Transcript Document

HUMAN EXCRETORY SYSTEM
The role of liver in excretion:
1. Detoxification: The liver removes harmful substances
such as bacteria, certain drugs and hormones from blood.
Within the liver these substances are changed into
inactive or less poisonous forms. It detoxifies the blood.
2. Excretion of bile
3. Formation of urea: Amino acids are the breakdown
products of proteins. Because excess amino acids cannot
be stored in the body, they are broken down in the liver.
The parts of the amino acids are changed into other
substances. From each amino acid, the amino group (NH2)
is changed into ammonia (NH3). The reminder of the
amino acid molecule is either changed into pyruvic acid
and used as an energy source in cellular respiration. Or it
is changed glycogen or fat for storage.
Formation of Urea
urea
HO
O
H
C
C
Growth and repair
NH3
(ammonia)
NH2
R
HO
amino acid
O
H
C
C
NH2
R
carbon skeleton use as
energy source or converted
to glycogen or fat
Ornithin Cycle
NH3
CO2
H 2O
Ornithine
Citralline
Urea
NH3
H 2O
Arginine
H 2O
The Urinary System
The Urinary System
The Urinary System
The urinary system is made up of:
Kidneys
Ureters
 are the
organs that
produce urine
 urine
passes from
each kidney
through a
tube called
ureter
Bladder
 urine is
stored here
Urethra
 during
urination, the
stored urine
travels from the
bladder to the
outside of the
body through
urethra
Kidney Structure
The kidneys are important for 2 reasons:
 They remove the wastes of cellular metabolism from the
blood
 They regulate the concentrations of the substances found
in the body fluids
Kidney Structure
The kidney has 3
parts:
 the outer
part is the
cortex (kabuk)
 the middle
part is the
medulla (öz)
 the inner
region is the
pelvis
(havuzcuk)
Kidney Structure
 Blood is filtered in
the cortex.
 The medulla is made
up of tubes called
collecting ducts. These
ducts carry the
filtered substances
(filtrate) to the pelvis.
 Pelvis is the cavity
connected to the
ureter. Urine formed
from the filtrate
drains from the pelvis
into the ureter.
Nephrons
Nephrons
 Nephron is the functional unit of kidneys.
 Each kidney has about 1.25 millions of nephrons.
 A nephron is composed of:
Malpighi body + proximal + loop of Henle + distal + collecting
tubule
tubule
duct
Malpighi body = glomerulus + Bowman’s
capsule
3. Bowman’s
capsule
4. proximal
tubule
2. glomerulus
1. afferent and efferent
arteriole
5. loop of Henle
MEDULLA
6. distal
tubule
CORTEX
7. collecting
duct
Nephrons
 The glomerulus is a group of capillaries
that form a tight ball.
 It is surrounded by a double-walled,
cup-shaped structure which is called
Bowman’s capsule.
 From the blood in the glomerulus,
substances are filtered into Bowman’s
capsule.
 The filtrate exits Bowman’s capsule
through the renal tubule, a long tubule
that empties into a collecting duct.
 The middle section of the renal tubule
forms a long loop called the loop of Henle
which extends into the medulla.
Nephrons
 The collecting duct which receives the filtrate from many
nephrons, leads from the medulla into the pelvis.
 Blood enters the kidneys through the renal artery, and
leaves the kidneys through the renal pelvis.
 Each nephron has one arteriole that carries blood from
the renal artery to the nephron. The arteriole branches to
form the renal capillaries that make up the glomerulus.
 Before leaving Bowman’s capsule, the capillaries join
together into a single arteriole. The new arteriole subdivides
into a second capillary network that surrounds the renal
tubule.
 The capillaries then merge again, this time to form a
venule. This pattern of blood flow around the nephron is
unusual because there are two sets of capillaries, rather
than one between the arteries and veins.
Urine Formation
Filtration
• Both useful
substances and wastes
are removed from the
blood.
Filtration:
Reabsorption
• Some of the useful
substances reenter the
blood to be used by the
body.
