AP 2 Exam 3

What are the two main functions of the lymphatic system?

Transports/houses lymphocytes to defend against foreign substances, and returns excess interstitial fluid to venous blood to maintain fluid balance, blood volume, and blood pressure.

What are the three main components of the lymphatic system?

Lymph vessels, lymphoid tissues, and lymphoid organs.

What is lymph, and what percent of interstitial fluid becomes lymph?

The fluid transported in lymph vessels, formed from fluid that leaves blood capillaries and isn't reabsorbed; ~15% of interstitial fluid.

What is lymph composed of? 

Water, dissolved solutes, small proteins, and foreign material (debris, pathogens, metastasized cancer cells).

Describe the structure of lymphatic capillaries. 

Small, closed-ended vessels; slightly larger than blood capillaries; no basement membrane; overlapping endothelial cells with flaps let fluid in but not out; anchored by anchoring filaments.

Where are lymphatic capillaries absent? 

Avascular tissue, red marrow, spleen, and CNS.

What are lacteals? 

Lymphatic capillaries in the GI tract that absorb lipid-soluble substances.

How does fluid move into lymphatic capillaries?

Increased hydrostatic pressure in interstitial fluid pushes fluid through the endothelial flaps into the capillary, where it becomes trapped.

What is the route of lymph flow from capillaries to the bloodstream?

Lymphatic capillaries → lymphatic vessels → lymphatic trunks → lymphatic ducts → subclavian vein.

How do lymphatic vessels differ structurally from lymphatic capillaries?

Vessels have 3 tunics (like blood vessels) and valves (like veins) to prevent backflow; capillaries lack these.

What 3 mechanisms move lymph through lymphatic vessels (since there's no pump)?

The skeletal muscle pump, the respiratory pump, and rhythmic contraction of smooth muscle in larger lymph vessels.

Name the 5 lymphatic trunks and what each drains.

Jugular (head/neck), subclavian (upper limbs, breast, thoracic wall), bronchomediastinal (thoracic wall), intestinal (abdominal structures), lumbar (lower limbs, abdominopelvic wall, pelvic organs).

What does the right lymphatic duct drain? 

The right side of the head/neck, right upper limb, and right thorax.

What does the thoracic duct drain? 

The left side of the head/neck, left upper limb, left thorax, the entire abdomen, and both lower limbs.

What is the cisterna chyli? 

A sac-like structure that stores chyle (milky, lipid-rich lymph), located at the base of the thoracic duct.

What is lymphedema and what causes it? 

Accumulation of interstitial fluid from blocked lymphatic drainage (trauma, infection, tumor, radiation, or node removal); causes swelling/pain and can impair wound healing.

What is elephantiasis? 

An extreme form of lymphedema, often caused by parasitic worms.

Differentiate primary vs. secondary lymphoid structures.

Primary: formation/maturation of lymphocytes (red bone marrow, thymus). Secondary: house lymphocytes and initiate immune responses (lymph nodes, spleen, tonsils, lymphatic nodules, MALT).

Where is red bone marrow located, and what is its function?

In trabeculae of spongy bone (skull, ribs, sternum, vertebrae, ossa coxae, humerus/femur heads); site of hematopoiesis.

Where do T-lymphocytes and B-lymphocytes mature?

T-lymphocytes are made in red bone marrow but migrate to the thymus to mature; B-lymphocytes are made AND matured in red bone marrow.

Describe the structure and function of the thymus.

Bilobed organ above the heart; site of T-cell maturation; grows until puberty then regresses into adipose tissue. Cortex has immature T-cells; medulla has mature T-cells.

What hormone aids T-cell maturation in the thymus?

Thymulin.

What is the function of lymph nodes, and where are the major clusters?

Filter lymph and remove unwanted substances; clusters include cervical (head/neck), axillary (breast/axilla/upper limb), and inguinal (lower limb/pelvis) nodes.

Differentiate afferent vs. efferent vessels of a lymph node.

Afferent vessels bring lymph IN (multiple); efferent vessels drain lymph OUT (single exit).

What is found in the cortex of a lymph node? 

Lymphoid nodules with germinal centers (proliferating B-cells/macrophages) surrounded by the mantle zone (T-cells, macrophages, dendritic cells); cortical sinuses.

What is found in the medulla of a lymph node?

Medullary cords (B cells, T cells, macrophages) and medullary sinuses.

What is the hilum of a lymph node? 

An indented region lined with macrophages.

Describe lymphoma and its two types. 

