A scanning electron microscopical study of the dermal microcirculation of the equine foot

The microcirculation of the dermal laminae and papillae of the equine foot from seven clinically normal Australian ponies was studied using an improved microvascular casting corrosion technique and scanning electron microscopy. Casts of veins, arteries, capillaries and arteriovenous anastomoses (AVAs) were readily identified by their characteristic surface morphology. Arteries entered the laminar circulation axially, between pairs of axial veins, and were connected to each other by smaller calibre interconnecting arteries. Short abaxial branches of the axial interconnecting arteries gave rise to tufts of predominantly, proximodistally orientated, capillaries arranged abaxially in rows. The laminar veins anastomosed with each other extensively (the axial venous plexus) and formed most of the vascular skeleton of casts of the dermal laminae. AVAs were found throughout the laminar circulation but the largest and longest (40 mu diameter) were found clustered close to the origin of the axial arteries. The density of the laminar AVAs was estimated to be 500 AVAs/cm2. Blood vessels of the dermal papillae of the periople, coronary band, distal laminae, sole and frog shared a basic structural organisation. The cast of each papillary unit consisted of a central artery and vein enmeshed in a sheath of fine capillaries. At intervals along the length of the central artery were short branches which gave rise to tufts of capillaries. The capillaries formed a tortuous anastomosing plexus which encircled the papillary unit and drained into the central vein at intervals along its length. AVAs were always present at the base of the papillary units and anastomoses connected the central artery and vein. AVAs are important components of the dermal microcirculation of the equine foot and their distribution and density is compatible with their proposed role in the pathophysiology of equine laminitis.     

The vascular bed in the rabbit ear: microangiography and scanning electron microscopy of vascular corrosion casts

The vascular bed of the rabbit ear has been studied with light microscopy, microangiography and scanning electron microscopy of resin casts in a series of 20 ears. The major arteries supplying the ear were the central and rostral auricular branches of the caudal auricular artery. The caudal auricular branch was not observed, except as a small vessel supplying the rostral auricular base. The central auricular branch supplied blood to most of the auricular integument and was surrounded by capillaries extended from those supplying the skin. The periarterial capillaries formed a fine, compact network in the tunica media and were closely related to the central auricular branch. Evidence is presented suggesting that this vascular mechanism has a counter-current heat-exchange function for regulating body temperature. The artery had the well-developed internal elastic lamina and intimal cushions that regulate blood flow at the branching sites. A number of arteriovenous anastomoses were also observed between arterioles and venules, particularly in marginal regions of the ear. The intimal cushions and arteriovenous anastomoses might play an additional role in thermoregulation by regulating local blood flow in the ear.     

On the development of the papillary body in the feline claw

The pre- and post-natal development of the feline claw was studied in 22 feline fetuses with a crown-rump length (CRL) ranging from 40 to 160 mm, in six kittens up to an age of 22 days, and in four adult cats. In fetuses up to a CRL of 75 mm, the characteristic shape of the feline claw was developed. Segment-specific dermal modifications in the various segments, especially the dorsal ridge, started to develop in fetuses with a CRL between 75 and 105 mm. Modifications of the papillary body in the different claw segments took place in the last third of prenatal development and were continued postnatally. At first, the basal lamina became wavy, followed by the formation of small dermal microridges, which would be enlarged to dermal ridges and lamellae. In the claw of adult cats, the papillary body was very small. The dermal tissue of the proximal part of the coronet formed low microridges with short papillae originating on and between these low ridges. In the wall segment, dermal microridges were formed which were arranged in a parallel fashion, and in the distal part of the wall, short dermal micropapillae arose on the crest of each microridge. In the sole segment, thin dermal lamellae were developed. The sequence of papillary body development and the varying conformations of the papillary body in the different segments of the feline claw are compared to those in the nail, the canine claw and hooves.     

