The trapezoid ligament is one of two components forming the coracoclavicular (CC) ligament. The conoid ligament is the other component.
The trapezoid ligament is a broad quadrilateral ligament that is quite thin. Its positioned almost horizontally. It is the anterolateral part of...
The triangle of Guillain and Mollaret, also known as the dentatorubro-olivary pathway, has three corners 1:
inferior olivary nucleus
contralateral dentate nucleus
Rubro-olivary fibers descend from the parvocellular division of each red nucleus along the central tegmental tracts t...
The triangle of safety is an anatomical region in the axilla that forms a guide as to the safe position for intercostal catheter (ICC) placement. With the arm abducted, the apex is the axilla, and the triangle is formed by the:
lateral border of the pectoralis major anteriorly
lateral border o...
The triangles of the neck are surgically focused divisions of the neck, first described from early dissection-based anatomical studies which predated cross-sectional anatomical description based on cross-sectional imaging (see deep spaces of the neck).
The neck can be divided into anterior and ...
The triangular fibrocartilage complex (TFCC) is a complex structure that is a major contributor to the stability of the wrist.
The TFCC is located on the ulnar aspect of the wrist joint between the ulna and the lunate and triquetrum of the proximal carpal row. It has an elongate...
The triangular ligaments grouped with the ulnar collateral ligament and meniscal homologue, comprise the ulnar-sided components of the triangular fibrocartilage complex (TFCC). The triangular ligament attaches triangular fibrocartilage to the ulnar tip and fovea.
The triangular ligament is comp...
The triangular space may refer to:
medial (upper) triangular space in the axilla
lateral (lower) triangular space in the axilla
Triangular space of cruciate ligaments (TSC) is defined as the potential extrasynovial space between anterior and posterior cruciate ligaments of the knee joint.
anteriorly: anterior cruciate ligament
posteriorly: posterior cruciate ligament
inferiorly: tibial plate...
A useful mnemonic to remember the tributaries of the inferior vena cava is:
I Like To Rise So High
I: common iliac veins
L: lumbar veins
T: right testicular (gonadal) vein
R: renal veins
S: suprarenal veins
H: hepatic veins
The triceps brachii muscle, often referred to simply as the triceps, is a three-headed muscle in the posterior compartment of the arm.
long head: infraglenoid tubercle of the scapula
medial head: posterior humerus inferior to the radial groove, both intermuscular septa
The triceps coxae is the tricipital (three headed) collection of 3 muscles in the posterior hip which act together on the hip, primarily to laterally rotate the extended thigh. It comprises (in order from superior to inferior) the superior gemellus, obturator internus and inferior gemellus muscl...
Triceps surae is another term used for the calf muscles, more specifically two of the three muscles of the superficial posterior compartment of the leg:
medial and lateral heads of the gastrocnemius muscle
The group of muscles are innervated by the tibial nerve and form the Achi...
The tricuspid valve (TV) is one of the four cardiac valves. It is one of the two atrioventricular valves (AVs) and allows blood to flow from the right atrium to the right ventricle. It opens during diastole and closes during systole. The valve has anterior, posterior and septal leaflets (cusps),...
The trigeminal ganglion, also known as the Gasser, Gasserian or semilunar ganglion, is the large crescent-shaped sensoryganglion of the trigeminal nerve located in the trigeminal cave (Meckel cave) surrounded by cerebrospinal fluid.
The ganglion contains the cell bodies of the sensory root of t...
The trigeminal nerve is the fifth cranial nerve and its primary role is relaying sensory information from the face and head, although it does provide motor control to the muscles of mastication. It is both large and complicated and has multiple brainstem nuclei (sensory and motor) as well as man...
A mnemonic for remembering the names of the skull foramina that the division of the trigeminal nerve (CN V) pass through is:
Standing Room Only
standing: superior orbital fissure (ophthalmic division of trigeminal nerve)
room: foramen rotundum (maxillary division of trigeminal nerve...
The trigone of the lateral ventricle is an area of the lateral ventricle at the confluence of the occipital and temporal horns. It refers either to the three-dimensional space at the transition between the body of the lateral ventricle and the occipital and temporal horns, in which case it is al...
The triquetrum (also known as os triquetrum or triangular bone) is one of the carpal bones and forms part of the proximal carpal row.
The triquetrum is wedge-shaped carpal bone located between the lunate and the pisiform. It has an oval facet for articulation with the ...
The triradiate cartilage is the Y- shaped epiphyseal plate that occurs at the junction where the ischium, ilium, and pubis meet in the skeletally immature skeleton.
