Advanced Human Physiology and Anatomy Marimar de la Cruz Review Prof. John Uscian Chapter XIII: The Circulatory System Test Date: October 12, 2010
• The circulatory system consist of a major pump; the heart, and various smaller, pump-‐like mechanisms that together move two forms of liquid tissues (blood and lymph) through an extensive network of tubular structures of the body.
o Functions:
delivery of nutrients to the cells
movement of wastes away from the cell hormone delivery
immunological properties clotting abilities
water and ion balance
distribution of heat of metabolism
o Two components: cardiovascular system, lymphatic system.
Cardiovascular System
• Made up of blood vessels and the heart.
• Two divisions through which the blood can travel: o Pulmonary circulation
Takes oxygen-‐poor blood from the heart to the lungs and then returns oxygen-‐ rich blood to the heart.
Right half of the heart ejects blood into it. o Systemic circulation
Takes oxygen-‐rich blood to all of the other organs of the body and returns oxygen-‐poor blood to the heart.
Left half of the heart ejects blood into it.
• Arteries take blood away from the heart and veins return blood to the heart. • Heart
o Two pumps that beat as one.
o Pericardium: fibrous membrane that surrounds the heart.
Pericardial cavity (area between the pericardium and the heart) is filled with pericardial fluid.
The pericardial fluid functions as a sort of lubricant that reduces friction between the beating of the heart and the surrounding tissues.
o The heart wall is compromised of three tissues:
Epicardium/ visceral pericardium: inner pericardium layer that comes in contact with the heart
Myocardium: heart muscle tissue made up of cardiocytes, thickest component of heart wall, confers capacity to contract.
Endocardium: simple squamous epithelium that makes up the inside lining of the heart, inner surface facilitates movement of blood, heart valves form from endocardium folds.
o Atria: upper chambers of the heart
right atrium: receives blood from superior and inferior vena cava and coronary sinus.
left atrium: receives blood from pulmonary veins interatrial septum: divides atria
o Ventricles: lower chambers of the heart, pump the blood into the arteries. right ventricle: pumps into the trunk of the pulmonary artery left ventricle: pumps blood into the aorta
interventricular septum: divides ventricles. thickest near the apex. o Atriventricular valves: ensure blood flows from atria to ventricles
o Papillary muscles: conical muscles arranged as pillar-‐like structures
chordae tendineae: connective tissue that attaches them to the atrioventricular valves
o Pulmonary valve: ensures blood flow from right ventricle to pulmonary artery o Aortic valve: ensures blood flow from left ventricle to aorta
o Aorta: largest artery of the body
o Pulmonary artery: directs blood from the right ventricle into the lungs. branches into right and left pulmonary arteries which go into the right and left lungs.
o Heart is supplied with oxygen-‐rich blood via the coronary arteries, this blood is returned to the right atrium by the coronary sinus and pulmonary veins. • Mechanical Events of the Heart Contraction Cycle:
o Left ventricle contracts with about seven times more force than the right ventricle. o Systole: ventricular contraction.
isovolumentric contraction: volume of the ventricles is constat but blood pressure increases as myocardium begins to contract after receiving a signal.
• atrial diastole: atrial fill with blood and increase volume as they relax. Ejection of blood from ventricles: BP continues to rise until threshold pressure
and the aortic valve opens, at almost the same instant the pulmonary valve opens.
Late systole: BP decreases until valves close o Diastole: ventricular relaxation.
BP in the ventricles continues to fall and atria continue to fill with blood until ventricular pressure falls below that of atria and atrioventricular valves open. the ventricles fill almost to capacity during the first third of diastole.
At termination of the 2/3 of diastole an action potential is generated by the sinoatrial node.
The action potential causes atria to contract (atrial systole), it travels through the interventricular septum into the walls of the myocardium causing the ventricles to enter systole and contract.
• Cardiocytes and other aspects of heart histology
o Heart skeleton is made up of fibrous connective tissue that extends from the atria to the ventricles.
This tissue lacks electrical-‐conducting properties. o Cardiocytes: heart muscle cells that make up the myocardium.
Binucleated
Actin and myosin filaments arranged in sarcomeres Striated but not as much as skeletal muscle.
Sarcoplasmic Reticulum less developed that in skeletal muscle. No dilated cisternae.
T tubules in close proximity to sarcoplasmic reticulum at fewer areas, resulting in less efficient transfer of action potential and slower onset of cardiocyte contraction.
Cannot function with a significant oxygen debt.
Enriched with mitochondria that aerobically produce sufficient ATP for the heart to function under normal physiological demands.
Joined to one another forming spiraled sheet-‐like structures.
