Blood vessels and Lymphatic system Flashcards
What is resting vascular tone?
In resting state, smooth muscles in walls of arterioles are somewhat contracted via the sympathetic NS -> this can increase flow by vasodilation
Controls the diameter of arterioles
R varies 1/r4
- Organs regulate indiv blood flow by varying resistance of arterioles
What is hyperemia? When does this occur?
Hyperemia = increased perfusion of ‘needy’ tissues
Occurs when there are;
- declining tissue levels of oxygen
- increasing levels of co2, adenosine, H+, K+, heat or inflammatory chemicals
- any combination of these leads to a need for an increase in blood flow to those local areas
- this causes relaxation of smooth muscle in the walls of arterioles to help in blood flow
What is actve vs reactive hyperemia?
Active = moving, therefore heart and muscles are working harder
- reponses to an increase in physical/metabolic activity
- larger total blood flow during active, digesting organs and kidneys recieve less while blood flow to skin, muscles ad heart greatly increases
Reactive = temporarily cutting off bloo circulation to areas of your body causing reduced supply in those local areas
- Ex. crossing your legs, cutting off flow to lower limbs, you will need to uncorss you legs after a period of time if you feel them fall asleep (tingly)
- ## cutoff of blood supply leads to accumulation of waste products and a brief period of hyperemia
What are myogenic controls?
- Vascular smooth tissue reponds to increased stretch with increased tone, stretch is thus resisted causing vasoconstriction
- decreased stretch results in vasodilation
- result is tissue perfusion homeostasis → capillaries not damaged in response to high bp
what is an example of myogenic controls ?
When doing yoga when your head is facing down with your body
- as you initially go upside down there is going to be an increase in blood flow into the small vessels associated with the head region
- causes increased stretch, smooth muscle response to stretch is contracting more forcefully
- further causes vasoconstriction so not too much blood enters the head region and moves towards capillary beds
What are the 4 ways something can get across the basement membrane for capillary exchange?
1) diffusion through the membrane
- lipid soluble substances (co2, o2, nitrogen)
- follows gradients
- heat moves via convection down a thermal gradient
2) movement through intercellular clefts
- water soluble substances (ions, glucose)
3) movement through fenestrations
- water soluble substances (glycoproteins)
4) transport via vesicles or caveolae
- large substances (proteins like insulin)
- shuttling via endocytosis, then exocytosis
- antibody molecules from maternal to fetal circulation
What is bulk flow?
Especially important for fluid movement and anything dissolved in it
- carries nutrients and wastes in appropriate direction, but usually relies more on diffusion
What is NFP? how is this calculated?
NFP = net flitration pressure, used to determine the pressure driving the fluid out of the capillary at any given point
Outward pressures (HPc and OPif)
Inward pressures (HPif and OPc)
NFP = (HPc+OPif) - (HPif+OPc)
if nfp = positive → net filtration
if nfp negative → net resorbtion
Describe the lymphatic vessels vs the lymphatic organs/tissues
Vessels = return up to 3L of ‘leaked’ fluid plus plasma proteins to bloodstream
- begin with blind ended lymph capillaries (lacteals when found in instestinal villi)
- everywhere except bones, teeth, bone marrow and only in limited areas (meninges) of CNS
Tissues/organs = essential in body to provide defence/resistance to disease
How are lymph capillaries very permeable?
1) contains flap-like minivalves that provide spaces in between loosely attached endothelial cells
- blind ended (covered at the ends) because they are the starting points
2) collagen filaments anchor the endothelial cells to surrounding structures
What happens when fluid pressure builds up in the tissues (during inflammation/edema)?
It will make lymph capillaries even more permable, if fluid pressure builds up it will open the flaps and make it easier for fluid to move into the lumens of the capillaries
What is the function of lymph nodes?
Larger clusters where lymphatic vessels converge (inguinal, axillary, cervical regions)
1) filter lymph (macrophages; removand destroy microorganisms)
2) activate immune system if anything is found
What are the different types of lymphoid cells?
Lymphocytes = T-cells and B-cells
- T-cells = manage immune response (soldiers)
- B-cells = can differentiate into antibody producing plasma cells
Macrophages = phagocytize foreign substances and can be antigen presenters - activates T -cells
Dendritic cells = antigen presenters, bring antigens to lymph nodes from skin and muscosal linings (informs other immune cells)
Reticular cells = fibroblast like cells, produce the extracellular matrix network that supports the immune cells
What is lymphoid tissue?
All are made of reticular CT except thymus
- houses and provides proliferation sites for lymphocytes
- ideal surveillance vantage point for lymphocytes and macrophages
Why are there fewer efferent compared to afferent lymphatic vessels?
There are more ways for fluid to enter but less to exit which allows forcing of the fluid to slow down
More time for nodes to identify anything bad in the fluid entering
Also note the one way traffic through each lymph node
