Excretory System in the Human Flashcards
What is excretion?
Excretion is the removal of waste products of metabolism from the body.
How does the excretory system play a role in homeostasis?
The excretory system plays a role in homeostasis: (i) by maintaining the composition of an organism’s fluids, including fluid balance and chemistry. (ii) by preventing the accumulation of poisonous wastes which might interfere with metabolism.
What is homeostasis?
Homeostasis is the maintenance of a constant internal environment within the body.
What are the main waste products of homeostasis
The main waste products are water, carbon dioxide and nitrogenous (nitrogen-containing) wastes.
What happens to wastes which go into the liver and what are they called? What wastes are produced?
In the liver, excess amino acids are split into a carbohydrate and urea.
What wastes do the lungs remove?
The lungs remove carbon dioxide and water.
What wastes do the sweat glands excrete?
The sweat glands excrete water and some salts.
What do the kidneys remove?
The kidneys remove most of the rest, including the urea.
What does the urinary system consist of? (basic)
The kidneys, the bladder and some ducts (tubes).
Draw the urinary system
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What are all the parts of the urinary system?
Diaphragm, Aorta, Vena Cava, Adrenal gland, Renal artery, Kidney, Renal vein, Ureter, Bladder, Urethra, Sphincter (controls the release of urine)
What does a section through the kidney show?
A section through the kidney shows an outer darker region (cortex) and a lighter inner zone (medulla).
Draw a diagram of the kidney.
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What are all the parts of the kidney?
Tubule, Pyramid, Collecting duct, Cortex, Medulla, Renal vein, Renal artery, Pelvis, Ureter
How do the kidneys work?
The kidneys work by filtering the blood and then absorbing back what the body needs to keep. The wastes are allowed pass to the bladder, for storage and release.
What happens as urine is produced?
As urine is produced, it flows into the renal pelvis, then into the ureter, to the bladder
What are two main words to describe what the kidneys do?
Filtration and Reabsorption
How does filtration happen in the kidney?
In the outer cortex, small molecules like glucose, amino acids, water, urea and salts filter out of the blood into narrow tubules
How does reabsorption happen in the kidney?
Blood vessels reabsorb back useful nutrients from the tubules. Urea, excess salts and water, are allowed to continue down the tubule and on to the bladder.
What is secretion?
Secretion is the production and release of chemicals from cells.
Where are some substances secreted from and where are they secreted into?
Some substances, especially potassium and hydrogen ions, are secreted from the blood into the tubule in the cortex region.
What happens when the blood becomes too acidic?
When the blood becomes too acidic, hydrogen ions are secreted into the urine.
How do the kidneys control blood pH?
By controlling the hydrogen ion concentration in the blood, the kidneys control blood pH.
From where is water lost from the body?
Lungs, skin, intestines and kidneys
Do we have control over the amount of water lost each day from the lungs, skin or intestines?
We have no control over the amount of water lost each day from the lungs, skin or intestines.
What organs control water in the body and what is this called?
So the kidneys are the water control (osmoregulatory) organs of the body - conserving or eliminating water as the body requires.
What type of creatures are mammals and birds? (to do with heat)
Mammals and birds are endotherms (warm blooded): their source of heat is internal [from their own metabolic heat].
What type of creature are most animals? (to do with heat)
Most animals are ectotherms (cold blooded) - they lose or gain heat by moving into areas where temperature is suitable, e.g. fish, amphibians, reptiles.
What happens to blood when our temperature rises?
If our temperature rises more blood flows close to the surface of skin so heat is lost by radiation.
What happens to glands when our temperature rises?
Glands release sweat (a weak salt solution) onto the surface of the skin - this perspiration cools the skin, by taking away some of the body heat when it evaporates.
What must be done because of glands releasing sweat?
This loss of water, as sweat, must be replaced - that is why it is important to drink water before, during and after exercising to maintain the balance of water and salts in the body.
What happens to blood if our temperature drops?
Blood leaves the surface layers and flows beneath the adipose (fat) tissue which insulates us, so less heat is lost through the skin surface
What happens to sweat when we get cold?