- takes place in the glomeruli and Bowman’s
capsule
- the blood that enters a glomerulus is under
pressure
Net filtration = blood – plasma protein + Bowman’s capsule
pressure
pressure
osmotic pressure
pressure
= 70mmHg - (32mmHg + 14mmHg) = 24 mmHg
GLOMERULAR CAPILLARIES SYSTEMIC CAPILLARIES
Since they are found between two
arteries (arterioles), blood pressure
remains along the capillaries.
Since they are found between the
arteries and veins blood pressure drops
as blood passes from the arteries to
the veins.
Blood pressure is about 70mmHg.
Blood pressure is 35 mmHg at the
arteriole end and 15 mmHg at the
venule end.
The wall of the glomerular capillaries is
covered with capillary endothelium and
Bowman’capsule endothelium. These
layers prevent exit of the blood cells
and blood proteins from the glomerular
capillaries and make the glomerular
capillaries resist to high blood pressure.
The wall of the blood capillaries is
covered with a single layer of
endothelium. This layer cannot prevent
the passage of blood proteins and white
blood cells out of the blood.
They are more permeable because they
have high amounts of pores. The blood
pressure is higher than the osmotic
pressure of the plasma proteins in the
glomerular capillaries so glomerular
capillaries make only filtration.
At the arteriole end filtration, at the
venule end reabsorption occurs.
Urine Formation
FILTRATION:
• Filtration takes place in the glomeruli and Bowman’s
capsules.
• The blood that enters a glomerulus is under pressure
Net filtration pressure=(blood pressure –(protein osmotic
pressure+ Bowman’s capsule pressure))
Net filtration pressure= (70mm-Hg – (32mm-Hg + 14 mmHg)) = 24 mm-Hg
• The pressure forces the filtrate, which includes water,
urea, glucose, amino acids, and various salts through the thin
walls of the glomerulus into Bowman’s capsule.
*Blood cells and blood proteins are too large to pass through
the walls of the glomerulus. They remain in the blood.
• The filtrate that enters the Bowman’s capsule is like blood
plasma, but it does not contain blood proteins.
Urine Formation
• The kidneys form about 180 liters of filtrate in a 24-hour
period. However, only about 1- 1.5 liter of urine is actually
produced by the kidneys in 24 hours.
• In a minute, 125 ml filtrate is formed.
• If blood pressure of renal artery is higher than 180mm-Hg
or lower than 80 mm-Hg, human body loses its auto control.
Urine Formation
REABSORBTION AND TUBULAR SECRETION:
@
• After the filtrate has left Bowman’s capsule, reabsorption
occurs in the renal tubule. It is the process of reabsorption
that reduces the volume of filtrate and returns various
important substances to the blood for homeostasis.
• During filtration 125 ml of fluid passes into the Bowman’s
capsule in one minute. 124 ml of this fluid is reabsorbed into
the blood.
• Reabsorption occurs by osmosis, diffusion and active
transport.
• Every substance in the blood has a threshold level. If the
amount of a substance in the blood is over the threshold level,
it is not reabsorbed through the tubules of nephron, instead it
is excreted with urine. (For example: in a healthy person’s
blood for each 100 ml of blood there is 180 mg of glucose. If
the amount of glucose is increased in the blood, glucose is
observed in the urine )
Urine Formation
Urine Formation
I. IN PROXIMAL TUBULE
@
Most of the filtrate, (about 80%) that has passed from the
Bowman’s capsule is reabsorbed by active and passive
transport in the proximal tubule.
•
From the filtrate glucose, amino acids, vitamins,
various ions (Na+, K+ , Ca+2, Mg+2, HCO3- , PO4-3,SO4-2),
urea, and uric acids are reabsorbed.
•
Na+ is reabsorbed by active transport.
•
Cl- is reabsorbed by diffusion.
•
H2O is reabsorbed by osmosis.
•
Creatinin is not reabsorbed.
•
Glucose, amino acids and K + are reabsorbed by
active transport.
•
Some excess and foreign substances (creatinin,
penicillin, H+, NH3) are taken from the blood by
proximal tubule cells and secreted into filtrate.
