Articles
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More than 200 results
Article
Abducens nerve
The abducens nerve is the sixth cranial nerve (CN VI). It is a motor nerve responsible for abduction of the eye (TA: nervus abducens or nervus cranialis VI). It courses from the abducens nucleus, located in the dorsal pons, up to the cavernous sinus, via a long cisternal segment that is prone to...
Article
Aberrant internal carotid artery
Aberrant internal carotid artery is a variant of the internal carotid artery and represents a collateral pathway resulting from involution of the normal cervical portion (first embryonic segment) of the internal carotid artery 5.
Gross anatomy
There is consequent enlargement of the usually sma...
Article
Aberrant right subclavian artery
Aberrant right subclavian arteries (ARSA), also known as arteria lusoria, are among the commonest aortic arch anomalies.
Epidemiology
The estimated incidence is 0.5-2% 1.
Associations
as can be expected from the embryological development of the artery, the right recurrent laryngeal nerve is...
Article
Accessory middle cerebral artery
The accessory middle cerebral artery is a variant of the middle cerebral artery (MCA) that arises from the anterior cerebral artery (ACA). It is different from a duplicated middle cerebral artery, in which the duplicated vessel originates also from the distal end of the internal carotid artery (...
Article
Accessory right inferior hepatic vein
An accessory right inferior hepatic vein is the most common variation of the hepatic veins, and may be multiple 1. It is present in up to 48% of the population and drains the posteroinferior part of the right lobe directly into the inferior vena cava (IVC) 1-3.
Variations in hepatic vascular an...
Article
Acromial types
Acromial types were initially divided into three types (known as the Bigliani classification) 3, to which a fourth has been added 2. These classifications are used as a standardized way of describing the acromion and predicting to a degree the incidence of impingement.
Classification
This cla...
Article
Acromioclavicular joint configuration
There is much variation in acromioclavicular joint configuration, which may be confused with pathology. The relationship of the acromion to the distal clavicle at the AC joint can be described in the coronal plane as 1-3:
horizontal: normal
low-lying: associated with shoulder impingement (unfo...
Article
Agger nasi cells
Agger nasi air cells are the most anterior ethmoidal air cells lying anterolateral and inferior to the frontal recess and anterior and above the attachment of the middle turbinate. They are located within the lacrimal bone and therefore have as lateral relations the orbit, the lacrimal sac and t...
Article
Aorta
The aorta, the great artery, is the largest artery of the human body and carries oxygenated blood ejected from the left ventricle to the systemic circulation. It is divided into:
thoracic aorta
ascending aorta
aortic arch
descending aorta
abdominal aorta
It has branches from each section a...
Article
Aortic arch
The aortic arch represents the direct continuation of the ascending aorta and represents a key area for a review of normal variant anatomy and a wide range of pathological processes that range from congenital anomalies to traumatic injury.
Summary
origin: continuation of the ascending aorta at...
Article
Variant anatomy of the aortic arch
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.
Gross anatomy
Normally, the aorta ascends in the superior mediastinum to the level of the sternal notch before arc...
Article
Arnold's nerve
Arnold's nerve, also known as the auricular branch or mastoid branch, of the vagus nerve (CN X) is a small sensory nerve supplying the skin of the external acoustic meatus.
Terminology
The greater occipital nerve has also been known in the past - confusingly - as the nerve of Arnold.
The use...
Article
Ascending aorta
The ascending aorta is the first part of the aorta and begins at the sinotubular junction (the junction of the aortic root and ascending aorta) and terminates as it exits the fibrous pericardium where it becomes the aortic arch, in the transthoracic plane (of Ludwig). It is located obliquely jus...
Article
Asymmetrically large jugular bulb
Asymmetrically large jugular bulbs are entirely normal and asymptomatic; its only significance is to distinguish it from pathology.
The size of the jugular bulbs is variable, with the right side being significantly larger than the left in two-thirds of people.
A normal but large bulb will have...
Article
Azygos lobe
An azygos lobe is a normal variant that develops when a laterally displaced azygos vein creates a deep pleural fissure in the apical segment of the right upper lobe during embryological development. It is not a true accessory lobe as it does not have its own bronchus or corresponding bronchopulm...
Article
Azygos vein
The azygos vein is a unilateral vessel that ascends in the thorax to the right of the vertebral column, carrying deoxygenated blood from the posterior chest and abdominal walls. It forms part of the azygos venous system.
Terminology
The spelling azygous when referring to the vein is incorrect,...
Article
Bicornuate uterus
A bicornuate uterus is a type of uterine duplication anomaly. It can be classified as a class IV Mullerian duct anomaly.
Epidemiology
Overall, congenital uterine anomalies occur in ~1.5% of females (range 0.1-3%). Bicornuate uteri are thought to represent ~25% (range 10-39%) of Mullerian duct ...
Article
Bifid rib
A bifid or bifurcated rib is a congenital skeletal abnormality where the affected rib has a forked sternal end. They are thought to occur in ~0.2% of the population and there may be a female and right-sided predilection 2.
Epidemiology
Associations
Gorlin (nevoid basal cell carcinoma) syndrom...
Article
Bill bar
Bill bar (TA: crista verticalis) also known as the vertical crest, is a bony anatomical landmark that divides the superior compartment of the internal acoustic meatus into an anterior and posterior compartment. Anterior to Bill bar, in the anterior superior quadrant, are the facial nerve (CN VII...
Article
Bovine arch
Bovine arch is the most common variant of the aortic arch and occurs when the brachiocephalic (innominate) artery shares a common origin with the left common carotid artery.
Epidemiology
A bovine arch is present in ~15% (range 8-27%) of the population and is more common in individuals of Afri...