Otosclerosis is a congenital or spontaneous-onset disease characterized by abnormal bone remodeling in the inner ear. Often this causes the stapes to adhere to the oval window, which impedes its ability to conduct sound, and is a cause of conductive hearing loss. Clinical otosclerosis is found in about 1% of people, although it is more common in forms that do not cause noticeable hearing loss. Otosclerosis is more likely in young age groups, and females. Two common treatments are stapedectomy, the surgical removal of the stapes and replacement with an artificial prosthesis, and stapedotomy, the creation of a small hole in the base of the stapes followed by the insertion of an artificial prosthesis into that hole.
Clinical relevance
Stapes
Stapes | Clinical relevance
Yes, its impairment causes conductive hearing loss In 0.01-0.02% of people, the stapedial artery does not regress, and persists in the central foramen. In this case, a pulsatile sound may be heard in the affected ear, or there may be no symptoms at all. Yes, a pulsatile sound may be heard in the affected ear, or there may be no symptoms at all Yes, in 0.01-0.02% of people, the stapedial artery does not regress, and persists in the central foramen. In this case, a pulsatile sound may be heard in the affected ear, or there may be no symptoms at all.
what are the 3 smallest bones in the human body
user
Strapes is one of them
assistant
what is the size of this above bone?
user
Roughly 3 x 2.5mm
assistant
which part of the body is this located?
user
Middle ear of humans
assistant
besides the human, is this bony structure present in other living species in the animal kingdom?
user
It is one of three ossicles in mammals, in non-mammalian four-legged animals its homologous form is called the columella
assistant
what are the functions this bony structure serves?
user
It transmits sound vibrations from the incus to the oval window, a membrane-covered opening to the inner ear.
assistant
are there any variations of this bony structure?
user
It appears to be relatively constant in size in different ethnic groups
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can this bony structure get affected or impaired?
user
Surgery may be complicated by a persistent stapedial artery, fibrosis-related damage to the base of the bone, or obliterative otosclerosis, resulting in obliteration of the base.
Stapes | Clinical relevance
The stapes appears to be relatively constant in size in different ethnic groups. In 0.01-0.02% of people, the stapedial artery does not regress, and persists in the central foramen. In this case, a pulsatile sound may be heard in the affected ear, or there may be no symptoms at all. Rarely, the stapes may be completely absent.
Stapes | Variation
Occasionally the joints between the ossicles become rigid. One condition, otosclerosis, results in the fusing of the stapes to the oval window. This reduces hearing and may be treated surgically.
Ossicles | Clinical relevance
The morphology of the stapes suggests that the animal was capable of hearing high-frequency sound. "B. woodi" does not possess lateral line sulci or an ossified branchial system. The principal method of respiration was probably buccal (gulping air through mouth) rather than costal (expanding chest volume to take in air), indicated by the small straight ribs.
Balanerpeton | Introduction
The stapes develops from the second pharyngeal arch during the sixth to eighth week of embryological life. The central cavity of the stapes, the obturator foramen, is due to the presence embryologically of the stapedial artery, which usually regresses in humans during normal development.
Stapes | Development
Otosclerosis is a congenital or spontaneous-onset disease characterized by abnormal bone remodeling in the inner ear. Often this causes the stapes to adhere to the oval window, which impedes its ability to conduct sound, and is a cause of conductive hearing loss. Clinical otosclerosis is found in about 1% of people, although it is more common in forms that do not cause noticeable hearing loss. Otosclerosis is more likely in young age groups, and females. Two common treatments are stapedectomy, the surgical removal of the stapes and replacement with an artificial prosthesis, and stapedotomy, the creation of a small hole in the base of the stapes followed by the insertion of an artificial prosthesis into that hole.
Stapes | Clinical relevance
The stapes is one of three ossicles in mammals. In non-mammalian four-legged animals, the bone homologous to the stapes is usually called the columella; however, in reptiles, either term may be used. In fish, the homologous bone is called the "hyomandibular", and is part of the gill arch supporting either the spiracle or the jaw, depending on the species. The equivalent term in amphibians is the "".
Stapes | Animals
For example, the lower branch of the squamosal bone is shortened to offset the tall dorsal process of quadratojugal which connects to it. On the other hand, the rear branch jugal bone lengthens to fill some of the space left by the shortening of the anterior process of the quadratojugal. In archosauriforms, the jugal even re-encloses the lower temporal fenestra. The stapes are long, thin, and solid, without a perforating hole (stapedial foramen) present in the more robust stapes of other reptiles.
Archosauromorpha | Skull
The stapes is the third bone of the three ossicles in the middle ear. The stapes is a stirrup-shaped bone, and the smallest in the human body. It rests on the oval window, to which it is connected by an annular ligament. The stapes is described as having a base, resting on the oval window, as well as a head that articulates with the incus. These are connected by anterior and posterior limbs (). The stapes articulates with the incus through the incudostapedial joint. The stapes is the smallest bone in the human body, and measures roughly 3 x 2.5mm, greater along the head-base span.
Stapes | Structure
The configuration of the stapes is intermediate between non-amniote tetrapods and amniotes. On the one hand, its connection to the otic notch is unusual, since true reptiles and other amniotes have lost an otic notch, forcing the tympanum and stapes to shift downwards towards the quadrate bone of the jaw joint. On the other hand, the thin, sensitive structure of "Seymouria"'s stapes is a specialization over most non-amniote tetrapods, which have a thick stapes useless for hearing yet useful for reinforcing the skull. The inner ear of "Seymouria baylorensis" retains a cochlear recess located behind (rather than below) the vestibule, and its anterior semicircular canal was likely encompassed by a cartilaginous (rather than bony) supraoccipital.
