NEET MDS Shorts
962756
PhysiologyVitamin D is essential for the absorption of calcium and phosphorus from the diet, which are critical for bone formation and maintenance. It also plays roles in muscle function and immune system regulation, but its primary function is in the skeletal system.
917005
PhysiologyThe myenteric plexus, or Auerbach's plexus, is located between the longitudinal and circular muscle layers of the gut wall. Its primary function is to regulate the motility of the gastrointestinal tract. It does so by coordinating the contractions of the smooth muscles, which are responsible for peristalsis and the propulsion of food through the digestive system. The myenteric plexus works in conjunction with the submucosal plexus and can be influenced by both the sympathetic and parasympathetic nervous systems.
730597
PhysiologyThe primary function of the descending limb of the Loop of Henle is the reabsorption of water, which concentrates the tubular fluid as it descends.
363817
General MedicineHemophilia A is a congenital defect due to various abnormalities of the gene on the X chromosome that codes for factor VIII, leading to a hemorrhagic diathesis. Hageman trait is also congenital but does not directly cause a bleeding disorder.
709022
Oral MedicineAcetaminophen is primarily known for its analgesic and antipyretic (fever-reducing) effects. It is a common component in many over-the-counter pain relief medications.
604410
AnatomyThe nerve to masseter passes through the mandibular notch to enter the muscle on its medial surface
The nerve to the masseter muscle is the masseteric nerve, which is a branch
of the mandibular nerve (CN V3), the largest division of the trigeminal nerve
(cranial nerve V). The masseter muscle is one of the muscles of mastication that
lifts the lower jaw, contributing to the action of biting and chewing.
The masseteric nerve originates from the anterior division of the mandibular
nerve and typically passes:
1. Deep to the medial pterygoid muscle: The medial pterygoid muscle is located
in the infratemporal fossa, which is the space deep to the zygomatic arch and
medial to the temporomandibular joint (TMJ). The masseteric nerve runs in a deep
position relative to the medial pterygoid muscle as it travels towards the
masseter muscle. This muscle is involved in the side-to-side movement of the
jaw, known as lateral excursion.
2. Posterior to the temporomandibular joint: The TMJ is the articulation between
the mandible and the temporal bone of the skull. It is a synovial joint that
allows for the hinge movement of the jaw, such as opening and closing the mouth.
The masseteric nerve passes behind the TMJ to reach the masseter muscle. This
nerve does not actually cross the joint itself but runs in a position posterior
to it.
3. Superior to the zygomatic arch: The zygomatic arch is the bony structure that
extends from the zygomatic process of the temporal bone to the zygomatic bone of
the skull. It forms the prominence of the cheek. The masseteric nerve runs
superior to the zygomatic arch to reach the masseter muscle. The arch serves as
a landmark for the nerve's course, and the nerve typically does not pass through
the arch itself.
4. Through the mandibular notch: This statement is not entirely correct. The
masseteric nerve does not pass through the mandibular notch, which is a
depression on the medial surface of the ramus of the mandible, but rather it
passes above (superior to) the notch. The mandibular notch is the location where
the masseteric nerve and the other branches of the mandibular nerve leave the
infratemporal fossa and enter the submandibular space to innervate the muscles
of mastication, including the masseter. The nerve then runs along the lateral
surface of the lateral pterygoid plate and enters the deep surface of the
masseter muscle.
In summary, the masseteric nerve passes deep to the medial pterygoid muscle,
posterior to the TMJ, and superior to the zygomatic arch. It does not pass
through the mandibular notch; instead, it runs superior to it before reaching
the masseter muscle. The anatomical pathway of this nerve allows it to
effectively innervate the masseter muscle, which is crucial for the function of
the muscle in mastication.
919236
ProsthodonticsTitanium alloys are commonly used in dental implants due to their favorable properties, including biocompatibility and mechanical strength. The density of titanium alloys is relatively close to that of human alveolar bone, which helps in achieving a good integration (osseointegration) between the implant and the bone. Other materials listed, such as chromium-cobalt and stainless steel alloys, have different densities and are not as compatible with bone in terms of density and biological response. Bioglass, while biocompatible, is not typically used as a structural implant material in the same way as titanium.
290011
RadiologyIn an X-ray tube, the filament (cathode) is heated to produce electrons through a process called thermionic emission. This heating is accomplished by a step-down low voltage transformer, which reduces the high voltage from the power supply to a lower voltage suitable for heating the filament. The step-down transformer ensures that the filament receives the correct amount of current to achieve the necessary temperature for electron production.