The fifth ventricle has historically been used to refer to either the:
cavum septum pellucidum
The filum terminale is a filament of connective tissue that extends inferiorly from the apex of the conus medullaris.
The filum terminale is continuous with the pia mater and is described as having two sections:
filum terminale internum: upper three quarters of the filum; covere...
The first rib is the most superior of the twelve ribs. It is an atypical rib and is an important anatomical landmark and is one of the borders of the superior thoracic aperture.
Compared to a typical rib, the first rib is short and thick and it has a single articular f...
Fishtail pancreas (also known as pancreas bifidum or bifid tail of the pancreas) is a rare anatomical variant of the pancreas produced by a branching anomaly during its development. It is named as such due to the fishtail-like appearance of the pancreas.
It is a rare anatomical an...
The fissula ante fenestram (FAF), also known as the cochlear cleft, is a small connective tissue-filled cleft located where the tendon of the tensor tympani muscle turns laterally toward the malleus. It is situated immediately anterior to the oval window, and posterior to the cochleariform proce...
Flat bones are 1 of the 5 types of bones in the body and represent a group of bones (predominantly of the cranium) that have a relatively flat shape and form from intramembranous ossification.
Flexor carpi radialis (FCR) is a muscle found in the first layer of the anterior compartment of the forearm. It does not pass through the carpal tunnel, but rather by itself in a small separate tunnel between the superficial and deep layers of the flexor retinaculum along the scaphoid and trapez...
Flexor carpi ulnaris (FCU) is a muscle of the first layer of the anterior compartment of the forearm.
humeral head: medial epicondyle of the humerus
ulnar head: medial border of olecranon and posterior border of ulna
insertion: base of 5th metacarpal; hook of hamate, pisiform...
The flexor digiti minimi brevis muscle lies lateral to the abductor digiti minimi, within the hypothenar eminence.
origin: hook of the hamate and flexor retinaculum
insertion: proximal phalanx of 5th digit
action: flexes 5th finger at metacarpophalangeal joint
arterial supply: ulnar...
The flexor digiti minimi brevis muscle lies under the 5th metatarsal bone.
origin: base of metatarsal V and related sheath of fibularis longus tendon
insertion: lateral side of base of proximal phalanx of 5th toe
action: flexes 5th toe at metatarsophalangeal joint
arterial supply: l...
The flexor digitorum brevis muscle lies immediately superior to the plantar aponeurosis and inferior to the tendons of the flexor digitorum longus in the sole of the foot.
origin: medial process of calcaneal tuberosity and plantar aponeurosis
insertion: sides of plantar surface of mid...
The flexor digitorum longus (FDL) muscle is located on the tibial side of the leg within the deep posterior compartment of the leg. At its origin it is thin but as it descends, the muscle increases in size.
origin: medial side of posterior surface of the tibia
insertion: plantar surfa...
Flexor digitorum profundus (FDP) makes up the third layer of the anterior compartment of the forearm along with flexor pollicis longus. It passes through the carpal tunnel.
origin: proximal, anterior surface of ulna and adjacent interosseous membrane
insertion: volar surface of distal...
Flexor digitorum superficialis (FDS) is a muscle in the second (intermediate) layer of the anterior compartment of the forearm that splits into four tendons, passes under the flexor retinaculum and through the carpal tunnel, to insert into the middle phalanx of the 2nd-5th digits.
The flexor hallucis brevis muscle is one of the small muscles of the foot that is involved in flexion of the 1st toe. The hallux sesamoid bones are embedded within its tendon.
origin: plantar surface of cuboid
insertion: medial and lateral sesamoid bones of first metatarsal
The flexor hallucis longus (FHL) muscle is one of the muscles of the posterior deep compartment of the leg and along with flexor hallucis brevis, is involved in flexion of the great toe. Its tendon passes between the medial and lateral tubercles of the talus. It's tendon sheath may communicate w...
The flexor pollicis brevis muscle is a muscle of the thenar eminence and is distal to the abductor pollicis brevis.
origin: tubercle of the trapezium and flexor retinaculum
insertion: proximal phalanx of the thumb
action: flexes thumb at metacarpophalangeal joint
arterial supply: su...
