II: Ch. 21

Smaller muscular arteries

Adapted for vasodilation and vasoconstriction.

Medium veins.

Go-between small veins and large veins. Fuse into large veins

Left common carotid

Up left side of body to head

Inferior vena cava

(abdomen, pelvis, lower limbs) Deoxy blood here back to heart

Pressure

(force per unit area) How much force is being applied to the blood vasculature

Superior vena cava

(head, neck, thorax, upper limbs) Deoxy blood here back to heart

Inferior mesenteric

(takes blood to descending colon and rectum)

Superior mesenteric

(takes blood to pancreas, small intestine, colon)

Celiac trunk -

(takes blood to stomach, liver, duodenum [part intestines]); branching into left gastric, common hepatic, and splenic arteries

Splenic

(takes blood to stomach, spleen)

Functions of circulatory system

1.Carry blood 2.Exchange nutrients, waste products, and gases 3.Transport of hormones, components of the immune system, molecules required for coagulation, enzymes, nutrients, gases, waste products, etc. 4.Regulate blood pressure 5.Directs blood flow

Arteries and veins, not capillaries, have

3 distinct layers (layer = tunic or tunica)

Smooth muscle in arterioles, metarterioles, precapillary sphincters regulates blood flow

All branches want to be able to carefully control amount blood flowing into tissue so have precapillary bed sphincters - lot imp Sphincters - control blood flow to tissues

Smooth muscle allows vessels to regulate blood supply by constricting or dilating

Allow vasodilate and vasocontrict which helps them control amount blood going into tisuses More blood into tissues - vasodilate because increases volume Less blood into tissue - vasoconstrict so less blood going into tissues

Systemic circulation

Aorta

Describe the difference between an artery, capillary, and a vein in as few words as possible.

Arteries - away from heart; elastic; more muscular than cap and veins; higher pressure than cap and generally veins; aorta has highest BP (artery with highest because closer to heart) Capillary - in between arteries and veins; exchange; very small; lots ofbranching (really branch) Veins - to the heart; valves - imp to limit backflow; thinner than arteries but thicker than capillaries

Photomicrograph of artery and vein

Arteries lot more smooth muscle than veins Arteries have thicker tunica media, more smooth muscle, than veins - veins collapse more and arteries do not

Blood flows from arterioles through metarterioles, then through capillary network

Arterioles branch into metarterioles arterioles branch into metarterioles which are what lead directly into cap bed - which is a big number of branches that go through tissues

Arteriovenous anastomoses:

Arterioles to small veins with no capillaries Blood vessels that connect arterioles directly to small veins with no capillary beds Arterioarteriole anastomoses- Blood vessels connect two arterioles together; in heart; one blocked up to ensure redundancy Circle of Willis - have a lot of redundancy in the blood vasculature brain because if one blocked can go around it Connect between arteries and arteries or arteries and veins = anastomoses Sole of foot, palm of hand, terminal phalanges (fingertips), nail beds Temperature regulation - direct blood flow away from the surface of the body to keep it more internalized - do via Arteriovenous anastomoses in hands - frostbite in toes, fingertips, nose, ears because cartilage - not lot blood flow

Aortic arch

Ascending aorta - first branch right and left coronary arteries taking oxy blood to heart Arch - because it is an arch - brachiocephalic artery heading off to right which then branches into right subclavian (heading to arm) and right common carotid (head); left common carotid artery; left subclavian; 3 branches off aortic arch, not 4 because we think humans symmetrical; first branch is brachiocephalic

2.Exchange nutrients, waste products, and gases

Circ system links respiratory system and digestive system to the rest of your body Respiratory system - where getting O2 into blood and out CO2 Digestive - where getting water, carbs, lipids, AA, almost all of your ions; need iron to make hemoglobin getting that from food into digestive system where crosses epithelial tissue and goes into circ system This means circ system is transporting all of these diff things to tissues where once gets to tissues has to offload product - glucose, water, O2, AA, fatty acids, tricglycerades Then at tissues also picks up waste products - via aerobic respiration body producing CO2 which diffuses out of tissues into blood to be transported and waste products - lactic acid in muscles, ammonioum (when metabolize AA produce ammonium (byproduct of metabolism of AA - transported then made into urea in liver then transported into kidneys where excreted) Major func of circ system

