11.3
Excretory System
Definitions
Excretion—
The disposal of nitrogen-containing waste products of
metabolism
Osmoregulation—
How organisms regulate solute concentrations and balance
the gain and loss of water
Why is excretion important?
Body needs to get rid of waste
Otherwise, waste will build up
Take up space
Prevent metabolic processes
Poison organism
What are the two types of
waste produced by the body?
Solid waste
Liquid waste (urea)
Where is solid waste processed?
Large intestine
Where is solid waste excreted?
Rectum and anus
Where is liquid waste processed?
Kidney
Where is liquid waste excreted?
Urinary tract
Excretory System Overview
Overview of Excretory System,
Kidney, and Nephron Structure
Kidney Structure
Be able to draw: cortex, medulla with pyramids,
pelvis, ureter, renal artery, and renal vein
Identify the components of a kidney.
cortex
medulla
renal pyramids
pelvis
ureter
renal artery
renal vein
Nephron Structure
Be able to draw a nephron
Must include
glomerulus
Bowman's capsule
proximal convoluted tubule
loop of Henle
ascending and descending
both labeled
Ascending
portion of
Loop of Henle
distal convoluted tubule
collecting duct
Descending
portion of
Loop of Henle
Identify the components of a nephron.
glomerulus
Bowman's capsule
proximal convoluted
tubule
loop of Henle
ascending and descending
portions of the Loop/Henle
distal convoluted tubule
collecting duct
Ascending
portion of
Loop of Henle
Descending
portion of
Loop of Henle
How do solutes and water get into the
proximal convoluted tubule?
High pressure in
arteries/arterioles leading
into the nephron
This leads to ultrafiltration
in the capillaries of the
glomerulus
Water and solutes such as
urea, glucose, salts, and
amino acids drain into the
Bowman's capsule
Water and solutes dumped
into the proximal convoluted
tubule
How are salt, amino acids, and water reabsorbed
into blood from the proximal convoluted tubule?
Salt (NaCl), glucose, and
amino acids are
transported back to the
blood by active transport
Water follows in to the
blood by osmosis
Solute Reabsorption Diagram
How are the cells on the wall of the proximal
convoluted tubule specially adapted for
selective absorption?
microvilli
increase the
surface area for
absorption
through active
transport
mitochondria
produce ATP
for active
transport
What happens after filtration and reabsorption?
3. Secretion
Toxins, excess ions and
other substances are
actively transported out
of the filtrate
4. Excretion
The filtrate is sent out of
the nephron and out of
the body as urine
What are some reasons an individual’s
blood solute concentration increase?
vomiting and diarrhea makes the body lose water
increased salt intake (from eating those potato chips...)
drinking alcohol adds ethanol and sugar
drinking coffee adds sugar and caffeine
excess sweating makes the body lose water
if the individual isn’t drinking enough water
Anti-Diuretic Hormone (ADH) Function
Osmo-receptors in the brain
monitor blood solute concentration
It is a hormone that is synthesized
in the brain (hypothalamus)
When solute concentrations are
high, ADH is released into the
blood stream
ADH travels to the nephrons of the
kidney and tell kidney to reabsorb
more water
This is a negative feedback control
of ADH secretion
1. Blood vessels carry blood to and from the kidney. Draw a
labelled diagram to show the internal structure of the kidney,
including the vessels that are connected to it.
(5 marks)
cortex shown at the edge of kidney;
medulla shown inside the cortex (with pyramids);
pelvis shown on the concave side of the kidney;
ureter shown connecting with the pelvis
renal artery shown connected
renal vein shown connected
IB Exam Question
IB Exam Question
2. Draw a labelled diagram of a nephron.
(6 marks)
glomerulus;
Bowman's capsule;
proximal convoluted tubule;
loop of Henle;
ascending and descending both labeled;
distal convoluted tubule;
collecting duct;
IB Exam Question
3. Which part of the nephron shown below
is impermeable to water molecules? (1 mark)
A. I
B. II
C. III
D. IV
Correct answer: C
IB Exam Question
4. Describe how the liquid and solutes that flow through
the proximal convoluted tubule are produced.
(2 marks)
high pressure in arteries/arterioles leading into the
nephron;
this leads to ultrafiltration in the capillaries of the
glomerulus;
Water and solutes such as urea, glucose, salts, and
amino acids drain into the Bowman's capsule which
leads to the proximal convoluted tubule;
IB Exam Question
5. Explain how the structure of the proximal convoluted tubule
cell is adapted to carry out selective re-absorption.
(2 marks)
microvilli increase the surface area for absorption /
active transport;
mitochondria produce ATP for active transport;
IB Exam Question
6. Name three solutes that are selectively reabsorbed
back into the blood in the proximal convoluted tubule.
(1 mark)
glucose
amino acids
salt (NaCl)
7. Describe how these solutes and water are reabsorbed
by the blood from the proximal convoluted tubule.
Salt (NaCl), glucose, and amino acids are transported
back to the blood by active transport
Water follows in to the blood by osmosis
IB Exam Question
8. Where in the kidney does ultrafiltration
take place?
(1 mark)
A. Glomerulus
B. Loop of Henlé
C. Proximal tubule
D. Collecting ducts
Correct answer: A
IB Exam Question
9. What can be changed in the kidney over a period of time
in order to carry out the process of osmoregulation?(1 mark)
A. The amount of blood flowing to the kidney
B. The amount of fluid filtered from the blood in the
glomeruli
C. The amount of solutes selectively reabsorbed in the
proximal convoluted tubule
D. The amount of water reabsorbed in the collecting
ducts
Correct answer: D
IB Exam Question
10. State three reasons why a person’s blood
plasma solute concentration may increase.
(3 marks)
vomiting / diarrhoea
increase salt intake;
drink alcohol / coffee;
excess sweating / lack of water intake;
IB Exam Question
11. How does anti-diuretic hormone
(ADH) function in osmoregulation.
It is a hormone that is synthesized in the brain
(hypothalamus)
Osmo-receptors in the brain monitor blood solute
concentration.
When solute concentrations are high, ADH is released
into the blood stream
The hormone travels to the nephrons of the kidney
and signal kidney to reabsorb more water.,
This is a negative feedback control of ADH secretion;
IB Exam Question
12. Anti-diuretic hormone has its main effect
on which part of the nephron?
(1 mark)
A. Proximal tubule
B. Bowman’s capsule
C. Loop of Henle
D. Collecting duct
Correct answer: D