. Human Excretory System . . Structure of Kidney Excretory system in human consists of a pair of kidneys, a pair of ureters, urinary bladder and urethra (Figure.
. ). Kidneys Most aquatic animals Birds and most reptiles, insects and land snails Mammals, most amphibians, sharks, reptiles and terrestrial invertebrates Ammonia Uric acid Urea Animals Nitrogenous wastes Figure . Excretory products in different groups of animals.
XI Std Biology-Zoology Chapter- pelvis and ureter have smooth muscles which contracts rhythmically. The calyces collect the urine and empties into the ureter, which is stored in the urinary bladder temporarily. The urinary bladder opens into the urethra through which urine is expelled out. Cortex Medulla Renal Artery Renal Vein Ureter Capsule Kidney pelvis Major calyx Renal pyramid Renal column of Bertini Minor calyx Juxtamedullary nephron Cortical nephron Figure .
L S of kidney . . Structure of a Nephron Each kidney has nearly one million complex tubular structures called nephron (Figure . ).
Each nephron consists of a filtering corpuscle called renal corpuscle (malpighian body) and a renal tubule. The renal tubule opens into a longer tubule called the collecting duct. The renal tubule begins with a double walled cup shaped structure called the Bowman’s capsule, which encloses a ball of capillaries that delivers fluid to the tubules, called the glomerulus. The Bowman’s capsule and the glomerulus together constitute the renal corpuscle.
The endothelium of glomerulus has many pores (fenestrae). The external parietal layer of the Bowman's capsule is made up of simple squamous epithelium and the visceral layer is made of epithelial cells called podocytes. The podocytes end in foot processes which cling to the basement membrane of the glomerulus. The openings between the foot processes are called filtration slits.
are reddish brown, bean shaped structures that lie in the superior lumbar region between the levels of the last thoracic and third lumber vertebra close to the dorsal inner wall of the abdominal cavity. The right kidney is placed slightly lower than the left kidney. Each kidney weighs an average of - grams. The outer layer of the kidney is covered