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Home , Cisterna chyli, Lacteal, Lymphatic system, Red pulp, Right lymphatic duct, Spleen

24. The Answers to Pre-Lab Assignments Pre-Lab Activity 1: 1. a. b. nodes c. d. lymphatic vessels e. 2. a. 2 b. 5 c. 3 d. 1 e. 4

Pre-Lab Activity 2: 1. a. spleen b. c. d. tonsil e. lymph node

Pre-Lab Activity 3: 1. lymph 2. 4 1 3 2

Pre-Lab Activity 4: 1. hCG 2. a. b. primary 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 , contain three tunics and sels ward venous circula- valves; lymph transport is dependent tion. on milking action of skeletal muscles and pressure changes within .

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 ; an arterial • Bronchomedi- lymph ducts. trunk gives rise to smaller that astinal carry away from the heart. • Intestinal • Lumbar

Lymph ducts The two largest lym- Thoracic duct empties into left subcla- • Thoracic duct phatic structures that vian ; empties • Right lymphat- empty lymph into ve- into right (both at junc- ic duct nous circulation. tion of subclavian and internal jugular veins).

Lymph nodes Small, 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 .

Lymphatic Structure Description/Function Connections to Things I Have Already Learned Spleen Largest lymphoid or- Along with the , the spleen phago- gan; located posterior cytizes old, damaged red blood cells. and lateral to in left hypochondriac region; filters blood, launches immune re- sponse; : many RBCs; : many lympho- cytes.

Thymus Produces hormones Also classified as an endocrine ; (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 and T cells • Tonsils with mucosal mem- • Pharyngeal branes • Palatine • Lingual • Located in na- • Peyer’s patch- sopharynx es • Located in the oropharynx • • Located at the base of the • Associated with the of the • An evagination of the cecum

Activity 2 1. a. Which white type is most prominent in the germinal centers, and what is its function? Rapidly dividing B cells (they are that produce ) 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” 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 ? 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 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 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, , and heart. d. Intestinal trunk Drains stomach, intestines, spleen, , 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 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 ? 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 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 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 . 4. Name the unpaired tonsil located in the nasopharynx. pharyngeal tonsils () 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. 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 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 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. are specialized capillaries found in the small intestine that ab- sorb dietary . enter the as complexes called chylo- microns, which are then transported via lymphatic vessels to the blood- stream. Trace the pathway of a 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 → → pulmonary vein → left atrium ______→ left ventricle → -ascending aorta → aortic arch → -thoracic aorta → abdominal» aorta → common iliac artery → external iliac artery → femoral ar- tery → → capillary bed → cell in the rectus femoris 5. Compare and contrast the following lymphoid organs by completing each of the following charts. Characteristics Unique Characteristics Shared Characteristics Unique to a Lymph Node by Both a Lymph Node to a Tonsil and a Tonsil Contains afferent and Contains many lympho- Contains crypts efferent vessels cytes and macrophages

Surrounded by a capsule Lymphoid organs Classified as MALT

Filters lymph Rid the body of patho- Aggregated near gens

Characteristics Unique Characteristics Shared Characteristics Unique to to the Thymus by Both the Thymus the Spleen and Spleen Atrophies in old age to Function in immunity Largest lymphoid organ become mostly adipose

T-lymphocytes undergo Trabeculae subdivide Contains red pulp and maturation here and each organ white pulp then later migrate to lymph Produce hormones Contain abundant lym- Hematopoiesis in fetus called thymosins phocytes and macro- phages