Human Excretion and Kidney Physiology

As blood enters your kidneys, it is filtered by glomerulus. The ultrafiltrate produced by the glomerulus initially contains small molecules like water, glucose, amino acids, bicarbonate, urea, and creatinine as well as ions such as potassium, sodium, chloride, calcium, and phosphate. All of this filtrate is channeled from the Bowman's space inside of the Bowman's capsule into the long series of ducts in the nephron, which are collectively called the renal tubule. During this journey, many things will be added and subtracted to and from the ultrafiltrate by the cells lining these ducts in order to finally form the urine.  After this the tubular fluid leaves the renal tubules and passes to the collecting duct system, which connects the nephron to the ureter. Urine then enters the urinary bladder ( which collects waste excreted by the kidneys prior to disposal by urination) via the ureters and exits via the urethra.

"Uriniferous tubule" or "nephron" are the structural and functional unit of kidney. It is present in the outer firm region of kidney, the renal cortex. It consist of renal corpuscle and a long renal tubule. 

The functional unit of the kidney is the uriniferous tubule, a highly convoluted structure that modifies the fluid passing through it to form to form urine as its final output. This tubule consists of two parts, the nephron and the collecting tubule.

Malpighian tubule, in insects, any of the excretory organs that lie in the abdominal body cavity and empty into the junction between midgut and hindgut. The tubule cells actively transport initial urine constituents (potassium ions, water, urate ions, sugar, amino acids) into the tubule. In some species urine is acidified in the distal end of the tubule and an aqueous suspension of uric acid crystals is conducted into the rectum, where water and nutrients are reabsorbed. In other species the urine is acidified in the rectum. Certain tubule cells may have special functions, as in the secretion of the sticky substance that surrounds eggs of certain leaf beetles or in the secretion of silk by certain immature beetles. Thus, option A is correct.

A malpighian tubule empties its content into the gut. Malpighian tubule, in insects, any of the excretory organs that lie in the abdominal body cavity and empty into the junction between midgut and hindgut. In species having few malpighian tubules, they are long and coiled; in species with numerous (up to 150) tubules, they are short. The tubule cells actively transport initial urine constituents (potassium ions, water, urate ions, sugar, amino acids) into the tubule. In some species urine is acidified in the distal end of the tubule and an aqueous suspension of uric acid crystals is conducted into the rectum, where water and nutrients are reabsorbed. In other species the urine is acidified in the rectum. Certain tubule cells may have special functions, as in the secretion of the sticky substance that surrounds eggs of certain leaf beetles or in the secretion of silk by certain immature beetles.

Malpighian body is found in the kidneys of the vertebrates. It is also called kidney corpuscle and is composed of a glomerulus and the Bowman's capsule. It is concerned with the filtration of the blood and forms the glomerular filtrate. In insects, the malpighian tubules are present for the excretion.

Urine is formed in the kidney. The tubes which connect the kidney and urinary bladder are known as the ureter. From the kidney, urine is propelled into the urinary bladder through ureters which are made of smooth muscle fibres. The bladder stores urine, allowing urination to be infrequent and can be controlled. The urethra is a long tube which connects urinary bladder to the urinary meatus for removal of urine from the body. In males, urethra travels through the penis and meet the urethral meatus located at the tip of the penis. In females, urethra connects to the urethral meatus above the vagina. The urethra is also known as the urinary opening. Hence the opening of urinary bladder is urethra.

Each human kidney contains approximately 1 million nephrons, so two kidneys contain approximately 2 million nephrons.

Filtration takes place through semipermeable walls of glomerulus and Bowman's capsule. Glomerulus and Bowman's capsule are collectively called malpighian corpuscle.

In humans, the Kidney is the excretory organ. Nephron or uriniferous tubule is the structural and functional unit of the kidney. On an average, 25-30 gm of urea is excreted out per day through urine. Hence uriniferous tubules are mainly concerned with removal of urea from the blood.

The nephrons along with collecting ducts are called as uriniferous tubule. The nephron is the structural and functional unit of the kidney. The body of the nephron is divided into  Bowman's capsule, PCT, Henle's loop and DCT. Hence glomerulus does not belong to the uriniferous tubule. Glomerulus are the tuft of capillaries present in the Bowman's capsule.