Embryonic anastomosis between hypoglossal nerves.

This article presents two cases of anastomosis of hypoglossal nerves in the suprahyoid region in human embryos of CR length 10.75 and 17.5 mm. This variation was studied in two human specimens at this stage of development and compared with the normal arrangement of the hypoglossal nerves in embryos at the same stage. The anastomotic branches were of similar caliber to the main trunks. In both cases the anastomosis was located dorsal to the origin of the geniohyoid muscles and caudal to the genioglossus muscles, lying transversally over the cranial face of the body of the hyoid bone anlage. The anastomosis formed a suprahyoid nerve chiasm on the midline in the embryo of 10.75 mm CR length.

Axillary arch: potential cause of neurovascular compression syndrome.

During routine bilateral dissection of 64 upper limbs in 32 adult human cadavers, four cases of an axillary arch, a muscular anomaly, were found. In one case, the axillary arch presented on both sides and in two cases it presented unilaterally on the right side. The innervation and relationships of the axillary arches are reported and the surgical significance of the anomaly is discussed.

Cardiac developmental onomatology: the real heart of the matter.

There has been much controversy regarding Cardiac Embryology since the 19th Century; this has brought up contradictions over many studies on Cardiac Development, and stems mainly from semantic differences rather than from scientific observations. In 1998, FCAT published the 1st Edition of Terminologia Anatomica, which did not include Terminologia Embryologica, and to this day, we do not have a thorough compilation of Terminology related to Cardiac Development (O'Rahilly and Müller 1996). In the present study we have reviewed the literature from the 19th and 20th Centuries gathering the terms proposed by those scientists who influenced Prenatal Cardiac Terminology. Our aim is to bring to the attention of clinicians and researchers of cardiac morphogenesis the need to undertake a reform of the Developmental Cardiac Terminology. We believe an International Consensus on the terminology to be used during the developmental stages is urgent; it should be meaningful both to the experimental embryologist and to the cardiologist, without being ambiguous or controversial. We must not forget that a terminology is of value only when it is properly used.

The course of the buccal nerve: relationships with the temporalis muscle during the prenatal period.

The aim of this study was to describe the course of the buccal nerve and its relationships with the temporalis muscle during the prenatal period. Serial sections of 90 human fetal specimens ranging from 9 to 17 wk development were studied by light microscopy. Each fetal specimen was studied on both right and left sides, making a total of 180 cases for study. A 3-D reconstruction of the region analysed in one of the specimens was made. In 89 cases the buccal nerve was located medial to the temporalis muscle; in 73 cases it penetrated the muscle; in 15 cases it lay in a canal formed by the muscle fibres and was covered by fascia, and finally, in 3 cases it was a branch of the inferior alveolar nerve. The study has revealed that in a large number of cases the buccal nerve maintains an intimate association with the temporalis muscle.

[Past and present of branchial arches]. / Pasado y presente de llos arcos branquiales.

The author effects a descriptive analysis of the different glandular thyroid stage, especially of side sketches, that taking as a basis our observations, we consider and demonstrate that they are originated only starting from the fourth bursae, because the parathyroids glands are ectodermic deriiated proceeding from the epicardic branchial placode, situated on the dorsal surfaces of the fourth epic blastic sulcus, both approaches opposite to classically accepted.

Development of the human elbow joint.

Many studies have been published on the development of the human elbow joint, but authors disagree on its morphogenetic timetable. Most discrepancies center on the cavitation of the elbow joint (including the humeroradial, humeroulnar, and superior radioulnar joints), and the organization of the tunnel of the ulnar nerve. We summarize our observations on the development of the elbow joint in 49 serially sectioned human embryonic (n = 28) and fetal (n = 21) upper limbs. During week 12, ossification begins in the epiphyses of the elements comprising the elbow joint. At the end of the embryonic period, the shallow groove between the posterior aspect of the medial epicondyle and the olecranon process, begins to be visible. The elbow joint cavity appears in O'Rahilly stage 21 (51 days) at the level of the humeroulnar and humeroradial interzones. Formation of the cavity begins at the medialmost portion of the humeroradial interzone and the lateralmost portion of the humeroulnar interzone. The annular ligament begins to develop in O'Rahilly stage 21 (51 days), and the superior radioulnar joint cavity appears between this ligament and the lateral aspect of the head of the radius during O'Rahilly stage 23 (56 days). We established the morphogenetic timetable of the human elbow joint.

Unusual variation of a third head of the biceps brachii muscle.