We stop sweating
What happens to hairs when our temperature drops?
Hairs stand up ( causing “goose bumps”) to try and insulate us with air
What happens to the muscles when our temperature drops?
We shiver (muscles contract to generate extra heat).
What is the structural and functional unit of the kidney?
The structural and functional unit of the kidney is the nephron.
What does the renal artery divide into?
The renal artery divides into afferent arterioles and then into a capillary network (glomerulus) at the top of each nephron.
Draw a diagram of the nephron.
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What does the renal artery divide into in filtration?
The renal artery divides into afferent arterioles and then into a capillary network (glomerulus) at the top of each nephron.
What surrounds each glomerulus and what happens there?
A cup-shaped funnel (Bowman’s capsule) surrounds each glomerulus and it is here that smaller molecules in the blood are forced, under pressure, out of the plasma and into the lumen of Bowman’s capsule, forming the glomerular filtrate.
Why is the blood pressure high in the efferent arteriole?
The blood pressure is high because the efferent arteriole is narrower than the afferent arteriole, so force-filtering the plasma.
What gets filtered in the efferent arteriole?
Everything except large proteins and blood cells gets filtered.
What can the body not afford to lose and how does it prevent it’s loss?
The body cannot afford to lose useful chemicals like food and water, so as the glomerular filtrate passes from the Bowman’s capsule into the proximal convoluted tubule, glucoses, amino acids, some salts and water are reabsorbed back into the blood.
What happens to the food molecules and most of the salt ions after they are reabsorbed?
The food molecules, including most of the salt ions, are taken back by active transport (against the concentration gradient, so energy is needed for this). Most of the water is reabsorbed by osmosis - from the Loop of Henle and convoluted tubules.
What is not reabsorbed?
Urea and other wastes, along with some water, are not reabsorbed. They pass, as urine, into the pelvis of the kidney and to the bladder for storage. Of the 180L of blood filtered each day, about 99% of the filtrate is reabsorbed.
What regulates the amount of water in the body and how does it do it?
The kidney regulates the amount of water in the body by varying the amount of urine produced.
What is regulating the amount of water by varying the amount of urine produced known as and what is it an example of?
This is known as osmoregulation, and it is and example of homeostasis.
What hormone controls the reabsorbtion of water into the blood?
ADH [Anti-diuretic hormone] controls whether the distal tubule and collecting ducts reabsorb water or not.
What happens if you drink a great deal of water?
The hypothalamus in the brain detects the diluted blood and turns off ADH production. Less water is reabsorbed so more water is allowed to escape to the bladder and a larger volume of dilute urine is produced.
What happens when the body is low on water?
ADH is secreted from the pituitary gland. More water is reabsorbed and only a small volume of urine is produced.
Where is the nephron located?
In the cortex and medulla of the kidney
What is the function of the nephron?
To make urine
What are the nephrons?
The functional units of the kidney, i.e. they make urine
What does blood enter the kidney through?
The renal artery
What does the renal artery divide up into in the kidney?
renal arterioles
What does each renal arteriole divide up into?
A cluster of capillaries called a glomerulus
Where is a glomerulus found?
in each Bowman’s capsule
What is a Bowman’s capsule?
A cup-shaped structure at one end of the nephron
Where does blood leave the glomerulus?
in the efferent arteriole
What does the efferent arteriole divide to form?
The capillaries that surround the rest of the nephron
What do the capillaries that surround the rest of the nephron rejoin to form?
renal venules
What do renal venules combine and leave the kidney as?
the renal vein
Where is urine produced?
The nephron
How does secretion happen in the kidney?
Secretion of potassium ions and hydrogen ions in the distal tube help to maintain the pH of blood.
What is filtration?
Filtration means that water and small molecules pass (under high pressure) from the blood into the nephron
What is reabsorption?
Reabsorption means that molecules pass from the nephron back into the blood
What is active transport?
Active transport means that energy (in the form of ATP) is used to move molecules, often against a concentration gradient, i.e. from low concentrations to high concentrations