Biotransformation:

Toxic substances can be broken down by hepatocytes or can be made water soluble. To be transported in blood and excreted by the kidneys. Importantly have this Taking Toxic substances and breaking them down by hepatocytes (cells in the liver) making them water soluble so can be transported in the blood and excreted by the kidneys - detoxification

Capillary beds in intestines that empty into hepatic portal vein that nutrient-rich oxygen poor to cap beds in liver to go through detoxification

Capillaries draining GI tract → hepatic portal vein → liver sinusoids (large caps in liver) →hepatic veins Cap beds in digestive tract - eaten something and getting nutrients into capillary beds - diffusing across the epithelial tissue of intestines into cap beds, nutrient rich O2 poor blood then goes to cap beds in liver where it is detoxified - this nutrient rich oxygen poor goes to hepatic vein to IVC where then in heart; right side heart pumps the nutrient rich O2 poor blood to lungs where picks up oxygen and returns back to heart and now heart pumping oxygen and nutrient rich out to the body

Diff types of capillaries

Continuous Fenestrated Sinusoidal Sinusoids Venous sinuses

Coronary sinus (heart)

Deoxy from coronary veins go to sinus

Abdominal aorta and its branches

Descending aorta Celiac trunk - Splenic Superior mesenteric Inferior mesenteric Aorta below the diaphragm; branches out to a lot of diff structures in abdomen - need lot blood flow Splits into right and left common carotid arteries

Hepatic portal system

Digestive system Portal vessels - type blood vessels - connect two cap beds and no pump between them through rest of body Portal system: Hepatic portal- Blood entering the hepatic portal vein is rich with nutrients collected from the intestines, but may also contain toxic substances. Both nutrients and toxic substances will be regulated by the liver Capillary beds in intestines that empty into hepatic portal vein that nutrient-rich oxygen poor to cap beds in liver to go through detoxification

5.Directs blood flow

Directs all blood to the appropriate parts of body Vasoconstriction, dilation, and sphincters responsible for that

3.Transport of hormones, components of the immune system, molecules required for coagulation, enzymes, nutrients, gases, waste products, etc.

Hormone - released into circ system where transported Various components of your immune system - vaccines producing antibodies in the blood so blood is transporting antibodies; have WBC that are responsible for your defense against pathogens and they are transported in blood Coagulation - fibrinogen and those clotting factors present in blood All sorts enzymes

Flow

How is blood flowing through the body Hematocrit - is a very good indicator of viscosity of blood; stickiness of blood which influences flow Also influenced by flow smoothly and easily through nice round, uniform pipe but will have constrictions - happens

Elastic arteries

Elastic fibers present in arteries - lot of elastin Means return to an original resting shape; can stretch it out then it will snap back - elastic They stretch out then snap back - throbbing - stretching out then snapping back - feel elastic artery in neck These diverge/split into muscular arteries Biggest elastic artery is aorta - branch into muscular arteries which branch into arterioles which then branch into a large number capillary beds Or conducting arteries More elastic Like interstates - they are there to get max number of RBC out to tissues as fast as possible Largest diameter so highest pressure Typically are closest to heart Systole - ventricles contracting pushing blood out and have high pressure and as feel pulse can feel it push out Lot more elastic tissue than muscle Largest diameters, pressure high and fluctuates between systolic and diastolic. More elastic tissue than muscle. Relatively thick tunica intima, thin tunica adventitia and tunica media Tunica media mostly elastic CT; recoil when stretch, which prevents blood pressure from falling rapidly

Internal elastic membrane. Fenestrated layer of elastic fibers.

Elastic membranes that then leads to tunica media

Tunica intima

Endothelium - epithelial tissue that opens into internal part of body; opens internally Innermost layer Intima - Most intimate; inside Basement membrane Lamina propria (C.T. layer) - this means CT layer Internal elastic membrane. Fenestrated layer of elastic fibers.

