Biomedical subjects

I Kjaer

Publications and source records attributed to I Kjaer.

123 records · Page 7Linked to original sources

PubMedDate not supplied

Prenatal development of the human osseous temporomandibular region.

The purpose of the present study was to describe the sequence in which the lateral cranial base ossifies, particularly in the temporomandibular region. Charting the ossification sequence in the lateral normal cranial base is important for evaluating deviations in pre- and postnatal temporomandibular development. The material consisted of 74 normal human fetuses (crown-rump length = 25-228 mm). The period investigated covers the interval from the early start of ossification at 8 weeks gestational age to the occurrence of a complex ossification pattern at 21 weeks gestational age. Ossification of the cranial base in the sagittal plane is assessed mainly by radiography. The findings are confirmed by marking structures before X-ray, devisceration, and histology. This investigation confirms previous findings concerning regularity in cranial ossification sequences. In addition, the ossification in the temporomandibular region is divided into eight developmental stages according to the pattern of ossification. Thus, a developmental reference material has been established based on the following sequence in ossification of the cranial base (including the mandible and the zygomatic bone): mandible, maxilla, medial pterygoid process of the sphenoid bone, the horizontal part of the frontal bone, the zygomatic bone, the zygomatic arch of the temporal bone, the squamous part of the temporal bone and the occipital squama followed by ossification in the greater wing of the sphenoid bone, the tympanic ring, the occipital condyle, the minor wing of the sphenoid bone (anterior clinoid process), and the lateral part of the postsphenoid bone.(ABSTRACT TRUNCATED AT 250 WORDS)

Embryonic and Fetal Development↗

PubMedDate not supplied

Cranial base and vertebral column in human anencephalic fetuses.

The purpose of the present study was to investigate the axial skeleton related to the notochord in human anencephalic fetuses in order to elucidate the pathogenesis. Fifteen second trimester fetuses were examined. The spine and the cranial base were dissected and radiographed. Comparison with normal fetuses was performed. Two patterns of abnormal ossification were seen. Anencephalic cases without cervical rachischisis (Groups I and II) differed markedly from cases with cervical rachischisis (Group III). Morphological characteristics, such as bilateral narrowing of the basilar part of the occipital bone combined with normal cranio-caudal dimension, were found in cases without cervical rachischisis. In these cases frontal clefting of vertebral corpora occurred. Caudocranial shortening of the basilar part of the occipital bone was found in cases with cervical rachischisis, where complete median clefting of vertebral corpora also occurred. Because the vertebral corpora and the basilar part of the occipital bone develop around the notochord, which interacts also in the process of neurulation, the defects might indicate a notochordal insufficiency. The study showed that when the initial closure of the neural groove failed, the skeletal deviations were more extensive. The study supports the hypothesis that the notochord is an important clue to an understanding of the pathogenesis in anencephaly.

Anencephaly↗

PubMedDate not supplied

Prenatal sagittal growth of the osseous components of the human palate.

The human osseous palate consists of the palatine processes of the maxillary bone anterior to the transverse palatine suture and the horizontal processes of the palatine bone posterior to the suture. The purpose of the present study was to analyze the sagittal growth of these different bone components bordering the transverse palatine suture. The material comprised radiographs of cranial midsagittal tissue blocks from 44 human fetal specimens obtained by legally approved abortions. Gestational age (GA) ranged from 10 to 26 weeks and crown-rump lengths (CRLs) from 50 to 240 mm. The lengths of the maxillary and palatine components of the hard palate were measured with a digital caliper on 3x-enlarged projections of the radiographs. A significant increase in the lengths of both palatal components occurred during the period investigated. Regression analysis on GA showed a linear course of the growth curve in the period studied and gave indirect evidence of a curvilinear shape in the period preceeding the one studied. Growth rates for the palatal dimensions were found to be proportional to that of CRL. The increase in total length resulted predominantly from an increase in the anteroposterior dimension of the maxillary component.

Cranial Sutures↗

PubMedDate not supplied

The prenatal development of the human nasal and vomeral bones.

The purpose of the present study was to establish normal prenatal development standards for the nasal and vomeral bones, both formed by intramembranous ossification in the membrane covering the cartilaginous nasal capsule. The study is based upon a combination of macroscopic (devisceration and radiography) and microscopic (histology) analyses on 62 normal human fetuses from spontaneous and induced abortions, ranging in gestational age from 9 to 24 weeks, representing crown-rump lengths (CRL) from 33 to 225 mm. Special attention was paid to the onset of bone formation in relation to other maturity aspects and to the growth of the bones. The very first onset of ossification of the vomeral bone is observed as two bilateral ossification centers, prior to nasal bone ossification. Later, the two bilateral ossification centers fuse caudally below the cartilaginous nasal septum, thus changing into a U-shaped bone when observed in the coronal plane. By bony apposition caudally the U-shaped vomer gradually changes into a Y-shape. The nasal bone appears as a thin bony contour ventral to the cartilaginous nasal septum in the sagittal plane, and changes gradually during growth to a wedge-shaped bone. Knowledge of the early development of the internal nose (vomeral bone) and external nose (nasal bone) is significant in understanding mid-face congenital malformations.

