Excretion Flashcards
The sum total of all the chemical reactions that take place in a cell.
Metabolism.
Why does metabolic waste need to be removed continuously?
It will poison the cells and inhibit normal functioning if allowed to accumulate.
How does metabolic waste leave the cells?
It diffuses out the cells via the tissue fluid that surrounds them, to the blood vessels.
What is an excretory organ?
An organ with the ability to remove waste products.
Where does the blood carry metabolic waste?
Excretory organs.
What are the four excretory organs/organ pairs?
Lungs.
Kidneys and bladder.
Liver and intestines.
Skin.
What do the lungs excrete?
CO2, water vapour and heat.
What do the kidneys and bladder excrete?
Urine.
What does urine consist of?
Excess water, mineral salts and nitrogenous waste products (namely urea, uric acid and creatinine).
What do the liver and intestine excrete?
Urea and bile pigments.
What does the skin excrete?
Sweat (via sweat glands).
What does sweat consist of?
Excess sweat, salts and a small amount of urea.
What are the origins of metabolic waste?
Cellular respiration - CO2 and excess water.
Deamination of amino acids - urea.
Metabolism of nucleic acids - uric acid.
Creatinine phosphate in the cells - creatinine.
Haemoglobin breakdown in the liver - bile pigments.
Which organs makeup the urinary system?
2 kidneys, 2 ureters, the bladder and the urethra.
Which two blood vessels are associated with the urinary system?
Renal arteries and renal veins.
Where are the two kidneys?
In the abdominal cavity, on either side of the vertebral column, just below the diaphragm.
Where do the kidneys receive oxygenated, metabolic waste rich, blood from?
The renal arteries.
Which blood vessel carries deoxygenated, purified, blood away from the kidneys?
The renal veins.
What do the 2 ureters do?
They extend from the kidneys and separately open into the bladder.
What is the structure and function of the kidney?
Thin walled muscular sack which temporarily stores urine.
What does the urethra do?
Transports urine from the bladder to the exterior.
What controls urine flow to the urethra from the bladder?
A sphincter muscle.
Describe the external structure of the kidneys.
Dark red, bean-shaped organ with the concave side facing the vertebral column.
What is the hilum?
The indentation on the concave side of the kidney where the renal artery enters and the renal vein and ureter leave the kidney.
What is the function of the layer of fat around the kidneys.
Protection, insulation and holds them in place.
What is the renal capsule?
A connective tissue membrane there for protection.
What is the cortex?
A reddish brown region directly under the renal capsule.
What is the medulla?
The inner region of the kidney containing the renal pyramids.
What is the renal papilla?
The apex of the of each pyramid.
What is the renal calyx(/calyces)?
The common tube that the tubes in the renal papilla open into.
What do the renal calyces open into?
The renal pelvis, the widened region of the ureter.
What is a nephron?
The structural and functional unit of the kidney.
What are the two main parts of the nephron?
The Malpighian body and the renal tubule.
What does the Malpighian body consist of?
The Bowman’s capsule and the glomerulus.
Where is the Malpighian body situated?
On one end of the nephron, in the cortex.
What is the Bowman’s capsule?
A double-walled, cup-shaped structure in the Malpighian body.
What is the glomerulus?
A network of blood capillaries in the Bowman’s capsule.
What surrounds the capillary blood vessels of the glomerulus?
A single endothelial layer (squamous epithelium) with pores between the endothelial cells.
Which blood vessel transports blood to the glomerulus?
Afferent arteriole.
Which blood vessel transports blood away from the glomerulus?
Efferent arteriole.
What does the inner wall of the Bowman’s capsule consist of?
Podocytes.
What are podocytes?
Cells with projections between which filtration slits occur.
What is the cavity of the Bowman’s capsule?
The cavity between the inner and outer wall of the Bowman’s capsule.
What is the renal tubule?
A long convoluted tubule situated partly in the cortex and partly in the medulla.
Name the three parts of the renal tubule.
The proximal convoluted tubule, the loop of Henle and the distal convoluted tubule.
Where is the proximal convoluted tubule situated?
Directly after the Bowman’s capsule in the cortex.
Where is the renal tubule widest?
At the proximal convoluted tubule.
What lines the proximal convoluted tubule?
A single layer of cuboidal epithelium.