Structure of capillary walls

Form fits func - way something is structured fits its job; happening in tissues and going on

Aortic arch:

Forms an arch Literally arches over - look like arch Noticeable not symmetrical arching posteriorly and to the left and has three branches coming off of it 3 branches Brachiocephalic artery Left common carotid Left subclavian artery Arches over then descends

Venules

From capillaries to here Little veins Ule - little Fuse into small drain capillary network. Endothelial cells and basement membrane with a few smooth muscle cells. As diameter of venules increases, amount of smooth muscle increases. Take blood away from tissues Minimal and small basement membrane with arteries venules taking blood away from tissue and very small minimal basement membrane in comparison to arteries Diameter in the venules increases with increase SM muscle These Fuse into small veins

Small veins

From venules to medium Smooth muscle cells form a continuous layer. Addition of tunica adventitia made of collagenous connective tissue Little bit more CT and smooth muscle Fuses into medium

Left subclavian artery

Going out to left arm

Brachiocephalic artery

Going out to right

Rise in pH

H+ decreased so response is slow HR

Muscular arteries

Have a lot of smooth muscle Split into arterioles Main city streets - have a lot smooth muscle or medium arteries Splenic, femoral - main ones Smaller muscular arteries Tunica media thick layer of smooth muscle; regulate blood flow to diff regions of body Regulate blood flow to the tissues

Some blood vessels innervated by myelinated fibers and act as baroreceptors that monitor stretch and detect changes in blood pressure

Have baroreceptors - reflex; have to know what going on in blood vasculature Myelinated fibers that monitor stretch and detect changes in BP

Fenestrated

Have pores. Endothelial cells have numerous fenestrae. Fenestrae are areas where cytoplasm is absent and plasma membrane is made of a thin, porous diaphragm. Highly permeable. E.g., intestinal villi, ciliary process of eye, choroid plexus, glomeruli of kidney Fenestrae - are pores/holes Means have little holes Found capillary beds with little holes in places where need get lot stuff from membranes into tissues Inside intestines - getting into body: carbs, AA, lipids, all of your nutrients so have very porous/fenestrated capillary beds Ciliary in eye - responsible for producing lot fluid in eye Choroid plexus - in brain that is responsible to produce CSF - making fluid to protect brain so need that Glomeruli of kidney - kidneys filter your blood, the glomeruli are the filter - have fenestrated capillaries there because want to get material out blood and fluid into kidneys for filtering

Route RBC leaving heart into tissue

Heart -> Elastic arteries leaving heart → branching to muscular arteries → branching to arterioles → branching to metarterioles → thoroughfare channels → past precapillary sphincters → through arterial caps → through venous caps → fuse venules → fuse small veins → fuse med/lg veins and return back to heart

Structural features of blood vessels

Heart to Arteries to capillaries which fuse into veins which go back to the heart Arteries Capillaries: Veins:

Flow through thoroughfare channel fairly consistent while flow through arterial capillaries is intermittent

In cap bed have one main channel, thoroughfare channel, where have fairly consistent blood flow Relatively steady blood flow through the channel

Blood vasculature has neural innervation: nerves innervating smooth muscle of blood vessels

In gen almost always sympathetic; most sig amounts of innervation

Basement membrane

Is a major feature of epithelial tissue

Sinusoids

Large diameter sinusoidal capillaries. Sparse basement membrane. E.g., liver, bone marrow. Larger diameter that Sinusoidal capillaries Very little basement membrane Liver - produces large number albumins, globulins, and fibrinogen proteins - making very large molecules; also in process of getting rid of damaged RBC Bone marrow - make RBC - get them into circ system and get them into there through pores in capillary ped; exchange of immature cells going into the blood and bone marrow Larger pores

Sinusoidal

Large diameter with large fenestrae. Less basement membrane. E.g., endocrine glands (large molecules cross their walls). Oidal - Little sinuses Larger in diameter and means large fenestrae Seen in endocrine glands - making big molecules, big protein hormones, glycoprotein hormones, etc; making big molecules that have to get into the blood

Substances move through capillaries by diffusion:

Lipid-soluble and small water-soluble molecules through plasma membrane Larger water-soluble molecules pass through fenestrae or gaps between endothelial cells.

