Organ Systems The circulatory system The circulatory system.
Circulatory Sy Tm
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Transcript of Circulatory Sy Tm
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Norfazlina Baharuddin
Asasi UiTM
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Objectives
By the end of this chapter student should be able to:
1. Describe the function of the circulatory system
2. State and describe the composition and function of the blood
3. Differentiate between organisms without any circulatory system, organism with open and closed circulatory system
4. Differentiate between single and double circulation
5. Explain the structure of the heart, arteries and veins.
6. Explain the physiology of the heart and blood circulation
7. Describe the lymphatic system
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Introduction
Circulatory system/ Cardiovascular system
Greek:
*Kardia means heart
*vas means vessel.
It consists of heart, blood, and blood vessels.
There are two different types of the circulatory system: open circulatory system and closed circulatory system.
Most of vertebrates have a closed circulatory system, whereas most invertebrate have an open circulatory
system.
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Circulatory system function
The vertebrate circulatory system
performs several
function:
1.Transport nutrient
from the digestive
system and from
storage depots to
each cell
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Circulatory system function
2.Transport oxygen and CO2
3. Transport metabolic waste from each cell to
organs that excrete them
4. Transport hormones from endocrine glands to
target tissues.
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Circulatory system function
5. Helps maintain fluid balance (homeostasis)
6. Defends the body against invading organism
7.It helps maintain body temperature by
transporting heat (particularly important for
endothermic animals birds,mammals
8. Helps stabilize the pH
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Blood composition and function
The circulatory system of human contains 4-6
liters of blood.
Blood consists of cells (45%) suspended in
plasma (55%) where
both can be separated
by spinning a blood
sample in a centrifuge.
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Plasma
(55%)
Water (90%)
Substances (10%)
Salts
Plasma Protein
Nutrients
Waste product
Respiratory gases
Hormone
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Blood composition and function
Inorganic salts (electrolytes)
Function:
i. Maintaining the osmotic balance between the
blood and the interstitial fluid
ii. Keeping the pH of the blood at 7.4 (pH buffer)
iii. Regulate the permeability of cell membranes
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Blood composition and function
Plasma protein function:
Albumin : Help maintain osmotic balance and pH
Fibrinogen : Blood clotting
Immunoglobulin : Body defense
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Blood
Red blood cell
ErythrocytesWhite blood cell
Leukocytes
Basophil Neutrophil Monocytes Eosinophil Lymphocytes
Platelet
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Blood composition and function
Red Blood Cell
RBC lack nuclei and mitochondria
Are biconcave disks shaped, thinner in the center than on the sides. (provides for more surface area for gas
exchange).
Formed in the bone marrow
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Blood composition and function
RBC circulated in the blood for three to four months before they get worn-out
Worn-out RBC are broken down at the liver where enzymes digest the amino acids to make
other proteins
Iron is returned to the bone marrow to make more RBC
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Blood composition and function
White blood cell (WBC)/Leukocytes-body defense
Most spend their time in the interstitial fluid fighting against infection. They are synthesize in
the bone marrow.
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Blood composition and function
i. Basophils
Helps fight infection by releasing the chemical
histamine.
Histamine dilates blood vessels and allow other
white blood cells to move out of the capillaries to
the tissues
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Blood composition and function
ii. Neutrophils and Monocyte - are phagocytes
Fight bacteria, foreign proteins that enter body through wound and help the tissue heal by removing cellular debris (dead cells) Monocyte
Neutrophils
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Blood composition and function
iii. Eosinophil - is a phagocyte that fights by parasitic protozoans and worms. They also
reduce allergy attacks
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Blood composition and function
iv. Lymphocyte - key
cell in immunity which
defends the body by
producing antibodies
which are proteins that
react against foreign
substances. Other
lymphocytes fight
viruses and cancer
cells.
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Blood composition and function
Platelets
Help in blood clotting together with the plasma protein fibrinogen.
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Blood composition and functionBlood clotting (3 phases):
Constriction of blood vessels at site which slows blood loss.
