Chapter 18

2 common causes of edema

1. An increase in capillary hydrostatic pressure i.e most common capillary hydrostatic pressure is hypertension.2. A decrease in the oncotic pressure (colloid osmotic pressure)- One of the most common causes is liver failure as a result of chronic alcoholism, viral infection, or cancer

Hypotension causes

1.reduced blood volume , can result from dehydration, vomiting, diarrhea, overuse of diuretics, low fluid intake. 2. decreased cardiac output, caused by medications that lower heart rate, or a decreased stroke volume caused by heart failure. 3. vasodilation. Septic Shock resulting from a severe bacterial infection can also result in vasodilation

Blood Flow

1.the volume of blood that flows per minute is determined by 2 factors . i.e blood pressure and resistance. _____ is directly proportional to the pressure gradient. Thus as the pressure gradient increases, so does ____

epinephrine, norepinephrine, and thyroid hormone

3 main *hormones* that affect Cardiac Output

resistance, cardiac output, and blood volume

3 main factors that influence blood pressure

one-way valves skeletal muscle pump respiratory movements

3 mechanisms that assist blood returning to the heart in the veins

blood reservoirs

Also the lumen of most veins is larger than the lumen of most arteries. Thus, veins are able to function as

Blood Vessel Radius

As the size of the vessel decreases, its radius is also decreased. Smaller vessels have a greater resistance than larger vessels

Tissue Perfusion in Special Circuits-Heart

Because of the contraction forces in the ventricular muscle, blood only flows through the coronary circulation during diastole The main regulatory mechanism of the coronary circulation is metabolic control

Sphygmomanometer and a stethoscope

Blood pressure is usually measured using a

Metabolic Controls

Cellular Metabolism generates chemicals that can act to regulate tissue perfusion

The solute particles in a solution exert a pulling force on water that is known as Osmotic Pressure (OP) - A solution with a higher solute concentration will have a higher Osmotic Pressure than a solution with a lower solute concentration...

F.Y.I - Recall that osmosis is the movement of water from an area of low solute concentration to an area of high solute concentration

Diffusion through the Endothelial Membrane

Lipid soluble substances such as oxygen, carbon dioxide and certain lipids can generally enter and exit the capillary by diffusing through the endothelial cells. The diffusion always takes place down a concentration gradient.

returning to the heart

Many of the larger veins (especially those in the legs) contain one-way valves which assist with blood (going where)

Tissue Perfusion in Special Circuits-Skin

One of the mechanisms behind autoregulation of blood flow to the skin is temperature. warm conditions will cause vasodilation while cold conditions will cause vasoconstriction

systolic pressure between 140-159mmHg and a diastolic pressure between 90-99mmHg

Stage 1 hypertension

systolic pressure greater or equal to 160 mmHg and a diastolic pressure greater or equal to 100mmHg

Stage 2 hypertension

Vasoconstriction is a decrease in the diameter of a blood vessel caused by a contraction of this smooth muscle.Vasodilation is an increase in the diameter of a blood vessel caused by the relaxation of this smooth muscle.A layer of elastic fibers

The Tunica Media has A layer of smooth muscle arranged in a circular manner around the lumen.This smooth muscle controls the diameter of the blood vessel &thus the amount of blood flowing through it.

Tissue Perfusion in Special Circuits-Brain

The brain is more intolerant of ischemia than any other tissue in the body A loss of consciousness will occur within seconds of a sudden decrease in perfusion pressure. Autoregulatory mechanisms including myogenic and metabolic controls maintain cerebral blood flow

Oncotic Pressure/Colloid Osmotic Pressur

The difference in osmotic pressure between the capillary and the interstitial space is known as the

Blood vessel length

The longer the blood vessel, the greater the resistance to flow.

Peripheral Resistance

The majority of resistance to blood flow takes place away from the heart, in the periphery where the arteries branch and become smaller.

vessel size, viscosity, and vessel length

There are 3 things that contribute to peripheral resistance

Arteries

There are usually more veins in the body than there are

osmosis and filtration

Water moves into and out of the blood by passing through small pores and fenestrations as well as moving via

Tissue Perfusion in Special Circuits-Skeletal Muscle

When exercise begins metabolic conditions in the skeletal muscle cause vasodilation resulting in an increase in blood flow to the muscle

Fenestrated Capillaries

_____ capillaries contain fenestrations or openings in the endothelial cells which makes them more leaky than continuous capillaries

vein

a blood vessel which drain blood from capillary beds and carry it towards the heart.

Hypotension

abnormally low blood pressure. Usually systolic pressure of less than 90mmHg and/or a diastolic pressure less than 60mm

effects of epinephrine and norepinephrine

are identical to stimulation of the sympathetic nervous system; both increasing cardiac output by increasing heart rate and contractility. Thyroid hormone (TH) acts in an indirect manner to increase cardiac output

baroreceptors

are stretch receptors in the aorta and carotid arteries

Capillaries

are the exchange vessels and the smallest of all blood vessels and are arranged in networks called "beds"

Continuous Capillaries

are the least "leaky" and permit the fewest substances to enter or exit the blood. Their endothelial cells are joined by tight junctions

respiratory movements

assist blood flow in the veins in the thoracic and abdomen o pelvic cavities

Hormones that Regulate Resistance Epinephrine and norepinephrine

cause vasoconstriction in many blood vessels in the body and thus will increase resistance and thus increase blood pressure

Atrial Naturetic Peptide (ANP)

causes the kidneys to increase the elimination of sodium and water which decreases blood volume

Edema

characterized by excessive water in the interstitial fluid

Hypertension

commonly referred to as "high blood pressure". associated with an increased risk of coronary artery disease, stroke, heart failure, kidney disease, vascular disease and more

Tunica Intima

consists of endothelium.The endothelium consists of single layer of simple squamous epithelial cells that sits on a basement membrane. The endothelium is continuous with the endocardium of the heart.

