NEET MDS Synopsis
Red Blood Cells (erythrocytes)
PhysiologyRed Blood Cells (erythrocytes)
Women average about 4.8 million of these cells per cubic millimeter (mm3; which is the same as a microliter [µl]) of blood.
Men average about 5.4 x 106 per µl.
These values can vary over quite a range depending on such factors as health and altitude.
RBC precursors mature in the bone marrow closely attached to a macrophage.
They manufacture hemoglobin until it accounts for some 90% of the dry weight of the cell.
The nucleus is squeezed out of the cell and is ingested by the macrophage.
RBC have characteristic biconcave shape
Thus RBCs are terminally differentiated; that is, they can never divide. They live about 120 days and then are ingested by phagocytic cells in the liver and spleen. Most of the iron in their hemoglobin is reclaimed for reuse. The remainder of the heme portion of the molecule is degraded into bile pigments and excreted by the liver. Some 3 million RBCs die and are scavenged by the liver each second.
Red blood cells are responsible for the transport of oxygen and carbon dioxide.
Muscles of the Orbit
AnatomyLevator Palpebrae Superioris Muscles
This is a thin, triangular muscle that elevates the upper eyelid.
It is continuously active except during sleeping and when the eye is closing.
Origin: roof of orbit, anterior to the optic canal.
Insertion: this muscle fans out into a wide aponeurosis that inserts into the skin of the upper eyelid. The inferior part of the aponeurosis contains some smooth muscle fibres that insert into the tarsal plate.
Innervation: the superior fibres are innervated by the oculomotor nerve (CN III), and the smooth muscle component is innervated by fibres of the cervical sympathetic trunk and the internal carotid plexus.
Illnesses involving the Levator Palpebrae Superioris
In third nerve palsy, the upper eyelid droops (ptosis) and cannot be raised voluntarily.
This results from damage to the oculomotor nerve (CN III), which supplies this muscle.
If the cervical sympathetic trunk is interrupted, the smooth muscle component of the levator palpebrae superioris is paralysed and also causes ptosis.
This is part of Horner's syndrome.
The Rectus Muscles
There are four rectus muscles (L. rectus, straight), superior, inferior, medial and lateral.
These arise from a tough tendinous cuff, called the common tendinous ring, which surrounds the optic canal and the junction of the superior and inferior orbital fissures.
From their common origin, these muscles run anteriorly, close to the walls of the orbit, and attach to the eyeball just posterior to the sclerocorneal junction.
The medial and lateral rectus muscles attach to the medial and lateral sides of the eyeball respectively, on the horizontal axis.
However, the superior rectus attaches to the anterosuperior aspect of the medial side of the eyeball while the inferior rectus attaches to the anteroinferior aspect of the medial side of the eye.
The Oblique Muscles
The Superior Oblique Muscle
This muscle arises from the body of the sphenoid bone, superomedial to the common tendinous ring.
It passes anteriorly, superior and medial to the superior and medial rectus muscles.
It ends as a round tendon that runs through a pulley-like loop called the trochlea (L. pulley).
After passing though the trochlea, the tendon of the superior oblique turns posterolaterally and inserts into the sclera at the posterosuperior aspect of the lateral side of the eyeball.
The Inferior Oblique Muscle
This muscle arises from the maxilla in the floor of the orbit.
It passes laterally and posteriorly, inferior to the inferior rectus muscle.
It inserts into the sclera at the posteroinferior aspect of the lateral side of the eyeball.
Multiple sclerosis
General Pathology
Multiple sclerosis
a. A demyelinating disease that primarily affects myelin (i.e. white matter). This affects the conduction of electrical impulses along the axons of nerves. Areas of demyelination are known as plaques.
b. The most common demyelinating disease.
c. Onset of disease usually occurs between ages 20 and 50; slightly more common in women.
d. Disease can affect any neuron in the central nervous system, including the brainstem and spinal cord. The optic nerve (vision) is commonly affected.
Osmotic diuretics
Pharmacology
Osmotic diuretics
An osmotic diuretic is a type of diuretic that inhibits reabsorption of water and sodium. They are pharmacologically inert substances that are given intravenously. They increase the osmolarity of blood and renal filtrate.