Intercalated disks: bind adjacent cardiocytes, folds in their membranes enable adjacent cells to fit with increased contact area.
Desmosomes: cardiac tissue structures that join cardiocytes.
Gap junctions: small protein channels that join the cytosol of one cell to that of an adjacent one, enable ion flow and action potential progression.
• Heart Conducing System:
o Structured such that the action potential generated by the sinoatrial node stimulates the atria to contract first and the ventricles to follow.
o Progression of Action Potential: Action potential is generated by the SA node (located at the junction of the superior vena cava and the right atrium), it migrates along the intermodal pathways to the AV node making the atria contract. The action potential moves to the bundle of his (av bundle, located in the superior portion of the
interventricular septum) that diverges into two segments; the right and left bundle branches, these convey the action potential towards the apex through the
interventricular septum. The action potential reaches the purkinje fibers in the walls of the ventricles causing them to contract.
o The Purkinje fibers convey action potentials much more rapidly than other cardiac tissues because of the gap junctions and the well developed intercalated discs in the cardiocytes that comprise these fibers.
o The SA node is made up of cardiocytes that can produce action potentials at higher rates than other cardiocytes.
o It takes 0.04 seconds for the action potential to move from the SA node to the AV node and 0.1 seconds in getting to the bundle of his, a total 0.15 second delay that’s enough for the atria to contract completely before systole, where the ventricles contract starting from the heart’s apex.
• Cardiocyte/Myocardium Electrical Properties
o Depolarization of cardiocytes is a function the opening voltage-‐gated fast Na+ channels.
The action potential rises from -‐90mV to +20mV membrane potential at which point they close.
o Repolarization depends upon voltage-‐gated slow Ca+2 channels and voltage-‐gated K+
channels. Voltage-‐gated K+ channels open and drops the membrane potential from
+20mV to 0mV, at almost the same time the Ca+2 channels open and the influx of
calcium slows the rate of repolarization lengthening it several hundred milliseconds (by bringing the positive charge into the cell and slowing the rate of K+ diffusion
through like charge repulsion).
o Full repolarization occurs when the voltage-‐gated Ca+2 channels close and the K+
channels open once again causing a sudden large outflux of potassium brings the membrane back to -‐90mV.
• Depolarization and Repolarization of the SA node
o Depolarization is initiated by the opening of voltage-‐gated slow Ca+2 channels open and
the action potential rises from -‐60mV to -‐40mV. This opens more calcium channels which rises the membrane potential to +20mV. At this point calcium channels close and voltage-‐gated K+ channels open inducing a rapid repolarization.
o Normally 70-‐80 depolarization-‐repolarization/heartbeats per minute.
o If SA node fails the AV node can take over but only produce 40 to 50 heartbeats per minute. If this fails the AV bundle can take over at 30 beats per minute.
o Ectopic pacemakers (ectopic foci) can take over the heartbeat under certain
circumstances in which the ectopic foci action potentials are enhanced, the SA node rythmicity is lowered or the conduction pathways from the SA node to other regions is reduced. Example: dead cells because of heart attack.
• Myocardium Refractory Period:
o Refractory Period: time during which a tissue cannot be activated after it has been stimulated.
o Two refractory periods associated with cardiocytes:
Absolute refractory period: stimulation cannot induce contraction.
Relative refractory period: stimulation has a lessened capacity to stimulate the cell to contract.
o The long plateau of the myocardium action potential (when Ca+2 channels are open)
enables it to rest and is an absolute refractory period. It plays a key role in preventing titanic contractions.
• Electrocardiogram: image obtained by an electrocardiograph of the heart’s electrical activity. o Three waves are normally produced:
P wave: depolarization of the atria
QRS wave: depolarization and signals the initiation of ventricular contraction T wave: ventricular repolarization
o Ion-‐rich fluids of the body propagate electrical activity in the body.
o Absence of P waves and a normal QT interval indicate atrial fibrillation in which the atria quiver. It is caused by ectopic pacemakers whose activities overwhelm the regular signals.
