Download The Circulatory System - Virtual Medical Academy

The circulatory system
The circulatory system of the human is closed type.
* Open type?
In the human, the circulatory system is formed of:
1-Cardiovascular system: consist of the heart, blood &
blood vessels.
2- Lymphatic system: composed of lymphoid vessels,
lymphoid organs& tissues.
*It takes up excess tissue fluid (extra cellular fluid) &
transports it to the blood stream.
The Cardiovascular System
1- blood:
It is kind of connective tissue which function in:
* transporting oxygen, nutrients& other solutes to cells.
* carries away metabolic waste & secretion including
hormones.
* help in stabilizing internal PH.
* has cells that fight infection.
* equalize body temperature.
Component of the blood:
1- Plasma:
It consists mostly of water, protein & ions.
Function:
* serve as transporting media for the blood cells& platelets.
* Solvent for ions & molecules including different plasma
protein.
* Some of the plasma protein transport lipids, fat soluble &
vitamins through the body.
* Some other plasma protein has a role in blood clotting or
in defense against pathogens.
2- Platelets:
*some stem cells develop into big cells called megakaryocyte
which give platelets.
* Each platelet last 5-9 days.
* They can initiate blood clotting.
3- Red blood cells ( RBCs):
* Biconcave disc-shaped cells .mature ones have no nucleus.
*originate from stem cells in bone marrow.
* They transport oxygen & carry away CO2 wastes.
4- White blood cells (WBCs) leukocytes:
* They arise from stem cells in bone marrow.
* function in daily housekeeping & defense.
* Some types engulf & target damaged or dead cells or any
other foreign things.
* They differ in shape of the nucleus, shape & staining traits
Kinds of leukocytes:
1- Granular leukocytes:
1- Eosinophils:
Secret enzymes that punch holes in the surface of the
parasitic worms.
2- Basophile:
Secret histamine & other substances that help to keep inflammation
joining after it start.
3- Neutrophils:
Phagocytize &digest bacterial cells to simple molecule pits (during
inflammation).
2- A granular leukocytes:
1-macrophage (big eaters):
*immature macrophages are called monocytes.
*play a role in defense against the parasitic worms.
*engulf &digest just about any foreign agents.
* They also help in clean up damaged tissue.
2-lymphocytes:
*T-lymphocyte & B- lymphocytes play a role in specific immune
response.
2- Blood vessels:
* They carry blood to the tissue & then back to the heart.
* They are 3 types:
1- Arteries & arterioles: carry blood away from the heart.
2- Capillaries: exchange material with the tissue.
3- Vedins & venules: return blood to the heart.
1- Arteries & arteriole:
* have thick walls consisting of:
1- An outer connective tissue layer.
2- An inner endothelial layer.
3- A thick middle layer of elastic fibres & smooth muscles.
2- Veins & venules:
* The wall of vein & venule is much thinner than that of arteriole or
artery because the middle layer of muscles & elastic fibres is poorly
developed.
3- Capillaries:
* Arterioles branch into small vessels called capillaries.
* They are narrow microscopic tubes with a thin wall composed of
only one endothelial layer.
Capillary bed:
A net-work of many capillaries present in all regions of the body.
3- THE HEART
* It is cone-shaped muscular organ located between lungs; the apex
is directed to the left.
* It consists of:
1- Myocardium: the major part of the heart. Consist largely of
cardiac muscle tissue.
2- Endocardium: endothelial tissue lines the inner surface of the
heart.
3- Pericardium: epithelial layer & fibrous covering the outer surface
of the heart.
* Internally the heart has a right & left sides separated by the
septum & has 4 champers.
# Two upper & small thin-walled chambers (atria).
#two lower &big thicks- walled (ventricles)
Valves
* The heart has 2 atrioventricular valves supported by fibrous
strings called chordae tendineae which prevent them from everting.
