A Comprehensive Guide to Canine Bladder Anatomy

The canine bladder is a vital organ that plays a crucial role in a dog's overall health. It's a muscular sac that stores urine until it's expelled from the body.

Located in the abdominal cavity, the bladder is positioned behind the pubic bone and in front of the rectum. This unique position allows for efficient storage and elimination of urine.

The bladder is made up of a thick, muscular wall that's capable of storing up to 600 milliliters of urine. This impressive capacity is made possible by the bladder's ability to stretch and expand as it fills with liquid.

In dogs, the bladder is typically around 2-3 times larger than it is in humans, making it a remarkable organ that's specifically adapted to meet the needs of our canine companions.

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The canine urinary system is a vital part of a dog's overall health, and understanding its anatomy can help you better care for your furry friend.

Dogs have two kidneys located in the abdominal cavity under the backbone, close to where the last rib meets the spine.

The kidneys play a crucial role in filtering waste and excess fluids from the blood, which is then carried away by the ureters to the bladder.

In a dog, the ureters extend from each kidney to the bladder, forming a vital connection between the kidneys and the bladder.

The bladder is located in the abdomen just in front of the pubic bone of the pelvis, where it stores urine until it's released.

The urethra, the tube that carries urine from the bladder to the outside, passes along the floor of the pelvis and ends in the vestibule of the vagina in female dogs or at the tip of the penis in male dogs.

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The canine bladder is a complex organ that plays a vital role in our furry friends' overall health. It can be divided into three main parts: the apex, body, and neck.

The bladder's triangular area on the dorsal aspect of the neck is called the trigone. This is where the ureters enter the bladder and the urethra is located.

The smooth muscle of the bladder is arranged in bundles with different orientations, including spiral, longitudinal, and circular. The circular bundle is specifically called the detrusor muscle, which is responsible for complete emptying of the bladder.

The detrusor muscle's fibres are intimately fused, meaning that stimulation results in the bladder emptying completely. This is crucial for our dogs to be able to urinate properly.

Related reading: Canine Bladder Cancer Stages

Dogs and cats have two kidneys, both located in the abdominal cavity under the backbone, close to where the last rib meets the spine.

The kidneys are positioned to allow for efficient filtration of waste and excess fluids from the blood. They are protected by the ribcage and the surrounding muscles.

The ureters, one from each kidney, extend from the kidneys to the bladder. This tube-like structure is narrow and muscular, allowing it to propel urine towards the bladder.

In the female dog, the urethra, the tube that carries urine from the bladder to the outside, passes along the floor of the pelvis and ends in the vestibule of the vagina. This is a relatively short distance, allowing for efficient urine flow.

Urinary incontinence in dogs is often the result of weak sphincter muscle tone at the urinary bladder. This can lead to leaking of urine, either small or large volumes, especially when the dog is lying down.

The urinary bladder is a muscular organ that stores urine until it's time to urinate. In dogs, the bladder is controlled by the urethral sphincter, which surrounds the urethra and prevents urine from leaking out. If the sphincter muscle tone is weak, the dog may experience urinary incontinence.

The urethral sphincter mechanism incompetence is a condition where the urethral sphincter doesn't function properly, leading to intermittent leakage of urine when the dog is recumbent or excited. This condition is more common in spayed females.

Here are some conditions that can cause urinary incontinence in dogs:

Polyuria and pollakiuria are different from urinary incontinence, but can be difficult to distinguish. Polyuria refers to an increased volume of urination, while pollakiuria refers to an increased frequency of urination.

The bladder can be divided into three main parts: the apex, body, and neck. The apex is the top part, the body is the main part, and the neck is the narrow part that connects the bladder to the urethra.

The trigone of the bladder is a triangular area on the back of the bladder neck. It's a crucial area where the ureters enter the bladder.

The bladder is made up of smooth muscle that's arranged in bundles with different orientations. This muscle is called the detrusor muscle, and it's responsible for emptying the bladder.

The detrusor muscle is made up of fibres that are intimately fused, which means that when it contracts, the bladder empties completely. This is important for preventing urine from leaking out.

The urethra is lined with smooth muscle that forms the internal urethral sphincter (IUS). The IUS helps to control the flow of urine out of the body.

Skeletal muscle forms the external urethral sphincter (EUS), which is located further down the urethra. The EUS helps to control the flow of urine by contracting and relaxing.

The bladder is controlled by both voluntary and involuntary components of the nervous system. The sympathetic nervous system helps to regulate the filling phase of the bladder.

The sympathetic nervous system does this by stimulating alpha-adrenergic fibres in the trigone and proximal urethra, which causes the IUS to contract. This helps to prevent urine from leaking out.

The parasympathetic nervous system, on the other hand, helps to regulate the emptying phase of the bladder. It does this by stimulating the detrusor muscle, which causes the bladder to contract and empty.

Suggestion: Skeletal System of a Dog

As the bladder fills, sensory stretch receptors in the bladder wall are stimulated. These receptors send signals to the spinal cord and brain, which helps to regulate the urge to urinate.

The pelvic and hypogastric nerves play a crucial role in transmitting these signals to the brain. They help to regulate the urge to urinate and the ability to control the flow of urine.

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Intramural ganglia are a crucial part of the bladder's anatomy, and understanding their histology is essential to grasping how the bladder functions.

