Literature to prepare the topic9

General angiology

Arteries of the head and neck 

Arterial anastomoses in the head and neck

Abdominal aorta and internal iliac artery

Fetal circulation and shunts

The system of superior vena cava

Anastomoses between the portal and caval venous systems

General angiology

The vascular system is intended for the circulation of blood and lymph. The circulation happens due to the heart work 

The vascular system includes the arterial vessels, the vessels of hemomicrocirculatory bloodstream and venous vessels. The arterial vessels carry the blood from the heart; in the hemomicrocirculatory vessels the exchange of substances with interstitial fluid occurs; most volume of the blood drains into the venous vessels (some part of the blood drains into the lymphatic vessles and thence into the venous system) and thereafter into the heart.

The hemomicrocirculatory, lymphocirculatory bloodstreams and interstitial space filled with interstitial fluid form the microcirculatory bloodstream where the metabolic processes proceed (see video https://youtu.be/j58FXmnDEAE until 4min11sec).
The distribution of the systemic arteries is like a branching tree

 The main arterial vessel is the aorta; from it the primary, then secondary, tertiary and further branches arise.

 

There are extra- and intraorganic arteries relatively to the organ. The extraorganic arteries branch 3-5 times; the intraorganic ones divide 5-8 times. Totally on the way from the heart to an organ there are 8, 10 and more branchings. The arterial diameter diminishes with branching. The arterial wall gradually becomes thinner and simpler in structure.

It should be noted that mostly there are no terminal arteries. The extra- and intraorganic arteries make numerous anastomoses forming the arterio-arterial loops (see the picture showing the angiography of the leg and foot).

The anastomoting arteries usually have an equal diameter. In the case of restricted blood flow through an artery, an anastomosis channel may become enlarged, providing a collateral circulation. This often develops rapidly. If the increased flow and pressure in the collateral channel are maintained, vessels enlarge and finally provide a new arterial route. But sudden occlusion may cause the death of the region supplied.
In some regions (kidneys, spleen) the arteries have no anastomoses and are hence end-arteries. If an end-artery occluded, necrosis occurs in the tissues supplied by it.

An organ can be supplied by the branches of one arterial system or several. Therefore, two categories of the anastomoses are recognized: intersystem and intrasystem. The intersystem anastomosis is a connection of the arteries deriving from the different large (magistral) arterial trunks. Such trunks are the aorta, subclavian arteries, external and internal carotid arteries, external and internal iliac arteries. The picture 1 shows the example of the intersystem anastomosis. The intrasystem anastomosis is a connection of the arteries originating from the same large arterial trunk (the picture 2).


Most commonly the extraorganic arteries run to the organ using the shortest way. They pass together with the nerves, more often via the neurovascular bundles (picture 3). In the trunk and limbs the arterial trunks are placed on the flexor surface.


The architectonics of the intraorganic arteries depends on the type of the organ (hollow, parenchymatous, brain, spinal cord, muscles etc). In general, the distribution of the arteries corresponds to the position of the structural and functional units of an organ.
The arterial architectonics is of great importance in the surgical practice. The arterial distribution, the presence of avascular zones, the degree of the development of the anastomoses are taken into consideration during resections and transplantations.

Here you can see the sructure of the arterial wall:

https://youtu.be/rNDKCfSZtOg https://youtu.be/3Q5x0znIFnI
There are the arteries of the elastic, muscular and mixed types depending on the predomination of the elastic or muscle tissue in the middle layer of thearterial wall.
The elastic arteries are the aorta, pulmonary arteries, brachiocephalic trunk, common carotid arteries, subclavian arteries and common iliac arteries. The elastic tissue provides the continuity of the blood flow from the heart. The father from the heart, the less quantity of the elastic fibres is in thearterial wall. Thus, further branches of the magistral arteries are of the muscular type. They are resistive vessels (the vessels, resistant to high pressure).
The mixed arteries are the external and internal carotids, axillary artery, external and internal iliac arteries, coeliac trunk, superior and inferior mesenteric arteries, renal and coronary arteries.
The thickness of the elastic arteries`s wall ranges from 10 to 15,5% of the artery`s lumen; of the muscular arteries`s wall — 15,5 to 20% of its lumen.

From the smallest in diameter intraorganic arteries the blood passes into the vessels of hemocirculatory bloodstream (capillary bed) (see the video https://youtu.be/Q530H1WxtOw untill 2 min).

It consists of arterioles, precapillary arterioles, capillaries, postcapillary venules and venules.
The diameter ranges from 15 to 30 mcm. The arterioles anastomosing with each other close the arterio-arterial loops which give off along their course 2-6 precapillary arterioles.
The precapillary arterioles have myocytes at the commencement; they play the role of sphincters which regulate the passage of the blood into the capillary bed (see the video https://youtu.be/yeX0uDpPBj4).
The structure of the capillaries you may see here https://youtu.be/hSkIG4MdKqU.
The capillaries in the lungs, brain, spinal cord, skeletal and smooth muscles are narrow but long. The glandular organs have wide capillaries. The widest capillaries are in the liver, spleen, red bone marrow; they are called the sinusoids). Some tissues are devoid of the capillaries: the epithelium of the skin and mucous membranes, cornea, dentine, enamel, endocardium and vascular intima). They are fed by the underlying structures or surrounding fluids.