Flexor pollicis longus (FPL) is one of the two muscles that make up the third layer of the anterior compartment of the forearm along with the flexor digitorum profundus. It is a deep muscle under abductor pollicis brevis muscle. It passes through the carpal tunnel.
The flexor retinaculum (also known as the transverse carpal ligament) is a rectangular-shaped fibrous band located at the ventral aspect of the wrist.
On the radial side, it attaches to the scaphoid tubercle and the ridge of the trapezium. On the ulnar side, it attaches to the pi...
Flexor retinaculum at the ankle is formed by reinforcement of the deep fascia of the leg by transverse collagen bundles and functions to prevent 'bowstringing' of tendons as they pass the tibiotalar joint. It forms the roof of the tarsal tunnel 1-2.
medial malleolus of the tibia
The floor of mouth is an oral cavity subsite and is a common location of oral cavity squamous cell carcinoma.
The floor of mouth is a U-shaped space which extends (and includes) from the oral cavity mucosa superiorly, and the mylohyoid muscle sling 2,3.
Focal fatty deposits/replacement in spinal bone marrow are well-defined focal fat islands within the bone marrow of spine or other parts of axial skeleton.
Common in older individuals, related to age but not to sex.
This process is a normal variant. Histologically, it ...
The foramen caecum represents a primitive tract between the anterior cranial fossa and the nasal space. It is located along the anterior cranial fossa, anterior to the cribriform plate of the ethmoid bone and posterior to the frontal bone, within the frontoethmoidal suture. It lies at a variable...
Foramen caecum can refer to a number of different anatomical structures:
foramen caecum (tongue)
foramen caecum (anterior cranial fossa)
The foramen lacerum is a triangular opening located in the middle cranial fossa anterior to the petrous apex, which forms its posterior border. Its anterior border is formed by the body of the sphenoid bone at the junction of greater wing and pterygoid process and medial border is formed by the ...
The foramen magnum is the largest foramen of the skull and is part of the occipital bone 1. It is oval in shape with a large antero-posterior diameter 2.
The foramen magnum is found in the most inferior part of the posterior cranial fossa 3. It is traversed by vital structures in...
The foramen of Langer is a defect in the deep pectoralis fascia. It is a defect at the level of the third intercostal space, through which the upper lateral portion of the breast extends into the axilla forming the axillary tail of Spence.
The foramen of Magendie (also called median aperture) is one of the foramina in the ventricular system and links the fourth ventricle and the cisterna magna. It is one of the three ways that cerebrospinal fluid (CSF) can leave the fourth ventricle and enter the subarachnoid space. The two other ...
The foramina of Morgagni, also known as the sternocostal triangles, are small defects in the posterior aspect of the anterior thoracic wall between the sternal and costal attachments of the diaphragm. The internal thoracic vessels descend through these foramina to become the superior epigastric ...
The foramen of Rouviere is a rarely seen space in the shoulder joint capsule between middle and inferior glenohumeral ligaments and it may communicate with the subcoracoid recess (inferior subscapularis recess). It should not be confused with an acquired defect.
The foramen of Weitbrecht is a small opening in the glenohumeral joint capsule between superior and middle glenohumeral ligaments and is seen communicating with the subtendinous bursa of the subscapularis muscle.
The foramen ovale (or ovalis) is the opening in the interatrial septum in the fetal heart that allows blood to bypass the right ventricle and non-ventilated lungs, shunted from the right atrium to the left atrium. Specifically it represents the opening between the upper and lower portions of the...
Foramen ovale can refer to a number of different anatomical structures:
foramen ovale (head)
foramen ovale (cardiac)
Foramen ovale is an oval shaped opening in the middle cranial fossa located at the posterior base of the greater wing of the sphenoid bone, lateral to the lingula. It transmits the mandibular division of the trigeminal nerve (CN Vc), accessory meningeal artery, emissary veins between the caverno...
The foramen rotundum is located in the middle cranial fossa, inferomedial to the superior orbital fissure at the base of greater wing of the sphenoid bone. Its medial border is formed by lateral wall of sphenoid sinus. It runs downwards and laterally in an oblique path and joins the middle crani...
The foramen singulare, also known as the singular foramen, is a small opening at the posteroinferior aspect of the fundus of the internal auditory canal (IAC) 2,3. It carries the singular or posterior ampullary nerve, a branch of the inferior vestibular nerve which carries afferent information f...
