Download Unit 6: Excretion

Biology 30S
Excretion
Excretion
Introduction
Every metabolic process in the human body uses energy and generates wastes.
If these waste products are not removed, they would quickly accumulate in harmful
proportions. In fact, some wastes are poisonous and pose a serious threat to health if
they are not removed promptly.
The process of getting rid of metabolic wastes is called excretion.
There are many organs and systems responsible for excretion.

The ______________ removes salts and nitrogen-based wastes

The ______________ remove carbon dioxide

The _______________ converts poisons and toxins to a form that can be
eliminated by the ____________________
Homeostasis
The blood picks up:
1. _______________________
2. Excess __________________
3. _________________ compounds
4. Excess _____________that may be present in
the interstitial fluid
The blood carries these wastes to the excretory organs, which channels them out of the
body.
Therefore, the excretory system:
1. Regulates volume of internal body fluids
2. Eliminates metabolic wastes from the internal environment
Components of the excretory system in humans include:
1. ________________________
2. _______________________
3. _________________________
4. ________________________
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Biology 30S
Excretion
The Urinary System

The kidneys remove metabolic wastes from the body by filtering the
_______________.

The entire blood volume is filtered through the kidneys about ___________
times per day by way of the renal __________________. After the blood is
cleaned, it flows back into the body through the renal ________________.

The kidneys work continuously, processing all of the blood in the body every 20
minutes. At this rate, every 24 hours the kidneys filter approximately
___________ litres of blood. of these 325 litres, only ___________ litres of fluid
are excreted as urine.
The human urinary system consists of:
 Two ________________
 Two ________________
 One _______________________
 One _____________________
Why are females more prone to urinary tract infections than males?
Urethras in females are about 4 cm, and about 20 cm in males.
The shorter length makes bacterial invasion easier in females.
Normally, there are two of kidneys, one on either side of the __________ under the
lower ribs.
The ___________________ lead from the kidneys to the _____________________,
which lies low in the abdominal cavity.
The ____________________ extends from the bladder to the exterior of the body,
carrying urine through the urogenital organs (the penis or vagina).
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Biology 30S
Excretion
Structure of Kidneys

Kidneys are reddish brown in colour and shaped like kidney beans.

Each kidney is about the size of your clenched fist. If you were to cut a kidney in
half, you would see the following parts:
o ___________________ - a thin, outer membrane that helps protect the
kidney
o __________________ - a lightly colored outer region
o __________________ – a darker, reddish-brown, inner region
o ________________________ – a flat, funnel-shaped cavity that collects
the urine into the ureters
Nephrons

The ___________________________ of the kidney are microscopic structures
called ___________________.

Each kidney contains about _____________________ nephrons.

A nephron contains a network of capillaries called the ___________________,
which ________________ blood into a cup-shaped structure known as the
______________________________.
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Biology 30S
Excretion

The _________________ then passes into a series of _____________________.

Water and waste products are ____________________ from the blood by the
filtering process and the flow ______________ and _____________ of the
tubules.

Much of the water is reabsorbed by the tubules and the wastes are concentrated
into urine.
The main parts of the nephron are as follows:

______________________ - coiled capillaries inside the Bowman's capsule.

_________________________ - closed end at the beginning of the nephron. It is
located in the cortex.

______________________________________ - first twisted region after the
Bowman's capsule. It is also in the cortex.
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Biology 30S
Excretion

__________________________ - long, loop after the proximal tubule. It extends
from the cortex down into the medulla and back. It is composed of the descending
(down) and ascending (up) limbs.

_____________________________ - second twisted portion of the nephron after
the loop of Henle. It is also in the cortex.

___________________________ - long straight portion after the distal tubule that is
the open end of the nephron. It extends from the cortex down through the medulla.
It drains into to the renal pelvis.
The nephron also has a unique and rich __________________________ compared to
other organs.
Kidney Blood Supply

_____________________ - supplies blood to the kidney from the circulatory system

________________________ - connects the renal artery with the glomerular
capillaries.

____________________ – described in section above

_________________________ - connects the glomerular capillaries with the
peritubular capillaries.

_______________________________ - located after the glomerular capillaries and
surrounding the proximal tubule, loop of Henle, and distal tubule.

