FACTS ABOUT THE URETER..WHAT DO YOU KNOW? DID YOU KNOW THAT......

THE URETER

The ureters are the tubes that carry urine form the kidney to the bladder. They are about 25cm to 30cm long with a diameter of about 3mm.  in human the ureters arise from the renal pelvis on the medial aspect of each kidney before descending towards the bladder on the front of the psoas major muscle.

The ureter runs posteroinforiorly on the lateral wall of the pelvis and curve anterior medially to enter the bladder through it posteroinferior part.  The opening of the ureter is occluded by the bladder when it is filling with urine to prevent urine from flowing back into the ureter again.

THE STRUCTURES OF THE URETERS.

The ureter has three main layers, namely:

    Tunica adventitia

    Tunica muscularies

    Tunica mucosa

The tunica adventitia is made up of the connective tissue which protects the surface of the ureter.

The tunica muscularies is found under the tunica adventitia and it is in three layers:

v outer longitudinal layer

v the middle layer which is in a circular form

v the inner most layer which is also longitudinal

The main function of the muscularies is to contract and relax to propel urine to the urinary bladder.

The tunica muscularies is also made of an epithelium layer. The function of the mucosa layer is to secrete mucus to prevent the urine from having an interaction with the muscularies.

FUNCTION OF THE URETERS

The main function of the ureter is to contract and relax to carry or propel urine from the pelvis of the kidney to the urinary bladder.

THE URINARY BLADDER

The bladder is a hollow distensible organ located at the pelvic cavity. It varies in positions, sizes and age. The bladder rises into the abdominal cavity when it fills with urine and distended.

In male the bladder is posteriorly and superiorly bounded by the rectum inferior part the abdominal wall whiles in female, it is posteriorly and superiorly bounded by the vagina and the uterus.

Generally the bladder is anteriorly bounded by the symphysis pubis and laterally by the pelvic bones.

STRUCTURE ASSOCIATED WITH THE BLADDER

The bladder is bladder is roughly pear shaped, but becomes more oval as it fills with urine. The posterior surface is the base. The bladder opens into the urethra at its lowest point the neck. The peritoneum covers only the superior surface before it turns upwards as the parietal peritoneum, lining the anterior abdominal wall. Posteriorly it surrounds the uterus in the female and the rectum in the male. The bladder wall is composed of three layers;

Ø The outer layer of loose connective tissue, containing blood and lymphatic vessels and nerves, covered on the upper surface by the peritoneum.

Ø The middle layer consisting of interlacing smooth muscle fibers and elastic tissue loosely arranged in the layers. This is called the DISTRUSOR MUSCLE and when it contracts it empties the bladder.

Ø The mucosa composed of transitional epithelium layer that readily permit the distention of the bladder as it fills with urine.

When the bladder is empty the inner lining is arranged in folds, or rugger which gradually disappears as it fills. The bladder is distensible but when it contains 300 to 400mls, aware of the need to pass urine is felt. The total capacity is rarely more about 600mls.

The three orifices in the bladder wall form a triangle or trigons. The upper two orifices on the posterior wall are the openings of the ureters. The lower orifice is the opening into the urethra. The internal urethra sphincter, a thinking of the urethra smooth muscle layer in the upper part of the urethra, controls outflow of urine from the bladder. This sphincter is not under voluntary control

FUNCTION OF THE BLADDER

The main function of the bladder is to store urine temporally before it is finally expel out of the body.

THE URETHRA

The bladder is a tube that extends from the inferior part or the neck of the bladder to the external part of the body or the external environment of the body. It is longer in male than in female. In male the urethra is associated with the reproductive organs.

In females it is about 4cm long and 6mm in diameter and about 20cm long in male.

In female the urethral runs downward and forward behind the symphysis pubis and opens at the external urethra orifice just in front of vagina under the clitoris.

The external urethra orifice is guided by the external urethra sphincter which is under voluntary control. The walls of the female urethra have two main layers, an outer muscle layer and an inner lining mucosa which is continues with that of the bladder.

 The male bladder is divided into three parts, namely the prostrate urethra, membranous urethra and the spongy or the pineal urethra

                                                                             

The Micturition Reflex

                                                                             

•         The process of urination is controlled by the micturition reflex, which is initiated by the stretch receptors in the bladder wall. The urge to urinate generally appears when the bladder contains about 200 ml of urine.

•         Voluntary urination involves coupling this reflex with the voluntary relaxation of the external Urethral sphincter which allows opening of the internal urethral sphincter.

•         At the end of a normal micturition, less than 10 ml of urine remains in the bladder.