Other vessel types

More diff types blood vessels than arteries, capillaries, and veins Separate types of blood vessels Vasa vasorum: Portal veins: Arteriovenous anastomoses:

Capillary network

Muscular arteries branches into aterioles which branch into capillaries - step in arterioles branching into capillaries Blood flows from arterioles through metarterioles, then through capillary network Flow through thoroughfare channel fairly consistent while flow through arterial capillaries is intermittent Smooth muscle in arterioles, metarterioles, precapillary sphincters regulates blood flow Diffusion into and out of capillaries moves substances throughout the body. Blood flows from arterioles through metarterioles, then through capillary network Blood flows to arteriole end of cap bed and BHP and TOP are going to cause fluid to leave cap bed and go into tissues Venule side of cap bed - where have THP and BOP causing fluid to move from tissues back into venule side Flow through thoroughfare channel fairly consistent while flow through arterial capillaries is intermittent Smooth muscle in arterioles, metarterioles, precapillary sphincters regulates blood flow

Arteries of upper limb

Need to know: Subclavian, axillary and brachial - are continuous tubes/blood vessels from subclavian to arm and do have branches of brachial artery Are the 3 continuous blood vessels of the arm in correct anatomical order Identifying things go back to anatomical position Continuous tubes from subclavian - turns into axillary artery when in armpit which then flows into the brachial artery lot branches in the arm because have collateral circulation in arm; damage to one part can still have blood flow there; have multiple ways of getting blood into your arms Subclavian artery and axillary - shoulder, chest, and back Brachial artery - arm

Continuous

No gaps between endothelial cells. No fenestrae. Less permeable to large molecules than other capillary types. E.g., muscle, nervous tissue. Simple squamous epithelial cells do not have pores or gaps/fenestrae No gaps in epithelial cells Found in tissues where not a lot exchange of things so have them in muscles and nervous tissue - exchange gases and nutrients but not producing really big molecules in tissue or big molecules do not need to go to tissues; want to carefully regulate, blood-brain barrier, what goes into and out NS - NS gets damaged then not repaired Muscle tissue - very little repair; 1-1.7% can be prepared so sig damage to muscle or NS tissue is prob So want carefully regulate it

Blood entering the hepatic portal vein is rich with nutrients collected from the intestines, but may also contain toxic substances. Both nutrients and toxic substances will be regulated by the liver

Nutrients: Biotransformation:

Arterioles

Ole - means small Smaller arteries From muscular arteries to here Transport blood from small arteries to metarterioles, middle set of Arterioles, to capillaries Transport blood from small arteries to capillaries Smallest arteries where can differentiate the three tunics Metarterioles and arterioles cannot see the three layers Lot smooth muscle too and capable of a lot vasoconstriction and vasodilation Once at tissue site, arterioles kick in and really regulate pressure within tissues Too low not enough blood in tissues Too high pressure is an issues - too much hydrostatic pressure, pressure pushing blood into tissues, going to have have accumulation fluid - edema; time stays means amount fluid accumulated Careful regulation of fluid into tissues - want this Like small arteries, capable of vasoconstriction and dilation Arterioles regulate pressure through tissues Lead to capillaries

Vessels of penis and clitoris innervated by parasympathetic

One major exception in body - blood vessels in genitalia For sexual stimulation to occur also have to have some vasodilation; Erection - vessels have to vasodilate Erecetile Disfunction - related to blood vasculature and probs and increasing vasodilation and vasoconstriction changing those can affect cardiac effection

Diffusion into and out of capillaries moves substances throughout the body.

