Human Anatomy - Lecture Notes - Savchuk O.I. 2017

Lymph. Structure of the Lymphatic System

Lymph is a yellowish fluid that flows through lymphatic capillaries and vessels. It consists of lymph plasma and formed elements. In terms of chemical composition, lymph plasma is similar to Blood Plasma but contains less protein. Lymph plasma also contains neutral fats, simple sugars, and solutions of mineral salts КаСl, На₂Сl₃, as well as various compounds containing calcium, magnesium, and iron.

The formed elements of lymph include lymphocytes (98%), monocytes, and a small number of Other types of leukocytes. Erythrocytes are rarely found.

Lymph is formed in the lymphatic capillaries of Tissues and Organs by absorbing interstitial fluid. From the capillaries, lymph flows into peripheral Lymphatic vessels, then into Lymph Nodes, then into large lymphatic vessels, and finally empties into the bloodstream. Consequently, the composition of lymph changes. For instance, lymph draining from the gastrointestinal tract is rich in fats, Proteins, and sugars. Lymph passing through lymph nodes becomes enriched with granulocytes. Therefore, a distinction is made between peripheral lymph (before reaching the lymph nodes), intermediate lymph (after passing through the lymph nodes), and central lymph (lymph of the thoracic and right lymphatic ducts).

The process of Lymph formation is closely linked to the Movement of Water from the blood into the intercellular space and The formation of interstitial fluid. Approximately 1.5 liters of lymph are produced in a human daily.

Lymphatic vessels.

The Lymphatic system is part of The Vascular System. Lymph moves toward the large Veins OF THE neck, where it enters the venous blood. The lymphatic system is a branching network of vessels with lymph nodes situated along the course of Blood Vessels.

The lymphatic system ensures the absorption of water from tissues along with dissolved substances (proteins, fats, Bacteria, tissue breakdown products) that are not absorbed by blood capillaries. In addition, lymphogenesis occurs within it, which is of great importance for immunological reactions.

The lymphatic system begins with blind-ended endothelial tubes—capillaries—that form networks within organs. Capillaries are present in all organs except the Brain AND SPINAL cord, Eyeball, Inner ear, mucous membranes, Cartilage, splenic parenchyma, Bone Marrow, and Placenta.

Lymphatic vessels, which possess numerous Valves, originate from the capillaries. These valves ensure the unidirectional flow of lymph. Lymphatic vessels draining from organs travel to regional lymph nodes.

The lymphatic system consists of:

1) blind-ended lymphatic capillaries that form a network within organs;

2) intraorgan vessels that emerge from the lymphocapillary network and form their own network;

3) efferent vessels that exit the organ and are interrupted along their path by lymph nodes;

4) large lymphatic vessels that empty into lymphatic trunks.

The following trunks are distinguished: a) lumbar, b) intestinal, c) subclavian, d) jugular, and e) bronchomediastinal. These trunks merge into two lymphatic ducts that empty into the large veins of the neck.

The Thoracic duct (ductus thoracicus)

It is formed in the Abdominal cavity by the fusion of the two lumbar trunks. It passes through the Diaphragm alongside the aorta, lies in the posterior Mediastinum, ascends into the neck region, and empties into the left venous angle. This duct drains lymph from the lower limbs, pelvic organs and walls, the abdomen, the left upper limb, and the left side of the HEAD and Neck.

The Right lymphatic duct (ductus lymphaticus dexter)

Measuring 10-12 mm in length, it is formed by the fusion of the right bronchomediastinal, subclavian, and jugular trunks. This duct drains lymph from the right side of the head, neck, thoracic cavity, and right upper limb, and empties into the right subclavian vein or the right venous angle.

Lymphoid organs.

Organs in which lymphocytes develop and mature are called lymphoid organs, and the tissue that makes up these organs is known as lymphoid tissue. Lymphoid organs include the bone marrow, Thymus, lymph nodes, and Spleen.

The bone marrow and thymus are the primary (central) Hematopoietic organs. The bone marrow contains stem Cells that divide to become Blood Cells: erythrocytes, leukocytes, and platelets. These stem cells also give rise to cells of The Immune System: lymphocytes and plasma cells.

The immune system integrates organs and tissues that protect the body against genetically foreign cells or substances, whether produced within the body or introduced from the outside. The Organs of the immune system produce immunocompetent cells that provide Immunity—resistance to substances with antigenic properties. The primary organ of the immune system is the thymus, where T-lymphocytes are formed.

Lymph nodes are structures of various shapes (round, oval, bean-shaped), ranging in size from 1 to 20 mm, which participate in the body's defense reactions and regulate lymph flow. On one side, the lymph node has a depression called the hilum, through which Arteries and nerves enter and veins exit. The node is covered by a capsule from which trabeculae extend. The parenchyma of the node consists of a cortex and a medulla.

