NEET MDS Synopsis
Cushings syndrome
General Pathology
Cushing’s syndrome
The symptoms and signs of Cushing’s syndrome are associated with prolonged inappropriate elevation of free corticosteroid levels.
Clinical features
- Central obesity and moon face.
- Plethora and acne.
- Menstrual irregularity.
- Hirsutism and hair thinning.
- Hypertension.
- Diabetes.
- Osteoporosis—may cause collapse of vertebrae, rib fractures.
- Muscle wasting and weakness.
- Atrophy of skin and dermis—paper thin skin with bruising tendency, purple striae.
Aetiopathogenesis — patients with Cushing’s syndrome can be classified into two groups on the basis of whether the aetiology of the condition is ACTH dependent or independent.
Classification of Cushing's syndrome
ACTH dependent- Iatrogenic (ACTH therapy) Pituitary hypersecretion of ACTH Ectopic ACTH syndrome (benign or malignant non-endocrine tumour)
Non-ACTH dependent - Iatrogenic, e.g. prednisolone Adrenal cortical adenoma , Adrenal cortical carcinoma
ACTH-dependent aetiology:
- Pituitary hypersecretion of ACTH (Cushing’s disease)—bilateral adrenal hyperplasia secondary to excessive secretion of ACTH by a corticotroph adenoma of the pituitary gland.
- Production of ectopic ACTH or corticotrophin- releasing hormone (CRH) by non-endocrine neoplasm, e.g. small cell lung cancer and some carcinoid tumours. In cases of malignant bronchial tumour, the patient rarely survives long enough to develop any physical features of Cushing’s syndrome.
Non-ACTH-dependent aetiology
Iatrogenic steroid therapy—most common cause of Cushing’s syndrome.
Adrenal cortical adenoma—well-circumscribed yellow tumour usually 2–5 cm in diameter.
Extremely common as an incidental finding in up to 30% of all post-mortem examinations. The yellow colour is due to stored lipid (mainly cholesterol) from which the hormones are synthesised. The vast majority have no clinical effects (i.e. they are non-functioning adenomas), with only a small percentage producing Cushing’s syndrome.
Adrenal cortical carcinoma—rare and almost always associated with the overproduction of hormones, usually glucocorticoids and sex steroids.
Cushing’s syndrome mixed with androgenic effects which are particularly noticeable in women. Tumours are usually large and yellowish white in colour. Local invasion and metastatic spread are common.
Irrespective of the aetiology, the diagnosis is based on clinical features and the demonstration of a raised plasma cortisol level.
The aetiology of the disorder is elucidated through:
- Raised urinary cortisol in the first instance, but further testing is required.
- Low-dose dexamethasone suppression test (suppression of cortisol levels in Cushing’s disease due to suppression of pituitary ACTH secretion, but a lack of suppression suggests ACTH-independent Cushing’s syndrome).
- MRI and CT scan visualisation of pituitary and adrenal glands.
- Analysis of blood ACTH (high = pituitary adenoma or ectopic ACTH source; low = primary adrenal tumour due to feedback suppression).
- Treatment of the underlying cause is essential as untreated Cushing’s syndrome has a 50% 5-year mortality rate.
The therapeutic administration of glucocorticosteroids (e.g. prednisolone) is a common cause of the features of Cushing’s syndrome.
The Sprue
Dental Materials
The Sprue :
Its a channel through which molten alloy can reach the mold in an invested ring after the wax has been eliminated. Role of a Sprue: Create a channel to allow the molten wax to escape from the mold. Enable the molten alloy to flow into the mold which was previously occupied by the wax pattern.
FUNCTIONS OF SPRUE
1 . Forms a mount for the wax pattern .
2 . Creates a channel for elimination of wax .
3 .Forms a channel for entry of molten metal
4 . Provides a reservoir of molten metal to compensate for the alloy shrinkage .
SELECTION OF SPRUE
Sprue former gauge selection is often empirical, is yet based on the following five general principles:
1. Select the gauge sprue former with a diameter that is approximately the same size as the thickest area of the wax pattern. If the pattern is small, the sprue former must also be small because a large sprue former attached to a thin delicate pattern could cause distortion. However if the sprue former diameter is too small this area will solidify before the casting itself and localized shrinkage porosity may result.
2. If possible the sprue former should be attached to the portion of the pattern with the largest cross-sectional area. It is best for the molten alloy to flow from the thick section to the surrounding thin areas. This design minimizes the risk of turbulence.
3. The length of the sprue former should be long enough to properly position the pattern in the casting ring within 6mm of the trailing end and yet short enough so the molten alloy does not solidify before it fills the mold.
4. The type of sprue former selected influences the burnout technique used. It is advisable to use a two-stage burnout technique whenever plastic sprue formers or patterns are involved to ensure complete carbon elimination, because plastic sprues soften at temperatures above the melting point of the inlay waxes.
