Veins are blood vessels that carry blood toward the heart. Most veins carry deoxygenated blood from the tissues back to the heart. In contrast to veins, arteries carry blood away from the heart. Veins are less muscular than arteries and are closer to the skin. There are valves in most veins to prevent backflow. Veins are present throughout the body as tubes. Veins are classified in a number of ways, including superficial vs. deep, pulmonary vs. systemic, large vs. small. Superficial veins are those closer to the surface of the body, have no corresponding arteries. Deep veins have corresponding arteries. Perforator veins drain from the superficial to the deep veins; these are referred to in the lower limbs and feet. Communicating veins are veins. Pulmonary veins are a set of veins. Systemic veins deliver deoxygenated blood to the heart. Most veins are equipped with valves to prevent blood flowing in the reverse direction. Veins are translucent, so the color a vein appears from an organism's exterior is determined in large part by the color of venous blood, dark red as a result of its low oxygen content.
Veins appear blue because the subcutaneous fat absorbs low-frequency light, permitting only the energetic blue wavelengths to penetrate through to the dark vein and reflect back to the viewer. The colour of a vein can be affected by the characteristics of a person's skin, how much oxygen is being carried in the blood, how big and deep the vessels are; when a vein is drained of blood and removed from an organism, it appears grey-white. The largest veins in the human body are the venae cavae; these are two large veins which enter the right atrium of the heart from below. The superior vena cava carries blood from the arms and head to the right atrium of the heart, while the inferior vena cava carries blood from the legs and abdomen to the heart; the inferior vena cava is retroperitoneal and runs to the right and parallel to the abdominal aorta along the spine. Large veins feed into these two veins, smaller veins into these. Together this forms the venous system. Whilst the main veins hold a constant position, the position of veins person to person can display quite a lot of variation.
The pulmonary veins carry oxygenated blood from the lungs to the heart. The superior and inferior venae cavae carry deoxygenated blood from the upper and lower systemic circulations, respectively; the portal venous system is a series of venules that directly connect two capillary beds. Examples of such systems include hypophyseal portal system; the peripheral veins carry blood from feet. Microscopically, veins have a thick outer layer made of connective tissue, called the tunica externa or tunica adventitia. During procedures requiring venous access such as venipuncture, one may notice a subtle "pop" as the needle penetrates this layer; the middle layer of bands of smooth muscle are called tunica media and are, in general, much thinner than those of arteries, as veins do not function in a contractile manner and are not subject to the high pressures of systole, as arteries are. The interior is lined with endothelial cells called tunica intima; the precise location of veins varies much more from person to person than that of arteries.
Veins serve to return blood from organs to the heart. Veins are called "capacitance vessels" because most of the blood volume is contained within veins. In systemic circulation oxygenated blood is pumped by the left ventricle through the arteries to the muscles and organs of the body, where its nutrients and gases are exchanged at capillaries. After taking up cellular waste and carbon dioxide in capillaries, blood is channeled through vessels that converge with one another to form venules, which continue to converge and form the larger veins; the de-oxygenated blood is taken by veins to the right atrium of the heart, which transfers the blood to the right ventricle, where it is pumped through the pulmonary arteries to the lungs. In pulmonary circulation the pulmonary veins return oxygenated blood from the lungs to the left atrium, which empties into the left ventricle, completing the cycle of blood circulation; the return of blood to the heart is assisted by the action of the muscle pump, by the thoracic pump action of breathing during respiration.
Standing or sitting for a prolonged period of time can cause low venous return from venous pooling shock. Fainting can occur but baroreceptors within the aortic sinuses initiate a baroreflex such that angiotensin II and norepinephrine stimulate vasoconstriction and heart rate increases to return blood flow. Neurogenic and hypovolaemic shock can cause fainting. In these cases, the smooth muscles surrounding the veins become slack and the veins fill with the majority of the blood in the body, keeping blood away from the brain and causing unconsciousness. Jet pilots wear pressurized suits to help maintain their venous blood pressure; the arteries are perceived as carrying oxygenated blood to the tissues, while veins carry deoxygenated blood back to the heart. This is true of the systemic circulation, by far the larger of the two circuits of blood in the body, which transports oxygen from the heart to the tissues of the body. However, in pulmonary circulation, the arteries carry deoxygenated blood from the heart to the lungs, veins return blood from the lungs to the heart.
The difference between veins a
Dorsal venous network of hand
The dorsal venous network of the hand is a network of veins in the superficial fascia on the dorsum of hand formed by the dorsal metacarpal veins. It is found on the back of the hand and gives rise to veins such as the cephalic vein and the basilic vein
Median antebrachial vein
The median antebrachial vein drains the venous plexus on the palmar surface of the hand. It travels up on the ulnar side of the front of the forearm and ends in the basilic vein or in the vena mediana cubiti; this article incorporates text in the public domain from page 662 of the 20th edition of Gray's Anatomy
Circumflex scapular artery
The circumflex scapular artery is a branch of the subscapular artery and part of the scapular anastomoses. It curves around the axillary border of the scapula, traveling through the anatomical "Triangular space" made up of the Teres minor superiorly, the Teres major inferiorly, the long head of the Triceps laterally, it enters the infraspinatous fossa under cover of the Teres minor, anastomoses with the transverse scapular artery and the descending branch of the transverse cervical. In its course it gives off two branches: one enters the subscapular fossa beneath the Subscapularis, which it supplies, anastomosing with the transverse scapular artery and the descending branch of the transverse cervical; the other is continued along the axillary border of the scapula, between the Teres major and minor, at the dorsal surface of the inferior angle anastomosis with the descending branch of the transverse cervical. In addition to these, small branches are distributed to the back part of the Deltoideus and the long head of the Triceps brachii, anastomosing with an ascending branch of the profunda brachii.
