The median eminence : an electron microscopic study with special reference to gonadotropin release in the rat

Adaptation of an organism to changes in the external and internal environment is in vertebrates brought about by two more or less separate integrative systems: the nervous system and the endocrine system. The nervous system is primarily equipped for rapid and short lived responses, the endocrine system for slower but longer lasting ones. The cells of nervous system and endocrine system have many features in common but they differ, apart from rapidity and duration of the effects exerted, in the way they achieve "privacy" (Wurtman, 1970) in their intercellular conununication. In the nervous system "privacy" is attained primarily by anatomical means whereas chemical messengers, operating over a long distance, are particularly used in the endocrine system. In the nervous system, neurons are the cells adapted for reception, integration and rapid transmission of information. Transmission occurs along dendrites and axons, which are elongated parts of the neurons themselves, and from one cell to another at morphologically identifiable sites of contact, the synapses. Transmission is mediated by a limited number of substances, neurotransmitters, which are released extremely close to receptors of the affected cells

Transfer of lumbosacral load to iliac bones and legs Part 2: Loading of the sacroiliac joints when lifting in a stooped posture

We developed a biomechanical model of load transfer by the sacroiliac joints in relation to posture. A description is given of two ways in which the transfer of lumbar load to the pelvis in a stooped posture can take place. One way concerns ligament and muscle forces that act on the sacrum, raising the tendency of the sacrum to flex in relation to the hip bones. The other refers to ligament and muscle forces acting on the iliac crests, raising the tendency of the sacrum to shift in caudal direction in relation to the hip bones. Both loading modes deal with the self-bracing mechanism that comes into action to prevent shear in the sacroiliac joints. When a person is lifting a load while in a stooped posture, the force raised by gravity acting in a plane perpendicular to the spine and the sacrum becomes of interest. In this situation a belt such as used by weight lifters may contribute to the stability of the sacroiliac joints. Verification of the biomechanical model is based on anatomical studies and on load application to human specimens. Magnetic resonance imaging pictures have been taken to verify geometry in vivo

Fascial deformation in the lateral elbow region: A conceptual approach

Abstract In embalmed preparations, the antebrachial fascia in the lateral elbow region is shown to be deformed by load application to the triceps muscle. From this fascia, muscles arise which are primarily concerned with the extension of wrist and fingers. In the case of lateral epicondylitis (tennis elbow), the superficial site of attachment of these extensors at the lateral epicondyle is extremely painful. Triceps training may help to diminish (or prevent) this pain by altering the forces acting at the lateral epicondyle

The surgical anatomy of the superior gluteal nerve and anatomical radiologic bases of the direct lateral approach to the hip

In view of the increasing popularity of the direct lateral approach to the hip joint for hemi- or total hip arthroplasty, the location of the superior gluteal nerve (SGN) was studied. This nerve is in danger when using a transgluteal incision. In 20 embalmed specimens the relation of the SGN to the tip of the greater trochanter (TT) was studied as well as the relation to the iliac crest. For this purpose macroscopy, microscopy and CT were used. In 13 hips a so-called most inferior branch was found at an average of 1 cm distal to the inferior branch, the main trunk of the nerve. There was substantial variation in the course of both the inferior and the most inferior branch of the SGN. In order to prevent nerve damage, proximal extension of the transgluteal incision should be limited to 3 cm cranial to TT. Furthermore the incision has to be confined to the distal one third of the distance TT-iliac crest. In tall people extra care should be taken

