CH 19 Cardiovascular system: Blood vessels

List the begining and end of the bed capillary?

1. Starts at terminal arteriole, that is feeding the bed 2. Leads into metarteriole which is continous with the thoroughfare channel. 3. This channel joins the postcapillary venule that drains the bed.

Define vasomotion

Blood flow through the capillary is slow and intermittent

Define vascular shock

Blood volume is normal, circulation is poor as a result of abnormal expansion of vascular bed caused by extreme vasodilation

What vessel does blood flow slowest?

capillaries

Define capillary beds? What 2 vessel types does it consist of?

Capillaries don't function as individuals. Instead they form interweaving capillary beds. 2. Consist of: A. vascular shunt- short vessel that directly connects the arteriole and venule at opposite ends of bed B. true capillaries- actual exchange vessels

Study these two tables

pg 708 19.9 and pg 709 19.2

define cardiogenic shock

pump failure, occurs when heart is so inefficient that it cannot sustain adequate circulation.

Define circulatory shock?

Any condition in which blood vessels are inadequately filled and blood cannot circulate normally.

What vessel does blood flow fastest?

Aorta

Name the function of baroreceptors in cartoid sinus reflex and aortic reflex.

Baroreceptors taking part in the cartoid sinus reflex protect the blood supply to the brain, whereas those activated int the aoric reflex help maintain adequate blood pressure in the systemic circuit.

Define Mean arterial pressure and describe its equation?

1. Pressure that propels blood to tissues 2. Diastole lasts longer than systole, so MAP is roughly equal to diastolic pressure plus 1/3rd of pulse pressure.

Describe the capillaries and their function

1. Are the smallest blood vessels 2. Have thin walls that have ONLY tunica intima 3. Diameter is just large enough for RBC to go through 4. Their function is to exchange materials, gas, nutrients, hormone and so on.

List the 3 major types of blood vessels

1. Arteries 2. Capillaries 3. Veins

In the pulmonary circuit, what kind of blood does artery and veins carry?

1. Arteries carry O2 poor blood 2. Veins carry O2 rich blood

In the systemic circuit, what kind of blood does artery and veins carry?

1. Arteries carry O2 rich blood 2. Veins carry O2 poor blood

Describe the large arterioles and their function.

1. Arterioles are the Smallest of the arteries 2. Large arterioles, have all 3 tunics and tunica media is smooth muscle.

Why are veins called blood reservoirs?

1. Because veins have large lumen and thin wall they can keep more blood. 2. 65% of the bodys blood supply is found in veins

Why is low capillary pressure desired?

1. Capillaries are fragile and high pressures would rupture them. 2. Most capillary are extremely permeable, so even low pressure forces solute-containing fluids out of blood stream into interstitial space.

Describe the functions of tissue perfusion

1. Deliver O2 and nutrients, and removal of wastes from, tissue cells. 2. Gas exchange in the lungs 3. absorb nutrients from digestive tract 4. urine formation in the kidneys

Describe the muscular (distributing) arteries and their function?

1. Deliver blood to specific body organ

List the 4 routes for molecules to get across capillaries

1. Diffusion through membrane 2. Movement through intercellular clefts (H2O soluble substance) 3. movement through fenestrations (H2O soluble substance) 4. Transport via pinocytotic vesicle or caveolae (large substance)

Describe elastic (conducting) arteries and their function

1. Elastic fibers are thick wall arteries near the heart, aorta and major branches 2. They are the pressure reservoirs expanding and recoiling as heart contracts. 3. Because of Large lumens, they are low resistance pathways that conduct blood from heart.

What is the function of the Tunica externa? What is it made up of?

1. External layer 2. Composed of large, loose woven collagen fibers that protect/reinforce the vessel.

MAP example: List the equation for a person with systolic pressure: 120mm and diastolic pressure 80mg.

1. Find out pulse pressure, difference between systolic and diastolic pressure. 120-80=40 2. Plug it into this equation. MAP=Diastolic pressure + Pulse/3 3. So, MAP=80 + 40/3= 80+13.3=93.3

Define hydrostatic pressure

1. Force exerted by fluid pressing against a wall

Define intercellular clefts? Which capillary type is complete?

1. Gaps of unjoined tight junction membrane. Are large enough to allow limited passage of fluids/small solutes 2. Brain capillary

Define sinusoidal capillaries? What do they allow?

1. Highly modified, leaky capillary found only in the liver, bone marrow, spleen, adrenal medulla 2. Usually fenestrated, has large intercellular clefts 3. Allow large molecules and even blood cells to pass between the blood/surrounding tissues.

Name the 2 factors that reflect Arterial BP?

1. How much the elastic arteries close to the heart can be stretched 2. The volume of blood forced into them at anytime.

Describe the vena cavae and its function?

1. Its the largest vein and the tunica externa is further thickened by longitudinal bands of smooth muscle. 2. Its function is it returns blood directly to the heart.

What is common cause of vascular shock?

1. Loss of vasomotor tone due to anaphylaxis, a systemic allergic reaction in which body wide vasodilation is triggered by the massive release of histamine. 2. other causes: failed autnomic nervous system and severe bacterial infection, septic shock

What are the 2 main goals of neural controls of peripheral resistance? Give examples

1. Maintaining adequate MAP by altering blood vessel diameter Ex. Under conditions of low blood volume, all vessels except those supplying the heart and brain are constricted to allow as much blood as possible to flow to the 2 organs. 2. Altering blood distribution to respond to specific demands of various organs Ex. During excercise, blood is temporarily shunted from digestive organs to skeletal muscles

Describe the vasomotor center and its function

1. Neural center that oversees changes in the diameter of blood vessels 2. Is a cluster of neurons in the medulla.

Define resistance and list 3 sources of resistance?