Seymouria | Skull
If the mobility of the stapes is reduced due to otosclerosis, then stapedius muscle contraction does not significantly decrease the admittance. When acoustic reflex testing is conducted, the acoustic reflex thresholds (ART) cannot be determined when attempting to measure on the affected side. Also, a conductive pathology will attenuate the test stimuli, resulting in either elevated reflex thresholds or absent reflexes when the stimulus is presented in the affected ear and measured in the other ear.
Otosclerosis | Audiometry
In the tetrapod and higher clades from the lower-middle Famennian there are several defining changes on the basis of anatomy of "Ichthyostega", "Tulerpeton", and "Acanthostega". In the cranium, there is a stapes derived from the hyomandibular of fishes; a single bilateral pair of nasal bones, and a fenestra ovalis in the otic capsule of the braincase. The opening of the otic wall of the braincase can be considered a paedomorphic feature for tetrapods and is linked to the stapes functionally. The stapes was thought to be just a structural support between the palate and the stapedial plate of the braincase.
Skeletal changes of organisms transitioning from water to land | Head changes in aquatic tetrapods
The stapes bone transmits movement to the oval window. As the stapes footplate moves into the oval window, the round window membrane moves out, and this allows movement of the fluid within the cochlea, leading to movement of the cochlear inner hair cells and thus hearing. If the round window were to be absent or rigidly fixed (as can happen in some congenital abnormalities), the stapes footplate would be pushing incompressible fluid against the unyielding walls of the cochlea. It would therefore not move to any useful degree leading to a hearing loss of about 60dB. This is, unsurprisingly, the same as for conditions where the stapes itself is fixed, such as otosclerosis.
Round window | Function
Complications of stapedectomy: When a stapedectomy is done in a middle ear with a congenitally fixed footplate, the results may be excellent but the risk of hearing damage is greater than when the stapes bone is removed and replaced (for otosclerosis). This is primarily due to the risk of additional anomalies being present in the congenitally abnormal ear. If high pressure within the fluid compartment that lies just below the stapes footplate exists, then a perilymphatic gusher may occur when the stapes is removed. Even without immediate complications during surgery, there is always concern of a perilymph fistula forming postoperatively.
Stapedectomy | Complications
The occiput and the first neck vertebra of the holotype of "Lagenanectes richterae" show pathological alterations of the bony structure. They may have been caused by an infection.
Lagenanectes | Pathologies
These are the most unusual of the braincase bones, and were previously misidentified as stapes. While they are not stapes, it is difficult to be certain what they are. As mentioned, they are sutured to the tubera basioccipitalia, and so could not have moved freely, meaning that they were not bones for the transmission of sound in this manner. Medially, they are sutured to the posterodorsal margins of the tubera basioccipitalia by a strongly serrate and partially intergrown suture. The posterior surface of this forms a steeply inclined trough running from the suture to the distal extremity of the paraoccipital process.
Phantomosaurus | Opisthotic bones
The stapes is commonly described as having been discovered by the professor Giovanni Filippo Ingrassia in 1546 at the University of Naples, although this remains the nature of some controversy, as Ingrassia's description was published posthumously in his 1603 anatomical commentary '. Spanish anatomist Pedro Jimeno is first to have been credited with a published description, in ' (1549). The bone is so-named because of its resemblance to a stirrup (), an example of a late Latin word, probably created in mediaeval times from "to stand" (), as stirrups did not exist in the early Latin-speaking world.
Stapes | History
The ossicles are suspended in the head and loosely coupled to the skull. When the head moves, the ossicles move out of phase with the head, but still follow the same cyclic motion. This causes the stapes to move in and out of the oval window. When vibrations come from the mastoid, inertial bone-conduction is greatest below 800 Hz. Putting the bone vibrator on the forehead instead of the mastoid does not significantly create this affect.
Bone conduction auditory brainstem response | Inertial bone-conduction
The woven bone's "undulating fibrous bundles" were observed oriented in the direction of the "m. brachialis". The lesion's fusion and lack of porosity at its near and far ends indicate the periostitis was inactive or healed. McWhinney and the other researchers argued that this injury would have been a continuous source of hardship for the animal. It would have exerted pressure on the muscles. This pressure would have compressed the muscles' blood vessels and nerves, reducing the range of motion of both the limb's flexor and extensor muscles. This effect would have hindered the "mM. brachialis", "m. brachoradialis", and to a lesser degree the "m.
Camarasaurus | Paleopathology
The stapedius emerges from a pinpoint foramen in the apex of the pyramidal eminence (a hollow, cone-shaped prominence in the posterior wall of the tympanic cavity), and inserts into the neck of the stapes.
Stapedius muscle | Structure
The clinical significance of this structure is due to the median nerve and brachial artery which may pass underneath the "arch" formed by the process and ligament over the humeral body. Within this space the nerve may be compressed leading to supracondylar process syndrome. The ligament may also affect the ulnar nerve after an anterior transposition surgery, which is a commonly performed to manage patients with a cubital tunnel syndrome, a form of ulnar nerve entrapment. It is unlikely that the ulnar nerves are affected in patients without transposition surgeries.
