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having a nidus of hairs.
pilonidal cyst (pilonidal sinus) a hair-containing sacrococcygeal dermoid cyst or sinus, often opening at a postanal dimple, believed to result from an infolding of skin in which hair continues to grow. These cysts cause no symptoms unless they become infected, which is likely because of their location. Pain and swelling, with the formation of an abscess, are the symptoms of infection. Treatment consists of surgical removal.
Patient Care. Postoperative care includes dressing changes and wound care to avoid contamination and promote healing. A lubricating laxative and an oil enema are usually given before the first bowel movement to avoid strain on the suture line. Patients are taught handwashing and toileting to prevent infection until the wound is completely healed.
1. a recess, cavity, or channel, such as one in bone or a dilated channel for venous blood.
2. an abnormal channel or fistula, permitting escape of pus.
3. paranasal sinus.
anal s's furrows, with pouchlike recesses at the distal end, separating the rectal columns; called also anal crypts.
anterior s's (sinus anterio´res) the anterior air cells that together with the middle and posterior air cells form the ethmoidal sinus.
aortic s's pouchlike dilatations at the root of the aorta, one opposite each semilunar cusp of the aortic valve, from which the coronary arteries originate.
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 that are stimulated by changes in blood pressure. See also carotid sinus syndrome.
cavernous sinus an irregularly shaped venous channel between the layers of dura mater of the brain, one on either side of the body of the sphenoid bone and communicating across the midline. Several cranial nerves course through this sinus.
cerebral sinus one of the ventricles of the brain.
cervical sinus a temporary depression in the neck of the embryo containing the branchial arches.
circular sinus the venous channel encircling the pituitary gland, 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 dilated terminal portion of the great cardiac vein, receiving blood from other veins draining the heart muscle and emptying into the right atrium.
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.
ethmoid s's (ethmoidal s's) ethmoid cells.
frontal sinus one of the paired paranasal sinuses in the frontal bone, each communicating with the middle nasal meatus on the same side.
intercavernous s's channels connecting the two cavernous sinuses, one passing anterior and the other posterior to the stalk of the pituitary gland.
lymphatic s's irregular, tortuous spaces within lymphoid tissues through which lymph flows.
maxillary sinus one of the paired paranasal sinuses in the body of the maxilla on either side, opening into the middle nasal meatus on the same side.
occipital sinus a venous sinus between the layers of dura mater, passing upward along the midline of the cerebellum.
paranasal s's the eight cavities in the skull that are connected with the nasal cavity (see also Plates). They are arranged in four pairs, each of which has one member on the left and one on the right. The pairs are the maxillary sinuses in the maxillae; the frontal sinuses in the frontal bone; the sphenoid sinuses in the sphenoid bone behind the nasal cavity; and the ethmoid cells (ethmoid sinuses) in the ethmoid bone behind and below the frontal sinuses. The functions of the sinuses are not certain. They are believed to help the nose in circulating, warming, and moistening the air as it is inhaled, thereby lessening the shock of cold, dry air to the lungs. They also are thought to have a minor role as resonating chambers for the voice.
petrosal sinus, inferior a venous channel arising from the cavernous sinus and draining into the internal jugular vein.
petrosal sinus, superior one arising from the cavernous sinus and draining into the transverse sinus of the dura mater.
pilonidal sinus pilonidal cyst.
prostatic sinus the posterolateral recess between the seminal colliculus and the wall of the urethra, where the prostatic ductules empty into the urethra.
s's of pulmonary trunk spaces between the wall of the pulmonary trunk and cusps of the pulmonary valve at its opening from the right ventricle.
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 that ends in the confluence of sinuses.
sigmoid sinus a venous sinus of the dura mater on either side, continuous with the straight 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, opening into the superior nasal meatus on the same side.
sphenoparietal sinus one of the venous sinuses of the dura mater, emptying into the cavernous sinus.
s's of spleen dilated venous sinuses found in the splenic pulp; they are not lined by ordinary endothelial cells.
straight sinus a venous sinus of the dura mater formed by junction of the great cerebral vein and inferior sagittal sinus, and ending in the confluence of sinuses.
tarsal sinus a space between the calcaneus and talus.
tentorial sinus straight sinus.
transverse sinus of dura mater a large venous sinus on either side of the brain.
transverse sinus of pericardium a passage within the pericardial sac, behind the aorta and pulmonary trunk and in front of the left atrium and superior vena cava.
tympanic sinus a deep recess on the medial wall of the middle ear.
