cells, and are the elements in the bile which assist the pancreatic secretion in the digestion of fats. They are largely absorbed in the intestines and resecreted by the Hver — probably because of their value as a stimulus to bile secretion. Biliousness, as commonly understood by the laity, is due to the poverty of the bile in these acid salts. In their comparative absence fats are very hard to digest or to dispose of, hence the intolerance of the patient to greasy foods ; and the stimulation of bile- flow is weakened, causing a general diminution of bile and bile-function. Cholesterin and Lecithin are both of them true excretory products, being secreted from the blood by the liver cells. They both pass out unchanged in the feces.
Innervation. — The secretion of bile does not appear to be under the control of any special set of nerves, but is a constant function, dependent for its regulation only upon the vaso-motor influences of the hepatic vessels, and probably also on the character of the blood flowing through them.
Discharge of Bile. — Normally the bile is not continuously given by the liver directly to the duodenum, but is stored in the gall-bladder, guarded by a sphincter, and discharged at intervals during digestion. The ejection of the chyme into the duodenum acts as a stimulus for the reflex which relaxes the sphincter, contracts the gall bladder, and throws the bile into the duodenum. This reflex is mediated by the vagus and splanchnic nerves.
<Callout type="important" title="Important">The discharge of bile is regulated by the vagus and splanchnic nerves.</Callout>
Function of Bile. — Bile performs a two-fold role, (1) that of an excretory function, eliminating cholesterin, lecithin, and bile pigments, and (2) that of a digestive process, accelerating the emulsification and hydrolysis of fats in the intestine.
<Callout type="risk" title="Risk">Obstruction of the bile duct can lead to jaundice due to absorption of bile pigments.</Callout>
Glycogen is frequently called animal starch, as it has the same general chemical formula as vegetable starch, and is amenable to the action of ptyalin with practically the same end-products. It is constantly present in the normal liver, being stored up during digestion and given out to the tissues gradually in the fasting intervals. The quantity present varies, therefore, in regard to the occurrence of meals ; the mean quantity is about 2.5 per cent of the weight of the liver.
Formation of Glycogen. — Normally the great bulk of glycogen is undoubtedly derived from the hydrocarbon of the diet. These reach the liver in the form of dextrose, levulose, and saccharose, which are dehydrated by the liver cells into glycogen, as follows: C6H12O6—H2O=C6H10O5.
Experiment and observation make it clear that glycogen may also be derived from the proteids of the blood. Of the various end-products of pepsin and trypsin digestion, those containing a nitrogen atom are probably converted in the liver into urea, the balance going to make sugar, which is subsequently converted into glycogen.
Pats increase the amount of glycogen in the liver, but whether by direct conversion into this product or by diminishing the consumption of glycogen by the tissues is not certainly known. Von Noorden asserts that glycogen is derived directly from fats.
<Callout type="warning" title="Warning">Diabetes may result from a deficiency in the polymerization process of glycogen, leading to an excess of sugar in the blood.</Callout>
Uses of Glycog'en. — The modern doctrine of glyco-gen is that it represents the storage of the carbohydrate nutriment of the body which the liver holds in trust and gives out to the blood as required.
Regulation of Glycogen Formation. — The formation of glycogen is a constant metabolic process, and modified only by the quantity and quality of the diet. Each hydrocarbon has a different limit to which the liver is able to dispose of its sugar-product. For starch, which forms so large a portion of our diet, no limit is known, and of the sugars themselves glucose has the highest limit, as much as 150 gms being taken care of at one dose.
When these articles are fed beyond their limit glycemia occurs, due to the surplus sugar-products which the liver is unable to store as glycogen.
Regulation of Glycogen Distribution. — That the doling out of glycogen in the form of glucose by the liver to the tissues is in some way under the control of the nervous system seems probable from the fact that certain disturbances of the nervous equilibrium bring about a temporary glycemia and glycuria, and also from Claude Bernard's famous 'piqure' experiment, in which he induced glycosuria by a puncture of the fourth ventricle.
The spleen is an organ whose function or functions are very obscure. It is supposed to (1) generate new corpuscles, (2) furnish a graveyard for red blood corpuscles, and (3) assist in the formation of uric acid.
Elimination. The kidneys secrete urine. Inasmuch, however, as the constituents of the urine are all existent in the blood when it reaches the kidney, and are simply separated by those organs, it would be more correct to say that they excrete urine. In the absence of one kidney, the other, if healthy, will compensate by performing double duty indefinitely.