Struthers' ligament | Introduction
Oyen et al.’s data suggested that more prognathic individuals experienced a decrease in load/lever efficiency. This transmits tension via the frontal process of the maxilla to the supraorbital region, resulting in a contemporary reinforcement of this structure. This was also correlated to periods of tooth eruption.
Brow ridge | Bio-mechanical model
The parietosquamosal shelf was not reduced in size, and the frontoparietal suture was open. Sub-adults had mound-like domes, with the back part of the parietal and skull-roof being flat. The supratemporal fenestrae showed asymmetry in size, and the closure of the frontoparietal suture was variable. The nodes were stretched or almost obliterated as the dome expanded during growth, with a tesserated surface remaining. The pattern was often obliterated at the highest point (apex) of the dome, the area where maximum expansion occurred. The tubercles on the skull were stretched in different directions, and those at the margin of the parietosquamosal shelf may have been hypertrophied (enlarged) tubercles.
Stegoceras | Ontogenetic changes
The dorsal process of the stapes in "Theriognathus" is greatly reduced or entirely absent. The dentary is short, shaped like a banana, and continuously tapers anteriorly to a narrow edge. The dentarys’ lateral surface is smooth. The posterodorsal terminal end of the coronoid process is more rounded, and the dorsal extent terminates below the middle of the orbit in adults. The postdentary bones are reduced to form a free standing coronoid process. The reflected lamina is spade shaped and does not extend below the dentary The area between left and right dentaries remains relatively long and narrow just posterior to symphyseal region.
Theriognathus | Lower jaw
Paralysis of the stapedius allows wider oscillation of the stapes, resulting in heightened reaction of the auditory ossicles to sound vibration. This condition, known as hyperacusis, causes normal sounds to be perceived as very loud. Paralysis of the stapedius muscle may result when the nerve to the stapedius, a branch of the facial nerve, is damaged, or when the facial nerve itself is damaged before the nerve to stapedius branches. In cases of Bell's palsy, a unilateral paralysis of the facial nerve, the stapedius is paralyzed and hyperacusis may result.
Stapedius muscle | Clinical significance
The dorsal blood supply, particularly of the proximal portion, is highly variable. Sometimes the fibers of the abductor pollicis brevis emerge from the tubercle.
Scaphoid bone | Variation
Instead of normal suture patterning along the developing skull, the affected organisms displayed a mosaic of sites where bone formation was being initiated but not completed. This caused the appearance of many small irregular bones instead of the normal smooth frontal and parietal bones. These phenotypic shifts corresponded to an overproliferation of Runx2+ osteoblast progenitors indicating that the phenotype observed was related to an abundance of initiation sites for bone proliferation creating many pseudo-sutures.
Sp7 transcription factor | In adult organisms
The stapes or stirrup is a bone in the middle ear of humans and other mammals which is involved in the conduction of sound vibrations to the inner ear. This stirrup-shaped bone is connected to the oval window by its annular ligament, which allows the footplate to transmit sound energy through the oval window into the inner ear. The stapes is the smallest and lightest bone in the human body, and is so-called because of its resemblance to a stirrup ().
Stapes | Introduction
A wide range of treatments are possible, including rest, surgery and casting.
Trapezoid bone | Clinical Significance
Another clinical example in which the horizontal extent of crestal bone loss due to biologic width formation can negatively affect the peri-implant bony architecture is a situation in which the buccal plate of the alveolar process is very thin and lies wholly or substantially within the halo of the horizontal component of the biologic width. If an implant is placed within 1.5 mm of the facial aspect of the buccal plate, it will be obliterated for a vertical distance of approximately 1.5-2 mm by the formation of the biologic width on the body of the implant fixture, which can lead to complications related to esthetics and long-term maintenance.
Platform switching | Horizontal component affecting buccal plate in narrow alveolar crests
The stapes remained in contact with the quadrate bone, but functioned as auditory ossicles rather than supports for the brain case. As a result, the quadrate bones of therapsids likely had a dual function in both the jaw joint and auditory system.
Evolution of mammalian auditory ossicles | Early therapsid jaws and ears
The pterygoids and palatines were seemingly toothless, although this observance may be due to poor preservation. The tip of each ectopterygoid expands into a fan-shaped structure, and the suborbital fenestra is very short.
Prolacertoides | Description
The results of this surgery are generally most reliable in patients whose stapes has lost mobility because of otosclerosis. Nine out of ten patients who undergo the procedure will come out with significantly improved hearing while less than 1% will experience worsened hearing acuity or deafness. Successful surgery usually provides an increase in hearing acuity of about 20 dB. That is as much difference as having your hands over both ears, or not. However, most of the published results of success fall within the speech frequency of 500 Hz, 1000 Hz and 2000 Hz; poorer results are typically obtained in the high frequencies, but these are normally less hampered by otosclerosis in the first place.
Stapedectomy | Introduction
Caudal to what will eventually become the stapes, Reichert's cartilage also forms the styloid process of the temporal bone. The cartilage between the hyoid bone and styloid process will not remain as development continues, but its perichondrium will eventually form the stylohyoid ligament.
Pharyngeal arch | Reichert's cartilage
A band of bone material of decreased density may form alongside the surface of the bone. Thickening of the periosteum occurs. The formation of callouses in the affected area is also common. This gives the appearance of a false fracture. Typical sites of involvement are the axillary margins of the scapula, ribs, pubic rami, proximal ends of the femur and ulna.
