Measuring the blood pressure
احياء لغات - الباب الثانى| Blood Pressure
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Measuring the blood pressure
Due to the heart beating, the heart pushes the blood to the body through arteries and veins easily.
The blood is a viscous liquid can't move easily through the microscopic blood capillaries, so the blood need a pressure to move through it therefore, it causes resistance.
The resistance increases the blood pressure in the network of the arteries.
Systolic blood pressure is the maximum blood pressure in the arteries that close to the heart during the contraction of the ventricles.
Diastolic blood pressure is the minimum blood pressure in the arteries that close to the heart during the relaxation of the ventricles.
The blood pressure reading is expressed as two figures the first (Systolic blood pressure) higher than the second Diastolic blood pressure.
Measuring the blood pressure
Sphygmomanometer
It is an instrument that used to measure
the blood pressure.
Sphygmomanometer give 2 numbers
as 120/80 mm Hg in normal youth.
The no.120 indicate Systolic
blood pressure but 80 indicate the
Systolic blood pressure is the maximum
blood pressure in the arteries that close to the heart during the contraction of the ventricles 120 mm Hg but it decrease until reach 10 mm Hg in blood capillaries and veins therefore the presence of the internal valves of vein help the blood to return back to the heart .
The blood pressure increase gradually in old ages so, it needs to treat before it reaches the dangerous cases.
The structure of Mercurial sphygmomanometer
• It consists of mercury tube connected
to graduated scale.
• The blood pressure is measured
according the height of mercury column.
• A cuff is connected to the instrument
and placed around the upper arm.
• By using a Stethoscope the doctor can
hear the contraction of the ventricles
and distinguish the point of the systolic
blood pressure and distinguish diastolic
blood pressure when the sound disappear.
• The blood pressure can be measured when the heart beat and between beat and the next and also by the digital instruments but the mercury instrument is more accurate.
The blood circulation
1- Pulmonary circulation 2- Systematic circulation 3- Hepatic circulation
1. Pulmonary circulation
It starts from right ventricle & ends at left atrium.
When the right ventricle contracts,
the tricuspid valve shuts & the deoxygenated
blood rushes into the pulmonary artery and
the Simi-lunar valve is closed preventing the
returning back of the blood to the heart
The pulmonary artery divide into two branches, each
branch divides again into small branches till it ends
at blood capillaries around alveoli.
• Through the blood capillaries water vapour & CO2
come out the blood & O2 get into the blood
This is called exchange of gases so, the blood now become oxygenated.
• The blood returns from the lungs to the left atrium through the 4 pulmonary veins.
• The left atrium contracts pushing the blood down to the left ventricle through the bicuspid valve.
2- Systematic circulation
• It starts from the left ventricle
& ends at the right atrium.
• When the left ventricle contracts the bicuspid
valve shuts & Oxygenated blood rushes into
the aorta & does not go back to the heart.GR
• The aorta branches into arteries. Each artery
enters to an organ of the body and endat a
network of blood capillaries distributed
between the body tissues & cells
• Exchange of material between the blood &
the cells takes place where the cells receive
O2 & foodstuffs from the blood & the blood
receives CO2 , H2O & wastes.
• Exchange of substance takes place by
diffusion & active transport through the walls
of the blood capillaries.
The 2 sides of the heart, right & left contract at the same time, so that pumping of the oxygenated & deoxygenated blood takes place at the same time.
3- Hepatic portal circulation
The blood capillary of the villi, carrying digested food stuffs, collect to form larger venules, These venules form a large vein called hepatic portal vein that enters into the liver The hepatic portal vein also receives other veins coming from the pancreas, the spleen & the stomach.
The hepatic portal vein branches into smaller venules that end at blood capillaries distributed between the hepatic cells, Through the blood capillaries sugars & amino acids diffuse into the hepatic cells where some changes occur.
The blood leaves the liver through the hepatic vein to join the upper part of the inferior vena cava just before it opens at the right atrium.
NB.
The hepatic portal vein is the only vein begins & ends by blood capillaries.
The liver is the only organ that receives an artery as well as a vein.
The hepatic portal vein and the hepatic vein are the only veins connected
together by blood capillaries
Summary:
1- Pulmonary circulation
Rt. Ventricle pulmonary artery Lungs 4pulmonary vein Lt Atrium
2- Systematic circulation
Lt. ventricle aorta body organs superior & inferior VC. Rt. atrium
3- Hepatic portal circulation
Villi blood capillaries hepatic portal V. hepatic V. Inf.V.C Rt. Atrium
Formation of the blood clotting
• The blood clots if it is exposed to the air or the cells are exposed to rough surface.
The mechanism of the blood clotting
• When the blood is exposed to air or to rough surface, as damaged blood vessels & cells, the blood platelets with the damaged cells form a protein substance named thromboplastin.
• In the presence of Ca++ ions, thromboplastin activates inactive prothrombin into active thrombin (prothrombin is formed inside the liver by the help of vitamin K It is then passed directly to the blood) .
• Thrombin catalyses the conversion of soluble protein found in the blood named fibrinogen into Insoluble fibrin.
• Fibrin precipitates as a network of fibers, the blood cells aggregate at that network forming the clot, which blocks damaged area at the vessel, so that bleeding stops.
1- Blood platelets + destroyed cells clotting factors thromboplastin.
2 -Prothrombin Thromboplastin +clotting factors, Ca++ thrombin
3- Fibrinogen thrombin Fibrin
Why blood does not clot inside blood vessels?
Because:
1. Blood runs inside blood vessels in a regular speed and does not slow down.
2. Blood platelets slide easily and smoothly inside the blood vessels in order not to be broken.
3. The liver secretes a substance called heparin that prevents the conversion of thrombin into thrombin
N.B
During blood clotting the action of heparin stops
The lymphatic system is the immunity system of the body because it has the ability to protect the body against the harmful bacteria and the foreign particles and produce the antibodies which responsible for the body immunity.
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