Urine Formation
II. LOOP of HENLE
@
•
The filtrate is concentrated in the loop of Henle.
•
Descending loop is permeable to water but impermeable
to salt (NaCl)
- Water is reabsorbed by osmosis at the descending
loop
- The filtrate becomes hypertonic
•
Ascending loop is permeable to salt (NaCl) but
impermeable to water.
- NaCl is reabsorbed by diffusion at the lower (thinner)
part but NaCl is reabsorbed by active transport at
the upper (thicker) part.
- The filtrate becomes hypotonic
Urine Formation
III. DISTAL TUBULE
@
•
Once the filtrate is in the distal tubule, its composition is
determined.
•
Distal tubule is impermeable to urea.
•
Re-absorption of water takes place under the control of ADH
(vasopressin) according to body’s water requirement.
•
Re-absorption of Na+ and secretion of K+ take place under the
control of aldosteron according to body’s requirement.
•
Reabsorption of Cl- by passive transport follows the
reabsorption of Na+ by active transport.
•
Reabsorption of Ca+2 takes place under the control of
parathormone according to the body’s requirement.
•
Distal tubule regulates the blood pH (7.4)
-When pH of blood drops, through the cells of distal tubule,
reabsorption HCO3-, and secretion of H+ increase with NH3
- When pH of blood increases, through the cells of distal tubule
reabsorption of HCO3- , and secretion of H+are decreased.
Urine Formation
IV.
•
•
•
•
•
•
•
COLLECTING DUCT
@
Urine is concentrated in the collecting duct.
The lower part of the collecting duct is permeable to urea.
By diffusion, urea passes in to the tissue fluid of medulla,
and with NaCl it increases the osmotic pressure of the
medium (hypertonic medium). With this change, water is
reabsorbed (under the control of ADH) and urine is
concentrated.
Healthy adult people produce 1500ml urine per day.
Urine consists of (95-96%) water, remaining is urea, uric
acid, creatinin, and mineral salts.
A healthy person’s urine does not contain blood cells,
plasma proteins, glucose, and amino acids.
pH of urine is between 4.7-8.0. pH of urine changes
according to physiological conditions and nutrition of the
person.
Urine Formation
TUBULAR SECRETION
@
Not all materials are subjected to the filtering and
selective-reabsorbtion strategy. Some larger molecules,
such as penicillin, by pass the pores of the glomerulus’s
and are actively removed from the blood in the second
bed of capillaries adjacent to the tubules. This tubular
secretion supplements glomerular excretion and increases
the efficiency of the overall excretory regulation of
blood composition.
Tubular secretion is actually a misnomer since it is the
second bed of capillaries, not the tubules, that does not
the secreting.
Urine Formation
@
EXCRETION IN PLANTS
EXCRETION IN PLANTS
Gas Exchange:
In green plants, not all metabolic wastes are excreted; some are
used by the plants. This is true to some extent for oxygen and
carbondioxide. Plants carry on cellular respiration both day and
night. Oxygen, which is needed for cellular respiration, is a by
product of photosynthesis. During the day, when photosynthesis is
occuring, some of the oxygen produced is used for cellular
respiration. The rest diffuses out of the plant through the
stomates of the leaves. Carbondioxide, which is an end product of
cellular respiration, is used in photosynthesis. Thus, during the
day, the carbondioxide produced by cellular respiration is used in
photosynthesis. At night, when there is no light reactions of
photosynthesis going on, carbondioxide is excreted through the
stomates and lenticels.
EXCRETION IN PLANTS
Nitrogenous and Other Wastes:
Nitrogenous , or nitrogen containing, wastes are normally excreted
by animals, but may be used by plants. When, for example, there
are excess amino acids, the amino group (NH2) is removed, and the
nitrogen is used in the synthesis of other compounds required by
the plants.
Other wastes may be stored within vacuoles in in certain cells,
either in solution or as crytals. Spinach, for example, stores oxalic
acid crytals in the vacuoles of its leaf cells.
Actively dividing meristematic cells grow away from their waste
materials. The wastes are simply left behind in the cells produced
by these tissues.