HUman Bio - Ch 41 The Kidneys and Osmoregulatory Organs

ADH (vasopressin)

hormone that regulates the permeability of the collecting duct walls and is released when a person is dehydrated

-produced by hypothalamus and secreted by posterior pituitary

-makes the collecting duct more permeable to water

-leads to rise in blood volume

Aldosterone

"salt-retaining hormone" which promotes the retention of Na+ by the kidneys. na+ retention promotes water retention, which promotes a higher blood volume and pressure

Excretion

Process by which metabolic wastes are eliminated from the body

hypertonic solution

A solution in which the concentration of solutes is greater than that of the cell that resides in the solution

hypotonic solution

A solution in which the concentration of solutes is less than that of the cell that resides in the solution

isotonic solution

a solution whose solute concentration is equal to the solute concentration inside a cell

nephron

The tubular excretory unit of the vertebrate kidney.

Nitrogenous waste products

urea, uric acid, creatinine, ammonia

Osmoconformers

An organism that allows its internal salt concentration to change with the salinity of the surrounding water

Osmoregulation

regulation of solute concentrations and water balance by a cell or organism

Osmoregulators

organisms that maintain their internal water balance and solute concentration within narrow limits

salt glands of marine birds

transport epithelia that excretes water saltier than the ocean, allowing birds to drink ocean water with a net gain of water

Osmoregulation in freshwater fish

1. Freshwater fish are hyperosmotic to their environment, leading to water gain (too little salt)

2. Uptake salt through gills and in food

3. Discharge water through dilute urine

osmoregulation in saltwater fish

gain water and salt ions from drinking water, constantly lose water to hyperosmotic environment, excrete salt ions from gills and urine from kidneys

Ammonia

A small, very toxic molecule (NH3) produced by nitrogen fixation or as a metabolic waste product of protein and nucleic acid metabolism. Made up of 1 Nitrogen and 3 hydrogen atoms.

Urea

waste product formed in the liver, filtered out of the blood by the kidneys, and excreted in urine,a colorless crystalline compound which is the main nitrogenous breakdown product of protein metabolism in mammals and is excreted in urine. CH4N2O

uric acid

nitrogenous waste excreted in the urine

When is uric acid produced?

Uric acid is a waste product created during the normal breakdown of purines, naturally occurring substances found in foods such as liver, mushrooms, anchovies, mackerel and dried beans according to the NIAMS. Uric acid is normally cleaned out of the blood by the kidneys, and passes out of the body along with urine.

Ammonia vs Urea

Because ammonia is toxic, it is excreted immediately by fish, converted into uric acid by birds, and converted into urea by mammals. ... Ammonia is smaller, more volatile and more mobile than urea. If allowed to accumulate, ammonia would raise the pH in cells to toxic levels.

Ammonia vs urea vs uric acid

In contrast, mammals (including humans) produce urea from ammonia; however, they also form some uric acid during the breakdown of nucleic acids. In this case, uric acid is excreted in urine instead of in feces, as is done in birds and reptiles. ... Uric acid is also less toxic than ammonia or urea.

Ureotelic animals

, which includes mammals, produce urea as the main nitrogenous waste material.

filtration process

As the glomerular filtrate passes through the nephron, components needed by the body, such as water, glucose, and ions, leave the nephron by diffusion and reenter the blood; water is reabsorbed at the tubules of the nephron

Glomerular filtration:

Glomerular filtration: The first stage in urine formation. This is the process in which water and other substances in the blood plasma (electrolytes, glucose, fatty acids, amino acids, nitrogenous wastes, and vitamins) pass from the capillaries of the glomerulus into the Bowman's capsule. This stage must be controlled because if filtration is too high, reabsorption of the required water and solutes. If filtration is too low, the wastes that should be eliminated are reabsorbed.

Tubular reabsorption:

Tubular reabsorption: The second stage in urine formation. This is the process of reclaiming water and other substances (sodium, glucose, nitrogenous wastes) from the tubular fluid. After these substances leave the surface of the renal tubule, they are reabsorbed by the capillaries into the blood stream.

