The urinary system, the attention for synchronization

Delimitation cycle

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What gives us our humanity and differentiates us from animals is the emotions. They live in us, and turn us away from our will so easily. Misunderstood forces, which we refute because they make the impossible possible and achieve what we fear. If to live humanely, it was to look our emotions in the face, and stop hurting oneself by thinking doing good.

Imagine all the people living life in Peace.

The urinary system uses specific actions, to perform the various functions necessary to accomplish a common goal:

Localisation defines function

The nephrons are a little different in their structure depending on their location.

  • Cortical nephrons have their glomeruli in the most peripheral or middle region of the renal cortex and generally have only a short Henle’s loop;
  • The juxtamedullary nephrons which have a long Henle’s loop which sinks deep into the innermost renal medulla;
  • Juxtamedullary nephrons make up only 10 to 15% of all kidney nephrons and play an essential role in the concentration of urine.

A nephron is a functional unit of the kidney, which produces an ultrafiltrate from the blood and potentially makes up the urine.

A sequence of tasks

Each nephron has the same successive structures.

  • The glomerulus: a ball formed by the afferent arterioles, which is enclosed in the Bowman’s capsule and which is involved in the filtration of plasma;
  • The proximal convoluted tubule: following, it receives the plasma ultrafiltrate and brings it to the Henle’s loop;
  • Henle’s loop: it consists of a single long tubule, the caliber of which varies and which is covered with epithelial cells specialized in reabsorption and secretion over the entire length;
  • The distal convoluted tube: it receives the residual liquid from Henle’s loop, controls its osmolarity and transports it to the collecting tube or tubule;
  • The collecting tubule: it carries out the terminal part of the nephron where the final concentration of urine is precisely adjusted before it reaches the minor calyxes.

Each element of the nephron has a specific task which belongs to one of the following functions: transport, control, regulate.

Maintain the essentials

The volume of blood passing through each glomerulus is controlled by active nervous and hormonal mechanisms acting on the afferent and efferent arterioles.

Take the example of renal sodium and water regulation:

  • Sodium filtration is regulated at the glomerulus by the baroreceptor reflex,
  • its reabsorption is regulated at the tubular level by the stimulating effect of aldosterone (secreted by the adrenal cortex) and other factors also play a role.
  • The reabsorption of water remains linked to the movements of sodium up to the collecting tubule,
  • then, this regulation of water is subject to the control of vasopressin, the diuretic hormone (ADH for antidiuretic hormone);
  • A low level of DHA leads to diluted urine (excretion of water),
  • while a high level of DHA activates the channels for water (aquaporins) resulting in reabsorption of water and concentration of urine.
  • The counter-current vascular system (the efferent arterioles of the renal vasa recta) maintains the osmotic gradient necessary for tubular function;
  • If water retention is necessary, it will generate a hyperosmotic medullary interstitial fluid, the water reabsorption effect of which will be added to that of DHA.

It is thanks to a coordinated structure, both linear and spatial, that the urinary system is able to regulate the concentration of urine according to the needs of the organism.

Let’s use the specialization of tasks and the coordination of functions to work together for a harmonious world:

If the human body is able to know when to concentrate or dilute
a molecule to maintain the harmony of the body
through hormones or osmotic gradients;

We can define indicators to no longer exceed the limits
that our earthly life imposes on us;

Let’s find out about our limiting factors,
in order to respect them to develop us in the correctness of balance.

Bibliographic reference:
– The information on the urinary system and the pictures are taken from the book « The Netter’s Anatomy Coloring Book », John T. HANSE, Elsevier Masson SAS, 2017 (the french version)..

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