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Urinary Bladder facts that you find here will spell out its anatomy and functions and of course, some fun facts that you should know. Before we move on with our facts list, it is imperative to say that we will be focusing on Urinary Bladder in humans and we will not go for other animals such as reptiles, mammals, birds, fish and amphibians. Covering everything is simply beyond the scope of this article. So let us begin…

Urinary Bladder Facts: 1-5 | What is Urinary Bladder?

1. The Urinary Bladder in humans is an organ. It is made of muscles and it is hollow by design. It is more like a sac.

2. The hollow design makes it work like a storage unit where urine is stored only to be disposed off at a later time. The urine it holds comes from the kidneys and enters the Urinary Bladder through two tubes known as as Ureters (singular: Ureter).

3. The Urinary Bladder is very much like an elastic bag. In terms of biology, it is distensible. It sits on our pelvic floor right behind our pelvic bone.

4. In empty conditions, the Urinary Bladder resembles the shape of a pear. When the bladder is full, it takes an oval shape. As far as size is concerned, it is about 2 inches long. However, it can grow up 6 inches when full.

5. The amount of urine it can hold can range between 300 ml and 500 ml or 10.14 fluid ounces to 16.90 fluid ounces. However, the urge for urination occurs when the bladder is about one-quarter (1/4th) full. However, we hold urine for much longer than that.

Urinary Bladder Facts: 6-10 | How Does the Bladder Work?

6. When empty, the inner lining of the Urinary Bladder makes folds and tucks in. When urine fills in, the lining and hence the bladder expands to accommodate urine flowing in through the Ureters.

7. When empty the muscle walls of the bladder becomes thick and the whole organ becomes firm. However, this is only temporary.

8. The moment the Kidneys process urine and send the liquid through the Ureters all the way down to the bladder, the muscle walls of the Urinary Bladder start thinning and the bladder starts expanding. One thing of note here is that the urine runs down the Ureters because of:

  • Gravity.
  • Peristalsis – a wave-like movement of the Ureters.

9. As the bladder keeps expanding, it needs space. The growing bladder gradually moves upwards and fills in the space in the abdominal cavity.

10. There are two question that need to be asked. They are:

  • Will the Urinary Bladder leak? No, not really no! The bladder has an internal muscular valve known as internal sphincter. It prevents leaking of the urine from bladder.
  • Will the urine flow back into the Ureters? No, that’s not possible because of the shape of the bladder. It has a triangular shape which is known as ‘trigone’. This shape prevents urine from flowing back into the Ureters. To be more specific, there are two flaps covering the Ureteric Orifices (openings of the Ureters) preventing backward flow of urine known as vesicoureteral reflux. This trigone shape is also responsible for preventing the Urethra from stretching as well. Urethra is from where the urine flows out.

Urinary Bladder Facts: 11-15 | External Structure of Urinary Bladder

11. The external structure of Urinary Bladder has been divided into four parts. These parts are:

  • Apex
  • Fundus
  • Neck
  • Body

12. The Apex of the Urinary Bladder is the part of the bladder which is directed upwards. It directs towards Pubic Symphysis’ upper part. The Apex (which was previously known as the Vertex) connects with Umbilicus using a ligament known as the Median Umbilical Ligament.

13. The Fundus is the other name for the base of the Urinary Bladder. It has a posterior location (that is, towards the back). It has a slightly triangular shape with the triangle tip pointing backwards. The Fundus in females lies against the vagina while in males, it lies against the rectum.

14. The Neck of the Urinary Bladder is the inferior aspect of the bladder. (Inferior in Anatomical Terminology means ‘below’ while superior means ‘above’.) So, the Neck of the bladder lies below the Apex, the Fundus and the Body. The Neck is the place where the walls of the bladder narrow down and converges down like a funnel towards the Urethra. In males, the Urinary Bladder’s Neck is adjacent to Prostate Gland. In females, the Urinary Bladder Neck changes position (Source) depending on the body position.

