The loss of blood volume is detected by cells in the kidneys and triggers thirst for both water and salt via the renin-angiotensin system. Renin-angiotensin system
Hypovolemia leads to activation of the renin angiotensin system (RAS) and is detected by cells in the kidney. When these cells detect decreased blood flow due to the low volume they secrete an enzyme called renin. Renin then enters the blood where it catalyzes a protein called angiotensinogen to angiotensin I. Angiotensin I is then almost immediately converted by an enzyme already present in the blood to the active form of the protein, angiotensin II. Angiotensin II then travels in the blood until it reaches the posterior pituitary gland and the adrenal cortex, where it causes a cascade effect of hormones that cause the kidneys to retain water and sodium, increasing blood pressure. It is also responsible for the initiation of drinking behavior and salt appetite via the subfornical organ. Others
Arterial baroreceptors sense a decreased arterial pressure, and signal to the central nervous system in the area postrema and nucleus tractus solitarii. Cardiopulmonary receptors sense a decreased blood volume, and signal to area postrema and nucleus tractus solitarii. Cellular dehydration and osmoreceptor stimulation
Osmometric thirst occurs when the solute concentration of the interstitial fluid increases. This increase draws water out of the cells, and they shrink in volume.
A torus palatinus (pl. tori palatini), or palatal torus (pl. palatal tori), is a bony protrusion on the palate. Palatal tori are usually present on the midline of the hard palate. Most palatal tori are less than 2 cm in diameter, but their size can change throughout life. Types
Sometimes, the tori are categorized by their appearance. Arising as a broad base and a smooth surface, flat tori are located on the midline of the palate and extend symmetrically to either side. Spindle tori have a ridge located at their midline. Nodular tori have multiple bony growths that each have their own base. Lobular tori have multiple bony growths with a common base. Cause
Although some research suggest palatal tori to be an autosomal dominant trait, it is generally believed that palatal tori are caused by several factors. They are more common in early adult life and can increase in size. In some older people, the size of the tori may decrease due to bone resorption. It is believed that tori of the lower jaw are the result of local stresses and not due solely to genetic influences. Treatment
Palatal tori are usually a clinical finding with no treatment necessary. It is possible for ulcers to form on the area of the tori due to repeated trauma. Also, the tori may complicate the fabrication of dentures. If removal of the tori is needed, surgery can be done to reduce the amount of bone present. Surgical removal
A maxillary torus is only removed in instances where it is problematic.