Ch 12 Lymphatic System

bacteria, viruses, fungi, protists/ worms

What are the 4 major types of pathogens?

bacteria

Type of pathogen:

• Prokaryotic

• Lipopolysaccharide or peptidoglycan in cell walls

• Adhere to and multiply by feeding off body

• Produce/secrete toxins causing symptoms

viruses

Type of pathogen:

• DNA/RNA strands wrapped in protein

• Non-living; require host cells to propagate

• Unique molecular patterns recognized easily by immune system

fungi

Type of pathogen:

• Eukaryotic

• Recognized by cell wall components (chitin and glucans)

protists/ worms

Type of pathogen:

• Eukaryotic organisms

• Protists: Unicellular

• Worms: Multicellular

lymphatic system

Concentrate and screen interstitial fluid for pathogens

lymph tissue, bone marrow, lymph

What are the three components of the lymphatic system?

lymphatic capillaries

Lymphatic tissue:

• Low-pressure single-cell thick vessels

• Moves toward heart via pressure gradients & muscle help

• Flow: Capillaries → vessels → trunks → ducts

lymph nodes

Lymphatic tissue:

• Receives lymph from lymphatic vessels

• House leukocytes for immune response initiation

• Enters via afferent & exits via efferent vessels

right lymphatic duct

Lymphatic duct:

• upper right quadrant of body → right subclavian/internal jugular vein junction

thoracic duct

Lymphatic duct:

Rest of the body → left subclavian/jugular vein junction

bone marrow, thymus

What are the two primary lymphoid organs?

• Involved in leukocyte development

lymph nodes, spleen

What are the two secondary lymphoid organs?

lymph nodes

Secondary lymphoid organ:

• House mature leukocytes

• Areas at high risk: axillary, inguinal, cervical

spleen

Secondary lymphoid organ:

• “Largest lymph node”

specialized nodes

Tonsils, Peyer’s patch, MALT (mucosa-associated), BALT (bronchus-associated)

immunity

the ability to resist damage from pathogens, harmful chemicals, and internal threats

innate immunity

Type of immunity:

• Non-specific

• Present at birth

• Body recognizes and destroys certain pathogens the same way each time, regardless of previous exposure

• Anatomical structures and physiological processes that provide resistance to pathogens that causes diseases

• Physical barriers and internal defenses

first line of defense

Innate (non-specific immunity)

1. Barriers physically difficult to cross (e.g. skin, sweat, tears, saliva)

2. If compromised due to injury or other condition, second line of defense mechanisms triggered

physical, chemical barriers

What is the first line of defense in innate immunity?

• Will not feel sick

skin

First line of defense:

• Physical Barrier: Impenetrable in most cases, composed of tightly packed epithelial cells and dead keratin-filled sacs.

• Microbiome: Dry environment with a suited microbiota that competes with pathogens.

• Chemical Defense: Sebum (unsaturated fatty acids) creates an acidic environment (pH 3-5).

• Self-Cleaning: Constant sloughing of dead cells removes attached microbes

mucus

First line of defense:

Epithelial Cells:
Internal layers are thinner than skin layers (G.I., G.U., respiratory, eyes, ears).

Mucus Viscosity:
2000x more viscous than water; turns over quickly, complicating drug delivery.

Lysozyme:
Enzyme found in milk, tears, and saliva (low concentration in cow milk).

Chemical Defense:
Gastric juice maintains a highly acidic pH of 1.2–3.

Excretions:
Saliva, tears, ear wax, urine...

lacrimal apparatus

First line of defense:

Glands: Produce tears (~20ml/day) for continuous eye protection.

Ducts & Sac: Channels that drain and distribute fluid across the eye.

Protective Actions: Prevents microbial settling, removes debris, repairs, and drains.

Visual Coverage: Full surface protection for both eyes.

phagocytes, inflammation, fever

What is the second line of defense for innate immunity?

phagocytes

Specialized white blood cells like neutrophils, eosinophils, and macrophages that engulf and digest pathogens

inflammation

A localized response to injury or infection characterized by redness, heat, swelling, and pain to limit damage

fever

A systemic increase in body temperature that inhibits microbial growth and speeds up body repair processes

1. High body temperature; normal innate immune response

2. Pathogens and leukocytes release pyrogens to signal hypothalamus to raise body temperature

3. Inhibits production of virus and bacteria, promotes healing, and enhances immune response

antimicrobials

Substances like interferons and complement proteins that directly attack or inhibit the reproduction of pathogens

antigen presenting cells

Cells presenting foreign fragments to lymphocytes to trigger adaptive immunity

tissue injury, vasodilation, increased permeability, phagocyte mobilization

Put these 4 phases of inflammation in order:

• Increased permeability

• Tissue injury

• Phagocyte mobilization

• Vasodilation

adaptive immunity

What is the third line of defense?

antigens

Unrecognized foreign objects

cell, antibody mediated

What are the two types of adaptive immunity?

cell mediated immunity

Adaptive immunity (T cells)

1. Targets intracellular pathogens

2. Cytotoxic T cells survey own cells and look for unhealthy cells

3. Cancerous or pathogen-infected cells, antigen displayed by MHC-I

• Cytotoxic T cells release perforins and granzymes

antibody mediated immunity

Adaptive immunity - Humoral (B cells)

1. Th2: cells that secrete cytokines that induce B cells to differentiate into plasma cells

2. Th2 stimulates B cells to promote secretion of antibodies out of the cell and into surrounding body fluid

3. Good against free bacteria, viruses, and toxins

natural passive immunity

Immunity acquired from antibodies passed in breast milk or through placenta

natural active immunity

Immunity gained through illness and recovery

artificial passive immunity

Immunity gained through antibodies harvested from another person or an animal

artificial active immunity

Immunity acquired through a vaccine