Pseudofracture | Structure
"Styloichthys" is characterized by large pores on the cosmine surface. These pores are often spoon-shaped and arranged in parallel grooves. There is a jagged margin between ethmosphenoid and otoccipital shields, an otoccipital with a wide flat surface carrying no vestibular fontanelle. The snout bends sharply downward and is slightly concave. The lower jaw has a ventrally protruding flange formed by prearticular and meckelian bone. Also characteristic of "Styloichthys" is the lyre-shaped trajectory of the supraorbital canal, a fenestra ventralis, small internasal cavities, three coronoids in the lower jaw, an eyestalk and a slender postorbital pila which connects the basipterygoid process and the side of the braincase wall.
Styloichthys | Description
Situated between the incus and the inner ear, the stapes transmits sound vibrations from the incus to the oval window, a membrane-covered opening to the inner ear. The stapes is also stabilized by the stapedius muscle, which is innervated by the facial nerve.
Stapes | Function
This species is likely now extinct.
Theliderma stapes | Conservation
CHL in otosclerosis is caused by two main sites of involvement of the sclerotic (or scar-like) lesions. The best understood mechanism is fixation of the stapes footplate to the oval window of the cochlea. This greatly impairs movement of the stapes and therefore transmission of sound into the inner ear ("ossicular coupling"). Additionally the cochlea's round window can also become sclerotic, and in a similar way impair movement of sound pressure waves through the inner ear ("acoustic coupling"). Conductive hearing loss is usually concomitant with impingement of abnormal bone on the stapes footplate. This involvement of the oval window forms the basis of the name fenestral otosclerosis.
Otosclerosis | Pathophysiology
As evolution later attached the cranium of terrestrial vertebrates to the rest of the skull, the hyomandibula lost its supportive function and became an interior organ, the stapes, and thus its secondary function had become its primary function.
Hyomandibula | Evolutionary context
Although all material consists of juvenile specimens, they all appeared to be developing an anatomical structure similar to that of "Partula hebe".
Partula pearcekellyi | Anatomy
freyi". The width and length of the head are the same at and the scapes measure The length of the mesosoma varies in the holotype and paratype, ranging from .
Sphecomyrma | "S. canadensis"
This system had evolved independently within several different amphibian lineages. The impedance matching ear had to meet certain conditions to work. The stapes had to be perpendicular to the tympanum, small and light enough to reduce its inertia, and suspended in an air-filled cavity. In modern species that are sensitive to over 1 kHz frequencies, the footplate of the stapes is 1/20th the area of the tympanum. However, in early amphibians the stapes was too large, making the footplate area oversized, preventing the hearing of high frequencies. So it appears they could only hear high intensity, low frequency sounds—and the stapes more probably just supported the brain case against the cheek.
Tetrapod | Hearing
The posterolateral borders were rounded and lacked spines. The compound eyes appear as anterolateral reniform (bean-shaped) elevations in the surface of the prosoma. The opisthosoma increased slightly its width in the third and fourth segments, then decreased slightly until the seventh segment. All the tergites (the dorsal part of the segments) were similar, superimposing strongly on each other, with the half of the first segment being hidden under the prosoma. The rest of tergites were more slightly superimposed, indicating a great flexibility and even the ability to roll up itself. The telson was trapezoidal, but Størmer mistook it as the twelfth segment of the body, suggesting a hypothetical lanceolate (lance-shaped) or fan-shaped telson.
Paleomerus | History of research
The resulting syndrome depends on the structure affected. Stenoses/strictures of other bodily structures/organs include:
Stenosis | Types
Fixation of the stapes within the oval window causes a conductive hearing loss. In pure-tone audiometry, this manifests as air-bone gaps on the audiogram (i.e. a difference of more than 10 dB between the air-conduction and bone-conduction thresholds at a given test frequency). However, medial fixation of the ossicular chain impairs both the inertial and osseotympanic modes of bone conduction, increasing the bone-conduction thresholds between 500 Hz and 4 kHz, and reducing the size of air-bone gaps. As 2 kHz is the resonant frequency of the ossicular chain, the largest increase in bone-conduction threshold (around 15 dB) occurs at this frequency – the resultant notch is called "Carhart's notch" and is a useful clinical marker for medial ossicular-chain fixation.
Otosclerosis | Audiometry
Air vibrations could not set up pulsations through the skull as in a proper auditory organ. The spiracle was retained as the otic notch, eventually closed in by the tympanum, a thin, tight membrane. The hyomandibula of fish migrated upwards from its jaw supporting position, and was reduced in size to form the stapes. Situated between the tympanum and braincase in an air-filled cavity, the stapes was now capable of transmitting vibrations from the exterior of the head to the interior. Thus the stapes became an important element in an impedance matching system, coupling airborne sound waves to the receptor system of the inner ear.
Tetrapod | Hearing
The resulting three-boned structure is still seen in modern monotremes, but in all other living mammals, the procoracoid has disappeared, and the coracoid bone has fused with the scapula, to become the coracoid process. These changes are associated with the upright gait of mammals, compared with the more sprawling limb arrangement of reptiles and amphibians; the muscles formerly attached to the procoracoid are no longer required. The altered musculature is also responsible for the alteration in the shape of the rest of the scapula; the forward margin of the original bone became the spine and acromion, from which the main shelf of the shoulder blade arises as a new structure.
Scapula | In other animals
The head and segments of the antenna tend to be smaller in the holotype specimen while in the paratype they are slightly larger. The pubescence is short but scattered throughout the body, measuring . The colour of the specimens appears to be light-brown. The metapleural gland exhibits a notably wide and oval-shaped orifice, (openings into the body). The separation between the orifice and the posterior portion of the propodeum is twice the diameter than the orifice itself. The cuticle situated in the anterior portion (referring to what is in front) of the orifice is thinner in contrast to the cuticle surrounding the mesosoma, where it is notably transparent.