The foramen spinosum is located in the posteromedial part of greater wing of sphenoid bone posterolateral to foramen ovale which connects the middle cranial fossa with the infratemporal fossa. It transmits the middle meningeal artery, middle meningeal vein, and (usually) the nervus spinosus.
The foramen tympanicum (also known as foramen of Huschke) is an anatomical variation in the external acoustic canal (EAC), where a bony defect connects the EAC to the temporomandibular joint (TMJ).
Various studies have reported on the occurrence of a foramen tympanicum in the asym...
The foramen Vesalii, also know as the foramen of Vesalius, sphenoidal emissary foramen, foramen venosus or canaliculus sphenoidal, is a tiny variably present foramen in the greater wing of the sphenoid bone, located between the foramen ovale and scaphoid fossa. It transmits a sphenoidal emissary...
The forceps major, also known as the posterior forceps, is a white matter fibre bundle which connects the occipital lobes and crosses the midline via the splenium of the corpus callosum.
The forceps minor, also known as the anterior forceps, is a white matter fibre bundle which connects the lateral and medial surfaces of the frontal lobes and crosses the midline via the genu of the corpus callosum.
The forearm is part of the upper limb below the (upper) arm and above the hand and wrist, comprising the radius and ulna bones. In the supinated anatomical position, the radius is lateral and the ulna is medial.
The elbow joint is superior and the wrist joint inferior. Forearm flexion and exten...
The forefoot is the portion of the foot distal to the midfoot and is composed of the metatarsals and the phalanges. The tarsometatarsal joints (TMTJ) joins the midfoot to the forefoot.
The fornix is the main efferent system of the hippocampus and an important part of the limbic system. It is one of the commissural fibres connecting the cerebral hemispheres.
Roughly C-shaped, the fornix extends from the hippocampus to the mammillary bodies of the hypothalamus an...
The term fornix (plural: fornices) is used for anatomical structures in multiple organ systems that all share an arch-like morphology:
History and etymology
Fornix is Latin for...
The fornix conjunctiva is loose soft tissue lying at the junction between the palpebral conjunctiva (covering the inner surface of the eyelid) and the bulbar conjunctiva (covering the globe). Each eye has two fornices, the superior and inferior fornices. The fornix permits freedom of movement of...
The fornices are superior recesses of the vagina formed by the protrusion of the cervix into the vaginal vault. There is a large posterior fornix and a smaller anterior fornix with two small lateral fornices.
History and etymology
Fornix is Latin for 'arch'.
The fossa navicularis refers to a normal mild dilatation of the urethra. It occurs at the most distal/downstream portion of the urethra.
It is more evident in males, where it occurs in the penile/pendulous urethra, near the urethral meatus. There is also a fossa navicularis in women: the more f...
The fossa of Rosenmüller, also known as the posterolateral pharyngeal recess, is the most common site of origin for nasopharyngeal carcinoma.
It is located superior and posterior to the torus tubarius (the posterior projection of the cartilaginous portion of the Eustachian tube) ...
The fossa ovale (or ovalis) is the small oval depression in the interatrial septum at the site of the closed foramen ovale, which closes once fetal circulation ceases in the first few minutes of postnatal life. It represents the overlapping primary and secondary septa of the interatrial septum. ...
The fourth ventricle is one of the components of the ventricular system in the brain, along with the lateral and third ventricles. It extends from the cerebral aqueduct (of Sylvius) to the obex and is filled with CSF.
CSF enters the ventricle via the cerebral aqueduct and leaves via one of four...
The fovea ethmoidalis is a portion of the ethmoid bone and represents its superior portion (part of the ethmoid roof) which is seen as a continuation of the superior orbital roof to the cribriform plate.
A foveola pharyngica recess is one of the variants of the inferior median clival canal, thought to represent a remnant of the notocord. It represents a blind ending recess in the anteroinferior surface (nasopharyngeal) surface of the clivus 1,2.
Frenulum (plural: frenula) is an anatomical term and refers to a small fold of soft tissue that checks the movement of an anatomical part.
frenulum (ileocaecal valve)
frenulum (labia minora)
History and etymology
Frenulum derives from...
The frontal bone is a skull bone that contributes to the cranial vault. It contributes to form part of the anterior cranial fossa.
