A&P II Exam 2

Immune System Definition

not an organ system, but a cell population that inhabits all organs and defends the body from agents of disease

Immunity (in relation to lymphatic system)

Excess fluid picks up foreign cells and chemicals from the tissues

Lipid absorption (in relation to lymphatic system)

lacteals absorb

• We cannot absorb it into the bloodstream, so we absorb in lymphatic system

Lymph

The recovered fluid

• fluid that has leaked out of the bloodstream

Lymphatic Vessels

transport the lymph (leaked fluid)

Lymph Characteristics

• clear, colorless fluid

• originates as extracellular fluid drawn to lymphatic capillaries

how do lymphatic capillaries move?

move through a pressure gradient from high to low pressure

lymphatic capillaries are closed or open?

they are closed at one end so that liquid can come in not out.

what is the difference between lymphatic vessels and lymphatic capillaries?

Lymphatic vessels have one-way valves, whereas capillaries have two-way valves.

three layers of lymphatic vessels are:

• tunica interna: endothelium and valves

• tunica media: elastic fibers, smooth muscles

• tunica externa: thin outer layer

right lymphatic duct

Receives lymph from the right arm, right side of head, and thorax; empties into the right subclavian vein. (minority of body)

thoracic duct

larger and longer. Receives lymph from the left arm, left side of the head, neck, and thorax; empties into the left subclavian vein.

subclavian veins

collect from the thoracic duct

natural killer cells (NK)

large lymphocytes that attack and destroy bacteria, transplanted tissue, host cells infected with viruses or that have turned cancerous.

T lymphocytes (T cells)

mature in the thymus; intracellular

B lymphocytes (B cells)

Activation causes proliferation and differentiation into plasma cells that produce antibodies.

an antigen is anything that…

triggers an immune response

dendritic cells

• Branched, mobile APCs found in epidermis, mucous membranes, and lymphatic organs

• Alert immune system to pathogens that have breached the body surface

Reticular cells

Branched stationary cells that contribute to the stroma of a lymphatic organ

lymphatic (lymphoid) tissue

aggregations of lymphocytes in the connective tissues of mucous membranes and various organs

diffuse lymphatic tissue

• Lymphocytes are scattered (not clustered)

• Prevalent in body passages open to the exterior

  • Respiratory, digestive, urinary, and reproductive tracts

  • Mucosa-associated lymphatic tissue (MALT)

lymphatic nodules (follicles)

Dense masses of lymphocytes and macrophages that congregate in response to pathogens

primary lymphatic organs

Where lymphocytes are “trained”

• red bone marrow or thymus

immunocompetent

able to recognize and respond to antigens → education needed to know what to do (T & B cells)

secondary lymphatic organs

Lymph nodes, tonsils, and spleen

• Immunocompetent cells populate these tissues

thymus

member of the endocrine, lymphatic, and immune systems

• Houses developing lymphocytes

• Secretes hormones regulating their activity

• Bilobed organ located in superior mediastinum between sternum and aortic arch

• Degeneration (involution) with age

lymph nodes

most numerous lymphatic organs

• About 450 in typical young adult

two functions of lymph nodes

• cleanse the lymph

• Act as a site of T and B cell activation

Metastasis

cancerous cells break free from original tumor, travel to other sites in the body, and establish new tumors

tossils

patches of lymphatic tissue located at the entrance to the pharynx

• Guard against ingested or inhaled pathogens

• Covered with epithelium

• Have deep pits: tonsillar crypts lined with lymphatic nodules

3 main sets of nostrils

1. palatine tonsils

2. lingual tonsils

3. pharyngeal tonsil (adenoids)

palatine tonsils

• Pair at posterior margin of oral cavity

• Most often infected 

lingual tonsils

Pair at root of tongue

pharyngeal tonsils

Single tonsil on wall of nasopharynx

spleen

the body’s largest lymphatic organ

red pulp tissue (spleen)

sinuses filled with erythrocytes

white pulp (spleen)

lymphocytes, macrophages surrounding small branches of splenic artery

functions of spleen

• Healthy red blood cells (RBCs) come and go

• For old, fragile RBCs, spleen is “erythrocyte graveyard”