Malignant neoplasm of lymphoid tissue presenting as a nontender

enlarged node with possible night sweats/fever/weight loss. Hodgkin

(young adults/60+, often curable) vs. non-Hodgkin (more common,

variable aggressiveness).

Where is the spleen located, and what is its largest classification?

Largest lymphoid organ; left upper abdominal quadrant, lateral to the left kidney, posterolateral to the stomach.

What is the function of white pulp in the spleen?

Clusters of T- and B-lymphocytes and macrophages around the central artery; monitors BLOOD for foreign material and bacteria.

What is the function of red pulp in the spleen? 

Contains erythrocytes, platelets, macrophages, B-cells; splenic cords and sinusoids phagocytize bacteria/debris and defective RBCs/platelets; storage site for erythrocytes/platelets.

Trace blood flow through the spleen. 

Splenic artery → central artery (white pulp) → splenic sinusoid (red pulp) → venules → splenic vein → IVC.

Does the spleen filter blood or lymph? 

Blood, not lymph.

What is a splenectomy and its most common cause?

Surgical removal of the spleen, most commonly due to a ruptured spleen from abdominal injury; increases susceptibility to life-threatening infection.

Name the three tonsil groups and their locations.

Pharyngeal tonsil (adenoids) – pharynx; palatine tonsils – oral cavity (most commonly infected); lingual tonsil – back of the tongue.

What are tonsillar crypts? 

Invaginations that trap material and contain lymphoid nodules, some with germinal centers.

What is tonsillitis? 

Inflammation/infection of the tonsils (usually palatine); causes redness, swelling, possible obstruction, fever, chills, sore throat.

What are lymphatic nodules? 

Clusters of lymphoid cells (not fully encapsulated) found in every body organ; scattered nodules are called diffuse lymphoid tissue.

What is MALT, and where is it found? 

Mucosa-associated lymphoid tissue; lymphoid nodules in the lamina propria of GI, respiratory, genital, and urinary mucosa; defends against foreign substances.

What are Peyer patches? 

Large collections of lymphoid nodules in the wall of the GI tract, prominent in the small intestine (especially the ileum).

Name the 5 categories of infectious agents and give an example of each.

Bacteria (strep throat), Viruses (Ebola), Fungi (ringworm), Protozoans (malaria), Multicellular parasites (tapeworm).

Which pathogen type is an obligate intracellular parasite?

Viruses — they must enter a cell to reproduce

What are prions? 

Fragments of infectious protein (neither cells nor viruses) that cause disease in nervous tissue, e.g., variant Creutzfeldt-Jakob ("mad cow") disease; can spread from cows to humans via infected meat.

What are cytokines and their 3 modes of action?

Small soluble proteins that communicate between immune cells and regulate inflammation/effector cells; act via autocrine (self), paracrine (neighboring cells), or endocrine (blood-circulated) stimulation.

Differentiate innate vs. adaptive immunity. 

Innate: born with it, immediate, nonspecific. Adaptive: acquired, involves T/B lymphocytes responding to specific antigens, takes days to become effective.

What does the skin do as a first line of defense?

Physical barrier releasing antimicrobial substances (sebum, lysozymes, defensins, dermcidin); normal flora prevents pathogen growth

What do mucosal membranes secrete, and how do they defend the body?

Produce mucin (forms mucus that traps substances) and release lysozyme, defensins, and IgA; respiratory cilia sweep out microbes; GI tract uses saliva/stomach acid.

What is commensal (normal) microflora? 

Nonpathogenic microorganisms on body surfaces that interfere with pathogen attachment.

Compare neutrophils and macrophages. 

Both destroy pathogens via lysosome + respiratory burst; macrophages also present antigens and clean up infected/injured tissue; neutrophils are first responders.

What is the role of dendritic cells in innate immunity?

Destroy pathogens and present antigen fragments to T-lymphocytes, initiating an immune response

Differentiate basophils and mast cells. 

Basophils circulate in blood and release granules during inflammation; mast cells reside in CT/mucosa/organs and release granules (histamine, heparin, eicosanoids).

How do NK cells destroy target cells? 

Via perforin (forms membrane pores) and granzymes; target infected, tumor, or transplanted cells.

What is the role of eosinophils? 

Target parasites via degranulation and phagocytosis of antigen-antibody complexes; use toll-like receptors for pattern recognition.

Describe the actions of interferons (IFN-alpha/beta vs. IFN-gamma).

