13 Excretion in humans Flashcards
[3 MARKS]
Describe how and where in the body urea is formed
📌 breakdown of amino acids
📌 removal of nitrogen containing parts
📌 excess amino acids transported to the liver
📌 deamination
ref to book for other mistakes
How is carbon dioxide excreted
carbon dioxide is excreted through the lungs [during exhalation]
- WASTE PRODUCT of aerobic respiration
- must be excreted as it dissolves in water easily to form an acidic solution which can lower the pH of cells
- can reduce the activity of enzymes in the body which are essential for controlling the rate of metabolic reactions
- too much carbon dioxide in the body is toxic
Define excretion
removal of toxic materials, the waste products of metabolism, and substances in excess of requirements
e.g., urea, CO2, salts/ions
NOT defacating - this is NOT excretion, but egestion
metabolism: chemical reactions in the cell including respiration
What do kidneys excrete?
kidneys excrete urea and excess
water and ions
by producing urine
Why are kidneys important?
[excretory system, filters - “clean” blood]
important for maintaining the water & ion balance in the body; ADJUSTMENT OF IONS (SALTS) IN THE BLOOD + ADJUSTMENT OF WATER IN THE BLOOD
also filter urea out of blood and excrete it; REMOVAL OF UREA FROM BLOOD
waste products transferred to bladder
Identify in diagrams and images the kidneys,
ureters, bladder and urethra
Organs involved in excretion
skin & lungs
skin excretes water & mineral ions
lungs excrete CO2 & water
liver
liver: PRODUCES urea from amino acids [breakdown of them; process: deamination]
Ureter
transports urine from the kidneys to the bladder
urethra
facilitates removal of urine from body
bladder
collects urine prior to urination
- Removal of Urea
Why are excess amino acids broken down by liver?
Bc - proteins CANNOT be stored by the body
so excess amino acids broken down by liver -> deamination
What is the waste product?
Urea
[nitrogen-containing part of amino acids. Diffused into blood to be]
filtered out by the kidneys
[also excreted partly in sweat]
Why should urea be excreted?
toxic waste product so must be excreted before it reaches high concentrations
- Adjustment of ion content
Ions e.g.?
Taken in how? Removed by?
Ions such as sodium are
taken into the body in food.
Excess ions are removed by the KIDNEYS.
- Adjustment of water content
Too little water in blood?
Hypothalamus detects blood is too highly concentrated ->
Pituitary gland releases ADH ->
More ADH enters kidneys - more water is reabsorbed ->
So less & more concentrated urine produced
Too much water in blood
Hypothalamus detects blood is not concentrated enough ->
Pituitary gland releases LESS ADH ->
Less ADH enters kidney - less water is reabsorbed ->
More urine that’s less concentrated is produced
The hypothalamus in the brain _______ to ___________ into the _____
EXAMPLE of homeostasis
monitors the water content of the blood and instructs the pituitary gland,
TO: release the hormone ADH (Anti-diuretic hormone)
INTO: into the blood
Kidney structure: pelvis, cortex, renal vein (above), renal artery, medulla (look like shells), ureter (coming out of it at the bottom)
Renal vein does?
transports filtered blood back to the heart
renal artery
transports unfiltered blood from the aorta into the kidney
cortex
blood is filtered here by nephrons
[pelvis - urine collects here before passing into the ureter]
medulla
where water is reabsorbed to maintain water balance
Step 1: Ultrafiltration
Glomerulus?
The glomerulus is a knot of blood vessels surrounded by the renal capsule
-> high blood pressure…
High blood pressure in the glomerulus forces water, ions, urea, & glucose out of the blood
Exceptions that CANNOT BE forced out
proteins, RBCs too large to be filtered
-> This is ULTRAFILTRATION.
Step 2: Selective Reabsorption
- In the renal tubule:
USING ACTIVE TRANSPORT (for filtering blood)
- ALL glucose is reabsorbed
- sufficient ions/salts are reabsorbed using active transport as for glucose & water
- sufficient water is also reabsorbed here (depending on effects of ADH)
What happens to remaining?
