The jugular veins are vein

Vein

In the circulatory system, veins are blood vessels that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart...

s that bring deoxygenated blood from the head

Head

In anatomy, the head of an animal is the rostral part that usually comprises the brain, eyes, ears, nose and mouth . Some very simple animals may not have a head, but many bilaterally symmetric forms do....

 back to the heart via the superior vena cava

Superior vena cava

The superior vena cava is truly superior, a large diameter, yet short, vein that carries deoxygenated blood from the upper half of the body to the heart's right atrium...

.

Internal and external

There are two sets of jugular veins: external and internal.

• The internal jugular vein
  Internal jugular vein
  The two internal jugular veins collect the blood from the brain, the superficial parts of the face, and the neck.-Path:On both sides and at the base of the brain, the inferior petrosal sinus and the sigmoid sinus join to form the internal jugular vein...
  
   is formed by the anastomosis
  Anastomosis
  An anastomosis is the reconnection of two streams that previously branched out, such as blood vessels or leaf veins. The term is used in medicine, biology, mycology and geology....
  
   of blood from the sigmoid sinus
  Sigmoid sinus
  The sigmoid sinuses , within the human head, are two areas beneath the brain which allow blood to drain inferiorly from the posterior center of the head. They drain from the transverse sinuses and converge with the inferior petrosal sinuses to form the internal jugular vein...
  
   of the dura mater
  Dura mater
  The dura mater , or dura, is the outermost of the three layers of the meninges surrounding the brain and spinal cord. It is derived from Mesoderm. The other two meningeal layers are the pia mater and the arachnoid mater. The dura surrounds the brain and the spinal cord and is responsible for...
  
   and the common facial vein
  Common facial vein
  The anterior facial vein usually unites with the posterior facial vein to form the common facial vein, which crosses the external carotid artery and enters the internal jugular vein at a variable point below the hyoid bone....
  
  . The internal jugular runs with the common carotid artery
  Common carotid artery
  In human anatomy, the common carotid artery is an artery that supplies the head and neck with oxygenated blood; it divides in the neck to form the external and internal carotid arteries. - Structure :...
  
   and vagus nerve
  Vagus nerve
  The vagus nerve , also called pneumogastric nerve or cranial nerve X, is the tenth of twelve paired cranial nerves...
  
   inside the carotid sheath
  Carotid sheath
  The carotid sheath is an anatomical term for the fibrous connective tissue that surrounds the vascular compartment of the neck. It is part of the deep cervical fascia of the neck, below the superficial cervical fascia meaning the subcutaneous adipose tissue immediately beneath the skin.The deep...
  
  . It provides venous drainage for the contents of the skull
  Human skull
  The human skull is a bony structure, skeleton, that is in the human head and which supports the structures of the face and forms a cavity for the brain.In humans, the adult skull is normally made up of 22 bones...
  
  .

• The external jugular runs superficially to sternocleidomastoid.

The left and right external jugular veins drain into the subclavian veins. The internal jugular veins join with the subclavian veins more medially to form the brachiocephalic vein

Brachiocephalic vein

The left and right brachiocephalic veins in the upper chest are formed by the union of each corresponding internal jugular vein and subclavian vein...

s. Finally, the left and right brachiocephalic veins join to form the superior vena cava

Superior vena cava

The superior vena cava is truly superior, a large diameter, yet short, vein that carries deoxygenated blood from the upper half of the body to the heart's right atrium...

, which delivers deoxygenated blood to the right atrium of the heart.

There is also another minor jugular vein, the anterior jugular vein

Anterior jugular vein

The anterior jugular vein begins near the hyoid bone by the confluence of several superficial veins from the submaxillary region.It descends between the median line and the anterior border of the Sternocleidomastoideus, and, at the lower part of the neck, passes beneath that muscle to open into the...

, draining the submaxillary region.

Pressure

The jugular venous pressure (JVP) is an indirectly observed pressure over the venous system

Vein

In the circulatory system, veins are blood vessels that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart...

. It can be useful in the differentiation of different forms of heart

Heart disease

Heart disease, cardiac disease or cardiopathy is an umbrella term for a variety of diseases affecting the heart. , it is the leading cause of death in the United States, England, Canada and Wales, accounting for 25.4% of the total deaths in the United States.-Types:-Coronary heart disease:Coronary...

 and lung disease.

Three upward deflections and two downward deflections have been described. The upward deflections correspond with (1) atrial contraction, (2) ventricular contraction (and resulting bulging of tricuspid into the right atrium during isovolumic systole), and (3) atrial venous filling. The downward deflections correspond with (1) the atrium relaxing (and the tricuspid valve moving downward) and (2) the filling of ventricle after the tricuspid opens.