This article incorporates text in the public domain from page 588 of the 20th edition of Gray's Anatomy Anatomy photo:03:05-0101 at the SUNY Downstate Medical Center - "Triangular Space of Scapular Region" Anatomy photo:05:07-0302 at the SUNY Downstate Medical Center - "Major Branches of the Axillary Artery" Anatomy figure: 05:04-18 at Human Anatomy Online, SUNY Downstate Medical Center - "The axillary artery and its major branches shown in relation to major landmarks." Lesson3axillaryart&vein at The Anatomy Lesson by Wesley Norman
The subscapular artery, the largest branch of the axillary artery, arises from the third part of the axillary artery at the lower border of the subscapularis muscle, which it follows to the inferior angle of the scapula, where it anastomoses with the lateral thoracic and intercostal arteries, with the descending branch of the dorsal scapular artery, ends in the neighboring muscles. About 4 cm from its origin it gives off two branches, first the scapular circumflex artery and the thoracodorsal artery. From the thoracodorsal artery it supplies latissimus dorsi, while the scapular circumflex artery participates in the scapular anastamosis, it terminates in an anastomosis with the dorsal scapular artery. This article incorporates text in the public domain from page 588 of the 20th edition of Gray's Anatomy Illustration at microsurgeon.org Photo at mvm.ed.ac.uk lesson3axillaryart&vein at The Anatomy Lesson by Wesley Norman
The triceps triceps brachii, is a large muscle on the back of the upper limb of many vertebrates. It is the muscle principally responsible for extension of the elbow joint; the long head arises from the infraglenoid tubercle of the scapula. It extends distally anterior to the teres posterior to the teres major; the medial head arises proximally from the groove of the radial nerve. The medial head is covered by the lateral and long heads, is only visible distally on the humerus; the lateral head arises from the dorsal surface of the humerus and proximal to the groove of the radial nerve, from the greater tubercle down to the region of the lateral intermuscular septum. Each of the three fascicles has its own motorneuron subnucleus in the motor column in the spinal cord; the medial head is formed predominantly by small type I fibers and motor units, the lateral head of large type IIb fibers and motor units and the long head of a mixture of fiber types and motor units. It has been suggested that each fascicle "may be considered an independent muscle with specific functional roles."The fibers converge to a single tendon to insert onto the olecranon process of the ulna and to the posterior wall of the capsule of the elbow joint where bursae are found.
Parts of the common tendon radiates into the fascia of the forearm and can cover the anconeus muscle. All three heads of the triceps brachii are classically believed to be innervated by the radial nerve. However, a study conducted in 2004 determined that, in 20 cadaveric specimens and 15 surgical dissections on participants, the long head was innervated by a branch of the axillary nerve in all cases. A tendinous arch is the origin of the long head and the tendon of latissimus dorsi. In rare cases, the long head can originate from the lateral margin of the scapula and from the capsule of the shoulder joint; the triceps is an extensor muscle of the elbow joint and an antagonist of the biceps and brachialis muscles. It can fixate the elbow joint when the forearm and hand are used for fine movements, e.g. when writing. It has been suggested that the long head fascicle is employed when sustained force generation is demanded, or when there is a need for a synergistic control of the shoulder and elbow or both.
The lateral head is used for movements requiring occasional high-intensity force, while the medial fascicle enables more precise, low-force movements. With its origin on the scapula, the long head acts on the shoulder joint and is involved in retroversion and adduction of the arm, it helps stabilise the shoulder joint at the top of the humerus. The triceps can be worked through either isolation or compound elbow extension movements and can contract statically to keep the arm straightened against resistance. Isolation movements include cable push-downs, lying triceps extensions and arm extensions behind the back. Examples of compound elbow extension include pressing movements like the push up, bench press, close grip bench press, military press and dips. A closer grip targets the triceps more than wider grip movements. Static contraction movements include pullovers, straight-arm pulldowns and bent-over lateral raises, which are used to build the deltoids and latissimus dorsi. Ruptures of the triceps muscle are rare, only occur in anabolic steroid users.
The triceps reflex, elicited by hitting the triceps, is used to test the function of the nerves of the arm. This tests spinal nerves C6 and C7, predominately C7, it is sometimes called a three-headed muscle, because there are three bundles of muscles, each of different origins, joining together at the elbow. Though a named muscle, the triceps surae, is found on the lower leg, the triceps brachii is called the triceps; the plural form of triceps was tricipites, a form not in general use today. In the horse, 84%, 15%, 3% of the total triceps muscle weight correspond to the long and medial heads, respectively. Many mammals, such as dogs and pigs, have a fourth head, the accessory head, it lies between the medial heads. In humans, the anconeus is sometimes loosely called "the fourth head of the triceps brachii". Illustration: upper-body/triceps-brachii from The Department of Radiology at the University of Washington Anatomy photo:06:11-0100 at the SUNY Downstate Medical Center Photo at Ithaca College Muscles/TricepsBrachii at exrx.net
In human anatomy, the axillary vein is a large blood vessel that conveys blood from the lateral aspect of the thorax and upper limb toward the heart. There is one axillary vein on each side of the body, its origin is at a continuation of the brachial vein. This large vein is formed by the basilic vein. At its terminal part, it is joined by the cephalic vein. Other tributaries include the subscapular vein, circumflex humeral vein, lateral thoracic vein and thoraco-acromial vein, it terminates at the lateral margin of the first rib. It is accompanied along its course by a named artery, the axillary artery. Gray's s149 lesson3axillaryart&vein at The Anatomy Lesson by Wesley Norman