• Cardiac Output, Blood Pressure, and Heart Sounds
o At rest the heart pumps about 72 times per minute.
o Average Stroke Volume: volume of blood pumped through each cardiac cycle; end-‐ diastolic volume minus end-‐systolic volume.
o During rigorous physical activity the output may increase by five times.
o Cardiac reserve = additional amount of blood pumped when active -‐ amount of blood pumped when at rest.
o Blood Pressure is the result of the person’s cardiac output. o Mean Arterial Pressure: average blood pressure in the aorta
MAP = (Cardiac Output)(Peripheral Resistance: total resistance against which the blood is pumped)
o At the end of systole BP in the ventricles drop slightly below that of BP in the aorta causing a little bit of blood to be pushed back and making the aortic valve close. The closing of the valve causes a slught uncrease in aortic BP known as dicrotic notch or incisura. Through diastole aortic BP continues to decrease until it reaches 80 mm Hg prior to systole where it peaks at 120 mm Hg.
o Sound:
Lubb: closing of AV valves
Dub: closing of aortic and pulmonary valves • Heart Regulation
o Intrinsic Heart Regulation Factors: are independent of neural and hormonal factors The volume of blood returning to the heart (venous return) during diastole
affects the amount of blood that will be ejected from the ventricles during systole.
Increased venous return makes increased end-‐diastolic volume and increased stretch of the ventricular walls, known as preload. Greater preload means grater cardiac output.
Cardiac muscle like skeletal muscle exhibits a stretch vs. tension relationship but it is not stretched optimally prior to contraction under normal end-‐diastole volumes. When preload increases the muscle stretches more and the force of contraction and stroke volume are increased.
Starling’s law of the heart correlates the effectiveness of heart pumping with preload volume changes.
• Increased blood volume returned to heart; increased cardiac muscle stretch, increased contraction force, slightly increased heart rate, increased stroke volume and hence increased cardiac output. • Decreased blood volume returned to the heart; decreased cardiac
muscle stretch, slightly decreased heart rate, decreased stroke volume and hence decreased cardiac output.
When the right atrium is stretched to a greater extent as a result of greater blood being returned to it by the very large systemic veins, this stimulates the SA node (because it is located in the right atrium) to generate action potentials at a higher rate.
• The direct effect is to increase the Ca+2 of the cells comprising the SA
node making it produce more action potentials per unit time. There are forces that resist the ejection of blood from the ventricles like the
Afterload: aortic pressure force that the left ventricle must overcome to eject blood into this artery. The effect of afterload is insignificant as long as it doesn’t exceed 170 mm Hg, at this point the capacity of the ventricles to pump blood is negatively impacted.
Increased physical activity stimulates dilation of blood vessels so that an increase in blood volume movement results.
The contraction of skeletal muscles in the arms and legs and other areas in which veins are embedded accounts for most of the blood returned to the atria.
• During elevated physical activity they contract more often and therefore return more blood.
Valves within the veins prevent the backflow of blood o Extrinsic Heart Regulation Factors:
Two divisions of the autonomic nervous system innervate the heart. • Parasympathetic can decrease heart output by 10-‐20%, having an
inhibitory effect.
o The parasympathetic fibers are contained in the vagus nerve. Preganglionic extend to the ganglia in the heart wall and the Postganglionic extend to the SA and AV nodes, myocardium and coronary blood vessels.
o The heart can decrease to 20-‐30 beats per minute through more forceful stimulation than usual.
o If the rate of volume returned is constant stroke volume may be increased because the heart has more time to strech and fill with blood since it is beating slower.
o Releases acetylcholine which bind to acetylcholine-‐gated K+
channels causing it to open and thus hyperpolarizing the cells making it harder to depolarize them and giving required more time to achieve depolarization.
• Sympathetic can increase heart output by 50-‐100%.
o Fibers originate in thoracin nerves (T2, T3, T4) sinapse with cervical and upper thoracic ganglia, the postganglionic fibers extend to the myocardium.
o Called cardiac nerves they innervate the SA node, the AV node, cornary blood vessels, and ventricle myocardium.
o Causes the heart rate and contraction force to increase maintaining it at a 20% greater force than in the absence of these nerves.
o Heart rate can increase to 250-‐300 beats per minute.
o Stroke volume may increase as well but beyond a certain heart rate the blood volume will diminish because of a shortened diastole decreasing the stroke volume.
o Norepinephrine interacts with beta-‐andregenic receptors and causes increased production and accumulation of cAMP which increases cardiocyte permeability to Ca+2 through the opening
of cardiocyte membrane slow calcium channels.
Estrinsic factors can regulate: blood pressure, blood O2 levels, blood CO2 levels,
and blood pH by negative feedback. Hormonal Extrinsic Heart Regulation:
• Adrenal Medulla secretes epinephrine and norepinephrine due to sympathetic stimulation. The hormones travel through the bloodstream into the heart and bind to beta-‐andregenic receptors.
• Relationship of Heart Function to Maintenance of Homeostatic Parameters
Cardioregulatory center of the medulla oblongata receives messages from these receptors; it increases heart rate via its cardioacceleratory center and
decreases it through its cardioinhibitory center.
