Chapter 19) Circulatory System Flashcards
1
Q
Blood Vessel Types
A
- Arteries) Carry Blood away from the heart
- Branch to From Capillaries
- Capilalries) branches of arteris that connect tissue cells
- serve cells
- Veins) Carry blood toward the heart
- Converge into larger vessels
2
Q
Structure of Blood Vessel Wall
A
- Lumen) Central Blood Containing space
- Tunica Intimita (Inner Wall Layer) In contact with blood in lumen
- Consists of endothelium that is a simple squamous epithelium that lines vessels
- Continuous with lining of heart
- Subendothelial layer (Basment Membrane) In vessels larger than 1mm, there is a basment membrane that supports endothelium
- Tuncia Media (Middle Wall layer) Smooth muscle and sheets of elastin
- Smooth muscle Controls Vasoconstriction and Vasodilation. Influences blood pressue/flow
- Tuncia Externa (Adventitia) (Outer Wall Layer)
- Contains Collegen to protect and reinforce/ anchor vessels
- Contains nerve fibers and lymphatic vessels
- Vasa Vasorum (vessels of the vessles) noruishes external layer.
3
Q
Elastic Arteries
A
- Large, Thick-walled Arteries neat the heart
- Aorta and major branches
- Elastin is found in all three tunics (wall layers)
- Large Lumens allow for maximum blood flow
- conducting arteries
- Inctive in Vasoconstriction
- Done to keep smooth pressure downstream
4
Q
Muscular Arteries
A
- Deliver blood to body organs
- Branch from elastic arteries
- also called distrubuiting arteries
- Thickest tunica media of all vessels
- More active in vasocontriction
- Less capabile of streatching (less elastin)
5
Q
Arterioles (Resistance Vessels)
A
- Smallest Arteries
- Contain all three tunics, but Tunica Media is mostly smooth muscle
- Leads to capillary beds
- control flow into capilaries via vasodilation and vasoconstriction
- Arteriolar Diameter
- Controls minute-to-minute blood flow
- Varries in response to nueral, hormonal, and local chemical influences
- Diameter = resistance, arterioles are called resistance vessels because they are narrow which means they are more resistant. Slows down blood speed and lowers pressure so capilaries are not damaged
6
Q
Capillaries
A
- Microscopic blood vessels composed of walls of thin tunica intima
- smallest capilareis are one cell wide
- Pericytes) contractile stem cells that can help regenrate scar tissue and stabilize the capibality
- Found in all tissues exexpt for cartlidge, epithelia, cornea, and the lens
- Functions
- Exchange of things (gas, nutrients, wastes, hormones etc) between blood and interstital fluid.
- What are the three types?
7
Q
Continuuous Capillaries
A
- Abundent in skin and muscles
- held together by tight junctions
- there are gaps in membrane called intercellular clefts that allow limited passage of fluids/ small solutes
- Continuous capillaries of brain are unique
- lack inercular clefts which forms blood-brain barrier
8
Q
Fenestrated Capillaries
A
- Endotheial cells contain pores (fenestrations)
- more permiable than continous capillaries
- Function in absorption or filtration
- (small intestines, endocrine glands, and kidneys)
9
Q
Sinsuoid Capillaries
A
- Found only in the liver, bonw marrow, spleen and the adrenal medulla
- Contain large inercellular clefts and fenestrations
- largest type of capilaries because of lack of tight junctions
- Blood flows slowly
- large molcules and blood cells can pass between blood and surrounding tissues
- macropages can rech into clefts to catch bacteria
10
Q
Capillary Beds
A
- Microcirculation and Capillary beds
- Capillaries form interweaving networks called capillary beds
- Networks of capillaries between arterioles and venules is known as microcirculation
- Terminal arteriole > Metarteriole (vessel in between an artriole and capillary)
- Metarteriole > Throughfare Channel (Between capillary and venule)
- Throughfare Channel > Postcapillary Venule (drains bed)
11
Q
Two types of Vessels in Capillaries
A
- Vascular Shunt (Metaertioles and Thoroughfare channels)
- Short vessel that directly connects terminal aereriole and venules
- On each side of bed
- True Capillaries
- 10 to 100 vessels per bed
- Branch off metarteriole or terminal arteriole
12
Q
Blood Flow Through Capillary Beds
A
- Terminal artiole branches into metarteriole. Metatrole branches from true capallaries which branch and retrun to thorghfare channel
- Precapillary Sphincters lie at root of each true capillary to regulate blood flood into the capillaries
- Can be open or closed depending on how much a specific body part needs nutrient delivery/ waste removal
13
Q
Venules
A
- Capillaries unite to form venules
- smallest are postcapillary venules
- Very Porous
- similar to capillaries
- Allow fluids and WBCs into the tissues
- Consists of Endothelium and and a few Pericytes.
