A&p 2, Ch 19

Front 1

Blood vessels structure and function

Back 1

Blood vessels: delivery system of dynamic structures that begin and end at heart

Arteries: carry blood away from the heart, oxygenated except for pulmonary circulation and umbilical vessels of fetus

Capillaries: direct contact with tissue cell, directly serve cellular needs. Exchange: between arteries and veins

Veins: carry blood toward heart, deoxygenated except for pulmonary circulation and umbilical vessels of fetus

Front 2

Structure of blood vessel wall

Back 2

Three layers or tunics:

1. Tunica intima forms a friction-reducing lining

- innermost layer

- endothelium

2. Tunica Media

- middle layer composed mostly of smooth muscle and sheets of elastin

- sympathetic vasomotor nerve fibers control vasoconstriction and vasodilation

- bulkiest layer responsible for maintaining blood flow and blood pressure

3. Tunica externa forms protective outermost covering

- mostly fibrous connective tissue

- vasa vasorum: system of tiny blood vessels found in larger vessels

Front 3

Arteries

Back 3

Three groups based on size and function

1. Elastic and muscular arteries:

Elastic arteries: thick walled with large for resistance Lumen, abundance of elastin which allows the walls to expand. Do not basil constrict. Found in the aorta and pulmonary arteries.

Muscular arteries: also called Distributing arteries deliver blood to body organs period thickest Tunica Media with more smooth muscle

2. Arterioles

- smallest of all arteries

- control flow into capillaries beds via vasodilation and vasoconstriction of smooth muscle

- AKA resistance arteries because changing diameters change resistance to blood flow

- lead capillary beds

3. Capillaries

- exchange of gases, nutrients and wastes to and from tissue

- capillary endothelial cells are joined by tight junctions with gaps called intercellular clefts

- three types of capillaries:

A. Continuous capillaries: abundant in skin, muscles, Longs, and CNS

- blood-brain barrier , enclosed with with tight junctions, no intercellular clefts

B. Fenestrated capillary: involved in active filtration (kidneys), absorption (intestines) or endocrine hormone secretion

C. Sinusoidal capillaries: have fewer tight junctions, usually fenestrated with larger intercellular clefts, incomplete basement membrane and large lumens

- found in liver, bone marrow, spleen and Adrenal medulla

- macrophages

- blood flow is sluggish

Front 4

Capillary beds

Back 4

Capillary bed: interwoven network of capillaries between arterioles and venules

Microcirculation: flow of blood through bed

2 types of vessels:

- vascular shunt: channel that connects arterial directly with venule

- true capillaries: actual vessels involved in exchange

Fluid movement at capillary beds:

- blood pressure forces fluid and solutes out of capillaries

- osmotic pressure draws fluid into capillaries

Front 5

Veins

Back 5

-Carry blood toward the heart

- formed when venules converge

- have all tunics but thinner walls with large lumens compared with corresponding arteries

- blood pressure lower than in arteries as larger diameter lumens offer a little resistance

- venous valves prevent backflow of blood

- venous sinuses are flattened veins with extremely thin walls, composed only of endothelium

Front 6

Anastomoses

Back 6

Vascular anastomoses: interconnections of blood vessels

Arterial anastomoses: provide alternate Pathways to ensure continuous flow

- common in joints, abdominal organs, brain and heart

Arteriovenous anastomoses: shunt in capillaries

Venous anastomoses: so abundant that occluded veins rarely block blood flow

Front 7

Blood flow

Back 7

Volume of blood flowing through vessel, organ, or entire circulation and given.

- measured in milliliters per minute

- constant when at rest comma varies at individual organ level, based on needs

Front 8

Blood pressure

Back 8

Force per unit area exerted on wall of blood vessel by Blood

- expressed in mm Hg

Front 9

Resistance (peripheral resistance)

Back 9

Opposition to flow

- measurement of amount of friction blood encounters with vessel walls, generally and peripheral systemic circulation

Three important sources of resistance

- blood viscosity

- total blood vessel length

- blood vessel diameter

Front 10

Blood viscosity

Back 10

Thickness or stickiness of blood due to formed elements and plasma proteins

- increase viscosity equals increase resistance

Front 11

Blood vessel diameter

Back 11

- greatest influence on Resistance

- fluid close to walls moves more slowly than in the middle of tube laminar flow

- if laminar flow is disrupted and becomes turbulent flow, your regular flow that causes increased resistance

- if radius increases resistance decreases

- small diameter arterioles are major determinants of peripheral resistance

Front 12

Arterial blood pressure

Back 12

Determined by two factors:

1. Elasticity of arteries close to Heart

2. Volume of blood forced into them at any time

Systolic pressure pressure exerted in aorta during ventricular contraction

Diastolic pressure lowest level of aortic pressure when heart is at rest

Pulse pressure difference between systolic and diastolic pressure

Pulse throbbing of arteries due to difference in pulse pressures

Mean arterial pressure (MAP) pressure that propels blood to tissue

MAP = CO × TR

Front 13

Venous blood pressure

Back 13

- if vein is cut low pressure of venous system causes blood to flow out smoothly

- if artery is cut blood spurts out because pressure is higher

factors aiding venous return:

1. Muscular pump

2. Respiratory pump

3. Sympathetic venoconstriction

Front 14

The muscular pump

Back 14

Three main factors regulating blood pressure:

1. Cardiac output

2. Peripheral resistance

3. Blood volume

Factors can be affected by:

- short-term regulation neural controls

- short-term regulation hormonal controls

- long-term regulation renal controls

Front 15

Short-term regulation neural controls

Back 15

Two main neural mechanisms control peripheral resistance

1. MAP maintained by altering blood vessel diameter which Alters resistance

2. Can alter blood distribution to organs in response to specific demands

neural controls operate via reflex arcs that involve:

- Cardiovascular Center of medulla

- baroreceptors

- chemoreceptors

- higher brain centers

Cardiovascular Center: composed of clusters of sympathetic neurons and medulla

Cardiac centers cardioinhibitory and cardio accelerator

Vasomotor Center: sends steady impulses be a sympathetic efferents called vasomotor fibers to blood vessels

Baroreceptor reflexes located in carotid sinuses, aortic Arch and walls of large arteries of neck and thorax

Front 16

Short-term mechanisms hormonal controls

Back 16

-Hormones regulate BP and short-term via changes and peripheral resistance or long-term via changes in blood volume

- Adrenal medulla hormones epinephrine and norepinephrine from adrenal gland increased carbon dioxide and vasoconstriction

- Angiotensin II stimulate vasoconstriction

- atrial natriuretic peptide decreases BP by antagonizing aldosterone, causing decreased blood volume

Front 17

Long-term mechanisms renal regulation

Back 17

- long-term mechanisms control BP by altering blood volume via kidneys

- kidneys regulate arterial blood pressure by:

1. Direct renal mechanism

- Alters blood volume independently of hormones

2. Indirect renal mechanism

-renin-angiotensin-aldosterone

Front 18

Summary of blood pressure regulation

Back 18

Goal of blood pressure regulation is to keep blood pressure high enough to provide adequate tissue perfusion, but not so high that blood vessels are damaged

Front 19

Arteries of the head and neck

Back 19

Common carotid:

-Internal carotid supplies the brain

- external carotid supplies the face

Circle of Willis: arterial anastomosis on base of brain receiving blood from basilar and internal carotid arteries serves cerebrum

Front 20

Veins of the head and neck

Back 20

-Drain blood from brain to internal jugular vein

- internal jugular vein receives most of the blood from the vein

- external jugular vein drain the external structures of the head

Front 21

Flow

Back 21

Amount of blood flowing through a vessel organ at a given time

Flow = Volume/Time

Front 22

Perfusion

Back 22

Amount of blood flowing through a tissue per weight measured in grams

Perfusion = volume/time//tissue wt

Ex. 2500L/min//1000g = 250mL/100g

Front 23

The mean arterial pressure + peripheral resistance equals this

Back 23

Cardiac output

Front 24

Internal resistance that exists in all fluids, related to fluid thickness

Back 24

Viscosity

Front 25

This vessel supplies blood to the external face

Back 25

External carotid

Front 26

This vessel supplies blood to the brain

Back 26

Internal carotid

Front 27

This vessel drains blood from the brain

Back 27

Internal jugular

Front 28

This vessel drains blood from the external face

Back 28

External jugular

Front 29

Blood vessel interconnections that provide alternate circulatory pathways

Back 29

Anastomoses

Front 30

The most abundant arteries that deliver blood to organs

Back 30

Muscular arteries

Front 31

This layer of the blood vessel contains the endothelium

Back 31

Tunica intima

Front 32

This layer of the blood vessel contains the vasa vasorum

Back 32

Tunica externa

Front 33

This reflex occurs when arterial blood pressure increases

Back 33

Baroreceptor

Front 34

What occurs to blood flow when the blood vessel is constricted

Back 34

Pressure increases

Front 35

What occurs to fluid at the arterial end of the capillary compared to the venous end of the capillary

Back 35

At the arterial end of the capillary blood pressure is more that osmotic pressure and the fluid flows out of the capillary and into the interstitial fluid. At the vinyl end of the capillary blood pressure is less than osmotic pressure and fluid flows from the interstitial fluid into the capillary

Front 36

Why are veins sometimes called Reservoir vessels

Back 36

Because they store blood

Front 37

What is the difference between primary and secondary hypertension

Back 37

Primary has unknown cause secondary has known cause

Front 38

If all the blood vessels were to dilate at the same time What deadly symptom would you expect

Back 38

Vascular shock