The Circulatory System

The Circulatory and
Lymphatic systems
Blood is a fluid that circulates throughout the body.
It carries nutrients from digestive system to body
It carries oxygen taken up by respiratory system
It removes wastes produced by cell metabolism. *
The human body contains approx 5-6L of
Blood consists of:
A fluid component called plasma.
And formed elements :
– Red blood cells
– White blood cells
– Platelets
Function of blood components
Plasma :
–Makes up 55% of whole blood
–Is a yellowish liquid (mainly water)
in which red blood cells, white
blood cells and platelets are in
–Also contains nutrients, antibodies,
hormones and metabolic waste .*
Red blood cells:
– Are concave on both sides and lack a nucleus
– Contain Hemoglobin (red pigment that
carries oxygen)
– Are produced in the bone marrow
– 45% of blood volume
 Oxygenated blood carries oxygen and is
bright red
 Deoxygenated blood depleted of
oxygen, carrying carbon dioxide and is
dark red (not blue).
White blood cells:
– Also called Leucocytes
– Are colourless
– Larger than red blood cells
 White blood cells protect the body by:
– Engulfing and digesting dead or damaged cells, old RBC’s,
and microorganisms
– Produce antibodies to neutralize invading organisms
 are red blood cell fragments
 Important in the clotting of blood
(clotting –the process
where the platelets
clump together and start
the formation of fibrin
filaments to form a solid
mass (a clot) and stop
the bleeding)
Fibrin filaments
Blood groups
 Red blood cells have proteins on their surface,
called antigens that provoke a clotting reaction
when they are introduced into another body.
 Blood is grouped according to the type of antigen it
contains and by the Rhesus factor.
 Blood typing is important for blood transfusions
 A blood transfusion is the injection blood products
(usually red blood cells) from one person to
Blood type A
-has the A antigen (protein)
on its surface
Blood type B
-has the B antigen on its
Blood type AB
-has both A and B antigen
on its surface
Blood type O
-has NO antigen on its
Rhesus (Rh)factor
This Rh factor is another antigen determining
the compatibility for blood transfusions
– Rh+ means the antigen is present
– Rh - means the antigen is not present
can donate to
can receive from
A+, A-, AB+, AB-
A-, O-
A+, AB+
A+, A-, O+, O-
B-, B+, AB-, AB+
B-, O-
B+, AB+
B+, B-, O+, O-
AB-, AB+
AB-, A-, B-, O-
Universal recipient
Universal donor
O+, A+, B+, AB+
O+, O-
The anatomy of the
Circulatory System
The Heart
the heart has 4 chambers:
– Right and left atrium (1st chambers that blood
enters in heart)
– Right and left ventricle (last chamber before blood
leaves heart)
Left atrium
Right atrium
Right ventricle
Left ventricle
(very muscular)
Heart Valve movie
Major blood vessels of the heart
Blood vessels are the plumbing of
body that assure the distribution
blood to the entire body.
 Two vessels leave the ventricles:
 The Pulmonary artery –blood is pumped
to the lungs.
 The Aorta – blood is pumped throughout
the body.
Two vessels enter the atria:
 The Pulmonary veins – bring blood back
from the lungs.
 The Venae Cavae – bring blood back from
the body.
Main blood vessels
(blood to body)
Superior vena cava
(blood from the
upper body)
(blood to the
Inferior vena cava
(blood from the
lower body)
(blood from
the lungs)
Blood Vessels
Arteries carry blood away from the heart to the
organs of the body
have thick, muscular,
walls to withstand high pressure.
The Aorta is the largest artery
in the body.
These large arteries progressively branch and get
smaller and smaller, becoming- arterioles, then
Capillaries are minute branches at the ends of
the arteries and veins.
They are permeable allowing the diffusion of
substances into all body cells which are within
50µm of a capillary.
Veins –go to the heart and have
thinner walls and are less elastic
than the arteries because there
is less pressure.
to help the blood to flow up from the extremities (e.g.
legs), veins have one way valves that prevent
Leg muscle contractions help “pump”
blood back to the heart.
Capillaries turn into venules enlarging into
returning to left atrium via the large Vena Cava.
How it works
When a heart beats it first
contracts the atria and then
the ventricles
Deoxygenated blood returns
under pressure via the Vena
Cava into the relaxed right
Contraction of right atrium
forces blood into the right
Ventricular contraction forces
blood through the Pulmonary
artery into the lungs.
Blood travels through smaller
arteries then arterioles and
finally the capillaries in single file.
The capillaries surround the minute air sacks
(alveoli) and allow the exchange of gases
(O2,CO2) between blood and inhaled air.
Oxygenated blood leaves the
capillaries of the lungs, first
through the venules, then
veins returning to the left
atrium via the pulmonary vein.
Contraction of the left atrium
forces the blood into the left
Contraction of the left ventricle
forces the blood through the Aorta
throughout the body.
Arteries branch off the aorta and supply various organs and
tissues with oxygenated blood. The blood follows this path:
 Arterioles
 Capillaries – exchange of gases
 Venules
 Veins
 Vena cava
Blood pressure
Blood pressure is the force with which the blood
is pushing against the arterial walls.
Bp is measured in mm of mercury (mm Hg)
The systolic pressure is when the ventricular
pressure is at its maximum and the vessels are
The diastolic pressure is when the heart is at
rest ( no contraction).
The pressure is given as a ratio of systolic 120
diastolic 80
(for adolescents normal bp is 113 mm Hg)
The lymphatic system
 Carries dissolved O2 and nutrients to the cells
 Collects cellular waste products
 plays an important role in the immune system
Lymph is:
 A fluid that fills the spaces between the blood
vessels and the body cells
 A fluid derived from the blood
Lymphatic vessels resemble blood vessels and
are close to them
The lymph returns to the circulatory system via
two veins near the heart.
The lymph relies on muscle movement for
The lymphatic system comprises of the following
organs :
 The thymus- found underneath the heart
 The bone marrow- found in long bones
 The spleen- found left of stomach under
 The tonsils- found in mouth bordering the
The lymphatic vessels have lymph nodes
throughout the body.
When an infection occurs these nodes
swell and harden (e.g. A cold or tonsillitis)
The immune system
The ability of the body to protect itself against
antigens is called immunity.
Antigens are viruses, bacteria, abnormal cells
or other substances that produce an immune
An antibody is a substance produced by
certain white blood cells that can neutralize
specific antigens.

similar documents