Final answer:
Temporomandibular joint disorder (TMJD or TMJ syndrome) is the condition where an individual cannot close their mouth due to dislocation at the joint, which can be caused by various factors, and has treatments like pharmacologic agents and bite guards. Tetanus leads to muscle spasms and lockjaw and is preventable by vaccination. Myasthenia gravis causes muscle weakness due to an autoimmune response blocking acetylcholine receptors and requires medical treatment.
Step-by-step explanation:
The condition described in the question where an individual is unable to close their mouth due to the mandibular condyle moving beyond the articular tubercle as a result of opening the mouth too wide or after a blow to the jaw is known as Temporomandibular joint disorder (TMJD or TMJ syndrome). TMJ disorder is a painful condition that may arise from multiple factors such as arthritis, cartilage wear, muscle fatigue, teeth grinding, or jaw injury. It can cause symptoms like headache, difficulty in chewing, and even the inability to move the jaw (lockjaw). Treatments for TMJ disorder often include pharmacologic agents for pain and other therapies like bite guards.
Tetanus is a serious bacterial infection characterized by muscle spasms, often starting in the jaw, which is why it's also known as lockjaw. It is caused by a toxin that blocks neurotransmitters responsible for muscle relaxation, leading to stiff muscle spasms sufficient to cause bone fractures or asphyxiation if the respiratory muscles are involved. Tetanus can be prevented by DTaP vaccine and is treated in a medical setting.
Myasthenia gravis is an autoimmune disorder where antibodies block acetylcholine receptors at the neuromuscular junction, leading to muscle weakness and fatigue, often starting with muscles around the eyes. If the respiratory muscles are affected, it can result in a myasthenic crisis needing emergency care. Various treatments including medications to counter the autoimmune response are available.