1. Opposition to flow and is a measure of the amount of friction blood encounters as it passes through the vessels. AKA peripheral resistance 2. Blood viscosity, vessel length, vessel diameter

Describe the small arterioles

1. Small arterioles lead into cappillary beds, are a single layer of smooth muscle cells.

What is the function of the Tunica intima? What is it made up of?

1. The innermost layer. 2. Contains endothelium, lines all lumen cell walls 3. Forms slick surface that minimizes blood friction

What adaptations do veins have to ensure blood is returned at same rate of speed as it was pumped?

1. The large lumen diameter: has very little resistance on BP. 2. The Venous valves

What is the function of Tunica Media? What is it made up of?

1. The mid layer 2. Responsible for maintaining bp and continuous blood circulation by Vasoconstriction or Vasodilation 3. Made up of smooth muscle and sheets of elastin, that contract during the above^^^

Describe venous valves and their function?

1. The prevent blood from flowing backward and resemble semilunar valves in function and structure. 2. They are formed from folds of tunica intima. 3. Most abundant in veins of limbs.

Learn these 2 concepts

1. The pumping action of the heart generates blood flow. 2. Pressure results when flow is opposed by resistance.

Describe the larger venules?

1. They have 1 or 2 layers of smooth muscle cells (scanty tunica media) 2. have thin externa wall

Describe the 3 layers that typically form the wall of a blood vessel?

1. Tunica intima 2. Tunica media 3. Tunica externa

Describe diastolic pressure.

1. When aortic pressure drops to its lowest level. 2. Happens during diastole, aortic valves close to prevent back flow. Walls of the aorta recoil and maintain enough pressure so blood continues forward into smaller vessels.

List the 3 functional adaptations that are important to venous return

1. muscular pump (most important adaptation) 2. respiratory pump 3. Smooth muscle

Define fenestrated capillaries? Where are they found

1.Similar to continuous, except the endothelial is riddled with oval pores aka fenestrations. 2. Much more permeable to fluids and solutes than continuous. 3. Special locations like the kidney and small intestine 4. Found where active capillary exchange occurs

T or F: Blood pressure in veins is low? Is the tunica externa thick or thin?

1.T 2. Thick

Describe the small venules?

AKA the postcapillary venules, consist of endothelium in which pericytes congregate. 2. They're extremely porous, fluid/WBC move through the bloodstream these walls.

What does interstitial hydrostatic pressure do?

Acts outside capillaries and pushes fluids in.

Describe smooth muscle

Adaptation for venous return Layer of smooth muscle around the veins that constricts under sypathetic control, increases venous return.

Describe systolic pressure peak.

As left ventricle contracts and sends blood into aorta, it stretches the elastic aorta as aortic pressure reaches its peak.

Describe the way blood moves

As the heart contracts 1. Forces blood into large arteries leaving the ventricles 2. Blood goes to smaller arteries 3. Then goes to arterioles that feed into Capillary beds of body organs/tissue 4. Blood is drained from capillary into venules 5. Then into larger veins that ultimately empty blood in the heart

Define auto-regulation

Automatic adjustment of blood flow to each tissue in proportion to the tissues requirements at any instant.

Describe the muscular pump

Consists of skeletal muscle As this muscle contracts and relax, they "milk" blood toward the heart. Once blood passes each successive valve it can't flow back.

Describe pulse pressure

Difference between systolic and diastolic pressure

Describe the pulse pressure

Difference between systolic and diastolic pressure. S-D

What does capillary hydrostatic pressure do?

Forces fluid through the capillary walls (filtration), leaving behind cells and protein.

Why is slow capillary blood flow beneficial?

It allows for adequate time for exchanges between blood and tissue

Define diffusion

Movement alway occurs along a concentration gradient , high to low pressure

Describe the respiratory pump

Pressure changes occurring in the ventral body cavity during breathing create the respiratory pump that moves blood up towards heart.

What is key to dealing with hypovolemic shock?

Replace fluid volume as quickly as possible

Define hypovolemic shock

Results from large scale loss of blood, as might follow acute hemorrhage, severe vomiting or diarrhea or extensive burns.

Continuous capillaries are most abundant in?

Skin and muscles and are the most common.

What are the major determinants in peripheral resistance?

Small diameter arterioles, can enlarge and constrict which respond to chemical and neural controls.

Describe the relationship between blood vessel diameter and resistance

Small the tube the greater the resistance. Larger tube less resistance.

Define blood pressure

Systemic arterial BP in the aorta. It is the pressure gradient-difference in BP within vascular system- provides driving force that keeps blood moving. Always from area of high to low BP in body.

T or F: Venous BP is steady and changes very little during cardiac cycle.

T

Define microcirculation?

The flow of blood from an arteriole to a venule, that is through the capillary bed.

Describe the relationship between blood vessel length and resistance.

The longer the vessel the greater the resistance.

What acts as a valve to regulate blood flow into the capillary?

The precapillary sphincter.

What are the base components of the capillary beds?

The true capillaries

What are vasomoter fibers used for?

The vasomotor center transmits impulses at a steady rate along these sympathetic efferents.

Define blood flow

The volume of blood flowing through a vessel, organ, or entire circulation in given period.

How are venules formed?

They are formed when capilliaries unite.

How are veins formed?

They are formed when venules unite.

Define Pericytes

They are spider shaped smooth muscle like cells that stabilize the capillary wall and help control capillary permeability.

Describe the function of arteries

They carry blood away from the heart

Describe the function of veins

They carry blood to the heart

T or F: Muscular arteries have thickest tunica media of all vessels?

True

What tunic has the most elastin?

Tunica media

Describe vasomotor tone

Where arterioles are always in a state of moderate constriction

Is capillary blood pressure the same as capillary hydrostatic pressure?

Yes