Face↗

PubMedDate not supplied

Development of the basilar part of the occipital bone in normal human fetuses.

The present study aims to investigate the normal maturity and growth of the basilar part of the occipital bone evaluated radiographically and histochemically during the first half of prenatal life. The material consisted of cranial bases from 49 normal human fetuses and, in addition, three separate occipital bones deviscerated from normal fetuses. The normal development of the basilar part of the occipital bone was divided into five maturity stages (OB-I to OB-V). Microscopic investigation confirmed the macroscopic findings described. For each stage the ventro-dorsal dimension of the occipital bone component was measured (LEN). The stages of (OB-I to OB-V) were related to gestational age (AGE), crown-rump length (CRL), LEN, and to the length of the humeral bone (HL). Close accordance was registered between OB stages and length values of the basilar part of the occipital bone, LEN, and length of the humeral bone, HL. A highly significant positive correlation was found between LEN and the parameters AGE, CRL, and HL values (P < 0.001). Standards for normal development of the basilar part of the occipital bone are considered important for evaluation of the pathological prenatal development of the cranial base.

Gestational Age↗

PubMedDate not supplied

Ossification of lateral components in the human prenatal cranial base.

The purpose of the present study was to perform a radiographic description of the developing osseous structures in the prenatal human cranial base and to describe the sequence in which these structures ossify. The material consisted of 58 normal human fetuses (crown-rump length (CRL) 26-180 mm). The period investigated covered the time interval from the period before start of ossification at 8 weeks gestational age to occurrence of distinct ossification at 22 weeks gestational age. The osseous structures of 48 cranial bases were identified by radiography, supplemented by inspection of ten deviscerated cranial bases. The time of appearance of ossification of the individual bones was in agreement with former reports. The study showed a remarkable consistency in the sequence of ossification in the lateral part of the cranial base (parasagittal segment, PSS). The development was divided into eight stages. Bilateral agreement in ossification pattern was observed. The ossification pattern in the parasagittal segments of the cranial base was characterized by occurrence of osseous bone structures in the squama regions before occurrence in the cranial base region. It is suggested that a connection exists between the ossification pattern of the cranial base and the developmental pattern of the brain.

Embryonic and Fetal Development↗

PubMedDate not supplied

Ossification sequence of occipital bone and vertebrae in human fetuses.

The aim of this radiographic study of human fetuses was to examine the pattern and sequence of ossification in the occipital bone and the spinal vertebrae. Together with previous studies of ossification of the human fetal basal cranium, this study can serve as a reference for normalcy in future studies of fetuses with neural tube defects and associated pathological development of the axial skeleton. Thirty-nine normal fetuses aborted between 9 and 14 weeks of gestation were examined. Based on the appearance of ossification centers in the bones under study, the fetuses could be grouped in four well-defined developmental stages, which were named occipito-spinal stages I-IV (OS I-IV). The OS stage was closely related to gestational age, crown-rump length, foot length, and degree of ossification in the hands and feet.

Embryonic and Fetal Development↗

PubMedDate not supplied

Changes in human palatine bone location and tongue position during prenatal palatal closure.

Closure of the palatal shelves during normal prenatal palate formation is commonly supposed to be the result of a complex interaction between tissue growth processes and functional factors such as mandibular and tongue movements. The purpose of the present study was to analyze tongue and palatine bone positions during palatal shelf closure. The material consisted of 40 normal human fetuses (CRL 26-57 mm). The series covers the developmental stages in which palatal shelf closure takes place. The spatial relation between the tip of the tongue and the lips was examined by visual inspection, and radiographic/cephalometric methods were used for analyzing palatine bone positions. On axial radiographs of the upper jaws, the angle in the horizontal plane between the vertical plates of the palatine bones was measured. The study revealed that the vertical plates of the palatine bones rotate on their vertical axes during palatal closure, the mean interpalatine angle changing from 23.7 degrees (SD 2.0 degrees) to 13.3 degrees (SD 3.2 degrees), P < 0.001. The rotation of the palatine bones occurred while the cranial base was still unossified. Moreover, the tip of the tongue became visible between the lips immediately after palate closure. In the present study the rotational changes observed in skeletal tissue provided information about soft tissue changes during palatal closure. These normal developmental aspects are discussed in relation to skeletal deviations in congenital cleft palate malformations.

Fetus↗

PubMedDate not supplied

The development and morphology of the incisive fissure and the transverse palatine suture in the human fetal palate.

