NEET MDS Synopsis
Microscopic structure
Anatomy
Cartilage model is covered with perichondrium that is converted to periosteum
Diaphysis-central shaft
Epiphysis-located at either end of the diaphysis
Growth in length of the bone is provided by the emetaphyseal plate located between the epiphyseal cartilage and the diaphysis
Blood capillaries and the mesenchymal cells infiltrate the spaces left by the destroyed chondrocytes
Osteoblasts are derived from the undifferentiated cells; form an osseous matrix in the cartilage
Bone appears at the site where there was cartilage
Microscopic structure
Compact bone is found on the exterior of all bones; canceIlous bone is found in the interior
Surface of compact bone is covered by periosteum that is attached by Sharpey's fibers
Blood vessels enter the periosteum via Volkmann's canals and then enter the haversian canals that are formed by the canaliculi and lacunae
Marrow
FiIls spaces of spongy bone
Contains blood vessels and blood ceIls in various stages of development
Types
Red bone marrow
Formation of red blood ceIls (RBCs) and some white blood cells (WBCs) in this location
Predominate type of marrow in newborn
Found in spongy bone of adults (sternum, ribs, vertebrae, and proximal epiphyses of long bones)
Yellow bone marrow
Fatty marrow
Generally replaces red bone marrow in the adult, except in areas mentioned above
Ossification is completed as the proximal epiphysis joins with the diaphysis between the twentieth and twenty-fifth year
TOXOPLASMOSIS
General Pathology
TOXOPLASMOSIS
Infection with Toxoplasma gondii, causing a spectrum of manifestations ranging from asymptomatic benign lymphadenopathy to life-threatening CNS disease, chorioretinitis, and mental retardation.
Symptomatic infections may present in several ways
Acute toxoplasmosis may mimic infectious mononucleosis with lymphadenopathy, fever, malaise, myalgia, hepatosplenomegaly, and pharyngitis. Atypical lymphocytosis, mild anemia, leukopenia, and slightly abnormal liver function tests are common. The syndrome may persist for weeks or months but is almost always self-limited.
A severe disseminated form characterized by pneumonitis, myocarditis, meningoencephalitis, polymyositis, diffuse maculopapular rash, high fevers, chills, and prostration. Acute fulminating disease is uncommon.
Congenital toxoplasmosis usually results from a primary (and often asymptomatic) acute infection acquired by the mother during pregnancy. The risk of transplacental infection increases from 15% to 30 to 60% for maternal infections acquired in the 1st, 2nd, or 3rd trimester of gestation, respectively
Drugs Used in Diabetes -pramlintide -Amylin mimetics
Pharmacology
Pramlintide -Amylin mimetics
Mechanism
synthetic analogue of human amylin that acts in conjunction with insulin
↓ release of glucagon
delays gastric emptying
Clinical use
type I and II DM
Seddon’s Classification of Nerve Injuries
Oral and Maxillofacial SurgerySeddon’s Classification of Nerve Injuries
Neuropraxia:
Definition: This is the mildest form of nerve
injury, often caused by compression or mild trauma.
Sunderland Classification: Type I (10).
Nerve Sheath: Intact; the surrounding connective
tissue remains undamaged.
Axons: Intact; the nerve fibers are not severed.
Wallerian Degeneration: None; there is no
degeneration of the distal nerve segment.
Conduction Failure: Transitory; there may be
temporary loss of function, but it is reversible.
Spontaneous Recovery: Complete recovery is
expected.
Time of Recovery: Typically within 4 weeks.
Axonotmesis:
Definition: This injury involves damage to the
axons while the nerve sheath remains intact. It is often caused by more
severe trauma, such as crush injuries.
Sunderland Classification: Type II (20), Type III
(30), Type IV (40).
Nerve Sheath: Intact; the connective tissue
framework is preserved.
Axons: Interrupted; the nerve fibers are damaged
but the sheath allows for potential regeneration.
Wallerian Degeneration: Yes, partial; degeneration
occurs in the distal segment of the nerve.
Conduction Failure: Prolonged; there is a
longer-lasting loss of function.
Spontaneous Recovery: Partial recovery is possible,
depending on the extent of the injury.
Time of Recovery: Recovery may take months.
