BIOL113 L34

What is the functional unit of the vertebrate kidney?

a Nephron

what is a nephron and its function ?

Each of your kidneys is made up of about a million filtering units called nephrons. Each nephron includes a filter, called the glomerulus, and a tubule. The nephrons work through a two-step process: the glomerulus filters your blood, and the tubule returns needed substances to your blood and removes wastes.

What is excretion?

The output of substances from the body, including salts, water, metabolic waste products, ammonia, urea, and CO2.

How do most excretory systems produce a filtrate?

By pressure-filtering body fluids and then modifying the filtrate’s contents.

What are the 'extra-renal' excretory organs?

Lungs, gills, salt glands, and skin.

Which organisms have protonephridia as their excretory organs?

Flatworms, rotifers, larval annelids, and molluscs.

what are renal organs?

organs that produce urine, flatworms, rotifers, larval annelids and molluscs have protonephridia. Insects, spiders and centipedes have malpighian tubules: Annelids (earthworm), molluscs, crustaceans and vertebrate kidney have metanephridia and coelomoducts.

What is the function of Protonephridia in urine formation?

Balancing water uptake and reabsorbing valuable solutes in the tubule.

How is urine formed in Protonephridia?

Beating cilia of 'flame bulb' draws water and solutes into the tubule (filtration).

What is the primary urine formation process in Malpighian tubules?

Active transport of potassium salts into the tubule, water follows by osmosis, generating urine flow.

is uric acid soluble or insoluble ?

insoluble

What is the function of Metanephridia and coelomoducts in urine formation?

They are renal organs that produce urine in annelids (earthworm), molluscs, crustaceans, and vertebrate kidney.

What are metanephridia (in earth worms)?

They are excretory organs found in each body segment of an earthworm, immersed in coelomic fluid and enveloped by a capillary network.

What is the function of nephrostome in metanephridia of an earthworm?

It is an open ciliated funnel that allows coelomic fluid to enter the metanephridia for filtration.

How does metanephridia produce urine in earthworms?

Found in each segment of the earthworm's body, these structures consist of a nephrostome, which filters coelomic fluid into tubular metanephridia. Through selective reabsorption, useful substances are retained, while waste products, including ammonia and excess ions, are transported through the metanephridial duct to exit the body via the nephridiopores. This process results in the production of urine, which helps maintain internal osmolarity and removes metabolic waste

What makes metanephridia more advanced than protonephridia?

They are an open system, open at both ends, allowing faster urine formation, and are surrounded by a network of blood vessels to adjust the composition of urine.

What percentage of the heart's output do the renal arteries supply to the kidneys?

About 20%

How much blood flows through a pair of human kidneys each day?

Between 1,100 and 2,000 litres (275 times total blood volume).

How many kidney tubules called nephrons are there in each kidney?

About 1 million.

what is similar about protonephridia and metanephridia?

both involve a similar basic process of urine formation. In both systems, fluid continuously enters tubules, where it undergoes selective modification. Valuable solutes are selectively withdrawn from the fluid through reabsorption, while waste products are secreted.

What does the vertebrate kidney structure regulate?

Osmolarity of blood, Na/K ratio of plasma, blood volume, blood pressure by adjusting rate and composition of urine formation.

What are the main components of the nephron structure in mammals?

Bowman’s capsule, Loop of Henle, Proximal tubule, Distal tubule.

What are the components of the initial filtrate in the nephron?

Salts, sugar, amino acids.

Where does the tubular reabsorption of water and salts occur in the nephron?

Proximal tubule.

What percentage of the filtrate is reabsorbed in the process of water reabsorption?

65%.

How is the reabsorption of water and salts in the proximal tubule achieved?

Through osmosis and active transport.

What is the process of reabsorption of useful salts, sugars, and amino acids in the proximal tubule called?

Tubular reabsorption

What is the process in the nephron that is least selective?

Filtration.

What is the function of the distal tubule in tubular reabsorption?

Salt reabsorption/secretion.

What happens in the collecting duct during dehydration?

Water reabsorption concentrates the final urine when the animal is dehydrated.

what is diuresis?

Diuresis is a physiological process in which the kidneys increase the production and excretion of urine, leading to a higher urinary output.

Which hormone primarily affects the water permeability of the collecting ducts?

Antidiuretic hormone (ADH)

what is antidiuresis?

Antidiuresis is a physiological process in which the kidneys reduce the amount of urine produced, leading to water conservation and decreased urinary output.

More antidiuretic hormone results in…

More permeability, thus more water reabsorption and more concentrated urine

Less antidiuretic hormone results in…

less water permeability, more water retained in urine.

What is the adaptation of the kangaroo rat's nephrons to address the problem of water conservation?

Extremely concentrated urine and extremely long loops of Henle to maintain steep osmotic gradients.

What is the adaptation of the beaver's nephrons due to living in fresh water?

Very short loops of Henle and very little ability to concentrate urine.

What is the adaptation of bird kidneys for water conservation?

Birds have much shorter loops of henle compared to mammals which creates a problem of water conservation. To solve this they produce uric acid which can be excreted as a paste, rather than urea which must be dissolved in water.

How do reptiles solve the problem of water conservation?

They have no loops of henle which creates a problem of water conservation. To solve this, they produce uric acid and reabsorb water across the epithelium of cloaca.

What is the adaptation of trout kidneys for living in freshwater?

Trout are hyperosmotic to surroundings. Problem: excess water take up across the gills. Solution: Producing very dilute urine.

How do amphibian kidneys function in fresh water and on land?

They excrete dilute urine in fresh water, but reabsorb water across the bladder when on land to conserve water.

What is the main function of the kidney in tuna?

Excretion of double-charged salts (Ca2+, Mg2+, SO42-).

What are tuna to sea water and what problem does this create?

hypo-osmotic to seawater. Problem: lose water across the gills and gain salts. Their nephrons have small glomeruli, which are the initial filtering units in the kidney. Additionally, they lack a distal tubule, a part of the nephron responsible for fine-tuning electrolyte balance in other animals. Moreover, tuna have relatively few nephrons in their kidneys. These adaptations help reduce water loss and minimize the intake of excess salts.

Why do vampire bats need to eliminate a large amount of liquid?

to be light enough to fly.

What type of urine do vampire bats produce when feeding?

Dilute urine to get rid of excess water from the blood meal.

What type of urine do vampire bats produce when roosting?

Very concentrated urine to get rid of nitrogenous waste while conserving water (up to 4,600 mosm/L).

What is the osmoregulatory/excretory system of a freshwater flatworm based on?

The operation of protonephridia.

What must freshwater fish do to maintain homeostasis?

Excrete large quantities of water.

what is osmoregulation?

Osmoregulation is the biological process by which organisms regulate the concentration of water and solutes within their bodies to maintain optimal internal conditions, despite changes in the external environment.

what does hyper-osmotic mean?

describes solution with the greater concentration of solute than another solution. e.g trout is said to be hyper-osmotic to fresh water.

what does hypo-osmotic mean?

describes a solution with a lesser concentration of solute than another solution. e.g tuna is hypo-osmotic to sea water.