Human clay models versus cat dissection: how the similarity between the classroom and the exam affects student performance

This study examined the effect of different anatomic representations on student learning in a human anatomy class studying the muscular system. Specifically, we examined the efficacy of using dissected cats (with and without handouts) compared with clay sculpting of human structures. Ten undergraduate laboratory sections were assigned to three treatment groups: cat dissection only, cat dissection with handouts, and human clay sculpting with handouts. Exams included higher-order questions that presented novel anatomic images and scenarios that the students did not practice in class. The higher-order anatomy exam questions varied the degree to which students in the different treatments had to transform the anatomic representation studied during laboratory activities to match the representation used in the exam questions. In this respect, exam questions manipulated the similarity between the surface features of the anatomic representations used in the classroom versus the exam. When identifying anatomic structures presented in a photograph or diagram, student performance improved significantly when transformation demands decreased, i.e., students in the human clay sculpting treatment group performed best on human anatomy questions and students in the cat dissection treatment group performed better on cat anatomy questions (independent of the use of handouts). There were similar, but nonsignificant, trends when students were asked functional anatomy questions presented in human and cat contexts. On survey questions designed to measure student attitudes about dissection versus nonanimal alternatives, students typically preferred the method used in their treatment group, suggesting that student preference is too fluid to factor into curricular decisions. When designing curricula, instructors must choose anatomic representations that support their course goals. Human representations are most effective when teaching the human muscular system.     

Cat dissection vs. sculpting human structures in clay: an analysis of two approaches to undergraduate human anatomy laboratory education

Many human anatomy courses are taught using cat dissection. Alternatives are available, but information regarding learning outcomes is incomplete. In 2003, approximately 120 undergraduates enrolled in a human anatomy course were assigned to one of two treatment groups. In the control group, students performed cat dissections (emphasizing isolation and identification) of the muscular, digestive, and cardiovascular systems. In the experimental treatment group, students built clay sculptures of each human body system. Student learning was evaluated by using both low- and high-difficulty questions. On pre- and postexperiment control exams, there were no significant differences in student performance. On exams after a cat dissection vs. a human-clay sculpting experience, the students in the human-clay sculpting treatment group scored significantly higher than their classmates in the cat dissection group on both the low- and high-difficulty questions. Student attitudes toward dissection and taking future human anatomy courses were also measured. There were no differences in student attitudes at the beginning of the experiment; afterward, students exposed to a cat dissection experience viewed dissection more favorably than students in the human-clay sculpting treatment group. There were no treatment effects on student willingness to take future human anatomy courses. The experimental design makes it difficult to conclude precisely why students assigned to the human-clay sculpting experience performed better on exams, but as each method was performed in this particular human anatomy course, our data indicate that human-clay sculpting may be a viable alternative to cat dissection in an anatomy course in which the students focus on human anatomy.     

The developing neurovascular anatomy of the embryo: a technique of simultaneous evaluation using fluorescent labeling, confocal microscopy, and three-dimensional reconstruction.

The close spatial relationship between peripheral nerves and blood vessels in the adult is well known. However, evidence supporting the congruent development of these structures in embryos remains anecdotal. Neurovascular relationships also have been shown to be conserved in other vertebrates. This homology suggests that either peripheral nerves or blood vessels, or both, might have fundamental morphogenetic roles during embryologic development. Both peripheral nerves and blood vessels have been independently implicated as etiologic agents in the pathogenesis of congenital disabilities, and several congenital anomalies fit their distribution patterns. This article presents a technique for the simultaneous visualization of peripheral nerves and blood vessels at different stages in the developing embryo. The forelimbs of 310 quail embryos were dissected over a 1-year period. Peripheral nerves were labeled with the neural crest and axon antibody, HNK-1, followed by fluorescein-conjugated secondary antibodies. Blood vessels were labeled by a perfusion technique using the fluorescent dye, dioctadecyl-tetramethylindocarbocyanine. Specimens were processed and imaged in whole-mount with confocal microscopy, and images were reconstructed using three-dimensional modeling software. Both nerves and blood vessels seem to undergo a highly stereotypic sequence of development in the embryonic quail forelimb. Furthermore, the existence of a close spatial relationship between nerves and blood vessels suggests either a high degree of developmental interdependence or shared patterning mechanisms. This technique permits further evaluation of the possible role peripheral nerves and blood vessels might play in the pathogenesis of congenital disabilities and provides a starting point for further studies aimed at elucidating the means by which peripheral nerves and blood vessels are patterned in the forelimb of the avian embryo.     

