chapter 22 : lymphatic system

What are the two main functions of the lymphatic system?

Fluid balance and protection from infection/disease.

What are the 3 functions of the lymphatic system?

Immunity, lipid absorption, fluid recovery.

What specific role do lacteals play in lipid absorption?

They absorb dietary fats from the gut and pass them to the blood.

What happens to fluid that leaks out of blood vessels?

The lymphatic system collects it and returns it to the blood.

What are the 6 components of the lymphatic system?

Lymphatic fluid, capillaries, small vessels, major vessels, ducts, and lymphatic tissue.

What is lymphatic fluid?

The liquid moving through the system from vessels into veins.

What are lymphatic capillaries?

Tiny one-way pocket-like vessels where fluid first enters the system.

What makes flow through lymphatic capillaries one-way?

Overlapping endothelial cells — fluid gets in but cannot go back.

What causes the beaded appearance of small lymphatic vessels?

Internal valves that keep fluid moving one direction.

What do major lymphatic vessels drain into?

Lymphatic trunks, which drain into ducts.

What are the 2 lymphatic ducts?

Right Lymphatic Duct and Thoracic Duct.

What side of the body does the Right Lymphatic Duct drain?

The right side only.

Where does the Right Lymphatic Duct empty?

Into the right subclavian vein.

What does the Thoracic Duct collect?

Lymph from below the diaphragm and the left side above it.

Where does the Thoracic Duct empty?

Into the left subclavian vein.

What is a germinal center?

An area of active lymphocyte growth inside lymphatic tissue.

What makes lymphatic tissue different from other organs structurally?

It has no fibrous capsule surrounding it.

What are the 2 types of lymphatic tissue?

MALT and Tonsils.

Where is MALT located?

Along mucous membranes of the gut and airways.

Where are tonsils located?

Associated with the pharynx.

What are the 3 lymphatic organs?

Lymph nodes, thymus gland, spleen.

What is the shape and function of lymph nodes?

Bean-shaped organs that filter lymph.

In what direction does fluid move through a lymph node?

Cortex → medulla → medullary cords.

What is the role of the afferent lymphatic vessel?

Brings lymph from tissue into the node.

What is the role of the efferent lymphatic vessel?

Carries lymph away from the node.

Where is the thymus gland located?

Behind the sternum.

What happens in the cortex of the thymus?

T cells divide and mature.

What happens in the medulla of the thymus?

Mature T cells enter the bloodstream.

What are the two functions of the spleen?

Filters blood and stimulates B and T cell responses.

What does the red pulp of the spleen contain?

Red blood cells.

What does the white pulp of the spleen contain?

Lymph tissue with lymphocytes.

What process produces all lymphocytes and where does it occur?

Lymphopoiesis, in the bone marrow.

What are the 3 types of lymphocytes?

T cells, B cells, Natural Killer cells.

Where do T lymphocytes mature?

In the thymus.

What do T lymphocytes determine?

Self vs. non-self.

What 2 cell types do T lymphocytes include?

Cytotoxic and helper cells.

Where do B lymphocytes mature?

In the bone marrow.

What do B lymphocytes differentiate into?

Plasma cells that produce antibodies.

Where do Natural Killer cells mature?

In the bone marrow.

What do Natural Killer cells attack?

Virus-infected and cancerous cells.

Which lymphocytes have memory?

T cells and B cells.

Which lymphocyte has no memory?

Natural Killer cells.

What are the 2 categories of body defenses?

Innate and adaptive.

What makes innate defense different from adaptive?

Innate does not distinguish between threats. Adaptive targets specific ones.

When is innate defense present?

From birth — it is genetically determined.

What are the 7 components of innate defense?

Physical barriers, phagocytes, immunological surveillance, interferons, complement, inflammation, fever.

What is the role of physical barriers in innate defense?

Skin and hair block pathogens from entering the body.

What cells carry out phagocytosis in innate defense?

Macrophages.

What is immunological surveillance?

NK cells patrolling and destroying abnormal cells.

What are interferons?

Antiviral chemicals released to protect neighboring cells from viral infection.

What is the Membrane Attack Complex (MAC)?

A structure that punches holes in bacterial cell membranes to destroy them.

What does complement do in innate defense?

Proteins assist antibodies in destroying pathogens.

What is the purpose of inflammation?

Swelling and redness that walls off and contains the infection.

What does fever do to help fight infection?

