Micturition - Urination Process

Introduction

Different processes take place inside the body for proper functioning. As a result of various processes happening inside our body, metabolic wastes will be produced and are needed to be removed. Excretion helps in the removal of unwanted substances from our bodies. The kidney is considered to be the primary excretory organ. Its main function is to filter the blood and remove excretory products, especially urea in the form of urine. A pair of ureters come out from each kidney that transports urine to the urinary bladder. From the urinary bladder, the urethra arises helping the bladder to expel urine. The process of removal of urine from the urinary bladder is known as micturition.

Micturition

The process of removal of urine from the urinary bladder is known as micturition. A pair of the ureter transports urine to the urinary bladder from the kidneys. The urine is stored in the urinary bladder. The stretch receptor that is present in the wall of the bladder gets stimulated as the bladder become full. Generally, when the volume of urine reaches approximately 250 ml, the stretch receptor becomes stimulated. As the bladder become full the tendency to urinate increases which results in a micturition reflex. Due to micturition reflexes sometimes involuntary urination may occur. The bladder expels the urine with the help of the urethra.

Children and adults have considerable control over urination. They are able to increase, decrease or stop their urination as per their wish. So micturition is known as a simple reflex.

Physical Properties of Micturition

The physical properties of micturition are listed below −

• Colour: Yellow.

• Volume: 1 - 1.5 liters per day.

• pH : 5 to 8.

• Odor: Ammonia-like/faint smell.

• Specific gravity: 1.003 to 1.035.

The above properties may vary depending upon the diet of a person.

Chemical Composition of Urine

Urine contains 95% water and it's an aqueous solution. The other constitutes of urine are listed below.

• Urea 9.3 g/l

• Sodium1.17 g/l

• Chloride 1.87 g/l

• Creatinine 0.670 g/l

• Potassium 0.750 g/l

Apart from these ions, organic and inorganic compounds are also present in trace amounts. Till the urine is transported to the urethra, the urine is sterile in nature.

Process of Micturition

The micturition process is constituted of two phases that are listed below.

Storage Phase

• The storage organ of the excretory system is the urinary bladder.

• The urinary bladder is a sac-like muscular structure located in the lower abdomen.

• Urine deposits in the urinary bladder.

• The shape and size of the urinary bladder depend upon the amount of urine present in it.

• The pressures it receives from its adjacent organs also affect the size and shape of the bladder.

• The urinary bladder can able to hold a 16-ounce volume of urine for approximately 2 -5 hours.

• The urine leakage is controlled by a special type of circular sphincter muscles.

• The bladder expels the urine with the help of the urethra.

Voiding Phase

• As the bladder become full, the tendency to urinate increases.

• The brain sends signals to the urinary bladder to contract.

• The receptor of the urinary bladder sends signals to the central nervous system.

• In response to this CNS sends a signal to encourage contraction of the bladder.

• The bladder expels the urine with the help of the urethra and this process is known as micturition.

• The synaptic mechanism is known as the micturition reflex.

Problem or Diseases of Micturition

There are various physical as well as physiological factors that affect micturition. Some of the diseases of micturition are listed below.

• Detrusor instability − In this conduction, the detrusor muscles contract without any specific reasons. As a result, due to detrusor instability, the affected individual lose voluntary control over urination. The main function of detrusor muscles is to contract the bladder when required. And it also helps in the process of micturition.

• Urinary retention − In this condition, the affected individuals are unable to empty the urinary bladder completely. There are different causes for urinary retention like muscles of the bladder being weak, nerve problems, and urethra blockage.

• Spinal cord trauma − Injury to the spinal cord due to an accident or any other health-related issue causes malfunction of the urinary bladder. That causes urinary incontinence.

• Frequent urination − In this, the bladder fails to hold the urine. Frequent urination may be due to various problems like problems related to the kidneys, individual suffering with fever, pain in the abdomen, and urinary tract infection. Frequent urination can happen in case of diabetes, prostate problem, and during pregnancy period.

Treatment

The treatment of micturition is described below.

• Bladder retaining − In this, the affected individuals should try to avoid urinating frequently. This helps the retention capacity of the urinary bladder.

• Diet modification − Food that contains high-quality caffeine, carbonated drinks, artificial sweeteners, etc., should be avoided.

• Kegel exercise − This exercise helps the muscles that are present in the urethra and urinary bladder.

• Surgery − In case of any blockage in the excretory system then surgery is found to be helpful.

• The nerve pathway to the urinary tract should function normally.

Important Facts

The important facts of micturition are listed below.

• The collecting duct from the nephrons collects urine and transports it into the renal pelvis and ureters.

• The contraction of smooth muscles that are present in ureters expedites micturition.

• The urinary bladder is a sac-like muscular structure located in the lower abdomen. Urine deposits in the urinary bladder.

• The bladder expels the urine with the help of the urethra.

Conclusion

The process of removal of urine from the urinary bladder is known as micturition. A pair of ureter transports urine to the urinary bladder from the kidneys. The urine is stored in the urinary bladder. The bladder expels the urine with the help of the urethra.

FAQs

Q1. How do healthy food habits keep the kidney healthy?

Ans. We should take a healthy diet with a low intake of sodium, fat, and cholesterol. Eating green vegetables, fruits, whole grains, low-fat dairy, and lean meats keep our kidneys healthy.

Q2. What do you understand by nephrons?

Ans. The kidney is composed of approximately one million tiny tubular structures. These tubular structures are known as uriniferous tubules or nephrons.

Q3. What is diabetes?

Ans. Diabetes is a condition when the glucose level in the blood increases. Diabetes is caused due to our lifestyle, food habit, and very rarely due to heredity.

Q4. Why water is essential for the proper functioning of the kidney?

Ans. Water helps the kidney to remove wastes from the blood in the form of urine. If we do not drink enough water it leads to urinary tract infections and kidney stones.

Q5. What is a urinary tract infection?

Ans. Urinary tract infection is an infection in the organs of the urinary system. UTI can occur in the kidneys, ureters, urethra, and urinary bladder.