Ch 20 Blood vessels

What elevate blood viscosity?

RBC count and albumin concentration

What are aortic bodies? Location?

Same function as carotid bodies Location: in the aortic arch

What do capillaries do?

Site where nutrients, waste, and hormones pass between the blood and tissue fluid through the walls of the vessels

What does the body prevent excessive blood pressure?

Stretching and recoiling of the arteries during the cardiac cycle

What does the vasomotor center of the medulla oblongata exert?

Sympathetic control over vessels for vasodilation or vasoconstriction

What are the to pressures recorded

Systolic pressure Diastolic pressure

What do chemoreceptors do when the blood chemistry is off?

Tell the brainstem respiratory center to adjust respiratory rate to stabilize PH, O2, and Co2

Where are capillaries absent? What are the consequences of the absences?

Tendon Ligaments Lens of eye Cornea Epithelia Slow healing

What is edema? When does it occur?

The accumulation of excess fluid in a tissue. Occurs when fluid filters into a tissue faster than it is absorbed

What is pulse pressure?

The difference between systolic and diastolic pressure

What happens during vessel length?

The farther the liquid travels the more friction it encounters Pressure and flow decline with distance and length

What are carotid sinuses? Location?

They are baroreceptors that monitor blood pressure. Location: in the walls of the internal carotid artery

What do arterioles do?

They control the amount of blood to various organs

What do conducting arteries do?

They expand during systole Recoil during diastole- which lessens fluctuations in BP

What do medium venules have that make them unique?

They have venous valves

What are continuous capillaries?

They occur in most tissues. They have endothelial cells that are held together by tight junctions and form a continuous tube. Have intercellular clefts, and pericytes

What do baroreceptors do when there is high blood pressure?

They tell the brainstem to decrease heart rate and vessel dilation

What does transcytosis mean?

Through the cell

Consequences of edema

Tissue necrosis oxygen and waste removal impaired Pulmonary edema suffocation Cerebral edema headaches, nausea, seizure, coma Severe edema or circulatory shock low blood volume and pressure

What is the job for skeletal muscles in the medium veins?

To pump/propel venous blood back to toward the heart

What are hemorrhoids?

Varicose veins of the anal canal

Blood vessels bind to alpha adrenergic receptors do what?

Vasoconstriction

Skeletal and cardiac muscles blood vessels bind to B adrenergic receptors to do what?

Vasodialation

What is the secondary role for chemoreflex?

Vasomotion

Where are large veins found?

Vena cavae Pulmonary veins Internal jugular veins Renal veins

What is the only way of controlling peripheral resistance ?

Vessel radius

What is arterial anastomosis?

WHere two arteries merge providing alternative routes of blood supply to a tissue

What is neural control?

Where central and autonomic nervous system get involved

What are aneurysms ?

a weak point in an artery or heart wall. It forms a thin walled, bulging sac that can rupture

What is the primary role of chemoreflexes?

adjust respiration to change in blood chemistry PH is most important determinant

What is medullary ischemic reflex?

an autonomic response where the medulla oblongata monitors its own blood supply and activates corrective reflexes when it senses ischemia (~shortage of oxygen in blood vessel)

What is circulatory shock

any state in which cardiac output is insufficient to meet the body's metabolic needs

What happens when sphincters are closed?

blood bypasses the capillaries , leaving the less filled or even bloodless, and the blood takes a shortcut through the metarterioles and thoroughfare channels to venule

What is laminar flow?

blood flowing in layers in the vessels

Lungs

flow slower- more time for gas exchange

What is neurogenic shock?

forms of venous pooling shock that results in sudden loss of vasomotor tone

Exercise increases venous return

heart beats fasting increasing BP and CO

What is hormonal control?

hormones that influence BP like ADH, EPI, and NOR

What are metarterioles?

link arterioles to capillaries. They sometimes provide shortcuts where blood can bypass capillaries and flow directly to the venules

Tunica Externa

loose connective tissue. anchors the vessel

The skeletal muscle pump

massage of vessels in the muscle to squeeze the blood back to the heart

What is diastolic pressure?

minimum arterial BP taken during ventricular relaxation

Define hemodynamics

the physical principles of flow Flow is proportional to pressure and resistance

What is anastomosis?

the point where two blood vessels merge

What is peripheral resistance?

the resistance of flow that the blood encounters in vessels away from the heart

What is arteriovenous anastomosis

the shunt arter flows directly to veins by passing the capillaries

What do pericytes do?

they wrap around the capillaries and contract and regulate blood flow

Brain

total blood flow to brain fluctuates less than any other organ because loss of blood flow can cause brain damage

What is ecompensated shock

triggers when compensated shock fails. life threatening positive feedback occurs (blood clotting) damaging cardiac and brain tissue

What is capillary exchange?

two way movement of fluid across capillary walls the most important blood in the body is in the capillaries

2 examples of vasoreflexes

vasoconstriction- smooth muscle contraction vasodilation- smooth muscle relaxation

What are venous sinuses?

veins with thin walls and no smooth muscles, they rely on gravity and suction?

