The Transport System Essay, Research Paper
Describe the action of the heart in terms of collecting blood,
pumping of blood, and opening and closing of valves In mammals, with double circulation,
the heart is divided into right and left sides with 2 atria and 2 ventricles.
This division of the heart prevents the oxygenated blood on the left side from
mixing with the deoxygenated blood on the right side. The muscular heart pumps
the blood into a system of arteries, which branch into arteries. Within the
tissues the arterioles branch into capillaries where exchange of materials
between blood cells takes place. From the capillaries blood is collected up into
a series of venules which join up to form veins which the blood returns to the
heart. Blood returning to the heart from all parts of the body, except the
lungs, enters the right atrium, whence it passes into the right ventricle, and
then via the pulmonary artery to the lungs. The walls of the arteries and veins
are elastic,. and the heart and veins are equipped with valves which prevent
blood flowing in the wrong directions. Blood returning via the venae cavae
enters the right atrium. The resulting pressure in this chamber forces open the
flaps of the tricuspid valve. The result is that blood flows through the
tricuspid opening into the right ventricle. When the atrium ad ventricle is
full of blood, the atrium suddenly contracts, propelling the blood into the
ventricle. The contraction spreads from the right atrium over the rest of the
heart. Atrial systole s relatively weak but the ventricles, whose thick walls
are especially well endowed with muscle, contract more powerfully. As a result,
blood is forced from the right ventricle into the pulmonary artery. Draw a diagram of the heart showing all four chambers, and
associated vessels and valves. Outline the way the heart beats and is regulated in terms of its
myogenic nature, nerve and hormone situation Cardiac muscle (i.e. the heart) is
myogenic: its rhythmical contractions arise from within the muscle tissue
itself. The heart is made to slow up or down, under involuntary control, by
means of nerves and hormones. Myogenic means that cardiac cells are self-excitable:
they can contract without any signal from the nervous system. The sinoatrial
(SA) node/pacemaker is located in the wall of the right atrium. It is composed
of specialised muscle tissue. Each time the SA node contracts, it.initiates a
wave of excitation that travels through the wall of the heart; the two atria
contract in unison. The atrioventricular node is located at the bottom of the
wall separating the 2 atria. When the wave of excitation reaches the AV node,
it is delayed for about 1 second. After this delay, the wave of excitation
spreads upward through the ventricular walls. The pacemaker is controlled by
both nerves and hormones. The hormones are secreted into the blood by the
glands. Explain the relationship between the structure and function of
arteries, capillaries and veins Arteries o
flow away from heart. o
thickest vessels o
thin passage (to maintain pressure o
fast flow
Veins o
towards heart o
thin muscular wall o
slow flow
Capillaries o
No muscle o
permeable State the components of blood o
55% Plasma ?
90% Plasma = Water o
45% Erythrocytes, Leukocytes and Platelets State the substances transported by blood o
Heat o
Nutrients o
O2 o
CO2 o
Hormones o
Antibodies o
Waste Outline the basics of Haemophilia o
Inability of blood to clot o
Results in persistant bleeding o
Allelle sex-linked recessive o
Unable to produce Factor 8