Blood Vessels of the Systemic Circulation: Veins

Dr. Sam Nang

INTERNATIONAL UNIVERSITY

Blood Vessels of the Systemic Circulation: Veins

The superior vena cava returns blood from the head, neck, thorax, and upper limbs to the right atrium of the heart, and the inferior vena cava returns blood from the abdomen, pelvis, and lower limbs to the right atrium.

The veins draining the brain open into the dural venous sinuses. These are the superior sagittal, inferior sagittal, straight, transverse, sigmoid, cavernous, sphenoparietal, petrosal and occipital sinuses. Ultimately, the blood from all these sinuses reaches the sigmoid sinus which becomes continuous with the internal jugular vein. The intracranial venous sinuses communicate with vein outside the skull through emissary veins.

VENOUS SINUSES AND DRAINAGE OF HEAD AND FACE

VENOUS SINUSES AND DRAINAGE OF HEAD AND FACE

I. Diploic veins: endothelial-lined channels between inner and outer tables of the flat bones of skull. Communicate with menigeal veins and dural sinuses internally, veins of the scalp externally. Found in frontal, anterior, and posterior Temporal and occipital regions. Have no valves.

II.Emissary veins: direct connections between dural sinuses and veins on outside of bone. Some major ones pass through foramen ovale, mastoid and parietal foramina, hypoglossal and condyloid canals

III.Dural sinuses: between endosteal and meningeal dura

A.SUPERIOR SAGITTAL sinus: in convexity of falx cerebri from foramen cecum to internal occipital protuberance, where it deviates to right transverse sinus.

Receives superior cerebral veins, venous lacunae, arachnoid granulations, diploic and dural veins, and parietal emissary veins

B. INFERIOR SAGITTAL sinus : in free edge of falx cerebri. Ends in straight sinus.

Receives veins from falx cerebri and medial side of hemispheres

C. STRAIGHT sinus : along line of attachment of falx cerebri to tentorium cerebelli. Terminates in left transverse sinus. Receives inferior sagittal sinus, great cerebral vein (of Galen), left transverse sinus, and superior cerebellar veins

D. TRANSVERSE sinus : one on each side; begin at internal occipital protuberance; pass laterally in attached margin of tentorium to petrous bone, then bend caudally and medially as the sigmoid sinus to enter jugular foramina

Receive superior sagittal, straight, and superior petrosal sinuses, mastoid and condyloid emissary veins, inferior cerebral and cerebellar veins, and diploic veins

E.OCCIPITAL sinus : in attached margin of falx cerebelli; begins at foramen magnum; ends at confluence of sinuses

F. CONFLUENCE OF SINUSES: at internal occipital protuberance where superior sagittal, straight, occipital, and transverse sinuses meet

G. CAVERNOUS sinus: lie on each side of body of sphenoid bone

Receive superior ophthalmic and cerebral veins Communicate with transverse sinus vi superior petrosal sinus, and interal jugular vein via inferior petrosal sinus.

With the internal carotid venous plexus and pterygoid venous plexus through foramina of vesalii, ovale, and lacerum. And with the angular vein, through superior ophthalmic vein

H. INTERCAVERNOUS sinus : anterior and posterior, connecting cavernous sinuses, rostral and dorsal, to pituitary

I. SUPERIOR PETROSAL sinus : along superior border of petrous bone in attached margin of tentorium; join cavernous and transverse sinuses

Receive cavernous sinus; cerebellar, inferior cerebral, and tympanic veins

J. INFERIOR PETROSAL sinus : along suture between basilar portion of occipital and petrous temporal bones; join cavernous sinus and interal jugular vein

Receive cavernous sinus, interal auditiory vein, inferior cerebellar veins, and veins from medulla

K. BASILAR PLEXUS: network on basilar portion of occipital bone; interconnects inferior petrosal sinuses

Communicates with anterior vertebral plexus

Veins of the Head and Neck

The two pairs of major veins that drain blood from the head and neck are the external and internal jugular veins. The external jugular Veins are the more superficial of the two sets, and they drain blood from the posterior head and neck. The external jugular veins empty primarily into the subclavian veins.

