The Kidneys are located in the abdominal cavity, situated below the level of last thoracic and third lumbar vertebra close to the dorsal inner wall of abdominal cavity.
Each kidney is been shaped reddish brown.
The right kidney is lower and smaller than left kidney because the liver takes up much space on the right side.
From each kidney, one ureter arises, and the two Ureters open obliquely into the Urinary bladder, which is a hollow, muscular sac-like structure that stores urine.
Urethra is the membranous tube that arises from the neck of the bladder and conduct the urine to the exterior.
Each nephron has cup shaped upper end called Bowman's Capsule.It contain bundles of blood capillaries called glomerulus. The Bowman's capsule and glomerulus together form globular body called renal corpuscle.
The blood in the capillaries of glomerulus come from aorta by renal arteries and after passing through glomerulus it returns to the posterior vena cava via renal vein.The blood entering into glomerulus carries waste material which are filtered out in the Bowman's capsule.
Filtration is possible because walls of glomerular capillaries and Bowman's capsule are very thin and selectively permeable.
PROCESS OF FILTRATION
- A pair of kidneys, a pair of ureters, a urinary bladder and a urethra constitutes the human excretory system.
- Kidneys are present on either side of the backbone in the abdomen.
- Kidneys produce urine and urine from kidney passes through the ureters into the urinary bladder and remains stored their until it is released through the urethra.
- Urine is produced to filter out waste products from the blood.
- Nephrons are basic structural and functional unit of kidney.
- Cluster of thin walled blood capillaries called glomerulus in the nephron filtrate the urine and each cluster is associated with cup shaped end of a tube called Bowman’s capsule.
- Substances like glucose, amino acids, salts and a major amount of water is selectively reabsorbed from the initial filtrate as the urine flows along the tube.
- Reabsorption depends on the amount of excess water in the body and dissolved waste to be excreted.
- The urine from kidney enters the long tube called ureter.
- Ureter connects the kidney with the urinary bladder and urine from the kidney is passed to urinary bladder and stored in the bladder.
- When the pressure in the expanded bladder leads to the urge to urinate, the urine is passed out through urethra.
Excretion is the removal of waste from the body. Plants also produce waste products but very slowly and in very small amounts. They do not have any special organ for the removal of their waste product.
The waste products of a plant are carbon dioxide, water vapour and oxygen. While carbon dioxide and water vapour are waste products of respiration, oxygen is a waste product of photosynthesis. These waste products are removed through stomata in leaves and lenticels in stems and are released into the air.
Some of the waste products are stored in the leaves, bark and fruits of a plant or a tree. Trees get rid of them when dead leaves bark and ripe fruits fall off from them. Some plants store waste in their fruits in the form of solid bodies called raphides. For example, fruit yam has needle-shaped raphides on its surface. Plants also secrete waste in the form of gum and resins from their stem and branches.
Therefore, various methods used by plants to get rid of their waste products are:
- Gaseous waste through stomata and lenticels.
- Stored solid and liquid waste by shedding leaves, peeling of bark and falling of fruits.
- By secreting waste in the form of gum and resins.
- Excrete waste into the soil around them.
