Anatomy and Physiology – The Urinary System

Humans have the capacity to excrete toxins. For instance, the urinary system is major excretory system of the body. It helps in homeostasis specifically in electrolyte balance, fluid balance and acid-base balance. All by products of chemicals and food as well as preservatives may pass the kidney and be excreted in a form of urine.

Parts of the Urinary System

1. Kidneys – Two-red bean shaped organs that filters the water and chemicals that enters the body and excretes it as a urine
2. Ureters – Two tubes that transport urine to the urinary bladder
3. Urinary Bladder – A hollow organ that stores the urine
4. Urethra – It is a muscular tube that brings out the urine

Anatomy of Kidneys

The kidneys are anatomically located on the abdominal cavity. Each kidney approximately measures 11.25 long, 5.5 to 7.5 cm. wide and 2.5 cm thick. The kidney is embedded retroperitoneal in an adipose and fibrous capsule.

In a close look, the kidneys have the following surface:

1. Renal Cortex – You can find the capillary tufts and convoluted tubules
2. Renal Medulla – the inner portion wherein the renal pyramids are found
3. Renal Papilla – The minor calyx or calyces join together to form the major calyx. The major calyx connects to the ureter.

The kidneys originate on the metanephros. On the fifth week of development, the metanephros gives rise to two mesodermal sources: ureteric bud and metanephrogenix mass. Aside from the metanephros, the pronephros serves as the kidneys on the fourth week of gestation until the sixth week.

Anatomy of Urinary Bladder

The urinary bladder is anatomically located above the next to symphysis pubis while it is before the rectum. It stretches according to the volume of urine that must be excreted. It has four layers: from the innermost – mucosa, submucosa, muscularis and serosa.

In a closer look, the layers of the urinary bladder functions to adjust on the urine content that is supposed to be delivered out from the body. The mucosa allows distension of the bladder. The submucosa is vascular in nature; therefore it supplies blood around the bladder. The muscularis is the smooth muscle wall that helps in the biological process of passing out urine or micturition. The serosa on the other hand is made of simple squamous epithelial cells.

Anatomy of Nephron

Nephrons serve as the urine-forming unit of the kidney. It contains glomerulus, glomerular capsule, proximal convoluted tubule, nephron loo or loop of Henle and distal convoluted tubule.

Basic components of Kidney Function

1. Glomerular filtration – is the term given to a process that fluid and solutes in the blood plasma pass into the glomerular capsule.1. A
2. Glomerular filtration rate – is the rate of the filtration capacity of kidneys in minutes. The GFR differs in sex. For females, the average GFR is 110ml/min while for males, it is 125 ml/min.
3. Tubular reabsorption – The filtrate is approximately 99% actively or passively transported from the lumen into the interstitial fluid.
4. Tubular secretion – The peritubular capillaries takes in noxious substances.

Trivia:

Urination and Micturition are different by definition. Urination is the act of passing out the urine from the urinary bladder while micturition includes the physiologic process of voiding.

Kidneys regulate the concentration of the urine through the antidiuretic hormone or ADH being secreted from the posterior pituitary glands.

Some terms related with urinary system:

1. Acute renal failure
2. Azotemia
3. Blood Urea Nitrogen
4. Chronic renal failure
5. Cystitis
6. Cystoscopy
7. Glomerulonephritis
8. Hematuria
9. Hemodialysis
10. Nephrolithiasis