- Larger venules have one or two layers of smooth muscle cells.
14
Q
Veins
A
- Venules Join to form Veins. Have larger lumens compared to their corresponding arteries
- results in lower blood pressue than in arteris
- Tunica media is thin
- can be thin because of lower blood pressure
- Tunica Externa is thick and filled wit collegen and elastic networkds
- Veins are called capacitance vessels (blood reservoirs) because they can hold up to 65% of the body’s blood supply.
- Venous Valves) prevent backflow of blood
- most abundent in limbs
- Venous Sinuses) flattened veins with thin walls composed of only epithelium
- Supported by surrounding tissues.
*
- Supported by surrounding tissues.
15
Q
Vascular Anstomoses
A
- Most Organs receive blood from more than one major arterial branch. This forms arterial anastomeses when the same teritory is covered by more than one artery
- ensures an alternate pathway called Collateral Channels for blood to take.
- Occur at joints, abdominal organs, the brain, and the heart
- None in the retina, kindys or spleen (have poorly developed collateral circulation)
- Arteriinovenous anastomoses) Vascular shunts of capillaries
- Venous Anastomoses) common as vains interconnect freely
16
Q
Blood Flow
A
- Volume of blood flowing through a vessel, organ, or entire circulation in a given period
- Measured as ml/min
- Equilivent to Cardiac Output (volume of blood pumped by each venticle)
- Relitvely constant at rest
*
17
Q
Blood Pressure
A
- The force per unit are exerted on the wall of blood vessels
- expressed in mm Hg
- Measured as systemic arterial BP in large arteris near heart
- Hydrostatic Pressure Gradient) diffrences in blood pressure in vascular system
- keeps blood moving from higher to lower pressure and through the body
18
Q
Resistance
A
- Opposition to Flow
- measure of amount of friction blood encounters with vessel walls
- Important sources of resistance
- Blood Viscosity (thickness)(stickiness due to formed elements and plasma proteins)
- Total blood vessel length (More length= more resistance)
- Blood Vessel Diameter. (smaller diameter/vasoconstriction = more resistance)
- Greatest influence on resistance
19
Q
Relationship Between Blood Flow, Pressure and Resistance
A
- Blood Flow (F) is directly proportinal to the diffrence in blood pressure (ΔP) between two points
- ΔP increses, blood flow speeds up
- Blood flowus inversley propotinal to peripheral resistance (R)
- If R increases, blood flow decreases
- F=ΔP/R
20
Q
Systemic Blood Pressure
A
- Pressure generated when pumping action of heart encounters resistance.
- Highest in the Aorta where it declines through the pathway (0mm Hg in right atrium)
- Steepest drop in pressure occurs in arterioles which offer the greates resistance.
21
Q
Arterial Blood Pressure
A
- Pressure reflects two factors of arteries
- Elasticicty of elastic arteries
- Volume of blood forced in them at a time
- Blood pressure near heart is pulsatile (rises and falls)
- Systolic Pressure) Pressure exerted on aorta during ventricular contraction
- About 120 mm Hg in adults
- Diastolic Pressure) lowest level of aortic pressure
- aoritc valve closes to prevent backflow
- Pressure drops to 70-80 mm HG
- Pulse Pressure) diffrence between systolic and diastolic pressure
- Mean arterial pressure (MAP) pressure that is enough to send blood through the capalaries to the tissues
- Roughy equal to diastolic pressure plus 1/3 of systolic pressure.
22
Q
Vital Signs
A
- Vital Signs
- Pule and Blood Pressure
- Respritory rate and body temprature
- Pulse) Pressure wave caused by expansion and recoil of arteries
- Taking A pulse)
- Found in an artery that is close to the surface of the body (ex. radial artery)
- Pule Points/ Pressure Points) can be compressed to stop blood flow
23
Q
Measuring Blood Pressure
A
- You measure systemic arterial blood pressure in the brachial artery of the arm via the Ausculatory method
- use a pressure cuff (sphygmomanometet)
- Systolic pressire) 120 mm HG
- sound is heard when blood rushes through constricted artery
- Diasotlic pressure) 80mm Hg or less
- Sound stops as blood flow normalizes
24
Q
Capilary Blood Pressure
A
- Ranges from 17 to 35mm Hg
- Low pressure is desirable as high pressure would rupture apillaries
25
Venous Blood Pressure
* Changes little during cardiac cycle
* Small pressure gradient is about 15 mm Hg
* due to resistance
* Factors aiding Venous return
* Muscular pump) contraction of skeletal muscles
* Respritory Pump) moves blood as we breathe
* Sympathetic venoconstriction) reduces the volume of blood in the veins. Smooth muscle around veins contracts.