Mechanism(s) of Action
1. Reduce tissue fluid (edema)
2. Reflex cardiovascular effect by osmotic retention of fluid within vascular space which increases blood volume (contraindicated with Congestive heart failure)
3. Diuretic effect
o Makes H2O reabsorption far more difficult for tubular segments insufficient Na & H2O capacity in distal segments
o Increased intramedullary blood flow (washout)
o Incomplete sodium recapture (asc. loop). this is indirect inhibition of Na reabsorption (Na stays in tubule because water stays)
o Net diuretic effect:
Tubular concentration of sodium decreases
Total amount of sodium lost amount increases
GFR unchanged or slightly increased
Toxicity
Circulatory overload, dilutional hyponatremia, Hyperkalemia, edema, skin necrosis
Agents
Mannitol
Non-odontogenic cysts
Oral Pathology
Nasopalatine cyst
Radiology
The nasopalatine cyst appears as a well-defined, round radiolucency in the midline of the anterior maxilla . Sometimes it appears to be 'heart-shaped' because of super-imposition of the anterior nasal spine.
Radiological assessment should include examination of the lamina dura of the central incisors (to exclude a radicular cyst) and assessment of size (the nasopalatine foramen may reach a width of as much as 10 mm).
Pathology
The cyst is lined by a layer of pseudostratified ciliated columnar epithelium and/or stratified squamous epithelium. The capsule of the cyst is fibrous and may include the incisive canal neurovascular bundle.
Nasolabial cyst
Radiology
'Bowing' inwards of the anterolateral margin of the nasal cavity has been recorded
Pathology
The nasolabial cyst is lined by non-ciliated pseudostratified columnar epithelium, which is often rich in mucous cells.
Bacterial infectious diseases
General Medicine
Bacterial infectious diseases
Anthrax
- an acute infectious disease caused by the bacteria Bacillus anthracis
- Anthrax can enter the human body through the intestines (ingestion), lungs (inhalation), or skin (cutaneous).
1. Pulmonary (pneumonic, respiratory, or inhalation) anthrax
Respiratory infection initially presents with cold or flu-like symptoms for several days, followed by severe (and often fatal) respiratory collapse.
A lethal dose of anthrax is reported to result from inhalation of 10,000-20,000 spores. This form of the disease is also known as Woolsorters' disease or as Ragpickers' disease.
2. Gastrointestinal (gastroenteric) anthrax
Gastrointestinal infection often presents with serious gastrointestinal difficulty, vomiting of blood, and severe diarrhea. Untreated intestinal infections result in 25-65% mortality.
3. Cutaneous (skin) anthrax
Cutaneous infection often presents with large, painless necrotic ulcers (beginning as an irritating and itchy skin lesion or blister that is dark and usually concentrated as a black dot, somewhat resembling bread mold) at the site of infection.
Treatment
- large doses of intravenous and oral antibiotics, such as penicillin, ciprofloxacin, doxycycline, erythromycin, and vancomycin.
- Antibiotic prophylaxis is crucial in cases of pulmonary anthrax to prevent death.
Cholera
- a water-borne disease caused by the bacterium Vibrio cholerae, which are typically ingested by drinking contaminated water, or by eating improperly cooked fish, especially shellfish.
Symptoms
- general GI tract upset: profuse diarrhea (eg 1L/hour), abdominal cramping, fever, nausea and vomiting.
- Dehydration
- severe metabolic acidosis with potassium depletion, anuria, circulatory collapse and cyanosis
- Death is through circulatory volume shock (massive loss of fluid and electrolytes)
Treatment
- rehydration and replacement of electrolytes
- Tetracycline antibiotics may have a role in reducing the duration and severity of cholera
Diphtheria
- Diphtheria is an upper respiratory tract illness characterized by sore throat, low-grade fever, and an adherent membrane (a pseudomembrane) on the tonsil(s), pharynx, and/or nose
Signs and symptoms
- Incubation time of 1-4 days
- Symptoms include fatigue, fever, a mild sore throat and problems swallowing
- Children infected have symptoms that include nausea, vomiting, chills, and a high fever,
Treatment
- Antibiotics are used in patients or carriers to eradicate C. diphtheriae and prevent its transmission to others
- Erythromycin (orally or by injection) for 14 days (40 mg/kg per day with a maximum of 2 g/d), or
- Procaine penicillin G given intramuscularly for 14 days (300,000 U/d for patients weighing <10 kg and 600,000 U/d for those weighing >10 kg).
- Patients with allergies to penicillin G or erythromycin can use rifampin or clindamycin.
- In more severe cases lymph nodes in the neck may swell, and breathing and swallowing will be more difficult throat may require intubation or a tracheotomy
Pertussis
- Pertussis, also known as "whooping cough", is a highly contagious disease caused by certain species of the bacterium Bordetella—usually B. pertussis
- The disease is characterized initially by mild respiratory infections symptoms such as cough, sneezing, and runny nose (catarrhal stage).