Arteries of the head and neck

The arteries that supply the head, neck, cranial and orbital content arise from the aortic arch (see the video about the parts of the aorta and the aortic arch branching https://youtu.be/7IZ30V75a34).  Their ends, branches, zones of the blood supply can be found in all Anatomy textbooks. But when you read don`t be surprised, the different books give this information with variations because the branching of the arteries is highly variable. 
Here we focus on the topography and anastomoses of the noted arteries.

But before this we should talk about some general aspects. What should we know about the arteries in general? 1) the origin (from which magistral artery does a studied artery arise); 2) the end (how does the artery end, which terminal branches does it break into); 3) course (topography): the parts, the relations to the surrounding organs etc; 4) the branches originating from the artery; 5) the zones of the blood supply; 6) the anastomoses (inter- and intrasystem).


At first is about the course of the common carotids. The picture 1 shows the order of the aortic arch`s ramification and the length of the described arteries.

Now is about the relations of the common carotid arteries. The picture 2 shows them on the example of the right common carotid artery. The common carotids pass through the carotid triangle (picture 3) bounded by the sternocleidomastoid, posterior belly of the digastric and superior belly of the omohyoid. We can find the triangle on our necks (picture 4) and feel the puls of the arteries.

The knowledge of the topography of the common carotid artery is important to the stop bleeding.

Level with the thyroid cartilage`s upper edge the common carotid arterybifurcates into the internal and external carotids. At the division it has a dilatation, the carotid sinus (the picture 5). The tunica adventitia here is thickened and contains many receptor endings of the glossopharyngeal nerve. The sinus is a baroreceptor; it is responsive to changes in arterial blood pressure, leading to reflex haemodynamic modification. The carotid body, behind the common carotid bifurcation, a small reddish-brown structure, is a chemoreceptor. It responds to a stimulus, primarily O2 partial pressure, which is detected by the glomus cells, and triggers an action potential through the afferent fibers of the glossopharyngeal nerve, which relays the information to the central nervous system.
The internal carotid artery lies lateral to the external carotid but mainly supplies the cranial and orbital content (brain, eye and accessory organs), also forehead and nose hence, the name. In the neck we see the first portion of the internal carotid artery, called the cervical part; thereafter it enters the carotid canal piercing the temporal bone`s petrous part; then passes through the cavernous sinus and finally adjoins the brain, breaking into the terminal branches. Thus, the internal carotid artery has four parts: 1) cervical; 2) petrous; 3) cavernous; 4) cerebral (picture 6). But there is one more artery ascending through the neck and also supplying the brain (posteriorly); this is the vertebral artery which arises from the subclavian artery (therefore, belongs to the subclavian arterial system) (picture 7).

The vertebral artery ascends through a canal formed by the transverse foramina of the VI-I cervical vertebrae (here it can be compressed by the osseous overgrowths (see the vertebral artery syndrome)), enters the skull via the foramen magnum and joins with its fellow near the lower pontine border to form the basilar artery. The branches of the basilar artery (situated posteriorly) meet the branches of the internal carotid artery (situated anteriorly) to make a large central anastomosis called the circulus arteriosus (of Willis) (picture 8, 9, 10). The circle is in the cisterna interpeduncularis, surrounding the optic chiasma, the infundibular stem of the hypophysis cerebri and other related structures in the interpeduncular fossa. Anteriorly the anterior cerebral arteries (from the carotids) are joined by the anterior communicating artery; posteriorly the basilar artery divides onto the posterior cerebral arteries, each joined to the ipsilateral internal carotid by a posterior communicating artery.
Thus, the brain is supplied anteriorly from the carotid arterial system (internal carotid artery), posteriorly from the subclavian arterial system (vertebrobasilar arteries). In the center of the cerebral base these two systems anastomose in the Willis`s circle; its function is to provide adequate blood supply to the brain in the case of blood supply disorder in some of the noted magistral artery.
Vessels of this circle vary in caliber, being often maldeveloped, sometimes even absent. About 60% of circles display anomalies (according to Gray`s anatomy). A detailed analysis of this problem you may see in the article here: http://www.ijsrp.org/research-paper-0315/ijsrp-p3910.pdf

   

The vertebral artery (VA) passes in the canal formed by the transverse foramina of the cervical vertebrae where it can be compressed that causes the vertebral artery syndrome. This syndrome is often observed and manifests in various symptoms.
To make a correct diagnosis, to choose a correct treatment, it is necessary to know the vertebral artery relations in details. This will help us to understand why the certain symptoms occur and to find an exact source of pain in a patient. Besides, we should imagine very well what regions are supplied by the VA.
Now, the VA has four parts: 1) from the commencement to the entering the canal (prevertebral part); 2 ) in the canal; usually the VA enters the canal through the VI transverse foramen but occasionally through V or VI and very rare through III or IV (vertebral part); 3) from the exit the canal to the entering the skull (suboccipital part); 4) from the place where it pierces the atlanto-occipital membrane to the joining with its fellow (intracranial part) (see the picture 11).

