Download 4. nutrition: the circulatory and excretory systems.

4. NUTRITION: THE
CIRCULATORY AND
EXCRETORY SYSTEMS.
INTRODUCTION.
DISCUSS THE FOLLOWING QUESTIONS.
Why is blood so important?
What is the relationship between blood and the heart?
How does the body get rid of waste products?
1. THE INTERNAL ENVIRONMENT AND BLOOD.
Blood is a viscous fluid with a salty taste which
flows inside the vessels of the circulatory
system. The human body contains around 5.5
litres of blood.
1. THE INTERNAL ENVIRONMENT AND BLOOD.
1.1 COMPOSITION OF BLOOD.
1.1 COMPOSITION OF BLOOD.
BLOOD PLASMA: is a yellowish substance
made up of water containing various
dissolved molecules: minerals, nutrients,
waste products (urea, uric acid, CO2), proteins
and hormones.
1.1 COMPOSITION OF BLOOD.
•THERE ARE THREE TYPES OF CELLS:
ERYTHROCYTES or red blood cells:
-Most common. 99%
-Haemoglobin.
-120 days living.
1.1 COMPOSITION OF BLOOD.
•THERE ARE THREE TYPES OF CELLS:
LEUCOCITES or white blood cells:
-There are fewer white blood cells than
red ones
-Neutrophils, eosinophils, basophils,
lymphocytes and monocytes.
-Protect the body from infections.
1.1 COMPOSITION OF BLOOD.
•THERE ARE THREE TYPES OF CELLS:
TROMBOCYTES:
-Not true cells but cell fragments.
-They contain enzymes that allow the
blood to coagulate preventing
hemorrhage
1.2 THE FUNCTIONS OF BLOOD.
•TRANSPORT.
•COLLECT WASTE PRODUCTS (UREA, CO2…)
•REGULATE TEMPERATURE.
•PROTECTION.
•HEMOSTASIS.
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2.1 THE BLOOD VESSELS.
As arteries get further away from the heart, they gradually
branch out into narrower vessels leading to the different
organs. These vessels then divide into even smaller ones
called arterioles.
2. THE BLOOD VESSELS.
3. THE HEART.
In order for the blood to move around the circulatory system,
it needs to be pumped by the heart. Cells depend on the heart
to receive a constant supply of nutrients and oxygen. Poor
heart function can have fatal consequences.
3. THE HEART.
The heart is a hollow organ made of muscle tissue. It is
divided into two halves, right and left, by an internal wall. The
two halves are not connected in any way.
3. THE HEART.
Each half is then divided again into a small upper chamber,
the atrium, and a larger lower chamber, the ventricle.
Between the atrium and the ventricle on each side, there is a
valve: the atrioventricular valve. This allows blood to flow
from the atrium to the ventricle, but not vice versa.
3. THE HEART.
Several veins lead to the atria: two venae cavae on the right
and four pulmonary veins on the left. Two arteries lead away
from the ventricles: the pulmonary artery (on the right) and
the aorta (on the left). The semilunar valves prevent blood
from flowing back to the heart after it has left.
3. THE HEART.
3. THE HEART.
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2.2.1 HEARTBEAT.
Each heartbeat has three phases: atrial systole, ventricular systole and
diastole.
ATRIAL SYSTOLE: the atria contract and the blood is pumped into the
ventricles via the open atrioventricular valves.
2.2.1 HEARTBEAT.
VENTICULAR SYSTOLE. The ventricles contract, the semilunar valves
open, and the blood flows out into the pulmonary artery and the aorta. At
the same time, the atrioventricular valves close.
2.2.1 HEARTBEAT.
DIASTOLE. The heart relaxes and draws flood from the venae cavae and
pulmonary veins. This blood flows into the atria.
2.3. BLOOD CIRCUITS.
Blood is constantly pumped around a circuit of blood vessels (arteries,
capillaries and veins) by the heart. In humans, this circuit has two
parts: pulmonary circulation and systemic circulation.
Pulmonary artery leads
away from the heart and
splits into two arteries
which each lead to a lung.
The blood starts in the left
ventricle and flows along
the aorta, which splits into
arteries, arterioles and
capillaries. These lead to
all body tissues and organs
except the lungs.