- After one to two weeks the cough changes character, with paroxysms of coughing followed by an inspiratory "whooping" sound (paroxysmal stage)
- Other complications of the disease include pneumonia, encephalitis, pulmonary hypertension, and secondary bacterial superinfection.
- The disease is spread by contact with airborne discharges from the mucous membranes of infected people.
- Laboratory diagnosis include; Calcium alginate throat swab, culture on Bordet-Gengou medium, immunofluorescence and serological methods.
-Treatment of the disease with antibiotics (often erythromycin, azithromycin, clarithromycin or trimethoprim-sulfamethoxazole)
- Vaccination in children as preventive measure . The immunizations are often given in combination with tetanus and diphtheria immunizations, at ages 2, 4, and 6 months, and later at 15–18 months and 4–6 years
Tetanus
Tetanus is a serious and often fatal disease caused by the neurotoxin tetanospasmin which is produced by the Gram-positive, obligate anaerobic bacterium Clostridium tetani.
Symptoms
-The incubation period for tetanus is 3 days to as long as 15 weeks
- For neonates, the incubation period is 4 to 14 days, with 7 days being the average
- The first sign of tetanus is a mild jaw muscle spasm called lockjaw (trismus), followed by stiffness of the neck and back, risus sardonicus, difficulty swallowing, and muscle rigidity in the abdomen.
- Typical signs of tetanus include an increase in body temperature by 2 to 4°C, diaphoresis (excessive sweating), an elevated blood pressure, and an episodic rapid heart rate
Treatment
- Penicillin and metronidazole
- Human anti-tetanospasmin immunoglobulin should be given.
- Diazepam and DPT vaccine booster are also given
Syphilis
- a sexually transmitted disease (STD) that is caused by a spirochaete bacterium, Treponema pallidum
- The route of transmission for syphilis is almost invariably by sexual contact
Stages of syphilis
1.Primary syphilis
Chancres on penis due to primary syphilitic infection
Primary syphilis is manifested after an incubation period of 10-90 days (the average is 21 days) with a primary sore.
During the initial incubation period, individuals are asymptomatic.
The sore, called a chancre, is a firm, painless skin ulceration localized at the point of initial exposure to the bacterium, often on the penis, vagina or rectum.
Local lymph node swelling can occur. The primary lesion may persist for 4 to 6 weeks and then heal spontaneously.
2. Secondary syphilis
characterized by a skin rash that appears 1-6 months (commonly 6 to 8 weeks) after the primary infection
This is a symmetrical reddish-pink non-itchy rash on the trunk and extremities , nvolves the palms of the hands and the soles of the feet
in moist areas of the body the rash becomes flat broad whitish lesions called condylomata lata. Mucous patches may also appear on the genitals or in the mouth
common other symptoms include fever, sore throat, malaise, weight loss, headache, meningismus, and enlarged lymph nodes
3. Tertiary syphilis
occurs from as early as one year after the initial infection but can take up to ten years to manifest
This stage is characterised by gummas, soft, tumor-like growths, readily seen in the skin and mucous membranes, but which can occur almost anywhere in the body, often in the skeleton
Other characteristics of untreated syphilis include Charcot's joints (joint deformity),
Clutton's joints (bilateral knee effusions).
The more severe manifestations include neurosyphilis and cardiovascular syphilis.
Cardiovascular complications include aortic aortitis, aortic aneurysm, aneurysm of sinus of Valsalva, and aortic regurgitation, and are a frequent cause of death
Syphilitic aortitis can cause de Musset's sign
4.Congenital syphilis
Congenital syphilis is syphilis present in utero and at birth, and occurs when a child is born to a mother with secondary or tertiary syphilis.
Manifestations of congenital syphilis include abnormal x-rays; Hutchinson's teeth (centrally notched, widely-spaced peg-shaped upper central incisors);
mulberry molars (sixth year molars with multiple poorly developed cusps);
frontal bossing; saddle nose; poorly developed maxillae; enlarged liver; enlarged spleen; petechiae;
other skin rash; anemia; lymph node enlargement; jaundice; pseudoparalysis; and snuffles, the name given to rhinitis in this situation.
Rhagades, linear scars at the angles of the mouth and nose result from bacterial infection of skin lesions.
Death from congenital syphilis is usually through pulmonary hemorrhage.
