Lymphatic System Anatomy PDF

Lymphatic System By Dr: Joseph Amin Ass. Prof of anatomy & embryology Faculty of medicine-Zagazig university Lymphatic system is a drainage system accessory to venous system Functions of lymphatic system: 1- Drainage the excess tissue fluid. 2- Absorption of fats from th...

Lymphatic System By Dr: Joseph Amin Ass. Prof of anatomy & embryology Faculty of medicine-Zagazig university Lymphatic system is a drainage system accessory to venous system Functions of lymphatic system: 1- Drainage the excess tissue fluid. 2- Absorption of fats from the intestine 3- Immunological functions 4- Circulatory homeostasis  Components of Lymphatic system Extensive network of vessels through which lymph circulates 1- Lymph (fluid) 2- Lymph capillaries, vessels, trunks and ducts 3- Lymphoid organs - lymph nodes - spleen - thymus 4- Epithelio-lymphoid tissues - Bone marrow  Lymph About 30 L of fluid are filtered every 24 at the arterial end of capillaries into the interstitial space, from which 26-28 L are reabsorbed at the venous end. The remaining 2-4 L (10-15%) are drained by lymphatic capillaries. Thus, Lymph is the excess tissue fluid that enters the lymph capillaries Lymph is usually clear fluid similar to plasma N.B lymph from intestine is milky white as it contains absorbed fat droplets. The lymph from intestine is called “ chyle” (chylos in greek = juice) Lymph carries leaked plasma proteins, fat droplets, lymphocytes and plasma cells and particles like cell debris and bacteria.  Lymph capillaries Lymph capillaries are similar to blood capillaries but differ in that 1- Begin blindly in the intercellular spaces 2- Wider lumen 3- More permeable 4- They contain valves Lymph N.B Lymph capillaries in the intestinal villi are called “ Lacteals” as they carry the milky chyle  Lymph vessels  Lymph capillaries unit forming lymph vessels.  Lymph vessels are thin-walled resembling small veins.  They have numerus valves allowing only unidirectional flow. The valves lies at closer intervals than that of veins giving the vessels a beaded appearance  The flow in lymph vessels is interrupted by a series of lymph nodes.  They may be superficial or deep  Small lymph vessels collect into progressively larger ones that converge to form 6 lymph trunks.  The lymph trunks end in 2 collecting ducts.  The collecting ducts open into the angels between subclavian & internal jugular veins Jugular trunk Subclavian trunk Broncho-mediastinal trunk Right lymphatic Duct Thoracic Duct  Lymph Trunks 1- jugular drain the head and neck 2- subclavian drain the upper limb 3- broncho-mediastinal drain the thoracic cavity 4- intercostal trunk drain the thoracic wall 5- intestinal trunk drain the intestine 6- lumbar trunk drain the lower limb  Lymph Ducts 1- Thoracic duct - 45 cm in length - Start as the continuation of cisterna chyli - It drains All the body EXCEPT Right ½ of H&N Right UL Right ½ of thoracic cavity - It ends in the angle between left Subclavian and Left IJV veins 2- Right lymphatic duct - It drains Right ½ of H&N Right UL Right ½ of thoracic cavity - It ends in the angle between left Subclavian and Left IJV veins The factors responsible for flow of lymph are: 1- Filtration (hydrostatic) pressure 2- Valves 3- Contraction of smooth muscles in the wall of vessels 4- Contraction of surrounding muscles 5- Pulsation of surrounding arteries 5- Negative intrathoracic pressure caused by respiratory movements 6- Negative pressure in brachiocephalic veins  Lymphatic tissues Lymphatic tissue Framework of reticular fibers + Lymphocytes and plasma cells Mucosa associated lymphatic tissue (MALT) Peyer’s patches, palatine tonsil, pharyngeal tonsil, lingual tonsil N.B Lymphatic nodule circumscribed lymphatic tissue  Lymphoid Organs Encapsulated lymphatic tissues. They are classified into 1- Primary lymphoid organs: produce lymphocytes e.g. Bone marrow & Thymus gland 2- Secondary lymphoid organs: activate lymphocytes, initiate immune response e.g. lymph nodes, spleen  Lymph Nodes  Oval or bean-shaped, 0.1- 2.5 cm in length.  The lymph vessels generally pass at least through one LN  There about 450 LNs in the body (70 in H&N, 100 in thorax, 250 in abdomen & pelvis.  They can be either superficial (usually arranged around veins) or deep (usually arranged around arteries)  LNs tend to be in groups or clusters. The main groups are 1- Cervical 2- Axillary 3- Mediastinal 4- Aortic 5- Iliac 6-Inguinal  N.B: LN are the only lymphoid organ that has afferent and efferent lymph vessels Functions of LN: 1-Filtration of the lymph: lymph is only filtrated in LN, so lymphatic system is not closed system 2-Activation of lymphocytes and immunological logical response