Neurotmesis:
Definition: This is the most severe type of nerve
injury, where both the axons and the nerve sheath are disrupted. It
often results from lacerations or severe trauma.
Sunderland Classification: Type V (50).
Nerve Sheath: Interrupted; the connective tissue is
damaged, complicating regeneration.
Axons: Interrupted; the nerve fibers are completely
severed.
Wallerian Degeneration: Yes, complete; degeneration
occurs in both the proximal and distal segments of the nerve.
Conduction Failure: Permanent; there is a lasting
loss of function.
Spontaneous Recovery: Poor to none; recovery is
unlikely without surgical intervention.
Time of Recovery: Recovery may begin by 3 months,
if at all.
Acid Etching on Enamel
Conservative DentistryEffects of Acid Etching on Enamel
Acid etching is a critical step in various dental procedures, particularly in
the bonding of restorative materials to tooth structure. This process modifies
the enamel surface to enhance adhesion and improve the effectiveness of dental
materials. Below are the key effects of acid etching on enamel:
1. Removal of Pellicle
Pellicle Removal: Acid etching effectively removes the
acquired pellicle, a thin film of proteins and glycoproteins that forms on
the enamel surface after tooth cleaning.
Exposure of Inorganic Crystalline Component: By
removing the pellicle, the underlying inorganic crystalline structure of the
enamel is exposed, allowing for better interaction with bonding agents.
2. Creation of a Porous Layer
Porous Layer Formation: Acid etching creates a porous
layer on the enamel surface.
Depth of Pores: The depth of these pores typically
ranges from 5 to 10 micrometers (µm), depending on the concentration and
duration of the acid application.
Increased Surface Area: The formation of these pores
increases the surface area available for bonding, enhancing the mechanical
retention of restorative materials.
3. Increased Wettability
Wettability Improvement: Acid etching increases the
wettability of the enamel surface.
Significance: Improved wettability allows bonding
agents to spread more easily over the etched surface, facilitating better
adhesion and reducing the risk of voids or gaps.
4. Increased Surface Energy
Surface Energy Elevation: The etching process raises
the surface energy of the enamel.
Impact on Bonding: Higher surface energy enhances the
ability of bonding agents to adhere to the enamel, promoting a stronger bond
between the tooth structure and the restorative material.
COENZYMES
Biochemistry
COENZYMES
Enzymes may be simple proteins, or complex enzymes.
A complex enzyme contains a non-protein part, called as prosthetic group (co-enzymes).
Coenzymes are heat stable low molecular weight organic compound. The combined form of protein and the co-enzyme are called as holo-enzyme. The heat labile or unstable part of the holo-enzyme is called as apo-enzyme. The apo-enzyme gives necessary three dimensional structures required for the enzymatic chemical reaction.
Co-enzymes are very essential for the biological activities of the enzyme.
Co-enzymes combine loosely with apo-enzyme and are released easily by dialysis. Most of the co-enzymes are derivatives of vitamin B complex
The Submandibular Glands
AnatomyThe Submandibular Glands
Each of these U-shaped salivary glands is about the size of a thumb and lies along the body of the mandible.
It is partly superior and partly inferior to the posterior 1/2 of the base of the mandible.
It is partly superficial and partly deep to the mylohyoid muscle.
The submandibular duct arises from the portion of the gland that lies between the mylohyoid and hyoglossus muscle.
The duct passes deep and then superficial to the lingual nerve.
It opens by one to three orifices on a small sublingual papilla beside the lingual frenulum.
The submandibular gland is supplied by parasympathetic, secretomotor fibres from the submandibular ganglion (preganglionic fibres from the chorda tympani via the lingual nerve).
BETA-LACTAM ANTIBIOTICS
Pharmacology
Carbapenems: Broadest spectrum of beta-lactam antibiotics.
imipenem with cilastatin
meropenem
ertapenem
Monobactams: Unlike other beta-lactams, there is no fused ring attached to beta-lactam nucleus. Thus, there is less probability of cross-sensitivity reactions.
aztreonam
Beta-lactamase Inhibitors No antimicrobial activity. Their sole purpose is to prevent the inactivation of beta-lactam antibiotics by beta-lactamases, and as such, they are co-administered with beta-lactam antibiotics.
clavulanic acid
tazobactam
sulbactam