A macroscopic study of the vascular system of the bovine hind limb claw

The vascular organisation of the hind limb claws from clinically normal cattle was studied using plastic corrosion casts. The proper digital artery ran dorsodistally within the interdigital space and gave off a bulbar branch to the bulb, a plantar branch to the axial aspect of the wall and sole, and a coronary artery to the coronary margin and proximal wall. The artery entered the distal phalanx at the axial foramen, coursed through the nutrient canal as the terminal arch, and emerged at the abaxial foramen to anastomose with branches of the bulbar artery. During its interosseous course, the terminal branch gave off 6-8 primary branches which provided the arterial supply to the coronary margin, axial and abaxial wall, white zone and sole. The dorsal proper digital vein and axial and abaxial proper plantar digital veins drained all venous blood from the claw. Each of these large veins arose from numerous smaller veins which joined to form the venous networks of the coronary margin, wall, sole and bulb. A large arched vein passed through the coronary cushion and formed a connection between the superficial coronary venous plexus and the intra-osseous plexus of the distal phalanx. The axial and abaxial proper plantar digital veins were connected by a vessel through the bulbar cushion. At the same level, the axial proper plantar digital veins of the lateral and medial claw were connected to each other by a large vessel through the interdigital space, situated just proximal to the distal interdigital ligaments. This resulted in the presence of a complete distal venous arch along the plantar aspects of both claws. The parietal collecting veins drained most of the venous blood from the sole, white zone and wall, and connected directly to the venous plexuses of the coronary margin and bulb. Valves occurred commonly in medium and larger calibre veins throughout the claw.     

Portal streamlining as a cause of nonuniform hepatic distribution of sodium pertechnetate during per-rectal portal scintigraphy in the dog

The purpose of this study was to evaluate nonuniform patterns of vascular distribution of pertechnetate in the dog during per-rectal portal scintigraphy. Ninety-two studies were reviewed retrospectively to document the patterns of radionuclide distribution. Forty-five studies were classified as normal and 47 were classified as diagnostic for a macrovascular portosystemic shunt. In these dogs, shunt fractions were calculated and compared using a t-test. In dogs with sufficient liver radioactivity for evaluation, the study was classified as having uniform, dorsal, central, or ventral radiopharmaceutical distributions. There were 51 animals (45 normal and six dogs with low-magnitude portosystemic shunts) with sufficient liver activity to assess the radionuclide distribution within the liver. A one-way ANOVA was used to compare shunt fractions between each of the distribution patterns. Two dogs were anesthetized and selective portovenograms were performed. Portovenograms were compared with the scintigraphic images to correlate the vascular distribution of the right, central, and left divisional branches of the portal vein. The shunt fraction in the 45 normal dogs was significantly lower than in the dogs with portosystemic shunts (5.7% +/- 4.8% vs. 78.6% +/- 20.0% (mean +/- SD), P < 0.001). Of the 51 dogs with sufficient liver activity to classify the pattern of distribution, there were 15/51 (31.4%) with uniform radionuclide distribution, 10/51 (19.6%) with focal dorsal distribution, 15/51 (29.4%) with focal ventral distribution, and 10/51 (19.6%) with focal central distribution. There was no significant difference in the shunt fractions between the groups. There were six dogs diagnosed with low-magnitude portosystemic shunt with sufficient liver radioactivity to categorize the vascular distribution of the radionuclide within the liver. Of these six dogs, two had focal dorsal distribution, one had focal central, one had focal ventral and two had uniform distribution. Focal dorsal distribution could result from streamlining of the radionuclide into the right divisional branch of the portal vein. Focal ventral distribution could result from streamlining the radionuclide into the left divisional branch of the portal vein. Focal central distribution could result from streamlining the radionuclide into the central divisional branch of the portal vein.     

Vascularization of the Fleshy Comb in the Domestic Chicken

Up to now little is known about the vascularization of the chicken fleshy comb (crista carnosa). In order to evaluate the vascularization of the crista carnosa of the cook (breed White Leghorn), corrosion casts were created by injecting Plastoid into the internal carotid as described by Schummer (1951). Specimens were investigated by stereomicroscopy and scanning electron microscopy (SEM). Generally the dermis is highly vascularized by two capillary networks, which are localized beneath the epithelium and beneath the dermal papillas. The dense subepithelial network is characterized by the presence of sinusoid vessels. In the subcutaneous plexus numerous arteriovenous anastomoses of different types occur. Additionally there are arteriovenous anastomoses between the main vessels reaching the indentations of the comb. Our results show the presence of superficial and dense capillary networks and arteriovenous anastomoses are the anatomical basis for the functions of the chicken comb in mating behaviour and thermoregulation.
Reference  Schummer, A. 1951: Simplified method for plastoid corrosion. Anat. Anaz. 98 , 288–290.     

Ultrastructure of the horse tongue: further observations on the lingual integumentary architecture

This investigation examined primarily epidermal specializations of the adult horse tongue by light, scanning and transmission electron microscopy. Samples were collected from seven regions of the normal tongue of various breeds of horse. The filiform papillae, present on the dorsal and lateral aspects but not the ventral aspect of the tongue, were short, slender and finger-like structures with variable-shaped terminae. The epidermal thickness and height of dermal ridges were reduced on fungiform and vallate papillae, but tissue architecture and keratinocyte ultrastructure of most of the lingual epidermis corresponded to the common mammalian epidermal paradigm. One unique finding was the highly localized clustering of epidermal cells with exceptionally high content of PAS-negative trichohyalin cytoplasmic granules at a location atop the dermal ridges and beneath the base of filiform papillae. These granular cells were immediately subjacent to clusters of clear, non-granulated epidermal cells. It is believed that this integumentary specialization may enhance the structural strength at this localized site of the tissue architecture, in relationship to the mechanical papillae.     