Platelets becomes sticky and formed a plug to seal the site temporarily
Fibrin clot trap blood cells
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Blood composition and function
Clotting factors (platelets and damaged
cells) activates the prothrombin protein to
convert it into the
thrombin protein.
Thrombin then converts fibrinogen into
a threadlike protein
called fibrin
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Circulatory System
Some invertebrates have no circulatory system, some have an open circulatory system and
some have a closed circulatory system.
Many small and aquatic invertebrates have no
circulatory system
These are for cases of animals whose body cells are not arranged in numerous layers.
To them, a gastrovascular cavity provides adequate internal transportation.
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Circulatory system
In cnidarians, their gastrovascular cavity
serves as the circulatory
system as well as a
digestive organ.
The animals tentacles capture prey and deliver
it through the mouth and
into the cavity, where
digestion occurs.
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Circulatory system
The digested nutrients will diffuse across the cell lining to the cells at the outer layer.
As they stretches and contracts, movements in the body will stir up the contents of the
gastrovascular cavity and help distribute
nutrients.
Therefore, circulation is aided by contractions of muscles of the body wall.
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Circulatory system
For flatworms e.g. the planaria, circulation is not necessary because their flattened body permits
effective gas exchange via diffusion.
Their branched intestine also brings nutrients close to all cells.
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Circulatory system For pseudocoelomate (false cavity)
Animals such as nematodes, fluid in the body cavity helps circulate materials.
Contain complete digestive tract with mouth and anus (the tube-within-a-tube plan), no blood vascular system or
specialized respiratory organs
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Coelomates (also known as eucoelomates "true coelom") have a fluid filled body cavity called a coelom
with a complete lining called peritoneum derived from
mesoderm.
Pseudocoelomate animals have a pseudocoel(literally false cavity), which is a fully functional body cavity. Tissue derived from mesoderm only partly lines
the fluid filled body cavity of these animals
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Circulatory system Many invertebrates have an open circulatory system
such as arthropods and mollusks.
An open circulatory system is a system in which the heart pumps blood into vessels that have open
ends.
Instead of capillaries, blood vessels join directly with open sinuses (body cavity), where it actually baths the
internal organs.
In the system, blood and interstitial fluid are not distinguishable, which is known as hemolymph.
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Circulatory system
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Circulatory system
In mollusk, the heart has three chambers (2 atria, 1 ventricle).
The two atria receive hemolymph from the gills. The single ventricle pumps oxygen-rich hemolymph into blood
vessels that conduct it into the large sinuses (spaces) in
the hemocoel.
After bathing the body cells, the hemolymph passes into vessels that leads back to the gills where oxygen will be
reloaded.
* mollusk=Invertebrate having a soft unsegmented body usually
enclosed in a shell
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A hemocoel is a series of spaces
between the organs of organisms with
open circulatory systems, like most
arthropods and molluscs. A combination of
blood, lymph, and interstitial fluid called
hemolymph circulates through the
hemocoel.
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Circulatory system
Some arthropods have a pigment called hemocyaninthat turns blue when oxygenated.
Arthropods (insects) have a tubular heart.
In grasshoppers for instance, pumping of the tubularheart drives the hemolymph to move and brings the
nutrients directly into the body cells.
When the heart relaxes the hemolymph will go throughtiny openings (ostia) to the heart. The ostia have valves
to prevent backflow.
The rate of hemolymph circulation increase duringmovement of insects to provide more nutrients for cell
fuel.
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Circulatory system
Some invertebrates and vertebrates have a closed circulatory system. In this system, the blood is
confined to the vessels, which keep it distinct from the
interstitial fluid.
Earthworm, an invertebrate has a closed circulatory system. Two main blood vessels extend throughout the
body. They are the dorsal and ventral blood vessels.
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Circulatory system
In the anterior part of the
worm, five pairs of
contractile blood vessels,
which sometimes referred
as hearts connect dorsal
and ventral heart vessels.
Contraction of these
vessels, as well as the
contraction of muscles of
the body wall helps
circulate the blood.