The frontal bone has two portions:
vertical portion (squama): has external/internal surfaces
horizontal portion (orbital): has superior/inferior su...
The frontal bullar cells are a subset of variably present frontal recess cells located above the ethmoid bulla.
They are nearly identical to suprabullar cells. The distinguishing features with the latter are that the frontal bullar cells are located above the frontal ostium and ext...
Frontal cells are anterior ethmoid air cells located along the anterior aspect of the frontal recess. They are a subset of frontal recess cells and are classified into four types according to Kuhn's classification.
They are seen on CT in 20-33% of patients 1.
functional endoscopic si...
The frontal infundibulum is a term that refers to the funnel-shaped inferior narrowing of the frontal sinus. Together with the frontal ostium and frontal recess, it forms the frontal sinus outflow tract.
Frontal intersinus septal cells, also known as interfrontal sinus septal cells, are a subtype of medial frontal recess cells.
The frnotal intersinus septal cells lie within the intersinus septum between the frontal sinuses. They usually drain in the medial aspect of the frontal r...
The frontal lobe is by far the largest of the four lobes of the cerebrum (along with the parietal lobe, temporal lobe, and occipital lobe), and is responsible for many of the functions which produce voluntary and purposeful action.
The frontal lobe is the largest lobe accounting...
The frontal nerve is the largest and main branch of the ophthalmic division of the trigeminal nerve. It divides off the ophthalmic division just before entering the orbit through the superior orbital fissure outside and superolateral to the tendinous ring, where it lies between the lacrimal nerv...
The frontal ostium is an opening of the frontal sinus below the frontal infundibulum that drains into the frontal recess. Together with the frontal infundibulum and recess, it forms the frontal sinus outflow tract.
The frontal pole is one of the three poles of the brain (along with the occipital pole and temporal pole), and corresponds to the anterior most rounded point of the frontal lobe.
It does not have easily defined boundaries, but is roughly equivalent to the frontopolar cortex, which in turn is co...
The frontal recess is an opening in the inferior aspect of the frontal sinuses that allows drainage of the sinus.
The frontal recess is also known as the nasofrontal duct. However, since it doesn't have bony walls of its own, it is more appropriately referred to as a recess rather ...
Frontal recess cells are anterior ethmoid air cells that pneumatise the frontal recess. Their clinical relevance lies in their potential to obstruct the frontal recess outflow. As such, they should be reported by the radiologist preoperatively, especially in cases of frontal sinusitis.
The frontal sinuses are the paranasal sinuses within the frontal bone. They are lined with mucosa and are most often two in number.
location: anterior frontal bones on either side of the midline behind the brow ridges
blood supply: supratrochlear, supraorbital and anterior ethmoidal a...
The frontal sinus outflow tract is the drainage pathway of the frontal sinus. It is an hourglass-shaped structure with its waist at the frontal ostium.
Depending on the references, the term frontal sinus outflow tract is either used synonymously with frontal recess or it can ref...
The frontoethmoidal suture is a short cranial suture located in the anterior cranial fossa, between the orbital process of frontal and orbital plate of ethmoid bones. It forms part of the medial wall of the orbit.
The anterior and posterior ethmoidal foramina are seen just superior to it, throu...
The frontolacimal suture is the cranial suture between the frontal and lacrimal bones.
The frontomaxillary suture is the site where the nasal process of frontal bone meets the frontal process of the maxilla.
The frontonasal suture is the cranial suture between the frontal bone and the two nasal bones. This suture meets the internasal suture at the nasion.
The frontopolar artery is a branch of the A2 segment of the anterior cerebral artery (ACA), commonly arising after the medial frontobasal artery and coursing obliquely across the medial surface of the cerebral hemisphere towards the frontal pole.
The frontopolar cortex is located at the frontal pole of each frontal lobe, and is comprised of three roughly horizontal gyri: superior, middle and inferior frontopolar gyri.
It contains Brodmann area 10, which is thought to contribute to many aspects of cognition 1,2.
Despite many studies re...
The frontozygomatic suture (or zygomaticofrontal suture) is between the frontal process of the zygomatic bone and the zygomatic process of the frontal bone.
Fundus (plural: fundi) is used as an anatomical term for many organs and is generally used in the sense of a part that is the lower part or is distant from the main aperture:
fundus (urinary bladder)
fundus (internal acoust...
