- Open circulatory system
shows blood flow at a very low velocity and low pressure. Direct
exchange of materials between body cells and blood is possible.
- In cockroach, the muscles
responsible for circulation of blood are alary muscles.
- The number
of chambers of heart are different in different vertebrates. For example,
in fish, heart is two chambered with one auricle, one ventricle. The
blood pumped is venous blood, i.e., deoxygenated. The heart is also
called branchial heart or venous heart.
- In amphibians, the heart is
three chambered. In reptiles, the heart is structurally three chambered
and functionally four chambered. There are two auricles and an
incompletely divided ventricle. In crocodiles, and alligators, the heart
is four chambered.
- In birds and mammals, the
heart is with four chambers with two auricles and two ventricles.
- Interauricular septum has an oval
depression called fossa ovalis.
It is a vestigeal structure of foramen ovale present in foetus.
- Opening of inferior vena
cava is guarded by a valve of Eustachius while
opening of coronary sinus is guarded by valve of Thebesius.
- The animals without heart
are Nereis (annelid) and Amphioxus
- Angiology is study of blood vessels.
Angioplasty is removal of blockage of an artery by balloon surgery.
Angiography is radioautograph of blood vessels
after injecting certain tracers.
- Papillary muscles of
ventricles act as anchors in the heart of man.
- Portal system comprises of
portal vein and its branches. Man shows two types of portal systems,
namely, hepatic portal system and hypophyseal
- In amphibians and fishes,
there is another well developed portal system called renal portal system
which is absent in mammals.
- Coronary circulation
involves the blood supply to heart wall. Coronary arteries arise from
aortic arch and supply pure blood to heart wall. Coronary veins collect
the blood from heart wall and open in right auricle.
- ECG or electrocardiogram is
a graphic record of electrical variations produced by the beating of
heart. Einthoven is called father of electrocardiography.
ECG was first recorded by Waller.
- Myogenic heart is the one where
initiation of heart beat is under muscular control. Such a heart when
removed from the body and placed in a saline solution called Ringer's solution, goes on beating for some time. Example: Molluscs and vertebrates.
- Neurogenic heart is the one where
initiation of heart beat is under the control of nervous system. Thus,
it stops beating after it is removed out of the body. Example:
Crustaceans, insects and annelids.
- Blood is with three types of
blood corpuscles namely R.B.C.s, W.B.C.s and blood platelets.
- In mammals, the R.B.C.s are circular, biconcave and without nucleus.
The biconcave shape of R.B.C.s increases the
surface area to volume ratio. Absence of nucleus increases motility of
cells and haemoglobin content of cell. Life
span of human R.B.C.s is about 115 to 120