Comparative study of the autonomic innervation of the mammalian ovary,with particular regard to the follicular system

Summary The autonomic innervation of the ovary was studied in 12 mammalian species utilizing the cholinesterase method in combination with pseudocholinesterase inhibition for the cholinergic component, and glyoxylic acid histochemistry together with fluorometric determination of noradrenaline for the adrenergic component. Ovaries from cow, sheep, cat, and guinea pig were very richly supplied with adrenergic nerves in the cortical stroma, particularly enclosing follicles in various stages of development. In the follicular wall the nerve terminals were located in the theca externa, where they ran parallel to the follicular surface. Numerous adrenergic terminals also surrounded ovarian blood vessels. The adrenergic innervation was of intermediary density in the human ovary and in the pig, dog, cat, and opossum. Ovaries from rabbit, mouse and hamster had a sparse adrenergic nerve supply. The amount of intraovarian adrenergic nerves agreed well with the tissue concentration of noradrenaline in the various species. The cholinergic innervation was generally less well developed, but had the same distribution as the adrenergic system around blood vessels and in the ovarian stroma, including follicular walls.     

Guidelines for the intramuscular positioning of EMG electrodes in the semispinalis capitis and cervicis muscles.

The objective of the study was to establish guidelines for the application of fine-wire or needle electrodes in the semispinalis cervicis and semispinalis capitis muscles.First of all, measured data for the puncture angle and puncture depth of each muscle were determined in CT scans. Using a regression approach, a model relation of these data with the neck circumference was established. This made it possible to accurately determine the puncture angle and puncture depth on the basis of the known neck circumference. In a further step, the neck muscles of seven human cadavers were punctured with wires in order to check the workability of these guidelines. At the same time, the wires' positions in relation to important structures (nerves, vessels) were studied.Both muscles can be punctured with a high degree of reliability. However, when puncturing the semispinalis cervicis muscle, one has to pass through a layer that contains vessels, nevertheless the risk of injury is regarded as very small.The technique enables intramuscular EMG measurements of the two muscles in manifold clinical problems.     

The angiosomes of the mammals and other vertebrates.

This is a comparative study of the vasculature of the integument and underlying deep tissues of a range of mammals and other vertebrates. The investigation was conducted in the pig, monkey, dog, cat, possum, guinea pig, rat, rabbit, duck, and toad. The results from each are compared not only to each other, but also to previously performed human studies. The arterial network of the fresh animal cadaver was injected with a mixture of lead oxide and gelatin. The vascular anatomy of the skin, deep tissues, and individual muscles was defined by dissection, cutaneous perforator counts, photography, and radiography. A similar pilot study of the venous framework was performed in the pig, dog, and rabbit that included maps of the sites and orientations of the valves. The vasculature of the integument and deep tissues was correlated, and we found that we were able to define angiosomes (composite blocks of tissue supplied by the same source vessel) in each animal. Results revealed a marked dissimilarity of the overlying cutaneous vessels in many cases, yet a striking resemblance of the vascular architecture of the deep tissues. The size and density of the cutaneous perforators bore a close relation to the degree of the skin mobility, being large and sparse where the skin was mobile and smaller and more densely grouped where the integument was tethered or fixed. The cutaneous vasculature of the human resembled that of the monkey closely, was similar to that of the dog, cat, and possum, and was dissimilar to that of the pig, rat, guinea pig, and rabbit. Studies of the amphibian and bird bore many resemblances to those of the mammals. They provided basic concepts regarding modification of the animals' vascular anatomy in response to the functional demands of the species. In each animal, the arteries formed an unbroken network throughout the body. This consisted of anatomic territories linked by anastomotic vessels that were usually of reduced caliber. The pattern of the venous system was almost identical. Valved venous territories were linked by avalvular (oscillating) veins. The common denominator in the vascular system is the capillary bed. Conceptually, the anatomic arrangement of the arteries and veins, reproduced in each species, appears to be a sophisticated mechanism to allow equilibration of flow and pressure arriving at and departing from the capillary bed. The angiosome concept is reinforced by the animal studies. Although this investigation is essentially a detailed pilot study, it embraces many animals commonly used for experimentation and provides a reference atlas of their vasculature.(ABSTRACT TRUNCATED AT 400 WORDS)     

