UNIT 4. THE CIRCULATORY AND EXCRETORY SYSTEMS.
1.
BLOOD.
Interstitial fluid: is a liquid found among the cells. Substances are exchanged and renewed by blood, providing nutrients and taking waste products away.
Blood is a red viscous liquid that transport vital substances. Human body contains around 5’5 l of blood.
1.1.
Composition of the blood.
blood
blood plasma
water
minerals
nutrients
waste
products
urea
uric acid
Carbon
dioxide
proteins
hormones
blood cells
erythrocytes transport oxygen and carbon dioxide luekocytes protect the body from infections
dissolved (nutrients, waste products, CO2, proteins, hormones, etc.).
b) Blood cells: they are produce by bone marrow, which is found inside some bones. a. Erythrocytes or red blood cells:
Most common type of cells
They are disc shaped and have no nucleus They contain a protein called hemoglobin,
responsible of red colour of erythrocytes and blood, and which transports O2and CO2.
b. Leukocytes or white blood cells:
Different types: neutrophils, eosinophils, basophils, lymphocytes and monocytes. Protect the body from infections and
eliminate cellular waste after infections (dead cells, pieces of cells, etc.).
c. Thrombocytes or platelets:
They are not true cells, but cell fragments. They contain substances that allow blood
to coagulate and avoid hemorragies.
What is interstitial fluid and what is its function?
Make a summary scheme about the components of the blood
What is blood plasma? What is made of?
1.2.
The functions of the blood.
Transport nutrients
Collect waste products: urea, ureic acid and CO2
Transport hormones, that control a lot of body functions
Regulate temperature moving body heat from warmer areas to cooler ones Protect the body against infections
Prevent blood losses through coagulation
AB0 System:
Membranes of red blood cells contain different proteins. One type of these proteins has two forms, A and B, and it may not to be present. Therefore people can belong to:
- Group A: if all their proteins are type A
- Group B: if all their proteins are type B
- Group AB: if the cells have proteins of both types
- Group 0: it the cells don’t have proteins of neither one.
Name the functions of the blood.
Explain which types of proteins have the erythrocytes of each AB0 group.
2.
THE BLOOD VESSELS.
Arteries carry the blood away from the heart. As they get further from the heart, they are branched out into narrower arteries to the different organs. In the organs these narrow arteries are divided again into arterioles.
Arterioles continue branching out until they become to capillaries.
Capillaries are microscopic blood vessels with so thin walls that allow substances to be exchanged quickly and easily between the blood and the interstitial fluid.
Capillaries come together forming thicker vessels called venules. Venules come together into veins and thicker veins.
Veins are the vessels which let the blood to flow towards heart. Veins have valves on their walls that let the blood flow towards heart, but not in the opposite direction.
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Explain the function of each type of vessel
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3.
THE HEART
The heart is the organ which pumps the blood and makes it to move around the circulatory system. It’s a hollow organ made of muscle tissue (myocardium). It’s divided by internal wall in two halves not connected by anyway. Each half is divided into an atrium and a ventricle, connected by valves (tricuspid and mitral valves). Each atrium receives the blood of an important vein (vena cava or pulmonary vein) and each ventricle pours its blood in an important artery. The arteries are connected to the heart by valves too (semilunar valves).
https://www.youtube.com/watch?v=qmpd82mpVO4
The inner walls are covered by a thin layer of cells (endocardium) and outside is covered by a double membrane (pericardium).
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4.
BLOOD CIRCULATION.
https://www.youtube.com/watch?v=jLTdgrhpDCg https://www.youtube.com/watch?v=H04d3rJCLCE
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Lymphatic system collects and returns the excess of interstitial fluid to the bloodstream. This system is made up of lymphatic vessels and lymphatic nodes:
Lymphatic vessels:
o They begin in the capillary systems and go toward veins, joining between them in thicker lymphatic vessels.
o They are blind-ended (close at the end). o Interstitial fluid enters by filtration. Lymphatic nodes:
o They are located along the route followed by some vessels.
o They filter waste substances from lymph. o They produce lymphocytes (defensive cells)
and release them into the blood.
Functions of the lymphatic system:
It maintains the fluid balance between the interstitial fluid and the blood plasma
Protects the body from infections
They collect some products of digestion by lacteal vessels (mainly fats because they cannot travel by blood)
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6.
THE EXCRETORY SYSTEM
The excretory system is made up of:
Respiratory system: remove CO2 from the blood and expels it.
Sweat glands: they produce sweat with water and waste mineral salts. Sweat evaporates to cool the skin.
6.1.
The Urinary System.
They urinary system is made up of:
A pair of kidneys: two organs that remove waste substances from the blood and produce urine. Each one has three parts:
o renal cortex (corteza renal) o renal medulla (médula renal) o renal pelvis (pelvis renal)
Blood is filtered in millions of special cells called nephrons
(nefronas), located in the renal cortex and medulla, and waste substances are poured into the renal pelvis.
A pair of ureters: narrow tubes, about 28 cm long, that carry the urine out of the kidneys
Bladder: elastic hollow organ where urine is stored
Urethra: a tube where urine travels to exit the body. It has a sphincter which is closed unless micturition reflex occurs.
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