IFN-alpha/beta (from leukocytes/infected cells) destroy viral RNA/DNA in nearby cells and stimulate NK cells; IFN-gamma (from T/NK cells) stimulates macrophages to destroy infected cells.

Differentiate the classical and alternative complement pathways.

Classical: complement binds an antibody already attached to a foreign substance. Alternative: bacterial/fungal proteins bind complement directly.

What are the four major actions of the complement system after activation?

Inflammation, opsonization (coats pathogen for phagocytosis), cytolysis (forms MAC to lyse pathogen), and elimination of immune complexes (cross-links to RBCs for liver/spleen destruction).

What triggers inflammation, and what are the vascular changes that follow?

Injured tissue/basophils/mast cells release histamine, leukotrienes, prostaglandins, chemotactic factors → vasodilation, increased capillary permeability, increased leukocyte-adhesion molecules.

Define margination, diapedesis, and chemotaxis.

Margination = leukocyte adherence to CAMs; diapedesis = escaping vessel walls; chemotaxis = migration toward chemical signals.

What are the cardinal signs of inflammation and their causes?

Redness & heat (↑blood flow/metabolism), swelling (fluid loss from capillaries), pain (pressure + chemical irritants), and loss of function in severe cases.

What is pus, and what is an abscess? 

Pus = exudate of destroyed pathogens, dead leukocytes/macrophages, and debris. Abscess = pus walled off by collagen; may need surgical drainage.

What is a fever, and what causes it? 

Body temp elevation ≥1°C above 37°C caused by pyrogens acting on the hypothalamus, raising the temperature set point.

What are the 3 stages of fever? 

Onset (temp rises via vasoconstriction/shivering) → Stadium (elevated temp maintained, liver/spleen sequester zinc/iron) → Defervescence (temp returns to normal via vasodilation/sweating).

What temperature thresholds cause fever risks?

Seizures possible above 102°F; irreversible brain damage above 106°F; death possible above 109°F.

What are the two branches of adaptive immunity?

Cell-mediated immunity (T-lymphocytes) and antibody-mediated/humoral immunity (B-lymphocytes, plasma cells, antibodies).

What is an antigen, and what is an antigenic determinant (epitope)?

Antigen = a molecule that binds a component of adaptive immunity (TCR or antibody). Epitope = the specific site on the antigen recognized by the immune system.

What factors increase an antigen's immunogenicity?

Increased foreignness, size, complexity, or quantity.

What is a hapten? 

A molecule too small to be immunogenic alone; becomes immunogenic only when attached to a carrier molecule (e.g., poison ivy toxin, penicillin, pollen).

Differentiate TCR and BCR antigen recognition.

TCR requires antigen to be processed and presented by another cell; BCR makes direct contact with intact antigen (no APC needed)

What are the 4 T-cell subtypes and their functions?

Helper T (CD4+) – assists cell-mediated & humoral immunity; Cytotoxic T (CD8+) – induces apoptosis in target cells; Memory T – speeds future response; Regulatory T (Treg) – suppresses immune response.

Differentiate MHC I and MHC II. 

MHC I: on all nucleated cells, presents self/viral antigens, interacts with CD8 (Cytotoxic T). MHC II: only on APCs (dendritic cells, macrophages, B-cells), presents exogenous antigens, interacts with CD4 (Helper T).

Why are organ transplants tested for MHC/ABO compatibility?

No two individuals share identical MHC molecules; mismatches trigger rejection, so recipients are often given immunosuppressive drugs.

Where do B- and T-lymphocytes mature? 

B-lymphocytes mature in red bone marrow; T-lymphocytes migrate to the thymus as pre-T cells (thymocytes) to mature.

Differentiate positive and negative selection of T-cells.

Positive selection: tests ability to bind MHC on thymic epithelial cells (failure = elimination). Negative selection: tests ability to AVOID binding self-antigens (binding = destruction; ensures self-tolerance).

What happens during T-cell differentiation in the thymus?

Surviving cells become Helper T-cells (lose CD8, keep CD4) or Cytotoxic T-cells (lose CD4, keep CD8).

What does 'immunocompetent' and 'naive' mean for T-cells leaving the thymus?

Immunocompetent = able to respond to an antigen; naive = not yet exposed to an antigen.

How are regulatory T-cells (Tregs) formed and what do they do?

CD4+ cells formed from T-cells that bind self-antigens; release inhibitory chemicals to turn off cell-mediated/humoral responses

(peripheral tolerance).