1. A. Tonsils B. Lymph Nodes C. Thymus D. Lymphatic Vessels E
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24. The Lymphatic System Answers to Pre-Lab Assignments Pre-Lab Activity 1: 1. a. tonsils b. lymph nodes c. thymus d. lymphatic vessels e. spleen 2. a. 2 b. 5 c. 3 d. 1 e. 4 Pre-Lab Activity 2: 1. a. spleen b. lymph node c. tonsil d. tonsil e. lymph node Pre-Lab Activity 3: 1. lymph 2. 4 1 3 2 Pre-Lab Activity 4: 1. hCG 2. a. antigen b. primary antibody c. secondary antibody d. enzyme substrate Answers to Activity Questions Activity 1 Making Connections: The Lymphatic System Lymphatic Structure Description/Function Connections to Things I Have Already Learned Lymph collecting ves- Transport lymph to- Like veins, contain three tunics and sels ward venous circula- valves; lymph transport is dependent tion. on milking action of skeletal muscles and pressure changes within thorax. Lymph trunks Receive lymph from Several lymph collecting vessels fuse to • Jugular collecting vessels and form a lymph trunk as they transport • Subclavian empty it into the lymph toward the heart; an arterial • Bronchomedi- lymph ducts. trunk gives rise to smaller arteries that astinal carry blood away from the heart. • Intestinal • Lumbar Lymph ducts The two largest lym- Thoracic duct empties into left subcla- • Thoracic duct phatic structures that vian vein; right lymphatic duct empties • Right lymphat- empty lymph into ve- into right subclavian vein (both at junc- ic duct nous circulation. tion of subclavian and internal jugular veins). Lymph nodes Small, kidney bean– Each lymph node has an outer cortex • Cervical shaped organs associ- and an inner medulla like the adrenal • Axillary ated with lymph col- gland. • Inguinal lecting vessels; clean lymph; biological filter; clusters found in neck, armpit, and groin. Lymphatic Structure Description/Function Connections to Things I Have Already Learned Spleen Largest lymphoid or- Along with the liver, the spleen phago- gan; located posterior cytizes old, damaged red blood cells. and lateral to stomach in left hypochondriac region; filters blood, launches immune re- sponse; red pulp: many RBCs; white pulp: many lympho- cytes. Thymus Produces hormones Also classified as an endocrine organ; (thymosins) that stim- atrophies with old age ulate development of white blood cells. Mucosa-associated Lymphatic nodules A nodule = cluster of B cells surrounded •lymphoid tissue (follicles) associated by macrophages and T cells • Tonsils with mucosal mem- • Pharyngeal branes • Palatine • Lingual • Located in na- • Peyer’s patch- sopharynx es • Located in the oropharynx • Appendix • Located at the base of the tongue • Associated with the epithelium of the small intestine • An evagination of the cecum Activity 2 1. a. Which white blood cell type is most prominent in the germinal centers, and what is its function? Rapidly dividing B cells (they are lymphocytes that produce antibodies) b. Which cell types are most prominent in the medullary cords, and what is their function? Macrophages function in phagocytosis and also serve as antigen-presenting cells (they “present” antigens to T cells). d. What is the physiological significance of each lymph node having few- er efferent vessels than afferent vessels? Lymph drains from the lymph node more slowly than it enters, allowing more time for the lymph to be cleaned. 2. a. What is the purpose of the tonsillar crypts? to trap patho- gens ____ 3. a. Even though white pulp is not white in color, why is this tissue called white pulp? It contains abundant white blood cells. How do the functions of red pulp and white pulp relate to their structures? The white pulp, composed primarily of lymphocytes, performs the immune functions of the spleen, whereas the red pulp contains blood- filled sinus- es. Macrophages remove pathogens, debris, and worn-out red blood cells as blood flows through the sinuses. _______________________________________ Activity 3 2. Why does excess tissue fluid accumulate around body cells? Hydro- static pressure drives more fluid out of the capillary than osmotic pressure pulls into capillary.______ What happens to excess tissue fluid? It is taken up by lymphatic capillar- ies.____ When excess tissue fluid enters a lymphatic capillary, it becomes lymph . Lymphatic capillaries fuse to become larger lymphatic collecting ves- sels._______ 3. What is the purpose of the lymph nodes? to filter and clean out lymph as it passes through 4. a. Jugular trunks Drain head and neck. b. Subclavian trunks Drain the upper limbs. c. Bronchomediastinal trunks Drain thoracic wall, lung, and heart. d. Intestinal trunk Drains stomach, intestines, spleen, pancreas, and liver. e. Lumbar trunks Drain abdominal wall, pelvis, and low- er limbs. 