"Subclinical" laminitis in dairy cattle

In dairying countries worldwide, the economic importance of lameness in cattle is now recognised. Laminitis is regarded as a major predisposing factor in lameness caused by claw disorders such as white zone lesions, sole ulcer, and heel horn erosion. The existence of subclinical laminitis was first suggested in the late 1970s by Dutch workers describing the symptoms of sole haemorrhages and yellowish-coloured, soft sole horn. In an attempt to clarify some of the confusing and often conflicting terminology, the literature on laminitis is reviewed. Disturbed haemodynamics, in particular repeated or prolonged dilation of arteriovenous anastomoses, have been implicated in the pathogenesis of both equine and bovine laminitis. Some characteristics of the vascular system of the bovine claw which may be of importance in the pathophysiology of the subclinical laminitis syndrome are therefore discussed. Clinical observations suggest that subclinical laminitis is a multifactorial disease. The different factors that are or may be involved in its aetiology vary in complexity and severity according to the management protocol of the animals. The possible involvement of subclinical laminitis in claw lesions is assessed.     

人和哺乳动物支气管动脉与肺动脉吻合现象研究进展

对人和哺乳动物支气管动脉与肺动脉吻合问题的研究进行了概述.肺动脉与支气管动脉吻合的意义在于支气管动脉的高氧血液可以进入肺动脉代偿供应肺泡组织,肺动脉的营养血液也可以进入支气管动脉代偿供应肺间质.肺动脉与支气管动脉之间血管吻合常可以发生在胸膜面、支气管壁、终末细支气管或呼吸性细支气管等部位,也可以在毛细血管上发生支气管动脉与肺动脉的吻合.根据血管吻合的长度和口径,将其分为长吻合型和短吻合型,按照血管吻合的方式分为端-端吻合和端-侧吻合.在某些病理情况下,肺动脉与支气管动脉之间的吻合支还会通过管径扩张,增加血流量来供应局部的病变组织,因此有利于防御不利因素对机体造成的损伤,为机体实施正常的呼吸功能提供保障.     

Ultrasonographic diagnosis of unusual portal vascular abnormalities in two cats

Two cases of ascites secondary to portal vascular abnormalities associated with portal hypertension are described. In the first case a five-month-old cat was presented with recurrent ascites and investigations showed that the underlying cause was a hepatic arteriovenous fistula. Ultrasonography showed direct communication of the coeliac artery and right branch of the portal vein. There was also hepatofugal flow in the main portal vein consistent with portal hypertension. The ultrasonographic features were similar to those seen in dogs with hepatic arteriovenous fistulae. In the second case, ascites, portal hypertension and an intraluminal mass in the main portal vein was diagnosed in a 16-year-old cat that had been presented with hyperthyroidism and hepatomegaly. Acquired portosystemic collaterals involving the left renal vein were present. Additional diagnostic investigations were not permitted. Ultrasonography was useful in both cases to document portal hypertension and the underlying cause.     

Vascular anatomy of the equine small colon

The vasculature of 22 small colons from dead adult ponies was perfused with latex or barium sulphate solution. The vascular anatomy was studied by use of dissection and alkali digestion of the latex specimens and microangiography of the barium sulphate-perfused specimens. The small colon is supplied by the caudal mesenteric artery. The left colic artery arises from the caudal mesenteric artery, which then becomes the cranial rectal artery. Branches from the left colic and cranial rectal arteries form anastomosing arcades that become narrower distally along the length of the small colon. From these arcades arise terminal arteries, which enter the small colon wall and give rise to a subserosal, an intermuscular, and a large submucosal plexus, with frequent anastomoses between them. The venous drainage closely parallels the arterial supply, except near to its origin from the portal vein, when the left colic vein and caudal mesenteric vein are separate from the corresponding arteries.     