Name the parts of the loop of Henle.
Descending limb and ascending limb.
Where is the loop of Henle situated?
In the medulla of the nephron.
What does the ascending limb of the loop of Henle connect to?
The distal convoluted tubule.
What lines the distal convoluted tubule?
A single layer of cuboidal epithelium.
What does the distal convoluted tubule open into?
A collecting duct.
Name the duct formed by multiple collecting ducts converging.
Ducts of Bellini.
Which tubes form the renal pyramids?
Ducts of Bellini.
The renal artery enters the kidney at the ______.
hilum
How is oxygenated blood carried to the nephron cortex?
The renal artery branches into smaller arteries and extend between the pyramids in the direction of the cortex.
The branches of the renal artery continue to branch until they form ______ _______.
afferent arterioles
Each afferent arteriole leads to a _______.
Bowman’s capsule
What does the afferent arteriole divide into?
The glomerulus.
What do the capillaries of the glomerulus merge to form?
The efferent arteriole.
Why is the afferent arteriole much wider than the efferent arteriole?
To maintain high pressure in the blood in the glomerulus.
What does the efferent arteriole branch to form?
The peritubular capillary network, surrounding the renal tubule.
The peritubular capillaries eventually combine to form the _____ _____.
renal vein
What are the three main processes of the kidney?
Glomerular filtration, tubular reabsorption and tubular excretion.
Where does glomerular filtration take place?
The Malpighian body.
What forms an ultrafine filter in the Malpighian body?
The thin endothelium with pores lining the blood capillaries of the glomerulus, and the podocyte layer with filtration slits.
What is not filtered out of the Malpighian body?
Blood cells and plasma proteins.
What is the part of the blood that gets filtered into the Bowman’s capsule called?
Glomerular filtrate.
What useful substances are contained in glomerular filtrate?
Water Amino acids Glucose Vitamins Mineral salts
What waste products are contained in the glomerular filtrate?
Urea
Uric acids
Creatine
What is the filtration process promoted by?
High blood pressure in the glomerulus
Large filtration surface
Permeability of the glomerular membrane
What is the function of tubular reabsorption?
Preventing useful substances from forming part of urine and being excreted.
What are the adaptations of the proximal convoluted tubule for reabsorption?
Long and convoluted
Surrounding peritubular capillary network
Many mitochondria in the cuboidal epithelial cells
Cuboidal epithelial cells have finger-like projections
All glucose, amino acids and water soluble vitamins are _____ reabsorbed into the peritubular capillary vessels.
actively
Approximately 66% of water _______ reabsorbed into the peritubular capillaries by _______.
passively; osmosis
What substance is in high concentration in the medulla?
Sodium (Na+).
Why does the medulla need a high salt concentration?
So that water will passively leave the loop of Henle passively (osmosis).
Water moves from a ____ to a _____ water potential.
high; low
Which limb of the loop of Henle is permeable to water?
The descending limb.
Which limb of the loop of Henle has sodium ions actively pumped out of it?
The ascending limb.
What transports sodium ions from the medulla to prevent it becoming too salty?
The peritubular capillary network.
What is tubular excretion?
The process of substances being excreted from the blood in the peritubular capillaries through the epithelium of the renal tubule and added to the filtrate.
Where does tubular excretion occur?
In the proximal and distal convoluted tubules.
Which substances are actively added to the filtrate during tubular excretion?
Hydrogen ions Potassium ions Creatine Urea Drugs Preservatives Colourants And other foreign substances
What is the filtrate called once it’s flowed into the collecting duct?
Urine.
What does urine consist of?
Water
Inorganic salts
Metabolic wastes
Foreign substances
Where is the pH of the blood regulated?
The distal convoluted tubule.
What is the range of the regulated blood pH?
7.35 and 7.45.
What occurs when the pH in the blood is too low?
Secretion of H+ ions from the blood to the tubules.
What in the filtrate binds with the H+ ions to act as a buffer?
Phosphate compounds.
What are H+ ions excreted as in the urine?
Hydrogen phosphate.
______ _______ prevents the pH in the urine becoming too low (acidic).
Hydrogen phosphate.
When blood pH becomes too high fewer ______ ions are secreted and more _______ ions are secreted.
hydrogen; bicarbonate
