The Venous System of Guinea Pig

The Venous System:

The cranial vena cava draining blood from anterior region and the caudal vena cava from the middle and posterior region of the body open respectively into the cranio- caudal and craniodorsal region of the right atrium. Only hepatic portal system is present (Fig. 20.2).

1. Cranial vena cava:

The cranial vena cava is formed by the joining of right and left brachiocephalic veins. A brachiocephalic vein is formed by the joining of external and internal jugulars and subcla­vian.

A. External jugular formed by the union of:

a. Linguofacial from tongue and adjacent region.

b. Facial from facial region.

c. Maxillary from maxillary region.

d. Deep cervical from pectoral muscles.

e. Supra and subscapular from scapular region.

B. Internal jugular formed by the union of:

a. Pharyngeal from pharynx.

b. Oesophageal and trachal from oesophagus and trachea.

The two jugulars unite and open into the brachiocephalic vein of the side.

C. Right subclavian:

Formed by the union of:

a. Brachial from the extremity of the fore limb and continues inward as axillary vein re­ceiving costocervical from the thoracic wall, neck muscles and phrenic from the diaphragm.

b. The axillary continues as subclavian and receives:

i. Vertebral from vertebral column

ii. First intercostal from anterior inter­costal space

iii. Supreme intercostal from first two intercostal spaces

D. Left subclavian:

Formed by veins similar to those of right side:

1. Cranial vena cava:

It is a short and stout vessel, directly re­ceives:

i. Vertebral from vertebral column

ii. Internal thoracic from fifth and sixth intercostal spaces

iii. Azygos from the thoracic wall and diaphragm (phrenic)

2. Caudal vena cava:

It is formed by the union of veins bringing blood from the middle and posterior region of the body.

a. Median sacral from the sacral and coc­cygeal region

b. External iliac by the joining of:

i. Femoral from hind-limb

ii. Pseudo gastric from abdominal muscles and urinogenital organs

iii. Internal iliac from urinary bladder and pelvic region

iv. Common iliac is formed by the join­ing of two iliacs

The caudal vena cava in its forward course receives:

v. Caudal abdominal from the posterior abdomen and rectum and joins the common iliac

vi. Lumbars from lumbar region

vii. Genitals from testis/ovaries

viii. Renals from kidneys receiving adrenals

ix. Caudal phrenic from diaphragm

x. Cranial abdominal from abdomen

xi. Hepatic a single vein from the liver.

The caudal vena cava pierces the dia­phragm following a middle course and forms a shallow arch to the right and opens in the right atrium.

3. Hepatic portal system:

Hepatic portal vein is formed by joining of following veins from the visceral organs.

i. Cystic from gall bladder

ii. Cranial mesenteric from intestine

iii. Caudal mesenteric from rectum

iv. Gastro-duodenal from stomach, pancreas and anterior part of the intestine.

The hepatic portal vein branches in the lobes of the liver.

4. Pulmonary veins:

A single vein from the right and two veins joining to form one from the left lung, join to form a common pulmonary vein opening in the left atrium.