NEET MDS Synopsis
Morphine
Pharmacology
Morphine
Morphine is effective orally, but is much less effective than when given parenterally due to first-pass metabolism in the liver. Metabolism involves glucuronide formation, the product of which is excreted in the urine.
1. Central Nervous System Effects
• Morphine has mixed depressant and stimulatory actions on the CNS.
• Analgesia:
• Dysphoria – Euphoria
- morphine directly stimulates the chemoreceptor trigger zone, but later depresses the vomiting center in the brain stem. This center is outside the blood/brain barrier.
- opiates appear to relieve anxiety
• Morphine causes the release of histamine and abolishes hunger.
- causes the body to feel warm and the face and nose to itch.
• Pupils are constricted.- due to stimulation of the nuclei of the third cranial nerves.
- tolerance does not develop to this effect.
• Cough reflex is inhibited. - this is not a stereospecific effect.
- dextromethorphan will suppress cough but will not produce analgesia.
• Respiration is depressed
- due to a direct effect on the brain stem respiratory center.
- death from narcotic overdose is nearly always due to respiratory arrest.
- the mechanism of respiratory depression involves:
• a reduction in the responsiveness of the brain stem respiratory centers to an increase in pCO2.
• depression of brain stem centers that regulate respiratory rhythm.
- hypoxic stimulation of respiration is less affected and O2 administration can produce apnea.
2. Cardiovascular Effects
• Postural orthostatic hypotension.- due primarily to peripheral vasodilation, which may be due in part to histamine release.
• Cerebral circulation is also indirectly influenced by increased pCO2, which leads to cerebral vasodilation and increased cerebrospinal fluid pressure.
• In congestive heart failure, morphine decreases the left ventricular workload and myocardial oxygen demand.
3. Endocrine Effects
• Increases prolactin secretion
• Increases vasopressin (ADH) secretion
• Decreases pituitary gonadotropin (LH & FSH) secretion.
• Decreases stress induced ACTH secretion.
4. Gastrointestinal Tract Effects
• Constipation (tolerance does not develop to this effect).
• Several of these agents can be used in the treatment of diarrhea.
There is an increase in smooth muscle tone and a decrease in propulsive contractions.
Adverse Reactions
Generally direct extensions of their pharmacological actions.
1. respiratory depression, apnea
2. nausea and vomiting
3. dizziness, orthostatic hypotension, edema
4. mental clouding, drowsiness
5. constipation, ileus
6. biliary spasm (colic)
7. dry mouth
8. urine retention, urinary hesitancy
9. hypersensitivity reactions (contact dermatitis, urticaria)
Precautions
1. respiratory depression, particularly in the newborn
3. orthostatic hypotension
4. histamine release (asthma, shock)
5. drug interactions (other CNS depressants)
6. tolerance:
- analgesia, euphoria, nausea and vomiting, respiratory depression
7. physical dependence (psychological & physiological)
Dautrey Procedure
General SurgeryDautrey Procedure
The Dautrey procedure is a surgical intervention aimed at
preventing dislocation of the temporomandibular joint (TMJ) by creating a
mechanical obstacle that restricts abnormal forward translation of the condylar
head. This technique is particularly beneficial for patients who experience
recurrent TMJ dislocations or subluxations, especially when conservative
management strategies have proven ineffective.
Indications:
The Dautrey procedure is indicated for patients with a history of
recurrent TMJ dislocations. It is particularly useful when conservative
treatments, such as physical therapy or splint therapy, have failed to
provide adequate stabilization of the joint.
Surgical Technique:
Osteotomy of the Zygomatic Arch: The procedure
begins with an osteotomy, which involves surgically cutting the
zygomatic arch, the bony structure that forms the prominence of the
cheek.
Depressing the Zygomatic Arch: After the osteotomy,
the zygomatic arch is depressed in front of the condylar head. This
depression creates a physical barrier that acts as an obstacle to the
forward movement of the condylar head during jaw opening or excessive
movement.
Stabilization: The newly positioned zygomatic arch
limits the range of motion of the condylar head, thereby reducing the
risk of dislocation during functional activities such as chewing or
speaking.
Mechanism of Action:
By altering the position of the zygomatic arch, the Dautrey
procedure effectively changes the biomechanics of the TMJ. The new
position of the zygomatic arch prevents the condylar head from
translating too far forward, which is a common cause of dislocation.
Postoperative Care:
Following the procedure, patients may require a period of recovery
and rehabilitation. This may include:
Dietary Modifications: Soft diet to minimize
stress on the TMJ during the healing process.
Pain Management: Use of analgesics to manage
postoperative discomfort.
