The anatomy of the renal system covers 4 major related structures, namely the kidneys, the ureters, the bladder and the urethra. The renal system provides a way for metabolic wastes and excess ions to be filtered out of the blood along with water. Filtered product is then excreted as urine.
Functions of the Kidneys
- Excrete waste through urine
- Regulate blood volume and blood composition – blood pH and solute concentration
- Regulate blood pressure through renin secretion
- Synthesise glucose through gluconeogenesis
- Release renal erythropoeitic factor
- Participate in Vitamin D synthesis
Blood Supply of the Kidneys
Kidney and Nephron Anatomy of the Renal System
The nephron is the main functional unit of the kidney.
There are 2 types of nephrons:
- Cortical Nephron – has its glomerulus in the outer cortical zone, with its remaining part rarely penetrating the medulla. Cortical Nephrons amount to approximately 80% of all nephrons.
- Juxtamedullary Nephron (juxta = near) – has its glomerulus close to the corticomedullary junction, with its other parts penetrating deeply into the medulla. Juxtamedullary Nephrons amount to approximately 20% of all nephrons.
The nephron consists of:
- The Renal Corpuscle – consists of the Glomerulus and the Bowman’s Capsule, both of which help in the filtration of the blood plasma
- The Renal Tubule – consists of the Proximal Convoluted Tubule, the Loop of Henle and the Distal Convoluted Tubule, all of which allow the filtered fluid to pass through
The Bowman’s Capsule
The Endothelial-Capsular Membrane
The endothelial-capsular membrane is the most important aspect of the renal system in which most of the filtration takes place. It filters water and solutes in the blood. Large molecules eg. proteins and formed elements in the blood, are usually unable to pass through it, whilst the water and solutes which are filtered out of the blood pass into the capsular space, and then into the renal tubule.
The Proximal Convoluted Tubule
The proximal convoluted tubule is found in the cortex of the kidney. It reabsorbs 85% of water and sodium chloride as well as glucose which are present in the filtrate, resulting in a reduction in volume, yet no change in the osmolality of the filtrate.
The Ureters
The Ureters are 25-30cm long with a diameter of 1-10mm. These transport urine from the renal pelvis to the urinary bladder through peristaltic (1-5/min) contractions of the muscular walls of the ureters, with additional help by gravity and hydrostatic pressure.
The Urinary Bladder
The urinary bladder is a hallow distendible muscular organ that holds about 700-800ml of urine.
NOTE: In stress incontinence, the responsible muscle is called the external urethral sphincter. This is the same muscle which is trained in pelvic floor exercises.
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Claire is keen about public education on health-related subjects as well as holistic patient-centered care. She is also passionate about spreading awareness on the negative effects that domestic abuse leaves on its victims’ mental, emotional, social and physical wellbeing.
Claire aspires to continue studying following completion of her Nursing Degree, because she truly believes in lifelong education.
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