The prevertebral part is in the triangle with the following borders: medially the longus colli; laterally the anterior scalenus; inferiorly the pleural cupula (see the picture 12; the triangle is marked with blue lines). This segment of the VA can be compresses by the noted muscles (see the vertebral artery syndrome).
The vertebral part ascends through the canal, being close to the vertebralbodies, together with a sympathetic vertebral nerve arising from the stellate ganglion of the sympathetic trunk; also this part is accompanied by a thick plexus of veins which form the vertebral vein low in the neck. Behind thevertebral part are the ventral rami of the cervical spinal nerves. Medial to it are the intertransverse muscles and also musculi scaleni and longi. This segment of the VA can be compressed by osseous or ligamental overgrowths (osteochondrosis, arthrosis or ligamentosis), or by thevertebral body (in case of vertebral subluxation) (see the vertebral artery syndrome).
The suboccipital part passes at first between the rectus capitis lateralis and the atlantal lateral mass and then between the posterior atlanto-occipital membrane and atlantal posterior arch; the suboccipital muscles are behind (see picture 13). This segment of the VA can be compressed between the muscles and atlas or between the membrane and atlas (see the vertebral artery syndrome).
The intracranial part pierces the dura and arachnoid mater, ascends anterior to the hypoglossal roots inclining anterior to the medulla oblongata, at the lower pontine border it unites with its fellow to form the basilar artery.

 

Now we pay attention  to four large branches of the external carotid artery: lingual, facial, maxillary and superficial temporal (see the picture 14).
At first is about the lingual artery. It brings the blood supply to the tongue, palatine tonsils, soft palate, sublingual glands, muscles of the oral cavity floor.
It originates from the external carotid artery opposite the tip of the hyoid`s greater horn (see the picture 15, the origin and the tip are marked with blue lines). At the commencement it lies superficially, being covered only by the skin, fascia and platysma. Then it ascends medially and descends to the level of the hyoid bone again, making a loop which is crossed externally by the hypoglossal nerve. Thereafter the artery ascends again, medial to the middle pharyngeal constrictor, deep to the hyoglossus, digastric tendon, submandibular gland, mylohyoid (see the picture 16) and enter the tongue.

  

 

 

The lingual artery passes through the area which is called the Pirogov`s (lingual) triangle (see the picture 17). It is situated within the submandibular triangle and bounded posteriorly by the tendon of the digastric; superiorly by the hypoglossal nerve and its vena comitans; and anteriorly by the posterior edge of the mylohyoid (see the picture 18; the triangle is marked with green lines). The floor of the triangle is formed by the hyoglossus. The Pirogov`s triangle is the place of choice for bandaging lingual artery; here it can be ligated for final stop bleeding.

Now is about the facial artery. It supplies the soft palate, palatine tonsils, auditory tube, pharynx, submandibular gland, the oral cavity floor, chin, cheek, lips, nose, lacrimal sac.
The facial artery arises from the external carotid artery within the carotid triangle (see the pictures 3, 14), immediately above the hyoid`s greater horn. It arches upward and lies in the groove on the submandibualr gland`s posterior aspect, beig between the gland and medial pterygoid. Then it curves round the inferior mandibular border anterior to the masseter to enter the face. Thereafter it ascends towards the medial angle of eye across the mandible, buccinator, lateral to the nose and joins the dorsal nasal branch of the internal carotid artery.
At the origin the artery lies superficially, covered by the skin, fasciae and platysma, often crossed by the hypoglossal nerve (picture 19). Then it passes deep to the digastric, stylohyoid, submandibualr gland (picture 20). In the face the pulse of the artery can be felt as it crosses the mandible; here the artery is just beneath the platysma. When ascends, it is covered by the skin, fat of the cheek, zygomatic muscles and terminally it is embedded in the levator labii superioris alaeque nasi (picture 19).
For the temporary stop bleeding we should press the facial artery at the place where it crosses round the inferior mandibular border, about 2 cm anterior to the mandibular angle (picture 21; the place is marked with green circle).

