C6

C7

C8C

T1T1

Nerve Axillary Radial

MusculocutaneousRadial Radial

Posterior interosseus

Anterior interosseousUlna r

UlnarMedian

The thickened nerve marked with the arrow in the above image is the great auricular nerve and the thickened nerve visible below the great auricular nerve is the transverse cervical nerve.

Nerve thickening in this case is likely to be due to leprosy.

Great auricular nerve:

It is the largest ascending branch of cervical plexus and arises from the second and the third cervical spinal nerves.

It winds over the posterior border of the sternocleidomastoid muscle and ascends upwards. On reaching the parotid gland it divides into the anterior and posterior branches:

• Anterior branch - supplies the facial skin over the parotid gland and joins the facial nerve in
• the gland.
• Posterior branch - supplies the skin over the mastoid process, posteroinferior part of the
• auricle, lobule, and concha.

Clinical considerations:

• Leprosy - Nerve thickening is present. The nerve is palpable over the upper part of the sternocleidomastoid muscle. (as seen in the above image)
• Frey's syndrome - An aberrant connection between the auriculotemporal nerve and great auricular nerve causes gustatory sweating.

Broca’s area is situated in the inferior frontal gyrus.

Broca’s motor speech area (44,45) is located in the inferior frontal gyrus. Wernicke’s area (22) is located in the superior temporal gyrus.

The trochlear nerve nucleus is a part of the general somatic efferent (GSE) column, not the special visceral afferent column.

The trochlear nerve is a motor nerve that innervates superior oblique muscle in the orbit.

The neurons of the general somatic efferent (GSE) column innervate the extrinsic ocular muscles and muscles of the tongue (III, IV, VI, and XII cranial nerves).

The interchondral joint between the attachment of the 8th and 9th rib with the 7th rib is a synovial joint.

Joints in the thoracic cavity are of the following types:

• Synarthrosis - structures are connected by a fibrous band of tissue. E.g, 1st sternocostal joint
• Synchondrosis - primary cartilaginous joints. E.g., costochondral joints
• Symphysis - secondary cartilaginous joints. E.g. manubriosternal and xiphisternal joints
• Synovial joints - the presence of these help the thoracic cavity expand during inspiration. E.g.:
• Interchondral joint
• Sternocostal joint
• Costovertebral joint
• Costotransverse joint
• Note:

The interchondral joint between the 9th and 10th cartilages is never synovial and sometimes absent.

The anterior fontanelle is the last fontanelle to close. It closes at around 18-24 months of age.

• Anterior: Between frontal and parietal bones (Bregma) - Closes at 18-24 months
• Posterior: Sagittal and lambdoid sutures - Closes at 2-3 months
• Mastoid/Posterolateral: Intersection of temporal, parietal, and occipital bones - Closes at 6-18 months

Sibson’s fascia is attached to the inner border of the 1st rib, not the 2nd rib.

Sibson's fascia (suprapleural membrane) serves as a plane of separation between the lower neck and the thorax and covers the apical part of the lung. It is attached to the inner border of the 1st rib and posteriorly to the anterior border of the transverse process of the C7 vertebra. It

is strengthened by a few spreading muscular fibers derived from the scalene muscles. The subclavian vessels lie on top of it.

The vagal trunk does not pass through the aortic opening of the diaphragm. It passes through the esophageal opening at the level of the T10 vertebra.

Structures passing through the aortic opening (T12) are the Aorta, Azygous vein, and Thoracic duct.

The hard palate contains keratinised stratified squamous epithelium, has a submucosa, and contains minor salivary glands.

This keratinised stratified squamous epithelium has regional variations and may be orthokeratinised or parakeratinised (found in the hard palate and gingiva). The bony structure of the hard palate is covered by a firmly attached mucosa in the central part. In the lateral parts, the hard palate also has a submucosal layer containing blood vessels. There are minor mucous type salivary glands in the submucosa in the posterior part of the hard palate.

The muscle marked 'A' is lumbricals and they cause flexion at the metacarpophalangeal joints.

Lumbricals are intrinsic muscles of the hand that flex the metacarpophalangeal joints (MCP) and extend the interphalangeal joints (PIP & DIP). They originate from the flexor digitorum profundus.

• The lateral two are unipennate, supplied by the median nerve.
• The medial two are bipinnate, supplied by the ulnar nerve.

Cricothyroid is a tensor of vocal cords.

The facial nerve is the nerve of the 2nd pharyngeal arch.

Each pharyngeal arch is characterized by its own muscular components. The muscular components of each arch have their own cranial nerve. Wherever the muscle cells migrate, they carry their nerve component with them.

