L13- Vessels Flashcards
blood vessels can be
Continuous, Fenestrated or Sinusoid
Continuous
- Continuous basement membrane and endothelial layer (tunica intima)
Fenestrated
- Continuous basement membrane
- Fenestrations within endothelial layer
sinusoidal
- Incomplete basement membrane
- Intercellular gap in epithelial layer(discontinuous)
on entering circulation, newly formed RBC travel from
venule intermediate veins larger vein vena cava
RBC matures within
2 days
newly formed WBC
WBCs take the same route at RBC
T cells need to
mature in the thymus and lympathics
B cells
already mature
precapillary sphincters
control flow in microciruclation
when precaipplary spinsters are open
open blood flows freely to capillary bed
- oxygen and nutrient rich blood flows from there arteries, through etc capillaries releasing nutrients and oxygen to the tissue and then into the venule
function of precapillary sphincters
Control fluid exchange between the capillaries and the body tissue
definition of a vein
vein is an elastic blood vessels which transports blood to the heart (right ventricle)
structure of a vein
- wide lumen
- thin wall
- 3 layers: tunica intima, tunica media, tunica externa
- valves
valves in veins
Non return valves (fibroelastic cartilaginous ) assists flow towards the heart
why are valves needed in veins
- Low pressure system
- Relies on muscle contractions to return blood to the heart
- Vein problems occur due to blood clot or vein defect behind the valves
size of veins
Range in size: 1-1.5cm in diameter
smallest type of vein
venule
venules
Receive blood from arterioles and capillaries
venules branch into
larger veins e.g. carry blood to the largest vein in the largest vein in the body
largest vein in the body
the vena cava
- Superior and inferior vena cava drain into the right atrium of the heart
types of vein
- pulmonary
- systemic
- superficial
- deep
pulmonary veins
- Carries oxygenated blood from the lungs to the left atrium of the heart
systemic veins
• Return oxygen depleted blood from the rest of the body to the right atrium of the heart
superficial veins
• Located near the surface of the skin and not located near a corresponding artery (e.g. in hands)
deep veins
• Located deep between tissues and typically located near a corresponding artery with the same name ( e.g. femoral artery and vein)
artery vs vein
- Artery has thicker tunica externa
- Very thin elastic layer in low pressure vein
artery defintiiton
are elastic blood vessels that convert. blood away from the heart
structure of an artery
Small lumen and thicker walls to deal with higher BP.
layers of artery
Consists of 3 main layers:
• Tunica intima- elastic membrane and smooth muscle lining
• Tunica media- smooth muscle and elastic fibres.
o This layer is thicker in arteries than in veins and has two distinct elastic layers
• Tunica externa- strong outer covering composed of collagen and elastic fibres
o Allows arteries to stretch but prevents over expansion due to higher blood pressures than in the veins
capillaries function
supply all cells with their requirements e.g. oxygen and nutrients
- take away waste products
structure of capillaries
very tin cell wall (allow for exchange)
- very narrow lumen (just wide enough for RBC to pass through)
structure of wall in veinsq
- thin
- mainly fibrous tissue
- contains far less muscle and elastic tissue than arteries
why do veins not need strong walls
- most of the BP has been lost
- wide lumen offers less resistance to blood flow
why do arteries have thick, strong and elastic walls
needed to withstand the pulsing of the blood, prevent bursting and maintain pressure wave
- prevents back flow
vasculogenesis
Formation of new blood vessels
- E.g. during embryo development, newly formed cancers and endometriosis
precursors of new blood vessels found
in bone marrow (angioblasts)
angiogenesis
Formation of new blood vessels from existing ones
- E.g. during fetal development, collateral arteries, postnatal lung development
collateral arteries
Arterioles which form a pathway around blockage- protect tissues that may become compromised
why do collateral arteries form
o Chronic diseases such as ischaema
o During development (brain and joints)
the pericyte is a
smooth muskie like cell found inside the basal lamina close to the basement membrane
pericyte is a key component of which blood vessel
capillaries - prevent endothelial cell proliferation
pericyte also involved in
nerve cell communications in the BBB (maintains tight capillaries)
pericytes can differentiate into
endothelial, smooth muscle or fibroblast
