Striated muscles of the mystacial region of the common albino mouse have been described. They were divided into two categories: extrinsic and intrinsic. The four extrinsic muscles (m. levator labii superioris, m. maxillolabialis, m. transversus nasi, m. nasalis) belong to the facial muscles. They originate on the skull and insert into the corium between the mystacial vibrissae. Their contraction moves the whole mystacial region in directions dependent on their origins. Intrinsic (follicular) muscles are associated solely with the vibrissal follicles and have no bony attachment. They were found around follicles alpha, beta, gamma, delta, around all follicles of rows A and B, and around the first six follicles of rows C, D and E. The form of the follicular muscle is a sling connecting two adjacent follicles of the same row. The arc of the sling surrounds the inferior part of the rostral follicle and the two extremities insert to the conical body of the caudal follicle and to the neighbouring corium. They are the protractors of the vibrissae. The inferior parts of the vibrissal follicles of a given row are fixed in a fibrous band which inserts in the anterior part of the muzzle. It is proposed that these bands become stretched during the protraction of vibrissae and contract, by their elasticity, immediately upon the end of the follicular muscles' contraction, executing the fast return of vibrissae to their resting, retracted position.
Contradictory opinions are found in the literature concerning the precise anatomy and role of the inferior laryngeal nerve, the terminal portion of the recurrent laryngeal nerve. Moreover, operative damage to this nerve beyond the thyroid area is seldom described. Twenty-one human larynges were dissected to give a precise description of the inferior laryngeal nerve and to draw attention to the risks of injury to the nerve during specific laryngological operations. In contrast with the varied descriptions found in the literature, only small variations in the terminal branching of the nerve were found. The nerve divides generally extralaryngeally into two branches: a motor, anterior one, innervating the intrinsic laryngeal musculature (except the cricothyroid muscle), and a sensory, posterior one, forming Galen's anastomosis. The anterior branch of the nerve is particularly susceptible to damage just behind the cricothyroid joint; two of its terminal rami, supplying respectively the interarytenoid and thyro-arytenoid muscles, incur potential risks of injury during endoscopic CO2 laser surgery.
The investigators studied the surgical anatomy of the main structures involved in the mobilization of the rectum (Denonvilliers' fascia, mesorectum, middle rectal artery, superior and inferior hypogastric plexuses).The study was carried out on 20 cadavers (17 unembalmed and 3 embalmed). To study Denonvilliers' fascia, ten embryos and fetuses (11 mm to 80 mm CRL) were also examined.Denonvilliers' fascia originates from the fusion of the primary pouch of Douglas. The two leaves making up this structure are easily separated. The mesorectum surrounds the rectum on three sides; it is easily separated from the presacral fascia and its connective tissue is bordered by a thin membrane. The middle rectal artery varies in appearance rate, origin, size, distribution and anastomosis. It runs under the lateral ligament and also sends branches to the genital apparatus. Of the two hypogastric plexuses, the inferior is the most difficult one to identify. Its superior branches extend to the rectum, and the inferior ones to the genital apparatus. Because the anterior part contains the parasympathetic nerves and the middle rectal artery, this region is at major risk during surgical dissection.A sound understanding of the surgical anatomy of the rectum enables the surgeon to perform a more correct and reasonable procedure in terms of both the extent of surgical treatment and the preservation of important anatomical structures.
The establishment of certain patterns of mystacial vibrlssae in mice has been the aim of an extensive breeding program carried on in this laboratory since 1977. In a companion paper we have reported on variations in this pattern in an outbred population of ICR mice. Starting with 21 ICR animals we bred, mostly by brother-sister mating, for 13 bilaterally symmetric patterns of mystacial vibrlssae characterized by the presence (or absence) of supernumerary whiskers (SWs). The strains are classified as follows: I, a mouse strain with the standard pattern; II, eight strains bred for the occurrence of SWs at a given site or sites; and III, four mouse strains bred for a maximal number of SWs in different regions of the whiskerpad. Commonly, SWs occur in regions that coincide with the zones of mergence between the three facial processes except for two class II strains in which we bred for SWs in the "straddler" row of vibrissae, and for one class III strain, In which we cultivated the tendency (that appeared late in our program) to have SWs at the crest of a facial process. For classes I and II we analyzed the results for about 18 generations in terms of "Improvement," meaning an increase in the percentages of animals with the desired phenotype together with a decreased frequency of undesired SWs. For class III, success in breeding meant the increase of the mean number of the desired SWs. All results led to the same conclusion: there is a genetic basis for the occurrence of SWs. The side preference of a particular SW is not strain dependent. It disappears in those class I and II strains in which almost 100% of animals obtained the desired phenotype. The increase in number of SWs in one zone of mergence does not depend on the presence of SWs in the other. Where tested, we almost always found a representation of an SW in a topologically equivalent location within the "barrelfield" area of the somatosensory cerebral cortex. Except for some diseases early in the breeding program, and some side effects of inbreeding that were eliminated, the population was without obvious defects. Where tested, there was no correlation between the occurrence of SWs and sex. The observed variations in pattern of mystacial vibrlssae and their genetic background led us to propose a morphogenetic model for the formation of the pattern of mystacial vibrlssae.