Understanding peripartum pelvic pain: Implications of a patient survey

Study Design. An analysis was made of the self-reported medical histories of patients with peripartum pelvic pain. Objectives. To compile an inventory of the disabilities of patients with peripartum pelvic pain, analyze factors associated with the risk for development of the disease, and to formulate a hypothesis on pathogenesis and specific preventive and therapeutic measures. Summary of Background Data. Pregnancy is an important risk factor for development of chronic low back pain. Understanding the pathogenesis of pelvic and low back pain during pregnancy and delivery could be useful in understanding and managing nonspecific low back pain. Methods. By means of a questionnaire, background data were collected among patients of the Dutch Association for Patients With Pelvic Complaints in Relation to Symphysiolysis. Results were compared with the general population. Subgroups were compared with each other. Results. Peripartum pelvic pain seriously interferes with many activities of daily living such us standing, walking, sitting, and all other activities in which the pelvis is involved. Most patients experience a relapse around menstruation and during a subsequent pregnancy. Occurrence of peripartum pelvic pain was associated with twin pregnancy, first pregnancy, higher ago at first pregnancy, larger weight of the baby, forceps or vacuum extraction, fundus expression, and a flexed position of the woman during childbirth; a negative association was observed with cesarean section. Conclusions. It is hypothesized that peripartum pelvic pain is caused by strain of ligaments in the pelvis and lower spine resulting from a combination of damage to ligaments (recently or in the past), hormonal effects, muscle weakness, and the weight of the fetus

Oblique abdominal muscle activity in standing and in sitting on hard and soft seats

The activity of the oblique abdominal muscles was investigated with the trunk in unconstrained, symmetrical and static postures. Electromyographic recordings in six healthy subjects revealed that in all subjects the activity of both the internal and the external obliques is significantly higher in unconstrained standing than in supine posture. Activity of the internal oblique was higher than that of the external oblique abdominal. The sacrospinal, gluteus maximus and biceps femoris muscles showed practically no activity in unconstrained erect posture. During unconstrained sitting both oblique abdominals are active. In most subjects the activity of the oblique abdominals was significantly smaller when sitting on a soft car seat than when sitting on an office chair with a hard seat. The possibility is discussed that contraction of the oblique abdominals in unconstrained standing and sitting may help in stabilizing the basis of the spine and particularly the sacroiliac joints. During standing and sitting the oblique abdominal muscles apparently have a significant role in sustaining gravity loads

The sacroiliac part of the iliolumbar ligament

The iliolumbar ligament has been described as the most important ligament for restraining movement at the lumbosacral junction. In addition, it may play an important role in restraining movement in the sacroiliac joints. To help understand its presumed restraining effect, the anatomy of the ligament and its orientation with respect to the sacroiliac joints were studied in 17 cadavers. Specific dissection showed the existence of several distinct parts of the iliolumbar ligament, among which is a sacroiliac part. This sacroiliac part originates on the sacrum and blends with the interosseous sacroiliac ligaments. Together with the ventral part of the iliolumbar ligament it inserts on the medial part of the iliac crest, separate from the interosseous sacroiliac ligaments. Its existence is verified by magnetic resonance imaging and by cryosectioning of the pelvis in the coronal and transverse plane. Fibre direction, length, width, thickness and orientation of the sacroiliac part of the iliolumbar ligament are described. It is mainly oriented in the coronal plane, perpendicular to the sacroiliac joint. The existence of this sacroiliac part of the iliolumbar ligament supports the assumption that the iliolumbar ligament has a direct restraining effect on movement in the sacroiliac joints

Mechanical tension in the median nerve: The effects of joint positions

Stretch tests are attractive in the diagnosis of nerve root or peripheral nerve lesion. Interpretation of the test results is often difficult since the distribution of tensile forces along the nerve caused by the test manoeuvre is not known. In this study the effect on median nerve tension of 22 positions of the arm was measured with ‘buckle’ force transducers. With the elbow in full extension and the hand in neutral position, altering the position of the shoulder significantly influenced tension in the proximal part of the median nerve; tension in the distal part was not influenced. With the shoulder in 90 ° abduction, dorsiflexion of the hand combined with an extended elbow resulted in an increased tension in both distal and proximal parts of the median nerve. Dorsiflexion of the hand combined with flexion of the elbow caused an increase in tension only in the distal part. At all sites of the median nerve the median nerve upper limb tension test caused a significantly higher tension than the radial and ulnar nerve upper limb tension tests. This study provides insight in the normal distribution of tensile forces along the median nerve and can have clinical consequences. For differentiating nerve root from peripheral nerve lesions a specific provocative tension test for the median nerve is advocated. The results of this study provide a theoretical basis for differentiating between lesions in the proximal and distal parts of the median nerve