The vertical component of the "Y" is the meeting of the ischium and pubic bone. The anterior arm is the junction of the ilium an...
The triscaphe joint is the shared joint between the scaphoid, trapezium and trapezoid bones in the wrist. This joint is also referred to by its much longer name, the scaphotrapeziotrapezoid (STT) joint.
This joint may be fused as an alternative to scapholunate fusion in treat...
Trochlea (sing., pl. trochleae) is a general term that refers to an anatomic structure that resembles the grooved part of a pulley system:
Trochlea have been described in:
trochlea of the superior oblique muscle
trochlear nerve (CN IV)
trochlea of ...
The trochlear nerve is the fourth cranial nerve and is the motor nerve of the superior oblique muscle of the eye. It can be divided into four parts:
nucleus and an intraparenchymal portion
cavernous sinus portion
Nucleus and intraparenchy...
The true vocal cords are the thickened, free edge of the cricovocal membrane, the cricovocal ligament, lined by mucous membrane 1. Together they form part of the glottis, the V-shaped aperture through which air passes. Their primary role is in phonation where vibration of the adducted vocal cord...
Tuber cinereum is a hollow eminence of gray matter. It is a part of the hypothalamus.
It is located between mammillary bodies and optic chiasm. Devoid of the blood brain barrier, it normally enhances after contrast administration.
It is continuous:
laterally: with an...
The tuberculum sellae is the ridged process of the sphenoid bone which forms the anterior wall of the sella turcica.
The tuberculum sellae forms the anterior wall of the sella turcica, which houses the pituitary gland. It is an elongated ridge located immediately poste...
The tunica albuginea (TA) forms the fibrous covering of the testis and is itself covered by the serous layer, the tunica vaginalis. The covering is total, except for at the point of attachment of the epididymis, and a small defect posteriorly where the spermatic cord vessels enter and leave the ...
Tunica is a word used in anatomy to refer to a type of covering.
tunica adventitia (also known as tunica externa)
tunica albuginea (clitoris)
tunica albuginea (ovary)
tunica albuginea (penis)
tunica albuginea (testis)
The tunica vaginalis (TV) represents the investing serosal covering of the testis. It forms as the embryological testis descends and passes out through the superficial inguinal ring carrying its abdominal peritoneal covering with it.
The tunica vaginalis is said to consist of two layers, the pa...
The twelfth rib is an atypical rib. It is the shortest rib, and one of two floating ribs.
The 12th rib has a single facet on its head for articulation with the T12 vertebra. It has a short neck and no tubercle. It also lacks a costal groove and angle. internal surface ...
The tympanic annulus is the thickened edge of the pars tensa of the tympanic membrane, anchoring it in the tympanic sulcus 3.
The tympanic annulus is formed by a fibrocartilaginous thickening of the edge of the pars tensa and has a horseshoe-shaped configuration. It is deficient ...
The tympanic membrane is a thin membrane that separates the external ear from the middle ear. It acts to transmit sound waves from air in the external auditory canal (EAC) to the ossicles of the middle ear.
The tympanic membrane is shaped like a flat cone pointing into the middle...
The tympanic part of the temporal bone is situated inferiorly to the squamous part and anteriorly to the mastoid part.
The tympanic part surrounds the external auditory meatus, forming the anterior wall, floor and some of the posterior wall of the bony external acoustic meatus. The lateral bord...
The tympanomastoid fissure is one of the intrinsic fissures of the temporal bone, located parallel and posterior to the bony external auditory canal, dividing the tympanic part of the temporal bone and mastoid process. Its radiological significance is as a fracture mimic (pseudofracture) 1. Its ...
The tympanosquamous fissure separates the tympanic part of the temporal bone from the squamous part. It is parallel and anterior to the bony external auditory canal and divides medially into the petrotympanic fissure and petrosquamous fissure.
Of the seven cervical vertebrae, C3 through C6 have typical anatomy, while C7 looks very similar. C1 (atlas) and C2 (axis) have very distinct anatomical features. For a basic anatomic description of the structure a generic vertebra, see vertebrae.
small, oval-shaped vertebral bod...
Typical ribs are those numbered 2 to 10 with ribs 1, 11 and 12 considered atypical.
A typical rib is long and flat. They contain a:
Ribs have a rounded, smooth superior border. The inferior border is thin and sharp.
Given the twelve thoracic vertebrae are largely similar, most are considered typical thoracic vertebrae with the exceptions T1 and T9 to T12. For a basic anatomic description of the structure of typical vertebrae, see vertebrae.
