Excretion- bio 20

How does the excretory system regulate the composition of body fluids

By removing wastes: ammonia, urea and uric acid, excess ions, other metabolites

How does the excret. System regulate the volume of water

By excreting extra water or reabsorbing water as needed. Humans lose two litres of water a day

how does the excret. System balance pH

By removing excess hydrogen ions via the kidneys

Role of lungs

Remove CO2 from the blood and remove other gases and water vapour

The role of skin

Excretes water, salts and urea in perspiration

Role of the digestive system

Excretes water, salts, lipids and other cellular chemicals. Note that feces is not a product of excretion

Where do nitrogenous compounds come from

Through the breakdown of amino acids and nucelic acids (DNA RNA)

What’s deamination

The removal of an amino group from a molecule

What is ammonia converted into to make it less toxic

Into urea in the liver

Renal artery/ vein

Renal artery: carries blood to the kidneys for filtration

Renal vein: carries filtered blood away from kidneys for reoxygenation

Kidney

Organ where waste is removed from the blood. Blood is filtered by nephrons

Ureter

Tune that connects the kidney to the bladder

Bladder

Where urine is temporarily stored until it is voided from the body

Urethra

Tube through which urine exits the bladder and body

Renal cortex

Outer layer of kidneys. Most of filtration occurs here

Renal medulla

The inner structures of the kidney. Most of reabsorption occurs here

Renal pelvis

Where urine collects before it’s moved to the urethra

Glomerulus

A network of capillaries which filters the blood components according to size.

Small components: move through capillary cells

Large components: remain

Proximal tubule

Reabsorption of nutrients, ions and water back into the blood begins, both by active and passive transport

Loop of Henle

Mostly water and ions are reabsorbed into the blood again by active and passive transport

Distal tubule

Continued reabsorption of water and ions as well as secretion of H+, K+ and other substances like drugs by active transport

Bowman’s capsule

Collects filtrate from the glomerulus. Not only has wastes but also substances needed by the body

Collecting duct

Connects the nephron to the renal pelvis. Reabsorption of water by osmosis occurs as urine moves along the collecting duct

Difference between active and passive transport

Passive does not require energy while active require atp. A concentration gradient is an example of passive transport.

Where does filtration occur

Thé glomerulus

The blood capillaries in the glomerulus is…

Semi permeable and allow water and small substances to move out of the blood and into the bowman’s capsule

What allows the filtrate to be pushed out of the blood

The pressure of the blood that enters the glomerulus

Substances present in filtrate

Water, ions, glucose, amino acids, urea, uric acid, ammonia

Substances not present in filtrate

RBCs and plasma proteins

What is the goal of reabsorption

To return water and required substances back to the blood

Where does reabsorption occur

Proximal and distal tubule, loop of Henle and the collecting duct

Where is most of filtrate reabsorbed

In the proximal tubule (65%)

substances reabsorbed through active transport

Nutrients and positively charged ions

Substances reabsorbed through passive transport

Negatively charged ions (by following positively charged ions)

Substances reabsorbed through osmosis

Water

The main substances reabsorbed in the loop of Henle

Water and ions

Reabsorption in the distal tubule involves…

The active transport of sodium ions, passive transport of negative charged ions along with the sodium ions and the reabsorption of water through osmosis

How can the distal tubule be changed

Depending on the body’s hydration, blood ions concentration and blood pressure. Controlled by hormones

Reabsorption in the collecting duct

There is still a lot of water that needs to be reabsorbed. As the collecting duct passes through the renal medulla, water is reabsorbed into the blood

Secretion

Occurs in the kidney to rid the blood of unwanted materials. Occurs by the active transport of substances from the blood into the nephron

Substances secreted into the nephron

Hydrogen ions, potassium ions, ammonia

Osmoreceptors and hypothalamus

A part of the brain that measures the osmotic pressure of the blood

What happens when the level of water in plasma decreases

Signals are sent to the pituitary gland to increase the secretion of a hormone called ADH

How does ADH decrease the volume of urine

By increasing the permeability of the distal tubules and the collecting ducts to water

When the concentration of water in the blood plasma increases…

The volume of urine decreases

Diabetes insipidus

Disease where a person does not make ADH

Aldosterone

Another hormone produced to regulate reabsorption. Increases permeability of the collecting ducts to sodium ions and the reabsorption of water

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