NEET MDS Synopsis
Cytopathologic techniques
General Pathology
Cytopathologic techniques
Cytopathology is the study of cells from various body sites to determine the cause or nature of disease.
Applications of cytopathology:
Screening for the early detection of asymptomatic cancer
2. Diagnosis of symptomatic cancer
3. Surveillance of patients treated for cancer
Cytopathologic methods
There are different cytopathologic methods including:
1. Fine-needle aspiration cytology (FNAC) -In FNAC, cells are obtained by aspirating the diseased organ using a very thin needle under negative pressure.
Superficial organs (e.g. thyroid, breast, lymph nodes, skin and soft tissues) can be easily aspirated.
Deep organs, such as the lung, mediastinum, liver, pancreas, kidney, adrenal gland, and retroperitoneum are aspirated with guidance by fluoroscopy, ultrasound or CT scan.
Exfoliative cytology
Refers to the examination of cells that are shed spontaneously into body fluids or secretions. Examples include sputum, cerebrospinal fluid, urine, effusions in body cavities (pleura, pericardium, peritoneum), nipple discharge and vaginal discharge.
Abrasive cytology
Refers to methods by which cells are dislodged by various tools from body surfaces (skin, mucous membranes, and serous membranes). E.g. preparation of cervical smears with a spatula or a small brush to detect cancer of the uterine cervix at early stages.
SPECIAL SOMATIC AFFERENT (SSA) PATHWAYS
Physiology
SPECIAL SOMATIC AFFERENT (SSA) PATHWAYS
Hearing
The organ of Corti with its sound-sensitive hair cells and basilar membrane are important parts of the sound transducing system for hearing. Mechanical vibrations of the basilar membrane generate membrane potentials in the hair cells which produce impulse patterns in the cochlear portion of the vestibulocochlear nerve (VIII)
Special somatic nerve fibers of cranial nerve VIII relay impulses from the sound receptors (hair cells) in the cochlear nuclei of the brainstem
These are bipolar neurons with cell bodies located in the spiral ganglia of the cochlea.
Vestibular System
The vestibulocochlear nerve serves two quite different functions.
The cochlear portion, conducts sound information to the brain,
The vestibular portion conducts proprioceptive information.
It is the central neural pathways
Special somatic afferent fibers from the hair cells of the macula utriculi and macula sacculi conduct information into the vestibular nuclei on the ipsilateral side of the pons and medulla.
These are bipolar neurons with cell bodies located in the vestibular ganglion.
Some of the fibers project directly into the ipsilateral cerebellum to terminate in the uvula, flocculus, and nodulus, but most enter the vestibular nuclei and synapse there.
Vision
The visual system receptors are the rods and cones of the retina.
Special somatic afferent fibers of the optic nerve (II) conduct visual signals into the brain
Fibers from the lateral (temporal) retina of either eye terminate in the lateral geniculate body on the same side of the brain as that eye.
SSA II fibers from the medial (nasal) retina of each eye cross over in the optic chiasm to terminate in the contralateral lateral geniculate body.
Area 17 is the primary visual area, which receives initial visual signals.
Neurons from this area project into the adjacent occipital cortex (areas 18 and 19) which is known as the secondary visual area. It is here that the visual signal is fully evaluated.
The visual reflex pathway involving the pupillary light reflex - in which the pupils constrict when a light is shined into the eyes and dilate when the light is removed.
Some SSA II fibers leave the optic tract before reaching the lateral geniculates, terminating in the superior colliculi instead.
From here, short neurons project to the EdingerWestphal nucleus (an accessory nucleus of III) in the midbrain, which serves as the origin of the preganglionic parasympathetic fibers of the oculomotor nerve (GVE III).
The GVE III fibers in turn project to the ciliary ganglia, from which arise the postganglionic fibers to the sphincter muscles of the iris, which constrict the pupils.
Xylitol
PedodonticsXylitol and Its Role in Dental Health
Xylitol is a naturally occurring sugar alcohol that is widely recognized for
its potential benefits in dental health, particularly in the prevention of
dental caries.