Physical Therapy: Exercises to restore normal
function and range of motion in the jaw.
Outcomes:
The Dautrey procedure has been shown to be effective in preventing
recurrent TMJ dislocations. Patients often experience improved joint
stability and a better quality of life following the surgery. Successful
outcomes can lead to reduced pain, improved jaw function, and enhanced
overall satisfaction with treatment.
Leeway Space
Pedodontics
Leeway Space
Leeway space refers to the size differential between the primary posterior
teeth (which include the primary canines, first molars, and second
molars) and their permanent successors, specifically the permanent canines and
first and second premolars. This space is significant in orthodontics
and pediatric dentistry because it plays a crucial role in accommodating the
permanent dentition as the primary teeth exfoliate.
Size Differential
Typically, the combined width of the primary posterior teeth is greater than
that of the permanent successors. For instance, the sum of the widths of the
primary canine, first molar, and second molar is larger than the combined widths
of the permanent canine and the first and second premolars. This inherent size
difference creates a natural space when the primary teeth are lost.
Measurement of Leeway Space
On average, the leeway space provides approximately:
3.1 mm of space per side in the mandibular arch (lower
jaw)
1.3 mm of space per side in the maxillary arch (upper
jaw)
This space can be crucial for alleviating crowding in the dental arch,
particularly in cases where there is insufficient space for the permanent teeth
to erupt properly.
Clinical Implications
When primary teeth fall out, the leeway space can be utilized to help relieve
crowding. If this space is not preserved, the permanent first molars tend to
drift forward into the available space, effectively closing the leeway space.
This forward drift can lead to misalignment and crowding of the permanent teeth,
potentially necessitating orthodontic intervention later on.
Management of Leeway Space
To maintain the leeway space, dental professionals may employ various
strategies, including:
Space maintainers: These are devices used to hold the
space open after the loss of primary teeth, preventing adjacent teeth from
drifting into the space.
Monitoring eruption patterns: Regular dental check-ups
can help track the eruption of permanent teeth and the status of leeway
space, allowing for timely interventions if crowding begins to develop.
Heart sounds
Physiology
Heart sounds
Heart sounds are a result of beating heart and resultant blood flow . that could be detected by a stethoscope during auscultation . Auscultation is a part of physical examination that doctors have to practice them perfectly.
Before discussion the origin and nature of the heart sounds we have to distinguish between the heart sounds and hurt murmurs. Heart murmurs are pathological noises that results from abnormal blood flow in the heart or blood vessels.
Physiologically , blood flow has a laminar pattern , which means that blood flows in form of layers , where the central layer is the most rapid . Laminar blood flow could be turned into turbulent one .
Turbulent blood flow is a result of stenotic ( narrowed ) valves or blood vessels , insufficient valves , roughened vessels` wall or endocardium , and many diseases . The turbulent blood flow causes noisy murmurs inside or outside the heart.
Heart sounds ( especially first and second sounds ) are mainly a result of closure of the valves of the heart . While the third sound is a result of vibration of ventricular wall and the leaflets of the opened AV valves after rapid inflow of blood from the atria to ventricles .
Third heart sound is physiologic in children but pathological in adults.
The four heart sound is a result of the atrial systole and vibration of the AV valves , due to blood rush during atrial systole . It is inaudible neither in adults nor in children . It is just detectable by the phonocardiogram .
Characteristic of heart sounds :
1. First heart sound (S1 , lub ) : a soft and low pitch sound, caused by closure of AV valves.Usually has two components ( M1( mitral ) and T1 ( tricuspid ). Normally M1 preceads T1.
2. Second heart sound ( S2 , dub) : sharp and high pitch sound . caused by closure of semilunar valves. It also has two components A2 ( aortic) and P2 ( pulmonary) . A2 preceads P2.
3. Third heart sound (S3) : low pitched sound.
4. Fourth heart sound ( S4) very low pitched sound.
As we notice : the first three sounds are related to ventricular activity , while the fourth heart sound is related to atrial activity.
Closure of valves is not the direct cause for heart sounds , but sharp blocking of blood of backward returning of blood by the closing valve is the direct cause.
