X. DRAFT/ A&P 2 : Blood vessels & Hemodynamic

Blood vessels

_______________ form a closed system of tubes that carry blood away from the heart, transport it to the tissues of the body, and then return it to the heart

Arteries

carry blood away from the heart. As you get further away from the heart, large elastic vessels divide into medium sized muscular arteries

Arterioles

Small arteries that connect to capillaries

Capillaries

Site of substance exchange between the blood and body tissues

Venules

Connect capillaries to larger veins

Veins

Convey blood from the tissues back to the heart

Vaso vasorum

Small blood vessels that supply blood to the wall of the arteries and veins

Angiogenesis

Growth of new blood vessels

Nevi vasorum

Nerve that supply the blood vessels

1. Tunica interna (intima)

2. Tunica media

3. Tunica externa (tunica adventitia)

What are the 3 layers of blood vessel?

Tunica interna

-innermost layer, adjacent to Lumen=inferior opening of the vessel

-in direct contact with the blood

1. Endothelium

2. Basement membrane

3. Internal elastic lamina (membrane):

Tunica interna has three parts:

Endothelium of tunica interna

the innermost component; lines the inner surface of the entire CVS

Basement membrane of tunica interna

second component; provide resilience for stretching and recoil

Internal elastic lamina (membrane) of tunica interna

Outermost component; With windows like opening Fenestrations —> facilitate diffusion of material

Tunica media

middle layer of blood vessel

Blood flow and BP

Tunica media regulate:

Circular smooth muscle & connective tissue layer

Tunica media has:

Circular smooth muscle of tunica media

"Ring" around the lumen —> regulates the diameter of the lumen

Sympathetic stimulation

What cause vasoconstriction?

Decreased symp. Stimulation, Nitric oxide, H+, lactic acid

What cause vasodilation?

Connective tissue layer of tunica media

Made of elastic fibers

tunica interna (intima), tunica media, tunica externa

The wall of an artery consists of:

Tunica externa (tunica adventitia)

-Outermost layer of blood vessel, adjacent to surrounding tissue

-elastic and collagen fibers

-contain numerous nerves (Nervi vasorum)

Vasa vasorum (self-vessels)

Supply blood to the blood vessels

Elasticity; contractility

The functional properties of arteries are ______________ and _______________

elastic tissue

Elasticity of arteries is due to the _______________ in tunica interna and tunica media, allows arteries to accept blood under great pressure from the contraction of the ventricles and to send it on through the system

Smooth muscle

Contractility is due to the _____________ in the tunica media; allows arteries to increase or decrease lumen size and to limit bleeding from wounds

Sympathetic neurons

___________________ affect the smooth muscle in the tunica media

Elastic arteries

Conducting arteries

-conduct blood from the heart to medium sized muscular arteries

-larger diameter (aorta; pulmonary arteries)

-more elastic fibers (elastic lamellae)

-less smooth muscle

-function as pressure reservoirs by storing mechanical energy and then they can recoil during the diastole phase of the ventricles to push blood into the smaller vessels

What are the characteristic of elastic arteries?

Stretch

Elastic aorta and arteries _________ during ventricular contraction

Recoil

Elastic aorta and arteries _________ during ventricular relaxation

Muscular arteries

distributing arteries

-capable of huge vasoconstriction and vasodilation and can adjust the rate of blood flow

-medium diameter

-smooth muscle > elastic fibers

-function: distribute blood to various parts of the body (organs)

What are the characteristics of muscular arteries?

Anastomoses

-Union of the branches of two or more arteries supplying the same region

-provide alternate routes for blood to reach a tissue or organ

Collateral circulation

Alternate flow of blood to a body part through an anastomosis

End arteries

Arteries that do not anastomose

Necrosis (cell death)

Occlusion of an end artery interrupts the blood supply of a whole segment of an organ, producing _______________ of that segment

Regulate the blood flow into the capillaries network

What's the function of the arterioles?

Resistance vessels

Arterioles are known as _______________

Increase

Vasoconstriction _____________ resistance ——->decreases blood flow to capillaries

Decrease

Vasodilation ______________ resistance——->increase blood flow to capillaries

Resistance

Opposition to blood flow

-determined by the amount of friction between the vessel walls and the blood following through

Microcirculation

Flow of blood through the capillaries

Metabolic activity

Capillaries are found near almost every cell in the body, but their distribution varies with the ______________________ of the tissue

Muscles, liver, kidneys, and NS are high metabolic tissues

Which tissues have more extensive capillary beds?

Tendons and ligaments (that's why sprains and tendinitis can take so long to heal)

Which tissues have few capillaries?

Lens, cornea, and cartilage

Capillaries are absent in some tissues like:

A single layer of cells (endothelium) and a basement membrane

Capillaries walls are composed of:

Exchange of nutrients and wastes since it has thin walls

Capillaries lack tunica media and tunica externa which allows:

Capillaries bed

Extensive capillary network

-increase surface area to allow more rapid exchange of large quantifies of materials

Metarterioles

A transitional vessel between the arterioles and the capillaries

-proximal end: has some smooth muscle that regulate flow into capillary bed

-distal end: empties into venule, no muscle fiber

Bypass

If the tissue has low metabolic demand, the blood can _____________ the extensive capillary network

Precapillary sphincter

Rings of smooth muscle fibers located at the junctions between the metarteriole and the capillaries which regulate blood flow through capillaries

Thoroughfare channel

most direct passageway through capillary bed

Capillary bed

If spinchters are relaxed, blood flowing through _________________

Thoroughfare channel

If sphincters contracted, blood flowing through________________

Vasomotion

An intermittent contraction/relaxation of the precapillary sphincters so that at rest there is still blood flowing through about 25% of the capillary bed

Continuous capillaries

A continuous tube of endothelial cells with intercellular clefts for diffusion to the tissues

-found in skeletal and smooth muscle, connective tissue, lungs

Fenestrated capillaries

Have pores in the endothelial cells for easier diffusion

-found in the kidney, villi in small intestine, endocrine gland, ventricles of the brain

Sinusoid capillaries

Have very large fenestrations. The basement membrane is incomplete or absent altogether and there are enormous intercellular clefts.