The internal jugular veins are much larger and deeper. They drain blood from the brain and the anterior head, face, and neck. The internal jugular veins join the subclavian veins on each side of the body to form the brachiocephalic veins. The brachiocephalic Veins join to form the superior vena cava.

Veins of the Upper Limbs

The veins of the upper limbs can be divided into deep and superficial groups. The deep veins, which drain the deep structures of the upper limbs, follow the same course as the arteries and are named for the arteries they accompany. The only noteworthy deep veins are the brachial veins, which accompany the brachial artery and empty into the axillary vein.

The superficial veins drain the superficial structures of the upper limbs and then empty into the deep veins. The cephalic vein, which empties into the axillary vein and the basilic vein, which becomes the axillary vein, are the major superficial veins. Many of their tributaries in the forearm and hand can be seen through the skin.

The median cubital vein usually connects the cephalic vein or its tributaries with the basilic vein. Although this vein varies in size among people, it is usually quite prominent on the anterior surface of the upper limb at the level of the elbow; an area called the cubital fossa, and is often used as a site for drawing blood.

Veins of the Thorax

Three major veins return blood from the thorax to the supenor vena cava: the right and left brachiocephalic veins and the azygos vein. Blood drains from the anterior thoracic wall by way of the anterior intercostal veins. These veins empty into the internal thoracic Veins, which empty into the brachiocephalic veins.

Blood from the posterior thoracic wall is colleted by posterior intercostal Veins, which drain into the azygos vein on the right and the hemiazygos vein or accessory hemiazygos vein on the left. The hemiazygos and accessory hemiazygos veins empty into the azygos vein, which drains into the superior vena cava.

Veins of the Abdomen and Pelvis

Blood from the posterior abdominal wall drains into the azygos vein. Blood from the rest of the abdomen and from the pelvis and lower limbs returns to the heart through the inferior vena cava.

The gonads (testes or ovaries), kidneys, adrenal glands, and liver are the only abdominal organs outside the pelvis from which blood drains directly into the inferior vena cava. The internal iliac veins drain the pelvis and join the external iliac veins from the lower limbs to form the common iliac veins. The common iliac veins combine to form the inferior vena cava.

Blood from the capillaries within most of the abdominal viscera, such as the stomach, intestines, pancreas, and spleen drains through a specialized system of blood vessels to the liver. The liver is a major processing center for substances absorbed by the intestinal tract. A portal system is a vascular system that begins and ends with capillary beds and has no pumping mechanism such as the heart between them.

The hepatic portal system begins with capillaries in the viscera and ends with capillaries in the liver. The major tributaries of the hepatic portal system are the splenic vein and the superior mesenteric vein. The inferior mesenteric vein empties into the splenic vein. The splenic vein carries blood from the spleen and pancreas. The superior and inferior mesenteric veins carry blood from the intestines.

Blood from the liver flows into hepatic veins, which join the inferior vena cava. Blood entering the liver through the hepatic portal vein is rich with nutrients collected from the intestines, but it may also contain a number of toxic substances harmful to the tissues of the body.

Within the liver, nutrients are taken up and stored or modified so they can be used by other cells of the body. Toxic substances are converted to nontoxic substances and are removed from the blood or are carried by the blood to the kidneys.

Veins of the Lower Limbs

The veins of the lower limbs, like those of the upper limbs, consist of deep and superficial groups. The deep veins follow the same path as the arteries and are named for the arteries they accompany. The superficial veins consist of the great and small saphenous veins.

The great saphenous vein originates over the dorsal and medial side of the foot and ascends along the medial side of the leg and thigh to empty into the fermoral vein. The small saphenous vein begins over the lateral side of the foot and empties into the popliteal vein which, in turn, empties into the fermoral vein. The femoral vein empties into the external iliac vein.

THE END