How Does the Urinary System Work : The urinary system works as a filter, removing toxins and wastes from your body through urine. It uses a series of tubes and ducts to pass this waste. These tubes are connected to your blood vessels and digestive system. Your urinary system helps the rest of your body to function properly.
The function of the urinary system is to filter blood and make urine as a waste byproduct. The organs of the urinary system include the kidneys, renal pelvis, ureters, bladder, and urethra.
Introduction Urinary System :
The urinary system consists of the kidneys, ureters, bladder and urethra. The kidneys are located on the posterior wall of the abdomen on each side of the vertebral column, behind the peritoneum and below the diaphragm.
The kidneys are bean-shaped organs measuring 11 x 6 x 3 cm (length, width and thickness). The weight in an adult is 150 grams. The kidneys are deep in the abdomen on either side of the vertebral column.
How Does the Urinary System Work :
The organs differ in relation to the two kidneys.
- Right kidney
- Left kidney
Right kidney – Right adrenal gland, liver, duodenum colon, diaphragm muscles of the posterior abdominal wall.
Left kidney – Left adrenal gland spleen, stomach, pancreas colon jejunum, diaphragm muscle of the posterior abdominal wall.
Gross Structure of the Kidney :
The kidneys are surrounded by a fibrous capsule. Underneath the capsule is the cortex. The innermost part is the medulla which is made up of conical shaped strips. They are also called pyramids.
The hilum is the medial concave border of the kidney. Blood vessels, lymphatic vessels, ureters and nerves enter through the hilum. renal pelvis is funnel shaped Structure that receives urine from the major and minor calyces (tubes). The pelvis continues as urine from both sides.
Kidney – Microscopic Structure :
Each kidney is made up of one million smaller functional units called nephrons. Each nephron is made up of Bowman’s capsule containing a network of blood vessels called the glomerulus.
This funnel (cup) shaped structure continues as the proximal curved tubule, the loop of Henle, and the distal curved tubule (small tube with many turns). The blood reaching the glomerulus is filtered into it and the useful blood material is reabsorbed during the process of urine formation.
These are tubular organs 25 to 30 cm long and 3 mm in diameter. They start from pelvis of the kidney and enter the urinary bladder. It is made up of three layers. The outer fibrous tissue, middle muscular layer and inner mucosa lined with transitional epithelium.The ureters propel the urine from kidneys into the bladder.
Urinary Bladder :
The bladder is a reservoir for urine. The bladder is located in the pelvic cavity behind the symphysis pubis. The dilated bladder rises in the abdomen. The bladder is pear shaped and becomes oval when filled with urine.
It is covered by the peritoneum only on the upper surface. The bladder wall is made up of outer fibrous connective tissue with blood vessels, lymphatic vessels, and nerves. The middle layer contains smooth muscles known as detrusor muscles.
The inner layer mucosa is made up of transitional epithelium. The urge to urinate is felt when the bladder holds 300 to 400 ml of urine. The maximum capacity of the bladder is 600 ml. Three openings (perforations) in the wall of the bladder form a triangle also known as a tri-gon.
The upper two openings on the posterior wall are the openings of the ureters. The lower opening is the origin of the urethra. this is It is built on a layer of smooth muscle that is not under voluntary control.
Urethra Structure :
It is 5 cm long in females and 20 cm in males. In both males and females the urethra is close to the genital organs. In women, it is behind the symphysis pubis and opens out in front of the vagina.
In both sexes it is made up of three layers. The outer layer is muscular (smooth) and elastic in nature and is under autonomic nervous control. The urethra remains closed due to the constant contraction of the muscles of the internal urethral sphincter (opening).
The external urethral opening is under voluntary neural control. The middle layer called the sub-mucosa is a spongy layer containing blood vessels and nerves.
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