 

The other two arteries (maxillary and superficial temporal), to which we pay our attention, are the terminal branches of the external carotid. The maxillary artery arises behind the mandibular neck. It has three segments: the first (mandibular), second (pterygoid) and third (pterygopalatine) (picture 22: blue lines show the boundaries between the segments; picture 23 shows the segments and the branches arising from them).
The first segment passes between the mandibular neck and sphenomandibular ligament, in contact with the auriculotemporal and inferior mandibular nerves (picture 24). Its branches mainly supply temporomandibular joint, external acoustic meatus, tympanic membrane, tympanic cavity, dura mater, trigeminal ganglion and its roots, facial nerve and its ganglion, mylohyoid, chin, buccal mucosa, lower teeth and gum, mandible, sphenoid and temporal bones.
One of the largest branches of this part is the middle meningeal artery. It enters the skull to supply the dura mater through the foramen spinosum and lies in a groove of the squamous temporal bone. Its surface projection is the middle of the zygomatic arch.

 

The second (pterygoid) segment of the maxillary artery passes in the infratemporal fossa; it ascends obliquely forwards medial to the temporalis and superficial to the lower head of the lateral pterygoid (picture 25 shows the maxillary artery`s parts and surrounding muscles).
The branches of this segment supply the pterygoid muscles, temporalis, masseter, buccinator.
The third (pterygopalatine) segment passes between the heads of the lateral pterygoid and through the pterygomaxillary fissure into the pterygopalatine fossa, where it is situated anterior to the pterygopalatine ganglion (picture 26 shows the pterygopalatine fossa with the sphenopalatine foramen from the outside; picture 22 shows the pterygopalatine segment).
The picture 27 shows the sphenopalatine foramen from the inside with entering sphenopalatine artery and the descending palatine artery (the branches of the third segment). You can see that the sphenopalatine arterysupplies the nasal mucosa (also the frontal, maxillary, ethmoid and sphenoid sinuses); the descending palatine artery `s branches (greater and lesser palatine arteries) supply the oral mucosa, passing through their canals.

 

The picture 28 shows the infraorbital artery arising from the third segment and passing through the infraorbital canal and foramen. Its dental branches supply the upper incisors, canine teeth, gingiva and maxillary sinus. After the infraorbital artery leaves its canal it supplies the tissues on the face. The upper molars and premolars are supplied by the posterior superior alveolar (dental) artery which arises from the maxillary artery as it enters the pterygopalatine fossa.
And two more branches of the pterygopalatine segment are the pharyngealartery and the artery of the pterygoid canal. Both arteries supply the nasopharynx and auditory tube; the first artery also supplies the mucosa of the nasal roof and sphenoidal sinus, the second one supplies the nerve of the pterygoid canal and tympanic cavity.
The picture 29 shows the relations of the pterygopalatine segment.

The superficial temporal artery begins in the parotid gland behind the mandibular neck, crosses the zygomatic process of the temporal bone and about 5 cm above divides into its terminal branches (frontal and parietal) (picture 30).
As the superficial temporal artery crosses the zygomatic process it is covered by the auricularis anterior; in the parotid gland it is crossed by the facial nerve branches.
The artery supplies: parotid gland; temporomandibualr joint; masseter; temporalis; tissues on the head in frontal and parietal regions; tissues on the face in the infraorbital, zygomatic and lateral facial regions; anterior part of the auricle and external acoustic meatus.
The superficial temporal artery is palpable through the skin and fascia; its projection line ascends from the middle of the zygomatic arch to the top. The point for the temporary stop bleeding from the artery is 1-2 cm above the arch.

Arterial anastomoses in the head and neck

To conclude the material about the arteries of the head and neck, we need to talk about the intersystem arterial anastomoses in these regions.
The main anastomoses between the external and internal carotid arterial systems are:
1. A. dorsalis nasi (from the ophthalmic artery which is from the internal carotid) and a. angularis (from the facial artery which is from the external carotid); (picture 1; the area of the anastomosis is marked with green circle)
2. A. supraorbitalis (from the ophthalmic artery which is from the internal carotid) and r. frontalis (from the superficial temporal artery which is from the external carotid); (picture 2; the area of the anastomosis is marked with green circle)
3. A. ethmoidalis anterior (from the ophthalmic artery which is from the internal carotid) and a. sphenopalatina (from the maxillary artery which is from the external carotid); (picture 3; the area of the anastomosis is marked with green circle)
4. A. meningea anterior (from anterior ethmoid artery which is from the ophthalmic artery; the latter is from the internal carotid) and a. meningea media (from the maxillary artery which is from the external carotid); (picture 4; the area of the anastomosis is marked with green circle)
5. Aa. caroticotympanicae (from the internal carotid) and aa. tympanicae (from the maxillary artery which is from the external carotid)

 

The anastomoses between the internal carotid and subclavian arterialsystems are on the cerebral base (Willis`s circle). It is between aa. communicans posteriores (from the internal carotid) and aa. cerebri posteriores (from the basilar artery which is from the vertebral arteries; the vertebral arteries are from the subclavian artery) (picture 5).
The anastomoses between the external carotid and subclavian arterialsystems are:
1. A. thyroidea superior (from the external carotid) and a. thyroidea inferior (from the thyrocervical trunk of the subclavian artery) and their branches (a. laryngea superior and a. laryngea inferior respectively). These anastomoses are in the thyroid gland and larynx respectively (picture 6).
2. A. occipitalis (from the external carotid) and a. cervicalis ascendens (from the thyrocervical trunk of the subclavian artery) (picture 7).
3. A. occipitalis (from the external carotid) and a. cervicalis profunda (from the costocervical trunk of the subclavian artery)
4. A. occipitalis (from the external carotid) and spinal branches of the a. vertebralis (from the subclavian artery)

Last three anastomoses are in the deep cervical muscles.