Immunohistochemical localization and vascular effects of vasoactive intestinal polypeptide in skeletal muscle of the cat

Summary Scattered vasoactive intestinal polypeptide (VIP) — immunoreactive nerves were found in the striated muscle of the hind limb of the cat, where they usually were associated with small blood vessels. VIP-immunoreactive nerves were also demonstrated in the sciatic nerve; after nerve ligation an abundance of intensely immunoreactive VIP fibres were seen proximal to the ligation. Intraarterial infusion of VIP into the isolated hind limb of the cat had dramatic effects on different sections of the vascular bed. Thus, VIP dilated the resistance vessels leading to a marked increment in muscle blood flow. VIP also relaxed the capacitance vessels causing regional pooling of blood; it increased the capillary surface area available for fluid exchange. Infusions of VIP at a dose of 8 g/min significantly inhibited the vasoconstriction induced by electrical stimulation of the regional sympathetic nerves. It is suggested that local nervous release of VIP may act as a modulator of vascular tone in skeletal muscle.     

Traditional versus computer-based dissections inenhancing learning in a tertiary setting: a student perspective

This paper describes a study investigating both the use and usefulness of laboratory dissections and computer-based dissections, in a tertiary, first-year human biology course. In addition student attitudes to dissection were investigated. Data were collected from enrolled students using quantitative and qualitative survey instruments. Students were questioned about their usage and perceptions of the usefulness of there sources provided, and their attitudes towards the use of dissections for learning in human biology.

The real dissection was used as a learning resource by 80% of the student cohort while only 15% used the computer-based dissection material. In addition 5% of students reported that they did not use either the realdissection material or the computer-based dissection. Of those students who did use the computer-based dissection, two thirds of them found it useful for learning both structure and function of body systems. Of those students who used the real dissection, 72% found it useful for learning structure but only 62% found that it helped in learning function. Of the entire cohort surveyed, 90% agreed that biology students should dissect ananimal to help learn about anatomy. These outcomes reinforce the need to offer a variety of learning experiences that target different styles of learning.     

Myofilament lengths of cat skeletal muscle: theoretical considerations and functional implications.

The cat is the primary model for neuromuscular research. However, sarcomere geometry, in particular thin-myofilament lengths of cat skeletal muscles, is not known, thus preventing adequate muscle modeling on the sarcomere level. The purpose of this study was to determine thin-myofilament lengths in cat skeletal muscle. It was found that average thin-myofilament lengths of cat tibialis anterior muscles (1.12 microns) were larger than the average values reported for frog (approximately 0.95 microns), rat (1.09 microns), and rabbit muscles (1.09 microns) and were smaller than the values reported for monkey (1.16 microns) and human skeletal muscles (1.27 microns). According to the cross-bridge theory of muscular contraction, this result implies that the range of sarcomere length on the ascending limb of the force-length relation for cat muscle is between those of frog, rat, and rabbit on the one side and monkey and human on the other side. It is speculated that the differences in thin-myofilament lengths of different animals are related to the functional demands of these muscles in everyday movement tasks. Isolated experimental observations appear to support this speculation.     

The innervation of the triangular fibrocartilage complex: nitric acid maceration rediscovered