Sphecomyrma | "S. freyi"
Ramírez-Velasco "et al." (2012) diagnosed "Huehuecanauhtlus" by a unique combination of characters. For example, two teeth exposed on the occlusal plane of the rostral third and the posterior third of the dentary and maxilla, respectively. It had seven sacral vertebrae and tall neural spines of posterior vertebrae, being between 3.5 and 4 times taller than their corresponding centra. As in "Claosaurus", its supraacetabular process is as long as 75% of the length of the central iliac plate, with an apex located above the posteroventral corner of the ischiac tuberosity. It differs from other hadrosauroids in possessing an extremely deflected preacetabular process of the ilium, so that the bisecting long axis of the process forms an angle less than 130° with the horizontal plane defined by the ischiac and pubic peduncles.
Huehuecanauhtlus | Description
Within mammals and other synapsids the columella has evolved into the stapes, a homologous bone within the newly evolved inner ear. As the tympanic cavity evolved to reduce in size, the columella shortened in length. The stirrup-shaped articular processes of the columella inspired a new name for this auditory ossicle, the stapes. The auditory ossicles continue to function in conducting transmitting sound through the auditory pathway; however, they have lost their function in conducting low frequency ground vibrations. Later-arising reptiles with columella likely evolved stronger limbs and a more crawling posture, which removed the body from the ground and prevented the transmission of ground-conducted sounds.
Columella (auditory system) | Homology in mammals
It also found that dome shape and size was strongly correlated with growth, and that growth was allometric (in contrast to isometric) from flat to domed, supporting "Ornatotholus" as a juvenile "Stegoceras". They also hypothesized that this model of dome growth, with dramatic changes from juvenile to adult, was the common developmental trajectory of pachycephalosaurs. These researchers noted that though Williamson and Carr's observation that the supratemporal fenestrae closed with age was generally correct, there was still a high degree of individual variation in the size of these fenestrae, regardless of the size of the frontoparietal, and this feature may therefore have been independent of ontogeny.
Stegoceras | Ontogenetic changes
The chelicerae match those observed in the males. On the prosoma, they display a pale median band behind the eyes. The transverse piece has marked paired excavations which meet at the midline and these excavation distances vary from nearly no space to about the width of one excavation.
Schizocosa stridulan | Appearance
Arthropods, however, show tremendous variation (over seven-fold) in sarcomere length, both between species and between muscles in a single individual. The reasons for the lack of substantial sarcomere variability in vertebrates is not fully known.
Sarcomere | Comparative structure
Accessory small bones called "ossicles" may be mistaken for avulsion fractures.
Anatomical variation | Clinical significance
A stapedectomy is a surgical procedure of the middle ear performed in order to improve hearing. If the stapes footplate is fixed in position, rather than being normally mobile, then a conductive hearing loss results. There are two major causes of stapes fixation. The first is a disease process of abnormal mineralization of the temporal bone called otosclerosis. The second is a congenital malformation of the stapes. In both of these situations, it is possible to improve hearing by removing the stapes bone and replacing it with a micro prosthesis - a stapedectomy, or creating a small hole in the fixed stapes footplate and inserting a tiny, piston-like prosthesis - a stapedotomy.
Stapedectomy | Introduction
These dynamic changes in the shape of the spinal canal are more pronounced in individuals with spinal stenosis. The amount of narrowing may be 67% in compared to 9% in healthy spines.
Neurogenic claudication | Pathophysiology
The posterior walls of the central sulcus appear to be affected more with age. Differences between genders regarding the average width of the central sulcus as one ages has also been shown. The average width of the central sulcus in males tends to increase more rapidly over time than that of females.
Central sulcus | Influences on Development
(1) Palatine and ectopterygoid reduced to narrow struts; (2) interpterygoid vacuity greatly expanded laterally; (3) humerus length:waist ratio of 6:10; (4) basioccipital and supraoccipital absent.
Amphibamiformes | Diagnosis
One affected individual had hip dysplasia, leading to dislocation, and another had metopic craniosynostosis, leading to a metopic ridge. Two individuals who did not survive to term had polydactyly of the thumb (preaxial polydactyly), flattened vertebrae (platyspondyly) and a rare chest wall malformation called a sternal cleft.
Strømme syndrome | Skeletal
The opisthotics were thickest at the base and generally similar to those of "Milleretta". They each connected to a thick yet complex stapes which possessed a conspicuous footplate, stapedial foramen, and a dorsal process. A knob on the outer edge of the stapes likely connected to a characteristic spur on the quadrate. What can be seen of the lower jaw indicates that it was primarily formed by the dentary in its front half, and the low, elongated surangular and angular in its rear half. The coronoid had a low peak and the tall articular had a small retroarticular process. Only one tooth was exposed, and it was similar to those of the maxilla, albeit smaller.
Australothyris | Description
The forces also influence the number, density, and alignment of trabeculae inside the bone. The bony trabeculae are aligned in the path of tensile and compressive stresses to provide maximum resistance to occlusal forces with a minimum of bone substance. When forces are increased, the bony trabeculae also increase in number and thickness and bone is added to the external surfaces. The periodontal ligament depends on stimulation provided by function to preserve its structure. Within physiologic limits the PDL can accommodate increased function by increasing its width. Forces that exceed the adaptive capacity of the periodontium produce injury called "trauma from occlusion".