26
Maintaing Blood Pressure
* Requires
* Cooperation of heart, blood vessels, and kidneys
* supervision by the brain
* Blood Presure = Cardiac output x Resistance
* Blood Pressure is directly related to CO and R (Change P = CO x R)
* Any change in one variable (P, CO,R) is normally compensated for to mantain constant blood pressure.
27
Short Term Nueral Control of Blood Pressure.
* Control peripheral resistabce
* Mantain MAP by alterting blood vessel diameter
* Will send blood to heart and brain if blood volume starts to drop.
* Alter blood distribution to organs (ex shunts when excercise levels increase)
* Controls operate via Reflex Arcs
* Barorecepors (Pressure-sensitive mechanoreceptors)
* Cardivascular center in medulla (clusters of sympathetic nuerons that moniter blood presure and control blood vessel diameter aka Vasomotor tone)
* Chemoreceptors detect increase in CO2 or drop of pH or O2 and signal to increase CO and vasoconstrictuon (increased MAP)
* Low MAP \> Vasoconstriction \> Increased CO
* Reflexes that regulate blood pressure are locaed in the Medulla
* not located in hypothalamus or cerebral cortex.
28
Short Term Hormonal Control of Blood Pressure.
* Hormones can Increase Blood Pressure
* Epineprine and Norepineprine) Increase CO and Vasoconstriction
* Angiotensin II) Renin from Kidneys is released when BP is low. Rennin genrates Angiotensin II which stimulates vasoconstriction and raises blood pressure.
* Can lower Blood Pressure
* Atrial Nural peptide (ANP) causes decreased blood volume by antagonizing (stopping) adlesterone.
29
Long Term Mechanism) Renal Regulation
* Baroreceptors adapt quickley so they cannot moniter long term pressure; Kidneys mantain blood pressure homeastasis
* Kidneys regulate blood volume
* Do so in two methoeds
* Direct Renal Mechanism
* Does not require hormones
* Increadsed BP = more urine which lowers pressure
* Decreased BP or Volume = less urine to conserve water and raise BP/Volume
* Indrirect mechanism
* Rennin-Aldesterone mechanism
* Low BP \> Release of Rennin\> stimulates aldestrone release (increased blood volume, causes vasoconstriction)
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31
Hypertension
* High Blood Pressure
* Sustained elevated arterial pressure of systolic pressure above 140 mm Hg or Diastolic above 90 mm Hg
* Prehypertension) elevated pressure but not in hypertension range
* at risk for developing hypertension
* 30% of people above 50 are hypertensive
* Heart works harder which enlarges and weakens it
* Primary/Essential hypertensuon
* No underlying cause (diet, stress, obesity, age, and smoking are risk factors)
* No cure but can be controlled
* Secondary Hypertension
* Due to an identifable disorder such as kidney desiese or hyperthyroidism
32
Hypotension
* Low blood pressure
* usually below 90/60 mm Hg
* Only a concern if it leads to inadequate blood flow or backflow
* Orthostatic Hypotension) Temporary low BP and dizziness when suddenly rising from sitting/ reclining
* Chronic Hyotension) Sign of another desiese (addisions. hyperthyroidism, malnutrition)
* Acute Hypotension) Sign of circulitory shock (inadquate blood flow)
* can kill cells if persistance
* mostly due to hypovolemic shock which results from large scale blood loss.
33
Circultory Shock
* Any condition where
* blood vessels are inadequately filled
* Blood cannot circulate
* Hypovolemic Shock) Results from blood loss
* Vascular shock) Results from extreme vasodilation/ decreased peripherial resistance
* Cardiogenic shock) results when heart cannot sustain circultion
34
Tissue Perfusion
* Means Blood Flow through Body Tissues.
* Involved in
* Delivery of O2/ nutrients
* Gas exhange in lungs
* Absortion of nutrients (digestive)
* Urine Formation (kidneys)
* Rate of Flow to each tissue is percise ammount for proper function
* Not too much or too little
* Changes based on body needs at the time
35
Autoregulation
* Rate of Blood Flow is exatly right for each organ. Achieved by autoregulation
* Intresnic Controls
* Control of flow is withing the organ or tissue by modifying the diameter of local arterioles
* Uses paracrines/ muscle tissue
* Known as autoregulation or local control
* Extrensic Cotrols
* Controls flow via arterial smooth muscle
* Acts via sympathetic nervous system and action of hormones.