The neurons of the 5th, 7th, 9th, and 10th cranial sensory ganglia that supply the pharyngeal arch structures are derived from ectodermal placodes (epipharyngeal placodes) and from the neural crest cells.

The fibers of the iliopubic tract fan out with fascia iliaca laterally.

The iliopubic tract is a thickening of the transversalis fascia lying immediately posterior to the inguinal (Poupart's) ligament. It extends from the anterior superior iliac spine (ASIS) superolaterally and arches across the front of the femoral sheath.

Attachments:

• Medially, its fibres insert by a broad attachment into the pubic tubercle and pectineal line, behind the conjoint tendon.
• Laterally, its fibres fan out within the fascia transversalis and fascia iliaca without bony attachment to the iliac spines.

Clinical note: It is considered as an important landmark in laparoscopic hernia surgeries.

The ureteric bud develops from the Mesonephric duct.

Intermediate mesoderm develops into the Genital ridge and Nephrogenic cord. The Nephrogenic cord further develops into Pronephros, Mesonephros and Metanephros. The ureteric bud develops from mesonephros which later fuses with the Mesonephric duct. Metanephros proliferates around the ureteric bud which forms metanephric blastema (definitive kidneys).

The heart starts to beat in the 4th week of development.

The movements at the atlanto-axial joint allow a person to look left and right.

The atlanto-axial joints include 3 synovial joints:

• Median atlanto-axial joint - The central pivot joint between the dens of the axis and a ring formed by the anterior arch and transverse atlantal ligament
• Lateral atlanto-axial joints - Plain synovial joints between lateral masses of atlas and upper facets of the body of axis

Movements at the atlanto-axial joint almost exclusively is rotation around the axis, which help side-to-side rotation of the head. The normal range of atlanto-axial rotation is about 40°.

The right coronary artery does not give rise to the circumflex coronary artery.

The right coronary artery arises from the anterior aortic sinus (right coronary sinus) of the ascending aorta. It passes anteriorly and descends vertically in the coronary sulcus between the right atrium and the right ventricle. On reaching the inferior margin, it turns posteriorly and continues in the sulcus onto the diaphragmatic surface and the base of the heart.

The diameter of the right coronary artery is less than that of the left coronary artery. The right conal artery is usually the first branch of the right coronary artery. The circumflex coronary artery is a branch of the left coronary artery and is the exclusive supplier to the right bundle branch.

Omphalocele is protrusion of abdominal contents through the umbilical ring. It is due to failure of physiological hernia to reduce into the abdominal cavity, which results in non-closure of the umbilical ring.

An omphalocele may contain stomach, liver, and intestines. And these contents are enclosed in a sac. Omphalocele is usually associated with other congenital anomalies (e.g., trisomy 13, trisomy 18, or Beckwith-Wiedemann syndrome) and with increased levels of α-fetoprotein.

Note: In gastroschisis, there is an absence of a membranous sac and is paraumbilical.

The marked structure is the internal capsule, which is a form of projection fiber.

The marked structure is the mandibular foramen and the inferior alveolar nerve passes through it.

The inferior alveolar nerve (IAN), a branch of the mandibular nerve (CN V3), descends behind the lateral pterygoid, at the lower border of the muscle, the nerve passes between the sphenomandibular ligament and the mandibular ramus and enters the mandibular canal via the mandibular foramen. The mandibular foramen is located above the mandibular angle, the opening through which the IAN and the vessels of the mandible pass. The IAN continues its course through the mandibular canal and then branches off to supply the lower teeth, gums, and lower lip.

The gall bladder does not form a boundary of the Calot’s triangle. Calot's triangle is bounded by 3C's:

• Medially – Common hepatic duct
• Inferiorly – Cystic duct
• Superior – Cystic artery

The marked dermatome which includes the umbilicus is supplied by T10. The dermatomal distribution of the abdominal region is as follows:

• T7, T8, T9 - supplies skin from the xiphoid process to just above the umbilicus.
• T10 - supplies skin around the umbilicus.
• T11, T12 - supplies skin below the umbilicus upto the suprapubic region.
• L1 - supplies skin around the genitalia and upper medial thigh.

The arrow shows extensor carpi radialis longus.

It originates from the distal third of the lateral supracondylar ridge of the humerus and inserts at the second metacarpal (radial side). It is innervated by the radial nerve, C6, and C7.

The vascular supply is by radial recurrent artery and it is responsible for the extension and abduction of the wrist joint.

The area marked in the image is supplied by radial nerve.