Relative to cervical and lumbar vertebrae, thoracic...
The ulna (plural: ulnae) is one of the two long bones of the forearm, located medially in the supinated anatomic position. It has a larger proximal end and tapers to a smaller distal end (opposite to the radius).
Prominent features of the ulna include:
The ulnar artery is a terminal branch of the brachial artery, arising at the proximal aspect of the forearm. Along with the radial artery, it is one of the main arteries of the forearm.
origin: terminal branch of the brachial artery
location: inferior aspect of the cubital fossa
The ulnar nerve is one of the terminal branches of the brachial plexus and has motor and sensory supply to the forearm and hand.
The ulnar nerve originates as a terminal branch of the medial cord of the brachial plexus with nerve root fibers from C8-T1.
The ulnar vein is one of the two major deep veins of the forearm, along with the radial vein. As is usual in the upper and lower limbs, there are often two veins (venae comitantes) that run on either side of the ulnar artery and anastomose freely with each other.
It forms in the hand from the d...
The ulnomeniscal homologue (UMH) is an obliquely oriented, fibrocartilaginous structure, that forms part of the ulnar collateral ligament complex (ULC) of the wrist.
The UMH is located between the ulnar styloid process and the triquetrum. It adheres to the ulnar joint capsule and...
The umbilical artery gives rise to both a nonfunctional remnant of the fetal circulation and an active vessel giving supply to the bladder. In the adult, the obliterated area of the vessel is identifiable as the medial umbilical ligament and the patent segment is the superior vesical artery.
The umbilical cord is a fetal organ that connects the placenta to the developing fetus and is a vital passage for nutrients, oxygen and waste products to and from the fetus.
The umbilical cord inserts into the center of the placental bulk and into the fetus at the umbilicus. Variations in inse...
The umbilical folds are a series of 5 folds of parietal peritoneum on the deep surface of the anterior abdominal wall and consist of:
a single midline median umbilical fold,
bilateral medial umbilical folds, and
bilateral lateral umbilical folds
The umbilical vein is the conduit for blood returning from the placenta to the fetus until it involutes soon after birth.
The umbilical vein arises from multiple tributaries within the placenta and enters the umbilical cord, along with the (usually) paired umbilical arteries. Once it enters the...
The umbilicus is the fibrous remnant of the foetal attachment of the umbilical cord after birth. All layers of the anterior abdominal wall fuse at the umbilical ring, a small round defect in the linea alba located just inferior to the midpoint between the xiphoid process of the sternum and the p...
The uncinate fasciculus is a white matter tract that connects the uncus (Brodmann area 35), the anterior temporal areas (temporal pole; Brodmann area 38), the amygdala and the hippocampal gyrus (Brodmann areas 36 and 30) with areas of the frontal lobe (polar and orbital cortex); runs - forming a...
The uncinate process of the ethmoid bone is a thin hook-like osseous structure of the wall of the lateral nasal cavity.
Together with the ethmoid bulla, it forms the boundaries of the hiatus semilunaris and ethmoid infundibulum.
The course of the free edge of the uncinate proces...
The uncinate process of the cervical spine is a hook-shaped process found bilaterally on the superolateral margin of the cervical vertebral bodies of C3-C7.
The uncinate processes are more anteriorly positioned in the upper cervical spine and more posteriorly location in the lower cervical spin...
Uncovertebral joints, also called Luschka’s joints, are seen bilaterally between adjacent cervical vertebrae, identified by the cat ear shaped uncinate processes of the C3-7 vertebrae (C1 and C2 have no uncinate processes).
The articulation forms between the uncina...
The uncus (plural: unci) is the innermost part of the anterior parahippocampal gyrus, part of the mesial temporal lobe.
The uncus is the most anterior portion of the medial parahippocampal gyrus. It belongs to the limbic system. Housing the primary olfactory cortex, it is part o...
Unfused spinous process, which is really failure of fusion of the neural arch, is a relatively common anatomical variant and is part of the spectrum of spina bifida occulta.
This should be differentiated from accessory ossicles of the spinous process, which appear after non-fusion of the secon...
Fusion of sternal body segments is usually complete by 25 years of age. But non-fusion of sternal body segments can be seen in older age group.
A unicornuate uterus or unicornis unicollis is a type of Müllerian duct anomaly (class II) characterized by a banana-shaped uterus usually draining into a single Fallopian tube.
This type can account for ~10% (range 6-13%) of uterine anomalies and infertility is seen in ~12.5% (ra...
