NEET MDS Synopsis
Hypopituitarism
General Pathology
Hypopituitarism
Hypopituitarism is caused by
1. Loss of the anterior pituitary parenchyma
a. congenital
b. acquired
2. Disorders of the hypothalamus e.g. tumors; these interfere with the delivery of pituitary hormone-releasing factors from the hypothalamus.
Most cases of anterior pituitary hypofunction are caused by the following:
1. Nonfunctioning pituitary adenomas
2. Ischemic necrosis of the anterior pituitary is an important cause of pituitary insufficiency. This requires destruction of 75% of the anterior pituitary.
Causes include
a. Sheehan syndrome, refers to postpartum necrosis of the anterior pituitary, and is the most cause. During pregnancy the anterior pituitary enlarges considerably because of an increase in the size and number of prolactin-secreting cells. However, this physiologic enlargement of the gland is not accompanied by an increase in blood supply. The enlarged gland is therefore vulnerable to ischemic injury, especially in women who develop significant hemorrhage and hypotension during the peripartum period. The posterior pituitary is usually not affected.
b. Disseminated intravascular coagulation
c. Sickle cell anemia
d. Elevated intracranial pressure
e. Traumatic injury
f. Shock states
3. Iatrogenic i.e. surgical removal or radiation-induced destruction
4. Inflammatory lesions such as sarcoidosis or tuberculosis
5. Metastatic neoplasms involving the pituitary.
6. Mutations affecting the pituitary transcription factor Pit-1
Children can develop growth failure (pituitary dwarfism) as a result of growth hormone deficiency.
Gonadotropin or gonadotropin-releasing hormone (GnRH) deficiency leads to amenorrhea and infertility in women and decreased libido, impotence, and loss of pubic and axillary hair in men. TSH and ACTH deficiencies result in symptoms of hypothyroidism and hypoadrenalism. Prolactin deficiency results in failure of postpartum lactation.
OCCLUSION AND DENTAL DEVELOPMENT-Development
Dental Anatomy
Development of occlusion.
A. Occlusion usually means the contact relationship in function. Concepts of occlusion vary with almost every specialty of dentistry.
Centric occlusion is the maximum contact and/or intercuspation of the teeth.
B. Occlusion is the sum total of many factors.
1. Genetic factors.
-Teeth can vary in size. Examples are microdontia (very small teeth) and macrodontia (very large teeth). Incidentally, Australian aborigines have the largest molar tooth size—some 35% larger than the smallest molar tooth group
-The shape of individual teeth can vary (such as third molars and the upper lateral incisors.)
-They can vary when and where they erupt, or they may not erupt at all (impaction).
-Teeth can be congenitally missing (partial or complete anodontia), or there can be extra (supernumerary) teeth.
-The skeletal support (maxilla/mandible) and how they are related to each other can vary considerably from the norm.
2. Environmental factors.
-Habits can have an affect: wear, thumbsucking, pipestem or cigarette holder usage, orthodontic appliances, orthodontic retainers have an influence on the occlusion.
3.Muscular pressure.
-Once the teeth erupt into the oral cavity, the position of teeth is affected by other teeth, both in the same dental arch and by teeth in the opposing dental arch.
-Teeth are affected by muscular pressure on the facial side (by cheeks/lips) and on the lingual side (by the tongue).
C. Occlusion constantly changes with development, maturity, and aging.
1 . There is change with the eruption and shedding of teeth as the successional changes from deciduous to permanent dentitions take place.
2. Tooth wear is significant over a lifetime. Abrasion, the wearing away of the occlusal surface reduces crown height and alters occlusal anatomy.
Attrition of the proximal surfaces reduces the mesial-distal dimensions of the teeth and significantly reduces arch length over a lifetime.
Abraision is the wear of teeth by agencies other than the friction of one tooth against another.
Attrition is the wear of teeth by one tooth rubbing against another
3. Tooth loss leaves one or more teeth without an antagonist. Also, teeth drift, tip, and rotate when other teeth in the arch are extracted.
Keratoses (Horny Growth)
General Pathology
Keratoses (Horny Growth)
1. Seborrheic keratosis is a common benign epidermal tumor composed of basaloid (basal cell-like) cells with increased pigmentation that produce a raised, pigmented, "stuck-on" appearance on the skin of middle-aged individuals.
- they can easily be scraped from the skin's surface.
- frequently enlarge of multiply following hormonal therapy.
- sudden appearance of large numbers of Seborrheic keratosis is a possible indication of a malignancy of the gastrointestinal tract (Leser-Trelat sign).
2. An actinic keratosis is a pre-malignant skin lesion induced by ultraviolet light damage.
- sun exposed areas.
- parakeratosis and atypia (dysplasia) of the keratinocytes.
- solar damage to underlying elastic and collagen tissue (solar elastosis).
- may progress to squamous carcinoma in situ (Bowen's disease) or invasive cancer.
3. A keratoacanthoma is characterized by the rapid growth of a crateriform lesion in 3 to 6
weeks usually on the face or upper extremity.
- it eventually regresses and involutes with scarring.
- commonly confused with a well-differentiated squamous cell carcinoma.
Properties of cardiac muscle
Physiology
Properties of cardiac muscle
Cardiac muscle is a striated muscle like the skeletal muscle , but it is different from the skeletal muscle in being involuntary and syncytial .