Functional anatomy of the footpad vasculature of dogs: scanning electron microscopy of vascular corrosion casts

Dogs are well adapted to cold climates and they can stand, walk and run on snow and ice for long periods of time. In contrast to the body trunk, which has, dense fur, the paws are more exposed to the cold due to the lack of fur insulation. The extremities have a high surface area-to-volume ratio, so they lose heat very easily. We offer anatomical evidence for a heat-conserving structure associated with dog footpad vasculature. Methylmethacrylate vascular corrosion casts for scanning electron microscopy, Indian ink-injected whole-mount and histological specimens were each prepared, in a series of 16 limbs from four adult dogs. Vascular casts and Indian ink studies showed that abundant venules were arranged around the arteries supplying the pad surface and formed a vein-artery-vein triad, with the peri-arterial venous network intimately related to the arteries. In addition, numerous arteriovenous anastomoses and well-developed venous plexuses were found throughout the dermal vasculature. The triad forms a counter-current heat exchanger. When the footpad is exposed to a cold environment, the counter-current heat exchanger serves to prevent heat loss by recirculating heat back to the body core. Furthermore, the arteriovenous anastomoses shift blood flow, draining blood to the skin surface, and the venous plexuses retain warm blood in the pad surface. Hence, the appropriate temperature for the footpad can be maintained in cold environments.     

Morphology of the filiform lingual papillae in porcupine (Hystrix cristata)

The light and scanning electron microscopic structure of the filiform lingual papillae was studied in five adult porcupine (three males and two females). The tongue was characterised by a round tip, a rostral median sulcus and a deep lingual fossa which was situated just rostral to a prominent inter-molar eminence corresponding to a torus linguae. The filiform papillae were curved, enclosed a large connective tissue core and were separated by wide inter-papillary zones covered by a thick epithelium. Most filiform papillae had a cylindrical shape, but the rostral and central parts of the tongue contained a number of flat, comb-shaped papillae with rounded tips.     

Arteriovenous Fistulas as an Aid in Blood Collection from Canine Blood Donors

To facilitate blood collection from blood donor dogs, arteriovenous fistulas were established between the common carotid arteries and external jugular veins in five adult dogs. Twelve to 16 mm, side-to-side anastomoses were created using simple interrupted 6–0 polypropylene sutures. Starting 1 month after the surgical procedure, 500 ml of blood was collected from each dog as required. Electrocardiography, thoracic radiography, and cardiac output and rate were used to monitor cardiac changes. Blood flow characteristics, and proliferative and dystrophic cellular changes occurring in the vessels were documented in one dog.
The mean blood collection times were 2 minutes and 45 seconds from the fistula site and 9.0 minutes from the opposite jugular vein. Ventricular hypertrophy and myocardial changes were observed on electrocardiogram in two dogs, and radiographic evidence of pulmonary hypertension was noted in three dogs. Reversed blood flow was documented in the common carotid artery and external jugular vein distal to the arteriovenous fistula. Four dogs were still in use as blood donors 1 to 1 1/2 years after establishment of the fistulas. Clinical signs of congestive heart failure were not observed.     

Magnetic resonance microscopy of the equine hoof wall: a study of resolution and potential

REASONS FOR PERFORMING STUDY: Obtaining magnetic resonance images of the inner hoof wall tissue at the microscopic level would enable early accurate diagnosis of laminitis and therefore more effective therapy. OBJECTIVES: To optimise magnetic resonance imaging (MRI) parameters in order to obtain the highest possible resolution of the structures beneath the equine hoof wall. METHODS: Magnetic resonance microscopy (MRM) was performed in front feet from 6 cadaver horses using T2-weighted fast spin echo (FSE-T2), and T1-weighted gradient echo (GRE-T1) sequences. RESULTS: In T2 weighted FSE images most of the stratum medium showed no signal, however the coronary, terminal and sole papillae were visible. The stratum lamellatum was clearly visible and primary epidermal lamellae could be differentiated from dermal lamellae. CONCLUSION: Most structures beneath the hoof wall were differentiated. Conventional scanners for diagnostic MRI in horses are low or high field. However this study used ultra-high field scanners currently not available for clinical use. Signal-to-noise ratio (S/N) increases as a function of field strength. An increase of spatial resolution of the image results in a decreased S/N. S/N can also be improved with better coils and the resolution of high field MRI scanners will increase as technology develops and surface array coils become more readily available. POTENTIAL RELEVANCE: Although MR images with microscopic resolution were obtained ex vivo, this study demonstrates the potential for detection of lamellar pathology as it occurs. Early recognition of the development of laminitis to instigate effective therapy at an earlier stage and may improve the outcome for laminitic horses. Clinical MR is now readily available at 3 T, while 4 T, 7 T and 9 T systems are being used for human whole body applications.     