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Vertebrate circulation system
Generally, vertebrates heart have one or two atria (the chamber that receives blood returning to the heart) and
one or two ventricles (the chamber that pump blood out
of the heart)
Animals with higher metabolic rates have more complex circulation system
The vertebrate cardiovascular system became modified in the course of evolution, as the site of gas exchange
shifted from gills to lungs.
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Vertebrate circulation system -fish
In fishes blood flows in a single circuit only.
The fish heart contains one atrium and one ventricle.
Each chamber has an additional structure in a form of chambers:
sinus venosus with the atrium - are collection chambers
ventricle and conus arteriosus - are pumping chambers.
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Vertebrate circulation system-fish
The sinus venosus isthe first chamber to
contract, followed by the
atrium, ventricle, and
conus arteriosus.
This series ofcontraction pumps blood
into a single circuit of
blood vessels.
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Vertebrate circulation system-fish
Blood is oxygenated as it passes through capillaries of the gills.
In gills, fresh oxygen will diffuse in through the countercurrent exchange system. As blood circulates
through the gills, pressure is low, so blood passes slowly
to other organs.
Fish swimming movements facilitate the circulation.
The oxygenated blood that has passed the capillary beds of organs returned to the atrium of the two-
chambered heart of fishes
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Vertebrate circulation system-fish
The obvious limitation is that as blood passed through the capillaries in the gills; the blood loses much pressure
developed by the contraction of the heart, making the
circulation from the gills to the rest of the body quite
sluggish.
This feature limits the rate of oxygen delivery to the rest of the body.
This one-way circuit which only pumps deoxygenated blood is adequate for fishes, but will not be enough for
the more active life styles of vertebrates.
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Vertebrate circulation system-Amphibian
As evolution occurs on the land vertebrates, their heart became partitioned into partly right and left halves.
But although it is partially partitioned, it is enough to direct blood flow through two partially separated circuits.
This causes the amphibian to possess double circulation system.
In this double circulation system, the ventricles pumped blood into a forked artery that leads to pulmocutaneous
and systemic circulation. In this way, oxygenated and
deoxygenated blood is kept separate
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Vertebrate circulation system- Amphibian
The frog has two atria and one ventricle. The right atrium receives deoxygenated
blood from the systemic circulation and
the left atrium receives oxygenated
blood from the lungs.
Oxygenated blood is received by the
left atrium and then enters into the frog's
single ventricle
Because they only have a single ventricle, both atria pump into a single
ventricle.
However, deoxygenated blood is pumped out of the heart before oxygenated blood
is pumped in.
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Vertebrate circulation system- Amphibian
Much of the deoxygenated blood is directed into the pulmonary circulation that delivers it to the lungs and
skin where it is recharged with oxygen.
The systematic circulation delivers oxygenated blood into arteries that conduct to various tissues of the body.
One advantage for amphibian is that inside water they can obtain additional oxygen through diffusion at their
skin.
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Vertebrate circulation system-Reptiles
In reptiles like crocodiles, the walls between the ventricles are separated by a septum that partially
subdivides the ventricle.
Lizards have a muscular septum which partially divides the ventricle.
This prevents mixing of the two bloods.
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Vertebrate circulation system- Reptiles
The left half of the ventricle pumps oxygenated blood
(received from the left atrium)
to the body.
The right half pumps deoxygenated blood (received
from the right atrium) to the
lungs.
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Vertebrate circulation system-
mammals and birds
In all mammals and birds, the septum is
complete.
Complete separation requires blood to pass
into the heart twice each
time it tours the body.
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Variation of Circulatory system
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Heart structure
Human heart is not much bigger than a fist and weighs
less than a pound, yet it is a
remarkable organ that is well
adapted for pumping blood.
It is located in the chest cavity directly under the
breastbone.
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Heart structure
The heart is enclosed by a double sac of serous membrane called the pericardium
A slippery lubricating fluid (serous fluid) is produced by the serous pericardial membranes.
