Kidneys, Fluid Regulation and the Urinary System

Kidneys, Fluid Regulation and the Urinary System

Structure if a Dissected Kidney

The kidney is dissected from top to bottom, this way a clearer cross-sectional specimen can be viewed. The kidney is divided up into four main components; Renal Cortex, Renal Medulla, Sinus Arteries and Veins and Renal Pelvis and Ureter.

Renal Cortex - The renal cortex is the part of the kidneys where ultrafiltration occurs, it has blood vessels that run through the structure and are connected to nephrons.

Renal Medulla - The nephrons are found in the medulla and it is here that they are able to expel waste products which travel through the renal pyramids and calyxes to the bladder.

Major Calyx - Connecting two or three minor calyxes to the ureter.

Papilla of Pyramid - The papilla is the apex tip of the renal pyramid, it faces in towards the kidney and channels waste products to the renal calyxes.

Minor Calyx - This part connects the apexed end of the pyramid (papilla) to the ureter, similar to branches the major calyx has multiple minor calyxes connected.

Ureter - The ureter is the long descending tubule that connects the renal medulla to the bladder.

Renal Pyramid in Renal Medulla - These are conical shaped tissues in the renal medulla where waste products move out from the nephrons.

Renal Column - A thick wall between each renal pyramid increasing the structure of the renal cortex.

Fibrous Renal Capsule - A thick fibrous membrane along with a thick perinephric adipose layer help protect the kidneys from damage while moving.

The Kidney Structure

Ultra Structure of the Nephron

Nephrons are a micro-structure in the kidneys where ultrafiltration occurs. Blood from the renal arteries travels to the glomerulus where a difference in potentials causes water, salts and other products to move out of the blood vessels into the bowman's capsule through diffusion.

Afterward the products travel down the first coiled tubule. The tubule is intertwined with a capillary network which is designed to help reabsorb water and other needed products. From here anything left in the tubule moves into the loop of henle. Here more and more water is diffused out of the tubule creating a salty environment as it reaches the bottom of the loop. From here the water potential is very low and salts are able to more readily move back into the blood vessels. As the remaining products enter the second tubule anything that is still able to be successfully reabsorbed is taken up.

The collecting duct has hormone triggered aquaporins which allow for active diffusion of water re up take.

The structure of the kidney is simply to remove excess products from the body. These products might be important to normal function but is excess can cause their own problems such as an excess of water interrupts osmotic diffusion.

These products are filtered out from the blood stream into nephrons which then, after partial reabsorbtion, transport the excess waste products to the medulla. From there the waste products move to the bladder via the ureter ready to be excreated from the body.

The kidneys play a vital role in the body as a whole as they enable us to filter out excess water, salts and other waste or excess products helping our body to self regulate its environment.

Without the kidneys a person isn't likely to survive more than a couple of days as toxins build up in the blood essentially poisoning itself.