Bilateral intersystem anastomoses of the head and neck (between the right and left branches of the subclavian and external carotid arteries) are also of great clinical importance. They are:
1. Between the superficial temporal arteries (in the galea aponeurotica)
2. Between the facial arteries and between the maxillary arteries (in the palate)
3. Between the lingual arteries (in the tongue)
4. Between the ascending pharyngeal arteries (in the pharynx)
5. Between the superior thyroid arteries and between the inferior thyroidarteries (in the thyroid gland)
6. Between the labial branches of the facial arteries (in the lips)

Abdominal aorta

The abdominal aorta ends in the bifurcation into the common iliac arteries; each of them divides into external and internal iliac arteries (picture 1). The abdominal aorta`s branches can be classified as parietal (supplying walls) and visceral (supplying organs). And this is clear because the abdominal cavity has the walls (as you remember, posterior, laterals, superior, anterior) and the abdominal organs, and everything is needed in blood supply.

The anterior, lateral and posterior abdominal walls are formed by the abdominal muscles, their fasciae, subcutaneous tissue, skin with participation of the skeleton, of course; the superior wall is formed by the diaphragm. Below, the abdominal cavity is continuous with the pelvic cavity.

Of the abdominal walls, the parietal aortic branches (inferior phrenic arteries, lumbar arteries) (picture 1) supply inferior diaphragmatic surface and posterolateral aspect, since the abdominal aorta lies close to the vertebral column. The anterolateral abdominal walls are supplied by the superior and inferior epigastric arteries (the first one is from the internal thoracic artery which is a branch of the subclavian artery; the second one is from the external iliac artery) (picture 1,2). The anterior aspect of the diaphragm receives the blood from the musculophrenic artery (a branch of the internal thoracic artery).

So, the inferior phrenic arteries anastomose with the musculophrenic in the diaphragm; the superior epigastric artery anastomoses with the inferior epigastric in the anterior abdominal wall (picture 2); both epigastric arteries anastomose with the lumbar arteries in the lateral abdominal walls.

Now, let`s name the viscera located in the abdominal cavity. They are liver, gallbladder, pancreas, stomach, spleen, small and large intestine (these are unpaired organs hence, are supplied by unpaired visceral aortic branches) (picture 3); and kidneys, upper parts of the ureters, suprarenal glands (they are paired and supplied by paired visceral aortic branches) (picture 4).

For the blood supply of the pelvic organs, the internal iliac artery exists. The pelvic organs are rectum, urinary bladder, lower parts of the ureters, urethra; in females the uterus, uterine tubes and ovaries; in males the prostate, seminal vesicles, deferent ducts.
But the ovaries and testes (the latter ones are located in the scrotum, i.e. outside the abdominal and pelvic cavities) are partially supplied by the paired visceral aortic branches because both organs in embryo start to develop in the abdominal cavity and then, before birth, descend into the pelvic cavity and scrotum respectively.

The upper part of the rectum is also supplied by the branch of the aorta (the superior rectal artery from an unpaired visceral aortic branch), while the middle and lower parts are supplied by the internal iliac artery`s branches.

So, between the branches of the aorta and internal iliac artery anastomoses occur: in the ovaries (ovarian artery from the aorta and ovarian branch of the uterine artery from the internal iliac) (picture 5); in the rectum (between the superior rectal artery from the aorta and middle rectal artery from the internal iliac) (picture 6). In the testis, the testicular artery (from the aorta) anastomoses with cremasteric artery (from the inferior epigastric artery which is a branch of the external iliac artery).

 

Fetal circulation and shunts

The ductus arteriosus (picture 1), also called the ductus Botalli, is a blood vessel connecting the pulmonary artery to the proximal descending aorta. It allows most of the blood from the right ventricle to bypass the fetus’s fluid-filled non-functioning lungs. After birth, it becomes the ligamentum arteriosum. The closure occurs during 72 hours after birth.
Failure of the ductus arteriosus to close after birth results in a condition called patent ductus arteriosus. Patency leads to pulmonary hypertension and cardiac arrhythmias, if it is not corrected.

 

The ductus venosus (Arantius’ duct ) (picture 2)connects the umbilical vein to the inferior vena cava. Thus, it allows oxygenated blood from the placenta to bypass the liver.
Ductus venosus naturally closes during the first week of life. Functional closure occurs within minutes of birth. Structural closure occurs during 3 to 7 days.
After closure, the ductus venosus becomes the ligamentum venosum, which can be found in the fissure for ligamentum venosum on the visceral surface of the liver (picture 3).
Failure of the ductus venosus to close after birth results in a condition called patent ductus venosus, the intrahepaticportosystemic shunt.

