María del Mar Yllera

This Special Issue follows a previous one entitled “Advances in Animal Anatomy”

The present study provides a detailed macroscopic examination (with some microscopic insights) of the genital apparatus of seven adult and intact male sugar gliders, as well as one castrated individual. The scrotum is pendulous and attached to the ventral abdominal wall, situated in the caudal part of the abdomen and cranial to the cloacal opening. The testes are oval shaped with their long axes oriented vertically. The epididymides are attached along the caudomedial border of their respective testes. The head and tail of the epididymides are in close proximity to the poles of the testes but are not directly attached. The deferent ducts are positioned laterally to their ipsilateral ureter as they run near the dorsal surface of the urinary bladder. The ampulla of the deferent duct is absent. The penis is located post-scrotally, lacks insertion into the bony pelvis, and has a bifid distal end. The crura of the penis originate within the ischiocavernosus muscles, and there are two bulbs of the penis. When flaccid, the entire penis is concealed in the perineal region and externalizes through an orifice situated in the ventral part of the cloaca, traversing its floor towards the cloacal opening. The urethral external orifice is positioned at the point where the bifurcation of the free part of the penis begins. The prostate gland resides in the pelvic cavity and consists of two parts: a macroscopically visible body surrounding the urethra and a microscopically identifiable portion embedded within the walls of the duct. Sugar gliders possess two pairs of bulbous bulbourethral glands, located dorsally and laterally to the rectum, but lack vesicular glands.

We dissected carcasses of eight mature females, both parous and non-parous specimens, to study the macroscopic anatomy of the female reproductive system in the sugar glider. The genital system includes double organs, namely the right and left ones, which are completely separated. It includes two ovaries, two oviducts, two uteri and a vaginal complex. The uteri are fusiform-shaped and lack horns. The vaginal complex includes two lateral vaginae and a median vagina, also called the ‘birth canal’. The cranial end of both lateral vaginae partially fuses, forming an expansion named the vaginal sinus, which is divided into two parts by a longitudinal septum, one for each vagina, where the ipsilateral uterine cervix opens. The caudal end of the lateral vaginae opens into a medial and impar duct: the urogenital sinus that serves as a common passage for the reproductive and urinary systems. In non-pregnant females, only the lateral vaginae are present. In pregnant and recently parous females, a short median vagina extends from the caudal wall of the vaginal sinus to the cranial end of the urogenital sinus. In the ventral wall of this sinus, next to its caudal opening, there is a forked clitoris.

This Special Issue was the result of reviewing Leonardo da Vinci's anatomical drawings of the bear foot and the horse trunk (among others)

The cat mandible is relatively small, and its manipulation implies the use of fixing methods and different repair techniques according to its small size to keep its biomechanical functionality intact. Attempts to fix dislocations of the temporomandibular joint should be primarily performed by non-invasive techniques (repositioning the bones and immobilisation), although when this is not possible, a surgical method should be used. Regarding mandibular fractures, these are usually concurrent with other traumatic injuries that, if serious, should be treated first. A non-invasive approach should also first be considered to fix mandibular fractures. When this is impractical, internal rigid fixation methods, such as osteosynthesis plates, should be used. However, it should be taken into account that in the cat mandible, dental roots and the mandibular canal structures occupy most of the volume of the mandibular body, a fact that makes it challenging to apply a plate with fixed screw positions without invading dental roots or neurovascular structures. Therefore, we propose a new prosthesis design that will provide acceptable rigid biomechanical stabilisation, but avoid dental root and neurovascular damage, when fixing simple mandibular body fractures. Future trends will include the use of better diagnostic imaging techniques, a patient-specific prosthesis design and the use of more biocompatible materials to minimise the patient’s recovery period and suffering.

Cats are one of our favourite pets in the home. They differ considerably from dogs but are usually treated clinically as small dogs, despite some anatomical and physiological dissimilarities. Their mandible is small and has some peculiarities relative to the dentition (only three incisors, a prominent canine, two premolars and one molar); a conical and horizontally oriented condyle, and a protudent angular process in its ventrocaudal part. Most of the body of the mandible is occupied by the mandibular dental roots and the mandibular canal that protects the neurovascular supply: the inferior alveolar artery and vein, and the inferior alveolar nerve that exits the mandible rostrally as the mental nerves. They irrigate and innervate all the teeth and associated structures such as the lips and gingiva. Tooth roots and the mandibular canal account for up to 70% of the volume of the mandibular body. Consequently, when fractured it is difficult to repair without invading the dental roots or vascular structures. Gaining a comprehensive anatomical knowledge and good clinical practice (such as image diagnosis before and post-surgery) will help in the awareness and avoidance of iatrogenic complications in day-to-day feline clinical practice.

Leonardo da Vinci was one of the most influencing personalities of his time, the perfect representation of the ideal Renaissance man, an expert painter, engineer and anatomist. Regarding Leonardo’s anatomical drawings, apart from human anatomy, he also depicted some animal species. This comparative study focused only on two species: Bears and horses. He produced some anatomical drawings to illustrate the dissection of “a bear’s foot” (Royal Collection Trust), previously described as “the left leg and foot of a bear”, but considering some anatomical details, we concluded that they depict the bear’s right pelvic limb. This misconception was due to the assumption that the bear’s digit I (1st toe) was the largest one, as in humans. We also analyzed a rough sketch (not previously reported), on the same page, and we concluded that it depicts the left antebrachium (forearm) and manus (hand) of a dog/wolf. Regarding Leonardo’s drawing representing the horse anatomy “The viscera of a horse”, the blood vessel arrangement and other anatomical structures are not consistent with the structure of the horse, but are more in accordance with the anatomy of a dog. In addition, other drawings comparing the anatomy of human leg muscles to that of horse pelvic limbs were also discussed in motion.