Chp 21- Blood vessels

what are the 3 histological layers in an artery?

1. Tunica interna- Endothelium + internal elastic lamina

2. Tunica media- elastic fibers and thick smooth muscle layer

3. Tunica Externa- elastic and collagen fiber

what are Endothelial cells? what do they do?

• release chemicals that

  • reduce friction in blood vessels

  • vasoconstriction

  • vasodilation

  • adhesion of white blood cells

what do arteries near the heart have a lot that other arteries have less?

• Elastic tissue

  • aids in accommodating stroke volume of the heart

what are vaso vasorums?

larger blood vessels that have their own blood supply

Anastomosis

2 structures w/ lumen connect to each other to create alternative pathways

why can collateral circulation a benefit for tissue?

Alternate pathways for blood to reach the tissue when passageway is obstructed by a blockage or narrowing

Description of: Arterioles

• Consists of endothelium, basement membrane, and smooth muscle cells

• pressure of 85-35 mmHg (30mmHg)

• Diameter can change drastically and is controlled by vasomotor center in medulla

• The end of an arteriole that connects to capillary is called a metarteriole

How does the vasoconstriction of arterioles affect blood pressure? what does this mean?

• it increases BP

• This constriction causes more resistance making blood flow more difficult. This means that systemic arterioles are key regulators of blood pressure

Description of: capillaries

• consist of endothelium and a basement membrane

• are involved in the exchange of nutrients and waste between blood and tissue

• 35-15 mmHg pressure

what structures do not have capillaries ?

• epithelium

• hyaline cartilage

• cornea

• lens

Continuous capillaries

• Located between cells

• Allows for control of what comes in and out of blood

• Held by tight junctions

• least permeable

• located at the skin and muscle

Fenestrated capillaries

• Located at cells with small pores

• At kidneys and small intestine

• Allows for rapid exchange of water and solutes between blood and interstitial fluid, pores do the filtering

Sinusoid capillaries

• located large intracellular cleft

• At bone marrow, liver, spleen

• Extremely leaky spaces, most permeable

• Allows free exchange of water and solutes

how does blood flow through capillaries

• Blood flow is intermittent

• Regulated by capillary sphincters (vasomotion) at metarterioles

• local tissue conditions (like low O2, high CO2, low pH, temperature increases) determine if the sphincters open allowing blood into capillary bed

what is the speed of blood flow at capillaries? what determines speed in a blood vessel?

• Blood flow is the slowest at capillaries to allow exchange

• speed of blood flow is inversely proportional to the total cross section of vessels

Description of: veins

• Tunica media is thinner than an artery

• Tunica externa is thicker in order to hold veins open by connecting to surrounding structures. contains smooth muscle.

• Tunica intimas has no elastic membrane and has few elastic fibers. simple squamous epi.

• Valves- prevents back flow

• 15-5 mmHg pressure

what helps aid in venous return to the heart?

• Valves: covered by endothelium, prevents back flow

• Skeletal muscle: squeezes blood past valves

• Breathing: changes thoracic pressure assisting in flow back to heart

what are venous sinus? what are two examples?

• A vein that lacks smooth muscle in the wall, no tunica media. Flat and easily distended

• Superior sagittal sinus and coronary sinus

what is blood pressure?

• force of blood (hydrostatic pressure) on the wall of a blood vessel

• measured in mmHg

• commonly taken at brachial artery

what is systolic pressure?

pressure of the artery when ventricles contract and pump stroke volume into the artery

what is diastolic pressure

pressure in the artery when it recoils and relaxes

what 6 factors affect blood pressure?

1. blood volume

2. cardiac output

3. chemoreceptors

4. baroreceptors

5. peripheral resistance

6. hormones

how does blood volume affect blood pressure?

the higher the volume, the higher the blood pressure

what is cardiovascular center? where is it located?

• Adjusts sympathetic and parasympathetic effects on circulatory system

  • sympathetic increases heart rate and force of contraction, promotes vasoconstriction of systemic arterioles

• located in medulla oblongata

how does cardiac output affect blood pressure

Cardiac output deals with the amount of blood being bumped out the left ventricle in 1 minute, so the more blood being pumped out, the higher the blood pressure

how does chemoreceptors affect blood pressure? where are they located?

Chemoreceptors detect O2, CO2 and H+. So if hypoxia is detected (low O2 in tissue), blood pressure increases to get O2 to the tissue

located in carotid bodies and aorta

how do baroreceptors affect blood pressure? where are they located?

• low pressure inhibits baroreceptors to detect pressure changes. they send impulses through glossopharyngeal and vagus nerve to send to cardiac centers to stimulate sympathetic nervous system to increase blood pressure

• located at carotid sinus

how does peripheral resistance affect blood pressure

• the greater the resistance, the harder it is for blood to pump, the higher the blood pressure.