Upper limb anatomy encompasses the anatomy of the shoulder, arm, elbow, forearm, wrist and hand.
This anatomy section promotes the use of the Terminologia Anatomica, the international standard of anatomical nomenclature.
The upper subscapular nerve, also known as the short or superior subscapular nerve, arises from the posterior cord of the brachial plexus and supplies the subscapularis muscle.
The upper subscapular nerve branches from the posterior cord of the brachial plexus with fibers...
The upper T sign is one of the features useful in identifying the central sulcus of the cerebral cortex on cross-sectional imaging.
It relies on identifying the superior frontal sulcus which intersects the precentral sulcus in a "T" junction, thus defining the precentral gyrus. The central sulc...
The urachus is the fibrous vestigial remnant of the fetal allantois.
The lumen of the urachus usually obliterates after birth and it becomes the median umbilical ligament, a midline linear fibrous fold of parietal peritoneum, extending from the apex of the bladder to the umbilicus. It is locate...
The ureter is a paired fibromuscular tube that conveys urine from the kidneys in the abdomen to the bladder in the pelvis.
The ureter is 25-30 cm long and has three parts:
abdominal ureter: from the renal pelvis to the pelvic brim
pelvic ureter: from the pelvic brim to the bla...
Ureteral duplication is the most common congenital abnormality associated with the urinary tract, and occurs in ~1% of the population.
Duplication can occur unilaterally or bilaterally, and may be partial or complete:
partially duplicated ureters fuse into a single ureter proxim...
The ureteric bud (also known as the metanephrogenic diverticulum) is a protrusion of the mesonephric duct that appears during the embryological development of urogenital organs. It will eventually form the urinary collecting system (i.e. collecting tubes, calyces, renal pelvis, ureter) of the ki...
The urethra is the terminal segment of the genitourinary system. Because of vastly different anatomy between the sexes, male and female urethras are discussed separately:
The urinary bladder (more commonly just called the bladder) is a distal part of the urinary tract and is an extraperitoneal structure located in the true pelvis. Its primary function is as a reservoir for urine.
The bladder has a triangular shape with a posterior base, an anteri...
The urinary system consists of the kidneys, ureter, bladder and urethra. With the exception of the urethra, this is the same in both males and females. It spans the abdomen and pelvis, from the upper abdomen to the extreme pelvis, being inextricably linked with the genital system.
The urinary ...
The urogenital triangle forms the anterior half of the diamond-shaped perineum. The triangle's corners are defined by the pubis symphysis anteriorly and the ischial tuberosities anterolaterally. The anterolateral borders are the ischiopubic rami and the posterior border is the transverse perinea...
The U sign denotes the characteristic U-shaped appearance of the subcentral gyrus which surrounds the inferolateral end of the central sulcus and abuts the lateral (Sylvian) fissure. It has been found, at least in one study, to be the most reliable anatomical feature to identify the central sulc...
Uterine agenesis is the extreme of Mullerian duct anomalies (Class I) where there is a complete absence of uterine tissue above the vagina.
The uterine agenesis-hypoplasia spectrum accounts for ~10-15% of all Müllerian duct anomalies.
The uterine artery is seen bilaterally and is a branch of the anterior division of the internal iliac artery.
It runs medially in the pelvis, within the base of the broad ligament, to the outer surface of the uterus. From lateral to medial it has a descending, transverse ...
Uterine duplication anomalies are a group of Müllerian duct anomalies where fusion of the Müllerian duct associated structures fail to some degree:
uterus didelphys: class III
bicornuate uterus: class IV (second commonest duplication anomaly)
septate uterus: class V (commonest duplication ano...
The uterine tube, also known as the Fallopian tube or less commonly the oviduct, is a paired hollow tube that bridges between each ovary and the uterus and functions to convey the mature ovum from the former to the latter. If conception occurs, it normally does so within the tube. It can be affe...
The uterine venous plexus is a network of veins surrounding the uterus and has extensive anastomoses with the vaginal venous plexus inferiorly and ovarian venous plexuses laterally.
The uterine venous plexus lies along the lateral aspects and superior angles of the uterus within ...
The paired uterosacral ligaments are one of the supporting structures of the uterus. Uterosacral ligaments are not infrequently affected in cases of deep infiltrating endometriosis.
The paired uterosacral ligaments are extraperitoneal structures which extend posteriorly from the ...
The uterus is a hollow, thick-walled, muscular organ of the female reproductive tract that lies in the lesser pelvis.