Out on arteriole end and in on venule bed blood through metarteriole and maintain steady flow through channel and then pass through sphincter on arteriole end capillary bed which flow into venous capillary bed then into venules; smooth muscle in arterioles, metarterioles, precapillary sphintcters regulate blood flow going into tissues - diffusion out of blood on arteriole end and into on venules capillary end

Systemic circulation: veins

Returning blood from body to right atrium Carrying oxygenated blood from LV out to rest of body; systemic circulation also getting water out to all tissues; get water into body by drinking it; way get all macronutrients need to consume them (water, carbs, AA, lipids) have to consume them - digestive system is where go into then move across epithelial tissue and then go into circ system - heart pumping out O2 and water and nutrients that tissues need throughout body Major veins Types of veins

Major veins

Returning deoxy blood to RA Coronary sinus (heart) Superior vena cava Inferior vena cava

Pulmonary circulation

Right side heart going out to the lungs From right ventricle into pulmonary trunk Pulmonary trunk divides into left and right pulmonary arteries to lungs. Two pulmonary veins exit each lung and enter left atrium

4.Regulate blood pressure

Plays role in this Heart is one of the major features that regulates BP but circ system plays a role as well

Interrelationships between

Pressure Flow Resistance

Arteries of the head and neck

Side view - Brachiocephalic that branches into right common carotid and right subclavian; 3 branches off of the aortic arch Humans not symmetrical in chest even though think are Need to know - Brachiocephalic, R Subclavian, R common carotid, Left Subclavian, Left common carotid

Medium or large veins

Small to Medium feeds into large Largest veins back to heart are SVC and IVC All three tunics are present; tunica media thin but can regulate vessel diameter because blood pressure in the venous system is low; predominant layer is tunica adventitia

or medium arteries

Smooth muscle allows vessels to regulate blood supply by constricting or dilating Most of the smaller unnamed arteries muscular arteries Thick walls due to 25-40 layers of smooth muscle. Since have more smooth muscle Also called distributing arteries because smooth muscle vasoconstrict and vasodilate to control blood supply; all part of regulating blood supply to tissues different regions of the body; smooth muscle constricts and dilates to regulate blood supply to tissues

Large veins.

Still have not lot elastic fibers, have smooth muscle but that CT is going to be the predominant layer - not special muscle in veins as do arteries Tunica intima is thin: endothelial cells, relatively thin layer of C.T and a few scattered elastic fibers. Tunica media has circularly arranged smooth muscle cells. Adventitia is predominant layer.

Types of veins

Superficial (closer to surface), deep (further from surface), sinuses (big)

Arteries

Take blood away from the heart 3 gen categories Elastic Muscular Arterioles

Veins:

Take blood back to heart - heart central pump; arteries to capillaries to veins thinner walls than arteries, contain less elastic tissue and fewer smooth muscle cells Structurally diff from arteries Thinner walls, less elastic tissue and less smooth muscle Less elastic tissue and less smooth muscle Venules Small veins Medium or large veins

Descending aorta

Thoracic aorta: Abdominal aorta:

Neural innervation of blood vessels

Unmyelinated sympathetic nerve fibers form plexi in tunica adventitia: vasoconstriction Vasoconstriction and vasodilation - smooth muscle very often has to have innervation by NS to constrict Blood vasculature has neural innervation: nerves innervating smooth muscle of blood vessels Organ not equally innervated by sym and para - sweat glands and Blood vessels - innervated primarily by sympathetic NS Unmyleinated sympathetic nerve fibers innervate blood vessels and causes vasoconstriction so stimulation causes vasoconstriction of blood vessels; increased epi released causing them to vasoconstrict Small arteries and arterioles in muscle have most sig amount of innervation to greatest extent Vessels of penis and clitoris innervated by parasympathetic Blood vasculature and sweat glands sympathetic stimulation with exception of genitalia need vasoconstriction Some blood vessels innervated by myelinated fibers and act as baroreceptors that monitor stretch and detect changes in blood pressure

Valves

Valves found in all veins greater than 2 mm in diameter. Unique to veins and not present in arteries Similar to SL valves Have cusps - blood pushing up and opens the cusp of blood and get backflow valve closes and snaps shut - not 100% - varicose veins part of that is that there are stretching veins and now valves will not come closed so now blood will pool See lot more valves in lower extremities because further from the heart so backflow is a bigger issue Folds in intima form two flaps that overlap. More valves in veins of lower extremities than in veins of upper extremities. Folds in tunica intima form the valves of veins, which allow blood to flow toward heart but not in opp direction