urogenital sinus an elongated sac that is formed by division of the cloaca in the early embryo, which ultimately forms most of the vestibule, urethra, and vagina in the female, and some of the urethra in the male.
uterine s's venous channels in the wall of the uterus in pregnancy.
uteroplacental s's blood spaces between the placenta and uterine sinuses.
sinus of venae cavae the posterior portion of the right atrium into which the inferior and the superior vena cava open; called also sinus venosus.
sinus veno´sus (venous sinus)
2. the common venous receptacle in the early embryo attached to the posterior wall of the primitive atrium.
venous s's 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 circular channel at the junction of the sclera and cornea, into which aqueous humor filters from the anterior chamber of the eye. Called also Schlemm's canal.
a fistula or pit in the sacral region, communicating with the exterior, containing hair which may act as a foreign body producing chronic inflammation.
Synonym(s): pilonidal fistula
Etymology: L, pilus + nidus + sinus, curve
a cavity or sinus containing hair, in a dermoid cyst or the deepest layers of the skin. In most instances the hair originates in another area and becomes lodged in the sinus.
pi·lo·ni·dal si·nus(pī'lō-nī'dăl sī'nŭs)
A fistula or pit in the sacral region, communicating with the exterior, containing loose, broken-off body hairs that may act as a foreign body producing chronic inflammation.
sinus(si'nus) plural.sinuses, sinus [L., sinus, curve, hollow]
1. A recess.
2. A cavity with a narrow opening.
3. An endothelia-lined, air-filled cavity within a bone. (When nonmedical people speak of 'sinuses', they are generally referring to this type of sinus, specifically, to the paranasal sinuses.)
4. An endothelia-lined channel for venous blood.
5. A channel leading to an abscess.
accessory nasal sinusParanasal sinus.
air sinusParanasal sinus.
Any of the saclike recesses on the inner lining of the anal canal between the anal columns.
Inside the aorta, the pouch behind each of the three leaflets of the aortic valve. The right and left coronary arteries each originate from an orifice in an aortic sinus, leaving one aortic sinus (the noncoronary sinus) as a blind pouch. Synonym: sinus of Valsalva
basilar sinusTransverse sinus (2).
The small dilation at the base of the internal carotid artery with baroreceptors in its wall. These receptors respond to changes in arterial blood pressure, and their signals are carried to the hindbrain by the glossopharyngeal nerve (CN IX).
sinus cavernosusCavernous sinus.
A 1 cm wide dural sinus extending 2 cm along the medial wall of the base of the middle cranial fossa. The cavernous sinus empties into (a) the transverse sinus via the superior petrosal sinus, (b) the internal jugular vein via the inferior petrosal sinus, (c) the pterygoid plexus via emissary veins, and (d) the facial vein via the superior ophthalmic vein. The right and left cavernous sinuses are interconnected by the anterior and posterior intercavernous sinuses. Tributaries of the cavernous sinus include the superior ophthalmic, superficial middle cerebral, and inferior cerebral veins and the sphenoparietal sinus.Synonym: sinus cavernosus
cerebral sinusDural sinus.
A set of four interconnected dural sinuses encircling the sella turcica and pituitary gland at the base of the brain. The four sinuses are the right and left cavernous sinuses and the anterior and posterior intercavernous sinuses.
A sinus in the midline of the gluteal cleft just over the coccyx.
confluence of the sinuses
The dilated posterior end of the superior sagittal sinus in the skull. This dilation joins one of the transverse sinuses (usually the right), which drains the blood from the superior sagittal sinus toward the internal jugular vein. The other transverse sinus and the occipital sinus also connect to the confluence of the sinuses.)
A large vein on the posterior surface of the heart; it runs in the atrioventricular groove between the left atrium and left ventricle. Most of the blood feeding the heart returns to the right atrium via the coronary sinus. Its direct tributaries include the small, middle, and great cardiac veins.
Any of the large veins between the two layers of the cranial dura mater.
cranial venous sinusSinus (3).
A congenital sinus tract connecting the surface of the body with the spinal canal.
An abnormal passageway leading from inside the body to the outside. This is usually due to an infectious process.
Any of several large endothelia-lined collecting channels into which veins of the brain and inner skull empty and which then empty into the internal jugular vein. These venous sinuses are found between the two layers (periosteal and meningeal) of the dura mater. Their walls have no muscle, and they have no valves to give direction to the blood flow. The venous sinuses in the skull include the superior sagittal, inferior sagittal, straight, transverse, and cavernous sinuses.Synonym: cerebral sinus; dural venous sinus
dural venous sinusDural sinus.
