sinus

(noun)

A cavity within the cranium.

Related Terms

Examples of sinus in the following topics:

  • Carotid Sinus Syncope and Massage

    • The carotid sinus is a localized dilation of the internal carotid artery at its origin, the common carotid artery .
    • The carotid sinus often has atherosclerotic plaques.
    • Massage of the carotid sinus, or carotid sinus massage, is used to diagnose carotid sinus syncope.
    • The carotid sinus can also be oversensitive to carotid sinus massage.
    • Carotid sinus syncope sometimes accompanies convulsive seizures because of the intensity of the carotid sinus reflex when pressure builds in one or both carotid sinuses.

  • Arrhythmia

    • In normal electrical activity, each heart beat originates as an electrical impulse from a small area of tissue in the right atrium of the heart called the sinus node or sino-atrial node or SA node.
    • This may be caused by a slowed signal from the sinus node (sinus bradycardia), a pause in the normal activity of the sinus node (sinus arrest), or by blocking of the electrical impulse on its way from the atria to the ventricles (AV block or heart block).
    • Schematic diagram of normal sinus rhythm for a human heart as seen on ECG.

  • Sinusitis

    • In addition to the severity of disease, sinusitis can be classified by the sinus cavity that it affects.
    • Frontal: can cause pain or pressure in the frontal sinus cavity (located above eyes), or a headache.
    • Sinus infection can spread through veins or by direct extension to close structures.
    • Sinusitis may extend to the central nervous system where it may cause cavernous sinus thrombosis, retrograde meningitis, and epidural, subdural, and brain abscesses.

  • Veins of the Head and Neck

    • Formed at the base of the brain from the inferior petrosal sinus and the sigmoid the sinus the internal jugular vein runs down the side of the neck adjacent to the internal carotid artery.

  • Proprioceptor Regulation of Breathing

    • During stretch receptor activation, the inhibitory signal that travels through the vagus nerve is also sent to  the sinus-atrial node of the heart.
    • When this process is cyclical it is called a sinus arrhythmia, which is a generally normal physiological phenomenon in which there is short-term tachycardia during inspiration.
    • Sinus arryhthmias do not occur in everyone, and are more common in youth.
    • The sensitivity of the sinus-atrial node to the inflation reflex is lost over time, so sinus arryhthmias are less common in older people.

  • Lymph Transport

    • Lymph circulates to the lymph node via afferent lymphatic vessels and drains into the lymph node in the subcapsular sinus.
    • The lymph fluid drains into the node just beneath the capsule of the node into the various sinus spaces of the lymph node.
    • The different sinus spaces are loosely separated by walls, so lymph fluid flows around them throughout the lymph node.
    • The sinus space is filled with macrophages that act to engulf foreign particles and pathogens and filter the lymph.

  • Glossopharyngeal (IX) Nerve

    • It receives visceral sensory fibers from the carotid bodies, carotid sinus.
    • Visceral sensory (general visceral afferent) - carries visceral sensory information from the carotid sinus and body.

  • Development of the Urinary System

    • The urinary bladder develops from the upper end of the urogenital sinus, which is continuous with the allantois.
    • The lower ends of the metanephric ducts are incorporated into the wall of the urogenital sinus and form the trigone of the bladder.

  • Oculomotor (III) Nerve

    • Sympathetic postganglionic fibers also join the nerve from the plexus on the internal carotid artery in the wall of the cavernous sinus and are distributed through the nerve, e.g., to the smooth muscle of levator palpebrae superioris.
    • It runs along the lateral wall of the cavernous sinus, above the other orbital nerves, receiving in its course one or two filaments from the cavernous plexus of the sympathetic nervous system, and a communicating branch from the ophthalmic division of the trigeminal nerve.

  • Abducens (VI) Nerve

    • At the tip of the petrous temporal bone, it makes a sharp turn forward to enter the cavernous sinus.
    • In the cavernous sinus it runs alongside the internal carotid artery.