Reverse Saphenous Conduit Flap in Cats: An Anatomic Study

The vascular anatomy of the reverse saphenous conduit flap in cats was denned by contrast radiography of both hindlimbs of 18 feline cadaver specimens. In all 36 flaps, flow of contrast medium from the femoral artery to the distal end of the flap was documented. Direct anastomosis of the superficial branch of the cranial tibial artery with the cranial branch of the saphenous artery and communication of the caudal branch of the saphenous artery with the perforating metatarsal artery, via the medial and lateral plantar arteries, was documented. The cranial branch of the medial saphenous vein was shown to anastomose with the cranial branch of the lateral saphenous vein. The presence of these anastomoses support the feasibility of the reverse saphenous conduit flap as an option for reconstruction of wounds of the metatarsus in cats.     

Normal blood supply to the canine mandible and mandibular teeth

The normal blood supply to the canine mandible and mandibular teeth was determined by microangiography and correlated histology. Branches of the inferior alveolar artery supplied the cortical bone of the mandibular body. Vessels from the periosteal and endosteal surfaces supplied symphyseal cortical bone. Direct vascular anastomoses were not found to cross the fibrous mandibular symphysis. Blood supply to the mandibular teeth was via dental arteries derived from the inferior alveolar artery, with interdental and interradicular arteries supplying the alveolar bone and periodontal ligament.     

圆囊苔草叶片的形态解剖学研究

利用光学显微镜研究了圆囊苔草叶的形态结构。圆囊苔草叶基生,由叶鞘和叶片两部分组成,叶片扁平带状,平行脉序;上下表皮细胞垂周壁均呈不同程度的波浪状,外壁均有较薄的角质层和硅化乳突;正对主脉的上表皮有泡状细胞;上下表皮均有气孔器分布,并且上表皮气孔密度大于下表皮。等面叶,栅栏组织发达,叶肉细胞中有2种类型的异化细胞,相邻维管束之间有发达的气腔;叶脉稠密、维管束鞘2层,外层为较大薄壁细胞,内层为较小的厚壁细胞。由纤维组成的机械组织,成片存在于绝大多数叶脉的上下方。     

Partial anomalous pulmonary venous connection in a dog

A 2-year-old male intact Belgian Malinois was presented for exercise intolerance. A grade III/VI left basilar systolic murmur was detected. Echocardiography revealed moderate right atrial and ventricular dilation and increased pulmonic outflow velocity. Thoracic radiographs showed right heart enlargement and a dilated caudal vena cava. In addition, on the left lateral projection, an enlarged aberrant right cranial pulmonary lobar vein was suspected to be diverging ventrally from the course of the right cranial lobar bronchus and inserting more ventrally than normal in the region of the right atrium. A left-to-right pulmonary vascular shunt was suspected, and the patient underwent further diagnostics under general anesthesia. An agitated saline study was positive, suggestive of a concurrent right to left shunt. A right heart catheterization was performed. Angiography was inconclusive. Oximetry testing revealed an increase in oxygen saturation within the right atrium at the level of the caudal cava supportive of a left-to-right shunt in this region. Computed tomography angiography revealed a large single pulmonary vein that anomalously entered into the caudolateral aspect of the right atrium (left-to-right shunt) and was suspicious for a small arteriovenous malformation between the right caudal pulmonary artery and the right pulmonary vein returning to the left atrium (right to left shunt). The patient was diagnosed with a partial anomalous pulmonary venous connection and a possible arteriovenous malformation.     

Development of a Free Latissimus Dorsi Muscle Flap in Cats

Anatomic and experimental evaluation of the feline latissimus dorsi muscle was performed to assess its potential use as a free muscle flap. In the anatomic study, nonselective angiography of the subscapular artery was performed in nine heparinized feline cadavers. The muscle dimensions and vascular anatomy of the dissected latissimus dorsi muscle were recorded. In the experimental study four cats underwent heterotopic transplantation of a partial latissimus dorsi flap, and three cats underwent orthotopic transplantation of a complete latissimus dorsi flap. The mean length and width of the latissimus dorsi muscle was 19.0 and 5.4 cm, respectively. The dominant vascular pedicle was the thoracodorsal artery and vein. The average length and diameter of the thoracodorsal artery was 2.7 cm and 0.6 mm, respectively. Minor vascular pedicles were provided by branches of the intercostal arteries. Numerous choke anastomoses existed between the two pedicle systems. Viability of muscle flaps based on subjective evaluation, angiography, and histopathology, was 66% and 100% in the heterotopic and orthotopic studies, respectively. Flap failure seemed to be caused by both arterial and venous thrombosis. The latissimus dorsi muscle flap met criteria required for application in microvascular reconstruction. The vascular pattern was appropriate and consistent. Donor site morbidity was low, whereas surgical accessibility was high. The muscle satisfied the physical criteria of a free flap. Long-term anastomotic patency and flap viability was shown.