Goblet cell

Galactogogues – Boosting Your Milk Supply and Production

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That is, the out-of-body events were experienced when blood flow in the brain had ceased. The theory is that certain layered combinations of planar calcite molecules can perform unique functions. The ultimate result of this shift was the emergence of the dominant left brain. Melatonin also seems to play an important role in regulating sleeping cycles; test subjects injected with the hormone become sleepy, suggesting that the increased production of melatonin coincident with nightfall acts as a fundamental mechanism for making people sleepy. Use of Herbals as Galactagogues. It was their job to test me.

Chapter 25: Renal Physiology and Disease

Proton pump inhibitors (PPIs) mechanism of action. A video animation

For example, carnivores ingest animal tissue that is primarily water, frugivores consume fruits containing water, and the nectar consumed by nectarivores is, of course, largely water. In the Sonoran Desert of the southwestern United States and northwestern Mexico, a cactus plant saguaro, Carnegiea gigantean appears to be an important source of water for several species of birds Wolf and de Rio Even foods that seemingly contain little water can serve as a water source because water is produced as a by-product of cellular metabolism.

This metabolic water can be of particular importance to birds in arid environments Williams The amount of water formed during fuel oxidation depends on a variety of factors, including metabolic rate and fuel type carbohydrates, fats, or proteins; Schmidt-Nielsen How do birds drink? Within each of these two main categories, however, there are several kinds of mechanisms.

For example, water is taken into the mouth by scooping water with the lower beak in cockatoos Cacatuinae. Mallards drink using a complex interplay of capillary action and pressure changes in different areas of the mouth. Among the suction drinkers, parakeets ladle water with the tip of the tongue and some parrots drink with a suctioning action.

Pigeons and doves, on the other hand, use a "double-suction mechanism" in which capillary action is responsible for bringing water between the slightly gaping tips of the beak and then the tongue acts as a piston to pump the water into the pharyngeal cavity.

Drinking by a Bengalese Finch. Water runs between the beak tips as a result of adhesion and capillary action. The bill then tips up and that, along with tongue movements, moves water into the pharynx Heidweiller and Zweers Mourning Dove drinking notice that doves don't have to tip their heads up like most other birds. The role of bird kidneys Figure 1 , like the kidneys of other vertebrates is filtration, excretion or secretion, and absorption.

They filter water and some substances from blood, such as waste products of metabolism and ions, that are voided in the urine. Kidneys also play an important role in conserving water and reabsorbing needed substances like glucose. The urinary organs of birds consist of paired kidneys and the ureters Figure 2 , which transport urine to the urodeum of the cloaca. Avian kidneys are divided into units called lobules. Each lobule has a cortex outer area and medulla or medullary cone; Figure 3.

Urine is carried from the avian kidneys to the cloaca and, specifically, the middle section called the urodeum by the ureters Figure from McSweeney and Stoskopf Image from Sherwood et al. Lobule of an avian kidney. The medullary cones include the loops of Henle and collecting ducts of nephrons plus a number of capillaries called the vasa recta. The avian renal medulla is cone shaped because the number of loops of Henle decreases toward the apex of the medullary cones.

The functional unit of the kidney is the nephron. Avian kidneys have two kinds of nephrons. A reptilian-type, with no loops of Henle are located in the cortex, and a mammalian-type with long or intermediate length loops, are located in the medulla Figure 4.

Nephrons filter the blood plasma to eliminate waste products, but, in doing so, must not lose needed materials like glucose or too much water. Blood enters nephrons via small arteries called afferent arterioles Figure 5. This blood enters the glomerulus a collection of capillaries; Figure 6 under high pressure and 'filters' through the walls of the capillaries and the walls of a surrounding structure called a capsule.

The filtrate that moves from the glomerular capsule into the proximal tubules is basically plasma without protein the protein molecules are too large. That filtrate, therefore, contains lots of important substances. In the proximal convoluted tubules, those needed substances such as vitamins and glucose are reabsorbed into the the blood Figure 7. Nephron components mammalian type nephron shown: Plasma is filtered from the glomerular capillaries into the glomerular capsule.

Filtrate then travels through the tubules and loop of Henle before entering the collecting duct. Glomeruli of an Anna's Hummingbird. Reabsorption of materials from the proximal convoluted tubule back into the blood.

Other than mammals, birds are the only vertebrates that conserve body water by producing urine osmotically more concentrated than the plasma from which it is derived. However, the ability of birds to concentrate urine is limited compared to mammals. Typically, water-deprived birds produce urine that is 1. This 'concentrating capacity' resides within the medullary cones. Solutes sodium chloride, or NaCl are actively transported out the ascending limb of the Loop of Henle Figure 8 , where they become concentrated in the medulla medullary cones.