This fluid eliminates friction that happens during
the beating of the heart
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Heart structure
This fibrous layer helps protect the heart and anchors it to the surrounding structures, such as
the diaphragm and the sternum.
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Heart structure
The heart walls are composed of three layers the outer epicardium, the myocardium and the inner most
endocardium
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Heart structure
Each half of the heart has two chambers; an
atrium and a ventricle
The left and the right side of the heart are
divided by a septum.
Between each atrium and a ventricle is an AV
(atrioventricular)
valve.
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Heart structure
On the right side, it is usually referred as
tricuspid valve
wherelse on the left side
is usually referred as the
bicuspid valve (mitral
valve).
Between each ventricle and the artery is a
semilunar valve.
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Heart structure
The valves function is to regulate the direction of blood flow.
They did this by automatically closing after a blood flow and preventing the blood from flowing backward
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Heart structure
The atrium is thin-walled because its function is only to
collect blood returning to the
heart and pump it in a short
distance to the ventricles
The ventricles are thick walled
because it needs to pump
blood to all of the bodys organs.
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Heart circulation- pulmonary system
The pulmonary circuit
- connects the hearts
and the lungs only.
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Heart circulation- pulmonary system The right atrium will receive
deoxygenated blood from
inferior vena cava, which
carries blood from lower
parts of the body, and
superior vena cava, which
carries blood from the upper
parts of the body.
From the right atrium, blood is pumped to the right
ventricle, which exits out
from the heart through two
pulmonary arteries, one
going to each lung.
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Heart circulation
At the lungs, CO2 will diffuse to the alveolus tobe exhaled out of the body.
Oxygen will be loaded to the blood and becarried into the heart by the pulmonary veins.
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Heart circulation
This circuit leads from the hearts right half to the capillary beds in
both lungs and then
to the hearts left half.
Therefore, this cycle is only a short loop one.
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Heart circulation-Systemic system
The systemic circuit
is a longer loop that
starts at the hearts left
half and ends at the
hearts right half.
Oxygenated blood is
pumped in from the
pulmonary veins into
the left atrium and the
left ventricle.
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Heart circulation-systemic system
Blood is then pumped by the left ventricle into
the aorta, the largest
artery. Arteries that
branch off from the
aorta conduct blood to
all regions of the body.
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Heart circulation-systemic system
Oxygenated blood will flow
through the arterioles and
capillary beds in all
regions.
Oxygen will diffuse
out of the blood and
carbon dioxide wastes diffuse
into the blood, and later
carried in the veins to
the hearts left half to enter
the pulmonary circuit.
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Cardiac cycle
In a healthy heart, the atria contract simultaneously.
After the contraction, the atrium relaxes and the ventricles start to contract.
Systole and diastole means heart contraction and heart relaxation respectively.
The term cardiac cycle refers to the events of one complete heartbeat, during which both atria and
ventricles contract and relax.
Since the heart beat at approximately 75 times per minute, the length of the cardiac cycle is normally
0.8 second.
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Cardiac cycle
i. Atrial and ventricular diastole - At this point, the
pressure of the heart is low and blood is flowing
passively into the atria and ventricles. The AV valves
are open and semilunar valves closed.
ii. Atrial systole, ventricular diastole - The atria starts to
contract and forced the remaining blood to the
ventricles. When the ventricular pressure is higher
than arteries, blood rushes out of ventricles
iii. Ventricular systole, atrial diastole- Blood is pushed
out of the system. The ventricles are completely
closed chambers
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When using a stethoscope, you can hear two distinct sounds during cardiac cycle.
The first lup sound is caused by the closing of the artrioventriculur valves.
The second heart sound, dup sound occurs when the semilunar valves are closed.
Cardiac cycle
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Cardiac output (CO)
Cardiac output is the amount of blood pumped out by each ventricle in one minute.
It is the product of the heart rate (HR) and the stroke volume (SV)
Stroke volume is the volume of blood pumped out by each ventricle with each heartbeat.
If we use the normal resting heart rate (75beats/min) and stroke volume (70 ml/beat) the average cardiac
output is about 5 liter/min.