Tubular secretion:

The third stage in urine formation. This is the process of removing chemicals from the blood and secreting them into the tubular fluid. This helps to remove wastes and plays a core role in acid-base balance.

Water conservation:

The fourth and final stage of urine formation. The kidneys not only dispose of wastes but they prevent the body from losing too much water. If the body loses too much water, dehydration will occur. Water is reabsorbed into the blood stream by osmosis. The amount of urine produced in the end is based upon the amount of fluid in the body. The more water a person intakes in a day, the more urine they will urinate.

protonephridia of flatworms

Cilia draw body fluid into tubules, filtrate excreted, mostly function for osmoregulation rather than exception, metabolic waste diffuses across body surface or eliminated through the moth or tubules networks of tubules with ciliated structures called flame bulbs that pull fluid through branched ducts opening to the outside

metanephridia

In annelid worms, a type of excretory tubule with internal openings that collect body fluids and external openings that excrete waste from the body.

Malpighian tubules

An excretory organ that is unique to insects, empties into digestive tract and removes nitrogenous wastes from the hemolymph, also plays a role in osmoregulation. Malpighian tubules are slender tubes normally found in the posterior regions of arthropod alimentary canals. Each tubule consists of a single layer of cells that is closed off at the distal end with the proximal end joining the alimentary canal at the junction between the midgut and hindgut.

nephridium

A blood filtration and excretory organ characteristic of segmented worms. Nephridium. The nephridium (plural nephridia) is an invertebrate organ which occurs in pairs and performs a function similar to the vertebrate kidney. ... They are present in many different invertebrate lines. There are two basic types, metanephridia and protonephridia, but there are other types.

kidney structure

The cortex and medulla make up two of the internal layers of a kidney and are composed of individual filtering units known as nephrons.

renal pelvis

funnel-shaped reservoir that collects the urine and passes it to the ureter

Nephrons are

Microscopic structures in the kidneys that produce urine

afferent arteriole

The small artery that carries blood toward the capillaries of the glomerulus.

ammonotelic

describes an animal that excretes ammonia as the primary waste material

angiotensin converting enzyme (ACE)

an enzyme found on the surface of blood vessels in the lungs and other tissues with vasopressive action

Angiotensin I

small polypeptide generated in plasma by the action of the enzyme renin on angiotensinogen; inactive precursor of angiotensin II (product in the renin-angiotensin-aldosterone pathway)

Angiotensin II

increases blood pressure by stimulating kidneys to reabsorb more water and by releasing aldosterone (molecule that affects different organs to increase blood pressure) polypeptide

Anti-diuretic hormone (ADH)

Source: Posterior Pituitary

Target: Kidneys

Action: Water balance/ blood pressure

Hormone that prevents the loss of water.

Antioxidants

Organic molecules that help protect the body from harmful chemicals called free radicals. Agent that prevents cell destruction by reactive oxygen species.

Arcute Artery

Artery that branches from the interlobar artery and arches over the base of the renal pyramids.

renal artery

an artery originating from the abdominal aorta and supplying the kidneys and adrenal glands and ureters

asending limb

Part of the loop of Henle that ascends from the renal medulla to the renal cortex

blood urea nitrogen (BUN)

blood test that measures the amount of urea in the blood

Bowman's capsule

Structure that enclose the glomerulus

calyx or calix

Cup-like collecting region of the renal pelvis. The term comes from Greek, kalux meaning a cup or case surrounding a flower bud.

cortex

outer layer of the kidney

cortical nephrons

Nephrons located almost entirely in the renal cortex. These nephrons have a reduced loop of Henle. 85% of nephrons; almost entirely in the cortex

nephron function

Regulate the concentration of water and soluble substances like sodium salts by filtering the blood, reabsorbing what is needed and excreting the rest as urine thereby eliminating wastes from the body, regulating blood volume and BP, controls levels of electrolytes and metabolites, and regulates blood pH.

cortical radiate artery

The artery that branches from the arcuate artery, continuing into the cortical region of the kidney. It branches to form the afferent arterioles.

countercurrent exchanger

peritubular capillary network that allows exchange of solutes and water from the renal tubules

descending limb of loop of henle

Portion of the nephron permeable only to water. The filtrate becomes more concentrated as it travels through, increasing concentration of the interstitial fluid. Part of the loop of Henle that descends from the renal cortex into the renal medulla.

distal convoluted tubule (DCT)

segment of the nephron between the nephron loop and the collecting duct Cuboidal cells with very few microvilli

Function more in secretion than reabsorption

Confined to cortex

efferent arteriole

The small artery that carries blood away from the capillaries of the glomerulus.