5. Which areas of the body are drained by the: a. right lymphatic duct? right side of head, neck, shoulder, thorax, and right up per limb b. thoracic duct? left side of head, neck, shoulder, thorax, and left up- per limb along with abdomen and lower limbs 6. c. The thoracic duct begins at the level of vertebra L2 as an en- larged sac called the cis terna chyli. Which lymph trunks unite to form the cisterna chyli? the lumbar trunks and the intestinal trunk _____________________________________ d. The thoracic duct ascends from the cisterna chyli along the left side of the vertebral column next to the aorta and pierces the diaphragm. At the base of the heart, the thoracic duct unites with the left subclavian vein. From which three lymph trunks does the thoracic duct receive lymph at the level of the clavicle? bronchomediastinal, subclavian, and jugular trunks ________________________________ 7. Lymph enters a lymphatic capillary at a capillary bed. It then drains into larger lymph collecting vessels . Positioned along them are struc- tures called lymph nodes that function to filter lymph . Lymph collect- ing vessels unite to form lymph trunks , which then fuse to form one of two lymph ducts . The thoracic duct drains most of the body, where- as the right lymphatic duct drains the right side of the head and neck, right shoulder, and right upper extremity. Lymph ducts return lymph to the bloodstream at the junction of the internal jugular vein and the subcla- vian vein on each side of the body. Answers to Post-Lab Assignments PART I. Check Your Understanding Activity 1: Exploring the Organs of the Lymphatic System 1. A lymph node filters lymph ; the spleen filters blood . 2. Lymph nodes are clustered in which three regions of the body? cervical, axillary, inguinal 3. What happens to the thymus as individuals age? It atrophies, be- coming largely adipose tissue. 4. Name the unpaired tonsil located in the nasopharynx. pharyngeal tonsils (adenoids) 5. Name the lymphoid tissue that extends from the cecum. appen- dix 6. What is MALT? mucosa-associated lymphoid tissue Activity 2: Examining the Histology of a Lymph Node, a Tonsil, and the Spleen 1. Identify the organ in the accompanying photomicrograph and name the indicated structures. Organ: lymph node a. capsule b. follicle c. medullary sinus d. germinal center e. medullary cord 2. How are a lymph node and a tonsil different with respect to structure? A lymph node has both afferent and efferent vessels, whereas a tonsil lacks afferent vessels. _______________________________________________________________ ______ 3. Identify the organ in the accompanying photomicrograph and name the indicated structures: Organ: spleen a. white pulp b. red pulp c. trabeculae Activity 3: Tracing the Flow of Lymph through the Body 1. The smallest of the lymphatic vessels, lymphatic capillaries , are blind-ended sacs that take in excess tissue fluid at capillary beds and transport it to larger lymph collecting vessels . 2. Name the four paired lymph trunks. lumbar, bronchomediastinal, subclavian, and jugular _______________________________________________________________ ________ 3. The thoracic duct begins as an enlarged sac called the cisternae chyli . 4. The lymph ducts return lymph to the venous circulation at the junc- tion of which two veins on •either side of the body? internal jugular veins and subclavian veins __ Activity 4: Using a Pregnancy Test to Demonstrate Antigen-Antibody Reac- tions 1. In an ELISA, antigen a. the primary antibody binds to which molecule? secondary antibody b. the enzyme is attached to which mole- cule? substrate c. the final step is the addition of which molecule? primary antibody d. the secondary antibody binds to which molecule? 2. In a positive pregnancy test, which antigen is detected in urine? hCG PART II. Putting It All Together A. Review Questions Answer the following questions using your lecture notes, your textbook, and your lab notes. 1. To which two organ systems does the thymus belong? endocrine and lymphatic 2. After Brian suffered a ruptured spleen in an automobile crash, a sur- geon removed it to stop internal bleeding. Why can Brian survive without his spleen? Other organs perform the same function as the spleen. For exam- ple, the spleen and liver phagocytize old, damaged red blood cells. The spleen and skin serve as blood reservoirs. 3. The third line of defense is specific immunity, which consists of two different mechanisms: antibody -mediated immunity carried out by B cells and cell -mediated immunity carried out by T cells. 4. Lacteals are specialized capillaries found in the small intestine that ab- sorb dietary fat. Fats enter the lacteal as lipoprotein complexes called chylo- microns, which are then transported via lymphatic vessels to the blood- stream. Trace the pathway of a chylomicron from the point at which it enters a lacteal until it reaches a cell in the rectus femoris muscle. lacteal → lymphatic collecting ves- sel → lymph trunk → thoracic duct → left subclavian vein → left brachiocephalic vein → -superior vena cava → right atrium → right ventricle → pulmonary trunk → pulmonary artery → lungs → pulmonary vein → left atrium _______________________ → left ventricle → -ascending aorta → aortic arch → -thoracic aorta → abdominal» aorta → common iliac artery → external iliac artery → femoral ar- tery → arteriole → capillary bed → cell in the rectus femoris 5.