Circulation and BloodCirculation and Blood

The Circulatory The Circulatory SystemSystem

Functions of the Circulatory Functions of the Circulatory SystemSystem

1.1. a. To transport oxygen from the lungs to a. To transport oxygen from the lungs to the tissue cells of the body for cellular the tissue cells of the body for cellular respiration.respiration.

b. To transport COb. To transport CO22 from the tissue cells from the tissue cells of the body to the lungs for excretion.of the body to the lungs for excretion.

2.2. To distribute nutrients (due to digestion) To distribute nutrients (due to digestion) from the intestinal capillaries to all cells from the intestinal capillaries to all cells of the body.of the body.

3.3. To transport:To transport:a. Metabolic (nitrogenous) wastes to a. Metabolic (nitrogenous) wastes to the kidneys, including urea.the kidneys, including urea.b. Toxic substances to the liver.b. Toxic substances to the liver.

4.4. To distribute hormones to the To distribute hormones to the tissues/organs on which they act.tissues/organs on which they act.

5.5. To regulate body temperature:To regulate body temperature:

i. Donation of heati. Donation of heat

ii. Flow shuntingii. Flow shunting

6.6. To prevent blood loss through blood To prevent blood loss through blood clotting.clotting.

7.7. To protect the body from pathogens To protect the body from pathogens (viruses/bacteria) due to the circulation (viruses/bacteria) due to the circulation of antibodies and white blood cells.of antibodies and white blood cells.

DEFINITIONS: (see fig. 13.7 p. 246)DEFINITIONS: (see fig. 13.7 p. 246)

SystemicSystemic Circulation – Circulation –

Blood pumped by the LEFT side of Blood pumped by the LEFT side of the heart, which services the the heart, which services the entire bodyentire body except except the lungs. the lungs.

PulmonaryPulmonary Circulation – Circulation – Blood pumped by the RIGHT side Blood pumped by the RIGHT side

of the heart, which services of the heart, which services only only the the lungslungs..

‘‘Services’Services’ = provides O = provides O22 & nutrients, while carrying & nutrients, while carrying away COaway CO22 and other wastes. and other wastes.

The Major Components of the The Major Components of the Human Circulatory SystemHuman Circulatory System

I.I. Blood Vessels (5 types)Blood Vessels (5 types)

II.II. BloodBlood

III.III. HeartHeart

Blood Vessels Blood Vessels (refer to fig. 13.1 p. (refer to fig. 13.1 p. 240)240)

i.i. ArteriesArteries• Carry blood AWAY from the heart.Carry blood AWAY from the heart.• The thickest of all vessel-types; they possess The thickest of all vessel-types; they possess

three layers of tissue:three layers of tissue:

i. i. InnerInner epithelial layer (aka epithelial layer (aka endotheliumendothelium)- possesses elastic fibres and )- possesses elastic fibres and promote smooth flow.promote smooth flow.

ii. ii. MiddleMiddle smooth muscle layer (contracts smooth muscle layer (contracts or relaxes to regulate blood flow and pressure)or relaxes to regulate blood flow and pressure)

* the thickest layer* the thickest layer

iii. iii. OuterOuter fibrous (elastic) connective fibrous (elastic) connective tissue which serves a protective function as tissue which serves a protective function as well as allowing the artery to stretch and recoil.well as allowing the artery to stretch and recoil.

► The walls of major arteries (eg. The walls of major arteries (eg. AortaAorta) are so ) are so thick that they must be supplied by their own thick that they must be supplied by their own blood vessels.blood vessels.

► Arteries in the systemic circuit carry Arteries in the systemic circuit carry oxygenated oxygenated blood, blood, whereas arteries in the pulmonary circuit whereas arteries in the pulmonary circuit carry carry deoxygenated blood.deoxygenated blood.

► Notice the smaller inner diameter of arteries Notice the smaller inner diameter of arteries compared to that of veins – due to the thicker compared to that of veins – due to the thicker middle muscle layer in arteries.middle muscle layer in arteries.

Artery

Vein

ii. ii. ArteriolesArterioles• Small arteries (same structure, but smaller) into which Small arteries (same structure, but smaller) into which

arteries have been divided (just visible to naked eye).arteries have been divided (just visible to naked eye).• It is easier for blood to enter arteries than it is for it to It is easier for blood to enter arteries than it is for it to

exit them, due to the narrower nature of arterioles exit them, due to the narrower nature of arterioles creates noticeable blood pressure during both heart creates noticeable blood pressure during both heart contraction (systole) and relaxation (diastole), because contraction (systole) and relaxation (diastole), because the heart contracts again before enough blood has the heart contracts again before enough blood has flowed into the arterioles to completely relieve the flowed into the arterioles to completely relieve the pressure in the arteries.pressure in the arteries.