_____________________________ - returns blood from the kidney to the
circulatory system
Importance of Kidneys
Your kidneys are important because they do the following essential things:
1. ___________________________________

Kidneys remove excess ______________ from the body or ______________
water when the body needs more.

Salts such as ________ and __________________ must be kept at specific levels.
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Biology 30S

Excretion
When the kidneys are working properly, __________________ (and
_______________) are excreted from the body in the urine.
2. ________________________________________

Wastes produced by metabolic activities must be removed from the body.

These wastes include:
 ______________ - is made when the body breaks down protein for energy


______________ – produced when the body breaks down purines (parts of
DNA)
_____________ - is a waste product of muscle activity
As kidney function _________________, the levels of urea and creatinine in the blood
__________________. (these wastes can be detected by blood tests to indicate if your
kidneys are working properly)
3. ________________________________________

Kidneys also make important chemical messengers called ______________.
These hormones circulate in the bloodstream and regulate some body functions.

These hormones include:
o _____________________ – helps control blood pressure
o ______________________ – stimulates red blood cell production
o ______________________ – promotes calcium reabsorption in the
digestive tract
Urine Formation
The nephrons performs three main functions to produce urine:
1. __________________ - the passage of substances through the capillaries of the
_____________________ into __________________________.
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Biology 30S
Excretion
o ________________, _____________, _______________, and ____________
go into the Bowman’s capsule
o Blood ______________ and large _______________ are too large to pass
2. ______________________ - the transfer of essential solutes and water from the
______________________ back into the ______________ (into the peritubular
capillaries)
o ______________, _________________, ___________________,
___________________, and other useful substances are reabsorbed back
into the peritubular capillaries by _____________________
_______________________
3. ___________________ - the movement of materials from the ____________ back
into the ___________________.
o Excess _________________ ions, _______________, and certain __________
(i.e., penicillin)
Anything (fluid, ions, small molecules) that has not been reabsorbed from the nephron
gets swept away to form the urine, which ultimately leaves the body.
Kidneys and Water Balance
As mentioned earlier, for your body to work properly, it must contain just the right
amount of water. One of the important jobs of the kidneys is to remove excess water
from the body or to retain water when the body needs more.
A hormone called __________________________ or ADH controls water conservation
by the kidney.
Diuretics are chemicals that increase the flow of urine.
ADH is produced in the ___________________ in the brain.
Common diuretics are:
 caffeine
 alcohol
Low water levels:
 The pituitary gland is signaled to _________________ more ___________

The _______________ carries the ADH to the __________________

The _________________ of the collecting duct __________________
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Biology 30S

Excretion
_______________ water is _________________ from the collecting duct into
the ___________________.

This results in producing more ______________________ ________________
Too much water:
 __________________ ADH is released

Collecting ducts become ________________________ to water

Less water returns to the blood and the urine is ____________________
Alcohol acts as a diuretic because it inhibits the secretion of ADH from the pituitary
gland. This is why you urinate more when you drink alcohol, are so thirsty the next day,
and possibly suffer from a hangover (main cause is dehydration).
____________ water levels = __ ADH = __ urination (more concentrated urine)
____________ water levels = __ ADH = __ urination (less concentrated urine)
Kidneys and Blood Pressure
The kidneys play a role in the regulation of blood _______________ by adjusting for
blood __________________.
A hormone called ___________________ acts on the nephrons to _________________
________________________ reabsorption.
As Na+ reabsorption increases:
 The osmotic gradient increases
 ___________ water moves ________ of the nephron and into the blood by
osmosis
 More water in the blood causes = _____________________________
 Greater blood volume = _________________ in blood pressure.
__ aldosterone = __ blood volume = __ blood pressure
__ aldosterone = __ blood volume = __ blood pressure
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