The walls of arteries

contain a thicker tunica media and thus a thicker wall than veins do.

The basement membrane

contains connective tissue containing elastic fibers which gives blood vessels distensibility or the ability to stretch when subjected to an increase pressure

chemoreceptors - peripheral chemoreceptors

detect the presence or absence of certain chemicals. There are _____ that regulate blood pressure are located in the aortic arch and in the carotid artery close to the baroreceptors that are known as ______

one-way valves

function to keep blood from blowing backwards in the veins

Sinusoidal Capillaries

have discontinuous sheets of endothelium and very large pores in the endothelial cells. are the leakiest of all capillaries

Capillary Exchange

have extremely thin walls which allows them to function as exchange vessels for nutrients, gases, ions, water, hormones, and waste between blood and the tissues. Materials are generally exchanged via one of 3 mechanisms

Capillary exchange - Diffusion and Osmosis

have small openings between the endothelial cells called fenestrations. Some small substances such as monosaccharides & amino acids can move freely through these pores when there is a concentration gradient

artery

is a blood vessel which carries blood away from the heart, can be thought of as distribution vessels. With the exception of the Pulmonary Arteries, ___ carry oxygenated blood.

Tissue Perfusion

is blood flow through a capillary bed to a tissue and takes into account the mass of the tissue. Perfusion is calculated by taking the blood flow and dividing it by mass in grams of tissue

Tunica Intima

is the inner most layer of the wall of a blood vessel that is next to the lumen. The lumen is the central hollow region where the blood is located.

Tunica Media

is the middle layer of the blood vessel wall and it has 2 components

Tunica Externa

is the outermost layer of the blood vessel and is composed of dense irregular connective tissue

Blood Pressure

is the outward force that blood exerts on the walls of the blood vessels;

Treatments for hypertension

lifestyle modifications including smoking cessation, weight loss, limit alcohol intake, increased physical activity. dietary modifications including low salt diet, decreased cholesterol intake, decreased saturated fat intake. drug therapy is aimed at one or more of the 3 factors controlling blood pressure: cardiac output, blood volume, and peripheral resistance

vascular anastomoses

locations where blood vessels connect via pathways called collateral vessels. represents an alternative route for blood flow

Filtration

movement of a fluid driven by a force such as pressure or gravity

Arterial Anastomoses

neighboring arteries are connected by collaterals

Venous Anastomoses

neighboring veins are connected by collaterals

Transcytosis

process in which the molecules are taken into the cell by endocytosis and then moved out the other side by exocytosis

Blood Viscosity

refers to how thick the blood is.As the liquid increases, it peripheral resistance also increases.

vasculature

refers to the blood vessels

Aldosterone

released by the adrenal cortex and acts in the kidney causing an increase in the retention of sodium by the kidney.Since water goes wherever sodium goes, there is a corresponding increase in total body water and thus an increase in blood volume

The parasympathetic nervous system

releases the neurotransmitter acetylcholine. Acetylcholine causes the heart rate to slow which decreases cardiac output and thus blood pressure

sympathetic nervous system

releases the neurotransmitters norepinephrine & epinephrine in response to stressors in the body (does not have to be major stressors)These neurotransmitters cause an increase in heart rate and contractility which increases cardiac output and thus increases blood pressure

Myogenic Mechanism Regulation

relies on properties inherent in the smooth muscle of the arteriole vessel supplying the capillary beds. Increases in blood pressure in the arterioles activates stretch sensors which result in vasoconstriction. The reverse is true if there is a decrease in blood pressure.

Blood vessels

responsible for transporting blood to and from the heart & tissues in the body, regulating the exchange of gases, nutrients, and waste, as well as controlling blood pressure

Hormones that Regulate Blood Volume Antidiuretic Hormone (ADH)

secreted by the posterior pituitary and acts in the kidney causing an increase in water reabsorption and decrease in urine production

Normal blood pressure

systolic pressure of less than 120mmHg, and a diastolic pressure of less than 80mmHg.

Pulse Pressure

the difference between the Systolic Pressure and the Diastolic Pressure

Hydrostatic Pressure

the force that a fluid exerts on the wall of its container. Blood pressure is a hydrostatic pressure which will force water out of a capillary - This movement of water is an example of filtration

Hemodynamics

the physiology of blood flow in the cardiovascular system

Diastolic Pressure

the pressure in the arteries during diastole is usually around 80mmHg

Systolic Pressure

the pressure in the arteries during systole is usually around 120mmHg

Angiotensin-II (Ang-II)

very powerful vasoconstrictor and will sharply increase peripheral resistance causing an increase in blood pressure

systemic arterial circuit

when a reference to "blood pressure" is made, the pressure referred to is the pressure in the

Arterio venous Anastomoses

when an artery empties directly into a vein without progressing through a capillary bed

skeletal muscle pump

when muscles contract, they squeeze on the veins and propel the blood toward the heart