Periodontium | External forces and the periodontium
In some of the eyeless genera ("Ductina") the suture coincides with the marginal suture, and thus appears to be absent. The part of the skeleton that is "tucked under" (the doublure) has no sutures crossing it to form a rostral plate. The thorax has 11 (rarely 10) segments, the side lobes (or pleurae) are furrowed, and the articulating facets distinct. The tailshield (or pygidium) is always smaller than the headshield (or cephalon), a situation called micropygous. In the Phacopidae a merger of the anterior and the two pairs of neighbouring lobes of the glabella forms a frontal lobe that expands forward and can be inflated and overhanging the frontal border.
Phacopidae | Description
The stapes, the bone transmitting sound waves from the eardrum to the middle ear, is elongated and not pierced by a foramen. Pterygoid teeth are typically lacking.
Ichthyosaur | Skull
The anular ligament, a ring-like structure that forms a seal between the end of the stapes and the rim of the vestibular foramen, was probably held in place by cartilage. The transfer of sound between the thin bony plate and the vestibular foramen in "Glanosuchus" was not as effective as it is in mammals, meaning that the animal had a less acute sense of hearing.
Glanosuchus | Hearing
The stapedius dampens the vibrations of the stapes by pulling on the neck of that bone. As one of the muscles involved in the acoustic reflex it prevents excess movement of the stapes, helping to control the amplitude of sound waves from the general external environment to the inner ear.
Stapedius muscle | Function
Phrynosomatid lizards show remarkable morphological diversity, including in the relative muscle fiber type composition in their hindlimb muscles. Ancestor reconstruction based on squared-change parsimony (equivalent to maximum likelihood under Brownian motion character evolution) indicates that horned lizards, one of the three main subclades of the lineage, have undergone a major evolutionary increase in the proportion of fast-oxidative glycolytic fibers in their iliofibularis muscles.
Ancestral reconstruction | Morphological and physiological character evolution
The basal margin is crenulate. The columella is tuberculose, above twisted plicate, below obsoletely truncate. The white umbilical area is spirally plicate with a crenulate margin. The thin parietal callus is wrinkled.
Clanculus kraussii | Description
Head, including the eyes, is broader than long. Dorsal portion of occipital margin is raised into a transverse carina from which short lengths of longitudinal carinae originate. Frontal carina is weak, terminating before reaching the posterior level of the eye. Clypeus with a median longitudinal carina and 1–3 pair of lateral carinae extending towards the anterior margin. Anterior clypeal margin is flat to weakly convex. Mesoscutum with distinct notauli forming a Y-shape. Parapsidal furrows reduced to weak impressions. Scuto-scutellar sulcus with 7–10 narrow longitudinal ridges visible in dorsal view. Propodeum is unarmed to weakly tuberculate, lacking teeth or spines. Propodeal lobes are obtusely triangular with a blunt or rounded apex; sometimes reduced to weak flanges.
Pristomyrmex tsujii | Males
The reason for this evolutionary change is still unknown; however, it may be to assist in grasping small objects and thin branches.
Sesamoid bone | Other animals
The structure of the nasal area indicates "Australodelphis" was likely to have enlarged nasiofacial muscles similar to "Mesoplodon" and indicate a possible ability to generate high-frequency sounds used in echolocation.
Australodelphis | Taxonomic placement
The bony palate is short, with its posterior end often located between the third molars. The alisphenoid strut, an extension of the alisphenoid bone of the skull that separates two foramina (openings) in the skull, is present in some individuals. The mastoid bone usually contains some openings. In the holotype, the head and body length is 130 mm, the tail length is 160 mm, the hindfoot length (without claws) is 31 mm, the ear length is 27 mm, and the skull length is 35.7 mm.
Nephelomys levipes | Introduction
Overall, through evolution of the species, a number of structures in the body have changed size, proportion, or location in order to accommodate bipedal locomotion and allow a person to stand upright and face forward. To help support the upper body, a number of structural changes were made to the pelvis. The ilial pelvic bone shifted forward and broadened, while the ischial pelvic bone shrank, narrowing the pelvic canal. These changes were occurring at the same time as humans were developing larger craniums.
Obstetrical dilemma | Human pelvis
The back and sides of sub-adult and adult skulls were ornamented by less modified tubercles. Before being incorporated into the enlarging dome, the skull bones expanded, resulting in junctions between these bones. The adult dome was broad and convex, and incorporated most of the shelf, which was reduced in size and overhung the occiput as a thick "lip". The supratempooral fenestrae were closed, but the suture between the frontoparietal and connected skull bones was not always closed in adults and subadults. In 2011, Ryan Schott and colleagues made a more comprehensive analysis of cranial dome ontogeny in "S. validum". The study found that the parietosquamosal shelf conserved the arrangement of ornamentation throughout growth, and that vascularity of the frontoparietal domes decreased with size.
Stegoceras | Ontogenetic changes
Bell's palsy can result from inflammation of the facial nerve where it leaves the skull at the stylomastoid foramen. Patients with Bell's palsy appear with facial drooping on the affected side.
Stylomastoid foramen | Clinical relevance
Because these ligaments lie in the posterior part of the vertebral canal, their hypertrophy can cause spinal stenosis, particularly in patients with diffuse idiopathic skeletal hyperostosis. Some studies indicate that the hypertrophy of these ligaments may be linked to a fibrotic process associated with increased collagen VI, which could represent an adaptive and reparative process in response to the rupture of elastic fibers.
