Thursday, April 28, 2011

The Veins

General feature

Thin walls, larger lumens, venous valves, venous plexus

Two sets of veins:

Superficial vein

is a term used to describe a vein that is close to the surface of the body

Superficial veins are not paired with an artery, unlike the deep veins, which typically have an artery with the same name close by Superficial veins are important physiologically for cooling of the body. When the body is too hot the body shunts blood from the deep veins to the superficial veins, to facilitate heat transfer to the surroundings.

Deep vein

is a term used to describe a vein that is deep in the body
Deep veins are almost always beside an artery with the same name (e.g. the femoral vein is beside the femoral artery).
Collectively, they carry the vast majority of the blood back to the heart

The return of blood to the heart is assisted by the action of the skeletal-muscle pump which helps maintain the extremely low blood pressure of the venous system.
Fainting can be caused by failure of the skeletal-muscular pump. Long periods of standing can result in blood pooling in the legs, with blood pressure too low to return blood to the heart.


Systemic veins

To understand the arrangement of the veins in systemic circulation,we should regard them as three systems:

1)Cardiac veins system
2) Superior vena cava system—S.V.C and its tributaries
3) Inferior vena cava system—I.V.C and its tributaries
Every system takes charge of several regions of our body.
1)Cardiac veins system---- drain the venus blood of heart
2) Superior vena cava system--- head,neck,thorax,upper
limb
3) Inferior vena cava system--- abdoman,pelvis,lower limb


Superior vena cava system

Superior vena cava

It begins posterior to the lower edge of the right first costal cartilage, where the right and left brachiocephalic veins join, and returns to the right atrium


Brachiocephalic veins

The left and right brachiocephalic veins (or
innominate veins) are formed by the union of
internal jugular vein and subclavian vein.


The internal jugular veins are the main returning route for the venus blood of the head and neck
The subclavian veins are the main returning route for the venus blood of the upper limb
The venus blood in the thorax is drained mainly by the azygos system of veins .
We can regard the superior vena cava as the aortic arch plus the thoracic aorta for they have similar control area of our body.



Veins of head and neck

The internal jugular vein

It runs from its origin at the jugular foramen to its termination behind the sternal end of the clavicle, where it joins the subclavian vein to form the brachiocephalic vein.


VEINS OF THE FACE

a)The veins of the face accompany the arteries & drain into the common facial & retromandibular veins, they communicate with the cavernous sinus

b)The veins of each side form a W shaped arrangement, each corner of the W is prolonged upwards in to the scalp & downwards in to the neck

c)The facial vein is the largest vein of the face, begins as an angular vein at the medial angle of the eye. The angular vein continue as the facial vein running downwards and backwards joins the anterior division of the retromandibular vein to form the common facial vein, later drains into the internal jugular vein


The posterior conner of the W is formed by the join of posterior auricular vein and posterior division of the retromandibular vein. They form the external jugular vein.


Veins of thorax

THE AZYGOS VEIN

This vein drains the thoracic wall & the upper lumbar region
It forms an important channel connecting the SVC & IVC
The term azygos means unpaired
formation
The azygos vein is formed by the union of 1) ascending lumbar veins2)right subcostal vein


Tributaries of the azygos vein include:

the right superior intercostal vein (a single vessel formed by the junction of the second, third, and fourth intercostal veins),
fifth to eleventh right posterior intercostal veins,
the hemiazygos vein,
the accessory hemiazygos vein,
esophageal veins,
mediastinal veins,
pericardial veins, and
right bronchial veins


Veins of upper limb

These include the superficial veins and the deep veins. The superficial veins first drain into the deep veins and then they together return to the heart

THE SUPERFICIAL VEINS

These veins assume important in medical practice because they are most common used for IV injection & for withdrawing blood for testing

Most of the superficail veins join to form 2 large veins, cephalic & basilic


CEPHALIC VEIN

It begins from the lateral end of the dorsal venous arch
It runs upwards through

1.Roof of snuffbox
2.Winds round the distal part of the forarm
3.Runs in front of the elbow
4.Runs in the deltopectoral groove
5.Joins the axillary vein or the subclavian vein

BASILIC VEIN

It begins from the medial end of the dorsal venous arch
Runs upwards

1)along the back of the med border of the f arm

2)winds round this border near the elbow

3)it pierces the deep fascia and joins the brachial vein or axillary vein


THE MEDIAN CUBITAL VEIN

it is a large communicating vein which shunts the blood from cephalic to the basilic vein

It begins from the cephalic vein 2.5 cm below the bend of the elbow, runs obliquely upwards & medially and ends in the basilic vein

It is a ideal place for IV injection

DEEP VEINS

The deep veins accompany the arteries of the same region and bear similar names


Inferior vena cava system

This system takes charge of the drainage of the venus blood from the abdoman,pelvis and the lower limbs.

We can regard it as the abdominal aorta plus the common iliac arteries for they have similar control area of our body.



Inferior vena cava

The inferior vena cava returns blood from all structures below the diaphragm to the right atrium of the heart.

It is formed when the two common iliac veins come together at the level of vertebra LV just to the right of midline.


Tributaries to the inferior vena cava include:
the common iliac veins;
the lumbar veins;
the right testicular or ovarian vein;
the renal veins;
the right suprarenal vein;
the inferior phrenic veins;
the hepatic veins

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