Chapter 21 Blood Vessel And Hemodynamics

Front 1

Five Main Types of Blood Vessels

Back 1

1) Arteries

2) Arterioles

3) Capillaries

4) Venules

5) Veins

Front 2

Artery Characteristics

Back 2

** Vessel that transports blood away from the heart

** Carries oxygenated blood to body (except pulmonary arteries)

** Artery circulates blood under high pressure and is thick-walled with a smaller lumen

Front 3

Capillary Characteristics

Back 3

** Thin narrow wall blood vessel located in tissues

** Site of exchange substances between blood and tissue cells

Front 4

Vein Characteristics

Back 4

** Vessel that transports blood toward the heart

** Carries deoxygenated blood from body to the heart (except pulmonary veins)

** Vein circulates blood under low pressure and is thin-walled with uni-directional valves which prevent back flow of blood and a large white lumen

** Lacks internal or external elastic laminae

Front 5

Three Tunics (Layers) of the Vessel Wall

Back 5

From inside to outside: Nearest the lumen

1) Tunica Interna

2) Tunica Media

3) Tunica Externa

Front 6

Vasoconstriction

Back 6

** Occurs when Smooth muscle in tuncia media contracts

Front 7

Vasodilation

Back 7

** Occurs when Smooth muscle relaxes

** The diameter of the lumen affects blood flow through vessel and resistance in the vessel

Front 8

Wall of an Artery

Back 8

** All three layers are present; Has very thick tunica media

** Their wall stretch or expand easily without breaking

** Aorta has thickest wall

Front 9

Wall of a Vein

Back 9

** All three layers are present; Wall is much thinner, but Lumen is larger

** Valves are extensions of Endothelium

Front 10

Wall of Capillary

Back 10

** Diameter of lumen: 5-10 micrometers

** Wall is very thin and lacks both tunica externa and media

** Contain Endothelium and Basement membrane

** Perfect for rapid exchange of material

Front 11

Two types of Arteries

Back 11

** Their classification is based on predominant tissue in Tunica Media

Types: 1) Elastic and 2) Muscular arteries

Front 12

Elastic Conducting Arteries

Back 12

** Largest diameter, wall 1/10 total diameter

** Thick tunica media with mostly elastic fibers which give the arterial wall the ability to stretch

** Function as a pressure reservoir; it moves blood forward while ventricles are relaxed

Front 13

Muscular Distributing Arteries

Back 13

** Medium sized; 1/4 of total diameter

** Tunica Media contains more smooth muscle and fewer elastic fibers; Distribute blood to organs

** Stronger vasoconstriction/vasodilation to Adjust rate of blood flow and Maintain vessel pressure

Front 14

Three types of Capillaries (Exchange Vessels)

Back 14

1) Continuous

2) Fenestrated

3) Sinusoidal

** Microscopic blood vessels of tissues where exchange of nutrients and waste products occur

Front 15

Continuous Capillary

Back 15

** Endothelial cells form a continuous tube; that are found in CNS, Muscle tissue, Skin, and Lungs

** Intercellular clefts are spaces between neighboring endothelial cells

Front 16

Fenestrated Capillary

Back 16

** Plasma membrane of endothelial cells have many fenestrations (small pores)

They are found in: Kidneys, Villi of Small intestines, Choroid plexuses in ventricles of brain, Cilliary processes of Eye ...

Front 17

Sinusoidal Capillary

Back 17

** Widest capillaries; endothelial cells have large fenestrations and intercellular clefts

** Basement membrane is absent or incomplete

** They are found in: Red bone marrow, Liver, Spleen ...

Front 18

Capillary Bed

Back 18

** Network of 10-100 capillaries that arises from single Metarteriole (terminal end of Arteriole)

** Structures involved: Precapillary sphincter, Arteriole, and Venule

Front 19

Precapillary Sphincter

Back 19

Located in metarteriole regulates blood flow from Arteries to Capillaries

Front 20

Arteriole and Venule

Back 20

Arteriole: Delivers oxygenated blood to capillary bed; Stays dilated and active

Venule: drains deoxygenated blood from capillary bed

Front 21

Capillary Exchange

Back 21

** Exchange of oxygen, nutrients, and waste products occurs between blood and interstitial fluid in capillary bed

Three types of Methods of capillary exchange:

1) Diffusion

2) Transcytosis

3) Bulk Flow

** Excess filtered fluid drains into Lymphatic capillaries

Front 22

Diffusion

Back 22

** Most important method of exchange

** Movement of substances from High to Low concentration

** Substances transported are:

Oxygen, Carbon dioxide, Glucose, Amino acids, and Steroid hormones

Front 23

Transcytosis

Back 23

** Has enclosure of a substance within a vesicle

** Movement of vesicle through endothelial cell via Endocytosis and exit through Exocytosis

** Substances transported are large proteins such as Insulin

Front 24

Bulk Flow

Back 24

** Movement of water with Solutes from Higher pressure to Lower pressure

** Important for regulating the volume of blood and interstitial fluid

** Has two types:

1) Filtration: Solutes and fluid move from blood capillaries into interstitial fluid

2) Reabsorption: Solutes and fluid move from interstitial fluid to blood capillaries

Front 25

Starling's Law of Capillaries

Back 25

WHAT GOES IN MUST COME OUT

* Filtration is greater than reabsorption

Front 26

Four pressures that drive Bulk Flow

Back 26

1) Blood Hydrostatic Pressure (BHP)

2) Interstitial Fluid Hydrostatic Pressure (IFHP)

3) Blood Colloid Osmotic Pressure (BCOP)

4) Interstitial Fluid Osmotic Pressure (IFOP)

Front 27

Blood Hydrostatic Pressure (BHP)

Back 27

** Outward Pressure exerted by blood on wall of Capillary

** It pushes fluid out of capillaries into interstitial fluid

** Blood always flow from high to low pressure

Front 28

Interstitial Fluid Hydrostatic Pressure (IFHP)

Back 28

** Pressure exerted by interstitial fluid; which is pushed back into capillaries

** Has an inward force exerted by fluid in interstitial space

Front 29

Blood Colloid Osmotic Pressure (BCOP)

Back 29

** An inward pulling force exerted by Solutes that are dissolved in Plasma

** It pulls fluid from interstitial fluid into blood

Front 30

Interstitial Fluid Osmotic Pressure (IFOP)

Back 30

** An outward pulling force exerted by Solutes dissolved in interstitial space

** It pulls fluid from blood into interstitial fluid

Front 31

Net Filtration Pressure (NFP)

Back 31

** Balances of pressures

NFP= Outward force - Inward force

Pressures promoting filtration - reabsorption

which equals (BHP + IFOP) - (BCOP +IFHP)

Front 32

Net Filtration Pressure at Arteriole End of Capillary

Back 32

Net bulk flow is outward: Filtration

Example: (BHP + IFOP) - (BCOP + IFHP)

35+1 - 26+0 NFP= 10mmHG

Front 33

NFP at Venular End of Capillary

Back 33

** Net bulk flow is inward: Reabsorption

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

Example on paper

Front 34

Hemodynamics of Blood Flow

Back 34

** Blood flow: Volume of blood flowing through a tissue per minute (mL/min)

** Factors that affect blood: 1) the pressure difference and 2) the resistance to blood flow

Front 35

Blood Pressure

Back 35

** Pressure exerted by blood on the walls of blood vessels

** Contraction of ventricles generates blood pressure

** The greater the pressure difference > more blood flow

Front 36

Peripheral Resistance

Back 36

** The opposition to blood flow due to friction between blood and wall of blood vessel

** The greater the resistance > less blood flow

Front 37

Effect of Blood Pressure on Blood Flow

Back 37

** Blood flows from region of higher pressure to lower pressure

** The greater the pressure difference > more blood flow

** Highest pressure in Aorta and Large systemic arteries

** As blood flow farther from heart, BP falls; It is zero when blood flow into right ventricle

Front 38

Arterial BP

Back 38

** Systolic BP: Pressure measured in an artery during Ventricular Systole

** Diastolic BP: Pressure measured in an artery during Ventricular Diastole

** In a resting adult: 110/70 mmHG

Front 39

Pulse Pressure (PP)

Back 39

** Reflects difference between systolic and diastolic blood pressure

PP= Systolic BP - Diastolic BP

Example: BP is 110/70

So pulse pressure= 110-70 = 40 mmHG

Front 40

Mean Arterial Blood Pressure

Back 40

** An average blood pressure in arteries

** MABP = Diastolic BP + 1/3 (PP)

** MABP = 70 + 1/3 (110-70) = 80 mmHG

Also: MABP= CO x R

R stands for resistance

Front 41

Vascular Resistance (R) MABP

Back 41

** Vascular resistance depends on: Diameter of blood vessel, Blood Viscosity, Blood vessel length**

** Size of the lumen of blood vessel affects resistance

** Viscosity of blood mostly depends on ratio of RBCs to plasma, and to smaller extend on the concentration of proteins in plasma