Syncytium means that cardiac muscle cells are able to excite and contract together due to the presence of gap junctions between adjacent cardiac cells.
Cardiac muscle has four properties , due to which the heart is able to fulfill its function as a pumping organ. Studying and understanding these properties is essential for students to understand the cardiac physiology as a whole.
1. Rhythmicity ( Chronotropism )
2. Excitability ( Bathmotropism )
3. Conductivity
4. Contractility
HERPES ZOSTER (Shingles)
General Pathology
HERPES ZOSTER (Shingles)
An infection with varicella-zoster virus primarily involving the dorsal root ganglia and characterized by vesicular eruption and neuralgic pain in the dermatome of the affected root ganglia.
caused by varicella-zoster virus
Symptoms and Signs
Pain along the site of the future eruption usually precedes the rash by 2 to 3 days. Characteristic crops of vesicles on an erythematous base then appear, following the cutaneous distribution of one or more adjacent dermatomes
Eruptions occur most often in the thoracic or lumbar region and are unilateral. Lesions usually continue to form for about 3 to 5 days
Geniculate zoster (Ramsay Hunt's syndrome) results from involvement of the geniculate ganglion. Pain in the ear and facial paralysis occur on the involved side. A vesicular eruption occurs in the external auditory canal, and taste may be lost in the anterior two thirds of the tongue
Polycarbonate Crowns
PedodonticsPolycarbonate Crowns in Pedodontics
Polycarbonate crowns are commonly used in pediatric dentistry, particularly
for managing anterior teeth affected by nursing bottle caries. These crowns
serve as temporary fixed prostheses for primary teeth, providing a functional
and aesthetic solution until the natural teeth exfoliate. This lecture will
discuss the indications, contraindications, and advantages of polycarbonate
crowns in pedodontic practice.
Nursing Bottle Caries
Definition: Nursing bottle caries, also known as early
childhood caries, is a condition characterized by the rapid demineralization
of the anterior teeth, primarily affecting the labial surfaces.
Progression: The lesions begin on the labial face of
the anterior teeth and can lead to extensive demineralization, affecting the
entire surface of the teeth.
Management Goal: The primary objective is to stabilize
the lesions without attempting a complete reconstruction of the coronal
anatomy.
Treatment Approach
Preparation of the Lesion:
The first step involves creating a clean periphery around the
carious lesion using a small round bur.
Care should be taken to leave the central portion of the affected
dentin intact to avoid pulp exposure.
This preparation allows for effective ion exchange with glass
ionomer materials, facilitating a good seal.
Use of Polycarbonate Crowns:
Polycarbonate crowns are indicated as temporary crowns for deciduous
anterior teeth that will eventually exfoliate.
They provide a protective covering for the tooth while maintaining
aesthetics and function.
Contraindications for Polycarbonate Crowns
Polycarbonate crowns may not be suitable in certain situations, including:
Severe Bruxism: Excessive grinding can lead to
premature failure of the crown.
Deep Bite: A deep bite may cause undue stress on the
crown, leading to potential fracture or dislodgment.
Excessive Abrasion: High levels of wear can compromise
the integrity of the crown.
Advantages of Polycarbonate Crowns
Polycarbonate crowns offer several benefits in pediatric dentistry:
Time-Saving: The application of polycarbonate crowns is
relatively quick, making them efficient for both the clinician and the
patient.
Ease of Trimming: These crowns can be easily trimmed to
achieve the desired fit and contour.
Adjustability: They can be adjusted with pliers,
allowing for modifications to ensure proper seating and comfort for the
patient.
Root Formation and Obliteration
Dental Anatomy
Root Formation and Obliteration
1. In general, the root of a deciduous tooth is completely formed in just about one year after eruption of that tooth into the mouth.
2. The intact root of the deciduous tooth is short lived. The roots remain fully formed only for about three years.
3. The intact root then begins to resorb at the apex or to the side of the apex, depending on the position of the developing permanent tooth bud.
4. Anterior permanent teeth tend to form toward the lingual of the deciduous teeth, although the canines can be the exception. Premolar teeth form between the roots of the deciduous molar teeth
Cryptococcosis
General Pathology
Cryptococcosis
An infection acquired by inhalation of soil contaminated with the encapsulated yeast Cryptococcus neoformans, which may cause a self-limited pulmonary infection or disseminate, especially to the meninges, but sometimes to the skin, bones, viscera, or other sites.
Cryptococcosis is a defining opportunistic infection for AIDS, although patients with Hodgkin's or other lymphomas or sarcoidosis or those receiving long-term corticosteroid therapy are also at increased risk.
AIDS-associated cryptococcal infection may present with severe, progressive pneumonia with acute dyspnea and an x-ray pattern suggestive of Pneumocystis infection.
Primary lesions in the lungs are usually asymptomatic and self-limited
Pneumonia usually causes cough and other nonspecific respiratory symptoms. Rarely, pyelonephritis occurs with renal papillary necrosis development.
Most symptoms of cryptococcal meningitis are attributable to brain swelling and are usually nonspecific, including headache, blurred vision, confusion, depression, agitation, or other behavioral changes. Except for ocular or facial palsies, focal signs are rare until relatively late in the course of infections. Blindness may develop due to brain swelling or direct involvement of the optic tracts. Fever is usually low-grade and frequently absent.