Injury to the triangular fibrocartilage complex (TFCC) is frequently implicated in the etiology of ulnar-sided wrist pain. This study examines the nervous anatomy of the TFCC using a nitric acid maceration technique and attempts to correlate this information with known tear patterns. Ten fresh frozen cadaveric specimens were studied in detail. Gross dissection of each upper-extremity specimen included removal of all flexor and extensor tendons. After identification and labeling with permanent color of the ulnar nerve, dorsal sensory branch of the ulnar nerve, posterior interosseous nerve, anterior interosseous nerve, and median nerve, an en bloc excision of the distal radioulnar region was performed. Digestion of the soft tissue was performed with nitric acid at sequential concentrations of 50% and 33% for 9 of 10 specimens. The digestion was halted by immersing the specimen in a mixture of 10% formaldehyde and 1% glycerine. After removal of bone, the specimens were fixed in paraffin, sectioned, and stained with hematoxylin and eosin. Nine of the 10 specimens were studied microscopically to determine the contribution of the grossly identified nerves to each zone of the triangular fibrocartilage complex as defined by Palmer's classification of acute TFCC tears. The anterior interosseous, median, and superficial radial nerves did not contribute to the innervation of the TFCC. The intraarticular course of the peripheral nerves could not be defined in the one specimen that was not digested with nitric acid. Nitric acid maceration is a rediscovered technique for identifying the nervous anatomy of soft tissues. The study showed that the triangular fibrocartilage complex is innervated by branches of the posterior interosseous, ulnar, and dorsal sensory ulnar nerves in a fairly consistent manner. Improved treatment of TFCC tears may result from an enhanced understanding of the supporting structures' innervation and mechanical function.     

Cancer Borealis Stomatogastric Nervous System Dissection

The stomatogastric ganglion (STG) is an excellent model for studying cellular and network interactions because it contains a relatively small number of cells (approximately 25 in C. borealis) which are well characterized. The cells in the STG exhibit a broad range of outputs and are responsible for the motor actions of the stomach. The stomach contains the gastric mill which breaks down food with three internal teeth, and the pylorus which filters the food before it reaches the midgut. The STG produces two rhythmic outputs to control the gastric mill and pylorus known as central pattern generators (CPGs). Each cell in the STG can participate in one or both of these rhythms. These CPGs allow for the study of neuromodulation, homeostasis, cellular and network variability, network development, and network recovery.The dissection of the stomatogastric nervous system (STNS) from the Jonah crab (Cancer borealis) is done in two parts; the gross and fine dissection. In the gross dissection the entire stomach is dissected from the crab. During the fine dissection the STNS is extracted from the stomach using a dissection microscope and micro-dissection tools (see figure 1). The STNS includes the STG, the oesophageal ganglion (OG), and the commissural ganglia (CoG) as well as the nerves that innervate the stomach muscles. Here, we show how to perform a complete dissection of the STNS in preparation for an electrophysiology experiment where the cells in the STG would be recorded from intracellularly and the peripheral nerves would be used for extracellular recordings. The proper technique for finding the desired nerves is shown as well as our technique of desheathing the ganglion to reveal the somata and neuropil.Open in a separate windowClick here to view.^{(116M, flv)}     

Congenital tibial aplasia with preaxial polydactyly: soft tissue anatomy as a clue to teratogenesis

We performed preoperative arteriography and postamputation dissection on a human limb having complete tibial aplasia and preaxial polydactyly. The tibia was replaced by a tendinous band with an attached connective tissue mass. In the leg, the muscles were normal. Muscles usually arising from the tibia arose from the tendinous band, Intrinsic muscles of the foot were absent where skeletal elements were absent and there were supernumerary muscles where there were supernumerary skeletal elements. The tendinous insertions of the muscles that originated in the leg followed the skeletal pattern of the foot. The nerves were normally distributed with the exception that extra branches innervated the supernumerary toes. Both the anterior tibial and peroneal arteries were smaller than normal and progressively reduced in size as they coursed distally and could not be identified below the ankle. The dorsalis pedis artery was absent. The other arteries of the leg and foot were normal with the exception of extra branches supplying the supernumerary toes. The anatomy indicates that the foot is probably a double posterior duplication. Such a defect implies abnormal specification of the foot pattern due to a prespecification event. The tibial remnant with normal leg soft tissues indicates normal specification of the leg pattern and subsequent interruption of tibial morphogenesis due to a postspecification event. The presence of these different types of malformations in the same limb may seem to be contradictory. We suggest, however, that a single teratogenic event occurring at one moment in time could cause combined pre- and postspecification malformations. We further suggest that a diminished anterior tibial artery reduced the number of vessels available for collateral circulation and thus put the limb at risk for subsequent malformation.     