The uterus has an inverted pear shape. In the adult, it measures about 7.5 cm in length, 5 cm wide at its upper part, and nearly 2.5 cm in thickness. It weighs ...
The utricle may refer to:
utricle of the inner ear
utricle of the prostatic urethra
The utricle is a small membranous sac (part of the membranous labyrinth) and paired with the saccule lies within the vestibule of the inner ear. It has an important role in orientation and static balance, particularly in horizontal tilt.
The vestibule is located within the bony l...
The uvea (plural: uveas), also called the uveal layer or vascular tunic, is the middle of the three layers that make up the eye. It is the pigmented layer and its main function is of nutrition and gas exchange. It sits between the retina (innermost layer) and sclera.
It is traditionally split ...
The vagina is a midline fibromuscular tubular organ positioned in the female perineum extending superiorly from the vulva, to the cervix and uterus in the pelvis.
The vagina is 8-10 cm in length, extending posterosuperior from the vestibule through the urogenital diaphragm to th...
The vaginal artery is a branch of the anterior division of the internal iliac artery, and should not to be mistaken with the vaginal branch of the uterine artery. It is often considered to be a homolog of the inferior vesical artery, which is present only in males.
origin: anterior div...
The vaginal opening, is also known as the introitus (plural: introituses), vaginal orifice, or ostium vaginae (plural: ostia vaginarum) (TA) .
The entrance to the vagina lies in the vestibule of the vulva in the median plane. It has an anteroposterior orientation and is partially...
The vagus nerve is the tenth (X) cranial nerve and provides the bulk of the parasympathetic input to the gastrointestinal system and to the heart. It is a complex mixed sensory, motor and parasympathetic nerve.
The vagus nerve arises as multiple rootlets at ...
The epiglottic valleculae are paired depressions in the oropharynx located anterior to the epiglottis and posterior to the base of tongue. They are located between the lateral glossoepiglottic folds and the median glossoepiglottic fold.
Vallecula is Latin for "small valley", a combi...
The valveless veins are veins that lack venous valves. Most veins contain valves (known as the valvula venosa in the TA) to prevent backflow, i.e. ensuring that blood flow is always towards the heart 1.
Recent evidence shows that veins that were previously thought to be valveless, are now known...
The valvulae conniventes, also known as Kerckring folds/valves, plicae circulares or just small bowel folds, are the mucosal folds of the small intestine, starting from the second part of the duodenum, they are large and thick at the jejunum and considerably decrease in size distally in the ileu...
Variant anatomy of the aortic arch occurs when there is failure of normal aortic development. It results in a number of heterogenous anomalies of the aorta and its branch vessels.
Normally, the aorta ascends in the superior mediastinum to the level of the sternal notch before arc...
Variation in hepatic arterial anatomy is seen in 40-45% of people. Classic branching of the common hepatic artery from the celiac artery, and the proper hepatic artery into right and left hepatic arteries to supply the entire liver, is seen in 55-60% of the population.
There can be several variations in placental morphology. These include:
single lobed discoid placenta (single disc): most common scenario
bilobed placenta: two near equal size lobes
succenturiate lobe(s): one of more smaller accessory lobes
circumvallate placenta: rolled placental edges with...
Vascular anatomical variants are common:
SVC and IVC - caval variants
intracranial arteries - variants
The vastus intermedius muscle is one of the four quadriceps muscles in the anterior compartment of the thigh. The others are the vastus medialis, the vastus lateralis, and the rectus femoris.
origin: upper two-thirds of the anterior and lateral surfaces of the femur
The vastus lateralis is largest of the four quadriceps muscles in the anterior compartment of the thigh. The others are the rectus femoris, the vastus intermedius, and the vastus medialis.
lateral part of intertrochanteric line
margin of greater trochanter
The vastus medialis muscle is one of the four quadriceps muscles in the anterior compartment of the thigh. The others are the rectus femoris, the vastus intermedius, and the vastus lateralis.
medial part of intertrochanteric line
medial lip of the linea ...
The vein of Galen, also known as the great cerebral vein or great vein of Galen, is a short trunk formed by the union of the two internal cerebral veins and basal veins of Rosenthal. It lies in the quadrigeminal cistern. It curves backward and upward around the posterior border of the splenium o...
The vein of Labbé, also known as inferior anastomotic vein, is part of the superficial venous system of the brain.
The vein of Labbé is the largest channel that crosses the temporal lobe between the Sylvian fissure and the transverse sinus and connects the superficial middle cerebral vein to t...