The remaining urea, water & salts are passed on to the bladder as urine
The Nephron – unit of filtration
made up of ;;
Glomerulus
Renal capsule
Renal tubule
Capillaries
Name substance that has molecules too large to pass through walls of capillaries
/ molecules too large to be filtered
Protein
Name substance reabsorbed in kidney /
Has molecules which are small enough to be filtered but is completely reabsorbed from fluid in the kidney tubule
Glucose
Name substance reabsorbed kidney
Glucose
Name substance that is a metabolic waste product
Urea
Name substance that increases in concentration as fluid moves along the kidney tubule
Salts
Urea
State 3 structures thru which fluid from region 4 passes as it leaves the body (NO GLUCOSE NO PROTEIN)
Ureter
Bladder
Urethra
Process of maintaining constant conditions within the body
Homeostasis
Define excretion
Removal from the body
Of toxins
And waste products of metabolism
And substances in excess of requirements
Outline role of liver in excretion [3]
Deamination
Removal of nitrogen containing part of amino acids
To produce urea
Urea passes into blood
State two waste substances that are removed from the blood by dialysis.
urea ;
ammonia ;
water ;
Define active transport [2]
Movement of ions
Against concentration gradient through a partially permeable membrane
Using energy from respiration
1 e.g. other than glucose of substance reabsorbed into blood from renal tubule
Ions
Explain why the concentrations of sodium ions and urea are greater at Z (urine) than Y (fluid)
[2]
water has been reabsorbed ;
by osmosis ;
(in/ by) collecting duct
as it passes through the liver
changes in concentration of glucose
and urea in the blood
glucose less,
urea more
Where is urea formed?
liver
a function of the kidneys of a healthy person?
reabsorb all glucose
Where are hormones removed from the blood and broken down in the human body?
liver
How is urea removed from the body?
in solution
renal artery - glucose
renal vein - glucose
ureter - salts
bladder - urea
Explain the function of the renal capsule in the kidney [3]
(ultra)filtration ;
high blood pressure assists filtrate to pass through capsule ;
proteins too big to move out of capsule /
glomerulus ;
filtrate small enough to move through ;
Explain how a dialysis machine filters blood.
dialysis membrane is partially permeable ;
minerals / salts / ions / urea, move by diffusion ;
from high concentration to low concentration / down a
concentration gradient ;
water, moves by osmosis ;
Explain how, when the patient is receiving dialysis treatment
(i) the loss of plasma proteins and red blood cells is prevented,
too large to go through membrane
the normal glucose concentration of the blood is maintained.
dialysing solution contains glucose ;
glucose diffuses ;
(until blood is) at, correct / normal, concentration
Describe the changes that occur in the urea concentration in the blood over the
period shown in Fig. 2.2.
You will gain credit for using the data in Fig. 2.2 in your
answer. [3]
decreases during, dialysis
increases, over next day after dialysis ;
maximum concentration(s) decreases (over time) ;
minimum concentration(s) (after dialysis) decreases (over
time) ;
Explain the changes in urea concentration in the blood as shown in Fig. 2.2. [4]
(urea) produced in liver ;
deamination ;
amino acids ;
diffuses, out of blood ;
through (dialysis) membrane ;
Describe the process of filtration in the kidney. [3]
ref to blood pressure ;
due to the heart / AW ;
ref to capillaries ; A glomerulus
small molecules forced out (of blood) ;
two examples ; urea, water
Name the processes resulting in the reabsorption of
1. glucose
2. water
diffusion ;
active uptake / active transport ; [max 2]
/////
osmosis ;
The kidneys remove metabolic waste from the liquid part of the blood.
Name:
(i) the liquid part of the blood;
[1]
(ii) the process that involves removing metabolic waste from the body.
plasma;
excretion ;
FUNCTIONS
- glomerulus
(ultra)filtration ;
small molecules, from blood or glomerulus;
are forced/ pushed (out)/ under (high) pressure ;
- tubule
(selective) reabsorption ;
back into the blood/ capillaries ;
e.g. of any substance that is filtered or reabsorbed like glucose ;
is all reabsorbed in the kidney;
glucose
Dialysis fluid contains sodium ions.
Use the information in Table 1.1 to suggest the concentration of sodium ions that
should be in the fluid and give a reason for your answer.
concentration g per 100cm3
reason
0.35 (g per 100cm3) ;
same concentration as the blood
State two components of blood that are not in dialysis fluid.
urea ;
amino acids ;
Use Fig. 3.2 to describe how kidney tubules reabsorb glucose from the filtrate. [2]
(glucose is reabsorbed) by active transport (from
filtrate) ;
against concentration gradient ;
using energy ;
When plants are grown in a solution that includes a poison that prevents respiration,
the roots continue to absorb water, but do not absorb many ions.
Explain this result [3]
active uptake/active transport, of ions against the concentration gradient
(into the root) ;
energy is needed for, active uptake/active transport ;
comes from respiration ;
water is absorbed, by osmosis
Describe the changes that occur to the blood as it flows through the dialysis machine
from A to B.
urea (concentration) decreases ;
water (content) increases / decreases ;
salt (concentration), decreases
Discuss the advantages of kidney transplants compared with dialysis.
long term solution / person no longer needs (regular) dialysis ;
an example of a disadvantage of dialysis ;
A pain / tiring / discomfort / takes a long time
increased freedom / better quality of life