5. Patterns may be sprued directly or indirectly. For direct sprueing the sprue former provides the direct connection between the pattern area and the sprue base or crucible former area. With indirect spruing a connector or reservoir bar is positioned between the pattern and the crucible former. It is common to use indirect spruing for multiple stage units and fixed partial dentures.
Oral Surgery NEET MDS Discussion part 1
NEET MDS
Surface Defence Mechanisms
General Pathology
Surface Defence Mechanisms
1. Skin:
(i) Mechanical barrier of keratin and desquamation.
(ii) Resident commensal organisms
(iii)Acidity of sweat.
(iv) Unsaturated fatty acids of sebum
2. Oropharyngeal
(i)Resident flora
(ii) Saliva, rich in lysozyme, mucin and Immunoglobulins (lgA).
3. Gastrointestinal tract.-
(i) Gastric HCI
(ii) Commensal organisms in Intestine
(iii) Bile salts
(iv) IgA.
(v) Diarrhoeal expulsion of irritants.
4. Respiratory tract:
(i) Trapping in turbinates
(ii) Mucus trapping
(iii) Expulsion by coughing and sneezing.
(iv) Ciliary propulsion.
(V) Lysozymes and antibodies in secretion.
(vi) Phagocytosis by alveolar macrophages.
5. Urinary tract:
(i) Flushing action.
(ii) Acidity
(iii) Phagocytosis by urothelial cells.
6. Vagina.-
(i) Desquamation.
(ii) Acid barrier.
(iii) Doderlein's bacilli (Lactobacilli)
7. Conjunctiva:
Lysozymes and IgA in tears
Mandibular First Deciduous Molar
Dental Anatomy
Mandibular First Deciduous Molar
-This tooth doesn't resemble any other tooth. It is unique unto itself.
-There are two roots.
-There is a strong bulbous enamel bulge buccally at the mesial.
- the mesiolingual cusps on this tooth is the highest and largest of the cusps.
Causes of disease
General Pathology
Causes of disease
The causes of disease Diseases can be caused by either environmental factors, genetic factors or a combination of the two.
A. Environmental factors
Environmental causes of disease are many and are classified into:
1. Physical agents
2. Chemicals
3. Nutritional deficiencies & excesses
4. Infections & infestations
5. Immunological factors
6. Psychogenic factors
1. Physical agents
These include trauma, radiation, extremes of temperature, and electric power. These agents
apply excess physical energy, in any form, to the body.
2. Chemicals
With the use of an ever-increasing number of chemical agents such as drugs,
3. Nutritional deficiencies and excesses
Nutritional deficiencies may arise as a result of poor supply, interference with absorption, inefficient transport within the body, or defective utilization. It may take the form of deficiency.
4. Infections and infestations
Viruses, bacteria, fungi, protozoa, and metazoa all cause diseases. They may do so by causing cell destruction directly as in virus infections (for example poliomyelitis) or protozoal infections (for example malaria).
5. Immunological factors
A. Hypersensitivity reaction
This is exaggerated immune response to an antigen. For example, bronchial asthma can occur due to exaggerated immune response to the harmless pollen.
B. Immunodeficiency
This is due to deficiency of a component of the immune system which leads to increased susceptibility to different diseases. An example is AIDS.
C. Autoimmunity
This is an abnormal (exaggerated) immune reaction against the self antigens of the host. Therefore, autoimmunity is a hypersensitivity reaction against the self antigens. 4
6. Psychogenic factors
The mental stresses imposed by conditions of life, particularly in technologically advanced
communities, are probably contributory factors in some groups of diseases.
B. Genetic Factors
These are hereditary factors that are inherited genetically from parents.
PHARMACOLOGY OF LOCAL ANESTHETICS
Pharmacology
PHARMACOLOGY OF LOCAL ANESTHETICS
Characteristics
1. Block axon conduction (nerve impulse) when applied locally in appropriate concentrations.
2. Local anesthetic action must be completely reversible; however, the duration of the anesthetic block should be of sufficient length to allow completion of the planned treatment.
3. Produce minimal local toxic effects such as nerve and muscle damage as well as minimal systemic toxic effects of organ systems such as the cardiovascular and central nervous system.
Nystatin
Pharmacology
Nystatin
Candida spp. are sensitive to nystatin.
Uses: Cutaneous, vaginal, mucosal and esophageal infections.
Candida infections can be treated with nystatin.
Cryptococcus is also sensitive to nystatin.
Nystatin is often used as prophylaxis in patients who are at risk for fungal infections, such as AIDS patients with a low CD4+ count and patients receiving chemotherapy.
MOA
nystatin binds to ergosterol, the main component of the fungal cell membrane. When present in sufficient concentrations, it forms a pore in the membrane that leads to K+ leakage and death of the fungus.