Arteries

vessels that carry blood away from the heart

Veins

vessels that carry blood back to the heart

What can hypertension cause

weaken of small arteries aneurysms

5 Mechanisms of venous return

1 Pressure gradient 2 Gravity drains blood from head and neck 3 Skeletal muscle pump 4 Respiratory pump 5 Cardiac suction

3 Principles of circulatory shock?

1 hypovolemic shock- loss of blood volume 2 obstructed venous return shock- tumor or aneurysm compresses a vein 3 Venous pooling- long periods of standing or sitting

What are the 5 types of veins from smallest to largest

1 postcapillary venules 2 muscular venules 3 medium venules 4 venous sinuses 5 large venules

3 layers of arteries and veins

1 tunica interna 2 tunica media 3 tunica externa

What is portal system?

Blood that flows through TWO consecutive capillary networks before returning to the heart

Where are distributing arteries found?

Brachial Femoral Splenic Renal

What is secreted to stimulate vasodilation in LOCAL control?

Bradykinin Histamines Prostaglandins

What are the 3 arterial sense organs?

Carotid Sinuses Carotid Bodies Aortic Bodies

Where are chemoreflexes located?

Carotid bodies and aortic bodies

What are carotid bodies? Location?

Carotid bodies are chemoreceptors that monitor blood chemistry

What are vasoreflexes?

Change in vessel radius

What are capillary beds?

Connect venules and arterioles?

Mechanisms involved in capillary exchange?

Diffusion Transcytosis Filtration Reabsorption

What are venous sinuses related to?

Dural venous sinus and cronary sinus of the heart

Cardiac suction

During systole the chordae tendinae pull down slightly on the AV valves this slightly increases volume to the atria leading to a suction of blood into the atria from both the vena cava and the pulmonary veins

Capillary diffusion can only occur if what?

Endothelial cells must be selectively permeable Find passages large enough to pass through (via filtration pores or intercellular clefts)

What are fenestrated capillaries? Who are they for?

Endothelial cells that have filtration pores For organs that need rapid absorption and filtration

What are capillaries composed of?

Endothelium and basal lamina

Importance of arterial elasticity

Expansion and recoil maintains steady flow of blood throughout cardiac cycle Smooths out pressure fluctuations and decrease stress of small arteries

What is anaphylactic shock?

Exposure to an antigen to which a person is allergic to

Vessel radius affects blood velocity (speed)

F is proportional to r4

FILTRATION and REABSORPTION

Fluid filters out of the arterial end of the capillary and osmotically reenters at the venous end Delivers materials to the cell and removes metabolic waste

Example of peripheral resistance

From AORTA to CAPILLARIES blood velocity decreases because: The greater the distance the more friction to reduce speed Smaller radii of arterioles and capillaries offer more resistance Farther from the heart, the flow rate goes down *never goes back up to original speed*

Example of peripheral resistance #2

From CAPILLARIES to VENA CAVA blood velocity increases again Decreased resistance going from capillaries to veins Larger amount of blood is forced into smaller channels *Never regains velocity of large arteries*

What do continuous capillaries allow passage of?

Glucose and other small solutes

Describe the simplest circulatory route

Heart > large arteries > medium arteries > arterioles > capillaries > venules > medium veins > large veins> heart

What causes varicose veins?

Heredity weakness Obesity Pregnancy Standing for too long

What cannot diffuse easily through plasma membranes? How do they get through?

Hydrophilic water soluble substances -glucose -electrolytes Intercellular clefts and filtration pores

What can diffuse easily through plasma membranes?

Hydrophobic lipid-soluble substances -Steroid hormones - O2 + CO2

What are the 4 opposing forces

Hydrostatic pressure- pushes H20 out Osmotic/oncotic pressure- pulls H20 in Pressures in the vessel Pressures in the tissues

Examples of reduced capillary filtration

Hypoproteinemia Liver disease Dietary protein deficiency

What is the metabolic theory of autoregulation?

If tissue is inadequately perfused, waste will accumulate and stimulate vasodilation which increases perfusion (flow) so more oxygen can go through When waste is removed the vessel constricts

How does venous pooling occur?

Inactivity not enough pressure to force blood upward

What are sinusoid/discontinuous capillaries?

Irregular blood filled spaces with large fenestrations

How does pressure affect flow?

It drives it

Where does the sensory go?

It transmits information to the brainstem and then regulates heart rate, vasomotion, and respiration

Where are arterial anastomosis found?

Joints and coronary circulation

Where is the portal system used?

Kidney Between intestines to the liver Between the hypothalamus and the anterior pituitary

Examples of increased capillary filtration

Kidney failure Histamine release Old age Poor venous return

Where are fenestrated capillaries found?

Kidneys for filtration Small intestines for absorption Endocrine glands Choroid plexus

What is atherosclerosis?

Lipid deposition in the walls

Where are discontinuous capillaries found?

Liver Spleen Bone Marrow

What is venule anastomosis?

MOST COMMON One vein empties directly into another

Vasomotion + where does this occur?

Occurs in tunica media. Changes in diameter of blood vessel

Brain's main chemical stimulus?

PH

What is systolic pressure?

