📚 Question Bank

The pylorus consists of mainly mucus-secreting glands.

The gastric glands can be divided into 3 groups which are namely:

• Principal gastric glands - They are found in the body and fundus. About 3-7 principal glands open into the gastric pit. These glands contain at least 5 different types of cells:
• Chief cells
• Parietal cells
• Mucous neck cells
• Neuroendocrine cells
• Stem cells.
• Cardiac gastric glands - They are found in the small area near the cardiac orifice. Some are simple tubular glands, others are compound branched tubular. They contain mucus-secreting cells predominantly. Parietal and chief cells are sparsely present.
• Pyloric gastric glands - Found in the pyloric antrum. About 2-3 convoluted tubes open into deep gastric pits. They mainly have mucus-secreting cells. They also have neuroendocrine cells, especially gastrin-secreting G cells. Parietal and chief cells are scarce.

Brunner's glands (or duodenal glands) are compound tubular submucosal glands present in the upper duodenum (above the sphincter of Oddi).

The alveoli of duodenal glands are lined mostly by mucous secreting columnar cells. Their ducts pass through the muscularis mucosae and empty into the intestinal crypts (of Lieberkuhn).

The duodenum can be easily differentiated from the jejunum or ileum by the presence of these submucosal glands. The jejunum and ileum do not have glands in their submucosa.

Given below is the histological section of normal duodenum showing the Brunner's glands at the submucosal layer.

Centroacinar cells are mainly present in the pancreas.

Centroacinar cells are present in the alveoli of the exocrine pancreas. They are called so because they are visible near the centre of the acinus (or alveolus). These cells actually are actually part of the intercalated ducts that are invaginated into the secretory elements of the pancreas.

The space of Disse consists of all of the following mentioned above except Kupffer cells. They are present in the lining of the walls of the sinusoids, not in the Space of Disse (perisinusoidal space).

Kupffer cells are also known as stellate macrophages or Kupffer-Borowicz cells. They are specialized macrophages present in the liver and are part of the mononuclear phagocyte system.

Space of Disse or the perisinusoidal space is present in the liver between the hepatocyte and a sinusoid. This space contains the blood plasma. The microvilli of hepatocytes extend into this space. This allows absorption of proteins and other plasma components from the sinusoids by the hepatocytes. This space may also have some fat cells.

The sinusoids are present in all the above-mentioned structures except kidneys. They are present in:

• Liver
• Spleen
• Lymph nodes
• Endocrine glands (adrenal medulla, parathyroid)
• Bone
• Carotid body

The given image is a graphical representation of sinusoids (sinus-like) which are small blood channels formed by subdivision of the lumen of large blood vessels (sinuses) by the invasion of developing parenchymal cell-cords.

The image shows the histological section of the epidermis. The structures marked are respectively:

• Stratum corneum
• Stratum granulosum
• Stratum spinosum
• Stratum basale

The above 4 layers are present in the thin hairy skin.

The thick glabrous skin over the palms and the soles alone contains a clear homogenous 5th layer between the stratum corneum and stratum granulosum, called the stratum lucidum.

Among the given options, the region marked X points towards the location of intercellular adhesions formed by desmosomes.

Desmosomes (maculae adherens) are specialized adhesive protein complexes that localize to intercellular junctions. They are responsible for maintaining the mechanical integrity of tissues and resisting shearing forces. They are made of intercellular filaments, dense cytoplasmic plaques within the cells on either side and intermediate filaments.

Hemidesmosomes are specialized structures for the cell to extracellular material adhesions.

The schematic representation shows the desmosomal proteins and relative distance from the plasma membrane. The desmosomal cadherins, the desmogleins and desmocollins, extend into the intercellular space and outer dense plaque to establish contact and adhere to neighbouring cells. The cadherin cytoplasmic tails associate linker proteins, plakoglobin, plakophilins, and desmoplakin. The desmoplakin binds to keratin intermediate filaments within the inner dense plaque, serving to tether the intermediate filaments to the plasma membrane.

The structure marked X in the histological image of the skin is the Meissner's corpuscle which is located in the papillary dermis.