• 3 factors effect this:

  • vasomotor tone (diameter of a blood vessel) is proportional to this idea. 1/diameter⁴

  • If blood is thicker (higher viscosity), it has a harder time flowing, therefore increasing blood pressure

  • the longer the blood vessel, the harder it is for blood to travel, the higher the blood pressure

how do hormones affect blood pressure

• Aldosterone= water follows salt, higher blood volume, higher blood pressure

• epinephrine also increases blood pressure

pulse pressure equation? what does pulse pressure mean?

• Caused by the expansion and recoiling of an artery. When it is higher it means a greater difference between systole and diastole

• depends on stroke volume and elasticity of blood vessels

• systolic pressure - diastolic pressure

mean arterial pressure equation

diastolic pressure - pp/3

*always closer to diastole becuase heart spends more time in diastole than systole

what is capillary exchange? why is it done at the capillary?

• nutrient exchange

• contains thin layer of simple squamous epithelium and basement membrane, regulated by pressure (hydrostatic and osmotic)

what is hydrostatic pressure? what is it in arterioles and veins?

• the pressure of the fluid inside pushing out

• arterioles: 30 mmHg

• veins: 15-18 mmHg

what is osmotic pressure?

• the pressure of pulling water into a capillary due to albumin and Na+ in blood

• Albumin does not leave capillaries so osmotic pressure stays constant around 22-25 mmHg

if at an arteriole end, 30 mmHg hydrostatic pressure and 22mmHg osmotic, how much is being pushed out?

8 mmHg pushed out

if at an venous end, 15 mmHg hydrostatic pressure and 22mmHg osmotic, how much is being pulled in?

7 mmHg pulling in

how does the nutrient exchange occur?

• fluid leaves out the capillary at the arteriole end and reenters at the venous

• nutrients are carried out the the arteriole end and waste products enter thought the venous

• water (and small substances) pass through capillary membrane in bulk flow

• more fluid leaves than reenters, albumin can leak out

basic functions of lumphatic system

1. immune functions (ex. Peyer’s patches)

2. fat absorption (ex. lacteals)

3. draining interstitial fluid (ex. capillary exchange)

what is edema? what causes it?

• increased amount of interstitial fluid that causes body to swell

• can be caused by

  • increase in venous hydrostatic pressure. this stops blood from being able to flow through and limits the capillary exchange

  • decrease in albumin causes a decrease in osmotic pressure

  • increase in capillary permeability, can cause albumin to leak out

  • lymph drainage blocked

what is pulse? where is it measured? why?

• elastic arteries expand and recoil with systole and diastole

• measured at an artery because pulse is created by the stroke volume enetering the aorta and sent to the arteries

pulse points

• temporal

• common carotid

• brachial

• femoral

• popliteal

• posterior tibial

• dorsalis pedis arteries

systtemic circulation

1. left ventricle

2. aorta

3. body

4. superior, inferior vena cava, coronary sinus

5. right atrium

pulmonary circulation

1. right ventricle

2. pulmonary artery

3. lungs

4. pulmonary vein

5. left atrium

hepatic portal circulation

1. aorta

2. superior mesenteric artery

3. capillaries in villus (bed 1)

4. superior mesenteric vein

5. hepatic portal vein

6. liver sinusoid (bed 2)

7. central vein

8. hepatic vein

9. inferior vena cava

circle of willis—

• brain is supplied with branches of arteries

• 4= anterior and posterior cerebral

where does the umbilical artery carry blood from?

-takes deoxygenated blood away from fetus

what is the foramen ovale? what does it become?

• connects the right atrium to the left atrium because fetal lungs do not function

• becomes fossa ovalis

what is the ductus arteriosus? what does it become?

• connects pulmonary artery to aorta

• becomes ligamentum arteriosum

what is shock?

inability of the cardiovascular system to supply organs of the body with adequate oxygen and nutrient

what is hypovolemic shock?

loss of blood, inefficient amount of blood

what is neurogenic shock?

vasodilation of arteries that leads to server decrease in blood pressure

what is septic shock?

infection w/release of toxic substance

causes vasodilation and increase in capillary permeability

what is obstructive shock?

something is obstructing the heart from pumping

what is anaphylactic shock?

vasodilation of arterioles

what is cardiogenic shock?

heart faliure, heart stops pumping

stages of shock: compensated

• increases sympathetic nervous system stimulation

• increase in blood pressure

• pallor skin, sweating

• decrease in urine production

• increase in blood pH, hyperventilation= less CO2= less H+

stages of shock: decompensated

• cardiovascular system can no longer maintain sufficient cardiac output

• decrease in blood pressure

• heart rate increases

stages of shock: irreversible

damage to major organs

ways to treat high blood pressure

1. diuretics= decrease blood volume via increasing urine production

2. beta-blockers= decreases cardiac output by blocking effects of epinephrine and norepinephrine (sympathetic NS)

3. vasodilators- decrease peripheral resistance by increasing arteriole diameter