• This causes artery walls to elastically snap back and This causes artery walls to elastically snap back and forth (reason for our pulse). This impedance by the forth (reason for our pulse). This impedance by the arterioles is known as arterioles is known as peripheral resistanceperipheral resistance..

• As a consequence of elastic arteries working against As a consequence of elastic arteries working against peripheral resistance, there exists noticeable blood peripheral resistance, there exists noticeable blood pressure even during diastole, thus continuously driving pressure even during diastole, thus continuously driving blood into arterioles and eventually capillaries.blood into arterioles and eventually capillaries.

► Blood flow into arterioles, Blood flow into arterioles, and eventually capillaries, and eventually capillaries, is controlled in two ways is controlled in two ways (through nervous/endocrine (through nervous/endocrine signals) signals) (see fig. 13.2 p. 241):(see fig. 13.2 p. 241): Smooth muscles lining Smooth muscles lining

arterioles constrict, thus arterioles constrict, thus allowing less blood to enter; allowing less blood to enter; however, the arteriole does however, the arteriole does not fully close, so some blood not fully close, so some blood enters…enters…

The ‘back-up’ plan involves The ‘back-up’ plan involves precapillary sphincter precapillary sphincter muscles contracting or muscles contracting or relaxing in order to relaxing in order to respectively close or open respectively close or open access into capillary beds; if access into capillary beds; if closed off, blood flows to closed off, blood flows to venules through a venules through a thoroughfare channel thoroughfare channel so that so that it can reach more ‘useful’ it can reach more ‘useful’ areas quicker.areas quicker.

Why restrict access to Why restrict access to arterioles/capillaries???arterioles/capillaries???

► Example scenarios:Example scenarios: Cold weather; want blood (with heat) to flow to Cold weather; want blood (with heat) to flow to

core of body, not periphery…blood gets core of body, not periphery…blood gets shuntedshunted to to core through the ‘closing off’ of the peripheral core through the ‘closing off’ of the peripheral arterioles/sphincter muscles.arterioles/sphincter muscles.

Exercising; want blood (with OExercising; want blood (with O22 and nutrients) to and nutrients) to flow to skeletal muscles and heart, not the flow to skeletal muscles and heart, not the digestive tract or other non-necessary places…digestive tract or other non-necessary places…blood gets blood gets shuntedshunted to muscles. Good or bad to to muscles. Good or bad to exercise after eating and why?exercise after eating and why?

Relaxing; blood Relaxing; blood shuntedshunted to digestive tract to pick to digestive tract to pick up nutrients etc…up nutrients etc…

iii. iii. CapillariesCapillaries• Very tiny vessels with walls that are Very tiny vessels with walls that are oneone cell thick cell thick

(comprised of endothelium with a basement (comprised of endothelium with a basement membrane), which allow for efficient exchange of membrane), which allow for efficient exchange of substances.substances.

• Present in all bodily regions Present in all bodily regions thus, a cut thus, a cut anywhere will draw blood.anywhere will draw blood.

• Small diameter allowing for ‘single file’ passage of Small diameter allowing for ‘single file’ passage of red blood cells (again, helps with efficient red blood cells (again, helps with efficient exchange of, in this case, oxygen and COexchange of, in this case, oxygen and CO22).).

• Surround cells/tissues/organs like a ‘spider web’ or Surround cells/tissues/organs like a ‘spider web’ or ‘basket’.‘basket’.

• Capillaries are, at most, 0.2 μm away from any cell Capillaries are, at most, 0.2 μm away from any cell in the body (also aids the exchange of in the body (also aids the exchange of substances).substances).

• Certain capillary Certain capillary bedsbeds may be open or closed may be open or closed depending on demands & subsequent flow depending on demands & subsequent flow shunting.shunting.

In general, only about 5-10% of the body’s blood is in the capillaries at any one time.

iv. iv. VenulesVenules• Same structure as a vein (see below), only smaller.Same structure as a vein (see below), only smaller.• Collect blood from the capillaries and/or the Collect blood from the capillaries and/or the

thoroughfare channels and join/enlarge to form thoroughfare channels and join/enlarge to form veins.veins.

v. v. VeinsVeins• Thin-walled compared to arteries.Thin-walled compared to arteries.

-- this provides veins with a larger interior -- this provides veins with a larger interior diameter than arteries.diameter than arteries.

Thinner muscle layer

• Same three layers of tissue as arteries, but Same three layers of tissue as arteries, but the middle smooth muscle layer is thinner.the middle smooth muscle layer is thinner.

• Carry blood TOWARDS the heart.Carry blood TOWARDS the heart.• There exists a There exists a lowerlower blood pressure in veins blood pressure in veins

since they are since they are furtherfurther from the heart, and from the heart, and because of the larger interior diameter.because of the larger interior diameter.

