NEET MDS Synopsis
Basic Properties of Gases
Physiology
Basic Properties of Gases
A. Dalton's Law of Partial Pressures
1. partial pressure - the "part" of the total air pressure caused by one component of a gas
Gas Percent Partial Pressure (P)
ALL AIR 100.0% 760 mm Hg
Nitrogen 78.6% 597 mm Hg (0.79 X 760)
Oxygen 20.9% l59 mm Hg (0.21 X 760)
CO2 0.04% 0.3 mm Hg (0.0004 X 760)
2. altitude - air pressure @ 10,000 ft = 563 mm Hg
3. scuba diving - air pressure @ 100 ft = 3000 mm Hg
B. Henry's Law of Gas Diffusion into Liquid
1. Henry's Law - a certain gas will diffuse INTO or OUT OF a liquid down its concentration gradient in proportion to its partial pressure
2. solubility - the ease with which a certain gas will "dissolve" into a liquid (like blood plasma)
HIGHest solubility in plasma Carbon Dioxide
Oxygen
LOWest solubility in plasma Nitrogen
C. Hyperbaric (Above normal pressure) Conditions
1. Creates HIGH gradient for gas entry into the body
2. therapeutic - oxygen forced into blood during: carbon monoxide poisoning, circulatory shock, asphyxiation, gangrene, tetanus, etc.
3. harmful - SCUBA divers may suffer the "bends" when they rise too quickly and Nitrogen gas "comes out of solution" and forms bubbles in the blood
Turbid Dentin
Conservative DentistryTurbid Dentin
Turbid Dentin: This term refers to a zone of dentin
that has undergone significant degradation due to bacterial invasion. It is
characterized by:
Widening and Distortion of Dentin Tubules: The
dentinal tubules in this zone become enlarged and distorted as they fill
with bacteria.
Minimal Mineral Content: There is very little
mineral present in turbid dentin, indicating a loss of structural
integrity.
Denatured Collagen: The collagen matrix in this
zone is irreversibly denatured, which compromises its mechanical
properties and ability to support the tooth structure.
Implications for Treatment
Irreversible Damage: Dentin in the turbid zone cannot
self-repair or remineralize. This means that any affected dentin must be
removed before a restoration can be placed.
Restorative Considerations: Proper identification and
removal of turbid dentin are critical to ensure the success of restorative
procedures. Failure to do so can lead to continued caries progression and
restoration failure.
The Skeleton of the Nose
AnatomyThe Skeleton of the Nose
The immovable bridge of the nose, the superior bony part of the nose, consists of the nasal bones, the frontal processes of the maxillae, and the nasal part of the frontal bones.
The movable cartilaginous part consists of five main cartilages and a few smaller ones.
The U-shaped alar nasal cartilages are free and movable.
They dilate and constrict the external nares when the muscles acting on the external nose contract.
The Nasal Cavities
The nasal cavities are entered through the anterior nares or nostrils.
They open into the nasopharynx through the choanae.
The Roof and Floor of the Nasal Cavity
The roof is curved and narrow, except at the posterior end.
The floor is wider than the roof.
It is formed from the palatine process of the maxilla and the horizontal plate of the palatine bone.
The Walls of the Nasal Cavity
The medial wall is formed by the nasal septum; it is usually smooth.
The lateral wall is uneven owing to the three longitudinal, scroll-shaped elevations, called the conchae (L. shells) or turbinates (L. shaped like a top).
These elevations are called the superior, middle and inferior conchae according to their position.
The superior and middle conchae are parts of the ethmoid bone, whereas the inferior conchae are separate bones.
The inferior and middle conchae project medially and inferiorly, producing air passageways called the inferior and middle meatus (L. passage). Note: the plural of "meatus" is the same as the singular.
The short superior conchae conceal the superior meatus.
The space posterosuperior to the superior concha is called the sphenoethmoidal recess.
Age changes in the dentition
Dental Anatomy
Age changes in the dentition
I. After the teeth have reached full occlusion, microscopic tooth movements occur to compensate for wear at the contact area (Mesial Drift) and occlusal surfaces (by Deposition of cementum at the root apex)
2. Attrition of incisal ridges and cusp tips may be so severe that dentin may become exposed and intrinsically stained
3. Secondary dentin may be formed in response to dental caries, trauma, and aging and result in decreased pulp size and tooth sensation
Bronchiectasis
General Pathology
Bronchiectasis
- Bronchiectasis is abnormal and irreversible dilatation of the bronchi and bronchioles (greater than 2 mm in diameter) secondary to inflammatory weakening of bronchial wall.
- Occur in childhood and early adult life
- Persistent cough with copious amount of foul smelling purulent sputum
Aetiopathogenesis
Bronchial wall destruction is due to:
- Endobronchial obstruction due to foreign body
- Infection due to local obstruction or impaired defence mechanism
Clinical conditions:
- Hereditary and congenital factors
- Obstruction
- Secondary complication
Hereditary and congenital factors:
- Congenital bronchiectasis due to developmental defects
- Cystic fibrosis causing defective secretion resulting in obstruction
- Hereditary immune defiency diseases
- Immotile cilia syndrome- immotile cilia of respiratory tract, sperms causing Kartagener’s syndrome (bronchiectasis, situs inversus and sinusitis) and male infertility
- Allergic bronchial asthma patients
Obstruction:
Localised variety in one part of bronchial system.