Front 42

Venous Return

Back 42

** Amount of blood returning to the heart through Systemic veins per minute

Occurs because of:

* Pressure generated by left ventricular contraction

* Skeletal Pump and Respiratory Pump

** Venous return should be equal to Cardiac output

Front 43

Venous Return and Pressure Difference

Back 43

** Pressure in venules: 16 mmHG

** Pressure in right heart: 0 mmHG

**** Blood always flows from regions of higher pressure to regions of lower pressure

Front 44

Venous Return and Skeletal Pump

Back 44

** Standing at rest, both venous valves are open >> Blood flows upward toward heart

** Contracting leg muscle pushes blood through proximal valve (open) and closes distal valve

** After relaxing leg muscle, proximal valve closes and distal valve opens due to higher pressure in foot than in leg

Front 45

Venous Return and Respiratory Pump

Back 45

** During inhalation, Diaphragm move downward which INCREASE pressure in Abdominal cavity and DECREASE pressure in Thoracic cavity

** During exhalation, the valves in veins prevents backflow of blood which is downward movement

Front 46

Role of Cardiovascular Center in Regulating Blood Pressure

Back 46

** Located in Medulla Oblongata

** It regulates heart rate, stroke volume, blood pressure ...

Front 47

Parasympathetic Effects on Blood pressure

Back 47

** Parasympathetic stimulation >> Transmitting impulse through Vagus nerve >> which Decreases the activity of SA and AV nodes >> Decreases HR, CO, and BP

Front 48

Sympathetic Effects on Blood pressure

Back 48

** Two types Sympathetic nerves arise from Cardiovascular center:

** 1) Cardiac accelerator nerves: Heart

** 2) Vasomotor nerves: Blood vessels

Front 49

Cardiac Accelerator Nerves

Back 49

** Sympathetic stimulation >> Increases activity of SA and AV nodes >> which Increases HR, CO, and BP

** It also increases contractility >> which increases SV, CO, and BP

Front 50

Vasomotor Nerves

Back 50

** Sends signals to Smooth muscle in Arterioles especially in Skin and Abdominal Viscera

** Sympathetic Simulation: Smooth muscle contracts >> Vasoconstriction >> Increases resistance >> which increases BP

** Sympathetic Inhibition: Smooth muscle relaxes >> Vasodilation >> Decreases resistance >> which decreases BP

Front 51

Neural Regulation of BP

Back 51

** Nervous system regulates BP as two types of reflexes:

** Baroreceptor reflex: Activated when BP changes in large arteries

** Chemoreceptor reflex: Activated when levels of H+, CO2, and O2 changes in blood

Front 52

Baroreceptor Reflex

Back 52

** Baroreceptors are pressure sensitive, when pressure falls they detect low blood pressure

** So the send signals to Cardiovascular center at a slower rate:

** From Internal carotid artery through Glossopharyngeal nerves

** From Aorta through Vagus nerves

** Cardiovascular center activates Sympathetic nerves and inhibit Parasympathetic nerves, which in turn Increase heart rate, contractility, and vasoconstrict vessels which Increases blood pressure

Front 53

Chemoreceptor Reflex

Back 53

** When they detect Hypoxia, Acidosis, or Hypercapnia (excess carbon dioxide), it sends signal to Cardiovascular center

** The center activates Sympathetic nerves and inhibit parasympathetic nerve which in turn Increase heart rate, contractility, and vasoconstrict vessels which Increases blood pressure

** Chemoreceptors also send input to Respiratory center to regulate rate of breathing

Front 54

Four hormones that regulate Blood Pressure

Back 54

1) Renin-angiotensin-aldosterone

2) Epinephrine and Norepinephrine

3) Antidiuretic Hormone (ADH)

4) Atrial Natriuretic Peptide (ANP)

Front 55

Epinephrine and Norepinephrine

Back 55

** Sympathetic stimulation to Adrenal glands release Epinephrine and Norepinephrine

** It increases heart rate and Contractility; Cause Vasoconstriction which in turn blood pressure increases

Front 56

Antidiuretic Hormone (ADH)

Back 56

** Produced by Hypothalamus

** When blood volume is low >> Posterior Pituitary gland releases ADH; it causes Vasoconstriction which increases blood pressure

** ADH reduces Urine volume which increases blood volume and blood pressure

Front 57

Atrial Natriuretic Peptide (ANP)

Back 57

** When blood pressure is high, Cells of Atria releases Atrial Natriuretic Peptide

** ANP causes Vasodilation, increases urine output and decrease blood volume and blood pressure