When bp increases, the vessel walls stretch, more signals are sent from baroreceptors to the cardioregulatory center, it sends action potentials along the parasympathetic nerve fibers stimulating a slower beating of the heart. When bp decreases, the vessel walls stretch less, less signals are sent, the
cardioregulatory center sends action potentials through the sympathetic nerve fibers.
This is termed the baroreceptor reflex.
o Chemoreceptor Reflex: detects changes in pH and CO2 levels through chemorepectors
that are located in the medulla oblongata.
A decrease in blood pH and increase in CO2 levels causes it to send messages
through sympathetic nerve fibers so that heart rate can be increased, increasing the rate at which CO2 can be exhaled.
There are chemoreceptors in the carotid and aortic arteries that detect low oxygen levels. These cause the heartbeat to decrease and narrow the blood vessels via vasoconstriction decreasing the heart’s need for oxygen.
o Ions can affect heart rate and stroke volume.
Increased levels of potassium can bring heart block, loss of action potentials. o Elevated temperature will somewhat increase heart rate.
• The Blood Vessels o Capillaries
Smallest and most extensive of all blood vessels. Average diameter of 7-‐9 µm, and 1mm in length.
Made up of a single cell layer of endothelial cells, simple squamous epithelial cells, the same ones that line the surface of the chambers of the heart and the innermost layer of all blood and lymph vessels.
The lumen of the capillaries is occupied by blood. The endothelial cells rest upon a basement membrane.
Adventitia: loose connective tissue surrounding the peripheral margins of and joining to the basement membrane.
Percapillary cells occur intermittently between the endothelial cells and the basement membrane. Fibroblasts, macrophages, undifferentiated smooth muscle cells.
Three forms of capillaries: • Continuous capillaries:
o Diameter: 7-‐9 µm.
o No spaces between endothelial cells which make this capillaries less permeable to molecules.
o Common throughout the body; nervous and muscle tissues. • Fenestrated Capillaries:
o Diameter: 0.07-‐0.1 µm
o Very porous and thin cell membrane due to fenestrae (pores in the endothelium wall).
o In tissues that require very permeable capillaries; intestinal villi, glomeruli of the kidney, CNS coroid plexus.
• Sinousoidal capillaries: o Diameter: 9 µm
o Less developed basement membrane.
o Larger fenestrae than fenestrated capillaries.
o Tissues that require large molecules to be moved; endocrine glands
o Sinusoids: sinusoidal capillaries with a large diameter Can move large molecules and even cells in some
common in liver or bone marrow. o Venous Sinuses:
Even greater diameter. Common in the spleen.
Large spaces occur between cells.
Arterioles supply blood to capillaries which form a network that occurs throughout tissues until the capillaries begin to form venules which return blood to the heart.
Arterial capillaries: occurring closest to arterioles Venous capillaries: occurring closest to venules
Precapillary Sphincters: smooth muscles that occur at the junction of an arteriole and a capillary, it will constrict or dilate the capillary by constriction and relaxation of the muscle.
o Arteries and Veins
Contain three tissue layers: • Tunica intima
o Endothelial cells surrounded by basement membrane o Sorrounded by a thin layer of connective tissue called the
lamina propia.
o Elastic fibers form the internal elastic membrane, which separates the tunica intima from the next layer; tunica media. • Tunica media
o Made up of smooth muscle cells, if they contract
vasoconstriction occurs and the volume of blood flow is diminished, if they relax vasodilation occurs and there is an increase in blood flow.
o Collagen and elastic fibers are also preset but vary in abundance according to each particular vessel.
• Tunica externa (tunica adventitia)
o Made up of connective tissue, it can be dense or loosely, that joins connective tissue surrounding the blood vessel.
o Arteries
Large elastic arteries • Closest to the heart
• Bp fluctuates according to diastole and systole
• Tunica media not well developed to prevent vasoconstriction. • Elastic tissue well developed facilitating expansion and contraction
between systole and diastole. • Tunica intima well developed. • Tunica adventitia thin.
Muscular arteries
• All arteries that are too small to be considered large elastic ones. • Thick walls
• Tunica media is made up of 25-‐40 layers of smooth muscle. • Elastic membrane of Tunica intima is well developed. • Tunic adventitia thick collagenous layer.
• Distributing arteries: medium-‐ sized muscular arteries.
Vasoconstriction and vasodilation enable them to regulate blood flow to various tissues and organs.
• The smaller ones of 40 µm in diameter have a tunica media comprised of 3-‐4 smooth muscle layers.
o Arterioles
Lead from small muscular arteries to capillaries. Three tunic layers are recognizable.
Tunica intima lacks elastic membrane.