Ligamenta flava | Clinical relevance
The bio-mechanical model predicts that morphological variation in torus size is the direct product of differential tension caused by mastication, as indicated by an increase in load/lever ratio and broad craniofacial angle. Research done on this model has largely been based on earlier work of Endo. By applying pressure similar to the type associated with chewing, he carried out an analysis of the structural function of the supraorbital region on dry human and gorilla skulls. His findings indicated that the face acts as a pillar that carries and disperses tension caused by the forces produced during mastication. Russell and Oyen "et al".
Brow ridge | Bio-mechanical model
The standard size and shape is retained throughout the number of species, but the variations between species of ornamentation may be due to physiological influences from the environment. Development occurs in two phases within the continuous process. The first phase involves the primary inner wall of the cyst being formed before the collar and surface, which is thin and occurs rapidly from a proximal to distal manner. The second phase is more controlled and occurs more slowly while the wall is being thickened, and the collar and surface ornamentation are being produced. Because of this process of making a stomatocyst, cysts can be found at any stage of development.
Mallomonas | Stomatocyst
However, they were too incompletely preserved to estimate the light sensitivity of the eyes. The footplates of the bony stapes are large, associated with hearing low-frequency sounds underground, although its inner-ear is not as specialised as "Kawingasaurus".
Kembawacela | Burrowing
The part of the skeleton that is ‘tucked under’ (the doublure) has no sutures crossing it to form a rostral plate.The thorax has 11 (rarely 10) segments, the side lobes (or pleurae) are furrowed, and the articulating facets distinct.
Phacopina | Description
ARHGAP31 mutations result in a loss of available active Cdc42 and consequently disrupt actin cytoskeletal structures, causing syndromic cutis aplasia and limb anomalies.
ARHGAP31 | Clinical relevance
An alisphenoid strut separates two foramina (openings) at the base of the skull, the buccinator-masticatory foramen and the foramen ovale accessorium. The pattern of grooves and foramina on the head indicates that the circulation of the arteries in the head of "T. ucucha" follows the primitive pattern. The tegmen tympani, the roof of the tympanic cavity, overlaps the suspensory process of the squamosal bone. At the back of the mandible (lower jaw), there is a capsular process to receive the root of the lower incisor, which is absent in "T. hylophilus".
Thomasomys ucucha | Description
The external mandibular fenestra is large. The dentary, lower jaw, teeth are quite pointed and have no front edge denticles; their rear edge is very straight. The holotype preserves a furcula and a basket of fifteen pairs of gastralia. The arms are weakly developed, with a slender humerus and ulna. The front top of the third metatarsal is not fully overgrown by the second and fourth metatarsals. The sickle claw of the second toe is relatively large and long for a troodontid.
Sinornithoides | Description
Nonetheless, different GISTs have different risk assessments of their tendency to recur or to metastasize, dependent on their site of origin, size, and number of mitotic figures. Due to the change in definition, clinical pathways of care before the year 2000 are largely uninformative in the current era.
Gastrointestinal stromal tumor | Classification
The preservation is so exceptional that studies have shown the species' numerous small ommatidia, distributed over the large eyes, could reduce the angle between ommatidia, thus improve their ability to detect small objects. Of the arguments above, it is posited by opponents that eyes are complex structures, and those in the Thylacocephala display clear and numerous affinities with compound eyes in other arthropod fossils, down to a cellular level of detail. The 'cephalic sac' structure itself is poorly preserved in Osteno specimens, a possible reason for interstitial 'sclerites'. The structural analogy with a cirripede peduncle lost supporting evidence when the 'ovaries' were shown to be alimentary residues, and the sac muscular system could be used to support the eyes.
Thylacocephala | Disagreements
It is these cells that are affected in the following diseases, – amyotrophic lateral sclerosis, spinal and bulbar muscular atrophy, Charcot–Marie–Tooth disease, progressive muscular atrophy, all spinal muscular atrophies, poliomyelitis, and West Nile virus.
Anterior grey column | Clinical significance
In "Anoualerpeton priscus", the suprapalatal fossa lies in the medial edge of the external nasal opening. In "Anoualerpeton unicus", however, it lies further mediad, outside the border of the external nasal opening.
Anoualerpeton | Morphology
Cephalon: Opisthoparian facial sutures. Early forms tend to have tapering, conical glabella with furrows extending far backwards while later forms with glabella expanding forwards to inflated frontal lobe. The hypostome is conterminant (e.g., Redlichia) or natant (e.g., Dolerolenus). The rostral plate is narrower than in suborder Olenellina, bound by rostral and connective sutures. Thorax: Fulcrate or non-fulcrate, typically with many segments (60+ in an Emmuelid). The axis is infrequently spine-bearing. Pygidium: Typically small, but can be larger and with many segments.
Redlichiina | Physiology
Large adenomas can cause remodeling of the underlying sphenoid bone altering the shape of the sella turcica.
Sella turcica | Clinical significance
The tympanic cavity and eustachian tube are derived from the first pharyngeal pouch (a cavity lined by endoderm). The distal part of the cleft, the tubotympanic recess, widens to create the tympanic cavity. The proximal part of the cleft remains narrow and creates the eustachian tube. The bones of the middle ear, the ossicles, derive from the cartilages of the pharyngeal arches. The malleus and incus derive from the cartilage of the first pharyngeal arch, whereas the stapes derives from the cartilage of the second pharyngeal arch.