The incisive fissure and the transverse palatine suture are well known anatomical structures in the human palate. The purpose of the present study was to describe the development and the morphology of the incisive fissure and the transverse palatine suture. Another purpose was to compare the nature of both structures with the aim of elucidating their possible function in the developing facial skeleton. Descriptions of the initial formation, development, and maturation of the incisive fissure and the transverse palatine suture, in combination with a comparison between the suture systems, were not found in the literature. Human fetal material, consisting of a total number of 96 specimens with gestational ages ranging from 9 to 24 weeks, was analyzed macroscopically (radiologically and after devisceration) and microscopically (histologically). The bony maturation of specimens was recorded by relating to the stages of maxillary ossification (MAX), an index for skeletal maturity of the palate. The study revealed pronounced macroscopic and microscopic differences between the incisive fissure and the transverse palatine suture. The transverse palatine suture appears to be a site for anteroposterior growth of the palate. The incisive fissure has a different macroscopic and microscopic appearance and presumably has a function more closely related to the development of the dentition and the anterior part of the maxilla.

Facial Bones↗

PubMedDate not supplied

The adenohypophysis and the cranial base in early human development.

The purpose of the present study is to chart the normal human development of the adenohypophyseal part of the pituitary gland and of the cranial base, with special attention given to the possible presence of pharyngeal remnants of adenohypophyseal tissue. From 31 human embryos and fetuses (7-21 weeks of gestation) midsagittal, paraffin-embedded tissue blocks of the cranial base, including the pituitary gland and the pharyngeal wall, were investigated histologically. The identification of adenohypophyseal tissue included immunohistochemical methods. In early stages, the adenohypophysis of the pituitary gland. From this stage in development adenohypophyseal tissue is not demonstrated pharyngeally. The cartilaginous cranial base is visible in its full antero-posterior extent before ossification starts. Cranio-pharyngeal canals are not registered in the cranial base. This study intends to define a standard for subsequent autopsy descriptions of the pituitary gland region in craniofacial malformations.

Autopsy↗

PubMedDate not supplied

Growth in the lateral part of the human skull during the second trimester.

The aim of the present study was to report dimensional changes in the lateral part of the prenatal human skull during the second trimester. The sample comprised 37 fetuses obtained in connection with requested autopsy. Gestational ages (GA) were available for 27 fetuses, ranging from 13 to 24 weeks. Crown-rump lengths (CRL) of 23 fetuses ranged from 78 to 228 mm. For 21 fetuses both CRL and GA were available. After excision of the midsagittal segment of the skulls by two paramedian sections from the frontal bone to the foramen magnum through the optic foramina, an incision was made through the middle of the occipital squama, bisecting the skull. The present study was based on the skull components of the resulting 74 lateral cranial tissue blocks. The tissue blocks were radiographed with a Hewlett Packard Faxitron unit. Seven reference points were digitized from each film and eight linear dimensions were calculated. Method errors ranged from 0.12 mm to 0.52 mm. The dimensions were related to crown-rump length (CRL) and lateral segment developmental stages (LSS). The increases in the linear dimensions of the anterior part of the lateral skull segments were similar to those found previously for the median skull segment. The dimensions of the anterior part of the lateral skull segments were found to increase by 150% during the second trimester, while those of the posterior part increased by 100% during the same period. Between maturity stages LSS 4 and 5 the dimensions increased by 30-50%, whereas less increase was observed between stages 5, 6, 7, and 8. This reduction was attributed to the progressive ossification of the cranial base. The almost horizontal distance from the mandibular condyle (condylion) to the anterior tympanic ring did not change significantly during the second trimester. Comparison of the bilateral skull segments showed no systematic asymmetry, but a significant individual biological variability in symmetry with standard deviations of 0.7-1.8 mm was found.

Cephalometry↗

PubMedDate not supplied

Human fetal pituitary gland in holoprosencephaly and anencephaly.

The normal prenatal development of the human pituitary gland and the gland-supporting sella turcica has recently been investigated. The sella turcica area constitutes a developmental boundary area in the cranial base. Posterior to the area the cranial base has developed close to the notochord, and anterior to the region the cranial base development is dependent chiefly on neural crest cell migrations. In the present study the sella turcica region was analyzed in two fetuses with holoprosencephaly (cyclopia and median cleft) and four fetuses with anencephaly combined with rachischisis in the neck region (GA 16-20 weeks). The sella turcica region was investigated radiologically and histologically. Adenohypohyseal gland tissue was localized by immunohistochemical hormonal marking. In both types of malformation an open craniopharyngeal canal was seen in the base of the sella turcica with adenohypophyseal glandular tissue located in the sella turcica, in the canal, and in the pharyngeal connective tissue at the external side of the cranial base. In conclusion, severe malformations of the pituitary gland occur in both holoprosencephaly, which is a polytopic field defect located anterior to the sella turcica, and in anencephaly associated with notochordal insufficiency posterior to the sella turcica. This might indicate that the sella turcica area, bounding different developmental fields, is involved in various craniofacial malformations. It is consequently recommended that examination of the pituitary gland should become a part of the routine autopsy of prenatal material when malformations in the face, brain, and cranial base occur.