Electrolyte

A solute that produces ions in solution; an electrolytic solution conducts an electric current.

flame cells (protonephridia)

Specialized hollow excretory or osmoregulatory structure composed of one or several small cells containing a tuft of flagella and situated at the end of a minute tubule; connected tubules ultimately open to the outside (Excretory cell found in flatworms)L

glomerular filtration

The first step in urine formation in which substances in blood pass through the filtration membrane and the filtrate enters the proximal convoluted tubule of the nephron.

glomerulus filtration rate

measure the volume of blood plasma filtered per minute by the kidneys

glumerulus

Cluster of capillaries surrounded by a membrane called the Bowman's capsule, portion of nephrons active in filtering urine

hilum of kidney

medial depression for blood vessels and ureter to enter kidney chamber( region in the renal corpuscles that contains the capillary)

inferior vena cava

receives blood from lower limbs and abdominal organs and empties into the posterior part of the right atrium of the heart

interlobar artery

artery that branches from the segmental artery and travels in between the renal lobes

juxtaglomerular cells

The cells of the afferent artery at the juxtaglomerular apparatus. They are baroreceptors that secrete renin upon sensing a decrease in blood pressure. ( in the afferent and efferent arterioles that responds to stimuli from the macula densa

juxtamedullary nephrons

-Long nephron loops deeply invade medulla

-Ascending limbs have thick and thin segments

-Important in production of concentrated urine

Nephron that lies in the cortex but close to the renal medulla.

kidney

organ that removes urea, excess water, and other waste products from the blood and passes them to the ureter

Lobes of the kidney

Each renal pyramid with its cortical cap forms a lobe. Lobes are not seen except in fetal kidneys.

Loop of Henle

section of the nephron tubule that conserves water and minimizes the volume of urine

mucula densa

group of cells that senses changes in sodium ion concentration; presents in parts of the renal tubule and collecting ducts.

Medulla

middle layer of a organ like the kidney or adrenal gland.

Microvilli

projections that increase the cell's surface area

Molality

Number of moles of solute per kilogram of solvent.

Molarity

the number of moles of solute per liter of solution

Mole

Gram equivalent of the molecular weight of a substance.

nephridia (earthworm)

gets ride of metabolic waste through pores on each segment

excretory system (Excretory structures found in annelids)

nephridiopore (Annelida)

a pore through which nepridia release waste fluid to the outside; located near tiny bristles called setae

non-electrolyte

a substance that does not readily ionize when dissolved or melted and is a poor conductor of electricity.

osmotic balance

the appropriate values of water and solute concentrations for a healthy organism

osmotic pressure

the pressure that would have to be applied to a pure solvent to prevent it from passing into a given solution by osmosis, often used to express the concentration of the solution. (Pressure exerted on a membrane to equalize solute concentration on either side.

perirenal fat capsule

a fatty mass that surrounds the kidney and cushions it against blows

peritubular capillary network

capillary that surrounds a renal tubule and functions in reabsorption and secretion during urine formation

proximal convoluted tubule (PCT)

first section of the renal tubule that the blood flows through; reabsorption of water, ions, and all organic nutrients ( part of the renal tube that lies closest to the glomerulus.)

renal capsule

The connective tissue covering the external surface of the kidney

renal columns

Area of the kidney through which the interlobar arteries travel in the process of supplying blood to the renal lobes

renal corpuscle

the glomerulus and Bowman's capsule together

renal fascia

protective outer covering of the kidney

renal pelvis (of kidney)

region in the kidney where the calyces join the ureters.