Unit 7 Excretion.pdf - Mrs Stovel

Unit 7 : Excretion
7.1: Excretory Organs
7.1.1 Define the term excretion.
7.1.2 Describe how excretion aids in maintaining homeostasis in the body.
7.13 Differentiate between excretion and secretion.
7.1.4 List the primary metabolic wastes produced in the human body .(CO , H20, NH3,
and mineral salts) and the source of each.
7.1.5 Compare the role. of the major excretory organs (kidneys, lungs, skin, intestine, and
liver) in the excretory process.
7.1.6 Predict the effect(s) of malfunctioning excretory organs on homeostasis in the
human body.

7.2: The Urinary System
7.2.1 Identify on a diagram and describe the function of the followinw structures of the human
urinary system: kidneys, renal cortex, renal medulla, renal pelvis, renal arteries and veins,
ureters, urinary bladder, and urethra.
7.2.2 Identify from a diagram and describe the finction of the following structures of the
nephron: afferent and efferent arterioles, glomerulus, Bowman 's capsule, proximal
convoluted tubule, peritubular capillaries, Loop of Henle, distal convoluted tubule, and
collecting duct.
7.2.3 Differentiate between the terms filtration, reabsorption, and secretion, as they relate to
nephron function.
7.2.4 Analyze and compare water and solute (glucose, protein, urea, Na,,K) concentration in
various parts of the nephron and urine.
7.2.5 Describe the role of antidiuretic hormone (ADH) in maintaining water balance in the
body.
7.2.6 Describe the role of aldosterone in maintaining blood pressure in the body.
7.2.7 Explain the effect of diuretics such as caffeine and alcohol on water loss'.

7.1: Excretory Organs
Excreh© 'The removal of waste products from the body.
Primary Metabolic Wastes:
Major Excretory Organs:
1. carbon dioxide 1. kidneys
2. water 2. lungs
3. ammonia 3. skin
4. mineral salts 4. intestine
5. liver
Maintaining Homeostasis:
The excretory organs are required to maintain homeostasis in the body. The
kidneys are the main excretory organs and if they fail to function, the other excretory
organs cannot adequately compensate to maintain a normal environment for the cells.
Sweat glands in the skin serve a minor function in excretion by removing water,
salts, and small amounts of urea, uric acid, and ammonia. Exchange across the walls of
capillaries provides nutrients and removes waste products from the interstitial spaces.
Exchange of gas in the lungs removes carbon dioxide and water from the blood and
provides a supply of oxygen. The intestine absorbs large amounts of water and salts and
concentrates undigested food into feces. The fiver removes certain waste products by
transforming them into compounds which can be eliminated by the kidneys.
The kidneys remove waste products, many of which are toxic, from the blood and
play a major role in controlling blood volume, the concentration of ions in the blood, and
the pH of the blood. The kidneys are also involved in the control of rbc production and
vitamin D metabolism.

Cotes if FLUID 1NTAK6 qk FL(JID OtITP[TT
An imbalance may result from the following circumstances which
cause a high fluid output
* High amounts of urine may be lost due to consumption
of diuretics or from some sort of kidney malfunction
* High amounts of perspiration may occur in hot weather,
during exercise or extremely stressful situations
* Increased exhalation due to exercise, etc...
* Prolonged bouts of diarrhea
Any of the above can be balanced with a fluid intake that is equal
to the output, but combined with a low fluid intake, the body can
become dehydrated. If the body becomes dehydrated, i.e. if output
exceeds input, then the body will attempt to restore homeostasis
according to the following chart:
if autzrt exceeds trnake In (or if this 46 of dehgdration occvrsk
1% - a thirst sensation will be generated in order to get the
lost fluids replaced
water will be removed from the urine (less urine)
296 - pain and collapse will occur in the bodies attempt to
conserve water - exhalation will be reduced
1096 - death

The Ro oft a ^ ^r its cr ti n:
1. - The liver transforms toxins (Ex. alcohol & heavy metals)
into soluble compounds that can be eliminated by the
kidney
2. - The;iiver also transforms hazardous products of protein
metabolism into safer products that can be eliminated by
the kidney (ex. ammonia is converted to urea)
Two main Rol s of e th Ki y
1. - Excretion of Nitrogenous and other wastes
2. - Maintaining'Homeostasis
^+ i^eL7C^LE..
• r
Component
Water 95
Urea
Uric Acid 2
Creatinine 1.5
Salt Ions
(Na, GI,,K Ca). _ 1.4
Ammonia .05
Ketones .03
Urochrome .02
Where the comporten t is from
from food and drink..
from detoxified ammonia
broken down nucleic acids(DNA)
from muscles as they work
from food and drink
from breaking down proteins
from broken down body fat
from broken down blood cells
(gives urine its yellow color)

Figure B-62 FLUID BALANCE '
H0
COMPONENT coMPOSm of .
(g/100 m L)
rwater ., +955.0.
urea 2.0
cr, tinine 1.5
ium ions 0.5
chloride ions 0.4
potassium ions 0.15
aIc um ions { .1€
ammonia 0.05

How the Kidney Maintains Homeostasis
Recall that to maintain homeostasis means to keep the internal system working at a balanced
state, to keep the level of substances at a constant level.
There are six main ways that the kidney helps to maintain homeostasis:
1. Controlling the Blood Sugar Level (BSL)
If the BSL is too low, the nephrons will actively transport a higher amount of sugar from the
filtrate back into the blood. If the BSL is too high, the nephrons will retain the sugar that is
contained in the filtrate and this sugar will exit the body in the urine. In this way, the BSL is
kept constant.
2. Controllin the Water and Salt Level of the Blood Osmore lation
If the blood contains too much water, the kidneys will produced a higher volume of urine. If
the blood doesn't contain enough water (dehydrated), the kidneys will produce a lower
volume of urine. Similarily, if the blood contains too much salt, salt will not be reabsorbed
from the filtrate by the blood, in fact if there is a lot of salt in the blood, the excess salt will
be secreted from the blood into the filtrate. In this way, the excess salt will exit the body in
the urine. If the blood is low on salt, any salt in the filtrate will be sent back to the blood by
the nephron. This function of the kidney is accomplished with the aid of hormones.
3. Controlling Blood Pressure-(BP)
If the BP is too high, water and/or salt will be removed from the body in the urine. Blood
with a lower water and/or salt content will have a lower pressure. Conversely, if the BP is too
low, the kidney will retain the water and/or salt and send it back to the blood so that the
blood pressure will rise back to the normal level. This function of the kidney is also
accomplished with the aid of hormones.
4. Controllin the Acid and Base Level of the Blood (RM
If the blood is too acidic or too basic, hydrogen ions (H+) or hydroxyl ions (OH-) will be
retained in the filtrate and as well will be secreted from the blood into the filtrate - these
excess ions will then exit the body in the urine.
Controlling Red Blood Cell (rbc) Production
If the number ofrbc's in the blood stream is low, the kidney has the ability to sense this and
will release a hormone called erythroprotein, that in turn tells the bone marrow to make more
rbc's.
6. Nitrogenous Waste Excretion
Eating and digesting proteins, a necessary nutrient in the diet, results in the production of
chemicals that contain nitrogen. These chemicals are called nitrogenous wastes. If not
discarded, these nitrogenous wastes will accumulate in the blood and will eventually become
toxic. The nephrons filter nitrogenous wastes out of the blood and these wastes then exit the
body in the urine. Nitrogenous wastes are also secreted from the blood into the filtrate. The
level of nitrogen wastes in the blood is thus lowered because of the action of the kidneys.