Download Circulatory system

Circulatory system
Premedical 26
The circulatory system carries blood and
dissolved substances to and from different
places in the body.
The heart has the job of pumping these things
around the body.
The heart pumps blood and substances around
the body in tubes called blood vessels.
How does this system work?
pulmonary vein
lungs
pulmonary artery
head & arms
aorta
main vein
Right
Left
liver
digestive system
kidneys
legs
double circulatory system
lymphatic system
Lungs
the right side of the
the left side of the
system
system
deals with
deals with
deoxygenated
oxygenated
blood.
blood.
Body cells
The Heart
This is a vein. It brings
blood from the body,
except the lungs.
These are arteries.
They carry blood away
from the heart.
2 atria
2 ventricles
The heart has four chambers
Coronary arteries,
the hearts own
blood supply
Thoracic cavity
between the lungs and is contained in the
pericardial sac
• Epicardium – outer layer of heart wall
• Endocardium – inner layer that consists of
endothelial cells, which line the heart, covers the
heart valves, and lines the blood vessels.
• Myocardium – middle layer composed of cardiac
muscle.
The Heart
vein to lungs
vein from head and body
right atrium
valve
right ventricle
artery to head and body
Artery from lungs
left atrium
valve
left ventricle
The AV valve on the right side of the heart is called the
tricuspid valve because it has three leaflets (cusps).
The AV valve on the left side of the heart is called the
bicuspid
valve (or mitral valve) because it has two
leaflets.
the pulmonary valve
the aortic valve
How does the heart work?
STEP ONE
blood from the
body
blood from
the lungs
The heart beat begins when the
heart muscles relax and blood
flows into the atria.
How does the heart work?
STEP TWO
The atria then contract and
the valves open to allow blood
into the ventricles.
How does the heart work?
STEP THREE
The valves close to stop blood
flowing backwards.
The ventricles contract forcing
the blood to leave the heart.
At the same time, the atria are
relaxing and once again filling with
blood.
The cycle then repeats itself.
Blood pressure
is a force exerted by circulating blood on the walls of blood
vessels.
During each heartbeat, BP varies between a maximum
(systolic) and a minimum (diastolic) pressure.
Systole is a phase where the myocardium is contracting in a
coordinated manner in response to an endogenous electrical
stimulus
Diastole is the period of time when the heart fills with blood
after systole.
Classification of blood pressure for adults
Category
systolic, mmHg
diastolic, mmHg
Hypotension
< 90
< 60
Normal
90 – 120
and 60 – 80
Prehypertension
121 – 139
or 81 – 89
Stage 1 Hypertension
140 – 159
or 90 – 99
Stage 2 Hypertension
≥ 160
or ≥ 100
There are 3 types of blood vessels
a.
ARTERY
b.
VEIN
c.
CAPILLARY
The ARTERY
the elastic fibres allow
the artery to stretch
under pressure
thick muscle and
elastic fibres
the thick muscle can
contract to push the
blood along.
The VEIN
veins have valves
which act to stop the
blood from going in the
wrong direction.
thin muscle and
elastic fibres
body muscles surround the veins
so that when they contract to move
the body, they also squeeze the
veins and push the blood along the
vessel.
The CAPILLARY
they exchange materials
between the blood and
other body cells.
the wall of a capillary
is only one cell thick
The exchange of materials
between the blood and the
body can only occur through
capillaries.
The CAPILLARY
A collection of capillaries is known as a capillary bed.
artery
vein
capillaries
body cell
The semi-permeable membrane
of capillary walls allows
nutrients, oxygen, and water
to diffuse from the blood to the tissues.
Waste products, like
carbon dioxide, diffuse from the tissues
into the blood.
• Veins have valves
prevent the blood from reversing flow
the return flow of blood to the heart when blood
pressure is low
• the aorta, the largest artery in the body
• blood from the stomach, pancreas, small
intestine, and spleen goes through the liver for
filtration
This portion of the systemic system is known as the
hepatic portal system.
The gastric vein (stomach), splenic vein (spleen),
pancreatic vein (pancreas), and mesenteric veins
(small intestines) empty into the portal vein that
carries the blood to the liver.
the hepatic vein
carries blood to the inferior (caudal) vena cava
The lymphatic
system
is part of the immune system and acts as a
secondary (accessory) circulatory
system.
• remove excess fluids from body tissues,
• absorb fatty acid and transport fat to circulatory
system, and
• produce immune cells (lymphocytes, monocytes,
and plasma cells).
Flow of Blood & Lymph Within Tissue
As the collecting lymph vessel accumulates lymph from
more and more lymph capillaries in its course, it becomes
larger and is called the
afferent lymph vessel
as
it enters a lymph node. Here the lymph percolates through
the lymph node tissue and is removed by the
efferent
lymph vessel. An efferent lymph vessel may directly
drain into one of the (right or thoracic) lymph ducts
Both
the lymph ducts
return the lymph to
the blood stream
by emptying into
the subclavian
veins
lymphoid tissue:
spleen, thymus,
bone marrow and the
lymphoid tissue
associated with the
digestive system.
Lymph nodes filter
foreign substances, such
as bacteria and cancer
cells, before it is reentered into the blood
system through the larger
veins.
Lymph nodes act as the
body’s first defense
against infection.
lymph node
has a fibrous outer covering (capsule), a cortex, and a medulla
Photo from U. S. Federal Government courtesy of Wikipedia.
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