Anencephaly↗

PubMedDate not supplied

A new craniofacial disorder involving hypertelorism and malformations of external nose, palate and pituitary gland.

The aim of the present study was to describe and pathologically evaluate an apparently unreported craniofacial malformation, based on comparison of the cranial midsagittal components with similar components under normal developmental conditions. A severely malformed fetus with a gestational age of about 17 weeks underwent whole body and special craniofacial radiography. Following autopsy dissection, the midsagittal segment of the cranial base, including the eyes, was radiographed in different projections. Midsagittal tissue blocks were serially sectioned for microscopy. Routine stains and immunohistochemical stains were applied. The face was characterized by hypertelorism, absence of external nose but with open shell-like cavities medio-cranially to the eyes, and by a palate fused in the midline and with extensive bony ridges laterally. There was absence of normal nasal cavities, presence of nasal septum and vomer, normal eyes, and nasal ducts covered with nasal mucosa ending blindly in the cartilage. No olfactory bulbs were found. The palatal ridges consisted of bony tissue. The pituitary gland was severely malformed and consisted solely of adenopituitary gland tissue, located in its full extent in the pharyngeal mucosa. There was no sella turcica. From a pathogenetic point of view, it is suggested that the neural crest cells in the frontonasal region of the crest were reduced in amount or late in migration to the midfacial region compared to the neural crest cells to the maxillary region. Therefore, we believe that the malformations observed in the nasal placodes and in the pituitary placode, combined with abnormal migration or abnormal timing of neural crest cells during the craniofacial development, are important factors behind this disorder.

Brain↗

PubMedDate not supplied

Mandibular movements during elevation and fusion of palatal shelves evaluated from the course of Meckel's cartilage.

The purpose of the present study was to investigate whether the course of Meckel's cartilage could reveal the mandibular movements during the elevation and fusion of the soft tissue palatal shelves. Histological sections, cut serially in the horizontal plane from 64 human mandibles, 16-104 mm CRL, were analyzed. The course of the anterior and medial part of Meckel's cartilage changed markedly during the three palatal stages, i.e., before, during, and after palate formation. The medial part changed during these stages from a straight course through a curled, S-shaped course to a crochet-hook-shaped course. The anterior part of Meckel's cartilage developed from a separation in the symphysis menti region to a fusion and later to a separation again. It is suggested that these changes in the course of Meckel's cartilage are due to different muscle activities. It is supposed that during the palatal developmental stages the activity of the geniohyoid and genioglossus muscles caused the mandibular retraction and the widening of the angulation between the bilateral hemimandibles. The S-shape of Meckel's cartilage is a result of these movements. Later mandibular proclination and narrowing of the bilateral hemimandibles resulted in an anterior mechanical fusion of Meckel's cartilage due to the activity of the mylohyoid muscle. This stage is followed by a retraction and re-widening of the angulation between the bilateral bony components, which disrupts the fusion of Meckel's cartilage in the symphysis menti region. Thus, the course of Meckel's cartilage revealed the mandibular movements in the sagittal and transverse planes during palate formation.

Bone Development↗

PubMedDate not supplied

The association between prenatal sella turcica morphology and notochordal remnants in the dorsum sellae.

The purpose of this study was to describe the location and morphology of notochordal remnants in the cranial base in normal and pathological conditions and to relate these findings to the morphological appearance of the sella turcica. Serially cut sagittal sections of paraffin-embedded sella turcica tissue blocks from 88 normal and pathological fetuses, 13 to 24 weeks of gestation, were examined. Twenty-seven specimens out of 88 had visible notochordal remnants in the cranial base, and these constituted the material available for this study. A straight notochordal course is always seen in normal sella turcica morphology, and a non-straight notochordal course is always seen in malformed sella turcica. Among the fetuses diagnosed at autopsy as "normal fetuses," both normal and pathological findings in the sella turcica regions were observed. The pathological findings were always found in the spontaneously aborted fetuses (five cases). Among the fetuses diagnosed at autopsy as "pathological fetuses," both normal and pathological findings were also observed in the sella region. Our conclusion is that the morphological appearance of the notochordal remnants in the dorsum sellae is associated with the morphology of the sella turcica. These structures ought to be analyzed on larger materials of both normal and pathological fetuses. One of the more obvious perspectives opened up by the present study is the probable disclosure of malformations in spontaneously aborted fetuses without external malformations.

Female↗