Human embryonic development | Middle ear
Diagnosis is often confirmed by several abnormalities of skeletal origin. There is a sequential order of findings, according to Cormode et al., which initiate in abnormal cartilage calcification and later brachytelephalangism. The uniqueness of brachytelephalangy in KS results in distinctively broadened and shortened first through fourth distal phalanges, while the fifth distal phalanx bone remains unaffected. Radiography also reveals several skeletal anomalies including facial hypoplasia resulting in underdevelopment of the nasal bridge with noticeably diminished alae nasi. In addition to distinguishable facial features, patients generally demonstrate shorter than average stature and general mild developmental delay.
Keutel syndrome | Skeletal effects
It is occupied by the base of the stapes, the circumference of which is fixed by the annular ligament to the margin of the foramen.
Oval window | Introduction
The right lamina of the sixth thoracic vertebra of MH1 presents a penetrating bone tumour, probably a benign osteoid osteoma. The lesion penetrates deep and is wide, and was still active at the time of death. It did not penetrate the neural canal so it probably did not cause any neurological complications, and there is no evidence of scoliosis (abnormal curving of the spine). It may have affected movement of the shoulder blade and the upper right quadrant of the back, perhaps causing acute or chronic pain, muscular disturbances, or muscle spasms. Given "A. sediba" may have required climbing ability, the lesion's position near the insertion for the trapezius, erector spinae, and rhomboid major muscles may have limited normal movement patterns.
Australopithecus sediba | Pathology
Comparisons have shown stapedotomy to yield either as good or better results than stapedectomy (measured by hearing improvement and reduction in the air-bone hearing gap, and especially at higher sound frequencies), and to be less prone to complications. In particular, stapedotomy procedure greatly reduces the chance of a perilymph fistula (leakage of cochlear fluid). Stapedotomy, like stapedectomy, can be successful in the presence of sclerotic adhesions (tissue growths abnormally linking the bones to the tympanic cavity), provided the adhesions are removed during surgery. However, the adhesions may recur over time. The stapedotomy method is not applicable in those relatively rare cases that involve scleroris of the entire ossicular chain.
Stapedectomy | Stapedectomy vs. stapedotomy
The outer apical margin is curved; less than 2 times the length of its pedicel. Placodeal sensillae are present through F5–F13. The pronotum has a distinct plate; its is 1.7 times longer than it is high. The lateral surface of the pronotum is pubescent. The mesoscutum is 1.1 times longer than wide. The median mesoscutal impression is invisible. Scutellar foveae are shallow, forming a transverse depression. The mesopleuron exhibits a longitudinal impression running on its posterior half. The area surrounding this impression almost is completely smooth. The mesopleural triangle is not impressed basally, while being pubescent. The metascutellum is constricted medially.
Paraulax ronquisti | Male
Indeed, for the same quantity of bone, different mechanically resistant bone structures may exist (few large trabeculae or numerous thin trabeculae that are mechanically stronger). Actually, bone loss is often accompanied by a deterioration of bone architecture, resulted in a decreased number of trabeculae, increased inter-trabecular distances, and a loss connectivity of the trabecular meshwork. Moreover, reduction of cortical bone thickness and increased porosity accompany trabecular bone loss, and in particular promote the fragility of the femoral neck. Osteoporotic bone is called "porous".
Trabecular bone score | Need for a marker of microarchitecture
The occurrence of a prominent mastoid process tends to push the concha forward, which extends the pinna (external ear) away from the side of the head. The external ear is mounted upon the bony base of the underlying temporal bone, therefore, anomalies and asymmetries of the skeletal shape can cause either pinna, or both pinnae, to become prominent. In relation to the protruding mastoid process, the most recognizable skeletal anomaly is the change in the position and in the projection of the pinna, as associated with non-synostotic plagiocephaly (the positional flattening of the side of the head, not caused by the inappropriate union of two bones).
Otoplasty | Auricular prominence
Persistence of the foramen tympanicum may also predispose the individual to the spread of infection or tumor from the external auditory canal to the infratemporal fossa or vice versa. It is associated with herniation of soft tissues from the temporomandibular joint into the external auditory meatus, and with formation of fistula between the parotid gland and the external auditory canal. During arthroscopy of the temporomandibular joint, the endoscope may inadvertently pass into the joint via the foramen, with resulting damage.
Foramen tympanicum | Clinical relevance
Skull material is very limited for "Nundasuchus"; only a right lower jaw and a right pterygoid bone (which formed part of the roof of the mouth) were preserved in the holotype. However, even these fragments are informative. The pterygoid is convex when seen from above and concave from below. This ventral (lower) concavity manifests in the form of a deep depression bounded by posterior (rear) and medial (inner) ridges. The portion of the pterygoid which would have been positioned along the midline of the palate is unusual compared to other archosaurs due to possessing teeth. These teeth were small and rounded, placed in three rows parallel to the midline of the mouth.
Nundasuchus | Skull
The brilliant intuitions of D'Arcy Thompson are now accepted by all: the shape that organs (including cancer) and organisms take depends on the variations in time and space of the mechanical properties of the tissues. But he describes, without making any assumptions about why and how. J Wolff described the histological variations of the bone according to the load which weighs on him. This is well known to thoracic surgeons: a vein removed to bypass a coronary artery and grafted into the artery position changes histology and becomes an artery due to this new pressure regime.
Physical oncology | The big ancestors and the dust under the carpet