BIO142: Unit 3 and 4

• Describe the two main components of the lymphatic system.


  1) lymphatic vessels

  2) lymphatic tissues & organs
• Explain the three basic functions of the lymphatic system.


  1) regulation of interstitial fluid volume (returns water back to the blood)

  2) absorption of dietary fats

  3) immune functions (filter pathogens from lymph)
• Define lymph.


  the watery liquid located w/in lymphatic vessels; composition is similar to that of interstitial fluid but w/ fewer proteins
• Describe characteristics of lymph with regards to

  a. its location --> w/in lymphatic vessels

  b. its production --> formed when interstitial fluid is collected in lymphatic vessels

  c. its content --> water, WBCs, proteins, salts, glucose, fats

  d. its movement into lymphatic capillaries --> the smallest lymphatic vessels that receive lymph from the blood
• Describe the regions that are drained by the thoracic duct and the right lymphatic duct.


  cisterna chyli, trunks from left side of upper body, lower body --> thoracic duct

  trunks from the right side of upper body --> right lymphatic duct
• Define cisterna chyli and identify its location.

  the large, swollen-looking lymphatic vessel located in the abdomen that the intestinal & lumbar trunks drain into; fluid drains from here into the thoracic duct
• Describe the structure and function of lymphatic vessels.


  blind-ended (one-way) vessels that transport lymph from the interstitial fluid to the blood; cells of vessels are not tightly joined & allow fluid to leak out
• Compare lymphatic vessels and small veins.

  lymphatic vessels --> blind-ended (one way), cells are loosely compacted & can flap open & closed, carry lymph

  blood capillaries --> 2 way system, cells are tightly packed, carry blood
• Define lymphedema, explain how it occurs, and give one cause of lymphedema.

  the accumulation of excess interstitial fluid in a particular area of the body causing it to enlarge; generally caused by the removal of lymphatic vessels during surgery or due to the blockage of a vessel by a pathogen, making it difficult for lymphatic vessels to transport lymph back to the CV system
• Describe the structure and function of lymphatic capillaries.

  transport lymph from the interstitial fluid to the blood; form web-like networks that surround blood capillary beds; cells of capillaries are not tightly joined & allow fluid to leak out
• Define lacteals.


  a specialized lymphatic capillary in a interstitial villus that receives absorbed fats in addition to lymph
• Describe lymphoid tissue and the main cell types found in this tissue.

  the reticular tissue found in lymphoid organs composed of loose CT, specialized cells, & reticular fibers; fibers interweave to form "nets" that trap pathogens; cell types found in lymphoid tissue: lymphocytes, phagocytes, reticular cells
• Describe the structure and location of MALT.

  mucosa-associated lymphatic tissue

  loosely organized clusters of lymphoid tissue located along mucous membranes; located throughout the GI tract, respiratory passages, & the genitourinary tract; mostly contains B & T cells
• Define Peyer's patches.


  a specialized cluster of MALT located in the last portion of the small intestine (the ileum) aka aggregated lymphoid nodules; defend against the bacteria found in the large intestine & prevent them from entering the small intestine
• Name the three main groups of tonsils and state their location.

  specialized clusters of lymphatic tissue located around the oral & nasal cavities

  1) pharyngeal tonsil (posterior nasal cavity) (aka adenoids)

  2) palatine tonsils (posterolateral oral cavity)

  3) lingual tonsil (at base of tongue
• Identify the location of the tonsils on a figure.

  A = lingual

  B = pharyngeal

  C = palatine

  
• Describe the structure and function of the appendix.

  a blind-ended, worm-shaped tube/specialized cluster of MALT that juts out from the large intestine; functions in defending against bacteria in the large intestine, especially those that may be pathogenic
• Explain appendicitis and its complications.

  the inflammation of the appendix; since it is a blind-end organ, it can not expand very much and can burst, spilling bacteria into the abdominopelvic cavity, and may cause internal bleeding & infection
• Define lymph nodes, and describe their location, structure, and function.


  small, bean-shaped clusters of lymphatic tissue located along lymphatic vessels throughout the body; function is to filter lymph; especially prominent in the axillary, cervical, inguinal, & mesenteric regions; composed of an external CT capsule surrounding a network of reticular fibers filled w/ macrophages, lymphocytes, & dendritic cells; the outer cortex consists of B-cell rich lymphoid follicles & divided by trabeculae; inner medulla has macrophages, & mature B cells called medullary cords; between the 2 layers are T cells
• State the location and function of the spleen.

  the large lymphoid organ located in the left upper quadrant of the abdominopelvic cavity that filters blood & processes old erythrocytes
• Distinguish between the functions of the red pulp and white pulp of the spleen.

  red pulp = contains macrophages that destroy old erythrocytes

  white pulp = filters pathogens from the blood & contains leukocytes
• State the location of the thymus, and briefly explain the size and function of the thymus in children and in adults.

  an endocrine gland located in the interior mediastinum that houses developing T lymphocytes & secretes paracrines that stimulate their maturation; is very large & active in infants & children, reaches maximum size around age 12-14, then begins to atrophy as the tissue is replaced w/ fat, thus decreasing the production of T cells
• Describe the three lines of defense against pathogens brought about by the immune system.

  1) first line of defense = cutaneous & mucous membranes

  2) second line of defense = innate immunity

  3) third line of defense = adaptive immunity
• Describe & compare the two types of immunity.