Peripheral circulation

aka vascular system aka blood vessels which transport blood through the body; with the exception spleen or if had damage to the body, blood does not leave the circ sys; blood moving through body it is staying in these tubes/blood vessels; bruise: broken some blood vessels and now blood accumulating outside of circ system; internal bleeding - damaged blood vessels and bleeding into internal body cavities; spleen diff - there have RBC leaving circ system and getting filtered; blood does not leave circ system unless there is an issue

Venous sinuses

are similar in structure but even larger. E.g., spleen Largest pores Sim to sinusoids Found in spleen - filters cells in blood; Kidneys - fluid Only place blood can leave circ system without damage; whole bunch reticular fibers present

Dynamics of blood circulation

blood circulation - there is an interrelationship between 3 things Interrelationships between Control mechanisms that regulate blood pressure and blood flow

Vasa vasorum:

blood vessels that supply the walls of arteries and veins. Penetrate vessel walls from the exterior. Branches of arteries. Arteries and veins have blood going through them at a relatively high speed for the best possible exchange of materials in tissue need it to be slow; just like going through drive through Blood through arteries and veins too quickly for exchange to take place so have these, which are special blood vessels that branch off major arteries and veins, that then take oxygenated blood to epitheial and CT of major blood vessels and take deoxy blood away from them; materials to there; typically deoxy going back into regular blood flow

Tunica externa (adventitia):

connective tissue, varies from dense regular near the vessel to loose that merges with the surrounding C.T.

Decrease CO2

decreases HR

Nutrients:

either taken up and stored or modified chemically and used by other parts of the body Liver also does imp things like takes up nutrients - part regulation of blood glucose involves glycogen broken into glucose released into circ system to maintain blood glucose levels constant and below 50 mg/dL = fatal; 70-140 right after eating and if not eaten in awhile 70-110; do not want to get too low; liver stores nutrients

Aorta

exits left ventricle and is divided into three parts Divided into 3 parts Leaving LV Aorta - large artery leaving heart; taking oxy blood from systemic side circ from LV out to body In generally humans biologically symmetrical; most major exception is chest and abdomen; to most efficiently fit material into limited space not going to have symmetry - in generally yes are symmetrical, split down middle and matches right and left but this is major exception Not all human body is bilaterally symmetrical - tend to think this; means cut right down middle and have matching halves; are symetrical and exactly sim Not case for abdominal and thoracic cavities - particularly the blood vessels in thoracic cavity/chest; complex animals/mammals see asymmetry in chest - idea is can pack more material in chest but the take away this is not symmetrical Ascending aorta: Aortic arch: Descending aorta

Blood

fluid moved through CV/circ system

Increase level of O2

high levels O2 do not need to get more blood to lungs for oxygenation so not increase HR

2 portal systems in body:

hypothalamhypophysial portal system - between hypo and AP, connects cap beds in hypo to cap beds in AP digestive system and liver = hepatic portal system - connect cap beds in intestines to cap beds in liver - liver serves as major detoxifier of the material consume; why people consume large amounts alcohol or makes you high is toxin is body metabolizing a toxin; you consume things and potentially a lot toxins in it so want detox that material before goes in circ system; so blood near the intestines (capillaries in intestines) and material diffuses from inside intestines and pass epithelial tissue into circ system but before start pumping that to rest of body goes liver where detox and then goes into VC and then pumped into the blood

Increase BP

increase HR keys increase BP - but not healthy response

Increase level CO2

increases HR

Abdominal aorta:

inferior to diaphragm. Ends as two common iliac arteries Dorsal blood vessel and nerve cord as opposed to ventral; run towards back of the body thens split into right and left common iliac arteries

Heart

is the pump

Heart ->

leads to Elastic arteries → that branch into muscular arteries → that branch into arterioles → that branch into capillaries → then fuse into venules → fuse into small veins → fuse into med that fuse into large veins and return blood back to the heart