Complete suppression of renal function, however, rapidly produces death.
Process of Excretion. — Two principal theories hold the field as to the mechanism by which the kidneys excrete the urine: 1. The Ludwig or mechanical theory accounts for the process by the purely mechanical agencies of filtration and diffusion. In the glomeruli the entire urine, in a dilute condition, is filtered from the blood, the process being regulated by the pressure in the blood vessels. In the tubules it loses some of its water by diffusion and becomes more concentrated.
- The Bowman-Haidenhain theory holds that the glomeruli separate water and inorganic salts from the blood, and the tubules secrete the organic constituents, urea, etc., both processes depending primarily upon the vital activity of the epithelial cells, although blood pressure necessarily plays a quite important part.
The preponderance of evidence is in favor of the latter theory, and it will be assumed here.
Albuminuria. — In their normal condition the epithelial cells of the kidneys are only permeable to those inorganic and organic constituents of the blood which make up the normal constituency of urine. In diseased conditions of the kidney which disable these cells, however, other elements are let through the glomeruli and tubules, chief among which is albumin. This phenomenon is known as albuminuria, and is common to all those diseases which injure the epithelial tissue of the kidneys.
There are two varieties of albumin found in pathological urine, Nucleo-Albumin and Serum Albumin. Of these the former is derived from the disintegration of the epithelial cells themselves, and is therefore not diagnostic of renal disease, as the disintegrated cells may come from other parts of the urinary tract.
Serum albumen, on the other hand, is derived directly from the blood, and is evidence of the disability and permeation of the renal tissues. The gravest forms of albuminuria, of course, are found in diseases of the kidney proper, i.e., in all forms of nephritis, amyloid disease, tuberculosis, cancer, abscess, calculus, etc.
The next severest occurrences of it are seen in those circulatory diseases, and diseases affecting circulation, which produce a secondary congestive effect upon the renal tissues, as heart diseases, hepatic cirrhosis, tumors, anemia, etc.
All infections and toxic conditions cause a transient albuminuria by the extension of their poisonous action to the renal cells.
Hematuria (blood in the urine) — Is the result of grosser lesions of the kidney tissue, allowing blood en masse to enter the glomeruli and tubules. (This, of course, assuming that the blood originates in the kidney, and not in some other part of the urinary tract).
All of the causes above credited with the power of causing albuminuria may also, by affecting grosser injury, give rise to hematuria.
Hemoglobinuria is, of course, always present when hematuria is, but may occur independently in diseases in which there is great destruction of red corpuscles, e.g., anemia, grave infectious diseases, etc.
Glycosuria. — Ordinarily, that is to say under the pressure in which it normally exists in the blood, the renal tissues are impermeable to sugar. But when it reaches an abnormally high percentage it is excreted in the urine. This occurs in diabetes mellitus and is pathognomonic of that disease.
Casts are nothing more or less than particles of renal tissue which have acquired the mould of the tubules in passing through them, and in many cases gained a covering of epithelium. They are of numerous variety, depending upon their composition, or more often upon their appearance, such as hyaline, granular, waxy, fatty, and blood casts.
True epithelial casts, composed entirely of epithelial cells, are rare.
Casts, of course, are found only in destructive processes in the renal tissues, and are diagnostic, when found in numbers, of organic kidney lesions.
Absolute anuria is rare, but may be caused by (a) complete destruction or disability of renal tissue, as in violent acute nephritis and in the last stages of organic kidney diseases, or (b) by complete pelvic obstruction, as in nephrosis, calculus, etc.
Oliguria (diminished secretion) results from any conditions injuring or disabling the secreting area and uncompensated by increased renal blood flow, as in malignant diseases, amyloid degeneration, acute nephritis, later stages of chronic nephritis after compensation has failed.
Polyuria (increased secretion) comes from conditions which while not completely disabling the secreting tissues, render them abnormally permeable to fluids, as in interstitial nephritis, cirrhosis, diabetes, etc.
Innervation. — The secretion of urine is a continuous process, performed, as stated, by the epithelial cells of the glomeruli and tubules, and is innervated by the sympathetic fibres supplying the kidneys from the renal plexus. The kidneys receive no nerves from the cerebro-spinal system, and their function is outside the province of voluntary acceleration or inhibition.
In view of the fact, elsewhere stated, that the renal function is essential to life, it is fortunate that interruption of the motive power of urinary secretion, whatever that motive power may be, is so rare as to be practically unknown. Increased and decreased secretion, however, may and frequently does result from nervous and emotional conditions, which must be explained by their effect upon the renal function through the nerve channels above described.
