A&P II ch. 20 part 1

lymph collecting vessels

- from the lymph capillaries, lymph flows into larger lymph collecting vessels that lead toward the bodies trunk. -Like veins these possess valves which are located very close together and bulge noticeably. As a result, large lymph collecting vessels resemble a string of beads. Pressures within them are very low and the valves are required to prevent the backflow of lymph and to maintain normal lymph flow towards they thoracic cavity. -*superficial lymph collecting vessels* - are located in the subcutanous layer, deep to the skin in the areolar tissues of the mucous membranes lining the digest, respiratory, urinary, and reproductive tracts; and the areolar tissues of the serous membranes lining the pleural, pericardial, and peritoneal membranes. -*deep lymph collecting vessels*- accompany the deep arteries and veins supplying skeletal muscles and other organs of the neck, limbs, trunk and the walls of visceral organs

lymph ducts

- the lymph trunks merge to form the two largest lymphatic vessels called the: 1. right lymphatic duct and 2. thoracic duct.

lymph trunks

- the superficial and deep lymph collecting vessels converge to form larger vessels known as lymphatic trunks and are named by the areas of body they drain; 1.) the *jugular trunks*- located in the neck and drain the head. 2.) *subclavian trunks* located in the shoulders and drain the arms. 3.) *bronchomediastinal trunks* located in the chest and drain the thoracic cavity and lungs. 4.) *lumber trunk* located in the abdomen and drains the walls of the digestive organs. - blockage of the lumbar trunks or subclavian trunks by a filarial worm, such as Wuchereria boncrofti, causes severe lymphedema known as *Elephantiasis*

lymph capillaries

-present in almost every tissue and organ in the body; are believed to be as abundant as blood capillaries. -they are absent, however, in areas of the body that lack a blood supply, such as the cornea of the eye, and are also absent from the central nervous system and bone marrow. -they differ from blood capillaries in that they: 1.) are blind-end tubes 2.) have larger diameters with lower resistance and pressure, 3.) have thinner walls that are more permeable and 4.) typically have a flattened or irregular shaped lumen. - they are lined by simple squamous epithelium, the basal lamina is incomplete or absent. Furthermore, the endothelial cells overlap forming a type of one-way valve called a *mini-valve*. The mini-valve permitt the entry of fluids and solutes such as proteins as well as viruses, bacteria and cell debris, but prevent their return to the intercellular spaces.

3 functions of the lymphatic system

1. drains 2. houses 3. absorbs

included in the lymphatic system

1. vessels 2. cells 3. tissues 4 organs responsible for defending the body against both enviromental hazzards (such as various pathogens) and internal threats (such as cancer cells)

thoracic duct

ascends along the left side of the vertebral column, collecting lymph from the left bronchomediastinal trunk, the left subclavian trunk, the left jugular trunk. At the base of the thoracic duct is an enlarged sac-like chamber called the *cisterna chyli* which receives lymph from the lumbar trunk and interstinal trunk. The thoracic duct drains the left side of the head, the left arm, the left shoulder, and the left side of the thoracic cavity, all of the abdomen, pelvic region and both legs. It empties into the left subclavian vein.

lymph vessels

carry lymph from the peripheral tissues to the venous system. The lymphatic network begins with lymphatic capillaries, which merge to form progressively larger vessels as they make their way towards circulation 1. lymph capillaries 2. lymph collecting vessels 3. lymph trunks 4. lymph ducts

right lymphatic duct

forms from the merger of the right jugular trunk, the right subclavian trunk and the right bronchomediastinal trunk. The right lymphatic duct drains the right side of the head, right arm, right shoulder, and right side of the thoracic cavity. The right lymphatic duct empties into the right subclavian vein.

absorbs

the lymphatic system absorbs digested fats from the intestine by specialized lymph vessels called *lacteals*. The fatty lymph is known as *chyle*

drains

the lymphatic system drains excess interstitial fluid from the interstitial space and transports it to the bloodstream. Once this tissue fluid enters into the lymphatic vessels, it is no longer called interstitial fluid; it is now called *lymph*. Any blockage in the normal drainage of lymph produces: *lymphedema*

houses

the lymphatic system houses the phagocytic cells and lymphocytes that clean the tissue fluid before it is dumped into circulation