2. Venous system consists of following parts:
Pulmonary venous system
Systemic venous system
Portal venous system
3. The blood vessels which carry the blood towards the
heart constitute the venous system.
The venous system in frog constitutes the following
main veins:
Pulmonary Veins:
The oxygenated blood from two lungs is returned by
two pulmonary veins, which open dorsally into the
left auricle after uniting with each other.
Caval Veins:
The deoxygenated blood from the rest of the body
comes to the sinus venosus through two precavals
(anterior venae cavae) and one postcaval vein
(posterior vena cavae).
4.
5. (i) Precavals or Anterior Vena
Cavae:
Each precaval or anterior vena cava is
formed by the union of three veins:
(a) External jugular receiving branches from the
tongue (lingual) and floor of the mouth
(mandibular).
6.
7. (b) Innominate receiving branches from
the brain and orbit (internal jugular), and
from shoulder and back of arm
(subscapular).
(c) Subclavian vein receiving branches
from arm (brachial) and from skin and
muscles of the abdomen and also mucous
membrane of mouth and head muscles
(musculo-cutaneous).
8.
9. (ii) Postcaval or Posterior Vena Cava:
The postcaval vein receives blood from the
kidneys by 5 to 6 pairs of renal veins and a pair of
gonadial veins (spermatic in male and ovarian in
female) from gonads.
It arises between the kidneys and runs
forward ventral to the dorsal aorta in the mid-ventral
line.
Before it is communicated with the sinus
venosus it also receives a pair of hepatic veins from
the liver.
10.
11. Renal Portal Vein:
The veins which collect the blood from the
posterior side of the body constitutes renal portal
system.
Two large veins, the femoral and sciatic,
return the blood from each leg.
On entering the body cavity each femoral
vein divides into a ventral pelvic and a dorsal renal
portal vein.
The pelvic meets its fellow from the
opposite side forming the anterior abdominal vein.
12.
13. It receives blood from the bladder and
central abdominal wall and runs forward to enter
into liver. Before entering the liver, it is connected
with the hepatic portal vein.
The renal portal unites with the sciatic and
runs along the outer margin of the kidneys
sending branches to it.
The renal portal vein receives the blood
from the body wall of lumbar region through
dorso-lumbar vein.
14.
15. Hepatic Portal System:
Hepatic portal system collects the blood from
the alimentary canal through many branches
and carries it to the liver where the veins
break up into capillaries and the blood is
collected by hepatic veins to pour into the
postcaval.
16.
17. Portal System of Frog
The portal system is defined as a system
of blood vessels in which veins carrying blood
from different parts of the body is first broken up
into capillaries in another organ like kidney or
liver then blood is collected by another set of
capillaries which unite to form another vein that
carries blood to the heart.
Portal vein is therefore originates from
capillaries and terminates as capillaries.
Thus it is also called double capillaries system.
18. Generally veins collect blood from
different parts of the body and bring it to the
heart.
However, there are some veins which
before reaching the heart take the blood to
some other organs where they form network of
capillaries.
These veins are called portal veins.
The organs which receive blood from portal
veins are called portal organ.
19.
20. It consists of the veins collecting the blood from
alimentary canal and hind limbs and distributing
blood to the liver.
It consists of:
i. Anterior abdominal vein-
It is a median vein and formed by the
union of two pelvic vein and vesicular vein.
Pelvic veins are the lateral branches of
femoral veins from hind limbs which collect
blood from the outer parts of the hind limbs.
21. Vesicular vein collects blood from urinary
bladder.
The anterior abdominal vein runs
forward along the mid-ventral line of the body
wall, towards the liver.
At the anterior most end, it divides
into two branches entering the right and left
lobes of the liver where it breaks up into
capillaries inside it.
It also gives a short branch which joins
the hepatic portal vein before entering the liver.
22. Jugular vein
Any of several veins of the neck that
drain blood from the brain, face, and neck,
returning it to the heart via the superior vena
cava.
The main vessels are the external
jugular vein and the interior jugular vein.
The external jugular vein receives
blood from the neck, the outside of the
cranium, and the deep tissues of the face and
empties into the subclavian veins .
23. Among the tributaries of the external
jugular veins are the posterior external jugular
veins, which receive blood from the back of
the neck, and the anterior external jugular
veins, which receive blood from the larynx (or
voice box) and other tissues below the
lower jaw.
The internal jugular veins unite with
the subclavian veins to form the
brachiocephalic veins and drain blood from
the brain, the face, and the neck.
24. External jugular vein
Travels along the lateral aspect of the neck and
drains the venous blood from the head. Just
caudal to the mandibular angle, it branches into
the linguofacial vein and the maxillary vein.
The mandibular gland is situated between
both branches
25. Internal Jugular Vein
The internal jugular vein is the key
structure in the examination of the deep
cervical chain and it should be kept in the
centre of the field of view whilst
sweeping down the chain with the probe
in the transverse position.
