Biology [3 marks Question Answer]

Solution is as follow:

Solution is as follow:

Constituents of Urine: The normal human urine consists of about 95% of water and 5% of solid wastes dissolved in it. The percentage of the solid wastes may slightly vary according to the food taken and according to the time after taking food but usually, these are approximately as follows:

Organic Constituents in (g/L)	Inorganic Constituents in (g/L)
Urea — 2-3	Sodium chloride — 9-0
Creatinine — 1-5	Potassium chloride — 2-5
Uric acid — 0-7	Sulphuric acid — 1-8
Others — 2-6	Ammonia — 0-6
	Others — 2-5

Besides the normal constituents the urine may pass out certain hormones and also certain medicines like the antibiotics and the excess vitamins.

In a nephron, the blood .enters by afferent arteriole and is filtered through the glomerulus. The filtrate is passed into the Bowman’s capsule; by the process called ultrafiltration. The filtrate contains useful products like glucose, amino acids, salts, etc. The plasma proteins, blood corpuscles, and platelets are retained in the glomerular mass. The filtrate now passes through Henle’s loop where selective reabsorption of useful products takes place but urea and uric acid are not absorbed. Now the excretory substances are secreted by proximal and distal convoluted tubule and urine is formed.

Dialysis involves the use of artificial kidney or a dialysis machine. The patient's blood is from the radial artery is led through the machine where excess salts and urea is removed. The purified blood is then returned to a vein in the same arm.
Dialysis is carried out in case of failure of both the kidneys. In case there is a permanent damage, then the dialysis is to be repeated for about 12 hours twice a week.

Urinary bladder: It lies at the base of the abdomen and has a thin, elastic, and muscular wall. The urinary bladder receives the urine from the ureter. The wall of the bladder relaxes and the bladder expands to hold and store the urine, The urine cannot flow out continuously because of the contraction of the right sphincter muscles at its junction with the urethra. When the bladder is full, it contracts and the ring of sphincter muscles relaxes so that the urine is forced out through the urethra.

Loop of Henle: The cells that comprise the loop of Henle are well-adapted for diffusion, filtration, and selective reabsorption. The final changes in the composition and the volume of the nephric filtrate occurs in the loop of Henle and the distal convoluted loop of the tubule. Glucose, amino acids, water, mineral salts, and some other substances leave the loop of Henle to pass into the blood capillaries that surround it.

Glomerulus: A single afferent arteriole of the renal artery breaks up into a number of capillary branches to form the glomerulus. The blood in the glomerulus is subjected to higher pressure since the diameter of the afferent arteriole is wider than that of the efferent arteriole that leaves the glomerulus, so ultra-filtration takes place.

The Bowman’s capsule is also called the Nephric capsule and represents the free end of the nephron. The Bowman’s capsule is a double-walled cup-like structure which lies in the cortex of the kidney. The glomerular filtrate which leaves the blood capillaries of the glomerulus during ultrafiltration enter the capsule and then passes to the first part of the nephric tubule.

(i) Renal cortex
(ii) 1. Afferent arteriole
2. Glomerulus
3. Bowman capsule
(iii) Ultrafilteration, reabsorption, and tubular secretion.
(iv) Ultrafilteration: In it blood entering the glomerulus under great pressure, is filtered. The liquid part of the blood filters through the walls of glomerular capillaries and Bowman’s capsule and enters into the nephron where it is called the glomerular filterate.

(i)
(1) Renal artery,
(2) Aorta,
(3) Renal arteries,
(4) Renal vein
(ii)
(5) Ureter—Carry urine to the bladder.
(6) Urinary bladder—Store urine
(7) Sphincter muscle—Control the voiding of urine
(8) Urethra—Urine released periodically.
(iii) Adrenal gland—At the top of kidney.

(i)

1 – Collecting duct
2 – Distal convoluted tubule (DCT)
3 – Descending limb of loop of Henle
4 – Bowman’s capsule

(ii) The diameter of efferent arteriole is narrower than the diameter of the afferent arteriole which builds the high hydrostatic pressure in the glomerulus.

(iii) Efferent arteriole

(iv) The two main stages of urine formation are ultrafiltration and tubular reabsorption.

(v) Henle’s loop and collecting tubules