Each corpuscle consists of a connective tissue capsule and a central core composed of a stack of flat modified Schwann cells (Coiled spring-like morphology). They are present in the dermal papillae of all parts of hands and foot, anterior aspect of the forearm, lips and mucous membrane of the apical part of the tongue.

They are rapidly acting mechanoreceptors and are specialised for light touch and low-frequency stimuli. They are sensitive to shape and textural changes and provide the neural basis for reading Braille text.

The histological image below shows Meissner's corpuscles in the dermal papillae.

Panniculus adiposus is present in the axilla.

Panniculus adiposus refers to a layer/sheet of fat present subcutaneously and is found over most of the body except the scrotum, penis, and eyelids. It is responsible for giving a smooth contour to the skin.

From the given options, the correct sequence from outer to inner is:

• retinal pigment epithelium (A),
• external limiting membrane (E),
• inner nuclear layer (D),
• inner plexiform layer (B),
• nerve fiber layer (C)

The gelatinous component of the crista ampullaris that extends from the crista to the roof of the ampullae is known as the cupula.

The ampullary cupula, or cupula, provides a sense of spatial orientation. It is located in each of the ampullae of the three semicircular canals. In the crista ampullaris, hair cells that have several stereocilia associated with each kinocilium, are embedded into the gelatinous matrix of the cupula in a specific pattern that is functionally significant. The lag of endolymph on the rotational movement of the head deflects the cupula and hence stimulates the hair cells.

The pattern of the arrangement of cranial nerve nuclei from the ventral to dorsal aspect is: Somatic Efferent gt; Visceral Efferent gt; Visceral Afferent gt; Somatic Afferent

The basal and alar cranial nerve nuclei of the brainstem are organized into 7 columns. The sequence of the columns from ventral to dorsal is shown in the image below - 3 motor columns in the ventral basal plate (green) and 4 sensory columns in the dorsal alar plate (blue). The visceral nuclei are closer to the sulcus limitans than the somatic nuclei.

Excruciating pain is the principal symptom of trigeminal neuralgia. The afferent fibers carrying pain and temperature from the face relay in the spinal nucleus of the trigeminal nerve. It extends from the chief sensory nucleus in the upper part of the pons through the medulla and into the upper 2 segments of the spinal cord.

The trigeminal nerve consists of 4 nuclei: 3 sensory (mesencephalic, spinal, and principal sensory nucleus) and 1 motor.

Nucleus Mesencephalic nucleus

Principal sensory nucleu s

Spinal nucleus

Motor nucleus

Location

Composed of a column ofuni polar nervecells situated in th e midbrain and extends inferi orly into the pons as far as th e main sensory nucleus

Posterior part of the pons lat eral to the motor nucleus

Continuous superiorly with t he main sensory nucleus and extends inferiorly the whole of the medulla oblongatatill t he 2ndcervical segment

The pons medial to the main sensory nucleus

Function

Receives the sensation ofpro prioceptionfrom the muscles of mastication and from the f acial and extraocular muscles

Receives the sensations oftou ch and pressurefrom the face

Receives the sensation ofpain and temperaturefrom the fac e and some fibers oftouch

Supplies the muscles of masti cation, tensor tympani, tenso r veli palitini, mylohyoid, and anterior belly of digastric m uscle

The dura mater of the posterior cranial fossa is mainly innervated by C2 and C3 nerves via cranial nerves X and XII.

These fibers may be distributed by the vagus and hypoglossal nerves.

The CT shows hydrocephalus, enlargement of the ventricles due to build-up of CSF. The ventricles of the brain are lined by ependymocytes.

Ependymocytes are a type of glial cell that line the ventricles of the brain and the central canal of the spinal cord. They are simple columnar cells. Some are ciliated in order to facilitate the circulation of CSF.

Their functions include secretion of CSF and transport of neurochemicals to and fro from the CSF. They also have a function in neuroregeneration.

The structure marked is the lateral ventricle. The roof of the anterior horn of the lateral ventricle is formed by the anterior part of the body of the corpus callosum.

The lateral ventricle is divided into the body and 3 horns. The locations of the parts are:

• Body - parietal lobe
• Anterior horn - frontal lobe
• Posterior horn - occipital lobe
• Inferior horn - temporal lobe.