• VALVES (one-way) assist with the upward VALVES (one-way) assist with the upward (against gravity) movement of blood back to (against gravity) movement of blood back to the heart (valves prevent the the heart (valves prevent the backflowbackflow of of blood). Malfunctioning valve blood). Malfunctioning valve varicose veinvaricose vein..

• Generally, 70% of the body’s blood is in the Generally, 70% of the body’s blood is in the veins…acts as somewhat of a blood resevoir.veins…acts as somewhat of a blood resevoir.

► Veins are located closer to the surface of the body Veins are located closer to the surface of the body than arteries, and they are surrounded by skeletal than arteries, and they are surrounded by skeletal muscle.muscle.

► The contraction of these skeletal muscles aid in The contraction of these skeletal muscles aid in blood flow through the veins (ie. The skeletal blood flow through the veins (ie. The skeletal muscles are the “hearts” for the veins).muscles are the “hearts” for the veins).

► In the systemic circuit, veins carry In the systemic circuit, veins carry deoxygenated deoxygenated blood.blood.

► In the pulmonary circuit, veins carry In the pulmonary circuit, veins carry oxygenated oxygenated bloodblood

ONE-WAY VALVES

Against Gravity

Blood Pressure and Blood Velocity Blood Pressure and Blood Velocity (fig. (fig. 13.9 p.248)13.9 p.248)

Blood Pressure (BP)Blood Pressure (BP): The hydrostatic pressure that : The hydrostatic pressure that blood exerts against the wall of a vessel.blood exerts against the wall of a vessel.

- highest in arteries due to their receiving of blood from highest in arteries due to their receiving of blood from the heart and due to the peripheral resistance created the heart and due to the peripheral resistance created by the smaller arterioles.by the smaller arterioles.

- that said, the BP within arteries varies with respect to that said, the BP within arteries varies with respect to the heart contracting (systole) and relaxing (diastole) the heart contracting (systole) and relaxing (diastole) systolic pressure is higher than diastolic pressure. systolic pressure is higher than diastolic pressure.

- BP begins to drop in arterioles as the blood simply gets BP begins to drop in arterioles as the blood simply gets further from the heart’s push, and it ‘spreads out’ further from the heart’s push, and it ‘spreads out’ more.more.

- BP in the capillaries is somewhat ‘medium’ in that BP in the capillaries is somewhat ‘medium’ in that even though the blood is far from the heart’s pump, even though the blood is far from the heart’s pump, the vessel openings are small and the walls are thin the vessel openings are small and the walls are thin allowing for a greater hydrostatic pressure against allowing for a greater hydrostatic pressure against them. them.

- By the time the blood reaches the veins, By the time the blood reaches the veins, its pressure is not affected much by the its pressure is not affected much by the heart due to its travel (and coupled ‘slow-heart due to its travel (and coupled ‘slow-down’) through tiny-diameter arterioles down’) through tiny-diameter arterioles and capillaries.and capillaries.

- Thus, very low BP in veins (the lowest, in Thus, very low BP in veins (the lowest, in fact):fact):- Blood is furthest from heart;Blood is furthest from heart;- Blood experienced extreme resistance within Blood experienced extreme resistance within

arterioles/capillaries;arterioles/capillaries;- Veins possess a very large (relative to Veins possess a very large (relative to

arteries) arteries) interiorinterior diameter. diameter.*BP can also increase with higher blood volume!

Blood VelocityBlood Velocity: the speed of blood moving : the speed of blood moving through vessels.through vessels.

- blood velocity is highest in the arteries due to the blood velocity is highest in the arteries due to the heart’s pump;heart’s pump;

- Blood velocity is lowest in the capillaries due to Blood velocity is lowest in the capillaries due to the single-file RBC flow through them and the the single-file RBC flow through them and the massive ‘spreading-out’ of the blood to the massive ‘spreading-out’ of the blood to the millions of capillary beds in the body;millions of capillary beds in the body;

- Blood velocity picks up again (but not to the Blood velocity picks up again (but not to the arterial level) in veins due to their large interior arterial level) in veins due to their large interior diameter (‘freeway’) and due to the action of diameter (‘freeway’) and due to the action of skeletal muscles to propel the blood back to the skeletal muscles to propel the blood back to the heart.heart.

* The * The cross-sectional areacross-sectional area (area of vessel wall in (area of vessel wall in contact with blood) of the vessels is greatest in contact with blood) of the vessels is greatest in capillaries and lowest in arteries and veins.capillaries and lowest in arteries and veins.

Normal BP = 120 mm Hg/80 mm Hg (systolic/diastolic).

Major Blood Vessels Major Blood Vessels (fig. 13.8 p. (fig. 13.8 p. 247)247)

Red vessels: usually arteries except for pulmonary circuit. Carry oxygenated blood.