Male perineogenital anatomy and clinical applications in genital reconstructions and male-to-female sex reassignment surgery

To determine the possibility of providing alternative surgical techniques for male genital reconstruction and for male-to-female sex reassignment surgery, the authors undertook an anatomic investigation of the perineogenital region in male cadavers. Anatomic dissection was performed on 14 male adult human cadavers (fresh and formalin-preserved) studying the main afferent vessels to the anterior perineal region and their mean internal diameters: deep external pudendal artery (0.60 mm), superficial perineal artery (0.50 mm), and funicular artery (0.37 mm). We established their exact topography, together with vascular anatomic variations, main vascular anastomosis circuits (base of the penis, scrotal septum, and perineal fat and lateral spermatic-scrotal fascia), angiosomes, anatomy of the rectovesical septum cavity, and their "critical" key points of dissection. The authors discuss the clinical possibility of elevation of a "tree" of previously described paragenital-genital flaps including mainly those based on the terminal branches of the internal pudendal vascular system, the erectile tissue pedicled flaps, and finally, flaps of the external pudendal system. The authors indicate the concrete vascularization system for each flap.     

Substance P-immunoreactive sensory nerves in the lower respiratory tract of various mammals including man

Summary The occurrence and origin of substance P (SP)-immunoreactive (IR) nerves in the lower respiratory tract was studied by means of immunohistochemistry in the guinea-pig, rat, cat and man. In addition, biopsies from human material were also analysed by radioimmunoassay. SP-IR nerves were seen in four principal locations: 1) under or within the lining epithelium, 2) around blood vessels, 3) within the bronchial smooth muscle layer, and 4) around local tracheobronchial ganglion cells. Ligation experiments combined with capsaicin pretreatments indicated that all SP-IR nerves in the respiratory tract are sensory. The trachea seems to be mainly supplied by the vagal nerves, while intrapulmonary bronchi and blood vessels receive SP-IR nerves of both vagal and non-vagal (spinal) origin. SP-IR nerves were also found in the human bronchi with principally similar location as in the guinea-pig. The levels of SP-IR in the trachea and peripheral bronchi of man were about 3–4 pmol/g, which is in the same range as the content of corresponding tissues from the guinea-pig.In conclusion, the present experimental findings of SP-IR nerves in the lower respiratory tract in both experimental animals and man support the functional evidence for the importance of SP in the vagal and non-vagal (spinal) control of bronchial smooth muscle tone and vascular permeability.     

Peripheral nerve magnetic stimulation: influence of tissue non-homogeneity

Background

Peripheral nerves are situated in a highly non-homogeneous environment, including muscles, bones, blood vessels, etc. Time-varying magnetic field stimulation of the median and ulnar nerves in the carpal region is studied, with special consideration of the influence of non-homogeneities.

Methods

A detailed three-dimensional finite element model (FEM) of the anatomy of the wrist region was built to assess the induced currents distribution by external magnetic stimulation. The electromagnetic field distribution in the non-homogeneous domain was defined as an internal Dirichlet problem using the finite element method. The boundary conditions were obtained by analysis of the vector potential field excited by external current-driven coils.

Results

The results include evaluation and graphical representation of the induced current field distribution at various stimulation coil positions. Comparative study for the real non-homogeneous structure with anisotropic conductivities of the tissues and a mock homogeneous media is also presented. The possibility of achieving selective stimulation of either of the two nerves is assessed.

Conclusion

The model developed could be useful in theoretical prediction of the current distribution in the nerves during diagnostic stimulation and therapeutic procedures involving electromagnetic excitation. The errors in applying homogeneous domain modeling rather than real non-homogeneous biological structures are demonstrated. The practical implications of the applied approach are valid for any arbitrary weakly conductive medium.

