Question

1. Describe the anatomy and physiology of urinary system.

Answer 1

The urinary system consists of the kidneys, ureters, urinary bladder, and urethra. The kidneys filter the blood to remove wastes and produce urine. The ureters, urinary bladder, and urethra together form the urinary tract.

Anatomy of Urinary system.

Kidneys:The kidneys are a pair of bean-shaped organs found along the posterior wall of the abdominal cavity. The kidneys filter metabolic wastes, excess ions, and chemicals from the blood to form urine.The kidneys remove urea from the blood through tiny filtering units called nephrons. Urea, together with water and other waste substances, forms the urine as it passes through the nephrons and down the renal tubules of the kidney.

Two ureters. These narrow tubes carry urine from the kidneys to the bladder. Muscles in the ureter walls continually tighten and relax forcing urine downward, away from the kidneys. If urine backs up, or is allowed to stand still, a kidney infection can develop. About every 10 to 15 seconds, small amounts of urine are emptied into the bladder from the ureters..

Bladder. This triangle-shaped, hollow organ is located in the lower abdomen.The bladder's walls relax and expand to store urine, and contract and flatten to empty urine through the urethra. The typical healthy adult bladder can stretch to hold anywhere from 600 to 800 milliliters of urine.

Urethra: It is the tube through which urine passes from the bladder to the exterior of the body. The female urethra is around 2 inches long and ends superior to the vaginal opening. In males, the urethra is around 8 to 10 inches long and ends at the tip of the penis. The urethra is also an organ of the male reproductive system as it carries sperm out of the body through the penis.

Urinary System Physiology:

The kidneys maintain the homeostasis of several important internal conditions by controlling the excretion of substances out of the body.

Ions:The kidney can control the excretion of potassium, sodium, calcium, magnesium, phosphate, and chloride ions into urine. In cases where these ions reach a higher than normal concentration, the kidneys can increase their excretion out of the body to return them to a normal level. Conversely, the kidneys can conserve these ions when they are present in lower than normal levels by allowing the ions to be reabsorbed into the blood during filtration.

pH:The kidneys monitor and regulate the levels of hydrogen ions (H+) and bicarbonate ions in the blood to control blood pH. The kidneys excrete excess H+ ions (whoch accumulate as a result of metabolism) into urine for elimination from the body. The kidneys also conserve bicarbonate ions, which act as important pH buffers in the blood.

Osmolarity:The kidneys maintain the body’s osmotic balance by controlling the amount of water that is filtered out of the blood and excreted into urine. When a person consumes a large amount of water, the kidneys reduce their reabsorption of water to allow the excess water to be excreted in urine. This results in the production of dilute, watery urine. In the case of the body being dehydrated, the kidneys reabsorb as much water as possible back into the blood to produce highly concentrated urine full of excreted ions and wastes. The changes in excretion of water are controlled by antidiuretic hormone (ADH) which helps the body retain water.

Blood Pressure:The kidneys monitor the body’s blood pressure to help maintain homeostasis. When blood pressure is elevated, the kidneys can help to reduce blood pressure by reducing the volume of blood in the body by reducing the reabsorption of water into the blood and producing watery, dilute urine. When blood pressure becomes too low, the kidneys can produce the enzyme renin to constrict blood vessels and produce concentrated urine, which allows more water to remain in the blood.

Filtration:Inside each kidney are around a million tiny structures called nephrons that filters blood to produce urine.

Storage and Excretion of Wastes:After urine has been produced by the kidneys, it is transported through the ureters to the urinary bladder. The urinary bladder when filled send signals to the brain and spinal cord. These signals result in the relaxation of the involuntary internal urethral sphincter and the sensation of needing to urinate. Urination may be delayed as long as the bladder does not exceed its maximum volume, but increasing nerve signals lead to greater discomfort and desire to urinate.

Production of Hormones:The kidneys produce and interact with several hormones that are involved in the control of systems outside of the urinary system.

Example: 1. Calcitriol which is the active form of vitamin D in the human body. 2. Erythropoietin, also known as EPO, is a hormone that is produced by the kidneys to stimulate the production of red blood cells