Hepatic portal-

liver; hypothalamohypophyseal portal between hypothalamus and pituitary. Blood from intestines to the liver for detoxification All cap beds in intestines and this is where you are getting water, ions, glucose, AA, cholesterol, lipids, triglycerides/triglycerols All things consumed go into tube of digestive system and then broken down, external digestion where occurs outside body - not in tissues, and broken and absorbed across epithelial tissue that then goes into circ system - want make sure that material cleaned up and detoxed before going to the rest of body - not 100% but outside of extreme circumstances take blood to the liver and detox it; then nutrient rich, oxygen poor detox blood returns to vena cava to go back to heart Water consume moves through epithelial tissue in digestive system in multiple locations; getting water through circ system from digestive system; intestines - are getting carbs and AA going to liver and then detoxifying them then to IVC and return back to heart and now nutrient-rich, O2-poor blood pumped to lungs to pick up oxygen then oxygenated and nutrient rich blood from LV; that is hepatic portal system; lipids later on

Thoracic aorta:

portion in thorax Thorax or chest Diaphragm base of this cavity/lower point

Ascending aorta:

right and left coronary arteries branch from here Very first part of aorta Means it is going up/ascending Very first branch is right and left coronary arteries then arches over Right and left coronary arteries immediately branch and take oxy blood to cardiac tissue First branching of aorta are right and left coronary arteries

Capillaries:

site of exchange with tissues Where have exchange - get fluid, nutrients, waste products into and out of tissues Many so small that only couple RBC can get through at a time; very small Branching out and going into the tissues These will then fuse into veins; first fuse into venules Arterioles to capillaries Nutrients, ions, carbs, lipids, AA, micronutrients (Ca, Na) going into tissues Where have exchange Water going into tissues and oxygen going into tissues and ions, nutrients, macronutrients (carbs, lipids, AA), micronutrients (Ca, Na, K) going into tissues Going to have waste products going out Water-solube or lipid-soluble really dictates how it is going to go into tissue See have capillary wall have thin epithelial cells: thin simple squamous epithelium - free side is to the internal/inside; basement membrane - present Almost all epithelial tissue has a basement membrane except epithelial tissue in lymphatic sys Some capillary cells that can form fibrous tissue: fibroblasts and some macrophages and little undifferentiated smooth muscle - capillaries are made Lipid-soluble molecules can easily diffuses across plasma membrane into simple squamous epithelium in capillary through basement membrane into tissues - releasing steroid it can easily cross plasma membrane of cap beds; really small molecules, like O2 and CO2, easily diffuse; water-solube (water and proteins) have to think about how get those into tissues - do that structurally by diff type capillaries - named based on size of pores Capillary wall consists of endothelial cells (simple squamous epithelium), basement membrane and a delicate layer of loose C.T. Scattered pericapillary cells that are fibroblasts, macrophages or undifferentiated smooth muscle cells. Substances move through capillaries by diffusion:

Tunica media:

smooth muscle cells arranged circularly around the blood vessel. Middle layer Lot smooth muscle - can vasoconstrict and vasodilate Vasoconstriction: Vasodilation: Diameter of vessel determines how much volume of blood is present and influences BP

Vasoconstriction:

smooth muscles contract, decrease in blood flow (Volume/time) Making diameter of tube smaller decreasing amount blood present/decrease volume per unit time but increases BP Less blood leave tube but leaving with greater force because of vasoconstriction Make diameter smaller

Vasodilation:

smooth muscles relax, increase in blood flow (volume/time) Making diameter of tube larger Means more blood per unit area per time but it is going to decrease BP - BP is force on the walls of blood vessel; more bigger and more space means less compression More volume per unit time More blood out

layers of arteries and veins

tunica intima, tunica media, tunica externa

Portal system:

vascular system that begins and ends at a capillary bed with no pumping mechanism in between. Two cap beds connected by vessel and no pump

Portal veins:

veins that begin in a primary capillary network, extend some distance and end in a secondary capillary network without a pumping mechanism, such as the heart, between them. A vein that connects two capillary beds with no pump Heart - connection; heart, arteries, capillaries, lungs, veins, back to heart Have two capillary beds and no pump; portal vein connects from one capillary bed to another one 2 portal systems in body: