NEET MDS Synopsis
Muscles of the Forehead
AnatomyMuscles Around the Mouth
The sphincter of the mouth is orbicularis oris and the dilator muscles radiate outward from the lips like the spokes of a wheel.
Orbicularis Oris Muscle
This muscle encircles the mouth and is the sphincter of the oral aperture
This muscle (1) closes the lips, (2) protrudes them and (3) compresses them against the teeth.
It plays an important role in articulation and mastication. Together with the buccinator muscle, it helps to hold the food between the teeth during mastication.
Zygomaticus Major Muscle
It extends from the zygomatic bone to the angle of the mouth.
It draws the corner of the moth superolaterally during smiling and laughing.
Zygomaticus Minor Muscle
This is a narrow slip of muscle, and passes obliquely from the zygomatic bone to the orbicularis oris.
It helps raise the upper lip when showing contempt or to deepen the nasolabial sulcus when showing sadness.
The Buccinator Muscle
This is a thin, flat, rectangular muscle.
It is attached laterally to the alveolar processes of the maxilla and mandible, opposite the molar teeth and the pterygomandibular raphe.
Medially, its fibres mingle with those of orbicularis oris.Innervation: the buccal branch of facial.
It aids mastication and swallowing by pushing the cheeks against the molar teeth during chewing.
ACRYLIC RESINS
Dental Materials
ACRYLIC RESINS
Use. Acrylic (unfilled) resins are used as temporary crown material. Temporary crowns are placed to protect the crown preparation and provide patient comfort during the time the permanent crown is being constructed
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.
Innervation of the Skin
AnatomyInnervation of the Skin
Innervation of the skin is mainly through the three branches of the trigeminal nerve (CN V).
Some skin over the angle of the mandible and anterior and posterior of the auricle is supplied by the great auricular nerve from the cervical plexus.
Some cutaneous branches of the auricular branch of the facial nerve also supplies skin on both sides of the auricle.
The trigeminal nerve is the general sensory nerve to the head, particularly the face, and is the motor nerve to the muscles of mastication.
The Ophthalmic Nerve
This is the superior division of the trigeminal nerve, the smallest of the three branches and is wholly sensory.
The ophthalmic nerve divides into three branches: the nasociliary, frontal and lacrimal just before entering the orbit through the superior orbital fissure.
The nasociliary nerve supplies the tip of the nose through the external nasal branch of the anterior ethmoidal nerve.
The frontal nerve is the direct continuation of CN V1 and divides into two branches, the supraorbital and supratrochlear.
The supratrochlear nerve supplies the middle part of the forehead.
The supraorbital nerve supplies the lateral part and the front of the scalp.
The lacrimal nerve, the smallest of the main ophthalmic branches, emerges over the superolateral orbital margin to supply the lacrimal gland and the lateral part of the upper eyelid.
The Maxillary Nerve
This is the intermediate division of the trigeminal nerve.
It has three cutaneous branches.
The infraorbital nerve is the largest terminal branch of the maxillary nerve.
It passes through the infraorbital foramen and breaks up into branches that supplies the skin on the lateral aspect of the nose, upper lip and lower eyelid.
The zygomaticofacial nerve, a small branch of the maxillary, emerges from the zygomatic bone from a foramen with the same name.
It supplies the skin over the zygomatic bone.
The zygomaticotemporal nerve emerges from the zygomatic bone from foramen of the same name.
It supplies the skin over the temporal region.
The Mandibular Nerve
This is the inferior division of the trigeminal nerve.
Of the three division of the trigeminal nerve, CN V3 is the only one that carries motor fibres (to the muscles of mastication).
The main sensory branches of the mandibular nerve are the buccal, auriculotemporal, inferior alveolar and lingual nerves.
The buccal nerve is a small branch of the mandibular that emerges from deep to the ramus of the mandible.
It supplies the skin of the cheek over the buccinator muscle, the mucous membrane lining the cheek, and the buccal surface of the gingiva.
The auriculotemporal nerve passes medially to the neck of the mandible and then turns superiorly, posterior to its head and anterior to the auricle. It then crosses over the root of the zygomatic process of the temporal bone, deep to the superficial temporal artery.
It supplies the auricle, external acoustic meatus, tympanic membrane, and the skin in the temporal region.
The inferior alveolar nerve is the large terminal branch of the posterior division of the mandibular nerve (the lingual nerve is the other terminal branch).