Atrioventricular valve:
# Tricuspid valve: on the right side; have 3 flaps.
# Bicuspid valve or mitral valve: on the left side; it has 2 flaps.
Semilunar valves:
Resemble half moon, between the ventricles & their attached vessels.
Heart is a double pump
*the right side of the heart sends the blood through the pulmonary
circuit to the lung & then back to the heart.
*the left side of the heart sends the blood through the systemic
circuit to other parts of the body & then back to the heart.
Path of blood in the heart
1-blood low in oxygen high in CO2 enters the right atrium through
superior & inferior vena cava.
2-contraction of the right atrium forces the blood through the
tricuspid valve to the right ventricles.
3- The right ventricles pumped the blood through semilunar valve
(pulmonary semilunar) to enter pulmonary artery which carry blood
to the lungs.
4-blood high in oxygen low inCO2 return from the lungs to left
atrium through pulmonary vein.
5- Contraction of the left atrium forces the blood through the
bicuspid valve into the left ventricles.
6-the left ventricles pumps the blood through semilunar valve (aorta
semilunar) into the aorta (the largest artery in the body) which carry
blood to all body tissues.
Heart beat
Cardiac cycle: is a sequence of contractions & relaxation.
Systole: refers to contraction of the heart muscle.
Diastole: refers to relaxation of the heart muscle.
* The two atria contract simultaneously & then the two ventricles
contract at the same time.
* So, atria systole is followed by ventricular systole.
* Heart contracts or beats about 70 times / minutes.
* Each heart beat about 0.85 second consisting of:
Time
atria
ventricles
0.15 sec
systole
diastole
0.30 sec
diastole
systole
0.40 sec
diastole
diastole
Cardiac conduction:
There're nodal tissues having both muscular & nervous
characteristic located in 2 regions of the heart which are:
1- SA (sinoatrial) node = pace maker:
A cluster of cell bodies found in the upper dorsal wall of right
atrium.
2- AV (atrioventricular) node:
Found at the base of right atrium very close near to the septum. It is
only an electrical bridge between the atria & ventricles.
* SA node initiates the heart beat & sends out an excitation impulse
every 0.85 second to cause atria to contract.
* when the impulse from SA node reaches AV node , it signals the
ventricles to contract by way of specialized fibres called ( pukinje
fibre) .
Blood pressure:
@ Blood pressure is the pressure of the blood against the wall of the
vessels.
@ The blood pressure is measured by using sphygmomanometer.
2- Lymphatic system:
* It is composed of drainage vessels, lymphoid organs & tissues.
* It is one way system.
* It is closely associated with the cardio vascular system because it
takes up excess tissue fluid ( extracellular fluid) & transports it to the
blood stream.
* When the fluid moves inside lymph vessels, it is called lymph.
Function of the lymphatic system:
1-helps in fighting infection.
2- Deliver pathogens, foreign cells & cellular debris from the body
tissue to the lymph vascular system disposal centre, the lymph node.
3- Drainage channels for water & plasma protein that have leaked
out of the blood at the capillary peds & must be delivered back to the
blood circulation.
4- Takes up the absorbed fat from the intestine & deliver them to
the general circulation.
Lymphoid organs & tissues;
@ They are central to the body defense against injury & attack.
@ They indicate the lymph node, spleen, thymus gland as well as
tonsils & patches of tissue in the wall of the small intestine &
appendix.
Lymph node
*lymphocytes take up a station in lymph node so help in defense.
* filter lymph so help in purifying blood.
Spleen
* has the same function of lymph nodes (largest organ)
* Store blood (reservoir of RBCs).
*contracts when blood pressure drops.
Thymus:
* Maturation of lymphocytes (T – lymphocytes)
* produce hormones that influence defense mechanism.
Main lymph vessels:
# Lymph vessels jointed to form 2 main lymph trunks:
1- Right lymphatic duct:
That drains the upper right portion of the body.
2- Thoracic duct:
That drains the rest of the body.