ANP 1115 - Blood Vessels & Lymphatic System Flashcards
What is Resting Vascular Tone?
in resting state, smooth muscles in walls of arterioles
somewhat contracted (sympathetic ns)
- can increase flow by vasodilation
How do Organs regulate blood flow?
organs regulate individual blood flow by varying resistance of arterioles
What are the Local, Metabolic Controls?
- declining tissue levels of oxygen
- increasing levels of CO2, adenosine, H+, K+, heat, inflammatory chemicals
What is the End Result of Metabolic Control?
immediate increased perfusion (hyperemia) of “needy” tissues
What is the Difference between Active & Reactive Hyperemia?
Active Hyperemia: blood flow response to metabolic activity
Reactive Hyperemia: redirect flow of blood; cut off blood supply to lower limbs
What are the Local, Myogenic Controls?
vascular smooth muscle responds to increased stretch with increased tone:
- stretch is resisted → vasoconstriction
- decreased stretch results in vasodilation
What is the Result of Myogenic Controls?
tissue perfusion homeostasis so cells not deprived in response to low bp and capillaries not damaged in response to high bp
What are the the Forces that act to influence Capillary Exchange?
(i) most cells in body within 0.02 mm of a capillary → diffusion works
(ii) capillary walls only 1 cell thick: support a mix of diffusional, osmotic & hydrostatic forces
What are the Capillary Bulk Mechanisms?
- Vesicle Transport
- Diffusion
- Bulk Flow
What is Vesicle Transport?
- for relatively large, lipid-insoluble molecules (protein hormones like insulin)
- shuttling via endocytosis, then exocytosis
- antibody molecules from maternal to fetal circulation
What is Diffusion?
- primary mechanism for dissolved solutes & gases (eg: O2, CO2, glucose)
- follow gradients
- heat moves via convection down a thermal gradient
- water-filled pores or fenestrations (Na+, K+, Cl-, glucose) or directly through the bilayer (O2, CO2, urea)
- pores <1% capillary SA; lipid-soluble substances have 100X more SA
What is Bulk Flow?
- this is especially important for fluid movement
- will also carry nutrients and wastes in appropriate direction, but they rely more on diffusion
What does the Overall Deficit of 1-2 mm Hg mean?
This means that some fluid (3-4 ml/min) is lost to the tissues and has to be returned by the lymphatic system
What does Increased Arteriole Pressure mean?
means increased filtration pressure = more fluid loss to tissues (edema)
What does Hemorrhage favour?
hemorrhage favours reabsorption
What is the Role of Lymphatic Vessels?
return up to 3 L of “leaked” fluid plus plasma proteins to the bloodstream
What is the Role of lymphatic tissues / organs?
essential in body to provide defense / resistance to disease
What are Lymphatic Vessels?
begin with microscopic, blind-ended lymph capillaries (called lacteals (pick up fluids & fats we digest to circ. system) when found in intestinal villi)
Where are Lymphatic Vessels found?
everywhere except bones, teeth, bone marrow, and in only limited areas (meninges) in CNS
What do the Flap-Like Minivalves provide?
flap-like minivalves provide spaces in between loosely attached endothelial cells
What is the Purpose of Collagen Filaments?
collagen filaments anchor the endothelial cells to surrounding structures
What happens when fluid pressure builds up in
tissues?
Make lymph capillaries more permeable
- open them up for a bit
- easier for fluid to go into those capillaries
Where does the Right Lymphatic Duct drain from?
Right head, shoulder area, upper limb, thorax area
Where does the Thoracic duct drain from?
Left head, shoulder area, upper limb, thorax area. abdomen
- Both lower limbs
What are Lymph Nodes?
clustered along lymphatic vessels
- larger clusters where lymphatic vessels converge (inguinal, axillary, cervical regions)
What are the two roles of Lymph Nodes?
(i) filter lymph (macrophages; remove & destroy microorganisms)
(ii) activate immune system if anything is found
What are the four Lymphoid Cells?
- Lymphocytes
- Macrophages
- Dendritic Cells
- Reticular Cells
What are Lymphocytes?
- T-cells: manage immune response; some are soldiers
- B-cells: can differentiate into antibody-producing plasma cells
What are Macrophages?
phagocytize foreign substances and can be antigen
presenters
- activate T-cells
What are Dendritic Cells?
antigen presenters
- bring antigens to lymph nodes from skin and mucosal linings
What are Reticular Cells?
fibroblast-like cells that produce the extracellular matrix
network that supports the immune cells
What is the Lymphoid Tissue?
reticular CT: all lymphoid organs except thymus
- in lamina propria of mucous membranes
- macrophages reside in network
- lymphocytes make temporary stopovers in between patrolling body
What are the two roles of Reticular CT?
a) houses and provides proliferation sites for lymphocytes
b) ideal surveillance vantage point for lymphocytes & macrophages
What are Lymph Nodes?
- Lymph nodes are usually bean-shaped
- Filters lymph that is filled with macrophages, T & B cells
- discrete, encapsulated collections of diffuse lymphoid tissue + follicles
- ~2.5 cm long; divided into compartments by trabeculae
What is the significance of fewer efferent compared to afferent lymphatic vessels?
Allowing macrophage to carry out their protective functions
What is the Cortex of Lymph Nodes?
follicles with germinal centres that contain proliferating populations of B cells that have been activated by a foreign antigen
What is the Medulla of Lymph Nodes?
medullary cords (B and T cells found here) & large lymph
sinuses (lymph capillaries) plus network of reticular fibers where macrophages are stationed to police the lymphatic fluid
What are the Other Lymphoid Organs?
- Spleen
- Thymus
- MALT (Mucosa-associated lymphoid tissues)