The foramen ovale, also called foramen Botalli, ostium secundum of Born or falx septi (picture 4), allows blood to enter the left atrium from the right atrium. After birth it becomes the fossa ovalis (picture 5). It closes normally during 12 weeks after birth.
In about 25% of adults the foramen ovale does not close completely, but remains as a small patent foramen ovale. It can cause congestive heart failure, cardiac arrhythmias, myocardial infarction.

 

The system of superior vena cava

1. The structure of the jugular, azygos and hemiazygos veins.

2. The anastomoses between the tributaries of the internal jugular vein.

1. The structure of the jugular, azygos and hemiazygos veins.

The topic “The veins of the head and neck” is one of the most difficult topics in the third semester. So, I will give it briefly step by step.
At first, there are three big veins in the neck region (sequentially from larger to smaller): the internal jugular vein, external jugular vein and anterior jugular vein (picture 1). They belong to the system of the superior vena cava.
During our classes we`ve talked about the direction of arterial and venous blood and about the veins do not have branches unlike the arteries, they have tributaries. Thus, we have to describe the veins from the periphery.
The internal jugular vein is a direct continuation of the dural sigmoid sinus at the jugular foramen (picture 2); it travels down, lateral to the common carotid artery and vagus nerve, and joins the subclavian vein behind the sternoclavicular joint (picture 1).

The external jugular vein is formed by a merger of the posterior auricular and occipital veins (picture 41). It drains into the venous angle formed by the internal jugular and subclavian veins (picture 1). Its tributaries are the transverse cervical vein and suprascapular vein which drain the cervical muscles, skin and occipital region.
While the internal jugular vein is hidden by the sternocleidomastoid, the external jugular vein lies superficial to it, being covered by the skin, superfiicial cervical fascia and platysma.
The anterior jugular veins arise from the superficial veins of the mental region and descend on the mylohyoid and sternohyoid muscles close to the midline. In the lower third of the neck they enter spatium interaponeuroticum suprasternale (over the jugular notch, between the superficial and pretracheal layers of the proper cervical fascia) and here they are interconnected by a transverse anastomosis, the jugular venous arch (picture 3). Each anterior jugular vein joins the external jugular vein (picture 1).

All tributaries of the internal jugular vein can be grouped as follows: intracranial and extracranial.
The intracranial tributaries are:
1) Dural venous sinuses;
2) Diploic veins;
3) Emissary veins;
4) Cerebral veins;
5) Meningeal veins;
6) Orbital veins;
7) Labyrinthine veins;
8) Venous plexuses of the skull base

The dural venous sinuses are the canals in the splitting of the dura mater, which receive blood from the brain, orbit and eyeball, internal ear, skull bones and cerebral meninges. All venous blood from the sinuses drains into the internal jugular vein. See the video which will remind you the main things about the sinuses.

The diploic veins occupy the channels in the diploё of some cranial bones; they are devoid of valves, contributing to the blood flow in two directions. They begin to develop at about two years after birth. They communicate with the meningeal veins, dural sinuses and pericranial veins. The picture 4 shows the diploic veins (green lines); red lines and words are the sinuses and veins where the diploic veins open.
The emissary veins traverse cranial openings, connecting the dural venous sinuses and extracranial veins. The picture 5 shows the main emissary veins (green lines); red lines and words are the sinuses where the emissary veins open.
So, you see the diploic and emissary veins open into the dural sinuses; the venous blood from all the sinuses flows into the sigmoid sinus hence, finally it drains into the internal jugular vein.

The cerebral veins drain the surface and interior of the hemispheres; they are grouped as superficial and deep.
The superficial cerebral veins form the superior, middle and inferior groups; they are shown in the picture 6: the veins of the superior group are in green ovals; the vein of the middle group is in red oval; the veins of the inferior group are in blue oval.
The superior and inferior cerebellar veins are also superficial.
The deep cerebral veins include the basal vein, shown in the picture 7 (underlined with red). It is formed by the union of anterior and deep middle veins which accompany the corresponding branches of the internal carotid artery.
Also here belong the talamostriate veins, the great cerebral vein (vein of Galen); they are shown in the picture 8  (underlined with green). Besides, the deep cerebral veins include the choroid veins, the internal cerebral veins, the veins of the septum pellucidum and the vein of the brain stem.

The meningeal veins begin from the plexiform vessels in the dura mater and drain into the veins in the outer dural layer which connect with the dural sinuses and with the diploic veins.

The orbital veins are the superior ophthalmic and inferior ophthalmic veins. Their tributaries mainly correspond to the branches of the ophthalmic artery. So, they drain the orbital content, forehead, nasal mucosa, nasal root. Both ophthalmic veins open into the cavernous sinus. Besides, the inferior ophthalmic vein connects with the pterygoid plexus (picture 9).