It is worthy of note in this connection that such influences seem to affect only the glomerular portion of the function, since nervous and psychic polyuria consists always in an increase in the water and inorganic salts, with a corresponding drop in density, while the same types of oliguria exhibit simply a diminution in these ingredients with a corresponding rise in density. The organic secretions do not seem to be influenced in such purely nervous cases.
Hysteria, migraine, neurasthenia, epilepsy, delirium tremens are examples of nervous polyuria.
Post-operative shock, melancholia, cerebral disorders, etc., frequently inhibit the renal function, and may even cause death thereby.
Vaso-Motor Regulation. — It has already been said that even under the Bowman-Haidenhain theory the secretion of urine is partially regulated by the blood-pressure in the kidneys. This is brought about by vaso-motor mechanism. The kidneys are supplied very richly with vaso-constrictor fibres, stimulation of which contrasts the renal vessels, raises pressure, lessens the flow of blood through the organs, and diminishes the secretion of urine. Inhibition of these constrictors dilates the renal vessels, increases the flow of blood, and accelerates secretion of urine.
Constriction of the arterioles at the skin, reflexly dilates those of the kidneys, increasing renal elimination.
Blood Flow. — From the foregoing it will be seen that the amount of secretion depends upon the quantity of blood passing through the kidney in a given time rather than upon blood pressure, and upon the latter only as it determines the former. High arterial pressure and low venous pressure, with no constriction of the renal vessels, will of course, drive large quantities of blood through the kidney and increase the urine.
Low arterial pressure, even though the renal vessels be dilated, will lessen the flow of blood and diminish the urine.
Polyuria. — For the above reasons the quantity of urine secreted is always increased in those conditions which increase the flow of blood through the kidneys, as in cardiac hypertrophy primary (i.e., not due to contracted kidney) which induces high pressure in the renal arteries, and in cystic degeneration of the kidney and hydronephrosis which dilate the renal vessels.
Oliguria, or diminished flow of urine, is for like reasons induced by all diseases which lessen the blood flow through the kidneys, e.g., myocarditis, valvular diseases (uncompensated), lung diseases, hepatic cirrhosis, which reduce the blood force, and in all diseases of the kidney itself which constrict the renal vessels.
The urine is normally a pale amber-colored fluid, slightly acid in reaction when passed, and of about 1.020 specific gravity. Its acidity depends chiefly upon the presence of acid phosphates, of which sodium phosphate is the most important, which, again, owe their preponderance to the proteids in the diet. The specific gravity is of course
Key Takeaways
- Bile functions include digestion and excretion.
- Glycogen formation and distribution are regulated by the liver and nervous system.
- Urine excretion is primarily determined by blood flow through the kidneys.
Practical Tips
- Monitor your diet to maintain proper glycogen levels, which can help manage energy levels during fasting periods.
- Be aware of conditions that may obstruct bile ducts, as they can lead to jaundice and other health issues.
- Understand how blood flow affects urine production; this knowledge can be useful in diagnosing certain kidney diseases.
Warnings & Risks
- Obstruction of the bile duct can lead to serious complications such as jaundice.
- Diabetes may result from a failure in glycogen polymerization, leading to high blood sugar levels.
- Nervous and emotional conditions can affect urine production, potentially masking underlying kidney issues.
Modern Application
While the historical techniques described in this chapter focus on understanding the physiological processes of bile and glycogen, many of these principles still apply today. Modern medical practices have improved diagnostic tools and treatments for liver and kidney diseases, but a foundational knowledge of these functions remains crucial for survival preparedness. Understanding how to manage diet and recognize symptoms can help prevent serious health issues.
Frequently Asked Questions
Q: What is the role of bile in digestion?
Bile plays a dual role: it assists in the emulsification and hydrolysis of fats, making them easier to digest, and also serves as an excretory product for eliminating cholesterol, lecithin, and bile pigments.
Q: How does glycogen formation occur in the liver?
Glycogen is primarily formed from dietary carbohydrates that are dehydrated by liver cells. It can also be derived from proteids of the blood through a process involving pepsin and trypsin digestion.
Q: What causes albuminuria in kidney diseases?
Albuminuria occurs when the epithelial cells of the kidneys are injured, allowing albumin to pass into the urine. This is common in various kidney diseases such as nephritis and amyloid disease.