NEET MDS Synopsis
The Sliding Filament mechanism of muscle contraction
PhysiologyThe Sliding Filament mechanism of muscle contraction.
When a muscle contracts the light I bands disappear and the dark A bands move closer together. This is due to the sliding of the actin and myosin myofilaments against one another. The Z-lines pull together and the sarcomere shortens
The thick myosin bands are not single myosin proteins but are made of multiple myosin molecules. Each myosin molecule is composed of two parts: the globular "head" and the elongated "tail". They are arranged to form the thick bands.
It is the myosin heads which form crossbridges that attach to binding sites on the actin molecules and then swivel to bring the Z-lines together
Likewise the thin bands are not single actin molecules. Actin is composed of globular proteins (G actin units) arranged to form a double coil (double alpha helix) which produces the thin filament. Each thin myofilament is wrapped by a tropomyosin protein, which in turn is connected to the troponin complex.
The tropomyosin-troponin combination blocks the active sites on the actin molecules preventing crossbridge formation. The troponin complex consists of three components: TnT, the part which attaches to tropomyosin, TnI, an inhibitory portion which attaches to actin, and TnC which binds calcium ions. When excess calcium ions are released they bind to the TnC causing the troponin-tropomyosin complex to move, releasing the blockage on the active sites. As soon as this happens the myosin heads bind to these active sites.
Periodontal Medications
PeriodontologyPeriodontal Medications and Their Uses
Periodontal medications play a crucial role in the management of periodontal
diseases, aiding in the treatment of infections, inflammation, and tissue
regeneration. Understanding the various types of medications and their specific
uses is essential for effective periodontal therapy.
Types of Periodontal Medications
Antibiotics:
Uses:
Used to treat bacterial infections associated with periodontal
disease.
Commonly prescribed antibiotics include amoxicillin,
metronidazole, and doxycycline.
Mechanism:
They help reduce the bacterial load in periodontal pockets,
promoting healing and reducing inflammation.
Antimicrobial Agents:
Chlorhexidine:
Uses: A topical antiseptic used as a mouth
rinse to reduce plaque and gingivitis.
Mechanism: It disrupts bacterial cell membranes
and inhibits bacterial growth.
Tetracycline:
Uses: Can be used topically in periodontal
pockets to reduce bacteria.
Mechanism: Inhibits protein synthesis in
bacteria, reducing their ability to cause infection.
Anti-Inflammatory Medications:
Non-Steroidal Anti-Inflammatory Drugs (NSAIDs):
Uses: Used to manage pain and inflammation
associated with periodontal disease.
Examples: Ibuprofen and naproxen.
Corticosteroids:
Uses: May be used in severe cases to reduce
inflammation.
Mechanism: Suppress the immune response and
reduce inflammation.
Local Delivery Systems:
Doxycycline Gel (Atridox):
Uses: A biodegradable gel that releases
doxycycline directly into periodontal pockets.
Mechanism: Provides localized antibiotic
therapy to reduce bacteria and inflammation.
Minocycline Microspheres (Arestin):
Uses: A localized antibiotic treatment that is
placed directly into periodontal pockets.
Mechanism: Releases minocycline over time to
combat infection.
Regenerative Agents:
Bone Grafts and Guided Tissue Regeneration (GTR) Materials:
Uses: Used in surgical procedures to promote
the regeneration of lost periodontal tissues.
Mechanism: Provide a scaffold for new tissue
growth and prevent the ingrowth of epithelium into the defect.
Desensitizing Agents:
Fluoride Varnishes:
Uses: Applied to sensitive areas to reduce
sensitivity and promote remineralization.
Mechanism: Strengthens enamel and reduces
sensitivity by occluding dentinal tubules.
Clinical Significance of Periodontal Medications
Management of Periodontal Disease:
Medications are essential in controlling infections and
inflammation, which are critical for the successful treatment of
periodontal diseases.
Adjunct to Non-Surgical Therapy:
Periodontal medications can enhance the effectiveness of
non-surgical treatments, such as scaling and root planing, by reducing
bacterial load and inflammation.