Properties of Xylitol
Low-Calorie Sweetener: Xylitol is a low-calorie sugar
substitute that provides sweetness without the high caloric content of
traditional sugars.
Natural Occurrence: It is found in small amounts in
various fruits and vegetables and can also be produced from birch wood and
corn.
Mechanism of Action
Inhibition of Streptococcus mutans:
Xylitol has been shown to inhibit the growth of Streptococcus
mutans, the primary bacterium responsible for dental caries.
It disrupts the metabolism of these bacteria, reducing their ability
to produce acids that demineralize tooth enamel.
Research and Evidence
Studies by Makinen:
Dr. R. Makinen has conducted extensive research on xylitol,
collaborating with various researchers worldwide.
In 2000, he published a summary titled “The Rocky Road of Xylitol to
its Clinical Application,” which highlighted the challenges and
successes in the clinical application of xylitol.
Caries Activity Reduction:
Numerous studies indicate that xylitol chewing gum significantly
reduces caries activity in both children and adults.
The evidence suggests that regular use of xylitol can lead to a
decrease in the incidence of cavities.
Transmission of S. mutans:
Research has shown that xylitol chewing gum can decrease the
transmission of S. mutans from mothers to their children,
potentially reducing the risk of early childhood caries.
Applications of Xylitol
Incorporation into Foods and Dentifrices:
Xylitol has been tested as an additive in various food products and
dental care items, including toothpaste and mouth rinses.
Its sweetening properties make it an appealing option for children,
promoting compliance with oral health recommendations.
Popularity as a Caries Prevention Strategy:
The use of xylitol chewing gum is gaining traction as an effective
caries prevention strategy, particularly among children.
Its palatable taste and low-calorie nature make it an attractive
alternative to traditional sugary snacks.
HYPERTROPHY
General Pathology
HYPERTROPHY
Increase in the size of an organ or tissue due to increase in the size of its Constituent cells.
1. Skeletal muscle due to -exercise.
2. Cardiac muscle of:
- Left ventricle in:
o Hypertension.
o Aortic valvular lesion.
o Severe anaemia.
- Right ventricle in :
o Mitral stenosis
o Cor pulmonale
3. Smooth muscle of:
- GIT proximal to strictures.
- Uterus in pregnancy.
Age changes in the dentition
Dental Anatomy
Age changes in the dentition
I. After the teeth have reached full occlusion, microscopic tooth movements occur to compensate for wear at the contact area (Mesial Drift) and occlusal surfaces (by Deposition of cementum at the root apex)
2. Attrition of incisal ridges and cusp tips may be so severe that dentin may become exposed and intrinsically stained
3. Secondary dentin may be formed in response to dental caries, trauma, and aging and result in decreased pulp size and tooth sensation
MAXILLARY SECOND MOLAR
Dental Anatomy
MAXILLARY SECOND MOLAR
The second molars are often called 12-year molars because they erupt when a child is about 12 years
Facial: The crown is shorter occluso-cervically and narrower mesiodistally whe compared to the first molar. The distobuccal cusp is visibly smaller than the mesiobuccal cusp. The two buccal roots are more nearly parallel. The roots are more parallel; the apex of the mesial root is on line with the with the buccal developmental groove. Mesial and distal roots tend to be about the same length.
Lingual: The distolingual cusp is smaller than the mesiolingual cusp. The Carabelli trait is absent.
Proximal: The crown is shorter than the first molar and the palatal root has less diverence. The roots tend to remain within the crown profile.
Occlusal: The distolingual cusp is smaller on the second than on the first molar. When it is much reduced in size, the crown outline is described as 'heart-shaped.' The Carabelli trait is usually absent. The order of cusp size, largest to smallest, is the same as the first but is more exaggerated: mesiolingual, mesiobuccal, distobuccal, and distolingual.
Contact Points; Height of Curvature: Both mesial and distal contacts tend to be centered buccolingually below the marginal ridges. Since themolars become shorter, moving from first to this molar, the contacts tend to appear more toward the center of the proximal surfaces.