A human cadaver was studied which presented a biceps brachii with three heads of origin in the left arm. The third or humeral head presented an unique area of insertion into the bicipital aponeurosis (lacertus fibrosus).

Development of the human temporomandibular joint.

A great deal of research has been published on the development of the human temporomandibularjoint (TMJ). However, there is some discordance about its morphological timing. The most controversial aspects concern the moment of the initial organization of the condyle and the squamous part of the temporal bone, the articular disc and capsule and also the cavitation and onset of condylar chondrogenesis. Serial sections of 70 human specimens between weeks 7 and 17 of development were studied by optical microscopy (25 embryos and 45 fetuses). All specimens were obtained from collections of the Institute of Embryology of the Complutense University of Madrid and the Department of Morphological Sciences of the University of Granada. Three phases in the development of the TMJ were identified. The first is the blastematic stage (weeks 7-8 of development), which corresponds with the onset of the organization of the condyle and the articular disc and capsule. During week 8 intramembranous ossification of the temporal squamous bone begins. The second stage is the cavitation stage (weeks 9-11 of development), corresponding to the initial formation of the inferior joint cavity (week 9) and the start condylar chondrogenesis. Week 11 marks the initiation of organization of the superior joint cavity. And the third stage is the maturation stage (after week 12 of development). This work establishes three phases in TMJ development: 1) the blastematic stage (weeks 7-8 of development); 2) the cavitation stage (weeks 9-11 of development); and 3) the maturation stage (after week 12 of development). This study identifies the critical period of TMJ morphogenesis as occurring between weeks 7 and 11 of development.

The vascular relationship between the temporomandibular joint and the middle ear in the human fetus.

PURPOSE: The aim of this work was to clarify the vascular relationships between the middle ear and the temporomandibular joint region during human fetal development. MATERIALS AND METHODS: Light microscopic studies were done on 40 human fetuses from 72 mm crown-rump length (C-R) to 150 mm C-R, which were stained by various methods. Five human fetuses were dissected. Natural latex with industrial coloring was injected through the external carotid artery. All specimens were dissected bilaterally. RESULTS: The limits of the retroarticular region and the fetal tympanosquamosal fissure are shown. The anterior tympanic artery has a variable origin. In most cases, it originates from the maxillary artery; in other cases it originates from the superficial temporal artery or the bifurcation of the external carotid artery. On its way through the retroarticular region, it gives branches to the posterior part of the temporomandibular joint. It progresses along the most lateral part of the tympanosquamosal fissure, dividing into three branches that extend throughout the middle ear. A number of venous spaces in the retroarticular region that constitute the retrodiscal venous plexus. Small venous vessels along the fetal tympanosquamosal fissure accompany the anterior tympanic artery and drain into the retrodiscal venous plexus. CONCLUSIONS: During human fetal development, there is a wide connection across the tympanosquamosal fissure between the middle ear and the temporomandibular joint region. The anterior tympanic artery and its branches, as well as small venous vessels that are connected with the retrodiscal venous plexus, extend along the most lateral part of the fissure.

Anatomical considerations on the discomalleolar ligament.

A study was carried out on the discomalleolar ligament by dissection of adult human cadavers. The ligament corresponds to the most internal portion of the superior lamina of the temporomandibular joint capsule. It extends from the posterointernal portion of the temporomandibular joint disc, penetrates the petrotympanic fissure and reaches the malleus of the middle ear. Because of its morphology and anatomical arrangement the discomalleolar ligament should be considered as an intrinsic ligament of the temporomandibular joint and distinguished from the tympanic portion of the sphenomandibular ligament (anterior ligament of the malleus).

Anatomic relationships of the orbital muscle of Müller in human fetuses.

A study was carried out in twenty human fetuses on the relationships of the orbital muscle of Müller. This muscle forms a lamina of smooth muscle fibres that cover the inferior orbital fissure. The latter is very wide during the fetal period because ossification of the bones that delimit this region is still incomplete. Some fibres of the orbital muscle extend along the superior orbital fissure under the inferior ophthalmic vein and the lower wall or floor of the cavernous sinus. This association suggests a possible influence on autonomically mediated vascular dynamics.

Development of Meckel's cartilage in the symphyseal region in man.