Histological studies have been conducted on full-thickness bladder sections obtained from dogs and humans, revealing differences in the location and number of intramural ganglia between species.

In dog bladders, intramural ganglia are more commonly found in the adventitial/serosal layer compared to the lamina propria and inner longitudinal muscle layer.

In contrast, human bladders have ganglia evenly distributed across the various layers, with no significant differences between the layers.

The numbers of neuronal cell bodies per ganglion are higher in the adventitial/serosal layer in dog bladders, whereas in human bladders, the numbers are similar across the layers.

These findings suggest that there are species differences in the histology of intramural ganglia, which may have implications for our understanding of bladder function and dysfunction.

A physical examination is a crucial step in understanding an animal's anatomy and physiology.

The examination should include a detailed look at the perineal or preputial area to check for urine staining or secondary pyoderma.

Urination should be observed to evaluate the ability to initiate urination, the presence or absence of stranguria or urinary tenesmus, and the diameter of the urine stream.

The urinary bladder should be palpated before and after voiding to evaluate its distension, size, and tone.

Manual bladder expression can provide information about sphincter tone and help differentiate between upper motor neuron (UMN) and lower motor neuron (LMN) disorders.

A digital vaginal examination should be performed in female dogs to check for masses within the genitalia or distal urethra.

A rectal examination is also necessary to evaluate anal tone and assess the prostate gland, urethra, and pelvic diaphragm.

Decreased anal tone can be observed in animals with lower motor neuron incontinence due to the involvement of the sacral segment of the spinal cord and the pudendal nerve.

The perineal and bulbocavernosus reflexes can also be assessed during the examination.

In all cases, an orthopaedic examination should be performed to check for degenerative joint disease, which is common in older animals and may contribute to difficulty urinating.

A urinalysis test is performed to examine your dog's urine, and it's essential to provide a fresh sample for accurate results.

Your veterinarian may also analyze bloodwork or submit urine for culturing to better understand the underlying cause of the issue.

In some cases, X-rays or an ultrasound may be used to evaluate your dog's urinary problem, and in more complex cases, an internal medicine specialist may be referred to for further testing like an endoscopy or biopsy sampling.

Diagnosing urinary issues in dogs requires a thorough examination of their symptoms and a series of tests to determine the cause.

Your veterinarian will likely start with a urinalysis test to examine your pet's urine, which needs to be fresh.

They may also analyze bloodwork, submit urine for culturing, or use imaging tests like X-rays or ultrasound to better evaluate the issue.

In some cases, pets may need to be referred to an internal medicine specialist for more advanced testing like an endoscopy or biopsy sampling.

Muscle strips from dog bladders were collected from nine dogs, including seven male sham-operated mixed-breed hound dogs and two adult female beagles.

The bladders were washed in Tyrode buffer, a solution containing various salts and sugars, and then immersed in Custodiol HTK organ transport media to preserve them for contraction studies.

Human bladders were collected from six organ transplant donors, three males, and three females, and were harvested within 30 minutes after cross-clamping the aorta.

The bladders were transported to the laboratory within 40 hours immersed in Belzer's Viaspan University of Wisconsin organ transport solution or Custodiol HTK on wet ice.

Differences in the organ transport media used for dog and human bladders were tested, and no differences were found in the responses of muscle strips dissected from bladders stored in either solution.

Dog bladders were dissected in a cold room, and muscle strips were taken from the dorsal and ventral aspects of the dome and the central middle part of the bladder.

The dissections were performed using sharp micro scissors and magnifying loops, and the strips were taken along visible fascicles of myofibrils.

For the inner longitudinal muscle layer strips, the mucosa was separated from the underlying layers by sharp dissection, and the strips were obtained with the long axis parallel to the direction of the muscle fibers.

The strips were clamped between force transducers and positioners and mounted in muscle baths containing Tyrode solution at 37°C.

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A dog urinary problem can occur at any area along the urinary tract, from an uncomplicated infection to serious cancers.

The urinary tract has many functions, including filtering the blood to remove toxins.

Problems can occur in the urinary tract's ability to maintain a balance of electrolytes, such as sodium and potassium.

Urine is created as a waste by-product of the body's filtering process.

The urinary tract also reabsorbs water for the body, making it essential for maintaining proper bodily functions.

Problems in the urinary tract can range from mild to severe, and it's crucial to identify the issue early to prevent further complications.

The findings of this study on canine bladder anatomy are quite fascinating and provide valuable insights into the layer-dependent differences in bladder detrusor muscle.

Dog bladders have a greater muscle layer-specific myogenic and muscarinic responses in the inner longitudinal muscle layer compared to the outer layer.

In contrast, the outer longitudinal muscle layer of dog bladders shows more neurogenic responses, which are concomitant with higher axonal density, ganglia numbers, and numbers of neurons/ganglia in this same outer layer.

Human bladders have similar nicotinic responses, with more in the inner layer, and neurogenic responses, with more in the outer layer, as dog bladders.

However, unlike dogs, human bladder specimens do not show muscle layer-dependent myogenic and muscarinic responses.

These findings expand our knowledge of layer-dependent differences in bladder detrusor muscle and are essential for understanding and treating bladder disease in both dogs and humans.