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Blood Vessels and Circulation

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Ashley Soper

on 28 April 2014

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Transcript of Blood Vessels and Circulation

Blood Vessels and Circulation
By Ashley and Brittany

Blood Pressure
Pressure in large and small arteries fluctuates
Systolic
pressure is the highest blood pressure
Diastolic
pressure is the lowest blood pressure
These are separated by a slash....120/80
The difference between these pressures is the pulse pressure
The farther from the heart, the lower the pulse pressure
When blood pressure falls, blood vessels recoil. This is called elastic rebound
Blood Vessel Walls
3 distinct layers
Tunica
intima
Tunica
media
Tunica
externa
Function of Blood Vessels
Arteries
- Blood vessels that carry blood away from the heart and toward a peripheral capillary.
Capillary- small blood vessels, interposed between arterioles and venules whose thin walls permit diffusion
Veins-blood vessel carrying blood from a capillary bed toward the heart
Factors Affecting Blood Flow
Turbulence

Tunica Intima
Also called tunica interna
Innermost layer of blood vessels
Includes endothelial lining and underlying layer of connective tissue dominated by elastic fibers
Tunica Media
Middle layer
Contains smooth muscle tissue in a framework of collagen and elastic fibers
When the muscles contract, diameter decreases; when they relax, diameter increases.
Tunica Externa
Outer layer
Also called tunica adventita
Sheath of connective tissue around vessel
Collagen fibers intertwine with adjacent tissues, anchoring vessel
Pressure
Resistance
Vascular Resistance
Viscosity
Pressure
Elastic Arteries
Large extremely resilient vessels whose tunica media is dominated by
elastic fibers.

Up to 2.5 cm diameter
Force exerted against a liquid generates fluid pressure, conducted in all directions
Liquid flows to low-pressure areas
Pressure is divided into 3 components
Arterial Pressure (Blood Pressure)
Capillary Pressure
Venous Pressure
Viscosity
Elastic properties enable them to limit pressure changes in the blood through accommodation
Ventricular systole (heart contraction) stretch
Ventricular diastole (heart relaxation) recoil
Viscosity is the resistance of a liquid to flow
Thick liquids flow only under high pressure
Blood is
5x
as thick as water
With anemia, the plasma protein content (hematocrit) is reduced & oxygen capacity and viscosity is reduced
Resistance
Resistance is any force that opposes movement (in this case, the movement of blood)
Total peripheral resistance is the resistance of the entire cardiovascular system
Circulatory pressure must be high enough to overcome total peripheral resistance
Resistance of the arterial system is called peripheral resistance
Vascular resistance, viscosity, and turbulence are all sources of peripheral resistance
Vascular Resistance
Largest component of peripheral resistance
Defined as the resistance of the blood vessels to blood flow
Most important factor-
friction
between blood and vessel walls
Friction increases with increasing blood vessel length and with decreasing diameter
Vascular resistance is controlled by smooth muscles changing vessel diameters
Most vascular resistance is in arterioles
Turbulence
Blood usually flows smoothly, slowest near the walls, and faster near the middle of the vessel
High flow rates, irregular surfaces, or sudden changes in diameter cause turbulence
Turbulence is eddies and swirls in the blood, that cause slower blood flow and increased resistance
Turbulence is usually within the heart or where the aorta and pulmonary trunk meet the heart
This turbulence causes 3rd and 4th heart sounds
Heart murmurs
are created by turbulence across damaged or misaligned heart valves
Muscular Arteries
Muscular
arteries distribute blood to skeletal muscles & internal organs
Diameter up to .4 cm
Ex. external carotid arteries of neck
Tunica media has more smooth muscle cells and fewer elastic fibers
Smooth muscle controls amounts delivered
Capillary Pressure
Capillary pressure is the blood pressure in capillary beds
Capillary walls are
permeable
to small ions, organic wastes, dissolved gases, and water
3.6 gal of water and solutes go through peripheral tissues, into the lymphatic vessels, and back into the bloodstream each day, which is important in homeostasis
This has 4 main functions:
Arterioles
Diameter 30 micro- meters
Small arterial branch that delivers blood to a
capillary
network
Functions
1. Maintaining communication between plasma and interstitial fluid
2. Speeding distribution of nutrients, hormones, and dissolved gases to tissues
3. Assisting movement of insoluble lipids and tissue proteins
4. Flushing toxins to lymphoid tissues to provide immunity to disease

Venous Pressure
Pressure at the start of the venous system is only
one-tenth
of the pressure at the start of the arterial system
Pressure declines slowly in the venous system
2 factors must help the blood overcome gravity:
The Respiratory Pump
Muscular Compression
Response of Cardiovascular System to Stress
Cardiovascular Regulation
Autoregulation