Any of the 3-18 paranasal sinuses on each side of the skull in and adjacent to the ethmoid bone. The ethmoid sinuses can be categorized as anterior, middle, or posterior, with each group usually draining into a different part of the nasal cavity. Ethmoid sinuses have very thin walls and are interconnected via openings in the septa between the sinuses.
Either of a pair of paranasal sinuses in the frontal bones just above the orbits. These sinuses lie adjacent to each other in the midline, but are usually completely separated by a bony septum. Each frontal sinus drains into the ipsilateral nasal cavity through an opening in the lateral wall along the middle nasal passageway (i.e., middle nasal meatus).
The sinus formed when hair is embedded in the skin and acts as a foreign body.
inferior longitudinal sinusInferior sagittal sinus.
inferior petrosal sinus
A dural sinus that drains the cavernous sinus posteriorly into the superior jugular bulb of the internal jugular vein.
inferior sagittal sinus
An unpaired midline dural sinus running along the lower, free margin of the falx cerebri (over the top of the corpus callosum). It drains blood from veins in the falx and from the medial surfaces of the hemispheres, and it empties, posteriorly, into the straight sinus.
The anterior and the posterior intercavernous sinuses interconnect the right and left cavernous sinuses at the base of the brain. All sinuses are valveless; thus, the cavernous and intercavernous sinuses form a circle -- the circular sinus -- that enwraps the sella turcica.
Immediately inside the tip of the nipple, the dilated end of any of the 15-20 lactiferous ducts, which convey milk from the mammary glands during lactation.
Either of two large venous sinuses in the inner side of the skull passing near the mastoid antrum and emptying into the jugular vein.
Endothelia-lined channels through which lymph flows inside lymph nodes. The walls of lymph sinuses are coated with T and B lymphocytes as well as phagocytic cells, all of which filter the passing lymph. Lymphocytes and macrophages move in and out of the lymph through the sinus walls.Synonym: lymph channel
1. Considered together, the many dilated veins or venous "lakes" that collect blood in the intervillous space of the placenta; the marginal sinus drains into the uterine veins.
2. A dural sinus along the inside of the rim of the foramen magnum; it drains into the vertebral venous plexus.
3. A blood-filled sinus in the marginal zone of the spleen. In the passage from the red pulp to the white pulp, some arterial blood flows along (and percolates through) the endothelia-lined walls of the marginal sinus before entering the arterial capillary beds of the white pulp.
An old term for the mastoid antrum.
Either of a pair of paranasal sinuses filling the bodies of the maxillary bones. The maxillary sinuses are large and pyramidal shaped, with average dimensions of 3.5 cm x 2.5 cm x 3.2 cm. The medial floor of the maxillary sinus is immediately above the roots of the first and second upper molars. Each maxillary sinus drains into the ipsilateral nasal cavity through an opening in the lateral wall of the hiatus semilunaris, under the middle nasal concha. Synonym: antrum of Highmore
A slender dural sinus running in the posterior, i.e., attached, margin of the falx cerebelli. It begins near the foramen magnum, and it ascends along the midline of the occipital bone. The occipital sinus empties into the confluence of the sinuses.
An air cavity in a facial bone, either the frontal, maxillary, sphenoid, or ethmoid bones; most paranasal sinuses occur in pairs. The paranasal sinuses are lined with ciliated epithelium that secretes mucus. The sinuses open into the lateral walls of the nasal cavities via small holes. Healthy paranasal sinuses are radiolucent. Synonym: accessory nasal sinus; air sinus; See: illustrationillustration
The oblique or the transverse pericardial sinus, which are spaces between the visceral and parietal layers of the serous pericardium. The oblique sinus runs along the posterior surface of the left atrium between the orifices of the right and the left pulmonary veins. The transverse sinus runs along the posterior surface of the base of the heart between the outflow vessels (the aorta and the pulmonary trunk) in front and the inflow vessels (the pulmonary veins) behind.
The superior or the inferior petrosal sinus.
pilonidal sinusPilonidal fistula.
Any of the spaces in the pleural sac along the lower and inferior portions of the lung that the lung does not occupy.
A lacuna in the prostatic part of the urethra. Synonym: sinus prostaticus
sinus prostaticusSinus pocularis.
Either of the pouches within the pulmonic trunk behind each of the three leaflets of the pulmonic valve.
sinus rectusStraight sinus.
The indentation on the medial side of each kidney into which the hilum leads; the renal sinus is largely filled by the renal pelvis.
