Veins

Blood reservoirs

At rest, systemic veins contain approximately 60% of the blood volume. This blood can be quickly diverted to other vessels if necessary.

Tissue layers

Compared to arteries, veins have a thinner tunica interna and tunica media and a thicker tunica externa.

Dorsal Venous Arch

Drains: foot Empties into: great saphenous vein; small saphenous vein

Straight Sinus

Drains: the great cerebral vein; inferior sagittal sinus; cerebellar veins Empties: transverse sinus

Superficial Veins

The superficial veins are located just below the skin and are often visible with the unaided eye. They are clinically important as sites for withdrawing blood or giving injections.

Azygos System

The term azygos means unpaired. Most structures of the thorax and the abdominal wall are drained by a network of veins that are situated on each side of the vertebral column called the azygos system. Several small veins directly link the azygos system with the IVC and the SVC. Large veins that drain the lower limbs and abdomen pass blood into the azygos system which ultimately empty into the SVC. Clinically, if the IVC or the hepatic portal vein were to become obstructed, the azygos system can return blood from the lower body to the SVC.

Low resistance conduits

Veins carry deoxygenated blood from the organs to the heart. Because they have relatively large lumens, they offer little resistance to blood flow.

valves

Veins contain one- way valves to prevent the backflow of blood.

Venous sinuses

Venous sinuses are enlarged venous channels with a thin endothelial wall that has no smooth muscle to alter its diameter. Examples are: intracranial vascular sinuses that drain blood from the brain; the coronary sinus of the heart that drains the great, the middle, and anterior cardiac veins.

Venules

Venules are small vessels that drain blood from capillaries and transport it to the veins

suprarenals (adrenals)

drain: adrenal glands (suprarenal glands) empty into: the right into the IVC; the left into the renal or inferior phrenic veins

Internal Jugular Veins

drain: brain; face; neck empty into: right and left brachiocephalic veins

ascending lumbars

drain: common iliacs; lumbar veins; sacral veins empty into: azygos vein (right ascending lumbar); hemiazygos vein (left ascending lumbar)

External Jugular Veins

drain: deep parts of the face; exterior of the cranium; auricular veins empty into: right and left subclavian veins

inferior phrenic

drain: diaphragm empty into: the right into the IVC; the left into the left suprarenal vein

lumbars ( 4 on each side of IVC)

drain: dorsal tributaries from the muscles and skin of the loin; abdominal tributaries from the abdominal wall; vertebral plexus empty into: first and second empty into the ascending lumbar veins; third and fourth empty into the IVC

common iliacs

drain: internal and external iliac veins; iliolumbar and sacral veins; left common iliac drains the middle sacral vein empty into: left and right common iliac veins join to form the inferior vena cava (IVC)

Hepatics

drain: liver empty into: IVC

external iliac

drain: lower extremities; lower abdominal wall; inferior epigastric deep circumflex veins; pubic veins empty into: common iliac veins

gonadals

drain: ovaries and testes empty into: IVC

internal iliac

drain: prostate gland and ductus deferens (in the male); uterus and vagina (in the female); gluteal muscles; medial side of the thigh; urinary bladder; rectum empty into: common iliac veins

sigmoids

drain: sigmoid colon; descending colon empties into: inferior mesenteric vein

posterior intercostal veins

drain: skin and muscles of the back empty into: azygos vein (#5-11); right highest intercostal; hemiazygos (#4)

left and right gastrics

drain: stomach (tributaries from both surfaces of the stomach) empty into: hepatic portal vein

short gastrics

drain: stomach (upper portion and left part of the greater curvature) empty into: splenic vein

renals

drain: the kidneys empty into: IVC

lumbars

drain: the skin and muscles of the loin; abdominal wall; vertebral plexus empty into: first and second lumbar veins empty into the ascending lumbar veins

