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38 Cards in this Set

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Blood vessels structure and function

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

Structure of blood vessel wall

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

Arteries

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

Capillary beds

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


Veins

-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

Anastomoses

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

Blood flow

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

Blood pressure

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


- expressed in mm Hg

Resistance (peripheral resistance)

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

Blood viscosity

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


- increase viscosity equals increase resistance

Blood vessel diameter

- 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

Arterial blood pressure

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

Venous blood pressure

- 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

The muscular pump

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

Short-term regulation neural controls

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



Short-term mechanisms hormonal controls

-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

Long-term mechanisms renal regulation

- 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

Summary of blood pressure regulation

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

Arteries of the head and neck

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

Veins of the head and neck

-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

Flow

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


Flow = Volume/Time

Perfusion

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



Perfusion = volume/time//tissue wt



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

The mean arterial pressure + peripheral resistance equals this

Cardiac output

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

Viscosity

This vessel supplies blood to the external face

External carotid

This vessel supplies blood to the brain

Internal carotid

This vessel drains blood from the brain

Internal jugular

This vessel drains blood from the external face

External jugular

Blood vessel interconnections that provide alternate circulatory pathways

Anastomoses

The most abundant arteries that deliver blood to organs

Muscular arteries

This layer of the blood vessel contains the endothelium

Tunica intima

This layer of the blood vessel contains the vasa vasorum

Tunica externa

This reflex occurs when arterial blood pressure increases

Baroreceptor

What occurs to blood flow when the blood vessel is constricted

Pressure increases

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

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

Why are veins sometimes called Reservoir vessels

Because they store blood

What is the difference between primary and secondary hypertension

Primary has unknown cause secondary has known cause

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

Vascular shock