Blue vessels: usually veins except for pulmonary circuit. Carry de-oxygenated blood.

1.1. AortaAorta – carries oxygenated blood out from the – carries oxygenated blood out from the Left Ventricle of the heart and services the entire Left Ventricle of the heart and services the entire systemic circuit by eventually branching into systemic circuit by eventually branching into various arteries. *Houses special nerves cells various arteries. *Houses special nerves cells (Aortic Bodies) that sense H(Aortic Bodies) that sense H++, CO, CO22, and O, and O22 levels levels in blood.in blood.

2.2. Coronary Arteries and VeinsCoronary Arteries and Veins – Arteries: – Arteries: branch off of the aorta and service the actual branch off of the aorta and service the actual heart muscleheart muscle (these vessels are seen on the (these vessels are seen on the surface of the heart) (*Blood in the heart’s surface of the heart) (*Blood in the heart’s chambers does not actually service the heart). chambers does not actually service the heart). Coronary Veins: carry ‘spent’ blood back to the Coronary Veins: carry ‘spent’ blood back to the heart’s chambers.heart’s chambers.

3.3. Carotid ArteriesCarotid Arteries – branch off of the aorta to – branch off of the aorta to service the brain/head region. Highly specialized service the brain/head region. Highly specialized contain special nerve cells (Carotid Bodies): contain special nerve cells (Carotid Bodies):

i. i. ChemoreceptorsChemoreceptors that detect O that detect O22, H, H++, , and COand CO22 content in the blood. content in the blood.ii. ii. Pressure ReceptorsPressure Receptors that detect blood that detect blood pressure changes.pressure changes.

-- the carotid artery can be used to measure -- the carotid artery can be used to measure one’s pulse.one’s pulse.

4.4. Jugular VeinsJugular Veins – opposite of carotid – opposite of carotid arteries. Carry blood from the brain/head arteries. Carry blood from the brain/head region back to the heart. Possess no region back to the heart. Possess no valves since gravity aids the flow.valves since gravity aids the flow.

5.5. Subclavian Arteries/VeinsSubclavian Arteries/Veins – service the – service the arms. Within the right subclavian vein arms. Within the right subclavian vein there is a union between the lymphatic there is a union between the lymphatic system and the circulatory system.system and the circulatory system.

6.6. Mesenteric ArteriesMesenteric Arteries – carry blood – carry blood from the aorta to the intestines (gut). from the aorta to the intestines (gut). Subdivide into villi capillaries.Subdivide into villi capillaries.

7.7. Hepatic Portal VeinHepatic Portal Vein – carries blood – carries blood from the intestines to the liver.from the intestines to the liver.

**HepaticHepatic = liver-related = liver-related

8.8. Hepatic VeinHepatic Vein – carries blood from the – carries blood from the liver back to the heart.liver back to the heart.

9.9. Renal Arteries/VeinsRenal Arteries/Veins – service the – service the kidneys.kidneys.

**RenalRenal = kidney-related= kidney-related

10. 10. Iliac Arteries/VeinsIliac Arteries/Veins – service the legs. – service the legs.

11.11. Anterior (Superior) and Posterior (Inferior) Anterior (Superior) and Posterior (Inferior) Vena Cava Vena Cava – collect/receive all of the blood from – collect/receive all of the blood from the various veins of the systemic circuit and the various veins of the systemic circuit and conduct it back into the right atrium of the heart.conduct it back into the right atrium of the heart.Anterior (Superior) Vena CavaAnterior (Superior) Vena Cava – collects blood – collects blood from above the heart.from above the heart.Posterior (Inferior) Vena CavaPosterior (Inferior) Vena Cava – collects blood – collects blood from below the heart.from below the heart.

12. 12. Pulmonary Arteries/VeinsPulmonary Arteries/Veins – only major vessels – only major vessels of the pulmonary circuit. Pulmonary arteries of the pulmonary circuit. Pulmonary arteries carry deoxygenated blood from the heart to the carry deoxygenated blood from the heart to the lungs. Pulmonary veins carry oxygenated blood lungs. Pulmonary veins carry oxygenated blood from the lungs back to the heart.from the lungs back to the heart.* Pulmonary Trunk* Pulmonary Trunk – first vessel to receive – first vessel to receive blood (bound for the lungs) from the heart. Splits blood (bound for the lungs) from the heart. Splits into two pulmonary arteries (one for each lung).into two pulmonary arteries (one for each lung).

Aorta

The aorta and the coronary system…heart not shown.

BloodBlood► Made up of, and will separate into, two Made up of, and will separate into, two

components:components:

1.1. PlasmaPlasma – comprises 55% of the blood – comprises 55% of the blood volumevolume

2.2. Formed ElementsFormed Elements (Cells) – comprise (Cells) – comprise 45% of the blood volume.45% of the blood volume.

