ALFS, L5: Anatomy of the Lymphatic System

Given definition, answer w/ term

Cardiovascular and immune

List the 2 principal roles of the lymphatic system

Cardiovascular

1 of the 2 Roles of the Lymphatic System:

• Maintains fluid balance and homeostasis via 2 distinct pressures that cause fluid to move between blood and tissues:

  • Hydrostatic pressure – push force that moves fluid _???___ from __???__ located in capillaries

  • Osmotic pressure – pull force generated by differences in the protein concentration between blood plasma and tissue fluid

• Lymphatic system runs parallel to the venous cardiovascular system, drains interstitial fluids, and deposits back into the cardiovascular system

Immune

1 of the 2 Roles of the Lymphatic System:

• Component of the surveillance system that defends the body

?? Creates excess fluid bluid, which would be bad, fill in reason

Enter the lymphatics

Lymphatic system

• Function:

  • Returns excess fluid back into circulation

  • Surveillance of infection/abnormality

• Anatomy:

  • Mirrors the venous system (e.g. lymphatic vessels are made of simple epithelial cells)

  • No intrinsic pump, the movement of lymph is driven by pressure changes caused by contraction of surrounding muscles

  • Has 2 main ducts ???? that prevent retrograde flow (??)

Lymph

• Function: fluid balance & immune

• Formation: ???

Edema

• Definition: Abnormal accumulation of interstitial fluid

• Examples:

  • Chronic heart disease – caused by increase in venous hydrostatic pressure

  • Loss of plasma protein – caused by decrease in blood osmotic pressure

  • Inflammation – caused by increased blood vessel permeability

  • Neoplastic obstruction of lymphatic vessels – caused by blockage of lymphatic drainage

Inflammation

• Inflammatory response in local tissue, consequences include:

  • Edema

  • Extra-vasation of immune cells into interstitial fluid

  • Antigen presenting cells – Specialized antigen-presenting cells migrating ???

Antigen presenting cells (APC)

• Function: Specialized antigen-presenting cells migrating ???

• Examples: ???

Afferent lymphatic vessels > subcapsular sinus > travecular sinuses > medullary sinus > efferent lymphatic vessel

List the main 5 steps in flow of lymph through a lymph node

T and B cells

While fluid is moving through the lymph node, they’re exposed to _______ and _______ cells

Afferent lymphatic vessels

Lymph Flow Through Lymph Node:

• Diagram: #1

Subcapsular sinus

Lymph Flow Through Lymph Node:

• Diagram: #2

Trabecular sinuses

Lymph Flow Through Lymph Node:

• Diagram: #3

Medullary sinus

Lymph Flow Through Lymph Node:

• Diagram: #4

Efferent lymphatic vessel

Lymph Flow Through Lymph Node:

• Diagram: #5

T-cells in the paracortex

Lymph Flow Through Lymph Node:

• Antigen presenting cells get trapped in trabecular sinuses and interact with #6

B cells located in the cortex

Lymph Flow Through Lymph Node:

• #7 located in the cortex in lymphoid follicles – upon activation form germinal centers

Plasma cells in medullary cords

Lymph Flow Through Lymph Node:

• _______ cells (antibody secreting B cells) located in _______ cords

Connective capsule

Lymph Node Histology

• Diagram: A

Cortex

Lymph Node Histology

• Diagram: B

Medulla

Lymph Node Histology

• Diagram: C

Follicles

Lymph Node Histology

• Diagram: D

Germinal center

Lymph Node Histology

• Diagram: E

Antigen stimulation

Most B and T cells in lymph node are naive (unstimulated), and upon _______ stimulation proliferate, and cause enlargement of the lymph node

On a histological sample,

-inrease in ytoplasm

differences in how cytoplasm and nuclei pick up stain

put in picture

Primary lymphoid organs

• Function: Site of production and early maturation of B and T cells:

• Function:

  • Thymus – primary maturation of T cells

  • Bone marrow – production and primary maturation of B cells and production of T cells ??

  • Bursa of fabricius

Secondary lymphoid organs

• Function:

  • Site for maintaining naive lymphocytes

  • Where lymphocytes are activated due to encountering & responding to antigens

• Examples:

  • Spleen – screen lymph

  • Lymph nodes – screens blood

  • Peyer’s patches and mucosal associated lymphoid follicles (MALTs)

  • Tonsils

Spleen

Screening organ for blood, analogous to lymph in the lymph nodes

Arterioles > periarteriole lymphatic sheath > margina zone > red pulp > venus sinusoids > efferent veins

List the main 5 steps in flow of blood through the spleen

Arterioles

Blood Flow Through Spleen:

• Diagram: #1

Perarteriole lymphatic shealth (PALS)

Blood Flow Through Spleen:

• Diagram: #2

Marginal zone

Blood Flow Through Spleen:

• Diagram: #3

Red pulp

Blood Flow Through Spleen:

• Diagram: #4

Venus sinusoids

Blood Flow Through Spleen:

• Diagram: #5

Efferent veins

Blood Flow Through Spleen:

• Diagram: #6

T and B cells

While blood is moving through the spleen, they’re exposed to _______ and _______ cells

Thymus

Components of Lymphatic System:

• where T cells mature

Bone marrow

Components of Lymphatic System:

• Production of B and T cells

• Maturation of B cells

Spleen

Components of Lymphatic System:

• o

M cells

Take sample of gut

Pass it through a pseudo lymph node (aka pass it by T and B cells) and then out through an efferent lymphoid vessel

Problem is, it will identify many non-self particles that aren’t harmful to the host (aka food), ongoing area of research

M cell

function – specialized areas distributed throughout the small intestines, allows body to identify pathogens

locoated over the peyer’s patches

many pathogens have developed systems to hijack and attach thesmelves to M cell, and allow them to enter the GI tract ???

peyer’s patch - organized lymphatic tissue, APC, B and T cells, that activate the immune response

Peyer’s patches

Components of Lymphatic System:

• Definition: Organized lymphoid follicles in distal ileum

• Location: Lies underneath M cells

• function: screens mucosal membrane of GI tract