A&P EXAM: lymphatic system, immune system & respiration

functions of lymphatic vessels

• Returns fluid leaked from blood vessels

• Transports dietary fats

• Transports lymph

• Carries out immune response (structural basis of immune system)

Structure of lymphatic vessels

• Structure: similar to veins (3 layers of tunica) except

  • Thinner walls w/ more wolves

  • Anastomose more frequently

  • closed circuit

Distribution of lymphatic vessels

• Found in most of the body except teeth, bone marrow & CNS

• Major trunks

  • Lumbar

  • Intestinal

  • Bronchiomediastinal

  • Subclavian

  • Jugular

• Major ducts

  • Right lymphatic duct: drains right upper limb, right side of head & thorax

  • Thoracic duct: drains rest of body

• Ducts drain into venous circulation at corresponding subclavian veins

Mechanism(s) of lymph transport

• Transported by a one way system TO THE HEART by:

  • Milking action of skeletal muscle

  • Valves to prevent backflow

  • Contraction of smooth muscle

  • Pulsation of arteries

Basic structure & cellular population of lymphoid tissue

• 2 types: diffuse & follicles (nodules)

• Contains B & T lymphocytes, APCs (dendritic cells & macrophages), reticular cells

Diffuse vs. follicular lymphoid tissues

• Diffuse: in almost every tissue; protect from pathogens trying to enter the body

  • Lymphocytes are loosely organized

  • Commonly found in mucous membranes

  • Also known as MALT

• Follicular: solid tightly packed cells & fibers together in small spheres

  • Found in secondary lymphoid organs

  • Where antibodies are produced & B cells trained

Lymph nodes: location, histological structure, & functions

• Small vessels associated with lymphatic vessels (found in clusters along them)

• Functions:

  • Filter lymph

  • Activate immune system

• Structure:

  • Bean shaped

  • Trabeculae divide it into compartments

  • Cortex (bark):

    • Contains follicles with germinal centers (heavy w/ dividing B-cells)

    • Deep cortex houses T-cells in transit

  • Medulla (middle):

    • Medullary cords extend inward 

    • Contain B-cells, T-cells & plasma cells

Other lymphoid organs of the body

• Spleen

  • Largest lymphoid organ

  • Site of lymphocyte proliferation & immune response

  • Cleanses blood of debris & defective RBCs

  • Structure

    • White pulp: lymphocytes involved in immune function

    • Red pulp: rich in RBCs & macrophages for disposal of both

  • Tonsils

    • Simplest lymphoid organs

    • Gather & remove pathogens in food or air; trap & destroy bacteria

      • Lingual tonsils

      • Palatine tonsils

      • Tubal tonsils 

      • Pharyngeal tonsils

  • Thymus

    • “T-lymphocyte school”: place where T-cells differentiate self from non-self

    • Most active during neonatal and pre adolescence 

    • Stops growing during adolescence

Surface membrane barriers and their protective functions

• Skin & mucous membranes

  • Keratin resists weak acids, enzymes & toxins

  • Mucosa traps viruses, bacteria & dust

Importance of phagocytosis and natural killer cells in innate body defense

• Phagocytosis detects and destroys pathogens early on in the immune response

• NK cells kill cancerous cells by inducing apoptosis (cell suicide)

Inflammatory process 

Signs of inflammation: redness, swelling, pain & heat

• Leaky capillaries allow excess fluid to leak into extracellular space causing swelling and pressure on nerves causing pain

Inflammatory chemicals & their specific roles

• Histamine: induces vasodilation & increases capillary permeability

• Prostaglandins: increase blood flow to the area

• Interferons: alert neighboring cells of infection (released by virus infected cells)

Antimicrobial substances & their function

• Interferons: released by virus infected cells to warn neighboring cells of invasion

• Complement proteins: blood proteins that circulate in plasma

  • Amplify inflammation

  • Induce phagocytosis by opsonization

  • Create pores for MAC’s

How fever protects the body

• Raises internal temperature to a non-dangerous degree

  • Increases rate of phagocytosis

  • Slows rate of pathogen growth

Antigens & how they affect adaptive defenses

• Antigen: antibody generating; mobilize adaptive defenses & provoke immune response

• Affect adaptive defenses by

  • Specificity: determining how specific the immune response will be

  • Systemic: guiding the immune response

  • Memory: create memory cells to allow for a faster & stronger secondary response

Complete antigen

• Has both immunogenicity & reactivity

  • Immunogenicity: ability of an antigen to stimulate an immune response

Reactivity: ability of an antigen to bind to antibodies or immune cells

Haptens

• Incomplete antigens non immunogenic by themselves

  • Can become immunogenic by binding with body proteins

Antigenic determinants

• Only certain parts of an entire antigen are immunogenic

• MORE DETERMINANTS = MORE LIKELY TO ELICIT DESIRED RESPONSE

B & T Lymphocyte development & activation

• Origin - from red bone marrow

• Maturation

• Seeding to secondary lymphoid organs

• Antigen encounter - become activated

• Proliferation & differentiation - once activated, they divide (clonal expansion) and turn into effector cells or memory cells

T-cells: origin, maturation process & function

• Originate in thymus

• Mature by way of positive & negative selection

  • Must recognize self and non self

• Function: provide defense against self cells

• CD4 → helper T cells, regulatory T cells or memory T cells

• CD8 → cytotoxic T cells

B-cells: origin, maturation process & function

• Originate in bone marrow

• Mature by gene rearrangement & ability to bind to foreign antigens

Function: produce antibodies that target specific antigens and mark them for destruction

