About the Anatomy of the vena cava and, in particular, about its ascending part

As for the vena cava, its root first diverges into parts like hairs in the liver itself in order to extract food from the branches of the “portal” vein, which are also divided into hairs. As for the branches of the vena cava, they go from the convexity of the liver to its interior, and the branches of the “gate” go from the concave part of the liver to its interior. Then the vein trunk comes out near the bulge and is divided into two parts: the ascending part 6 and the descending part. As for the ascending part, it breaks through the thoraco-abdominal barrier, passes into it and leaves two vessels in it, which diverge in the thoraco-abdominal barrier and deliver nutrients to it.

Then the ascending part runs parallel to the sac of the heart and sends into it many branches, which spread out in the sac like hairs and nourish it.

Next, the ascending part is divided into two parts. One part of it is large, approaches the heart and passes into it near the right ear of the heart. This vessel is the largest of the heart vessels. It is larger than other vessels because other vessels serve to draw in air, and this one serves to attract nutrients, and nutrients are denser than air and need a wider passage for them and a larger vessel containing them. As soon as this vein enters the heart, three membranes are created for it, the flap of which faces from the outside in, so that the heart, contracting, extracts the nutrient from this vein, and it does not return back when the heart expands again. The membranes of the heart are the densest membranes.

This vein, running parallel to the heart, leaves three vessels.

One vessel goes from it to the lung. It begins at the origin of the arteries, near the left artery, and turns in the right cavity towards the lung. This vein is created with two membranes, like an artery, and is therefore called an “arterial vein”.

The first benefit from this is due to the fact that the blood that leaks from the arterial vein is extremely liquid, like the substance of the lung, for this blood has recently been in the heart and has not reached sufficient maturity in it to pour out into the venous artery. And the second benefit is that the blood reaches an excellent degree of maturity in the venous artery.

As for the second of these three branches, it goes around the heart and then diverges inside it to nourish it.

This occurs at the point where the vena cava almost plunges into the right ear, entering the heart.

The third vein deviates, especially in humans, to the left side, then goes to the fifth thoracic vertebra, rests on it and diverges in the eight lower ribs, in the muscles that adjoin them, and in other bodies.

As for the part of the vena cava, which passes after the three mentioned branches have separated from it, and it passes the region of the heart, rising upward, then hairy branches diverge from it in the upper part of the membranes dividing the chest in half, in the upper part of the bursa and in loose meat called tusa.

Then, near the collarbone, two branches depart from it, which are directed towards the collarbone, going obliquely; the more they deepen, the more they move away from each other.

Each of these branches becomes two branches, which descend, one on each side, to the sternum, right and left, and reach the dagger-shaped process.

On its way, this vein gives off branches that diverge in the muscles located between the ribs, and their openings meet the openings of the vessels growing in these muscles; a group of these branches extends to the muscles located on the chest.

When these veins reach the dagger-shaped process, a group of them moves forward to the crowded muscles that move the scapula and diverges in it, while another group descends under the rectus muscles and branches from it diverge into these muscles; their ends adjoin the ascending parts of the sacral vein, which we will talk about shortly.

As for the rest of each of these trunks - and there are a pair of them - then each of them makes up five branches. One branch diverges in the chest and feeds the four upper ribs; another branch feeds the area of ​​the shoulder blades, the third goes to the muscles lying deep in the neck to nourish them, the fourth passes through the opening of the six upper vertebrae of the neck and, bypassing them, goes to the head. The fifth large branch, the largest of them all, approaches the armpit from all sides, and its branches are divided into four branches. The first of them diverges on the muscles lying on the sternum, which belong to the muscles that move the joint of the scapula; the second diverges in the loose meat and in the membranes located under the armpit; the third descends, passing along the side of the chest to the abdominal walls. The fourth branch is the largest and splits into three parts. Part of it diverges in the muscles lying in the recess of the scapula, part in the large muscle lying under the armpit. The third part - the largest - runs along the humerus to the arm; this is the vein called the axillary.

The part remaining from the first fork, each of the two branches of which has divided into many branches, rises to the neck, but before going deeper there, it is divided into two parts; one of them is the external jugular vein, the other is the deep jugular vein.

The external jugular vein divides, rising from the collarbone, into two parts. One of them, having separated, goes forward and to the side, and the other first goes forward, moving downwards, then rises up, again goes along the surface of the collarbone and goes around the collarbone in a circle. Then it rises and rises, going outside the neck, until it reaches the first part and merges with it, and then the well-known external jugular vein is formed from them.

And before the second branch merges with the first, two pairs are separated from it, one of which goes across; then the parts of this pair meet at the junction of the two clavicles at the place of the depression. And the other pair goes obliquely, outside the neck, and the branches that make it up do not meet after that.

From these two pairs there are web-like branches that escape from view. However, from this second pair especially diverging in the number of its branches are three visible veins, which are of noticeable size, while the rest are invisible.

One of these three veins stretches along the shoulder blade - this is the vein called the “scapular”, and the mullet extends from it. Two branches, on either side of this scapular vein, together accompany it to the apex of the scapula, but one of them lingers there and does not go further than the scapula, but diverges at it.

As for the second branch, which goes forward, it bypasses the top of the scapula and follows to the top of the humerus, where it branches. And the brachial vein itself passes by both branches and follows to the end of the arm. Here!

As for the external jugular vein, after the two parts that form it merge, it divides into two branches. Part of it goes deep and is divided into small branches that diverge in the upper jaw, and into many larger branches that diverge in the lower jaw. Parts of both kinds of branches diverge around the tongue and along the outer side of the parts of the muscles located in this place, while the other part goes outside and diverges in the places adjacent to the head and ears.

As for the deep vein, it accompanies the esophagus and ascends straight with it, leaving branches along its path that merge with the branches coming from the external jugular vein. All these branches diverge in the esophagus, in the larynx and in all parts of the deep-lying muscles, and their end reaches the end of the lambdoid suture. There, eight branches branch off from it, which diverge in the organs lying between the first and second vertebrae, and the hair vessel also extends to the joint of the head and neck.

More branches branch off from this vein and go to the membrane that envelops the skull; they reach the junction of two skull bones and go deep into the skull there.

The rest of this vein, having sent out the mentioned branches, passes deep into the skull to the end of the lambdoid suture, and from it branches branch into both membranes of the brain to nourish them and in order to attach the hard shell to what surrounds it and lies above it. Then this vein moves forward and feeds the membrane that envelops the brain, then descends from the thin membrane to the brain and diverges in it, just as arteries diverge. All these veins are surrounded by a fold of a dense membrane, which leads them to a large place, that is, to an empty space into which the blood flows, where it collects and from where it diverges between two folds. This space is called the "press".

When these branches approach the middle ventricle of the brain, they need to turn into large vessels capable of sucking blood from the “press” and the ducts branching from it. Then these veins stretch from the middle ventricle to both anterior ventricles; there they meet the ascending arteries and intertwine into a membrane called the “villous membrane network.”