- - includes Red Blood Cells (RBCs), includes Red Blood Cells (RBCs), White Blood Cells (WBCs), and Platelets White Blood Cells (WBCs), and Platelets (which aren’t whole cells, but cell (which aren’t whole cells, but cell fragments).fragments).

*fig. 13.10 p. 249.*fig. 13.10 p. 249.

PlasmaPlasma- 90-92% water 90-92% water maintains blood volume maintains blood volume

and pressure; transports substances due to and pressure; transports substances due to its flowing and polar nature. Primarily its flowing and polar nature. Primarily absorbed by small and large intestines.absorbed by small and large intestines. *Regulates temperature too!*Regulates temperature too!

- 7-8% Plasma Proteins 7-8% Plasma Proteins maintain blood maintain blood O.P./volume, etc. Produced by the liver. O.P./volume, etc. Produced by the liver. Too large to leave blood through Too large to leave blood through capillaries.capillaries.- Albumins: maintain BP and blood volume; Albumins: maintain BP and blood volume;

transport bilirubin.transport bilirubin.- Immunoglobulins: antibodies that fight infection Immunoglobulins: antibodies that fight infection

(pathogens); transport cholesterol. (pathogens); transport cholesterol. - Fibrinogen/Prothrombin: aid in blood clotting.Fibrinogen/Prothrombin: aid in blood clotting.

- <1% Other stuff: <1% Other stuff: - Salts/Electrolytes (minerals): maintain OP and Salts/Electrolytes (minerals): maintain OP and

BP, pH, and aid in metabolism in many ways; BP, pH, and aid in metabolism in many ways; absorbed primarily in small intestine.absorbed primarily in small intestine.

- Gases: oxygen/carbon dioxide from Gases: oxygen/carbon dioxide from lungs/tissues respectively;lungs/tissues respectively;

- Nutrients: fats, glucose, amino acids from Nutrients: fats, glucose, amino acids from small intestine;small intestine;

- Nitrogenous wastes: urea and uric acid from Nitrogenous wastes: urea and uric acid from liver;liver;

- Hormones to aid bodily processes;Hormones to aid bodily processes;- Vitamins from small intestine to aid in Vitamins from small intestine to aid in

enzymatic reactions.enzymatic reactions.

Formed ElementsFormed ElementsRed Blood Cells (RBCs) – fig. 13.11 p. 250Red Blood Cells (RBCs) – fig. 13.11 p. 250- aka aka erythrocyteserythrocytes, RBCs are the most numerous of the , RBCs are the most numerous of the

blood cells; there exist about 25 trillion in our (on blood cells; there exist about 25 trillion in our (on average) 5 L of blood (in fact, RBCs comprise 99% of average) 5 L of blood (in fact, RBCs comprise 99% of blood cells).blood cells).

- StructureStructure promotes promotes FunctionFunction::- RBC is a biconcave disk (flatter in center) allowing RBC is a biconcave disk (flatter in center) allowing

them to thread through capillaries very efficiently and them to thread through capillaries very efficiently and providing them with a large SA to Volume ratio.providing them with a large SA to Volume ratio.

- Lack nuclei and mitochondria to help limit size – Lack nuclei and mitochondria to help limit size – without nuclei, RBCs live (on avg.) 120 days and are without nuclei, RBCs live (on avg.) 120 days and are then destroyed (by phagocytic cells through then destroyed (by phagocytic cells through phagocytosis) in the liver or spleen. Without phagocytosis) in the liver or spleen. Without mitochondria, RBCs metabolize anaerobically so that mitochondria, RBCs metabolize anaerobically so that they do not use the very oxygen that they carry, in they do not use the very oxygen that they carry, in order to make their ATP energy.order to make their ATP energy.

- Large SA:Volume promotes RBCs’ main function: to Large SA:Volume promotes RBCs’ main function: to transport Otransport O22 in the blood and have it diffuse into/out in the blood and have it diffuse into/out of them at the lungs and tissues, respectively. (RBCs of them at the lungs and tissues, respectively. (RBCs also carry COalso carry CO22 and H and H++, but to a lesser extent than O, but to a lesser extent than O22).).

- Each RBC houses about 250 million molecules of Each RBC houses about 250 million molecules of hemoglobinhemoglobin, an iron-containing protein responsible , an iron-containing protein responsible for carrying Ofor carrying O22 (primarily) – hemoglobin is purple-red (primarily) – hemoglobin is purple-red without Owithout O22 and bright red with O and bright red with O22. Hemoglobin is . Hemoglobin is made up of four tertiary proteins (two alpha, two made up of four tertiary proteins (two alpha, two beta), four heme groups, and four Febeta), four heme groups, and four Fe2+2+ ions. It can ions. It can associate with, and carry, four Oassociate with, and carry, four O22 molecules at any molecules at any one time (more in Respiration Unit).one time (more in Respiration Unit).