Surgical Interventions:
In surgical procedures, medications can aid in healing and
regeneration, improving outcomes for patients undergoing periodontal
surgery.
Patient Compliance:
Educating patients about the importance of medications in their
treatment plan can improve compliance and overall treatment success.
SINUS & FISTULA
General Surgery
Sinus
It is a tubular track lined by granulation tissue and open at one end which is at the surface,
eg. Tuberculous Sinus
Fistula
A tubular track lined by granulation tissue and open at both ends.at least one of which communicates with a hollow viscus. it can be internal or external.
Causes
1. Inadequate drainage
Abscess bursting at the non dependent part
Incision at the non-dependent part.
Narrow outer opening leading to collection of exudates in the cavity.
2. Presence of foreign body like sequestrum or slough.
3. Persistence of infection.
4. When the track is lined by epithelium
5. Specific causes, TB., Syphilis, etc.
6. Marked fibrosis of the wall with obliteration of blood vessels.
7. Poor general condition causing delayed healing.
Treatment
1. control of specific infection,
2. Thorough excision of track to open up the cavity. Removal of foreign body and scraping of the epithelium
3. Through Scrapping of the wall to expose healthy tissue
4. Wound laid open and allowed to heal from the bottom leaving no pocket,
Fentanyl
Pharmacology
Fentanyl (Sublimaze)
Related chemically to meperidine.
Approximately 80 times more potent than morphine.
Duration of action very short (t1/2 20 min).
Used mainly following general anesthesia.
Neurolept analgesia: Fentanyl & Droperidol (Innovar)
fentanyl in analgesic (2-10 µg/kg), or anaesthetic (30-100 µg/kg) doses seldom causes significant decreases in blood pressure when given alone, even in patients with poor LV function
hypotension following fentanyl is mostly due to bradycardia and can be prevented by the use of anticholinergics, sympathomimetics or agents such as pancuronium this is more likely to occur in patients with high pre-existing sympathetic tone
hypertension is the commonest disturbance with high dose fentanyl anaesthesia, usually accompanying intubation, sternotomy, or aortic root dissection
Marginal Resection
Oral and Maxillofacial SurgeryMarginal Resection
Marginal resection, also known as en bloc resection or
peripheral osteotomy, is a surgical procedure used to treat locally aggressive
benign lesions of the jaw. This technique involves the removal of the lesion
along with a margin of surrounding bone, while preserving the continuity of the
jaw.
Key Features of Marginal Resection
Indications:
Marginal resection is indicated for benign lesions with a known
propensity for recurrence, such as:
Ameloblastoma
Calcifying epithelial odontogenic tumor
Myxoma
Ameloblastic odontoma
Squamous odontogenic tumor
Benign chondroblastoma
Hemangioma
It is also indicated for recurrent lesions that have been previously
treated with enucleation alone.
Rationale:
Enucleation of locally aggressive lesions is not a safe procedure,
as it can lead to recurrence. Marginal resection is a more effective
approach, as it allows for the complete removal of the tumor along with
a margin of surrounding bone.
Benefits:
Complete Removal of the Tumor: Marginal resection
ensures the complete removal of the tumor, reducing the risk of
recurrence.
Preservation of Jaw Continuity: This procedure
allows for the preservation of jaw continuity, avoiding deformity,
disfigurement, and the need for secondary cosmetic surgery and
prosthetic rehabilitation.
Surgical Technique:
The procedure involves the removal of the lesion along with a margin
of surrounding bone. The extent of the resection is determined by the
size and location of the lesion, as well as the patient's overall health
and medical history.
Postoperative Care:
Patients may experience some discomfort and swelling following the
procedure, which can be managed with analgesics and anti-inflammatory
medications.
Regular follow-up appointments are necessary to monitor the healing
process and assess for any potential complications.
Outcomes:
Marginal resection is a highly effective procedure for treating
locally aggressive benign lesions of the jaw. It allows for the complete
removal of the tumor, while preserving jaw continuity and minimizing the
risk of recurrence.
Congestive heart failure (CHF)
General Pathology
Congestive heart failure (CHF)
A. Left-sided CHF
1. May result from nearly any heart disease affecting the left ventricle (e.g., ischemic heart disease, hypertension, valvular disease).
