Question

Explain the structures and functions of the urinary system, make certain to include critical processes for urine production.

Answer 1

Urinary system is composed of:

1) Kidney: These are bean shaped retroperitoneal organs consiting of nephrons:

Kidney functions:
- urine formation :- The Three process of Urine Formation
1)Filtration,
2)Reabsorption,
3)Secretion

-Synthesis of vitamin D
- secretion of Renin to regulate blood pressure and GFR
-Secretion of Erythropoietin to regulate Erythropoiesis.
-Regulation of acid base balance and osmoregulation.

2) Ureter: It is long tubular structure that conducts the urine form kidney to the bladder.

3) Urinary Bladder: Is is muscular bag like structure that stores the urine for a period of time.

4) Urethra: It conducts the urine to outside of the body.

The Three Steps of Urine Formation
1)Filtration,
2)Reabsorption,
3)Secretion

The kidneys filter unwanted substances from the blood and produce urine to excrete them. There are three main steps of urine formation: glomerular filtration, reabsorption, and secretion. These processes ensure that only waste and excess water are removed from the body.

1. The Glomerulus Filters Water and Other Substances from the Blood:
Each kidney possess over 1 million tiny structures called nephrons. Each nephron has a glomerulus, the site of blood filtration. The glomerulus is a network of capillaries surrounded by a cuplike structure, the glomerular capsule (or Bowman’s capsule). As blood flows through the glomerulus, blood pressure pushes water and solutes from the capillaries into the capsule through a filtration membrane. This glomerular filtration begins the urine formation process.

2. The Filtration Membrane Keeps Blood Cells and Large Proteins in the Bloodstream:
Inside the glomerulus, blood pressure pushes fluid from capillaries into the glomerular capsule through a specialized layer of cells. This layer, the filtration membrane, allows water and small solutes to pass but blocks blood cells and large proteins. Those components remain in the bloodstream. The filtrate (the fluid that has passed through the membrane) flows from the glomerular capsule further into the nephron.

3. Reabsorption Moves Nutrients and Water Back into the Blood:
The glomerulus filters water and small solutes out of the bloodstream. The resulting filtrate contains waste, but also other substances the body needs: essential ions, glucose, amino acids, and smaller proteins. When the filtrate exits the glomerulus, it flows into a duct in the nephron called the renal tubule. As it moves, the needed substances and some water are reabsorbed through the tube wall into adjacent capillaries. This reabsorption of vital nutrients from the filtrate is the second step in urine creation.

4. Waste Ions and Hydrogen Ions Secreted from the Blood Complete the Formation of Urine:
The filtrate absorbed in the glomerulus flows through the renal tubule, where nutrients and water are reabsorbed into capillaries. At the same time, waste ions and hydrogen ions pass from the capillaries into the renal tubule. This process is called secretion. The secreted ions combine with the remaining filtrate and become urine. The urine flows out of the nephron tubule into a collecting duct. It passes out of the kidney through the renal pelvis, into the ureter, and down to the bladder.