Spleen (lien, splen)

It belongs to the lymphoid organs. It serves as a "graveyard" for erythrocytes, as this is where their breakdown occurs. Along with The Liver and Skin, the spleen can store a significant amount of blood (acting as a blood reservoir).

The spleen is located in the abdominal cavity in the left hypochondrium at the level of the IX - XI Ribs. It has two surfaces: diaphragmatic and visceral. The Stomach, left Kidney, and tail of the Pancreas lie adjacent to it. It features the splenic hilum, which is the site of entry and exit for Vessels and nerves. It is covered by the Peritoneum, making it intraperitoneal. It has a capsule from which septa, or trabeculae, extend. Between the trabeculae lies the splenic pulp. It contains a significant number of erythrocytes and 48 lymphocytes. Red and white pulp are distinguished. The red pulp contains erythrocytes, leukocytes, and macrophages. The white pulp is formed by lymphoid nodules consisting of lymphocytes and other lymphoid tissue cells.

Lymphatic vessels and nodes of specific body regions.

Lymphatic Vessels of the trunk, head, and limbs are divided into superficial and deep. The boundary between them is the deep Fascia of the respective region. Thus, superficial vessels include those of the skin and subcutaneous tissue, while deep vessels include all others lying beneath the fascia. Deep lymphatic vessels travel within neurovascular bundles and drain into the major vessels of the region, which then course to regional lymph nodes.    

Lymphatic vessels and nodes of the lower limbs.

The following nodes are distinguished in the lower limb:

1) popliteal lymph nodes – lymph drains here from the lateral margin of the FOOT and the inferolateral surface of the leg.

2) inguinal lymph nodes (superficial and deep) – they collect lymph from the rest of the lower limb, as well as from the gluteal region, anterior abdominal wall, and external genitalia.

Lymphatic vessels and nodes of the pelvis

The following nodes are distinguished in the pelvic cavity: 1) common iliac, 2) external iliac, 3) internal iliac, 4) sacral. All these nodes are located along blood vessels and drain lymph from the pelvic organs.

Lymphatic vessels and nodes of the abdominal cavity.

From the upper PARTS OF THE anterior abdominal wall, lymph drains into the axillary nodes, and from the lower parts, into the inguinal nodes.

In the abdominal cavity, a distinction is made between parietal nodes, located around the aorta and INFERIOR VENA CAVA, and visceral nodes, which are situated along the Branches of the celiac trunk and mesenteric arteries, within the mesentery of the small and large intestines.

The Small Intestine has a specialized system of lymphatic vessels called lacteals, because they transport fat, which gives them the appearance of a milky emulsion.

From the mesenteric nodes, lymph flows to the lumbar nodes, and from there into the left lumbar trunk and the thoracic duct.

Lymphatic vessels of the thoracic cavity.

Parietal and visceral lymph nodes are distinguished.

Parietal nodes are located on the posterior wall of the thoracic cavity (prevertebral, intercostal) and on the anterior wall (mammary, parasternal, diaphragmatic).

Visceral nodes form 3 groups: anterior mediastinal, posterior mediastinal, and tracheobronchial. They collect lymph from the organs of the anterior and posterior mediastinum.

Lymphatic vessels and nodes of the upper limbs.

They are divided into superficial and deep.

Deep vessels collect lymph from bones, joints, Muscles, and fasciae, carrying it to the axillary lymph nodes.

Superficial lymphatic vessels collect lymph from the skin and subcutaneous tissue, carrying it to the cubital and axillary lymph nodes. The efferent vessels of the axillary nodes form the right and left subclavian trunks, of which the left drains into the thoracic duct, and the right drains into the right lymphatic duct.

Lymphatic vessels and nodes of the head and neck

Superficial and deep lymphatic vessels of the head and neck run along blood vessels, carrying lymph in a superior-to-inferior direction.

Occipital, posterior auricular, and superficial cervical lymph nodes are distinguished. Lymph from the soft Tissues of the face drains into the buccal, parotid, submental, and submandibular lymph nodes.

Lymph from the Gums, Teeth, Tongue, and the mucous membranes of the oral and nasal cavities drains into the submental and submandibular lymph nodes.

Lymph from the Pharynx, Larynx, Esophagus, Trachea, and Thyroid Gland drains into the deep cervical lymph nodes.

These nodes lie along the neurovascular bundle of the neck. In the lower part of the neck, the efferent vessels merge to form the right and left jugular trunks. The left trunk drains into the thoracic duct, while the right drains into the right lymphatic duct.

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