BACKGROUND: The aim of this work is to clarify the aspects which are at present most controversial about the development of the anterior segments of Meckel's cartilage, such as the role of and determination of the area that is incorporated in the development of the human mandible. METHODS: Light microscope studies were done on 25 embryos and human fetuses from the collection of the Institute of Embryology at the University Complutense of Madrid and the Department of Morphological Science from the University of Granada. Specimen length was between 18 and 125 mm crown-rump. RESULTS: During the embryonic period, Meckel's cartilages were placed in the midline of the mandibular arch but fusion was not observed between them. Ossification of Meckel's cartilage begins at the end of the embryonic period and is completed in the fetal period and the portion that participates in mandibular formation is determined. This segment extends from the mental foramen to near the midline of the mandible. In this region, on the dorsal surface of the symphysis, cartilaginous nodules that originate from Meckel's cartilage are isolated. CONCLUSIONS: The ventral portions of Meckel's cartilage do not fuse in the midline of the mandibular arch. These present endo- and perichondral ossification and the section from the mental foramen to near the midline (mandibular symphysis) participates in mandibular formation. The ventral ends of Meckel's cartilage, i.e., the ends nearest the midline, do not ossify and remain isolated on the dorsal surface of the fetal mandibular symphysis.

Development of the human knee joint ligaments.

BACKGROUND: Many studies have been published on the development of the human knee joint, but scant attention has been given to the development of the knee joint ligaments. The only elements that have received much attention are the cruciate ligaments and their relationships with the synovial membrane. METHODS: We summarize our observations on the development of the knee joint ligaments in 50 serially sectioned human embryonic and fetal lower limbs (26 embryos and 24 fetuses). RESULTS: The patellar ligament begins to form in O'Rahilly stage 20, with the muscle fibers of the quadriceps muscle being attached inferiorly to the tibial tuberosity. The cruciate ligaments (beginning with the posterior) arise from the articular interzone in O'Rahilly stage 21. Subsequently, with the organization of the Wrisberg's meniscofemoral ligament, in week 10 of development, the cruciate ligament system is completed. The lateral collateral ligament begins to form in O'Rahilly stage 23, and from its first appearance it is independent of the knee joint capsule. At this time, development of the tendon of the popliteus muscle begins. The medial collateral ligament begins to develop in week 9 of development as a condensation of the joint capsule. Two weeks later, the intra-articular pad of fat begins to form from mesenchymal tissue below the patella and between the cruciate and the patellar ligaments. With the organization of the suprapatellar bursa in week 14 of development, knee joint development is complete. CONCLUSIONS: The morphogenetic time table of the knee joint ligaments was established.

Development of the human knee joint.

BACKGROUND: Many studies have been published on the development of the human knee joint, but different investigators disagree on its morphogenetic time table. Most discrepancies center on the cavitation of the knee joint and the participation of the superior tibiofibular joint in the joint knee system. METHODS: We summarize our observations of the development of the knee joint in 50 serially sectioned human embryonic and fetal lower limbs (26 embryos and 24 fetuses). RESULTS: The epiphysis of the femur and tibia become condryfied from O'Rahilly stage 18, and ossification begins during the 13th week of development. The patella appears as a dense blastema during O'Rahilly stage 19, becomes condryfied during O'Rahilly stage 22, and begins its ossification during the 14th week of development. The knee joint cavity appears during O'Rahilly stage 22, initially as the femoropatellar joint. This process begins at the periphery of the articular interzone. The superior tibiofibular joint communicates with the lateral meniscotibial joint between 10 and 11 weeks of development and becomes separated from the 13 week on. The menisci arise from the eccentric portions of the articular interzone during O'Rahilly stage 22; however, until week 9 of development, they are not easily distinguishable. CONCLUSIONS: We establish the morphogenetic time table of the human knee joint.

A duplicated Meckel's cartilage in a human fetus.

An exceptional case of a duplicate Meckel's cartilage in a human fetus, with a C-R length of 57 mm, is studied. Another small cartilage, isolated from Meckel's, of rounded morphology, was observed in a small region between the temporomandibular joint and the middle ear. This cartilage was only present on the right side.

Anterior tympanic artery: course, ramification and relationship with the temporomandibular joint.

The anterior tympanic artery, a branch of the maxillary artery, ascends through the retroarticular region dividing into anterior branches that spread through the posterior part of the temporomandibular joint, and posterior branches that contribute to the vascularization of the external acoustic meatus and the tympanic cavity. The arrangement of the anterior tympanic artery was studied bilaterally in 18 adult cadavers. In some cases, the anterior tympanic artery branches off from the superficial temporal artery. The relationships of the anterior tympanic artery with the posterior part of the temporomandibular joint were analyzed.