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Cardiac output
i) Regulation of stroke volume
Depends on venous return that effects the stretching of the cardiac muscle cells.
Venous return is the amount of blood entering the heart.
Anything that increases the volume or speed of venous return increases stroke volume and force of contraction.
Exercise speeds venous return caused by the enhanced squeezing action of active skeletal muscle.
Low venous return might result from severe blood loss.
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Cardiac outputii) Regulation of heart rate
Electrical pulses in the heart are controlled by special groups of cells called nodes.
During times of physical and emotional stress, the nerves of the sympathetic division stimulate SA
(sinoatrial) and AV (atrioventricular) nodes to increase
the heart beat.
The SA (sinoatrial) node generates an electrical signal that causes the upper heart chambers (atria) to contract;
the signal then passes through the AV (atrioventricular)
node to the lower heart chambers (ventricles), causing
them to contract, or pump.
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Cardiac output
Parasympathetic nerves slow and steady the heart rate.
Various hormones and ions can also have a dramatic effect on the heart activity
Epinephrine and thyroxine increases heart rate whereas reduced number of ions such as sodium
and potassium decrease the heart rate.
A number of other physical factors such as age, gender, exercise and body temperature also
affects the heart rate.
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Cardiac output
Cardiac muscle need not to be stimulated by nerve impulses before their contraction, they can contract
spontaneously and independently.
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Conduction system of the heart
Two types of controlling systems act to regulate heart activity.
i. The autonomic nervous system The nerves from this system act to slow down or accelerate the heart rate
depending on which division is activated.
ii. Nodal system (Intrinsic conduction system) A specialized tissue that functions as if it is a combination
of muscle and nervous tissue.
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Conduction system of the heart
This conduction system depends on the action made
by the SA (sinoatrial node)
and AV node
(atrioventricular node)
The SA node is located on the right atrium. The SA
node is often called the
pacemaker because it starts
each heartbeat.
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Conduction system the heart
From the SA node, the impulse spreads through the atria
causing it to contract.
And later spread to the AV node.
The AV node is located at the junction of the atria and
ventricles. This branches to the
bundle of His, left and right
bundle branches and Purkinje
fibers which spread within the
muscles of the ventricle walls.
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Conduction system of the heart
At the AV node, the impulse is delayed briefly to give the atria
time to finish contracting. The
impulse then passes to the
bundle of His, the bundle
branches and Purkinje fibers
causing the ventricles to
contract.
This contraction ejects blood superiorly into the large arteries
of the heart.
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Electrocardiogram (ECG)
An electrocardiogram is a recording of the electrical changes that occur in myocardium (the middle
muscular layer of the heart wall) during a cardiac cycle.
Body fluids contain ions that conduct electrical currents, and therefore the electrical changes in myocardium can
be detected at the skins surface.
When an electrocardiogram is being taken, electrodes placed on the skin are connected by wires to an
instrument that detects the myocardium electrical
changes.
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Electrocardiogram (ECG)
When the SA node triggers an impulse, the atrial fibers produce an electrical change that is called the P wave.
The P wave indicates the atria are about to contract.
After that the QRS complex signals that ventricles are about to contract.
The electrical changes that occur as the ventricular muscle fibers recover produce the T wave.
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Blood Vessel
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Blood vessels The vertebrate circulatory system includes three main
types of blood vessels, which are arteries, capillaries
and veins.
An artery carries blood away from the heart chamber toward other tissues.
When an artery enters an organ, it divides into many smaller branches called arterioles.
The arterioles deliver blood into the microscopic capillaries.
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Blood vessels
Materials are only
exchanged between the
blood and the interstitial
fluid bathing the cells
through the capillary
walls, which are only
one cell thick, which is
the endothelium.
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Blood vessel
From the capillaries at capillary beds, the deoxygenated blood flow will combine
through venules and back to veins.
The thick walls of arteries and vein prevent gases and nutrients from passing through.
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Blood vessels
Histologically, blood vessels
consist of concentric
layers or "tunics"
i. The tunica intima is the
inner lining, consisting of
endothelium and a
relatively thin layer of
supporting connective tissue.
