coccygeal sinus

sinus /si·nus/ (si´nus) pl. si´nus, sinuses   [L.]

1. a recess, cavity, or channel, as (a) one in bone or (b) a dilated channel for venous blood.

2. an abnormal channel or fistula permitting escape of pus.si´nusal

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air sinus  an air-containing space within a bone.

anal sinuses  furrows, with pouchlike openings at the distal end, separating the rectal columns.

aortic sinus  a dilatation between the aortic wall and each of the semilunar cusps of the aortic valve; from two of these sinuses the coronary arteries originate.

branchial sinus  an abnormal cavity or space opening externally on the inferior third of the neck; usually a result of persistence of the second pharyngeal groove and cervical sinus.

carotid sinus  a dilatation of the proximal portion of the internal carotid or distal portion of the common carotid artery, containing in its wall pressoreceptors which are stimulated by changes in blood pressure.

Carotid sinus (sinus caroticus) and carotid arteries in a deep dissection of the right side of the neck.

cavernous sinus  either of two irregularly shaped sinuses of the dura mater, located at either side of the body of the sphenoid bone and communicating across the midline; it contains the internal carotid artery and abducent nerve.

cervical sinus  a temporary depression caudal to the second pharyngeal arch, containing the succeeding pharyngeal arches; it is overgrown by the second pharyngeal arch and closes off as the cervical vesicle.

circular sinus  the venous channel encircling the hypophysis, formed by the two cavernous sinuses and the anterior and posterior intercavernous sinuses.

coccygeal sinus  a sinus or fistula just over or close to the tip of the coccyx.

coronary sinus  the terminal portion of the great cardiac vein, lying in the coronary sulcus between the left atrium and ventricle, and emptying into the right atrium.

cortical sinuses  lymph sinuses in the cortex of a lymph node, which arise from the marginal sinuses and continue into the medullary sinuses.

dermal sinus  a congenital sinus tract extending from the surface of the body, between the bodies of two adjacent lumbar vertebrae, to the spinal canal.

dural sinuses  large venous channels forming an anastomosing system between the layers of the dura mater, draining the cerebral veins and some diploic and meningeal veins into the veins of the neck.

sinus of epididymis  a long, slitlike serous pocket between the upper part of the testis and the overlying epididymis.

ethmoid sinuses , ethmoidal sinuses see under cell.

frontal sinus  one of the paired paranasal sinuses in the frontal bone, each communicating with the middle meatus of the ipsilateral nasal cavity.

intercavernous sinuses  two sinuses of the dura mater connecting the two cavernous sinuses, one passing anterior and the other posterior to the infundibulum of the hypophysis.

lacteal sinuses , lactiferous sinuses enlargements of the lactiferous ducts just before they open on the mammary papilla.

lymphatic sinuses  irregular, tortuous spaces within lymphoid tissue (nodes) through which lymph passes, to enter efferent lymphatic vessels.

marginal sinuses 

1. see under lake.

2. bowl-shaped lymph sinuses separating the capsule from the cortical parenchyma, and from which lymph flows into the cortical sinuses.

maxillary sinus  one of the paired paranasal sinuses in the body of the maxilla on either side, and opening into the middle meatus of the ipsilateral nasal cavity.

medullary sinuses  lymph sinuses in the medulla of a lymph node, which divide the lymphoid tissue into a number of medullary cords.

occipital sinus  one of the sinuses of the dura mater, passing upward along the midline of the cerebellum.

oral sinus  stomodeum.

paranasal sinuses  mucosa-lined air cavities in bones of the skull, communicating with the nasal cavity and including ethmoidal, frontal, maxillary, and sphenoidal sinuses.

Paranasal sinuses (sinus paranasales).

petrosal sinus  either of two sinuses of the dura mater, arising from the cavernous sinus and draining into the internal jugular vein (inferior petrosal s.) or into the transverse sinus (superior petrosal s.).

pilonidal sinus  a suppurating sinus containing hair, occurring chiefly in the coccygeal region.

prostatic sinus  the posterolateral recess between the seminal colliculus and the wall of the urethra.

sinus of pulmonary trunk  a slight dilatation between the wall of the pulmonary trunk and each of the semilunar cusps of the pulmonary trunk valve.

renal sinus  a recess in the substance of the kidney, occupied by the renal pelvis, calices, vessels, nerves, and fat.

sagittal sinus, inferior  a small venous sinus of the dura mater, opening into the straight sinus.

sagittal sinus, superior  a venous sinus of the dura mater which ends in the confluence of sinuses.

sigmoid sinus  a venous sinus of the dura mater on either side, continuous with the transverse sinus and draining into the internal jugular vein of the same side.

sphenoid sinus , sphenoidal sinus one of the paired paranasal sinuses in the body of the sphenoid bone and opening into the highest meatus of the ipsilateral nasal cavity.

sphenoparietal sinus  either of two sinuses of the dura mater, draining into the anterior part of the cavernous sinus.

sinus of spleen  a dilated venous sinus in the substance of the spleen.

straight sinus  one of the sinuses of the dura mater formed by junction of the great cerebral vein and inferior sagittal sinus, commonly ending in the confluence of the sinuses.

tarsal sinus  a space between the calcaneus and talus.

tentorial sinus  straight s.

terminal sinus  a vein that encircles the vascular area in the blastoderm.

transverse sinus 

1. either of two large sinuses of the dura mater.

2. a passage behind the aorta and pulmonary trunk and in front of the atria.

tympanic sinus  a deep recess in the posterior part of the tympanic cavity.

urogenital sinus  an elongated sac formed by division of the cloaca in the early embryo, forming most of the bladder, the female vestibule, urethra, and vagina, and most of the male urethra.

uterine sinuses  venous channels in the wall of the uterus in pregnancy.

sinus of venae cavae  the portion of the right atrium into which the inferior and the superior venae cavae open.

sinus veno´sus 

1. the common venous receptacle in the embryonic midheart, attached to the posterior wall of the primordial atrium.

2. venous s. (1).

3. s. of venae cavae.

venous sinus 

1. a large vein or channel for the circulation of venous blood.

2. s. venosus (1).

venous sinuses of dura mater  large channels for venous blood forming an anastomosing system between the layers of the dura mater of the brain, receiving blood from the brain and draining into the veins of the scalp or deep veins at the base of the skull.

venous sinus of sclera  a branching, circumferential vessel in the internal scleral sulcus, a major component of the drainage pathway for aqueous humor.

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coccygeal sinus

n.

A fistula opening in the region of the coccyx due to incomplete closure of the caudal end of the neural tube.

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Patient discussion about coccygeal sinus.

Q. What is pilonidal cyst?

A. A pilonidal cyst, also referred as sacrococcygeal fistula, is a blanket term for any type of skin infection near the tailbone. The condition is also referred as pilonidal sinus disease. It is usually painful. http://en.wikipedia.org/wiki/Pilonidal_cyst
This is a good site also:
http://www.pilonidal.org/whatitis.htm
Hope this helps.