Peak arterial BP taken during ventricular contraction

What does transcytosis involve?

Pinocytosis or endocytosis Transport vesicles and exocytosis

What increases blood viscosity? What kind of flow does it result in?

Polycythemia and dehydration Slowwwww

Gravity

Allows pressure in the large veins above the heart to be near 0

Where are conducting arteries found?

Aorta Common carotid Subclavian Pulmonary trunk Common iliac arteries

What is arteriosclerosis?

Arterial wall thickening overtime

What are the three types of anastomosis?

Arteriovenous anastomosis Venule anastomosis Arterial anastomosis

What is local control?

Autoregulation- the ability of tissues to regulate their own blood supply

What is septic shock?

Bacterial toxins trigger vasodilation and increased capillary permeability

Hydrostatic Pressure

Blood (BHP) and tissue (THP)

Osmotic pressure

Blood (BOP) and tissue (TOP)

Tunica Media

smooth muscle, collagen, and elastic tissue. strengthens vessels and prevents BP from rupturing them.

Define flow

the amount of blood flowing through an organ, tissue, or blood vessel

What is mean arterial pressure (MAP)?

the average pressure one would obtain by taking BP measurements at several intervals

What is venous return?

the flow of blood back to the heart

Define perfusion

the flow per given volume of tissue

Define blood pressure

the force that blood exerts against the blood vessel

The greater the pressure difference...

the greater the flow

The greater the resistence

the less the flow

Tunica interna (endothelial) Location, composition, functions

*Location:* Lines the blood blood vessels and exposed to blood *Composition:* simple squamous epithelium, basement membrane, and sparse layer of connective tissue *Functions: * acts as selectively permeable barrier, secrete chemicals

Structure of veins

- great capacity for blood containment -flaccid, have thinner walls, less muscular and elastic tissue -collapse when empty, expand easily -have steady blood flow -subjected to very low blood pressure

What are 3 autonomic reflexes that have to do with neural control?

1 Baroreflexes 2 Chemoreflexes 3 Medullary ischemia reflex

What are 3 things that oppose flow?

1 Blood viscosity 2 Vessel length 3 Vessel radius

What are 3 ways blood pressure is determined?

1 Cardiac output 2 Blood Volume 3 Resistance (to flow)

What are the 3 types of capillaries that are distinguished by ease with which substances pass through their walls

1 Continuous 2 Fenestrated 3 Discontinuous/sinusoid

What are the 3 primary causes of edema?

1 Increased capillary filtration 2 Reduced capillary filtration 3 Obstructed lymphatic drainage

What are 3 ways of controlling vasomotion?

1 Local control 2 Neural control 3 Hormonal control

3 types of arteries

1. Conducting (large/elastic arteries) 2. Distributing (medium/muscular arteries) 3. Arterioles (small/resistance arteries)

What are the two purposes of vasomotion?

1. Maintaining BP 2. rerouting blood supply to put it where it needs to be

What can cause hypotension?

Blood loss Anemia Dehydration

What are varicose veins?

Blood pools in the lower legs in people who stand for a long time, which adds stress to the veins The cusp weaken and pull apart, the blood starts to backflow and develop varicose veins

Examples of vasoreflexes:

1. Vigorous exercise dilates arteries in lungs, heart, muscles WHILE vasoconstriction occurs in kidneys and digestive tract 2. dozing in armchair after a big meal vasoconstriction in lower limbs raises BP above the limbs, redirecting blood to the intestinal arteries

Example of baroreflex

1.Increase BP -detected by the carotid sinuses 2.Signal is sent to the brainstem by the glossopharyngeal nerve -Reduces sympathetic tone 3.Excites vagal fibers (parasympathetic) -decreases the BP *short term fix*

What decreases blood viscosity? What kind of flow does it result in?

A deficiency of RBC (anemia) or albumin (hypoproteinemia) Speeeeeed

What is baroreflex?

A negative feedback response

Respiratory (thoracic) pump

Aids flow from the abdominal cavity to the thoracic cavity by inhalation blood squeezes upward

What do discontinuous capillaries allow passage of?

Albumin Clotting factors Proteins

Examples of things that have to use transcytosis?

Albumin Fatty acids and some hormones like insulin

What are dissecting aneurysms?

blood that accumulates between the tunic of the artery and separates them

What happens when sphincters are open?

capillaries are filled with blood and engage in exchange of tissue fluid

Capillaries

connect the smallest arteries to the smallest veins

What do distributing arteries do?

distribute blood to specific organs

What is the simplest circulatory route ?

only passes through one network of capillaries from the time it leaves the heart until it returns to the heart

Pressure gradient

pressure generated by the left ventricle is the driving force of venous return

What are arterial sense organs?

sensory structures that monitor blood pressure and chemistry

What is compensated shock?

several homeostatic mechanisms bring about spontaneous recovery ex a person faints and gravity restores blood flow to brain

What are precapillary sphincters?

single smooth muscle cell that wraps like a cuff around the opening to each capillary

What do fenestrated capillaries allow passage of?

small molecules

Vaso vasorum + where does this occur?

small vessels that supply blood to at least the outer half of the larger vessel Tunica externa