Kidney Structure:
The excretory organ of the human body is the kidney. Two kidneys lie at the back of the abdominal cavity, on either side of the vertebral column and the lower part of the ribcage, attached to the back wall. They are red-brown in colour and bean-shaped. The outer side of the kidney is convex, and the inner side is concave, with an indentation called the hilus or hilum. The ureter and renal vein comes out from the hilum and the renal artery enters the kidney. Two ureters arise from each kidney, proceeding downwards to open into the urinary bladder. The funnel-shaped extended part of the ureter is called the renal pelvis.
Kidney are enclosed with a special fibrous membrane, called the renal capsule. Adjacent to the renal capsule is the cortex, and the inner side is the medulla. These regions are composed of connective tissues and blood vessels. each kidney contains a particular type of tubules called uriniferous tubule. Each uriniferous tubule has two parts, the nephron and the collecting tubule. Urine is produced in the nephron and the collecting tubules carry urine to the pelvis.
Blood vessels are closely associated with the nephrons. Each glomerulus is supplied with blood by a branch of the renal artery called an afferent arteriole. The capillaries of hte glomerulus rejoin to form an efferent arteriole. The efferent arteriole leads off to form a network of capillaries running closely alongside the rest of the nephron. Blood from these capillaries flows into a branch of the renal vein.
Function:
A normal adult man expels almost 1500 milliliter urine daily. Urine contains nitrogenous waste products, such as - urea, uric acid, ammonia, creatinine etc. These are harmful to health. The kidney plays an important role in eliminating these waste products.
a) Each nephron of the kidney is continuously producing urine through a complex process.
b) The ureter carries urine to the urinary bladder, where it is stored.
c) The renal vein carries 'clean' blood' away from the kidneys.
d) The kidneys remove urea and other wastes from blood and excrete it in a liquid called urine.
e) The bladder is a bag which stores urine until you go to the toilet.
f) The renal artery carries 'dirty' blood to the kidneys.
g) The sphincter is a ring of muscle which keeps the bladder closed until you go to the toilet.
Q. 1. What is excretion?
Ans: Excretion is the biological process through which harmful nitrogenous waste products produced by metabolic activity are removed from the body.
Q.2. Where is 'dirty' blood filtered?
Ans: Blood is filtered by the glomerulus.
Q.3. What are the excretory products?
Ans: Excretory products are mostly nitrogenous waste. Human excretory products are expelled from the body as urine. urine is almost 90% water. Other components are urea, uric acid, creatanine and different kinds of salts.
Q.4. Glucose is small enough to be filtered from the blood in glomeruli in the kidney, but is not normally found in the urine. This is because glucose is:
Ans: reabsorbed along the whole length of the nephorns