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3. THE LYMPHATIC SYSTEM.
Water and solutes from blood plasma filter out the capillaries into the spaces
between the cells in the body tissue. These spaces are filled with a fluid known
as the interstitial fluid. Excess interstitial fluid is collected, and then
returned to the bloodstream, by the lymphatic system.
3. THE LYMPHATIC SYSTEM.
3. THE LYMPHATIC SYSTEM.
This system is made up of lymphatic vessels and lymph nodes.
•Lymphatic vessels. These include lymphatic capillaries in
the body tissues. They join together to form progressively
larger ducts called lymph-collecting vessels, which lead back
to the veins of the circulatory system.
•Lymphatic nodes. These organs are located along the route
followed by some lymphatic vessels. They produce
lymphocytes, release them into the vessels and filter waste
substances out from the vessels.
3.1. FUNCTIONS OF THE LYMPHATIC SYSTEM.
FUNCTIONS OF THE LYMPHATIC SYSTEM.
•It maintains the fluid balance between the interstitial fluid
and the blood plasma.
•It helps protect the body from infection.
•It collects the products of fat digestion in the small
intestine.
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4. THE EXCRETORY SYSTEM.
The excretory system is made up of the urinary system and a
number of other organs and systems that contribute to the
excretion of waste products.
•Respiratory system. This removes carbon dioxide from the
blood and expels it from the body.
4. THE EXCRETORY SYSTEM.
•Sweat glands. They produce sweat, which evaporates to cool
the skin. Some excretory substances are also expelled from the
body in sweat.
4. THE EXCRETORY SYSTEM.
•Liver. This organ eliminates products resulting from the
breakdown of haemoglobin from old red blood cells. It is also
eliminates a small amount of cholesterol and some toxic
substances.
4. THE EXCRETORY SYSTEM.
•Urinary system. This is the most important part of the
excretory system. It eliminates waste products in the form of
urine.
4.1 The Urinary system.
THE KIDNEYS.
These two organs are at the back of the abdomen (one on each
side). Each kidney has an external part (cortex) and an internal
part (medulla), and a hollow chamber (renal pelvis).
URINE is formed in the cortex and
medulla. It contains excretory
substances and drains into the
renal pelvis.
4.1 The Urinary system.
THE KIDNEYS.
Each kidney is made up of over a million nephrons, small tubes
with an open end surrounded by a capillary. They filter the
blood to produce urine.
4.1 The Urinary system.
THE KIDNEYS.
Nephrons are made up of several parts:
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4.1.2 Urinary tract.
THE URETERS, THE BLADDER AND THE URETHRA.
Urine is collected from the kidneys, stored, and then expelled from
the body. There are different organs for these functions.
•URETERS. There are two narrow tubes, around 28 cm long,
connecting the renal pelvis of the kidney to the bladder.
4.1.2 Urinary tract.
THE URETERS, THE BLADDER AND THE URETHRA.
•BLADDER. An elastic sac where urine collects before it is
expelled from the body. When the bladder fills up with urine, a
nervous stimulus makes the bladder contract and push the
urine out (via urethra).
4.1.2 Urinary tract.
THE URETERS, THE BLADDER AND THE URETHRA.
•URETHRA. This duct leads to the outside of the body.
In men, the urethra is connected to the reproductive system.
This means that urine and semen pass through it (at different
times). In women, the urethra is separate form the
reproductive system.
4.2 Urine formation.
PRODUCTION OF URINE.
Urine is a liquid obtained from the blood and made up of water,
various minerals, and different waste products (mainly urea and
uric acid). Urine is produced in two phases:
GLOMERULAR FILTRATION: this process filters the water and
most of the solutes circulating in the blood plasma. The liquid that
enters Bowman´s capsule is similar to blood plasma but does not
contain proteins.
TUBULAR REABSORPTION: as they travel through the
nephron´s tubule, a lot of filtered substances are reabsorbed,
including nutrients, vitamins, amino acids, etc.
Water is reabsorbed in the loop of Henle, and the other
substances are reabsorbed in the proximal tube. Waste
substances are nor reabsorbed.
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