The anterior horn extends from the genu of the corpus callosum up to the interventricular foramen. The relations of the anterior horn are:

• Anteriorly - Genu and rostrum of the corpus callosum
• Roof - Anterior part of the body of the corpus callosum
• Floor and lateral wall - Caudate nucleus
• Medial wall - Septum pellucidum and anterior column of fornix

The body or central part extends from the interventricular foramen to the splenium of the corpus callosum. The relations of the body are:

• Roof - Body of the corpus callosum
• Medial wall - Septum pellucidum
• Floor (from lateral to medial) - Caudate nucleus, stria terminalis, thalamostriate vein, thalamus, choroid plexus, and body of the fornix

The posterior horn extends from the splenium to the occipital pole. The relations are:

• Roof and lateral wall - Tapetum of corpus callosum
• Medial wall - Forceps major and calcar avis (calcarine sulcus)

The inferior horn is the largest compartment of the lateral ventricle and extends up to 2.5 cm from the temporal pole. The relations are:

• Roof - Tapetum of corpus callosum and tail of caudate nucleus
• Floor (lateral to medial) - Collateral eminence produced by collateral fissure, hippocampus.

Note: There is no lateral wall for the lateral ventricle.

The two elevations on the medial wall of the posterior horn of the lateral ventricle are due to the forceps major and calcar avis.

The posterior horn extends from the splenium to the occipital pole. The relations are:

• Roof and lateral wall - Tapetum of corpus callosum
• Medial wall - Forceps major and calcar avis (calcarine sulcus)

The forceps major is the fibers of the splenium of the corpus callosum. The calcar avis is formed by the white matter of the calcarine sulcus.

Forceps minor is formed by the anterior part of the corpus callosum.

The collateral eminence is formed by the collateral sulcus and is related to the floor of the inferior horn of the lateral ventricle.

The MRI shows a Dandy-Walker malformation. It is a rare congenital malformation involving the cerebellum and the fourth ventricle. The foramina of Luschka are the lateral openings in the fourth ventricle. These openings allow the flow of CSF from the ventricle into the subarachnoid space.

The fourth ventricle is a tent-shaped ventricle lying between the brainstem and the cerebellum. It is widest at the level of the pontomedullary junction.

The roof of the fourth ventricle is formed by:

• Superior medullary velum - White matter sheet stretching between the superior cerebellar peduncles.
• Inferior medullary velum - Made of ventricular ependyma and pia mater of tela choroidea, and has no nervous tissue. It is pierced by the foramen of Magendie in the midline, opening into the cisterna magna.

The T-shaped choroid plexus of the fourth ventricle is formed from the tela choroidea, made of two layers of pia mater.

The structure marked in the above image is a dural venous sinus, and the CSF is absorbed into this sinus through arachnoid villi.

Tela choroidea gives rise to the choroid plexus, from which CSF is secreted into the ventricles.

Tancytes/specialized glial cells in circumventricular organs help with the transport of neurochemicals to CSF.

The case suggests CSF rhinorrhea and the image shows the double-ring sign. CSF mainly forms in the choroid plexus. It is absorbed back by the arachnoid villi.

Formation of CSF:

• Major contributor - Choroid plexuses
• Minor contributors - Ependymal cells lining the ventricles, brain substance through the perivascular spaces

CSF is produced at a rate of 55– ml/day. The normal adult volume of CSF is 15–ml, and it is cycled about 3.˜ times a day. The normal CSF pressure is ˜–-1™– mm H2O.

Circumventricular organs are those structures in the brain that are devoid of the blood-brain barrier. Adenohypophysis is not devoid of a blood-brain barrier (BBB).

Neurohypophysis is devoid of the blood-brain barrier.

The given clinical scenario is suggestive of total agenesis of the corpus callosum. The most anterior part of the missing brain structure i.e. the corpus callosum is the genu.

The image given below shows an MRI scan of the sagittal section of a normal brain followed by an image showing corpus callosum agenesis.

The correct order of arrangement of stem cells, based on their potency to differentiate into different cells (highest to lowest) is totipotent gt; pluripotent gt; multipotent gt; oligopotent gt; unipotent.