What is the Urinary System? The urinary is system is a system of production, storage, and the elimination of urine. Formation and elimination of the urine is important for the human body because it contains nitrogenous wastes of the body that must be eliminated to maintain homeostasis. The urinary system is important for keeping the internal environment of the body clean. This particular system maintains proper homeostasis of water, salts and nitrogenous wastes (Iqba, 2010). There are four major organs that make up the Urinary system.
The four major organs are the kidneys, ureters, urinary bladder, and the urethra. The first organ within the urinary system is the kidney. The kidney is considered as the major organ of the entire system itself. The kidney is classified as a two bean shape organ that lies close to the lumbar spine on either side of the body. This organ controls the concentration of the urine. In the human body, you have two kidneys. They are protected by the lower rib cage and located under the muscles of the back and behind the parietal peritoneum, which is the membrane that lines the abdominal cavity.
The left kidney lies approximately at a vertebral level T12 to L1, which leaves the right kidney a little lower than the left one (Iqba, 2010). The function of the kidneys is to form urine, keep substances stable in the blood, make erythropoietin to produce red blood cells, make vitamin D active, and regulates blood pressure. It is the essential for homeostasis and the maintenance of life. The second major organs are the ureters. The ureters are classified as two hollow muscular tube, where you have one arising from each kidney and ending at the urinary bladder, which connects the kidneys to the bladder.
Within the human body there are two ureters. Each of the ureters is about 10 inches long; they lie in a vertical plane. The ureters have three constrictions. The muscles that are within the ureters walls tighten and relax forcing the urine to go down the tube in order for it to move away from the kidneys. The first constriction exists where the renal pelvis join the ureters, the second constriction occurs where it is kinked as it crosses the pelvic brim, and the third constriction is where it pierces the wall of the bladder (Iqba, 2011).
The third major organ is the urinary bladder. The urinary bladder is identified as a triangular shape. The bladder has an apex, base, a superior surface, and two inferolateral surfaces. It is located in lower abdomen, where it is held in place by the ligaments that are attached to the pelvic bones. The wall in the bladder relaxes, and expands to store the urine. It also contracts and flattens so it can empty the throughout the urethra. The apex lies behind the upper symphysis pubis, which is connected to the umbilicus ligament.
The base of the bladder has triangular shapes and faces posteriorly. Iqba states that the “superolateral angles of the bladder are joined by the ureters and the inferior angle is joined by the urethra. The vasa deferentia lie side by side on the posterior surface, separating the seminal vesicles from one another”. The urinary bladder functions as storage for the urine to delay the frequency of urination. The urinary bladder is made of several distinct tissue layers: the innermost layer of the bladder is the mucosa layer that lines the hollow lumen.
Unlike the mucosa of other hollow organs, the urinary bladder is lined with transitional epithelial tissue that is able to stretch significantly to accommodate large volumes of urine. The transitional epithelium also provides protection to the underlying tissues from acidic or alkaline urine. Surrounding the mucosal layer is the submucosa, a layer of connective tissue with blood vessels and nervous tissue that supports and controls the surrounding tissue layers. The visceral muscles of the muscularis layer surround the submucosa and provide the urinary bladder with its ability to expand and contract.
The muscularis is commonly referred to as the detrusor muscle and contracts during urination to expel urine from the body. The muscularis also forms the internal urethral sphincter, a ring of muscle that surrounds the urethral opening and holds urine in the urinary bladder. During urination, the sphincter relaxes to allow urine to flow into the urethra. It is considered as one of the most elastic organ of the body, and it is able to increase the volume greatly to accommodate 600 to 800 ml of urine at the maximum capacity.
The urinary bladder also helps to expel urine from the body during urination by contraction of the detrusor muscle and the relaxation of the internal urethral sphincter. The last major organ is the urethra. The urethra is a duct that connects to the urinary bladder to the genitals for the removal of fluids out of the human body. The tube that allows urine to pass outside the body. The brain signals the bladder muscles to tighten, which squeezes urine out of the bladder. At the same time, the brain signals the sphincter muscles to relax to let urine exit the bladder through the urethra.
When all the signals occur in the correct order, normal urination occurs. In males, the urethra travels through the penis and is the route for passage of both urine and semen. The male urethra is about 8 inches long and extends from the neck of the bladder to the external meatus of the glans penis. It provides exit for urine as well as semen during ejaculation. It is divided into three parts: the first part is the Prostatic urethra, which is about 1. 25 inches long that begins at the neck of the bladder and passes through the prostate from the base to the apex.
It is the widest and most dilatable portion of the urethra. On the posterior wall, there is a longitudinal ridge called the urethral crest, on each side of which is a groove called prostatic sinus. The prostatic ducts open into these sinuses. On the summit of the urethral crest is a depression known as the prostatic utricle. It is an analog of the uterus and vagina in females. On the edge of the mouth of the utricle are the openings of the two ejaculatory ducts. The Membranous urethra is the part that lies within the urogenital diaphragm.
It is about 0. 5 inches in length and is surrounded by the sphincter urethrae muscle. The membranous urethra is the shortest and the least dilatable part of urethra(Iqba, 2010). The bulbourethral glands are found posterior to this part of urethra but they open into the penile urethra. The membranous urethra is continuous above with the prostatic urethra and below with the penile urethra. Lastly the Penile urethra It is about 6 inches long and is enclosed in the bulb and corpus spongiosum of penis.
The terminal part of the penile urethra, which lies within the glans penis, is dilated to form fossa terminalis (navicular fossa) ( Iqba, 2010). The ducts of the bulbourethral glands open into the penile urethra below the urogenital diaphragm. In females urethra is shorter and is used only for urination. The female urethra is about 1. 5 inches in length. It extends from the neck of the bladder to the external meatus, where it opens into the vestibule about 1 inch below the clitoris. The female urethra traverses the sphincter urethrae muscle and lies in front of the vagina.
At the sides of the external urethral meatus, there are small openings of the ducts of the paraurethral glands. Female urethra can be dilated easily as compared to the male urethra. The urethra develops from endoderm, and the surrounding splanchnic mesoderm of the urogential sinus (Mescher, 2010). At 7 weeks’ gestation, the cloaca divides into the urogenital sinus and the rectum with the development of the urorectal septum. The paramesonephric, or Mullerian, tubercle divides the urogenital sinus into the pelvic and phallic portions, which will become the vesicourethral unit and the lower vagina, respectively.
The female urethra is typically developed by the 12th gestational week. The urinary system is basically considered as one of the most important systems in a human body, because it helps produce and function our urine throughout or body. In order for our body to function properly with the urinary system we need the following organs: kidneys, urinary bladder, urethra, and the ureters. We need all of these organs because they help our bodies function in a particular way. This system is very important, because it helps control what fluids enter and exit our bodies.