Raises body temperature to increase phagocyte activity.

What cells coordinate adaptive defense?

B and T cells.

What makes adaptive defense stronger after the first exposure?

It builds memory — future responses are faster and stronger.

What are the 2 forms of adaptive immunity?

Active and passive.

What is the difference between active and passive immunity?

Active — your body builds its own response. Passive — you receive ready-made antibodies from another source.

What are the 2 types of active immunity?

Naturally acquired and artificially induced.

What is naturally acquired active immunity?

Getting sick naturally and your body building the defense.

What is artificially induced active immunity?

A vaccine — controlled exposure to an antigen.

What are the 2 types of passive immunity?

Naturally acquired and artificially induced.

What is naturally acquired passive immunity?

Maternal antibodies passed to a baby.

What is artificially induced passive immunity?

Pre-made antibodies given by a doctor to fight an infection immediately.

What are the 5 properties of adaptive immunity?

Specificity, versatility, memory, tolerance, divided into cell-mediated and antibody-mediated responses.

What does specificity mean in adaptive immunity?

It targets one particular antigen, not all threats.

What does versatility mean in adaptive immunity?

It can respond to many different antigens.

What does tolerance mean in adaptive immunity?

It recognizes your own cells and does not attack them.

What are the 2 response types within adaptive immunity?

Cell-mediated and antibody-mediated.

What are the 2 types of T cells in cell mediated immunity?

Cytotoxic T cells (CD8) and Helper T cells (CD4).

What do Cytotoxic T cells (CD8) do?

Attack and destroy infected or dangerous cells physically and chemically.

What do Helper T cells (CD4) do?

Release signals that stimulate B and T cell responses.

What is antigen presentation?

A cell displays a pathogen piece on its surface using MHC proteins to activate a T cell.

What does MHC stand for?

Major Histocompatibility Complex.

What are the 2 classes of MHC proteins?

MHC Class I and MHC Class II.

Where is MHC Class I found?

On every nucleated cell in the body.

What does MHC Class I display?

Cytoplasmic proteins from inside the cell — abnormal ones flag the cell for destruction.

Where is MHC Class II found?

Only on antigen-presenting cells like macrophages and B cells.

What does MHC Class II display?

Pieces of a pathogen the cell has engulfed, shown to activate helper T cells.

What 2 things must match for a T cell to activate?

The correct MHC class AND the specific antigen it recognizes — both must be present.

What are the 2 CD coreceptors?

CD8 on cytotoxic T cells and CD4 on helper T cells.

What does CD8 help the cytotoxic T cell bind to?

Class I MHC plus the antigen.

What does CD4 help the helper T cell bind to?

Class II MHC plus the antigen.

What are the 2 classes of CD8 cells?

Cytotoxic T cells and Memory Cytotoxic T cells.

How does a cytotoxic T cell destroy its target?

Locks onto Class I MHC and antigen, then releases perforins that punch holes in and destroy the target cell.

What are Memory Cytotoxic T cells?

Leftover cells from a past infection that stay active and rapidly multiply if the same antigen returns.

What are the 2 classes of CD4 cells?

Helper T cells and Memory Helper T cells.

What do cytokines do when released by Helper T cells?

Stimulate T cell division and activate B cells.

What are Memory Helper T cells?

Leftover cells from a past infection that rapidly expand and speed up response if the same antigen returns.

What are the steps of B cell activation?

Naive B cell binds antigen → presents it with MHC → activated helper T cell binds and activates it → becomes a plasma cell.

What are the 2 classes of B cells?

Plasma cells and Memory B cells.

What do plasma cells produce?

Large amounts of antigen-specific antibodies.

What do Memory B cells do when re-exposed to an antigen?

Rapidly produce new plasma cells for a faster response.

What are antibodies made of?

Heavy and light protein chains with a variable region that binds the antigen and a constant region that signals immune cells.

What are the 5 things antibodies can do?

Neutralize, agglutinate, opsonize, activate complement, activate macrophages.

What does neutralize mean?

Antibody blocks the pathogen from entering cells.

What does agglutinate mean?

Antibody clumps pathogens together for easier destruction.

What does opsonize mean?

Antibody coats the pathogen so phagocytes recognize and eat it faster.

What does activating complement mean?

Antibody triggers the chain reaction of proteins that destroys the pathogen.

What does activating macrophages mean?

Antibody calls in macrophages to engulf and finish off the pathogen.