  1) innate immunity = responds to all pathogens in the same way; consists of antimicrobial proteins & certain cells w/in the bloodstream; responds quickly & is dominant for first 24 hours after exposure

  2) adaptive immunity = consists of cells & proteins that must bind to specific antigens in order to become activated; consists of cell-mediated immunity (T cells) & antibody-mediated immunity (B cells & antibodies); responds slower: takes 3-5 days to mount a response; has immunological memory to create a faster future response
• Explain the role of skin and mucosal membranes as the first line of defense.

  they provide a continuous physical barrier to block the entry of potential pathogens into the body; they also produce numerous protective secretions including: sebum, mucus, stomach acid, & defensins; normal flora also protect us by competing for space & resources, & secreting substances to kill and deter growth of pathogens
• Briefly describe some mechanisms by which pathogens can evade surface barriers.

  1) collagenase-producing bacteria --> produce enzymes called collagenase that degrade the protein collagen & allow them to access deeper tissues

  2) phagocytosis-resistant fungi --> have thick walls that cannot be ingested by phagocytes, can actually survive inside phagocytes --> macrophages spread disease as they travel through the blood & lymph

  3) acid-tolerant pathogens --> certain pathogens tolerate or prefer an acidic environment so the acidic secretions of the body have no effect on them & will survive & spread disease
• Briefly describe the role of the following cells that form the second and third lines of defense of the innate and adaptive immune systems:

  1) Agranulocytes = lack visible granules

  a) B lymohocyes = antibody mediated arm of adaptive immunity

  b) T lymphocytes = cell mediated arm of adaptive immunity

  c) monocytes = mature into macrophages

  2) Granulocytes = contain cytoplasmic granules

  a) neutrophils = ingests damaged cells & bacteria

  b) eosinophils = immune response to parasites & allergic reactions

  c) basophils = mediate inflammation

  3) Natural killer cells = act in innate immunity, located in blood & the spleen

  4) Dendritic cells = located in lymphoid organs, play role in innate immunity but also activate T cells

  5) Macrophages = function as phagocytes
• State the ways in which the lymphatic and immune systems are connected structurally and functionally.

  1) lymphoid tissues & organs provide a residence for cells of the immune system

  2) lymphoid organs & tissues trap pathogens for the immune system

  3) lymphoid organs activate cells of the immune system
• Briefly describe the general function of the complement system that serves as the second line of defense.

  a group of ~30 proteins that function in innate immunity; primarily circulate in their inactive forms and must be activated through 1 of 3 complement pathways: classic, lectin, or alternative; function in cell lysis, enhancing inflammation, neutralizing viruses, enhancing phagocytosis, & clearance of immune complexes
• Define cytokines, and briefly describe the general function of interferons and interleukins.

  proteins produced by several types of leukocytes that enhance the immune response in some way

  interferons = produced in response to infection by intracellular pathogens; inhibit viral replication inside host cells & activate components of both innate & adaptive immunity

  interleukins = 29 cytokines that are produced by & also affect leukocytes, i.e. stimulating neutrophil production, stimulating NK cells, triggering the production of specific IFNs, & activating T cells
• Define inflammation, and briefly describe the following with regards to inflammation:

  the series of events that occur in response to cellular injury; involves vasodilation, increased capillary permeability, pain, swelling, & decreased function

  1) Triggers = cell damage due to trauma, bacterial or viral invasion, toxins, heat, or chemicals

  2) Benefits of inflammation as a 2nd line of defense = triggers a series of events to wall off the damaged area from the rest of the body, clean up damaged cells & components, & bring cells & proteins to the area to repair the damaged tissue

  3) 4 cardinal signs of inflammation = redness, heat, swelling, & pain

  4) Mechanism of action of anti-inflammatory medications = block the production of prostaglandins &/or leukotrienes by mimicking actions of cortisol, inhibiting COX
• Using Figure 20.12, briefly explain the processes involved in the phagocyte response.

  1) local macrophages are activated

  2) neutrophils migrate by chemotaxis to the damaged tissue & phagocytize bacteria & cellular debris

  3) monocytes migrate to the tissue by chemotaxis & become macrophages

  4) bone marrow increases production of leukocytes, leading to leukocytosis
• Define fever and name the fever-inducing chemical.

  body temperature above the normal range (36-38 degrees C/97-99 degrees F); induced by pyrogens, which are released from damaged cells & bacteria
• Name the control center in the brain that acts as a thermostat, and briefly describe the benefits and risks of a fever.

  the hypothalamus is acted upon by pyrogens which cause it to reset the thermostat to a higher range

  benefits: phagocytes may function more efficiently at a higher body temperature

  risks: body temperature gets too high for body cells to survive
• Name the two branches of adaptive immunity & the immune cell involved in each branch.

  1) cell-mediated adaptive immunity (T cells)

  2) antibody-mediated immunity (B cells)
• State the targets for cell-mediated immunity.

  cells infected with intracellular pathogens (viruses & bacteria), cancer cells, & foreign cells
• Define antigens, self-antigens, and foreign antigens.


  antigen = a unique glycoprotein marker found on the surface of nearly all cells & biological chemical substances (ANTIbody-GENerating)

  self-antigens = antigens present on your own cells

  foreign antigens = antigens present on cells & substances not native to your body, & thus cause an immune response (immunogens)
• Define haptens, and describe how haptens become an antigen.


  haptens = small molecules that elicit an immune response only when attached to a large carrier such as a protein
• State the location where T lymphocytes are produced.

  in bone marrow
• State the location where T lymphocytes mature.

  the thymus