- Hemoglobin’s iron is sent to the bone marrow to be Hemoglobin’s iron is sent to the bone marrow to be reused when RBCs are destroyed; heme becomes reused when RBCs are destroyed; heme becomes bilirubin (released in bile pigments); and the alpha bilirubin (released in bile pigments); and the alpha and beta chains are hydrolyzed and the amino acids and beta chains are hydrolyzed and the amino acids reused.reused.

Manufacture of RBCsManufacture of RBCs (fig. 13.12 p. 251) (fig. 13.12 p. 251)

- RBCs are formed in the BONE MARROW of large - RBCs are formed in the BONE MARROW of large bones:bones:

- bones of the chest (ribs), upper arms - bones of the chest (ribs), upper arms (humerus), upper legs (femur), hips, skull.(humerus), upper legs (femur), hips, skull.

- multipotent stem cells in the bone marrow - multipotent stem cells in the bone marrow become become erythroblastserythroblasts (RBC precursor), which (RBC precursor), which lose their nuclei, gain hemoglobin, and mature lose their nuclei, gain hemoglobin, and mature or differentiate into an erythrocyte (RBC).or differentiate into an erythrocyte (RBC).

- Certain hormonal/nervous signals ‘tell’ stem - Certain hormonal/nervous signals ‘tell’ stem cells how to develop as they have the ability to cells how to develop as they have the ability to form any type of blood cell.form any type of blood cell.

Control of RBC ProductionControl of RBC Production- Oxygen-sensitive chemoreceptors in various Oxygen-sensitive chemoreceptors in various

locations (medulla oblongata, aortic/carotid locations (medulla oblongata, aortic/carotid bodies, renal artery, hepatic vein) sense low Obodies, renal artery, hepatic vein) sense low O22 levels in the blood.levels in the blood.

- Stimulus sent to kidney to produce the hormone Stimulus sent to kidney to produce the hormone erythropoietin (EPO)erythropoietin (EPO), which stimulates production , which stimulates production of RBCs in bone marrow, and acts to slow the rate of RBCs in bone marrow, and acts to slow the rate of RBC destruction – this allows for more Oof RBC destruction – this allows for more O22 to be to be carried in the blood as we exhale plenty of it.carried in the blood as we exhale plenty of it.

- Once OOnce O2 2 levels are restored, chemoreceptors send levels are restored, chemoreceptors send negative feedback message to kidney to cease negative feedback message to kidney to cease release of erythropoietin.release of erythropoietin.

- Some causes of lower than average OSome causes of lower than average O22 levels: levels: exercise, loss of blood, high altitudes, poor exercise, loss of blood, high altitudes, poor hemoglobin/RBC production/formation (anemia)hemoglobin/RBC production/formation (anemia)- Most common cause of anemia is iron deficiency.Most common cause of anemia is iron deficiency.

Blood TypingBlood Typing

A couple of definitions:A couple of definitions:

AntigenAntigen – a foreign substance that elicits a – a foreign substance that elicits a defensive response from the immune system. defensive response from the immune system. In the case of RBCs, an antigen (if present) is a In the case of RBCs, an antigen (if present) is a protein that is displayed on the surface of the protein that is displayed on the surface of the cell and serves as an ID tag for that cell.cell and serves as an ID tag for that cell.

AntibodyAntibody – an antigen-binding protein, – an antigen-binding protein, produced by certain WBCs, that bind to certain produced by certain WBCs, that bind to certain antigens, ‘tagging’ them for destruction by antigens, ‘tagging’ them for destruction by phagocytic WBCs.phagocytic WBCs.

FYI: Anti-gen = Antibody

generating

ABO SystemABO System

Key Points: If antibody B (say) comes into contact with antigen B, it will tag each B antigen for destruction (the blood clumps and causes flow problems).

Antibodies exist only in the plasma.

Donated blood is made up of primarily RBCs only.

So…a person with AB blood can receive blood from anyone; whereas, a person with type O blood can donate to anyone.

AB = Universal Recipient; O = Universal Donor.

See table 14.2 p. 278 for Pop’n distribution

O most common, then A, then B, then AB…

Another Antigen: Rh protein (see fig. 14.13, p. 279 – excellent figure!)

