23 Sept 2016

Urinary system anatomy

Excretory System is a group of organs that performs the function of excretion of metabolic waste from the body. The lungs, Skin, Large intestine and urinary system are different excretory systems.


The urinary system maintains the state of homeostasis by regulating water and solutes in the human body.


The Urinary System:  The Kidneys, the ureters, the bladder and urethra.


THE KIDNEYS are a pair of organs located in the retroperitoneum/back (Posterior wall) of the abdomen. The main function is to filter the blood. They create urine (Urine is composed of components like urea, water, ions and toxic wastes) as the end product which drains down to the bladder by a tube-like structure called ureters.


Cortex is the outer region and medulla is the inner area of the kidney. Renal pyramids are triangular structures that are found within the medulla.


The minor calyces are a funnel-shaped structure that surrounds the tip of each pyramid. The minor calyx integrates to constitute the major calyx.

The renal pelvis is the large collecting funnel that is formed by a bunch of major calyx. 


Nephrons -
 Functional unit of the kidney produces urine in the process of removing waste and excess substances from the blood. There are about 1 million units in each kidney.

        A. Glomeruli:  
Cluster/ball of capillaries, with the filtering membrane forms Bowman’s capsule.

        B. Renal tubules

                -    Proximal convoluted tubule (PCT)

                -    Descending and ascending - loop of Henle

                -    Distal convoluted tubule (DCT)

                -    Collecting tubule

URETERS: Carry urine from renal pelvis to the bladder. Two tubes about 15-18 inches long ½ inch diameter. Ureteral orifice (at bladder), prevents reflux of urine in ureters and the renal pelvis.

BLADDER: Muscle sac in the pelvis, just behind the pubic bone that receives and stores urine, approximately 250 ml. of urine until excreted from the body through the urethraIt is called voiding or micturition (emptying bladder).


Bladder has Internal sphincter (involuntary) & External sphincter (voluntary by training). Apex (trigone top) and Neck (lower part supported by ligaments).  


URETHRA: It is a tube that connects the bladder to genitals for the expulsion of urine, semen etc out of the body. In a female, it is located just above the vaginal opening.

For a female it is about 1 to 1 ½ inches long; urinary meatus located between the clitoris and the vagina.  

Male it is about 8 inches long, passes from bladder through the prostate gland and the penis to the meatus located at the end of the penis carries both urines and semen.

Common Diseases of Excretory System:


     1.   Pyelonephritis - Inflammation of the kidney due to a bacterial infection.

     2.   Glomerulonephritis - is inflammation of the glomeruli, which are structures in your kidneys that are made up of tiny blood vessels.

     3.   Nephrolithiasis – Kidney stones is a disease affecting the urinary tract. Kidney stones are small deposits that build up in the kidneys, made of calcium, phosphate and other components of foods. Kidney stone formation may result when the urine becomes overly concentrated.

     4.   Acute renal failure - A condition in which the kidneys suddenly can't filter waste from the blood that develops within 7 days.

     5.   Chronic renal failure - is a progressive loss in kidney function over a period of months or years

     6.   End-stage renal disease - is the final stage of chronic kidney disease in which the kidneys no longer function well enough to meet the needs of daily life.

     7.   Diabetic nephropathy - is damage to your kidneys caused by diabetes.

     8.   Hypertensive nephropathy - is a kidney disease that occurs as a result of high blood pressure.

     9.   Renal cyst - are sacs of fluid that form in the kidneys.

     10.   Urinary Tract Infection - An infection in any part of the urinary system, the kidneys, bladder or urethra

     11.   Cystitis - is inflammation of the bladder, usually caused by a bladder infection

     12.   Bladder cancer – Is an abnormal growth of cells in the bladder. 

Common signs and symptoms:


         1. Anuria

         2. Dysuria

         3. Oliguria

         4. Nocturia 

         5. Hematuria



1. Kidney                 - Nephro / Reno


2. Bladder                - Cysto / Vesico

3. Renal pelvis        - pyel/o



1. ARF - Acute renal failure

2. ESRD - End-stage renal disease

3. ESWL - Extracorporeal shockwave lithotripsy

4. GFR - Glomerular filtration rate

5. GU - Genitourinary

6. KUB - Kidneys, ureters, bladder

7. UA - Urinalysis

8. UPJ - Ureteropelvic junction

9. UTI - Urinary tract infection


Test your Knowledge:

                    A. Excretory System Quiz