It enters the mandible through the mandibular foramen to the mandibular canal. In the canal, it gives branches to the mandibular teeth.
Opposite the mental foramen, this nerve divides into the mental nerve and the incisive nerve.
The incisive nerve supplies the incisor teeth, the adjacent gingiva and the mucosa of the lower lip.
The mental nerve emerges from the mental foramen and supplies the skin of the chin and the skin and mucous membrane of the lower lip and gingiva.
The lingual nerve is the smaller terminal branch of the mandibular nerve.
It supplies the general sensory fibres to the anterior two-thirds of the tongue, the floor of the mouth and the gingivae of the mandibular teeth.
Diseases from Str. pyogenes (Group A strep)
General Pathology
Diseases from Str. pyogenes (Group A strep)
1. Streptococcal pharyngitis. Most frequent Group A infection. Throat has gray-white exudate. Infection may become systemic into blood, sinuses, jugular vein, meninges. In less than a week the M-protein and capsule production decrease, and transmission declines.
2. Skin infections, such as impetigo. Especially in children. Different M-proteins than in pharyngitis. Skin infections associated with edema and red streaking (characteristic).
3. Necrotizing fasciitis/myositis. Infection of deeper tissue advances despite antibiotics.
4. Scarlet fever. Caused by phage-associated erythrogenic toxin-producing strains. Toxins cause cardiac, renal, and other systemic failures. Rash is very red with a sand-papery feel and shedding of superficial skin.
5. Toxic Shock Syndrome. Parallels the toxic shock caused by TSST-carrying Staph. aureus.
6. Non-suppurative, post-infection diseases.
Rheumatic fever (myocarditis, cardiac valve disease, polyarthralgia, rashes. Occurs two weeks after a pharyngeal infection)
Glomerulonephritis (Occurs two weeks after pharyngeal or skin infections. Often due to immunologic reaction to M-protein type 12)
Partial Pressures of O2 and CO2 in the body
Physiology
Partial Pressures of O2 and CO2 in the body (normal, resting conditions):
Alveoli
PO2 = 100 mm Hg
PCO2 = 40 mm Hg
Alveolar capillaries
Entering the alveolar capillaries
PO2 = 40 mm Hg (relatively low because this blood has just returned from the systemic circulation & has lost much of its oxygen)
PCO2 = 45 mm Hg (relatively high because the blood returning from the systemic circulation has picked up carbon dioxide)
While in the alveolar capillaries, the diffusion of gasses occurs: oxygen diffuses from the alveoli into the blood & carbon dioxide from the blood into the alveoli.
Leaving the alveolar capillaries
PO2 = 100 mm Hg
PCO2 = 40 mm Hg
Blood leaving the alveolar capillaries returns to the left atrium & is pumped by the left ventricle into the systemic circulation. This blood travels through arteries & arterioles and into the systemic, or body, capillaries. As blood travels through arteries & arterioles, no gas exchange occurs.
Entering the systemic capillaries
PO2 = 100 mm Hg
PCO2 = 40 mm Hg
Body cells (resting conditions)
PO2 = 40 mm Hg
PCO2 = 45 mm Hg
Because of the differences in partial pressures of oxygen & carbon dioxide in the systemic capillaries & the body cells, oxygen diffuses from the blood & into the cells, while carbon dioxide diffuses from the cells into the blood.
Leaving the systemic capillaries
PO2 = 40 mm Hg
PCO2 = 45 mm Hg
Blood leaving the systemic capillaries returns to the heart (right atrium) via venules & veins (and no gas exchange occurs while blood is in venules & veins). This blood is then pumped to the lungs (and the alveolar capillaries) by the right ventricle.
The Hemoglobin Buffer Systems
Biochemistry
The Hemoglobin Buffer Systems
These buffer systems are involved in buffering CO2 inside erythrocytes. The buffering capacity of hemoglobin depends on its oxygenation and deoxygenation. Inside the erythrocytes, CO2 combines with H2O to form carbonic acid (H2CO3) under the action of carbonic anhydrase.
At the blood pH 7.4, H2CO3 dissociates into H+ and HCO3 − and needs immediate buffering.
SPIROCHETAL DISEASE -Syphilis
General Pathology
SPIROCHETAL DISEASE
Syphilis
A contagious systemic disease caused by the spirochete Treponema pallidum, characterized by sequential clinical stages and by years of latency.
