Chapter 23, Problem 1TYR

Summary Introduction

Introduction:

Metabolism of human body inevitably produces a variety of unwanted or waste products. This waste product is not simply needed by the body. If it is allowed to accumulate in the body, it may produce harmful effects. These wastes are completely excreted from our body, through digestive tracts, respiratory tracts, and by the sweat glands. The principal system that involved in the excretion of waste is the urinary system. From the blood, the metabolic waste is removed by the kidney. The rest of the urinary system involves in the elimination of urine, storage, and for transport. The kidney plays an important role in regulating the blood pressure and blood volume. Kidney physiology is administrated by certain principles. This includes osmotic pressure, down pressure, and electrochemical gradients. The stages of urine production and the role of the kidney (regulating urine concentration and fluid balance) is mainly depends on concepts like osmolarity, tonicity, and osmosis.

Answer to Problem 1TYR

Correct answer:

Micturition occurs when the detrusor contracts. Therefore, option a is correct.

Explanation of Solution

Justify reasons for the correct statement:

When the bladder is getting filled with the urine, it is essential for the urethral sphincters to be closed and the detrusor to relax. This occurs by the sympathetic pathways, which is originating from the upper lumbar spinal cord. The process of micturition is also called as “voiding”.  The act of micturition can be controlled by micturition reflex.

Option (a) is given as, “detrusor”.

The bladder is filled with the urine when the detrusor get relaxed. But, the contraction of the sphincters occurs in order to ensure retention of the urine (in bladder) until the volunteer make null.

Hence, option (a) is correct.

Justify reasons for the incorrect statements:

Option (b) is given as, “internal urethral sphincter”.

In men, the neck of the bladder and urethra is encircled by a smooth muscle. The sympathetic nervous system is abundantly innervated and gets thickened into a collar of muscle, which is called as the internal urethral sphincter. During ejaculation, it prevents the reflux of semen into the bladder. Hence, it is a wrong answer.

Option (c) is given as, “external urethral sphincter”.

An external urethral sphincter is present in both sexes. It is of skeletal muscle that surrounds the urethra where it moves through the pelvic floor. The voluntary control (voiding of urine) is delivered by the external urethral sphincter. Hence, it is a wrong answer.

Option (d) is given as, “muscularis of the ureter”.

It is one of the three layers of the ureter. The draining of the urine from the renal pelvis to the bladder is achieved by a peristaltic wave, which is initiated by the muscularis of the ureter. Hence, it is a wrong answer.

Option (e) is given as, “all of the above”.

The micturition occurs when the detrusor contracts. Hence, it is a wrong answer.

Hence, options (b), (c), (d), and (e) are incorrect.

Conclusion

Micturition happens when parasympathetic stimulates detrusor to contract.