We each have two kidneys and having healthy kidneys is one of the most important ways to ensure good health as they are absolutely vital organs. Unless the kidneys efficiently and effectively remove wastes from the body these wastes will build up and cause major damage, leading to death.
It is very important as part of your detox journey that you understand the critical role they play maintaining your health. While not big (a typical kidney size is about 11cm (4.3”) long, 6cm (2.4”) wide and 3cm (1.2”) thick, each weighing approximately 150g (about 4.5 to 5 ounces)) you absolutely cannot live without them.
They are located near the middle of the back, on either side of your spine, extending from the 12th thoracic vertebra down to the 3rd lumbar vertebra where they receive some protection from the lower rib cage.
The left kidney sits usually slightly higher than the right, probably because of the large liver which space partly occupies this space also. Your kidneys are held in position by a mass of fat and other tissue that encloses them, which is comprised of three layers:
1. The innermost layer is the renal capsule, a fibrous covering on the kidney itself
2. The adipose capsule, a fatty layer, supports and protects the kidney
3. On the outside is the renal fascia a thin layer of connective tissue which anchors the kidney to surrounding structures
The adipose capsule is extremely important and especially thin people run the risk of floating kidney (nephroptosis) in which the kidney drops possibly kinking the urethra thereby causing urine to back up into the kidney. This can lead to kidney damage and even kidney failure if left untreated.
Kidneys are part of the urinary system, which is one of the main excretory systems of the body. It consists of two kidneys which filter the blood and secrete urine via the urethra which connects to the urinary bladder from where it is passed via the urethra and discharged to the exterior.
Kidneys are an intricate and extremely efficient filtration system that performs many functions to keep the blood clean and chemically balanced. The lungs and skin also have a small role in ridding the body of metabolic wastes and other toxins, but most of the heavy lifting is done by the urinary system. Understanding how the kidneys work can help a person keep them healthy.
Kidneys filter the body’s entire blood supply more than 60 times a day and removes wastes from the blood and excretes it. While the kidneys only make up less than half a percent of the body’s weight, every minute of the day they use approximately a quarter of the resting body’s cardiac output and the body’s oxygen to process a litre (~1 quart) of blood.
In this process of sixty daily blood plasma cleanses, the kidneys filter about 180 litre (48 gallons) of water from the blood. After purification, most of the fluid pulled from the blood plasma is cleaned and returned to the bloodstream and the rest (less than 1 percent, or about 1.5 litres (1.5 quarts)) excreted from the body as urine.
Other important functions of the kidneys are the production and secretion of the following three hormones:
• calcitriol (which is the active form of vitamin D) helps maintain healthy bones and as well as a normal chemical balance in the body
• renin, a very important enzyme for the control and regulation of a person’s blood pressure
• erythropoietin controls the rate of formation of red blood cells by stimulating bone marrow
To say that kidneys are sophisticated and vitally important reprocessing machines is an understatement to say the least, and since the kidneys are the blood’s filters, it is no wonder that they are well supplied with blood vessels. In fact, every minute one-quarter of the body’s arterial blood is delivered to the kidneys via the renal arteries.
The kidney diagram shows that once inside the kidney, the renal artery splits into numerous segmental arteries that branch out into the kidney called afferent (incoming) arteriole (a terminal branch of the artery). Blood leaving the kidney, instead of connecting to a vein as do the body’s other capillary networks, they connect to an efferent (outgoing) arteriole.
The internal anatomy of the kidney breaks into two main regions:
• a smooth, reddish renal cortex. Within the cortex are the nephrons, the basic processing units of the kidney where the actual removal of wastes occurs. Each kidney has about a million nephrons and each is hooked to an afferent (incoming) arteriole. These arterioles then divide into little tangled capillary balls called glomeruli which are closely intertwined with tiny urine-collecting tubules (see below)
• a darker inner region, the renal medulla, consisting of 8 to 18 renal pyramids, tapering to the middle of the kidney. These pyramids are composed of tubules which are bundles of tiny urine-gathering components
Combined the nephrons and tubules act as a sieve to cleanse the blood.
The formation of urine
Inside the kidneys, intricate processes takes place whereby water and dissolved waste materials leave the blood and enter the urinary system. There are three processes involved in the formation of urine:
• Simple filtration The semi permeable walls of the glomerulus and glomerular capsule allow water and small molecules to freely pass, but larger molecules (including blood cells, plasma proteins and others) can’t cross this barrier and they remain in the capillaries
• Selective reabsorption – The purpose of this process is to reabsorb back into the blood those filtrate constituents the body requires to main fluid and electrolyte balance, as well as the blood’s pH level. Foreign substances (ie those that are not normal blood constituents) do not get reabsorbed
• Secretion – Substances not required and foreign materials which aren’t cleared from the blood by filtration are cleared by secretion into the convoluted tubules and from there these are then excreted from the body via the urine you pass
A healthy adult passes 1000 to 1500 ml (~1 to 1.5 quarts) per day. The amount of urine produced and its colour (among other factors) vary according to the fluid intake and the amount of substances that have been filtered out. During sleep and muscular exercise urine production is decreased.
The composition of urine reflects the activities of the nephrons in the maintenance of homeostasis, a vital role to balance water and electrolyte concentrations within the body. Electrolyte balance is maintained and the pH (acid/alkaline balance) is maintained by the excretion of hydrogen ions.
Urine is a mix of clear, amber and pale yellow in colour due to the presence of urobilin a bile pigment altered in the intestine, reabsorbed then excreted by the kidneys. It is also slightly acid solution of salts, the nitrogenous compounds urea and uric acid, creatinine, excessions, some drugs and metabolized hormones.
Dilute urine will be somewhat less than the plasma’s specific gravity of 1010, while concentrated urine may reach 1030. If you drink nothing for a full day, your kidneys continue producing urine at a specific gravity or at least 1.025. By selective excretion of acid or alkaline salts, the slight alkalinity of the blood is kept constant.
Without at least one litre (1 quart) of water per day, the water for urine will begin coming from tissues, which can lead to dehydration and more concentrated strong smelling urine as well as urine darker in color.
Some of the other dark urine causes include consumption of foods such as red beets (the urine has a pink or brownish tinge) although this can also be due to the presence of blood or bile salts in the urine. Vitamin supplements and prescription drugs can also cause discoloration. The frothiness of urine comes from bile salts or an excess of blood serum proteins in the urine (proteinuria). Smoky or cloudy urine is often caused by an infection.
Eating certain foods such as asparagus causes sulphur-containing amino acids to break down, lending urine a sulphurous smell. However, normally healthy urine has only a slight odor at first, but outside the body it begins to take on the smell of ammonia as bacteria begin to metabolize the substances in the urine.
What is kidney function
The term kidney function is used to describe how healthy your kidneys are. A kidney function test will assist in determining how well your kidneys are operating. If the results come back showing 100 percent kidney function that will mean you have two healthy kidneys. Even if the results come back and it shows a mild decline, say down to 60 to 70% of normal kidney function, this would rarely be noticeable.
However serious health problems occur when people have less than 25 percent of their kidney function and for many people with reduced kidney function, kidney disease also tends to be present. At kidney function below 10 to 15 percent of normal capacity will require radical therapy to sustain life, either by mechanically cleaning their blood (dialysis) or even via a kidney transplant.
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Daniels P, et al, Body-The Complete Human, National Geographic Society, Washington, USA, 2007
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH), www.kidney.niddk.nih.gov/kudiseases/pubs/yourkidneys/
Waugh A & Grant A, Anatomy and Physiology in Health and Illness, 9th Edition, Elsevier Limited, UK, 1998