The labyrinthine veins drain the internal ear, pass through the internal acoustic meatus and open into the inferior petrosal sinus.

The venous plexuses of the skull base surround the content of the foramen ovale, carotid canal and hypoglossal canal. Two first connect the pterygoid plexus with cavernous sinus. And the last connects the internal vertebral plexus with occipital and inferor petrosal sinuses.

So, all the tributaries of the internal jugular vein described below are intracranial.
You could see that the diploic, emissary, cerebral, meningeal, orbital and labyrinthine veins finally drain into the dural sinuses; the sigmoid sinus is continuous with the internal jugular vein.

No we can talk about the extracranial tributaries of the internal jugular vein.
They are
1) Facial vein. It takes venous blood from the eyelids, nose, lips, upper jaw, parotid gland, palate, submandibular gland, mental region and drains into the internal jugular vein.
2) Retromandibular vein. It is formed by the joining of the superficial temporal vein and maxillary vein (picture 10). It takes venous blood from the temporal and parietal regions, external ear, parotid gland, temporomandibular joint, tympanic cavity, zygomatic region. Also it takes the pterygoid plexus which in its turn drains the dura mater, masticatory muscles, lower jaw, nasal cavity.
3) Lingual vein (picture 11). It takes venous blood from the tongue, sublingual gland, oral cavity floor and drains into the internal jugular vein.
4) Pharyngeal veins. They drain the pharynx, palate, auditory tube, deep cervical muscles, dura mater and open into the internal jugular vein.
5) Superior thyroid vein. It drains the thyroid gland, larynx, sternocleidomastoid and opens into the internal jugular vein.
6) Middle thyroid vein. It drains the thyroid gland and takes the venous plexus situated in spatium interaponeuroticum suprasternale.

As already mentioned the internal jugular vein joins the subclavian vein to form the brachiocephalic vein (picture 12). The place of the joining is just opposite the sternoclavicular joint. Behind the junction of the right I rib to the sternum, the two brachiocephalic vein merge to form the superior vena cava which opens into the right atrium.
The brachiocephalic veins take the blood from (picture 12):
1) Thyroid gland, larynx, trachea, pharynx, oesophagus through the inferior thyroid veins and plexus thyroideus impar;
2) Mediastinal organs (thymus, pericardium, bronchi, trachea, oesophagus, lymph nodes) through the veins of the same names, pericardiophrenic and internal thoracic veins;
3) Deep cervical muscles through the deep cervical vein;
4) Vertebral venous plexuses through the vertebral vein (it accompanies the vertebral artery);
5) Abdominal muscles and diaphragm through the internal thoracic vein;
6) Proper chest muscles, ribs, sternum through the anterior intercostal veins which open into the internal thoracic vein (picture 13);
7) Upper three posterior intercostal spaces on the left side through vena intercostalis suprema sinistra.

 
While on the front side of the chest there are the brachiocephalic and internal thoracic veins, on the posterior side there are two large veins (10-12 mm in diameter): azygos (to the right) and hemiazygos (to the left) veins. They are direct continuations of the right and left ascending lumbar veins. They ascend through the slits between the medial and intermediate diaphragmatic crura and pass along the vertebral column in the posterior mediastinum. The hemiazygos vein is shorter; it crosses the VIII or IX thoracic vertebra to drain into the azygos vein. The azygos vein arches over the right principal bronchus and opens into the superior vena cava (picture 14).
Both azygos and hemiazygos veins take the posterior intercostal veins (theazygos vein takes the XII –IV right posterior intercostal veins; the hemiazygos – the XII-VII left posterior intercostal veins). Both veins drain the mediastinal organs and diaphragm.
Besides, the azygos vein takes the right superior intercostal vein (which drains the upper three intercostal spaces on the right). The hemyazygos vein takes the accessory hemiazygos vein (which drains the IV-VI intercostal spaces on the left) (picture 15).
To summarize the drainage of the intercostal spaces we should note that each intercostal space can be divided into anterior and posterior parts. These parts are drained by the anterior and posterior intercostal veins correspondently. The anterior intercostal veins open into the internal thoracic veins which in turn drain into the brachiocephalic veins (picture 14).
The posterior intercostal veins on the right side: XII-IV open into azygos vein; III-I open into the right superior intercostal vein which in turn drains into the azygos vein.
The posterior intercostal veins on the right side: XII-VII open into the hemiazygos vein; VI-IV open into the accessory hemiazygos vein; III-I open into vena intercostalis suprema sinistra which drains into the left brachiocephalic vein (picture 16).
2. The anastomoses between the tributaries of the internal jugular vein.
Like arteries, the veins make anastomoses with each other. Now we will talk about the venous anastomoses in the head and neck.
At first, the anastomoses between the extracranial tributaries of the internal jugular vein:
1. Between the facial vein and the pterygoid plexus through the deep facial vein (picture 17; the anastomosis is marked with green circle);
2. Between the facial vein and pharyngeal veins (may be dangerous in the operations on the tonsils);
3. Between the facial vein and superficial temporal vein through the transverse facial vein (picture 18; the anastomosis is marked with green circle);
4. Between the pterygoid plexus and pharyngeal veins.
Then, the anastomoses between the extra- and intracranial tributaries of the internal jugular vein:
1. Between the facial vein and superior ophthalmic vein through the supraorbital vein (picture 17; the anastomosis is marked with green circle); this anastomosis is dangerous because of a possible spreading of infection to the cavernous sinus;
2. Between the pterygoid plexus and inferior ophthalmic vein (picture 19);
3. Between the pterygoid plexus and meningeal veins;
4. Between the dural sinuses and diploic veins with the superficial cerebral veins through the emissary veins.
5. Between the venous plexuses of the skull base and pterygoid plexus;
6. Between the venous plexuses of the skull base and pharyngeal veins;
7. Between the supraorbital vein and superficial temporal vein.
And lastly, the intersystem venous anastomoses:
1. Between the external jugular vein with sigmoid and transverse sinuses through the mastoid and occipital emissary veins;
2. Between the external jugular vein and retromandibular vein (picture 20);
3. Bilateral anastomoses (between righ and left veins) in the scalp, nasal cavity, oral cavity, tongue, pharynx, thyroid gland, larynx
Anastomoses between the portal and caval venous systems