When urine passes throughout the osmotic gradient in the medulla, water leaves the tubules by osmosis and the urine become concentrated. Because only the looped nephrons contribute to the intramedullary osmotic gradient, the presence of loopless nephrons may limit the ability of the kidneys to produce hyperosmotic urine.

Thus, the concentrating ability of avian kidneys is more limited than in mammals. This reduced capacity of avian kidneys to concentrate urine compared to mammals means that more water accompanies the solutes that travel from the kidneys through ureters to the cloaca.

Water-deprived birds do have a mechanism for reducing the amount of water leaving the kidneys. In response to dehydration, the pituitary gland releases more of a hormone called arginine vasotocin AVT into the blood. In the kidneys, AVT causes a reduction in the glomerular filtration rate the rate at which plasma filters from the glomeruli into the glomerular capsule; Figure 8 so less water moves from the blood into the kidney tubules.

In addition, AVT increases the permeability of the walls of collected ducts to water by opening protein water channels called aquaporins Figure 8. As the collecting ducts become more permeable, more water moves by osmosis out of the collecting ducts because of the higher solute concentration in the medullary cones and can be reabsorbed by kidney capillaries. Studies to date suggest that the extent to which AVT can reduce urine production and water loss varies among species, but, in general, AVT is less effective in conserving water than the mammalian equivalent antidiuretic hormone, or ADH; Nishimura and Fan Therefore, water-deprived birds tend to produce more urine, and lose more water from the kidneys, than would a similar-sized water-deprived mammal.

A proposed model for urine concentration in the mammalian-type nephron of birds showing transport of NaCl and water in various nephron segments. Left , NaCl is actively exported out of the thick ascending limb TAL and some re-enters the descending limbs DLs by simple diffusion but, despite the resulting high solute concentration, water does not follow because the membrane is not permeable to water.

Loops of Henle exhibit some variation in length and more NaCl is transported out of the longer loops of Henle so the osmotic gradient is greatest near the end of the medullary. AVT arginine vasotocin is a hormone that helps birds conserve water by reducing the glomerular filtration rate the rate at which plasma moves from glomeruli in the glomerular capsules and by increasing the permeability of collecting ducts to water by opening protein water channels called aquaporins; AQP Figure from Nishimura and Fan Nasal respiratory turbinates are complex, epithelially lined structures in nearly all birds and mammals that act as intermittent countercurrent heat exchangers during respiration.

Respiratory turbinates also allow birds to conserve water by helping to 'dehumidify' air during exhalation. During inhalation top , ambient air passes over the respiratory turbinates and is warmed to body temperature. As a result, air is saturated with water vapor, and the turbinates are cooled by evaporative water loss. During exhalation bottom , warm air from the lungs returns through the nasal passage and is cooled as it passes over the turbinate surfaces.

This results in a substantial reduction in the moisture and heat contained in exhaled air. This graph depicts water vapor added to inhaled air shaded arrow and water condensate recovered from exhaled air open arrow. Hillenius and Ruben Birds that feed on nectar can consume a huge amount of fluid compared to their body weight.

And the more dilute the nectar, the higher the volumes ingested. Although the birds derive nutrients and energy from nectar, they have to get rid of the large amounts of water taken in.

Failing to do so can have devastating consequences. Palestine Sunbirds have somehow overcome the problems of life on liquid diet, so McWhorter et al. In the kidney, water is filtered out of blood by specialized structures called glomeruli, and some of the eliminated water is later reabsorbed in the nephron and collecting duct.

The researchers set out to test how these processes respond to water intake in Palestine Sunbirds. Although following the birds around and measuring their nectar intake is difficult, McWhorter and his colleagues came up with an ingenious solution to the problem.

They discovered that the birds adjust the amount they consume according to the concentration of sucrose solutions they are fed: In this way, the team could vary the bird's water intake and measure the rates of renal filtration and reabsorption. McWhorter explained that when the team began investigating this nectarivorous bird's approach to fluid management, it was thought that renal filtration changes according to water status; decreasing in response to water shortage, but increasing only moderately as the birds take on water.

But this was based on ideas developed for birds that do not regularly cope with a large intake of water. McWhorter and his team also knew that when the birds are on dilute diets, water is shunted through the gut without being absorbed.

So, how would Palestine Sunbirds' kidneys cope? The team found that renal filtration is not exceptionally sensitive to water loading in sunbirds; it increased only slightly in response to a dramatic decrease in sucrose concentration. On the other hand, the fractional water reabsorption - a measure of the proportion of the eliminated water that is reabsorbed by the kidney - dropped significantly when the birds were on the most dilute diet.