The fourth cranial ventricle.
The superior or the inferior sagittal sinus.
The continuation of the transverse sinus downward along the wall of the posterior cranial fossa to the jugular canal; there, the sigmoid sinus becomes the superior jugular bulb, the origin of the internal jugular vein.
Either of a pair of paranasal sinuses in the sphenoid bone just above and behind the nasal cavity. The sphenoid sinuses are located adjacent to the optic chiasm, the pituitary gland, and the internal carotid arteries. Each sphenoid sinus drains through an opening in the sphenoethmoidal recess at the very top of the ipsilateral nasal cavity.
A venous sinus uniting the cavernous sinus and a meningeal vein.
sinus of spleen
A large-capacity venous channel in the spleen.
An unpaired midline dural sinus where the falx cerebri and the tentorium cerebelli meet. The straight sinus is the posterior continuation of the inferior sagittal sinus. The straight sinus empties into the transverse sinus contralateral to the one joined by the superior sagittal sinus; nonetheless, the straight sinus often communicates, if only through a small channel, with the confluence of the sinuses.Synonym: sinus rectus
superior petrosal sinus
A slender dural sinus that drains the cavernous sinus posteriorly into the transverse sinus.
superior sagittal sinus
A long unpaired midline channel through the superior margin of the falx cerebri. It begins in the front near the crista galli of the ethmoid bone, and it extends along the entire inner roof of the skull to the internal occipital protuberance in the back. Its posterior end, called the confluence of the sinuses, is dilated and usually joins the right transverse sinus; however, the other transverse sinus and the occipital sinus also communicate with the confluence of the sinuses. Tributaries of the superior sagittal sinus include ascending frontal cerebral veins, superior cerebral veins, diploic veins draining the skull bones, and a number of irregularly shaped venous lacunae. Numerous arachnoid granulations (sites of the return of water and filtrate from the cerebrospinal fluid) protrude into the superior sagittal sinus.
tarsal sinusSinus tarsi.
A space between the top of the calcaneus bone and the bottom of the tarsal bone.Synonym: tarsal sinus
tentorial sinusSee: sinus rectus
A vein encircling the vascular area of the blastoderm.
A dural sinus in the lateral edge of the tentorium cerebelli along each lateral upper border of the posterior cranial fossa. One transverse sinus (usually the right) is a continuation of the superior sagittal sinus; the other transverse sinus (typically the smaller of the two) is the continuation of the inferior sagittal sinus, although both transverse sinuses usually have a connection near their origin, in the region of the confluence of sinuses. The transverse sinuses run anteriorly and turn downward to become the sigmoid sinuses at the front edges of the tentorium cerebelli; at this point, the transverse sinuses are joined by the superior petrosal sinuses. Tributaries of the transverse sinuses include inferior cerebral, inferior cerebellar, and diploic veins.
A recess in the medial wall of the tympanic cavity beside the promontory and adjacent to the round window. The sinus tympani can be > 3 mm deep.
In the embryo, a space behind the urogenital membrane (a surface structure) and separated from the future rectum by the urorectal septum (an internal structure). The urachus and the mesonephric ducts, i.e., the Wolffian ducts, open into the urogenital sinus. The sinus will later give rise to major parts of the urinary bladder, urethra, vagina, and genitourinary tract glands.
Any of the venous channels in the walls of the uterus during pregnancy.
Any of the slanting venous channels from the placenta serving to convey the maternal blood from the intervillous lacunae back into the uterine veins.
sinus of ValsalvaAortic sinus.
sinus of venal canal
The portion of the right atrium of the heart posterior, and to the left of, the crista terminalis. The inferior and superior vena caval veins empty into it.
In the embryo, the portion of the developing heart tube that leads into the cavities destined to form the atria and ventricles. The major embryonic veins — umbilical, vitelline, and common cardinal — all lead into the sinus venosum. Later, the sinus venosum will become the posterior smooth wall of the right atrium, including the openings from the coronary sinus and the venae cava.
A valveless irregularly shaped venous channel lined by endothelial cells. Large venous sinuses include the coronary sinus of the heart and the dural sinuses inside the skull; small venous sinuses are found inside certain tissues, such as the spleen.
pilonidal sinusA depression or pit in the skin in the upper part of the cleft between the buttocks that often contains hairs. The origin is unclear but the condition is thought to be due to hairs burrowing into the skin as a result of the movement of the buttocks. Pilonidal sinuses can become infected and surgical opening and exposure may be necessary.
having a nidus of hairs.
see dermoid cyst.
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