4 - Blood Vessels Flashcards
Describe layers of blood vessel wall
1) Tunica Externa: Connective tissue
2) Tunica Media: smooth muscle, allowing vasoconstiction and dilation
3) Tunica Intima: smooth muscle
What are the 5 types of capillary bases
1) Continuous
2) Fenestrated
3) Sinusoidal
4) Sinusoids
5) Venous Sinuses
Continuous Capillary (function and location)
1 – Continuous: No gaps between endothelial cells. No fenestrae. Less permeable to large molecules. E.g. muscle and nervous tissue.
Fenestrated - function + location
2 – Fenestrated. Have pores, numerous fenestrae. Highly permeable. E.g. intestinal villi, glomeruli of kidney.
Sinusoidal - function + location
3 – Sinusoidal: large in diameter with large fenestrae. Less basement membrane. E.g. endocrine glands (large molecules cross their walls)
Sinusoids - function + location
4 – Sinusoids: large diameter. Sinusoidal capillaries. Sparse basement membrane. E.g.. liver, bone marrow.
Venous Sinuses - function + location
5 – Venous sinuses: Similar structure to sinusoids but even larger. E.g. spleen
What is fenestrae?
- FENESTRAE: are areas where cytoplasm is absent and plasma membrane is made of thin, porous diaphragm.
▪ Define vasoconstriction and vasodilation
▪ Vasoconstriction: smooth muscles contract, decreasing blood flow.
▪ Vasodilation: smooth muscle cells relax and increase blood flow.
▪ Define the term vasa vasorum
Vasa Vasorum: blood vessels that supply the walls of the arteries and veins. Penetrate the vessel walls from the exterior, branches of the arteries.
▪ Define the term portal veins
Portal Veins: Veins that begin in a primary capillary network, extending some distance and end in a secondary capillary network without a pumping mechanism.
What type of nerve fibres are blood vessels innervated by?
Sympathetic fibres
Arterial changes that occur with age
Arteriosclerosis: degeneration changes in arteries, making them less elastic.
Atherosclerosis: depiction of plaque on walls
How does odema occur?
Odema occurs when capillary walls become permable and allow proteins to leak from the capillary into its instersitial fluid
What are the factors effecting blood flow
- Blood pressure
- Flow
Resitance
What is blood pressure
force exerted by blood against vessel wall
What is blood pressure measured by?
Korotkoff sounds
What is normal blood pressure
120/80
How do you calculate flow?
P1-P2 (P represents a specific point in a unit of time)
How is a Korotoff sound produced?
By TURBULANT flow
What is laminar flow?
Streamlined flow - outermost layer is the slowest and innermost is the fastest
What is turbulant flow
Interupted flow due to rpughened surface (e.g. from a pressure cuff)
What is Poiseluilles law?
Flow increases when resistance increases (e.g. when exercising)
How does viscosity effect bloodflow pressure
Viscosity increases blood flow pressure
What is critical closing pressure
A pressure at which a blood vessel collapses and blood flow stops
What is Laplace’s Law
Force acting on blood vessel is proportional to diameter of vissel x blood pressure
What is vascular compliance?
Blood vessel volume increases as pressure increases
What is pulse pressure?
Increases when stroke volume increases or vascular compliance decreases. Compliance decreases with age
What are the pressures involved in fluid exchange across capillary walls?
1) Capillary Exchange
2) Net Filtration Pressure
What do baroreceptors do?
Detect changes in blood pressure, and if low = will cause increased sympathetic stimulation of blood vessels = vasoconstiction
What do chemoreceptors do?
Monitor blood O2, CO2 and pH levels of blood.
What is the CNS ischemic response?
Due to high CO2 or low pH levels
What happens in the renin-angiotensingen mechanism?
Decreased blood pressure = results in increased H2O reabsoption, decreased urine volume = increased blood pressure.
What happens in the ADH mechanism
Osmoreceptors detect changes in osmolarity
Baroreceptors detect changes in blood pressure
> ADH secretion
= increase Blood volume and increased blood pressure
What is the atrial natriuretic mechanism?
Osmorecptors = detect increased osmotic pressre
Baroreceptors detect decreased BP
= ADH secretion
= Increased BV and BP