ACQUIRED SYPHILIS
T. pallidum is a delicate spiral organism about 0.25 µm wide and from 5 to 20 µm long, identified by characteristic morphology and motility with a darkfield microscope or fluorescent techniques
In acquired syphilis, T. pallidum enters through the mucous membranes or skin, reaches the regional lymph nodes within hours, and rapidly disseminates throughout the body. In all stages of disease, perivascular infiltration of lymphocytes, plasma cells, and, later, fibroblasts causes swelling and proliferation of the endothelium of the smaller blood vessels, leading to endarteritis obliterans.
In late syphilis, T. pallidum elicits a granulomatous-like (gummatous) reaction causing masses, ulcerations, and necrosis. Inflammation may subside despite progressive damage, especially in the cardiovascular and central nervous systems.
The CNS is invaded early in the infection. During the secondary stage of the disease, > 30% of patients have abnormal CSF and may have symptoms of meningitis
Symptoms, Signs, and Course
The incubation period of primary syphilis can vary from 1 to 13 wk but is usually from 3 to 4 wk. The disease may present at any stage and long after the initial infection
Primary stage: The primary lesion, or chancre generally evolves and heals within 4 to 8 wk in untreated patients. After inoculation, a red papule quickly erodes to form a painless ulcer with an indurated base that, when abraded, exudes a clear serum containing numerous spirochetes
The regional lymph nodes usually enlarge painlessly and are firm, discrete, and nontender. Chancres occur on the penis, anus, and rectum in men and on the vulva, cervix, and perineum in women. Chancres may also occur on the lips or the oropharyngeal or anogenital mucous membranes.
Secondary stage: Cutaneous rashes usually appear within 6 to 12 wk after infection and are most florid after 3 to 4 mo.
Frequently, generalized, nontender, firm, discrete lymphadenopathy and hepatosplenomegaly are palpable. Over 80% of patients have mucocutaneous lesions, 50% have generalized lymphadenopathy, and about 10% have lesions of the eyes (uveitis), bones (periostitis), joints, meninges, kidneys (glomerulitis), liver, and spleen.
Acute syphilitic meningitis may develop, with headache, neck stiffness, cranial nerve lesions, deafness, and, occasionally, papilledema.
Condyloma lata--hypertrophic, flattened, dull pink or gray papules at the mucocutaneous junctions and in moist areas of the skin--are extremely infectious. Hair often falls out in patches, leaving a moth-eaten appearance (alopecia areata).
Latent stage
In the early latent period (< 2 yr after infection), infectious mucocutaneous relapses may occur, but after 2 yr contagious lesions rarely develop, and the patient appears normal. About 1/3 of untreated persons develop late syphilis
Late or tertiary stage: Lesions may be clinically described as (1) benign tertiary syphilis of the skin, bone, and viscera, (2) cardiovascular syphilis, or (3) neurosyphilis.
The typical lesion is a gumma, an inflammatory mass that evolves to necrosis and fibrosis and that is frequently localized but may diffusely infiltrate an organ or tissue
Benign tertiary syphilis of the bones results in either periostitis with bone formation or osteitis with destructive lesions causing a deep, boring pain, characteristically worse at night. A lump or swelling may be palpable.
Cardiovascular syphilis: A dilated, usually fusiform aneurysm of the ascending or transverse aorta, narrowing of the coronary ostia, or aortic valvular insufficiency usually appears 10 to 25 yr after the initial infection
Neurosyphilis
In meningovascular neurosyphilis, brain involvement is signaled by headache, dizziness, poor concentration, lassitude, insomnia, neck stiffness, and blurred vision. Mental confusion, epileptiform attacks, papilledema, aphasia, and mono- or hemiplegia may also occur
Diagnosis:
Two classes of serologic tests for syphilis (STS) aid in diagnosing syphilis and other related treponemal diseases: screening, nontreponemal tests using lipoid antigens detect syphilitic reagin and include the Venereal Disease Research Laboratory (VDRL) and the rapid plasma reagin (RPR) tests. Specific treponemal tests detect antitreponemal antibodies and include fluorescent treponemal antibody absorption (FTA-ABS) test, microhemagglutination assay for antibodies to T. pallidum (MHA-TP), and Treponema pallidum hemagglutination assay (TPHA).
In darkfield microscopy, light is directed obliquely through the slide so that rays striking the spirochetes cause them to appear as bright, motile, narrow coils against a dark background