Obstetric forceps delivery
Obstetrics and Gynaecology
a forcep is a metal device that enables gentle rotation and/or traction of the fetal head during vaginal delivery
Types
Kielland: enables rotation and traction of the fetal head
Simpson: only enables traction of the fetal head
Barton: used for occiput transverse position of the fetal head
Piper: used to deliver the fetal head during breech delivery
Classification
Outlet: fetal head lies on the pelvic floor
Low: fetal head is below +2 station (not on the pelvic floor)
Mid: fetal head is below 0 station (not at +2 station)
High: fetal head is not engaged
Indications
Prolonged second stage of labor
Breech presentation
Nonreassuring fetal heart rate
To avoid/assist maternal pushing efforts
Prerequisites
Clinically adequate pelvic dimensions (see “Mechanics of childbirth”)
Full cervical dilation
Engagement of the fetal head
Knowledge of exact position and attitude of the fetal head
Emptied maternal bladder
No suspicion of fetal bleeding or bone mineralization disorders
Advantages
Scalp injuries are less common
Cannot undergo decompression and “pop off”
Complications
Maternal: obstetric lacerations (cervix, vagina, uterus)
Fetal: head or soft-tissue trauma (e.g., scalp lacerations, injured ears), facial nerve palsy
Muscles acting on the Temporomandibular Joint
AnatomyMuscles acting on the Temporomandibular Joint
Movements of the temporomandibular joint are chiefly from the action of the muscles of mastication.
The temporalis, masseter, and medial pterygoid muscles produce biting movements.
The lateral pterygoid muscles protrude the mandible with the help from the medial pterygoid muscles and retruded largely by the posterior fibres of the temporalis muscle.
Gravity is sufficient to depress the mandible, but if there is resistance, the lateral pterygoid, suprahyoid and infrahyoid, mylohyoid and anterior digastric muscles are activated.
Actions
Muscles
Depression (Open mouth)
Lateral pterygoid
Suprahyoid
Infrahyoid
Elevation (Close mouth)
Temporalis
Masseter
Medial pterygoid
Protrusion (Protrude chin)
Masseter (superficial fibres)
Lateral pterygoid
Medial pterygoid
Retrusion (Retrude chin)
Temporalis
Masseter (deep fibres)
Side-to-side movements (grinding and chewing)
Temporalis on same side
Pterygoid muscles of opposite side
Masseter
Enzymes
General Microbiology
Enzymes:
Serum lysozyme:
Provides innate & nonspecific immunity
Lysozyme is a hydrolytic enzyme capable of digesting bacterial cell walls containing peptidoglycan
• In the process of cell death, lysosomal NZs fxn mainly to aulolyse necrotic cells (NOT “mediate cell degradation”)
• Attacks bacterial cells by breaking the bond between NAG and NAM.
• Peptidoglycan – the rigid component of cell walls in most bacteria – not found in archaebacteria or eukaryotic cells
• Lysozyme is found in serum, tears, saliva, egg whites & phagocytic cells protecting the host nonspecifically from microorganisms
Superoxide dismutase: catalyzes the destruction of O2 free radicals protecting O2-metabolizing cells against harmful effects
Catalase:
- catalyzes the decomposition of H2O2 into H2O & O2
- Aerobic bacteria and facultative anaerobic w/ catalase are able to resist the effects of H2O2
- Anaerobic bacteria w/o catalase are sensitive to H2O2 (Peroxide), like Strep
- Anaerobic bacteria (obligate anaerobes) lack superoxide dismutase or catalase
- Staph makes catalase, where Strep does not have enough staff to make it
Coagulase
- Converts Fibronogen to fibrin
• Coagulase test is the prime criterion for classifying a bug as Staph aureus – from other Staph species
• Coagulase is important to the pathogenicity of S. aureus because it helps to establish the typical abscess lesion
• Coagulase also coats the surface w/ fibrin upon contact w/ blood, making it harder to phagocytize
Intrinsic Muscles of the Tongue
AnatomyIntrinsic Muscles of the Tongue
The Superior Longitudinal Muscle of the Tongue
The muscle forms a thin layer deep to the mucous membrane on the dorsum of the tongue, running from its tip to its root.
It arises from the submucosal fibrous layer and the lingual septum and inserts mainly into the mucous membrane.
This muscle curls the tip and sides of the tongue superiorly, making the dorsum of the tongue concave.
The Inferior Longitudinal Muscle of the Tongue
This muscle consists of a narrow band close to the inferior surface of the tongue.
It extends from the tip to the root of the tongue.
Some of its fibres attach to the hyoid bone.
This muscle curls the tip of the tongue inferiorly, making the dorsum of the tongue convex.
The Transverse Muscle of the Tongue
This muscle lies deep to the superior longitudinal muscle.
It arises from the fibrous lingual septum and runs lateral to its right and left margins.
Its fibres are inserted into the submucosal fibrous tissue.
The transverse muscle narrows and increases the height of the tongue.
The Vertical Muscle of the Tongue
This muscle runs inferolaterally from the dorsum of the tongue.
It flattens and broadens the tongue.
Acting with the transverse muscle, it increases the length of the tongue.