36
Meatabloic Controls (autoregulation)
* Vasodilation of Artioles and Relaxtion of precapillary sphincters occur in response to
* Declining O2 levels
* Increase in metabolic wastes and inflamitory chemicals
* Release of NO (powerful vasodilator)
* Effects
* Relaxation of vascular smooth muscle
37
Myogenic Controls (Autoregulation)
* Vascular smooth muscle resonds to streatch
* Passive streach promotes increased tone/ vasoconstriction
* Reduced streacth promotes vasodilation/ increased blood flow
38
Long Term Autoregulation
* occurs when short term regulation cannot meat tissue requirments
* Angiogenisis
* Number of vesses in region increases
* done to increase blood flow
39
Blood Flow) Skeletal Muscles
* Varries with fiber type and activity
* Active/Excercise Hypermia
* muscles become active and blood flow increases in direct proportion to metabolic activity
* Excercise means less O2. Blood flow/ respritory rate increase to compensate
* Sympatetic activity reduces blood for skin/digestive system and sends it to the muscles.
40
Blood Flow) Brain
* Constant flow of about 750ml/ min
* Meatabolic controls
* Decreased pH, Increased CO2 causes vasodilation
* Myogenic Controls
* Decreased MAP causes dilation
* Increased MAP caises constriction
* Syncope/ Fainting) occurs when brain blood pressure hits below 60mmHg
41
42
Blood Flow) Skin
* Blood Flow through the skin
* Supplies nutrients to cells (autoregulation in response to O2 needs)
* Helps regulate body temprature (neurally controlled vasoaction)
* Provides a blood resivuior
* Regulating Temp is main action
* can change from 50 ml/min to 2500 ml/min depending on needs.
* Temp rises \> Warm blood flushes skin \> heat is removed
* Temp Decreases \> Blood Vessels constrict \> Blood is diverted to more vital organs
43
Blood Flow) Lungs
* Pulmonary circut is unusual in many ways
* Pathway is shoer
* Arteries/ Arterioles are like veins in the sense that they have thin walls and large lumens
* Arterial resistance is low
* Autoregultory mechanism is opposite that iun most tissues
* O2 is Low\> Causes vasoconstriction because it is nonfucntional
* O2 is High\> Promotes vasodilation to get as much O2 as possible
44
Blood Flow) Heart
* During Ventricular Systole
* Cornoary Vessels are compressed. Myocardial (heart) blood flow ceases
* Stored myoglobin provides sufficent nutrients for heart during systole
* During Diastole
* High pressure forces blood through cornary circut
* During Excercise
* Cornary vessels dialate in responde to local accumulation of vasodilators
* Blood flow increases to cornary aretries 3-4 times
45
Velocity of Blood Flow
* Slow blood flow through capillaries promotes diffusion of nutrients and gases, and bulk flow of fluids
* Velocity is inversley related to blood flow
* Where blood flow is the faster the total area avabiale for diffusion declines
* Vasomotion
* Blood flow in capilaries is slow and due to vasomotion; the opening and closing of precapillary sphincters
46
Capilary Exchange
* Diffusion down concentration Gradients
* O2 and nutrients from blood to tissues
* CO2 and metabolic waste from tissues to blood
* Four Routes across capillaries for diffrent molecules
* Lipid soluable molecules diffuse directley through _Endothelial Membranes_ (lipid soluable)
* Water-soluable solutes pass through _Clefts_ and _Fenestrations_
* Larger molecules (proteins) are activally tranported in _Pinocytotic Vesicles_
47
Hydrostatic Pressures
* Direction and ammount of flpw depend on two oposing forces
* Hydrostatic Pressures
* Capillary Hydrostatic Pressure (HPc) (Capillary Blood Pressure) forces fluids through capaleries. greater at arteries (35mmHg) vs venule (17mmHg)
* Interstitital Fluid Hydrostatic Pressure (HPif) Pressure that would push fluid into a vessel if lymphatic vessels were not constantly drawing from it
* Colloid Osmotic Pressures
* Capillary Colloid Osmotic Pressure (Oncotic pressure) (OPc) Created by nondifussiable plasma protiens which draw water to themselves (26mmHg)
* Intersitial Fluid Osmotic Pressure (OPif) Low pressure due to low protien content (~1mmHg)
48
Net Filtration Pressure
* Comprises all forces acting on the capillary bed
* Net fluid flow out of arteries
* Net flow into the veins
* More fluid leaves than is returned
* Excess is returned via the lymphatic system
49
Edema
* An abnormal increase in the ammount of intersitial fluid
* Causes
* Increase in capillary Hydrostatic pressure (pushing out)
* Increase in interstital fluid Osmotic pressire (pulling in) due to lack of protein in plasme
* Decreased capillary OP
* Due to hypoprotenimemia
50
Develmental Aspects of Circultiory System
* Vessel formation occurs
* to support body growth
* wound healing
* to rebuild vessels lost during menstral cycles
* As we agge
* vascular desiese begins to appear
* Atherosclerosis and increased BP may arise.