An Rh antigen is present in people with Rh+ blood (no antibody), and is not present in people with Rh- blood (also, no antibody). If a person who is Rh- is exposed to Rh+ blood, antibodies will then be produced that will tag each Rh+ RBC for destruction…happens often during a pregnancy where a mother is Rh- and her fetus is Rh+…the fetus’ RBCs move across the placenta (late in the pregnancy or during delivery, when the placenta begins to break down) and stimulate the mother to produce Rh antibodies which can then cross the placenta (usually in a subsequent pregnancy) to tag and destroy the fetus’ RBCs. Solved by injection of anti-Rh antibodies during, or just after, delivery of ‘first’ child, which destroy any Rh+ RBCs that entered the mother’s system, leading to prevention of production of Rh antibodies in mother and ‘saving’ second fetus if he/she is Rh+ as well.

White Blood Cells (WBCs) White Blood Cells (WBCs) (fig. 13.10 p. 249)(fig. 13.10 p. 249)- aka aka LeukocytesLeukocytes- Can be granular or agranular.Can be granular or agranular.- Very large in size (have a nucleus) relative to RBCs Very large in size (have a nucleus) relative to RBCs

and platelets.and platelets.- In general, WBCs fight infection and resist disease In general, WBCs fight infection and resist disease

by aiding in the development of immunity.by aiding in the development of immunity.- Produced in the bone marrow from the same stem Produced in the bone marrow from the same stem

cells as RBCs, but follow a different developmentalcells as RBCs, but follow a different developmental pathway.pathway.

Two Classes and Five Types:Two Classes and Five Types:

Class I: Granular Leukocytes (filled with vesicles of Class I: Granular Leukocytes (filled with vesicles of enzymes that ‘defend’ against ‘invaders’)enzymes that ‘defend’ against ‘invaders’)

a. a. BasophilsBasophils – release histamines that cause – release histamines that cause allergic reactions (clotting of area, dilation of allergic reactions (clotting of area, dilation of vessels to allow neutrophils/monocytes to arrive).vessels to allow neutrophils/monocytes to arrive).

b. b. EosinophilsEosinophils – attack parasites by releasing – attack parasites by releasing substances that kill them.substances that kill them.

c. c. NeutrophilsNeutrophils – attack and engulf foreign – attack and engulf foreign invaders, destroying themselves in the invaders, destroying themselves in the process (pus); aka phagocytes. Most process (pus); aka phagocytes. Most numerous (60-70% of WBCs).numerous (60-70% of WBCs).

Class II – Agranular Leukocytes Class II – Agranular Leukocytes

a.a. Monocytes (Macrophages) – like neutrophils Monocytes (Macrophages) – like neutrophils except that they possess pseudopodia except that they possess pseudopodia (‘arms’) that can extend out to capture (‘arms’) that can extend out to capture invaders. As well, they may live through an invaders. As well, they may live through an encounter and even act to engulf dead encounter and even act to engulf dead neutrophils.neutrophils.

b.b. Lymphocytes (T and B) – produce antibodies Lymphocytes (T and B) – produce antibodies that tag specific invaders for destruction.that tag specific invaders for destruction.

Colony-stimulating Factors (CSFs) are secreted by ‘living’ WBCs to promote the WBC developmental pathway, leading to an increase in WBC production (akin to EPO for RBCs).

RBC = R

Agranular WBC (Monocyte) = N

Granular WBC (Eosinophil) = E

Platelets (fig. 13.14 p. 254) – Cell FragmentsPlatelets (fig. 13.14 p. 254) – Cell Fragments- regulated by hormone regulated by hormone thrombopoietinthrombopoietin, which is , which is

released by the liver and/or kidneys when platelet released by the liver and/or kidneys when platelet counts are low.counts are low.

- They lack a nucleus; are fragments of They lack a nucleus; are fragments of megakaryocytesmegakaryocytes, which are derived from bone , which are derived from bone marrow stem cells.marrow stem cells.

- Play a major role in Play a major role in blood clottingblood clotting; when a blood ; when a blood vessel is broken, it must be repaired. In order for vessel is broken, it must be repaired. In order for the tissue to regenerate, the blood flow through the tissue to regenerate, the blood flow through the cut must be stopped; a the cut must be stopped; a clotclot serves this serves this function.function.

- When a cut occurs, platelets congregate and stick When a cut occurs, platelets congregate and stick to the irregular surface created by the cut.to the irregular surface created by the cut.

- If it is a If it is a minorminor cut, this congregation clogs the hole. cut, this congregation clogs the hole.- If it is a If it is a majormajor cut, a sequence of events takes cut, a sequence of events takes

place:place:

- Platelets and damaged tissue cells release enzyme Platelets and damaged tissue cells release enzyme Prothrombin ActivatorProthrombin Activator, which, along with Ca, which, along with Ca2+2+ ions in ions in the plasma, acts to convert the plasma protein the plasma, acts to convert the plasma protein prothrombinprothrombin to the protein to the protein thrombinthrombin..