- It provides a smooth
surface that minimizes
resistance to the flow of blood.
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Blood vessels
ii. The tunica mediais the middle
muscular and/or
elastic layer,
containing smooth
muscle and elastic
tissue in varying
proportions.
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Blood vessels
iii. The tunica adventitia
is the outer, fibrous
connective tissue
layer.
- This elastic fibers
allow the blood vessel
to stretch and recoil
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Blood vessels
Nervous tissue is
generally inconspicuous
in blood vessels but
serves to regulate
smooth muscle function
and to mediate pain
sensation
The smooth muscle
allows arteries and
some veins to regulate
blood flow by constricting.
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Blood vessels
Capillaries lack two
outer layers present in
veins and arteries.
This allows exchange of
blood between the
blood and interstitial
fluid
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Blood vessels
Arteries have thicker middle and outer vessel
layer as compared to veins to withstand high pressure
and velocity of blood pressure from the heart.
The veins do not have to deal with high pressure and velocity because blood that flows through them are
returning from the long journey to the heart.
They have valves to prevent backflow of blood returning to the heart in low pressure
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Physiology of circulation - Blood flow
velocity
The velocity of blood in the blood vessel follows the law of continuity, which describes the blood flow through a
pipe.
A fluid flows through narrower segments faster than through wider segments
However, total cross sectional area of the blood capillaries slows down the flow of blood in vast numbers
of blood capillaries.
The slow progress of blood flow arterioles capilaries
venules is important as it allows the exchange of substances between blood and interstitial fluid.
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Physiology of circulation Arterialpulse
A good indication of a persons circulatory system can be obtained by taking arterial pulse
and blood pressure measurement
Arterial pulse
The surge of blood entering the arteries that caused the walls to stretch and recoil can be felt
as a pulse in any artery that runs close to the
bodys surface.
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Physiology of
circulation - Pulse We can feel the pulse by placing
several fingers on the radial
artery which lies near the outer
border of the palm side of a
wrist.
A carotid artery is another alternative for feeling the pulse.
It is located on the either side of
the trachea of the neck.
The pulse rate indicates the rate of the heart beat because the
arterial walls pulse whenever the
left ventricle contracts.
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Physiology of circulation Blood pressure
Blood pressure is the pressure of blood against the wall of a blood vessel.
A sphygmomanometer can be used to measure blood pressure, usually in the brachial artery of the
arm.
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Physiology of circulation
The blood pressure cuff is wrapped around the elbow and inflated until the cuff pressure exceeded the systolic
blood pressure.
At this point, blood flow in the arm is stopped and a brachial pulse cannot be heard.
The pressure in the cuff is gradually reduced.
The systolic pressure is recorded as the first tapping sound is heard.
As the pressure is reduced further, the sounds become louder and later disappeared when the artery is no
longer constricted and blood flows freely. The diastolic
pressure is recorded as the sound disappears.
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Blood pressure
When the ventricles contract, they force blood into large, thick walled elastic arteries that
expand as the blood is pushed into them.
Continual blood flow depends on the stretchiness of the arteries.
Because the heart continuously contracts and relaxes, the off-and-on flow of blood into the
arteries causes the heart pressure to rise and
fall during each beat.
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Blood pressure
Thus, two arterial blood pressure measurements are made, systolic (the pressure in the arteries at
the peak of ventricular contraction) and diastolic
pressure (the pressure in the arteries when the
ventricles are relaxing).
Blood pressures are reported in millimeters of mercury (mmHg) with the systolic pressure written
first. For example 120/80.
The high pressure forces the blood to continually move into the arterioles, capillaries, venules and
veins.
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Blood pressure
In the venules and veins, blood pressure is very minimal. Therefore, instead of blood pressure,
venous return depends on:
i. Skeletal muscle contraction
ii. The presence of valves in the veins
iii. Respiratory movements
Blood velocity increases in the venous vessels due to reduction in cross sectional area as small
venules join to form veins.