The sunbirds' kidney responds to the elevated water levels by decreasing reabsorption, rather than by raising the filtration rate.

The team also found that the glucose and osmotic concentrations in the final excreted fluids were significantly lower than those in the ureteral fluids released by the kidney. Because the gut and urinary tracts of birds join at the cloaca, the researchers conjecture that the dietary water that shunts through the gut might have diluted the ureteral fluids. They conclude that Palestine Sunbirds deal with large amounts of water intake by not absorbing it in the first place.

From an economical standpoint this makes sense, as eliminating water by increasing renal filtration rate can be energetically costly for birds.

Sugar and other metabolites lost during filtration may only be retained by reabsorption, possibly overwhelming the kidney's ability to prevent solute loss. But how the gut could absorb nutrients without taking in dietary water is still a mystery, as the two processes normally come hand in hand Click on the photo to check out Peter Jones' website.

Sunbirds and other birds feeding on nectar from aloe erythrina Erythrina livingstoniana flowers. An important part of the diet of all birds is protein. Proteins are composed of subunits called amino acids, and those amino acids are sometimes used as a source of energy or are converted into fats or carbohydrates.

When amino acids are used for energy or converted to fats or carbohydrates, the amine NH 2 group must be removed. These amine groups are toxic and must be eliminated. Some organisms excrete these nitrogenous wastes as ammonia e. Birds and reptiles excrete these wastes primarily as uric acid. Although excreting nitrogenous wastes as uric acid has its advantages e. Molecular structure of a typical amino acid, ammonia, urea, and uric acid. The homeostasis of fluid and ions in birds involves several organ systems Figure 10 and is a more complex phenomenon than in other vertebrates.

In birds, the kidneys and lower gastrointestinal tract cloaca, rectum, and ceca are involved in the regulation of extracellular fluid composition.

Many birds also have functional salt glands see below. Osmoregulatory organs of birds Hughes As noted above, the avian kidney has a limited capacity for the conservation of body water and electrolytes via elimination of hyperosmotic urine. This low capacity to concentrate urine is not a liability because urine formed by the kidneys travels along the ureters into the cloaca Figure From there, it may move by retrograde peristalsis into the lower intestine colon and cecae.

Fluid from the upper gastrointestinal tract also enters the cloaca. Therefore, the cloaca receives an influx of water from the kidneys and the small intestine. The influx of water into the cloaca can be reabsorbed through the epithelium of the lower intestinal tract to maintain hydration. In the lower intestine and cecae, water and sodium chloride are reclaimed by the process of sodium-linked water reabsorption Figure In other words, positively-charged sodium ions are actively transported out of the intestine and negatively-charged chloride ions follow.

Water then follows by osmosis. Uric acid is, as a result, concentrated and excreted as a relatively dry mixture with feces Hildebrandt Diagram of the cloaca and lower intestine of a domestic chicken Gallus gallus.

Initially, the solutes in the urine cause water to move by osmosis out of the surrounding tissues and into the coprodeum the section of the cloaca adjacent to the colon or large intestine.

After being transported by peristalsis into the colon, however, NaCl is transported out of the colon and water follows the concentration gradient osmosis and is reabsorbed Laverty and Skadhauge The predominate form in which nitrogen is excreted by birds uric acid requires little water for excretion because it isn't very soluble in water.

However, it does require a significant amount of protein to maintain it in a colloidal suspension in the urine i. The source of some of this protein is the plasma, as significant amounts pass through the glomerular filtration barrier. This protein is not lost because it is broken down when the urine enters the lower colon Goldstein et al. In the colon, the composition of the urine is altered in several ways.

Ask in the forums yourself. Discussions about 'discharge' in the English Only forum. Save history View All Links: Refers to person, place, thing, quality, etc. Sustantivo de género exclusivamente femenino "mesa", "tabla". Sustantivo de género exclusivamente masculino "televisor", "piso". Robert found it difficult explaining the reasons for his discharge to potential new employers. A Robert le resultó difícil explicar las razones de su despido a sus nuevos empleados potenciales.

Verb taking a direct object--for example, " Say something. Verbo que requiere de un objeto directo " di la verdad", " encontré una moneda".

The doctor discharged the patient as soon as she was well enough to go home. El doctor dio de alta a la paciente tan pronto como estuvo lo suficientemente bien para irse a casa.

Julian is a good employee who has always discharged his duties to a very high standard. Julian es un buen empleado que siempre ha cumplido con sus obligaciones de manera intachable.

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