It is important to store certain secretions until they are used in the body. To store these secretions, certain organs are needed, and which indeed are very much useful for the continuation of certain biological processes. Gallbladder and bladder are two such organs, which store different secretions in the body. Depending on their storing substances, their anatomy and physiology vary widely, and which will be discussed in this article, in detail.
Gallbladder is a pear-shaped sac which is made up of a mucous membrane, a fibromuscular coat, and a serous layer. It lies in a depression of the posterior surface of the liver. Gallbladder is 7-10 cm long in an average person. The mucous membrane of the gallbladder has tall columnar epithelium cell line, and its mucosa is highly folded. These folds are referred to as rugae. The fibromuscular layer is composed of connective tissues and smooth muscle fibers.
The main function of the gallbladder is to store and concentrate the bile, which is produced by the liver. When required, bile is discharged into the duodenum by the contractions of smooth muscle fibers. These contractions are stimulated by a hormone called CCK, which is released to blood when the food enters duodenum. The mucosa of the gallbladder absorbs water and ion in the bile in order to concentrate it.
Urinary bladder is a part of the urinary system that stores urine produced by kidneys until urination takes place. It is found anterior and inferior to the pelvic cavity and posterior to the symphysis pubis. Bladder receives urine through ureters, the small tubes connecting two kidneys and the urinary bladder.
Usually, the bladder can hold a volume of 150 mL to 500 mL urine before pain receptors are initiated. When urine enters, the bladder begins to stretch. When it reaches a certain extent, there are stretch receptors in the bladder which pass signals to the brain to let the person know that the time has come for urination. This signal generates again and again until the urination takes place.
The bladder is held tightly by a muscle called internal urethral sphincter muscle. This muscle is made up of smooth muscles, and thus it is involuntary muscle. Reaching the volume about 500 mL causes internal sphincter muscle to open because of the pressure build up in the bladder. However, there is another sphincter called external urethral sphincter located about 2 cm distal in the urethra. It is made up of skeletal muscles, thus voluntary and helps to control the urination to a certain extent even though the pain receptors are already being activated.
What is the difference between Gallbladder and Bladder?
• Bladder stores urine, whereas gallbladder stores bile.
• Bladder receives urine from kidney, whereas gallbladder receives bile from the liver.
• Bladder is in the pelvis and a part of the urinary system, whereas gallbladder is in the abdomen and a part of the digestive system.
• External and internal urethral sphincter muscles in the bladder help to control the urination, whereas smooth muscle fibers in the fibromuscular layer control the bile ejection.
You may also be interested in reading:
1. Difference Between Gallstones and Kidney Stones
2. Difference Between Bladder and Kidney Infection