15. The Body is the Urinary Bladder’s largest part. It is between the Apex, Fundus and Neck. It is the main part of the bladder and it proceeds upwards towards the Apex.

Urinary Bladder Facts: 16-20 | Internal Structure of Urinary Bladder

16. When it comes to the internal structure of the Urinary Bladder, it is pretty complex. There are several distinct tissue layers each with a distinct job to perform. There are three layers:

  • Mucosa Layer
  • Submucosa Layer
  • Muscularis Layer or Detrusor Muscle

17. The innermost layer (when viewed from inside the bladder lumen or space) is the mucosa layer. Transitional epithelial tissue lines up this layer This transitional epithelial tissue is capable of significant stretching so that large volumes of urine can be held in the bladder. This tissue layer is also responsible for protecting the tissues underneath it from urine that is alkaline or acidic by nature.

18. Sitting atop the mucosa layer is submucosa layer. This submucosa layer is made of connective tissue containing nervous tissues and blood vessels. These nervous tissues and blood vessels help in the controlling the surrounding tissue layers.

19. Atop the submucosa are the visceral muscles of what is known as the muscularis layer. This muscularis layer is the one that allows expansion and contraction of the bladder. The muscularis layer has another name. It is also known as detrusor muscle.

20. When it is time to expel the urine, the detrusor muscle or the muscularis layer contracts, squeezing out the urine from urethra. This detrusor muscle is also responsible forming internal urethral sphincter. This sphincter is nothing but a muscle ring surrounding the opening of the urethra. This sphincter keeps the urethral opening shut by staying contracted. When it is time to pee, the sphincter relaxes so that the urine can flow out.

Urinary Bladder Facts: 21-25 | Urinary Bladder Trigone

21. The Urinary Bladder Trigone is a triangular shaped area inside the Urinary Bladder and it is located above urethra. While in a 2D diagram of the urinary system, it is normal to think that the ureters connect with the bladder somewhere on the top, it is not true. The ureters connect with the bladder from behind, near the Fundus.

22. The two Ureteric Orifices and the Urethral Orifice (orifice means opening) make a triangular area known as the Trigone. This Trigone sits right inside the Fundus [See the last image in previous page].

23. The two Ureteric Orifices stay covered with mucosal flaps. The job of these flaps is to behave like valves and prevent urine from passing back into the Ureters (that is, prevention of vesicoureteral reflux).

24. Between the orifices of the Ureters, there is a raised tissue area. This area is called Interureteric Crest. This crest is what marks the upper lining of the Urinary Bladder Trigone. The trigone that is formed by these three openings is actually the bladder floor right above the Urethra and is blessed with smooth muscles unlike the rest of the interiors of the bladder with irregular surface.

25. The reason why the trigone has a smooth surface is that the smoothness eases the urine flow into the trigone and out of the trigone.

Urinary Bladder Facts: 26-30 | Just Random Facts

26. For a person with healthy urinary system, the Urinary Bladder is capable of holding urine for a period of up to 5 hours.

27. When a person pees, the Urinary Bladder will completely empty itself. This happens each and every time a person urinates.

28. The Urinary Bladder is said to be ‘overactive’ if a person needs to pee more than 8 times in a day. Emptying the bladder up to 8 times a day is just fine.

29. Both genders – males and females – can suffer from bladder problems. However, the problems are far commoner in certain groups of people such as women who recently had children, men with prostate problems and older people.

30. Overactive Bladder is two types – ‘Dry’ and ‘Wet’. Dry means that a person gets sudden and urgent need for urinating many times a day. Wet means that a person has to pee and at the same time, his or her bladder leaks. The Wet Overactive Bladder goes by another name – Urge Incontinence.

Hope you liked our urinary bladder facts article. If you want us to write more on similar topics, please drop a comment in the comment box.

Sources: 1, 2, 3, 4, 5, 6, 7

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