Obstruction can be due to
Foreign body
Endobronchial tumors
Hilar lymph nodes
Inflammatory scarring (TB)
Secondary complication:
Necrotizing pneumonia in Staph infection and TB
Morphologic changes
- Affects distal bronchi and bronchioles
- Lower lobes more frequently
- Lungs involved diffusely/segmentally
- Left lower lobe than right
- Pleura fibrotic & thickened adherent to chest wall
C/S lung: Honey-combed appearance
Microscopic examination:
Bronchiole-dilated
Bronchial epithelium-normal, ulcerated, squamous metaplasia
Bronchial wall-infiltration by ac & Ch inflammatory cells,
destruction of muscle, elastic tissue
Lung parenchyma-fibrosis, surrounding tissue pneumonia
Pleura-fibrotic and adherent
Skeletal System Functions
Anatomy
Provides a rigid support system
Protects delicate structures (e. g., the protection provided by the bones of the vertebral column to the spinal cord)
Bones supply calcium to the blood; are involved In the formation of blood cells (hemopoiesis)
Bones serve as the basis of attachment of muscles; form levers in the joint areas, aIlowing movement
SALIVARY GLANDS
Dental Anatomy
HISTOLOGY OF SALIVARY GLANDS
Parotid: so-called watery serous saliva rich in amylase
Submandibular gland: more mucinous
Sublingual: viscous saliva
Parotid Gland: The parotid is a serous secreting gland.
There are also fat cells in the parotid.
Submandibular Gland
This gland is serous and mucous secreting.
There are serous demilunes
This gland is more serous than mucous
Also fat cells
Sublingual Gland
Serous and mucous secreting
Serous cells in the form of demilunes on the mucous acini.
more mucous than serous cells
Minor Salivary Glands
Minor salivary glands are not found within gingiva and anterior part of the hard palate
Serous minor glands=von Ebner below the sulci of the circumvallate and folliate papillae of the tongue; palatine, glossopalatine glands are pure mucus; some lingual glands are also pure mucus
Functions
Protection: lubricant (glycoprotein); barrier against noxious stimuli; microbial toxins and minor traumas; washing non-adherent and acellular debris; calcium-binding proteins: formation of salivary pellicle
Buffering: bacteria require specific pH conditions; plaque microorganisms produce acids from sugars; phosphate ions and bicarbonate
Digestion: neutralizes esophageal contents, dilutes gastric chyme; forms food bolus; brakes starch
Taste: permits recognition of noxious substances; protein gustin necessary for growth and maturation of taste buds
Antimicrobial: lysozyme hydrolyzes cell walls of some bacteria; lactoferrin binds free iron and deprives bacteria of this essential element; IgA agglutinates microorganisms
Maintenance of tooth integrity: calcium and phosphate ions; ionic exchange with tooth surface
Tissue repair: bleeding time of oral tissues shorter than other tissues; resulting clot less solid than normal; remineralization
Danger Space
Oral and Maxillofacial SurgeryDanger Space: Anatomy and Clinical Significance
The danger space is an anatomical potential space located
between the alar fascia and the prevertebral fascia.
Understanding this space is crucial in the context of infections and their
potential spread within the neck and thoracic regions.
Anatomical Extent
Location: The danger space extends from the base
of the skull down to the posterior mediastinum,
reaching as far as the diaphragm. This extensive reach
makes it a significant pathway for the spread of infections.
Pathway for Infection Spread
Oropharyngeal Infections: Infections originating in the
oropharynx can spread to the danger space through the retropharyngeal
space. The retropharyngeal space is a potential space located
behind the pharynx and is clinically relevant in the context of infections,
particularly in children.
Connection to the Posterior Mediastinum: The danger
space is continuous with the posterior mediastinum, allowing for the
potential spread of infections from the neck to the thoracic cavity.
Mechanism of Infection Spread
Retropharyngeal Space: The spread of infection from the
retropharyngeal space to the danger space typically occurs at the junction
where the alar fascia and visceral fascia fuse,
particularly between the cervical vertebrae C6 and T4.
Rupture of Alar Fascia: Infection can spread by
rupturing through the alar fascia, which can lead to serious complications,
including mediastinitis, if the infection reaches the posterior mediastinum.
Clinical Implications
Infection Management: Awareness of the danger space is
critical for healthcare providers when evaluating and managing infections of
the head and neck. Prompt recognition and treatment of oropharyngeal
infections are essential to prevent their spread to the danger space and
beyond.
Surgical Considerations: Surgeons must be cautious
during procedures involving the neck to avoid inadvertently introducing
infections into the danger space or to recognize the potential for infection
spread during surgical interventions.