     

Neuropeptide Y: presence in sympathetic and parasympathetic innervation of the nasal mucosa

Summary The occurrence of neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP) and peptide histidine isoleucine (PHI) in the sympathetic and parasympathetic innervation of the nasal mucosa was studied in various species including man. A dense network of NPY-immunoreactive (IR) fibres was present around arteries and arterioles in the nasal mucosa of all species studied. NPY was also located in nerves around seromucous glands in pig and guinea-pig, but not in rat, cat and man. The NPY-IR glandular innervation corresponded to about 20% of the NPY content of the nasal mucosa as revealed by remaining NPY content determined by radioimmunoassay after sympathectomy. These periglandular NPY-positive fibres had a distribution similar to the VIP-IR and PHI-IR nerves but not to the noradrenergic markers tyrosine hydroxylase (TH) or dopamine--hydroxylase (DBH). The NPY nerves around glands and some perivascular fibres were not influenced by sympathectomy and probably originated in the sphenopalatine ganglion where NPY-IR and VIP-IR ganglion cells were present. The venous sinusoids were innervated by NPY-positive fibres in all species except the cat. Dense NPY and DBH-positive innervation was seen around thick-walled vessels in the pig nasal mucosa; the latter may represent arterio-venous shunts. Double-labelling experiments using TH and DBH, and surgical sympathectomy revealed that the majority of NPY-IR fibres around blood vessels were probably noradrenergic. The NPY-positive perivascular nerves that remained after sympathectomy in the pig nasal mucosa also contained VIP/PHI-IR. The major nasal blood vessels, i.e. sphenopalatine artery and vein, were also densely innervated by NPY-IR fibres of sympathetic origin. Perivascular VIP-IR fibres were present around small arteries, arterioles, venous sinusoids and arterio-venous shunt vessels of the nasal mucosa whereas major nasal vessels received only single VIP-positive nerves. The trigeminal ganglion of the species studied contained only single TH-IR or VIP-IR but no NPY-positive ganglion cells. It is concluded that NPY in the nasal mucosa is mainly present in perivascular nerves of sympathetic origin. In some species, such as pig, glandular and perivascular parasympathetic nerves, probably of VIP/PHI nature, also contain NPY.     

Muscles and nerves of the posterior abdomen and genitalia of male Periplaneta americana (L.) (Dictyoptera : Blattidae)

Segmental and intersegmental muscles of abdominal segments 7–10 are described for adult, male Periplaneta americana (L.) (Dictyoptera : Blattidae). Locations of extrinsic and intrinsic genitalic muscles are documented, and the actions of those associated with the right phallomere are hypothesized. Muscles of the 5 abdominal segments are innervated by branches from 5 pairs of segmental nerves and 3 pairs of transverse nerves. These stem from a terminal synganglion, formed during embryogenesis by fusion of neuromeres of abdominal segments 7–11. One pair of segmental nerves issues from each of the 5 neuromeres, and one pair of transverse nerves arises from neuromeres of abdominal segments 7–9. The nerves are traced to the muscles, integument, and reproductive glands, and their peripheral unions are characterized. Serial homologies of the nerves and muscles are proposed, and comparisons are made with neuromusculature of the female.     

The chick embryo: a leading model in somitogenesis studies

The vertebrate body is built on a metameric organization which consists of a repetition of functionally equivalent units, each comprising a vertebra, its associated muscles, peripheral nerves and blood vessels. This periodic pattern is established during embryogenesis by the somitogenesis process. Somites are generated in a rhythmic fashion from the presomitic mesoderm and they subsequently differentiate to give rise to the vertebrae and skeletal muscles of the body. Somitogenesis has been very actively studied in the chick embryo since the 19th century and many of the landmark experiments that led to our current understanding of the vertebrate segmentation process have been performed in this organism. Somite formation involves an oscillator, the segmentation clock whose periodic signal is converted into the periodic array of somite boundaries by a spacing mechanism relying on a traveling threshold of FGF signaling regressing in concert with body axis extension.     

Nervous system of Triatoma infestans

The anatomy of the adult nervous system of the haematophagous bug Triatoma infestans has been studied by means of dissections and histology. The central nervous system comprises three nervous masses: the brain + suboesophageal ganglion, the prothoracic ganglion, and the posterior fused ganglion (meso + metathoracic + abdominal ganglia). The form of the brain is determined by the tubular head and the highly developed muscles of the pharyngeal pump. The prothoracic. ganglion is located near the posternum, the posterior ganglionic mass near the mesosternum. A significative variation of the branching pattern of abdominal nerves is reported. The innervations of mouth parts, salivary glands, muscles, retrocerebral complex, spiracles, rectum, reproductive organs, alary muscles, and peripheral nerves are described. © 1994 Wiley-Liss, Inc.