Immunocompetence

 ability of a lymphocyte to recognize and respond to a specific antigen using a unique receptor

Self tolerance

ability of a lymphocyte to ignore the body’s own cells and proteins to prevent autoimmune reactions

Humoral immunity

• Antibody mediated

  • Antibodies produced by B-lymphocytes

• Bind to target cells → temporarily inactivate them → mark them for destruction 

• Cannot directly kill; can only mark for destruction

B-cell clonal selection

• Antigen encounter: only B-cells with receptors matching the antigen are selected

• Activation: antigen is presented to a helper t cell; cytokines are released to fully activate the cell

• Clonal expansion: the b cells divide rapidly producing many identical cells

Active v. passive humoral immunity

• Active → make your own antibodies

• Passive → someone gave you antibodies

5 classes of antibodies

• IgM → first antibody produced in immune response

• IgG → most prevalent; fixes to complement

• IGE → binds to mast cells; important in allergic reactions & inflammation

• IgA → found in body secretions (breast milk)

IgD → function unclear

Plasma & memory B cells & their roles in humoral immunity

• Plasma cells: active fighters; produce antibodies on the spot

• Memory cells: remain in the body long term; “remember” specific antigens to allow for a faster and stronger secondary response

Cellular immunity

• T lymphocytes act against target cells

Can directly or indirectly kill cells

Types of T cells & their roles

• Cytotoxic T-cells: attack cells that display abnormal MHC-1 proteins

  • Release perforin & cause apoptosis

  • NK cells are nonspecific; these are specific

• Helper T-cells: activated by APC presentation of an antigen

  • Activates B+T cells; induces proliferation; recruits other immune cells

  • W/O these cells there is NO IMMUNE RESPONSE

• Regulatory T-cells

  • Dampen immune system response to prevent autoimmune diseases

• Memory T-cells

  • Remember previous antigens

  • Provide faster and stronger secondary response

Process of T- cell activation

1. Antigen binding: CD8 cells bind to MHC I proteins; CD4 cells bind to MHC II proteins

2. Co-stimulation: like a safety check; helps prevent attacks on self (self tolerance)

• BOTH must be received to activate T-cell

organs (in order) forming the respiratory passageway

nose

nasal cavity

sinuses

pharynx

larynx

trachea

bronchi & bronchioles

lungs

alveoli

nose: structure & function

structure: nostrils, vestibules, nasal cavity (nasal conchae & meatuses)

function:

• provides airway for respiration

• moistens and warms air

• filters and cleans air

• resonating chamber for speech

• provides sense of smell through olfactory receptors

paranasal sinuses: location & function

location: frontal, sphenoid ethmoid and maxillary bones

function:

• lighten skull

• secrete mucus

• help to warm and moisten air

pharynx: location structure & function

location: base of skull to C6

structure: composed of skeletal muscle

function: connects nasal cavity/mouth to larynx and esophagus (passageway for food and air)

larynx: location & function

location: attaches to hyoid bone

function:

• provides airway

• routes food and air to proper channels

• voice production ( houses vocal cords)

protective mechanisms of the respiratory system

• nose hairs and mucus

• cilia

• coughing and sneezing

conducting vs respiratory zone

conducting: moves gas to exchange sites

• ends at respiratory bronchioles & contains everything above

respiratory: actual site of gas exchange

• starts at respiratory bronchioles; contains alveoli and alveolar ducts

lungs

• left smaller than right due to cardiac notch

• apex: superior tip

• base: inferior surface

• hilum: site of entry/exit of blood vessels

• lobes separated by fissures

• lobules: smallest subdivisions to naked eye; served by bronchioles & their branches

boyle’s law & how it relates to inhalation/exhalation

relationship between pressure & volume of gas

• as volume increases → pressure decreases

  • inhalation: breathe in → volume increases → pressure decreases → air flows in

  • exhalation: breathe out → volume decreases → pressure increases → air flows out

container size reduced = increased pressure

factors limiting pulmonary ventilation (things that make it harder to breathe)

• airway resistance - decreases closer to respiratory zone

• alveolar surface tension - surfactant is secreted by type II alveolar cells to discourage collapse

• lung compliance - higher lung compliance = easier to expand lungs and breathe

lung volumes

tidal volume → normal quiet breathing

inspiratory reserve volume → amount of air that can be inspired after TV

expiratory reserve volume → amount of air that can be expired after tidal volume

residual volume → amount of air that remains after forcible expiration

lung capacities

vital capacity → total amount of exchangeable air

functional residual capacity → total amount of air remaining in lungs after expiration

dead space

volume of air in lungs that does not participate in gas exchange

• anatomical dead space - air in respiratory passages

• alveolar dead space - air reaches alveoli but no gas exchange occurs due to dead or collapsed alveoli

• total dead space - combination of anatomical and alveolar dead space

dalton’s law of partial pressures

total pressure exerted by mixture of gases = sum of pressures exerted by each gas

• partial pressure → pressure exerted by each gas in a mixture (directly proportional to its %)

henry’s law

when a gas is in contact with a liquid, the gas will dissolve in the liquid in proportion to its partial pressure

• more pressure = more gas dissolves in the blood

  • oxygen is at higher pressure & higher concentration → dissolves in the blood

  • CO2 is at lower pressure & lower concentration → does not dissolve in blood

ventilation-perfusion coupling

more blood flows past alveoli that are functioning best

• ventilation - amount of gas reaching alveoli

• perfusion - blood flow reaching alveoli

hypoxia