Diagnosis
First effective test for syphilis, the Wassermann test
Rapid Plasma Reagin (RPR) and Venereal Disease Research Laboratory (VDRL) test are not as effective
Newer tests based on monoclonal antibodies and immunofluorescence, including Treponema pallidum haemagglutination assay (TPHA) and Fluorescent Treponemal Antibody Absorption (FTA-ABS) are more specific, but are still unable to rule out non-syphillis Treponomal infections such as Yaws and Pinta.
Microscopy of chancre fluid using dark ground illumination can be extremely quick and effective.
Treatment
first choice treatment for syphilis remains penicillin, in the form of benzathine penicillin G or aqueous procaine penicillin G injections
oral tetracyclines. In patients allergic to penicillins
Typhoid fever
- Typhoid fever (Enteric fever) is an illness caused by the bacterium Salmonella typhi
Symptoms
After infection, symptoms include:
a high fever from 39 °C to 40 °C (103 °F to 104 °F) that rises slowly
chills
bradycardia (slow heart rate)
weakness
diarrhea
headaches
myalgia (muscle pain)
lack of appetite
constipation
stomach pains
in some cases, a rash of flat, rose-colored spots called "rose spots"
extreme symptoms such as intestinal perforation or hemorrhage, delusions and confusion are also possible.
Diagnosis
Widal test (demonstration of salmonella antibodies against antigens O-somatic and H-flagellar)
Treatment
Antibiotics, such as ampicillin, chloramphenicol, trimethoprim-sulfamethoxazole, and ciprofloxacin, are commonly used to treat typhoid fever in developed countries
Usage of Ofloxacin along with Lactobacillus acidophilus is also recommended.
Amelogenesis and Enamel
Dental Anatomy
Amelogenesis and Enamel
Enamel is highly mineralized: 85% hydroxyapatite crystals
Enamel formation is a two-step process
The first step produces partially mineralized enamel: 30% (secretory)
The second step: Influx of minerals, removal of water and organic matrix (maturative)
Again, dentin is the prerequisite of enamel formation (reciprocal induction)
Stratum intermedium: high alkaline phosphatase activity
Differentiation of ameloblasts: Increase in glycogen contents
Formation of the enamel matrix
Enamel proteins, enzymes, metalloproteinases, phosphatases, etc.
Enamel proteins: amelogenins (90%), enamelin, tuftelin, and amelin
Amelogenins: bulk of organic matrix
Tuftelin: secreted at the early stages of amelogenesis (area of the DE junction)
Enamelin: binds to mineral
Amelin
Mineralization of enamel
No matrix vesicles
Immediate formation of crystallites
Intermingling of enamel crystallites with dentin
"Soft" enamel is formed
Histologic changes
Differentiation of inner enamel epithelium cells. They become ameloblasts
Tomes' processes: saw-toothed appearance
Collapse of dental organ
Formation of the reduced enamel epithelium
Hard tissue formation (Amelogenesis )
Enamel formation is called amelogenesis and occurs in the crown stage of tooth development. "Reciprocal induction" governs the relationship between the formation of dentin and enamel; dentin formation must always occur before enamel formation. Generally, enamel formation occurs in two stages: the secretory and maturation stages. Proteins and an organic matrix form a partially mineralized enamel in the secretory stage; the maturation stage completes enamel mineralization.
In the secretory stage, ameloblasts release enamel proteins that contribute to the enamel matrix, which is then partially mineralized by the enzyme alkaline phosphatase. The appearance of this mineralized tissue, which occurs usually around the third or fourth month of pregnancy, marks the first appearance of enamel in the body. Ameloblasts deposit enamel at the location of what become cusps of teeth alongside dentin. Enamel formation then continues outward, away from the center of the tooth.
In the maturation stage, the ameloblasts transport some of the substances used in enamel formation out of the enamel. Thus, the function of ameloblasts changes from enamel production, as occurs in the secretory stage, to transportation of substances. Most of the materials transported by ameloblasts in this stage are proteins used to complete mineralization. The important proteins involved are amelogenins, ameloblastins, enamelins, and tuftelins. By the end of this stage, the enamel has completed its mineralization.
Mental Age Assessment
PedodonticsMental Age Assessment
Mental age can be assessed using the following formula:
Mental Age = (Chronological Age × 100) / 10
Mental Age Descriptions
Below 69: Mentally retarded (intellectual disability).
Below 90: Low average intelligence.
90-110: Average intelligence. Most children fall within
this range.
Above 110: High average or superior intelligence.