Porto-caval anastomoses are the connections between the tributaries of the caval veins and portal vein.
The first porto-caval anastomosis is in the wall of the abdominal part of the oesophagus; it is between the left gastric vein, from where blood drains into the portal vein, and oesophageal veins, from where blood passes into the azygos and hemyazygos veins and then into the IVC (picture 1, 2).
There are four venous plexuses in the oesophageal wall: intraepithelial, mucous, submucous and adventitial. The largest veins are placed in the submucous plexus.
During the increased pressure in the portal vein, the drainage from the left gastric vein is impaired and the increased volume of blood passes into the oesophageal plexuses that causes their varicose expansion. In this case the varicose nodes can protrude into the oesophageal lumen and can be injured by food that leads to oesophageal-gastric hemorrhage.

The next porto-caval anastomosis is in the rectal wall between the superior rectal and middle rectal veins (picture 3, 4). There are the following venous plexuses in the rectal wall: internal (submucous plexus and subcutaneous (situated under the skin around the anus) plexuses) and external (subfascial plexus situated on the surface of the rectal muscle layer) (picture 5). The drainage from the plexuses occurs by the following ways:
1. Superior rectal vein then the inferior mesenteric vein then the portal vein;
2. Middle rectal vein then the internal iliac vein then the common iliac vein then IVC;
3. Inferior rectal vein then the internal pudendal vein then the internal iliac vein then the common iliac vein then IVC.
The submucous plexus consists of so called cavernous bodies which form the anal columns protruding into the rectal lumen and providing hermetic closure of the rectal sphincters.
The increased pressure in the portal system (the portal hypertension) (as well as hard physical load, pregnancy, the increased pressure in the rectum) leads to varicose expansions of the cavernous bodies and (hemorrhoids).

One more porto-caval anastomosis is in the anterior abdominal wall. Here the following veins anastomose: paraumbilical veins, superior epigastric vein and inferior epigastric vein (picture 6), and besides the thoracoepigastric vein and superficial epigastric vein (picture 7).
The paraumbilical veins open into the portal vein.
The superior epigastric vein drains into the internal thoracic vein; the latter into the subclavian vein; the latter into the brachiocaphalic vein which opens into the SVC.
The inferior epigastric vein opens into the external iliac vein; the latter into common iliac vein; the latter into IVC.
The thoracoepigastric vein opens into axillary vein; the latter into subclavian vein; the latter into brachiocephalic vein; the latter into SVC.
The superficial epigastrci vein drains into the femoral vein; the latter into the external iliac vein; the latter into common iliac vein; the latter into IVC.
The portal hypertension leads to the expansion of the veins surrounding the umbilicus that is called “caput medusae” (picture 8).
  
 And last porto-caval anastomoses are in the posterior abdominal wall. Here the following veins anastomose:
1. The tributaries of the splenic vein which opens into the portal vein;
2. The tributaries of the superior and inferior mesenteric veins which open into the portal vein;
3. The tributaries of the lumbar veins which drain into IVC
And finally is about the causes of the portal hypertension. There are three groups of causes:
1. Subhepatic block which occurs because of the thrombosis, dysplasia or constriction of the portal vein by the hepatic tumor or increased lymph nodes.
2. Intrahepatic block which occurs because of the compression of the intrahepatic veins in the hepatic diseases: cirrhosis, hepatic tumors, hepatic cysts.
3. Suprahepatic block when the drainage through the hepatic veins is disturbed.

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