2. Common signs and symptoms include:
a. Dyspnea (shortness of breath) exacerbated by exertion.
b. Paroxysmal nocturnal dyspnea.
c. Orthopnea.
d. Tachypnea.
e. Pleural effusion.
f. Consequences include pulmonary edema.
B. Right-sided CHF
1. The most common cause of right heart failure is left heart failure. It uncommonly occurs in isolation. Other causes include left-sided lesions (mitral stenosis), pulmonary hypertension, cardiomyopathy, and tricuspid or pulmonary valvular disease.
2. Frequently presents with peripheral edema, especially in the ankles and feet (i.e., dependent edema), enlarged liver or spleen, and distention of the neck veins.
Muscles Around the Nose
AnatomyMuscles Around the Nose
The Nasalis Muscle
This muscle consists of a transverse (compressor naris) and alar (dilator naris) parts.
It is supplied by the buccal branch of the facial nerve.
Management of Septic Shock
Oral and Maxillofacial SurgeryManagement of Septic Shock
Septic shock is a life-threatening condition characterized by severe
infection leading to systemic inflammation, vasodilation, and impaired tissue
perfusion. Effective management is crucial to improve outcomes and reduce
mortality. The management of septic shock should be based on several key
principles:
Key Principles of Management
Early and Effective Volume Replacement:
Fluid Resuscitation: Initiate aggressive fluid
resuscitation with crystalloids (e.g., normal saline or lactated
Ringer's solution) to restore intravascular volume and improve
circulation.
Goal: Aim for a rapid infusion of 30 mL/kg of
crystalloid fluids within the first 3 hours of recognition of septic
shock.
Restoration of Tissue Perfusion:
Monitoring: Continuous monitoring of vital signs,
urine output, and laboratory parameters to assess the effectiveness of
resuscitation.
Target Blood Pressure: In most patients, a systolic
blood pressure of 90 to 100 mm Hg or a mean arterial pressure (MAP) of
70 to 75 mm Hg is considered acceptable.
Adequate Oxygen Supply to Cells:
Oxygen Delivery: Ensure adequate oxygen delivery to
tissues by maintaining hemoglobin saturation (SaO2) above 95% and
arterial oxygen tension (PaO2) above 60 mm Hg.
Hematocrit: Maintain hematocrit levels above 30% to
ensure sufficient oxygen-carrying capacity.
Control of Infection:
Antibiotic Therapy: Administer broad-spectrum
antibiotics as soon as possible, ideally within the first hour of
recognizing septic shock. Adjust based on culture results and
sensitivity.
Source Control: Identify and control the source of
infection (e.g., drainage of abscesses, removal of infected devices).
Pharmacological Management
Vasopressor Therapy:
Indication: If hypotension persists despite
adequate fluid resuscitation, vasopressors are required to increase
arterial pressure.
First-Line Agents:
Dopamine: Often the first choice due to its
ability to maintain organ blood flow, particularly to the kidneys
and mesenteric circulation. Typical dosing is 20 to 25
micrograms/kg/min.
Noradrenaline (Norepinephrine): Should be added
if hypotension persists despite dopamine administration. It is the
preferred vasopressor for septic shock due to its potent
vasoconstrictive properties.
Cardiac Output and Myocardial Function:
Dobutamine: If myocardial depression is suspected
(e.g., low cardiac output despite adequate blood pressure), dobutamine
can be added to improve cardiac output without significantly increasing
arterial pressure. This helps restore oxygen delivery to tissues.
Monitoring: Continuous monitoring of cardiac output
and systemic vascular resistance is essential to assess the
effectiveness of treatment.
Additional Considerations
Supportive Care: Provide supportive care, including
mechanical ventilation if necessary, and monitor for complications such as
acute respiratory distress syndrome (ARDS) or acute kidney injury (AKI).
Nutritional Support: Early enteral nutrition should be
initiated as soon as feasible to support metabolic needs and improve
outcomes.
Reassessment: Regularly reassess the patient's
hemodynamic status and adjust fluid and medication therapy accordingly.