Roots: There are three roots, two buccal and one lingual. The roots are less divergent than the first with their apices usually falling within the crown profile. The buccal roots tend to incline to the distal.
Note: The distolingual cusp is the most variable feature of this tooth. When it is large, the occlusal is somewhat rhomboidal; when reduced in size the crown is described as triangual or 'heart-shaped.' At times, the root may be fused.
Esophagus pathology
General Pathology
ESOPHAGUS Pathology
Congenital malformations
1. A tracheoesophageal fistula (the most prevalent esophageal anomaly) occurs most commonly as an upper esophageal blind pouch with a fistula between the lower segment of the esophagus and the trachea. It is associated with hydramnios, congenital heart disease, and other gastrointestinal malformation.
2. Esophageal atresia is associated with VATER syndrome (vertebra1 defects, anal atresia, tracheoesophageal fistula, and renal dysplasia)
3. Stenosis refers to a narrowed esophagus with a small lumen. lt may be congenital or acquired, e.g., through trauma or inflammation.
Inflammatory disorders
Esophagitis
most often involves the lower half of the esophagus. Caused by the reflux of gastric contents (juices) into the lower esophagus. One of the most common GI disorders.
Clinical features.
Patients experience substernal burning associated with regurgitation, mild anemia, dysphagia, hematemesis, and melena. Esophagitis may predispose to esophageal cancer.
Etiology
- Reflux esophagitis is due to an incompetent lower esophageal sphincter that permits reflux of gastric juice into the lower esophagus.
- Irritants such as citric acid, hot liquids, alcohol, smoking, corrosive chemicals, and certain drugs, such as tetracycline, may provoke inflammation.
- Infectious etiologies include herpes, CMV, and C. albicans. The immunocompromised host is particularly susceptible to infectious esophagitis.
Although chronic or severe reflux disease is uncommon, consequences of these conditions can lead to Barrett’s esophagus, development of a stricture, or hemorrhage.
Pathology
-Grossly, there is hyperemia, edema, inflammation, and superficial necrosis.
Complications include ulceration, bleeding, stenosis, and squamous carcinoma.
Treatment: diet control, antacids, and medications that decrease the production of gastric acid (e.g., H blockers).
Barrett's esophagus,
gastric or intestinal columnar epithelium replaces normal squamous epithelium in response to chronic reflux.- A complication of chronic gastroesophageal reflux disease.
- Histologic findings include the replacement of squamous epithelium with metaplastic columnar epithelium.
- Complications include increased incidence of esophageal adenocarcinoma, stricture formation, or hemorrhage (ulceration).
Motor disorders.
Normal motor function requires effective peristalsis and relaxation of the lower esophageal sphincter.
Achalasia is a lack of relaxation of the lower esophageal sphincter (LES), which may be associated with aperistalsis of the esophagus and increased basal tone of the LES.
Clinical features. Achalasia occurs most commonly between the ages of 30 and 50. Typical symptoms are dysphagia, regurgitation, aspiration, and chest pain. The lack of motility promotes stagnation and predisposes to carcinoma.
Hiatal hernia is the herniation of the abdominal esophagus, the stomach, or both, through the esophageal hiatus in the diaphragm.
Scleroderma is a collagen vascular disease, seen primarily in women, that causes subcutaneous fibrosis and widespread degenerative changes. (A mild variant is known as CREST syndrome which stands for calcinosis. raynaud's phenomenon , esophageal dysfunction, sclerodactyly and telengectseia. esophagus is the most frequently involved region of the gastrointestinal tract.
Clinical features are mainly dysphagia and heartburn due to reflux oesophagitis caused by aperlistalsis and incompetent LES.