• Blood cell production in fetus (and very anemic adults)

• White pulp monitors blood for foreign antigens and keeps an army of monocytes for release when needed

• Stabilizes blood volume through plasma transfers to lymphatic system

pathogens

 agents capable of producing disease → loss of homeostasis

• include viruses (most common), bacteria, and fungi

first line of defense

skin, gastric secretions, and mucous membranes are physical barriers

• Before it is “inside” your body

second line of defense

several innate defense mechanisms

• Leukocytes and macrophages, antimicrobial proteins, natural killer cells, inflammation, and fever

third line of defense

adaptive immunity

• Defeats a pathogen and leaves the body with a “memory” of it so it can defeat it faster in the future.

innate defenses

First line of defense

guard equally against a broad range of pathogens

• They lack the capacity to remember pathogens

three kinds of innate defenses

• protective proteins

• Protective cells

• Protective processes

adaptive immunity

•  body must develop separate immunity to each pathogen

  • Body adapts to a pathogen and wards it off more easily upon future exposure (memory)

acid mantle

thin film of lactic and fatty acids from sweat and sebum that inhibits bacterial growth 

what does mucus do?

physically traps microbes and removes them from the body

lysozyme

enzyme destroys bacterial cell walls

phagocytes

cells that engulf foreign matter

neutrophils

• Wander in connective tissue, killing bacteria

• Can kill using phagocytosis and digestion

• Can kill by producing a cloud of bactericidal chemicals

lysosomes degranulate

Discharge enzymes into tissue fluid, causing a respiratory burst

• Creates a killing zone around the neutrophil, destroying several bacteria

eosinophils

• Guard against parasites, allergens (allergy-causing agents), and other pathogens

basophils

promote inflammation → recruits while blood cells to travel to the scene of a pathogen (good thing)

leukotrienes

activate and attract neutrophils and eosinophils

histamine

a vasodilator, which increases blood flow

• Speeds delivery of leukocytes to the area

heparin

inhibits clot formation

• Clots would impede leukocyte mobility

what is a mast cell and how is it different from a basophil?

they are the same except that mast cells are outside of the body

monocytes

emigrate from the blood into connective tissues and transform into macrophages

macrophage system

all the body’s avidly phagocytic cells, except leukocytes

wandering macrophage

actively seek pathogens

• Widely distributed in loose connective tissue

fixed macrophages

• phagocytize only pathogens that come to them

• Microglia —in central nervous system

• Alveolar macrophages —in lungs

• Hepatic macrophages —in liver

what do antimicrobial protein do?

inhibit microbial reproduction and provide short-term, Innate Immunity to pathogenic bacteria and viruses

what are the 2 families of antimicrobial proteins

Interferons & Complement system

interferons

 secreted by certain cells infected by viruses

• no benefit to the cell that secretes them

• Alert neighboring cells and protect them from becoming infected

• Bind to surface receptors on neighboring cells

  • Activate second-messenger systems within

what do NK cells destroy?

malignant cells

complement system

A group of 30 or more globular proteins that make powerful contributions to both innate immunity and adaptive immunity

• Synthesized mainly by liver

• Circulate in the blood in inactive form

• Activated by presence of a pathogen

what does activated complements bring (4 methods of pathogen destruction)

1. Inflammation

2. Immune clearance

3. Phagocytosis

4. Cytolysis

what are the 3 routes of complement activation?

1. Classical pathway

2. Alternative pathway

3. Lectin pathway

Inflammation

1. C3a stimulates mast cells and basophils to secrete histamine and other inflammatory chemicals

2. Activates and attracts neutrophils and macrophages

3. Speeds pathogen destruction in inflammation

Immune clearance

1. C3b binds with antigen–antibody (Ag-Ab) complexes to red blood cells

2. These RBCs circulate through liver and spleen

3. Macrophages of those organs strip off and destroy the Ag–Ab complexes leaving RBCs unharmed

4. Principal means of clearing foreign antigens from the bloodstream