Test

Describe the three layers or tunics of the blood vessel wall.

Tunica intima: innermost layer; composed of endothelium

Tunica media: middle layer of the vessel wall and composed predominantly of circularly arranged layers of smooth muscle cells; supported by elastic fibers

Tunica externa: outermost layer of blood vessel wall; composed of areolar connective tissue; contains elastic and collagen fibers

How do the tunics compare between arteries and veins?

arteries have a thicker tunica media, a narrower lumen, and more elastic and collagen fibers

Veins have a thinner tunica media, thicker tunica externa, a wide lumen, and less elastic and collagen fibers.

What are the three classes of arteries by size? Describe each.

1. Elastic arteries (aorta, common carotid, subclavian, pulmonary trunk, & common iliac arteries)/ expand during systole, recoil during diastole/ bigger tunica media (mostly elastic connective ruse. Recoil when stretched to prevent blood pressure drop)

2. Muscular arteries: distribute blood to specific organs (brachial, femoral, renal, splenic)/ more smooth muscle than elastic/ tunica media is a thick layer of smooth muscle

3. Arterioles: smallest arteries/ control amount of blood to various organs/ smooth muscle usually somewhat constricted/ regulate systemic blood pressure & flow/ regulated by vasomotor center in brainstem/ tunica media is smooth muscle

The smaller the arterioles the more the resistance/ most abundant/ most important/ less resistance more blood to capillary blood, more is the opposite

What are arterioles? What is vasomotor tone?

A small artery. Artery- arteriole- capillary-venule-vein.

Vasomotor tone: They have constant sympathetic feed that keeps them a little contracted.

Describe continuous capillaries, fenestrated capillaries and sinusoids.

Mainly composed of simple squamous and basement membrane

1. Continuous capillaries: endothelial cells have tight junctions (prevent leaking) forming a continuous tube w/ intercellular clefts/ large particles (cells, proteins) cannot pass, smaller molecules (glucose) can pass through wall

Common: found in muscle, skin, lungs CNS

2. Fenestrated capillaries: Endothelial cells form a continuous lining but the cells have fenestrations (pores)/ allow for the movement of smaller plasma proteins/ found in areas where a lot of fluid transport happens

3. Sinusoids: endothelial cells form an incomplete lining w/ large gaps/ opening allows transport of large substances (formed elements, proteins)

Found in bone marrow, spleen, liver, endocrine glands.

What are capillary beds, metarterioles, thoroughfare channels, precapillary sphincters, postcapillary venule, true capillaries, vasomotion and perfusion? Use Figure 20.5

1. Capillary beds: group of capillaries functioning together

2. Metarterioles: a vessel branch of an arteriole/ feeds capillary beds (proximal part encircle by muscle cells)

3. Thoroughfare channel: no smooth muscle, blood always flow through it

4. Pre capillary sphincters; circular muscles; control the size of opening/ if it constricts, no blood goes to capillary bed/ if it is relaxed blood goes/ stimulus is to much acid, Co2, low oxygen to dilate

5. Vasomotor: cycle of contracting and relaxing of pre capillary sphincters

(at one time only one-quarter if body's capillary beds are open)

6. Perfusion: amount of blood entering capillaries per unit per time per gram of tissue/ make sure that the organ or tissue meets its needs

7. Sphincters opens\= perfusion

Define venules, small, medium and large veins. What are systemic vein blood reservoirs?

1. Venules: smallest veins/ companion with arterioles

2. Medium veins: companion w/ muscular arteries/ one to the actual organs, bigger lumen, tunica external thicker, less smooth muscle, muscular

3. Largest veins: travel with elastic arteries (vena cava)/ most veins of these size have numerous valves, similar structure to hearts semilunar valve/ make sure blood flows unidirectional

4. Systemic vein blood reservoirs: 70% of blood is in systemic circulation/ systemic veins (55%)/ most of your blood is in your systemic veins at rest

Describe simple and alternative pathways. What are anastomoses? Describe a portal system.

1. Simple: one major artery delivers blood to an organ or body region and then branches into smaller and smaller arteries to arterioles

Anastomoses: two or more arteries converge to supply some organ/tissue

Venous anastomosis are more commonTwo or moreveins drain same body regionE.g., basilic, brachial, and cephalic veins draining theupper limb38

Arteriovenous anastomosis: transport blood from artery directly to vein/ allow areas to be bypassed if body is hypothermic

portal system: Blood flows through 2 capillary beds, the two beds separated by a portal vein.

Define cross sectional area and describe the relationship of cross section area and blood flow.

Cross sectional area: is one vessel is lumen diameter

Total cross section: sum of diameters of all vessels of a certain type (artery, capillary, vein)

The greater the area/ the smaller the vessel.

Describe blood flow velocity. What is the significance of much slower blood flow through the capillaries?

Is inversely related to total cross-sectional area:Larger area results in slower blood flow

Blood flow is slow in capillaries. Why is this important?

Allows for exchange between blood and tissue fluid

Why is capillary exchange important? Explain the processes of diffusion and vesicular transport between capillaries and tissues, include the substances moved by each process.

Diffusion: substances leave or enter blood according to their concentration gradient (oxygen, hormones, nutrients move from blood to tissue/ CO2 and waste diffuse from tissue into capillaries)

Route diffusion: Depends on particles size

Vesicular transport: Endothelial cells take substances in by pinocytosis (take little vesicles into cell)/ secrete substance from other side by exocytosis (hormones, fatty acids transported this way)

Describe bulk flow, filtration and reabsorption.

Bulk flow: moving fluid down pressure gradient/ large amounts of fluid & dissolved substance move/ movement direction depends on net pressure of opposing forces

Filtration: passive transport; blood pressure (hydrostatic) that forces plasma out of the capillaries (cleft, fenestrations)/ occurs on arterial end

Reabsorption: fluid going back in capillaries/ occurs on venous end. Produces ECF

Define hydrostatic pressure, blood colloid osmotic pressure.

hydrostatic pressure (water pressure/ blood pressure)/ promotes filtration at atrial end colloid osmotic pressure: pull in water due to presence of protein solutes

Define net filtration pressure. Use Figure 20.10 to calculate net filtration pressure at the arterial and venous ends of the capillary. Ignore interstitial hydrostatic pressure and interstitial colloid osmotic pressure.

NFP: Difference between net hydrostatic pressure and net colloid osmotic pressure.

Fluid filters out of the arterial end of capillary and is osmotically reabsorbed at the venous end of the capillary

What is the role of the lymphatic system in capillary exchange? Define edema. Describe its 3 causes.

85% of the blood filtered by capillaries reabsorbed

15% is absorbed by the lymphatic system and returned to the blood.

Edema: Excess tissue fluid. Too much fluid that filtered out and the lymphatic system can not absorb it all.

Increased capillary filtration,

kidney failure,

histamine release,