Neural Mechanisms

Endocrine Mechanisms
Exercise
Vasodilation occurs
Venous return increases
Cardiac output rises
Hemorrhage
Short-term BP elevation (venous reserve-liver, marrow, and skin)
Long-term blood volume restoration
Autoregulation
Precapillary
sphincters
change the shape of the blood vessels to regulate blood flow
When oxygen is abundant smooth muscles in the sphincters contract, decreasing blood flow
When carbon dioxide is abundant, sphincters relax, increasing blood flow
Vasodilators- promote the dilation of precapillary sphincters
Vasoconstrictors- promote the constriction of precapillary sphincters.
Functional Patterns in Pulmonary and Systemic Circuits
Arteries and Veins of the Pulmonary Circuit
Pulmonary trunk
Left and right pulmonary arteries
Alveoli
Pulmonary veins
Neural Mechanisms
Cardiovascular centers of the medulla oblongata regulate cardiac output and peripheral resistance
Each cardiac center has:
cardioacceleratory centers- increase cardiac output by sympathetic innervation
Cardioinhibitory centers- reduces cardiac output by parasympathetic innervation.
vasomotion- the control of the diameters of arterioles
vasodialtion & vasoconstriciton
Baroception- measures the degree of stretch of expandable organs
Chemoception- monitors the changes in carbon dioxode, oxygen, or pH in blood and cerebrospinal fluid.
Adult vs. Fetal Circulation
Endocrine Mechanisms
The endocrine system releases hormones that enhance short-term adjustments and direct long-term changes in cardiovascular performance
Blood reaches the placenta through 2 umbilical arteries in the umbilical cord
Blood returns from the placenta through the umbilical vein
The ductus venosus travels from the liver to the inferior vena cava
The foramen ovale is an opening in the interatrial partition
The ductus arteriosus is a short-circuit between the pulmonary and aortic
trunks
Antidiuretic Hormone (ADH)

Released from posterior pituitary in response to:
A decrease in blood volume
An increase in the osmotic concentration of the plasma
The presence of angiotensin II
Results in peripheral vasoconstriction that
elevates
blood pressure
Also has a water-conserving effect on the kidneys, thereby preventing a reduction in blood volume
Venules
Thin-walled veins that receive blood from
capillaries
Capillary Bed- interconnected network of capillaries

Anastomosis- an alternate route for blood formed by the joining of
two vessels
Angiotensin II
Formed in the blood following the release of the enzyme renin by the kidneys in response to a fall in blood pressure.
Renin starts a chain reaction that converts inactive plasma protein, angiotensinogen, to angiotensin II
Stimulates cardiac output and triggers arteriole constriction which elevates systemic blood pressure
Stimulates the secretion of ADH and aldosterone
aldosterone stimulates the reabsorption of sodium ions and water from the urine, ADH stimulates water conservation.
Stimulates thirst
Erythropoietin
Released by the kidneys when blood pressure falls or oxygen content of blood becomes abnormally low
Stimulates red blood cell production, elevating blood volume and improving the oxygen carrying capacity of the blood
Atrial Natriuretic Peptide
Release stimulated by increased blood pressure
Produced by cardiac muscle cells in the right atrium when they are stretched by increased venous return
Lowers
blood pressure and volume by:
Increasing loss of sodium ions and water at the kidneys
Promoting water loss by increasing urine production
Reducing thirst
Blocking the release of antidiuretic horomone, aldosterone, epinephrine, and norepinephrine
NE and E stimulate cardiac output and vasodiolation
Stimulates peripheral vasodiolation
Distribution of arteries and veins on the left and right sides of the body are
identical
, except near the heart
A single vessel may undergo name changes as it moves through the body
Tissues and organs are serviced by several arteries and veins.
Arteries and Veins of the Systemic Circuit
Brachiocephalic trunk
Left and right common carotid artery
Left and right subclavian artery
All five arteries originate along the
aortic
artery to deliver blood to the head, neck shoulders and upper limbs
Superior and inferior vena cava
Aorta
The brachiocephalic trunk ascends for a while before it branches to become the right common
carotid
artery and the right
subclavian
artery.
The carotid arteries deliver blood to the
neck
The subclavian arteries supply blood to the arms, chest wall, shoulders, back, and central nervous system
The superior vena cava receives blood from the head, neck, upper limbs, shoulders, and chest.
The inferior vena cava recieves blood from the organs inferior to the diaphragm.
Effects of Aging

Blood
Decreased hematocrit
Constriction or blockage of peripheral veins by the formation of a thrombus (blood clot)
The thrombus may become detached and pass through the heart and wedge in a small artery.
A pulmonary embolism occurs when the
thrombus
becomes wedged in an artery in the lungs.
Formation of varicose veins
The valves don't work properly, so blood pools in the veins of the legs.
Effects of Aging
Heart
Reduction in maximum cardiac output
Changes in the activities of nodal and conducting cells
Reduction in the elasticity of the fibrous skeleton
Progressive artherosclerosis (hardening of the arteries)
Causing restriction of coronary circulation
Replacement of damaged cardiac muscle cells by scar tissue
Effects of Aging
Blood Vessels
Arteriosclerosis
Thickening and toughening of blood vessel walls
Inelastic arteries become less tolerant to sudden pressure increases, leading to an aneurysm (localized blood vessel dilation)
Rupture of the aneurysm may cause a stroke, myocardial infarction, or massive blood loss
Calcium
deposits may form on weakened blood vessel walls, increasing risk of stroke and myocardial infarction
Thrombi can form at atherosclerotic plaques
Hypertension- high blood pressure
Hypotension- low blood pressure
Full transcript