Rings and webs
1. Webs are mucosal folds in the upper esophagus above the aortic arch.
2. Schatzki rings are mucosal rings at the squamocolumnarjunction below the aortic arch.
3. Plummer Vinson Syndrome consist of triad of dysphagia, atrophic glossitis, and anemia. Webs are found in the upper esophagus. The syndrome is associated specifically with iron deficiency anemia and sometimes hypochlorhydria. Patients are at increased risk for carcinoma of the pharynx or esophagus.
Mallory-Weiss syndrome
Mallory-Weiss tears refers to small mucosal tears at the gastroesophageal junction secondary to recurrent forceful vomiting. The tears occur along the long axis an result in hematemesis (sometimes massive).
- Characterized by lacerations (tears) in the esophagus.
- Most commonly occurs from vomiting (alcoholics).
- A related condition, known as Boerhaave syndrome, occurs when the esophagus ruptures, causing massive upper GI hemorrhage.
Esophageal varices
- The formation of varices (collateral channels) occurs from portal hypertension.
Causes of portal hypertension include blockage of the portal vein or liver disease (cirrhosis).
- Rupture of esophageal varices results in massive hemorrhage into the esophagus and hematemesis.
- Common in patients with liver cirrhosis.
Diverticula
are sac-like protrusions of one or more layers of pharyngeal or esophageal wall.
Tumors
- Benign tumors are rare.
- Carcinoma of the esophagus most commonly occurs after 50 and has a male:female ratio of 4.1.
Etiology: alcohal ingestion, smoking, nitrosamines in food, achalasia , web ring, Barrettes esophagus, and deficiencies of vitamins A and C , riboflavin, and some trace minerals
Clinical features include dysphagia (first to solids), retrosternal pain, anorexia, weight loss, melena, and symptoms secondary to metastases.
Pathology
- 50% occur in the middle third of the esophagus, 30% in the lower third, and 20% in the upper third. Most esophageal cancers are squamous cell carcinomas.
Adenocarcinomas arise mostly out of Barrett's esophagus.
Prognosis
is poor. Fewer than 10% of patients survive 5 years, usually because diagnosis is made at a late stage. The most common sites of metastasis are the liver and lung. The combination of cigarette smoking and alcohol is particularly causative for esophageal cancer (over l00% risk compared to nondrinkers/nonsmokers).
IRON
Biochemistry
IRON
The normal limit for iron consumption is 20 mg/day for adults, 20-30 mg/day for children and 40 mg/day for pregnant women.
Milk is considered as a poor source of iron.
Factors influencing absorption of iron Iron is absorbed by upper part of duodenum and is affected by various factors
(a) Only reduced form of iron (ferrous) is absorbed and ferric form are not absorbed
(b) Ascorbic acid (Vitamin C) increases the absorption of iron (c) The interfering substances such as phytic acid and oxalic acid decreases absorption of iron
Regulation of absorption of Iron
Absorption of iron is regulated by three main mechanisms, which includes
(a) Mucosal Regulation
(b) Storer regulation
(c) Erythropoietic regulation
In mucosal regulation absorption of iron requires DM-1 and ferroportin. Both the proteins are down regulated by hepcidin secreted by liver. The above regulation occurs when the body irons reserves are adequate. When the body iron content gets felled, storer regulation takes place. In storer regulation the mucosal is signaled for increase in iron absorption. The erythropoietic regulation occurs in response to anemia. Here the erythroid cells will signal the mucosa to increase the iron absorption.
Iron transport in blood
The transport form of iron in blood is transferin. Transferin are glycoprotein secreted by liver. In blood, the ceruloplasmin is the ferroxidase which oxidizes ferrous to ferric state.
Storage form of iron is ferritin. Almost no iron is excreted through urine.
Anemia
Anemia is the most common nutritional deficiency disease. The microscopic appearance of anemia is characterized by microcytic hypochromic anemia
The abnormal gene responsible for hemosiderosis is located on the short arm of chromosome No.6.
The main causes of iron deficiency or anemia are
(a) Nutritional deficiency of iron (b) Lack of iron absorption (c) Hook worm infection (d) Repeated pregnancy (e) Chronic blood loss (f) Nephrosis (g) Lead poisoning