The fusiform gyrus, also known as the temporo-occipital gyrus is a structure that lies on the basal surface of the temporal and occipital lobes. It forms part of Brodmann area 37, along with the inferior and middle temporal gyri. As its name suggests, it is composed of a temporal or anterior por...
The galea aponeurotica (also called the Galeal or epicranial aponeurosis or the aponeurosis epicranialis) is a tough fibrous sheet of connective tissue that extends over the cranium, forming the middle (third) layer of the scalp.
The gallbladder is a pear-shaped musculomembranous sac located along the undersurface of the liver. It functions to accumulate and concentrate bile between meals.
The adult gallbladder measures from 7-10 cm in length and 3-4 cm in transverse diameter 6. The gallbladd...
Agenesis of the gallbladder is a rare congenital anomaly.
The incidence is <0.1% (range 0.04-0.1%). There is strong female predominance present among the symptomatic cases.
Most patients with agenesis of the gallbladder are asymptomatic. Although some patie...
Gallbladder duplication is a rare anatomic anomaly characterised by the presence of an accessory gallbladder. There is no increased risk for malignancy or calculi compared to a single gallbladder.
Prevalence is estimated at 1 in 3000.
Boyden's classification divi...
Gallbladder triplication is an extremely rare anomaly. There are three types of gallbladder triplication are described according to the number of cystic duct and their insertion:
Three gallbladders and three cystic ducts which unite to form a common cystic duct before joining the common bile du...
The gastric bubble is a radiolucent rounded area generally nestled under the left hemidiaphragm representing gas in the fundus of the stomach.
On a lateral radiograph, the gastric bubble is usually located between the abdominal wall and spine. It can be seen on chest or abdominal plain films. I...
Gastric lymph node stations were originally divided into 16 groups proposed by the Japanese Research Society for Gastric Cancer in 1963.
The areas of stomach which drain into regional lymph nodes:
cardia and proximal lesser curvature drain into left gastric lymph nodes, then int...
The gastrocnemius muscle is one of the calf muscles (triceps sure) in the superficial posterior compartment of the leg which sits superificial to the much larger soleus muscle. It gives the calf its distinctive two-headed appearance and is a primary plantarflexor.
origin: superior to a...
The gastroduodenal artery (GDA) is a terminal branch of the common hepatic artery which mainly supplies the pylorus of the stomach, proximal duodenum, and the head of the pancreas. Due to its proximity to the anterior wall of the first part of the duodenum, the gastroduodenal artery is one of th...
The gastrointestinal tract includes any part of the oral cavity, oropharynx, hypopharynx, oesophagus, stomach, small bowel, colon, rectum and anal canal.
The gastro-oesophageal junction (GOJ) (also known as the oesophagogastric junction) is the part of the gastrointestinal tract where the oesophagus and stomach are joined.
The GOJ is normally mostly intra-abdominal and is 3-4 cm in length. To some extent, the oesophagus slides in ...
The gastrosplenic ligament is a peritoneal ligament which is formed by ventral part of dorsal mesentery.
The gastrosplenic ligament extends from the greater curvature of the stomach to the hilum of the spleen. It contains the short gastric arteries.
General anatomy is best described as the study of general anatomic concepts and structures removed from the specific regional anatomy focus.
To facilitate clinical description, the general topography of the abdomen is divided into four quadrants or nine regions by lines on the surface of the anterior abdominal wall. The four quadrants are created by vertical and horizontal lines passing through the umbilicus, whereas the nine regions...
The geniculate ganglion contains fibres for taste and somatic sensation and is located in the petrous temporal bone.
It is located at the first genu of the facial nerve at the anterior most part of the Fallopian canal at the junction between the labyrinthine and tympanic segment...
The genioglossus muscle is a fan-shaped extrinsic muscle of the tongue which makes up the bulk of the tongue.
origin: superior mental spine of the symphysis menti (posterior surface of midline mandible)
insertion: entire tongue mass and body of the hyoid bone
nerve supply: hypoglossa...
The geniohyoid muscle is one of the suprahyoid muscles of the neck that is innervated by the ventral ramus of C1. Geniohyoid draws the hyoid bone up and forward during mastication and assists the opening of the mandible.
origin: inferior mental spine of the mandible also known as the g...