-Found in liver, spleen, red bone marrow, endocrine glands

Postcapillary venules

Receive blood from capillaries

-sites of exchange of nutrients and wastes and white blood cell emigration

Muscular venules

Larger venules, have thicker walls across which exchange with the interstitial fluid no longer occur

Thinner; thicker

Veins consists of the same tunics as arteries but have a _______________ tunica interna and media and a ____________ tunica externa

Less

Veins have __________ elastic tissue and smooth muscle and are therefore thinner walled than arteries

Valves

Veins contain ____________ to prevent the back flow of blood, especially in lower limb vein.

Tunica intima; lumen

The cusps of the valve are derived from _____________ and are projecting into ___________

Pumping action of the heart

The ___________________ (major factor) and contraction of the skeletal muscles in the lower limbs are the factors in moving venous blood back to the heart

Vascular (venous) sinuses

Veins with very thin walls with no smooth muscle to alter their diameter, but they act like vein (collect venous blood)

-eg. dural sinuses (cranial cavity), coronary sinus (heart)

Weak valves

-when the valve leaks, the space distal to it gets to back flow of blood that increases the pressure and distends the vein

What lead to varicose veins?

Esophagus, superficial vein of lower limbs, veins in the anal canal

The most common sites for varicose veins are in:

Saphenous vein

_______________is very susceptible, deeper vessels have muscular support that prevent the wall from stretching out

Superficiala vein

Within the subcutaneous layer (superficial fascia) and are mostly used for intravenous injection

-much larger than deep vein in upper limbs and serve the major pathway of venous blood backflow

Small connections (anastomoses)

Superficial veins communicate with deep veins via

Systemic veins and venules

At rest, the largest portion of the blood is in ____________________, collectively called blood reservoirs.

-diffusion

-transcytosis

-bulk flow

Substances cross capillary walls by:

Diffusion

Most important method of capillary exchange

-O2, CO2, glucose, amino acids, hormones...

Blood into the cells

O2 diffuses down the concentration gradient from:

Interstitial fluid into the blood

CO2 diffuse from:

Endocytosis; exocytosis

The enclosing of substances within tiny vesicles that enter endothelial cells by _________________ and move across the cells and exit the other side by ______________ (insulin)

Bulk flow

Passive process in which large numbers of ions, molecules, or particles in a fluid move together in the same direction

higher; lower

Bulk flow occurs from an area of __________ pressure to and area of _____________ pressure, and it continues as long as a pressure difference exists

relative volumes of blood and interstitial fluid

Bulk flow is more important for regulation of the _________________________

Hydrostatic and osmotic pressure

The movement of water and dissolved substances (except proteins) through capillaries is dependent upon ________________________.

Blood hydrostatic pressure (BHP)

Pressure that the water portion of plasma exerts against blood vessel walls

Pushes

Blood hydrostatic pressure (BHP) __________ fluid out of capillary into interstitial fluid

Pulls

Interstitial fluid osmotic pressure (IFOP) ____________ fluid out of the capillaries

Filtration

Pressure-driven movement of fluid and solutes from blood capillaries into interstitial fluid

Blood hydrostatic pressure (BHP) and interstitial fluid osmotic pressure (IFOP)

Which pressure promote filtration?

Reabsorption

Pressure-driven movement of fluid and solutes from interstitial fluid into blood capillaries

Interstitial fluid hydrostatic pressure (IFHP) and blood colloid osmotic pressure (BCOP)

Which pressure promote reabsorption?

Net Filtration Pressure (NFP)

the difference between net hydrostatic pressure and net osmotic pressure

Blood colloid osmotic pressure

A force caused by the presence of large proteins suspended in the plasma that tends to pull fluid from interstitial spaces into the capillaries

Interstitial fluid hydrostatic pressure

________________ opposes BHP to push fluid into capillaries (roughly 0)

Outflow

At the arterial end of the capillary, there is a net _________

lower; lower; inflow

At the venous end of the capillary, blood hydrostatic pressure is much ____________. As a result, the pressures that promote filtration are __________ than the pressures that promotes reabsorption, and there is a net __________.

reabsorbed; lymphatic system

Approximately 85% of what is filtered is ______________ and the excess fluid is picked up by the _________________ and returned to circulation.

Starling's law of the capillaries

Under normal conditions, the volume of fluid and solutes reabsorbed is almost as large as the volume filtered

NFP=(BHP+IFOP)-(BCOP+IFHP)

1. Increase blood hydrostatic pressure in capillaries due to an increase in venous pressure

2. Decreased concentration of plasma proteins that lower blood colloid osmotic pressure

3. Increased permeability of capillaries which allows greater amount of plasma proteins to leave the blood and enter tissue fluid

4. Increased extracellular fluid volume as a result of fluid retention

5. Blockage of lymphatic vessels postoperative or due to filariasis worm infection

What cause edema?