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Blood pressure
When the skeletal muscles contract, they compress the weak walls of veins. This causes
the blood to move past the next valve.
Once past the valves, blood cannot flow backwards.
During inhalation, the thoracic pressure falls and abdominal pressure rises as the chest expands.
This respiratory movement also allows blood in veins to return back to the heart.
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Blood pressure
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Fluid movements in capillary beds
The fluid movements across a capillary wall result from the two opposing forces blood pressure and osmotic pressure.
At the arteriole end, blood pressure exceeds osmotic pressure, therefore ultrafiltration happens
causing fluid to flow out of the capillaries, bringing
together nutrients and gases
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Fluid movements in capillary beds
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Lymphatic system
Water and solutes undergo ultrafiltration process caused by the pressure of the blood at the
capillary beds to form interstitial fluids.
The interstitial fluid will be returned to the blood by way of an open circulatory system called the
lymphatic system.
The lymphatic system consists of lymphatic capillaries, lymphatic vessels, lymph nodes and
lymphatic organs.
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Lymphatic system
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Lymphatic system
Excess fluid that is that is drained into blind-ended lymph capillaries is called the lymph.
The lymph starts at the capillary beds, where they enter the lymph capillaries and later merges with the lymph
vessels/lymph veins that are equipped with valves to
prevent backflow of fluid toward the capillaries
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Lymphatic system
At strategic locations, lymph veins enter lymph
nodes, which are small, organized mass of lymph
tissue. Lymph nodes have two functions;
i. they filter the lymph as it slowly passes through
ii. they are battlegrounds where lymphocytes
and foreign agents are destroyed during an
infection.
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Lymphatic system
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Lymphatic system
Lymph nodes are most
numerous in the neck
region, under the arms,
in the groin region, in the
chest and abdomen.
In cases of infection,
lymph nodes enlarge
and may be felt as hard
little knots below the skin.
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Lymphatic system
Lymph veins that leave the lymph nodes conduct lymph towards the shoulder region.
The lymphatic veins flow into one of two lymph ducts.
The right lymph duct drains from the right arm, shoulder area, and the right side of the head and neck.
The left lymph duct, or thoracic duct, drains from the legs, gastrointestinal tract and other abdominal organs,
thoracic organs, and the left side of the head and neck
and left arm and shoulder.
These ducts then drain into the subclavian veins on each side.
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Lymphatic system
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Lymphatic system
Consists of three important organs
tonsils, spleen and thymus
i) Tonsils are masses of lymph
tissue under the lining of the
oral cavity and throat. Tonsils
help protect the respiratory
system from infection by
destroying bacteria and other
foreign agents that enter the
body through the mouth and
the nose.
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Lymphatic system
ii. The thymus is where
immature lymphocytes
differentiate into
Tlymphocytes.
iii. The spleen filters the blood and reacts immunologically to
bloodbone antigens. The
spleen functions in both
immune and hematopoietic
systems.
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Mechanism of lymph flow
The lymphatic system preserves fluid balance
by collecting about 10% of the interstitial fluid and
the protein that accumulates in the fluid. The
lymph capillaries have no obvious entrance, water
and solutes moves into clefts between cells
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Mechanism of lymph flow
Lymph capillaries merge into lymph vessels that have a larger diameter. Lymph vessel contain smooth
muscle in their wall.
Therefore, mechanism of backflow depends on:
i. Pressure gradient (hydrostatic pressure)
ii. Muscular and respiratory pumps push lymph
forward. Just like veins, besides having valves,
lymphatic vessels depend mainly on the movement of
skeletal muscles to squeeze the fluid along.
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Mechanism of lymph flow
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Lymphatic system-function
Have three obvious functions
i. Drainage
Collect water and that has leaked out of the blood in
capillary beds due to fluid pressure and returned it to the
bloodstream
ii. Disposal
Foreign cells and materials /cellular debris are brought to
the lymph nodes for disposal
iii. Delivery
Picked up fats that had been absorbed in the small intestine and delivers it into the bloodstream.