Ureters, Bladder, and Urethra

The Urinary System

The urinary system’s macro anatomyThe study of the structure of the human body. does not have many components.  The major organs are the kidneys, and you have two of them. If you don’t, it’s okay; the other one will compensate. Your left kidney is slightly higher than the right kidney.

The descending aorta delivers blood to the kidneys, and the blood returns to the body via a vein. However, waste products will be excreted through the ureters. There are two ureters, which connect the kidneys to the bladderA muscular organ that stores urine before excretion.. The bladder is suspended by ligaments and primarily serves as a storage unit for urineThe liquid waste excreted by the kidneys.. When you are ready, the urethraThe tube that carries urine from the bladder to the outside of the body. conducts urine to the outside. Blood enters the kidney. It can either return to the body through the renal vein. Alternatively, it can be excreted through the ureters, bladder, and urethra.

The urinary systemThe organ system that removes waste and maintains fluid balance. uses a mucus membrane. This membrane is open to the outside and must be kept moist.  There were 4 mucus membranes of the body and we’ve already talked about the digestive and respiratory membranes.  The urinary and reproductive systems are combined into the urethra output in people displaying a long urethra.  In people with shorter urtheras, the output of the urinary system and the reproductive systems are not combined.

Ureters

The ureterThe tube that carries urine from the kidney to the bladder., as seen in histological images, consists of epithelial tissue. It has a surrounding muscle layer. An outer adventitiaThe outermost connective tissue layer of an organ, such as the esophagus, which binds it to surround connects it to surrounding structures. Transitional epithelium is often confused with elastic connective tissue. It has dome-shaped cellsThe basic structural and functional units of life. lining the lumenThe inside space of a hollow organ or structure.. In contrast, elastic connective tissue appears as squiggly lines in arteriesBlood vessels that carry oxygenated blood away from the heart (except pulmonary arteries, which carr and veinsBlood vessels that return deoxygenated blood to the heart (except pulmonary veins, which carry oxyge. The dome-shaped cells stretch and flatten when the ureter expands.

Several tubes in the body contain hollow, collapsed lumens. These include the urethra, which is lined with stratified squamous epithelium. The vas deferens is covered in pseudostratified columnar epithelium with ciliaHair-like projections on the surface of some cells that move fluids or particles.. The uterine tube, which contains simple columnar ciliated epithelium, moves eggs along. These epithelial differences help distinguish the tubes.

Bladder

The bladder itself is primarily a storage organ and contains folds known as rugaeFolds in the stomach lining that allow expansion when food enters., which disappear when the bladder expands. The bottom portion of the bladder funnels into the urethra, an area called the trigoneA triangular area in the bladder between the ureter openings and the urethra, important for directin. Ligaments suspend the bladder, with one superiorAbove or toward the upper part of the body. ligament at the top and two transverse ligaments holding it in place.

A cross-section of the bladder reveals that it is lined with transitional epithelium, which allows for expansion. On a histology practical, you can distinguish between the bladder and the ureter by noting that the ureter appears as a tube. The bladder, in contrast, appears as a larger structure. The bladder’s dome-shaped cells are key indicators of transitional epithelium, which stretches as the bladder fills. Beneath this epithelial layer is the detrusor muscleThe smooth muscle layer of the bladder that contracts to expel urine., a smooth muscle responsible for bladder contraction and urine expulsion. The detrusor muscle is controlled involuntarily.

Urethra

The urethra starts as you descend through the bladder. Its length can vary significantly. This depends on what organ(s) contain it. The urethra is lined with stratified squamous epithelium, and urine samples typically contain sloughed-off cells from this lining. Mucous glands in the urethra facilitate the smooth movementA fundamental property of life involving motion of the body or its parts. of urine. Whether in the digestive, respiratory, or urinary systems, mucous glands serve a lubricating function. The urethral sphincters, composed of skeletal and smooth muscle, control the opening and closing of the urethra.

Urinary Tract Infections

A urinary tract infection can refer to infection in any part of the urinary system, kidneys, ureters, bladder, urethra. Most often UTI’s are bacterial . And most often people with shorter urethra gas have a greater tendency to pick up that bacteria. Urinary tract infections can be categorized as descending or ascending. These two words refer to the origin and final destination of the urinary tract infection. In descending infections the infection comes from the systemic blood supply descends the ureters to the bladder and urethra. In ascending urinary tract infections pathogens entering through the urethra travel up to the kidney creating an ascending pathway.

Micturition

The micturition reflexA reflex involving the contraction of the bladder and relaxation of the sphincter muscles that leads is both voluntary and involuntarily controlled and occurs much like the defecation reflex. There are two urethral sphincters. There is an internal urethral sphincter made of smooth muscle and involuntarily controlled. There is also an external urethral sphincter made of skeletal muscle. It is both involuntarily and voluntarily controlled.  This picture that I have here of the bladder is from someone who has a prostate gland. The prostate gland is strategically placed between these two sphincters.

Micturition can be initiated in a few ways. The primary sensory organs for initiation are baroreceptors. These baroreceptors are embedded in the wall of the bladder. These baroreceptors sense the higher pressureThe force exerted by gases in the respiratory system, affecting airflow and gas exchange. being put upon the inflated wall of the bladder as it fills with urine. There are chemoreceptors in the most superior wall of the bladder that also play a part in micturition. The confusion comes from recognizing that your bladder is controlled by both parasympathetic and sympathetic fibers.  The internal urethral sphincter is innervated with receptorsProteins located on the surface or inside cells that bind specific molecules (e.g., neurotransmitter that receive norepinephrineA neurotransmitter involved in attention, arousal, and the fight-or-flight response.. The external urethral sphincter is innervated with receptors that receive acetylcholinealso know as ACh A neurotransmitter that stimulates muscle contraction.. The micturition reflex is a carefully balanced act of both exciting and inhibiting neuronsThe functional cells of the nervous system that transmit signals.. Instead of describing the micturition reflex specifically, I think it’s important to understand certain drugs. These drugs are used to stop parasympathetic activity. These drugs are called anticholinergic drugs. People suffering from overactive bladder could be suffering from too many contractions of the detrusor muscle . This would create a situation in which urine is leaving the bladder when you don’t really want it to. Taking an anticholinergic drug could stop the excitatory signals coming to the detrusor muscle from

Spinal Cord Injuries & Urination

Nerves control the micturition reflex. They arise from the sacral plexusA network of nerves in the lower back that controls the pelvis and lower limbs.. Some nerves exit the spinal cordThe central nervous system structure that relays signals between the brain and body. at the T11T12 level. Spinal cord injuries and either of these places can yield issues with micturition. Some people are faced with an overactive bladder and leakage which is very common for women. Other people are faced with the inability to coordinate the micturition reflex and initiate voiding their bladder. This is not an area of much research. Not many people are faced with the inability to coordinate micturition. I found that much of the currentThe flow of electrical charge, as in ions moving across a neuron’s membrane. research on voiding is related to prostate swelling and management in older men..