Inferior Vena Cava (IVC)

drains: abdomen; pelvis; lower extremities empties into: the right atrium

Popliteal

drains: anterior and posterior tibial veins; small saphenous vein empties into: femoral vein (the femoral vein is a continuation of the popliteal vein immediately proximal to the knee)

axillary

drains: cephalic, brachial, and basilica veins empties into: becomes the subclavian vein at the outer border of the first rib

Superior Sagittal Sinus

drains: cerebrospinal fluid (CSF) from the subarachnoid space empties into: the confluence (coming together) of the sinuses near the internal occipital protuberance

subclavian

drains: continuation of the axillary vein starting at the level of the first rib; drains external jugular vein empties into: joins the internal jugular vein to form the brachiocephalic vein

Femoral

drains: deep structures of the thigh empties into: external iliac vein at the level of the inguinal ligament

left colic

drains: descending colon empties into: inferior mesenteric vein

radial

drains: dorsal metacarpal veins of the hand empties into: joins the ulnar vein in the antecubital fossa to form the brachial vein

Basillic

drains: dorsal venous arch of the lateral aspect of the hand; median cubital vein empties into: joins the brachial vein to form the axillary vein

cephalic

drains: dorsal venous arch of the medial aspect of the hand; accessory cephalic vein empties into: axillary vein immediately caudal to the clavicle

External iliac

drains: femoral vein; great saphenous vein (the external iliac vein is a continuation of the femoral vein) empties into: common iliac vein

Plantar Venuous Arch

drains: foot empties into: medial and lateral plantar veins

Anterior Tibial

drains: foot; muscles and bones of the anterior leg empties into: popliteal vein (the anterior tibial vein is a continuation of the dorsalis pedis vein)

Small Saphenous

drains: foot; posterior portion of the leg empties into: femoral vein (joins the popliteal vein behind the knee)

Great Saphenous

drains: foot; superficial tissues of the lower extremities; deep veins empties into: femoral vein (joins the femoral vein in the groin)

Accessory Hemiazygos

drains: fourth through eighth left posterior intercostals veins and maybe the left bronchial veins empties into: azygos vein or hemiazygos vein

cystic

drains: gallbladder empties into: hepatic portal vein

Internal Iliac

drains: gluteal muscles; medial side of the thigh; urinary bladder; rectum; prostate gland; ductus deferens; uterus; vagina empties into: common iliac vein (the internal iliac vein joins the external iliac vein to form the common iliac vein)

Superior Vena Cava (SVC)

drains: head; neck; chest; upper limb (right and left brachiocephalic veins); azygos vein empties into: superior cranial region of the right atrium

Hemiazygos (enters thorax through the aortic hiatus of the diaphragm)

drains: left ascending lumbar vein; caudal four or five intercostals veins; left subcostal vein; esophageal and mediastinal veins empties into: azygos vein

left superior intercostals

drains: left second, third, and fourth posterior intercostals veins empties into: left brachiocephalic vein and maybe the accessory hemiazygos vein

Median Cubital

drains: median antebrachial vein empties into: joins the basilic vein anterior to the elbow

ulnar

drains: palmar venous arch empties into: joins the radial vein in the antecubital fossa to form the brachial vein

Median antebrachial

drains: palmer venous arch of the hand empties into: median cubital vein

brachial

drains: radial and ulnar veins empties into: joins the basilica vein to form the axillary vein at the level of the teres major muscle

superior rectal

drains: rectum empties into: inferior mesenteric vein

inferior mesenteric

drains: rectum empties into: splenic vein

Brachiocephalic

drains: subclavian and internal jugular veins; left brachiocephalic drains the accessory hemiazygos vein empties into: superior vena cava

Hepatic portal

drains: superior mesenteric; splenic; gastric; pyloric; cystic; paraumbilical veins empties into: liver (it divides into right and left branches before emptying into the liver)

Transverse Sinus

drains: superior sagittal sinus (right sagittal sinus); straight sinus (left transverse sinus) empty into: sigmoid sinuses

right highest or superior intercostals

drains: upper two or three intercostals spaces empties into: azygos vein

Deep veins

usually travel alongside arteries of the same name and are located deep in the body