604
UNIT FOUR
After passing through the hepatic sinusoids of the liver,
the blood in the hepatic portal system travels through a
series of merging vessels into
hepatic veins.
These veins
empty into the
inferior vena cava,
returning the blood to the
general circulation.
Other veins empty into the inferior vena cava as it ascends
through the abdomen. They include the
lumbar, gonadal,
renal, suprarenal,
and
phrenic veins.
These vessels drain
regions that arteries with corresponding names supply.
Veins from the Lower Limb and Pelvis
As in the upper limb, veins that drain the blood from the
lower limb can be divided into deep and superF
cial groups
(f g. 15.57)
. The deep veins of the leg, such as the paired
anterior
and
posterior tibial veins,
have names that cor-
respond to the arteries they accompany. At the level of the
knee, these vessels form a single trunk, the
popliteal vein.
This vein continues upward through the thigh as the
femo-
ral vein,
which, in turn, becomes the
external iliac vein.
The superF cial veins of the foot, leg, and thigh connect to
form a complex network beneath the skin. These vessels drain
into two major trunks: the small and great saphenous veins.
3.
Splenic vein
from a convergence of several veins
draining the spleen, the pancreas, and a portion of the
stomach. Its largest tributary, the
inferior mesenteric
vein,
brings blood upward from the descending colon,
sigmoid colon, and rectum.
About 80% of the blood fl
owing to the liver in the hepatic
portal system comes from the capillaries in the stomach and
intestines and is oxygen-poor, but nutrient-rich. As discussed
in chapter 17 (pp. 674–675), the liver handles these nutrients
in a variety of ways. It regulates blood glucose concentration
by polymerizing excess glucose into glycogen for storage or
by breaking down glycogen into glucose when blood glucose
concentration drops below normal.
The liver helps regulate blood concentrations of recently
absorbed amino acids and lipids by modifying them into
forms cells can use, by oxidizing them, or by changing them
into storage forms. The liver also stores certain vitamins and
detoxiF es harmful substances.
Blood in the hepatic portal vein nearly always contains
bacteria that have entered through intestinal capillaries.
Large
Kupffer cells
lining the hepatic sinusoids phagocytize
these microorganisms, removing them from the portal blood
before it leaves the liver.
Liver
Hepatic
portal v.
Gallbladder
Pancreas
Superior
mesenteric v.
Portion of
small intestine
Ascending colon
Stomach
Left gastric v.
Right gastric v.
Spleen
Splenic v.
Inferior
mesenteric v.
Descending colon
Rectum
FIGURE 15.55
Veins that drain the abdominal viscera. (
v.
stands for vein.)
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