Lymphatic system & nonspecific immune | A&P I

Lymph

Interstitial fluid that has drained into the lymphatic system

Lymph is similar to plasma except:

Lacks plasma proteins

Function of lymphatic vessels

Carry lymph from peripheral tissues to be drained by the venous system

Lymphoid tissue vs lymphoid organs

Lymphoid organs are enclosed in a capsule

Two types of lymphatic cells

Stroma: structural; parenchyma: functional

Are lymphocytes stroma or parenchyma?

Parenchyma (functional)

Lymphatic vessels are similar to veins in what ways?

Carry fluid alongside arteries

Use the same forces to move fluid
Has the same three layers

Lymphatic vessels are different from veins in what ways?

Smaller & thinner
no structure analogous to the heart

Efferent lymph vessels

Carries lymph away from the node, located at hilum, less abundant than afferent

Afferent lymph vessels

Carries lymph toward the node, located on convex side, more abundant than efferent

Structure & function of endothelial cells in lymphatic vessels

Loosely bound and overlap like shingles
Acts as a one-way valve allowing material to enter but not to leave

Anchoring filaments in lymphatic vessels

Attach endothelial cells to surrounding connective tissue

How do endothelial cells & anchoring filaments in lymphatic vessel resolve edema?

Swelling from edema stretches anchoring filaments, opening up the endothelial flaps
More interstitial fluid flows into lymphatic capillaries, removing it from the tissue

Lacteal

Specialized lymphatic capillaries in the microvilli of the small intestine, drains lipids

Chyle

Lipid rich lymph located in lacteals

What happens to chyle after entering lacteals?

lymphatic vessels → intestinal duct → lumbar trunks → cisterna chyli

What happens to chyle after it collects in the cisterna chyli?

Thoracic duct → left subclavian vein → bloodstream

Lymph nodes

Organs located along lymphatic vessels that filter fluid and house immune cells

Three main clusters of lymph nodes

Inguinal, cervical, axillary

Lymphatic capillaries drain into lymphatic vessels, which drain into:

Lymphatic trunks

Lymphatic trunks drain into:

Lymphatic ducts

Which lymphatic duct drains three quarters of the body?

Thoracic duct

Which lymphatic duct drains one quarter of the body? What area?

Lymphatic duct: upper right quadrant

Lack of lymph drainage from blockage or valvular failure

Lymphedema

What are the three factors that facilitate lymph flow? (similar to veins)

Valves, respiratory pump, adjacent arteries

Three main types of lymphocytes

B cells, T cells, NK cells

Where are B cells produced and what is their function?

Bone marrow; produce antibodies targeting extracellular pathogens

Where are T cells produced and what is their function?

Thymus; target and destroy infected cells

What is the full name and function of NK cells?

Natural killer cells; patrol throughout lymphatic vessels looking for abnormal cells

Which lymphocyte is part of the specific/adaptive defense system and targets extracellular pathogens?

B cells

Which lymphocyte is part of the specific/adaptive defense system and targets intracellular pathogens?

T cells

Which lymphocyte is part of the nonspecific/innate defense system and targets intracellular pathogens?

NK cells

How do you identify a nodule (follicle) in lymphatic tissue as active?

Germinal center contains actively dividing lymphocytes; darker periphery due to increased amount of cells

MALT (mucosa-associated lymphoid tissue is located in:

Mucosa of hollow organs, tonsils, appendix, Peyer’s patches

Peyer’s patches

Clusters of MALT in the wall of the small intestine

Hilum of lymph nodes

Opening for blood vessels, nerves and efferent lymphatic vessels on the concave side of lymph nodes

Trabeculae (septa) of lymph nodes

Extensions of the lymph node capsule that divides nodules in its cortex

Medulla of lymph node

Diffused lymphoid tissue in center of lymph node

Which function of lymph nodes allows them to learn from infections to combat them better in the future?

Antigen presentation

In the thymus, ____ divides the tissue into ____

Trabeculae; lobules

Why does the thymus shrink around age 12-14?

Has finished growing & activating T-cells

Spleen is similar to a lymph node, except:

Filters blood instead of lymph

3 functions of spleen

Phagocytosis, storing iron from hemolysis, immune response

The first line of immune defense

Physical and chemical barriers

Physical barriers

Skin, hair, internal epithelium

Chemical barriers

Secretions that flush away materials (ex. sweat), secretions that kill or inhibit microorganisms (ex. stomach acid)

Second category of innate defense (after barriers)

Phagocytes

Types of phagocytes

Microphages: neutrophils and eosinophils
Macrophages: derived from monocytes, make up monocyte-macrophage system

Third category of innate defense (after phagocytes), uses NK cells

Immunological surveillance

What occurs after an NK cell identifies and attaches to an abnormal cell?

NK cell’s golgi apparatus forms perforin vesicles

What occurs after an NK cell forms perforin vesicles?

Dumps perforin from vesicles onto abnormal cell (exocytosis)

What occurs after NK cell exocytosizes?

Perforins destroy (lyse) the abnormal cell’s membrane

Fourth category of immune defense, a type of protein produced by a cell infected with a virus

Interferons

What is the function of interferons?

Prevents a virus from fusing with the DNA of a healthy cell

Fifth category of immune defense, proteins produced in liver

Complement

11 types of complement proteins

C1-9, B, P, D

Three complement protein pathways

Classical, lectin, alternative

The classical pathway of complement proteins starts by forming:

Antigen-antibody complex

In the classical pathway, what protein(s) does the antigen-antibody complex activate?

C1, C4, C2

What protein do all three complement protein pathways activate?

C3

Which complement protein pathway cannot be activated the first time the body is infected with a particular pathogen, and why?

Classical pathway: uses antibodies that are only produced after the body has experienced the first infection

The lectin complement pathway uses the protein ____ which is produced by ___

MBL, mannose binding lectin; liver

What is the first step in the lectin complement pathway

MBL binds to mannose in the cell membrane of the bacteria

What occurs in the alternative complement pathway?

C3 is spontaneously activated

How does the alternative pathway distinguish between a normal and harmful cell?

Normal cells have C3 inhibitors

Once C3 is activated by any of the three complement pathways, what occurs?

C3 splits into C3a (→ inflammation) and C3b (→ opsonization)

What is opsonization (caused by C3b)

Coats pathogen surfaces to enhance phagocytosis

What protein(s) does C3b activate (in addition to opsonization)?

C5-9

Once activated by C3b, what do proteins C5-9 do to the pathogen?

Inserts MAC (membrane attack complex) into membrane

What does the MAC (membrane attack complex, assembled by C5-9) do to the target pathogen?

Forms a pore in the membrane → water rushes in → lysis (destruction)

Five symptoms of inflammation

Swelling, redness, heat, pain, loss of function

Three positive effects of inflammation

Barrier against pathogens
Mobilizes defenses
Facilitates regeneration

Three products of inflammation

Necrosis: tissue destruction
Pus: mix of debris and necrotic tissue
Abscess: pus accumulated in enclosed space

Pyrogen

Any material that causes the hypothalamus to raise body temperature

What pyrogen is released by active macrophages?

Interleukin-1 (IL-1)

What are the seven major categories of innate (nonspecific) immune defense?

Barriers, phagocytosis, surveillance, interferons, complement, inflammation, fever