- The liver produces prothrombin with help from The liver produces prothrombin with help from Vitamin K (a lack of K in diet leads to hemorrhagic Vitamin K (a lack of K in diet leads to hemorrhagic disorders).disorders).

- Thrombin then acts as an enzyme to convert the Thrombin then acts as an enzyme to convert the plasma protein plasma protein fibrinogenfibrinogen to to fibrinfibrin, a thread , a thread (filament)-like protein that winds around the platelet (filament)-like protein that winds around the platelet congregation to stabilize it. Fibrin threads also congregation to stabilize it. Fibrin threads also capture RBCs that act to further plug holes in the clot.capture RBCs that act to further plug holes in the clot.

- The fibrin web eventually contracts (like actin fibers) The fibrin web eventually contracts (like actin fibers) to pull the tissue back together (forms a scab).to pull the tissue back together (forms a scab).

- Tissue repair occurs beneath scab.Tissue repair occurs beneath scab.- Once repairs are complete, the clot is released and Once repairs are complete, the clot is released and

destroyed by the enzyme destroyed by the enzyme plasminplasmin (present in blood). (present in blood).

Types of Body FluidsTypes of Body Fluids

NameName CompositionComposition

BloodBlood Formed elements Formed elements and plasmaand plasma

PlasmaPlasma Water, proteins, Water, proteins, salts, etc.salts, etc.

SerumSerum Plasma minus Plasma minus fibrinogen (after fibrinogen (after clotting)clotting)

Tissue (ECF) Tissue (ECF) fluidfluid

Plasma minus Plasma minus proteinsproteins

LymphLymph Tissue Fluid in Tissue Fluid in lymphatic vesselslymphatic vessels

Capillary ExchangeCapillary Exchange – – fig. 13.15 p. 255fig. 13.15 p. 255

► The diffusion of water, hormones, OThe diffusion of water, hormones, O22, nutrients, CO, nutrients, CO22, , and other wastes occurs between the capillaries and and other wastes occurs between the capillaries and the ECF (and eventually, body cells).the ECF (and eventually, body cells).

► Capillaries are very close (at most 0.2 micrometers) Capillaries are very close (at most 0.2 micrometers) to body cells, and their walls are one-cell thick to body cells, and their walls are one-cell thick (easy (easy exchange).exchange).

► Water is the transfer medium for the substances Water is the transfer medium for the substances diffusing; it is the osmotic gradient that is followed. diffusing; it is the osmotic gradient that is followed. Thus, tonicity (Osmotic Pressure (OP)) and Blood Thus, tonicity (Osmotic Pressure (OP)) and Blood Pressure (BP) within capillaries are important to Pressure (BP) within capillaries are important to analyze.analyze.

► Ultimate goals: to move OUltimate goals: to move O22 and nutrients from blood and nutrients from blood into ECF, and eventually into cells; and to move COinto ECF, and eventually into cells; and to move CO22 and other wastes from ECF (originally from cells) into and other wastes from ECF (originally from cells) into capillaries.capillaries.

► Picture two regions of the capillary: the arterial end and Picture two regions of the capillary: the arterial end and the venous end.the venous end.

► At the arterial end, the BP > OP (in fact, BP = 30 mmHg At the arterial end, the BP > OP (in fact, BP = 30 mmHg and OP = 21 mmHg), so there is a net movement (9 and OP = 21 mmHg), so there is a net movement (9 mm Hg) of water and its contained stuff (Omm Hg) of water and its contained stuff (O22/nutrients) /nutrients) out of blood into the ECF. The movement of Oout of blood into the ECF. The movement of O2 2 and and nutrients follows their own conc. gradients. Most nutrients follows their own conc. gradients. Most water, Owater, O22, nutrients eventually enter cells., nutrients eventually enter cells.

► At the venous end, since the plasma proteins were At the venous end, since the plasma proteins were unable to move out of the capillary, and due to the unable to move out of the capillary, and due to the movement of water, OP > BP (in fact, OP = 21 mmHg movement of water, OP > BP (in fact, OP = 21 mmHg and BP = 15 mm Hg). Thus, there is a net movement and BP = 15 mm Hg). Thus, there is a net movement (6 mmHg) of water and its contained stuff (CO(6 mmHg) of water and its contained stuff (CO22/other /other wastes – following their own conc. gradient) from the wastes – following their own conc. gradient) from the tissue cells/ECF into the capillary for eventual disposal tissue cells/ECF into the capillary for eventual disposal from/by the body.from/by the body.

► The excess water (3 mmHg diff.) is taken up by The excess water (3 mmHg diff.) is taken up by lymphlymph capillaries…this excess can be greater if the [plasma capillaries…this excess can be greater if the [plasma proteins] is lower than average.proteins] is lower than average.

Ignore these numbers… pay attention to the premise only…

Now…see the Lymphatic System…