Vasoconstriction and vasodilation regulate blood flow. o Veins and Venules
Venules:
• Receive blood from capillaries, to which they are similar in structure except for the diameter which is 40-‐50 µm for these vessels.
• Endothelium surrounded by a basement membrane.
• Smooth muscle cells surround the endothelium intermittently. • Nutrients can cross, but their capacity to do so decreases with
increasing vein size. Small veins
• 200-‐300 µm in diameter.
• Completely surrounded by a alayer of smooth muscle.
• Tunica adventitia comprised of collagenous connective tissue.
• All veins grater than 200 µm in diameter have valves that allow blood to flow only in the direction of the heart.
Medium veins: diameter in between small and large veins. Large veins:
• Transport bloos from medium veins to heart. • Thin tunica intima.
• Tunica adventitia best develop tissue layer, comprised of collagenous connective tissue.
o Vasa vasorum:
Small blood vessles that supply nutrients to the walls making up arteries and veins with diameter in excess of 1 mm by forming a network of capillaries in the tunica media and the tunica adventitia.
• Nervous Regulation of Blood Vessels:
o Sympathetic nerve fibers innervate the majority of blood vessel walls via unmyelinated nerve axons.
o Sympathetic stimulation causes vasoconstriction, parasympathetic stimulation results in vasodilation.
o Adjacent smooth muscle cells have cytosols linked via gap junction so stimulation can cause a large portion of a vessel to constrict.
o Enlarged nerve axons synapse with smooth muscle cells in the tunica media. • Pulmonary Circulation:
o Blood is ejected from the right ventricle into the pulmonary trunk.
o Pulmonary trunk gives way into the right and left pulmonary arteries, which take the blood to the right and left lungs.
o The blood then passes to capillaries that encircle alveoli (terminal sacs at the end of the bronchioles, the smallest ling air passageways).
o In here oxygen diffuses into the blood and carbon dioxide difuses out.
o From the capillaries the blood moves to venules, small veins, medium veins, large veins called theright and left pulmonary veins that direct the blood to the left atrium so it can be passed to the left ventricle and then the systemic circulation.
• Systemic Circulation:
o Recieves oxygen-‐rich blood in the aorta as it is pumped in the left ventricle.
o Distributes it through the body directing it through; large elastic artery branchings of the aorta, muscular arteries, arterioles, and capillaries. Through this path oxygen diffuses from higher concentration in the blood plasma to lower concentration in the interstitial fluid, then to lower concentration as it diffuses into the cells and then the mitochondria.
o Carbon Dioxide diffuses form the cells towards the interstitial fluid and then towards the capillaries, venules, small veins, medium veins, and large veins.
o The superior and inferior vena cava return the blood to the right atrium from where ir re-‐enters the pulmonary circulation.
• Systemic Arteries:
Ascending aorta: 2 inches long.
• The right and left coronary arteries, which supply the heart with fresh, oxygen-‐rich blood, branch from this part of the aorta.
Aortic arch: posteriorly directed arch to the left.
• Branchicephalic: branches at the level of the clavicle to form the right common carotid artery, which directs blood to the right side of the head and neck.
• Common carotid artery:
o Left common carotid artery: transports blood to the left side of the head and neck.
o Right common carotid artery • Subclavian artery:
o Left subclavian artery: transports blood to the left upper limb. Descending aorta:
• Longest portion, extends through the torax, abdomen and above the pelvis.
• Thoracic Aorta: occurs within the torax.
o Left and right bronchial arteries supply the left and right lungs. o Esophageal arteries supply the esophagus.
o Posterior intercostals supply the thoracic walls
• Abdominal Aorta: between diaphragm and part of the descending aorta that gives way to the two common iliac arteries.
o Common Iliac arteries:
External iliac supplies the lower limb
Internal iliac supplies the hip, pelvis, lower back, urinary bladder, vagina, uterus, rectum, and external genitalia. • Systemic Veins:
o Superior Vena Cava: returns systemic blood from the head, thorax, neck, and upper limbs
o Inferior Vena Cava: returns blood from the abdomen, pelvis, and lower limbs. o Coronary sinus: returns blood from the heart walls.
Cardiac Veins: drain blood from the heart walls to the coronary sinus. o Major veins that return blood to the superior and inferior vena cava:
Right and Left Brachiocephalic veins: receive blood from the internal and external jugular veins
• External Jugular Vein: from head and neck region to the left brachiocephalic vein
• Internal Jugular: from cranium, anterior head, face and neck to subclavian veins.
o The joining of these to the left and right subclavian veins from the brachiocephalic veins.
• Right and Left subclavian veins: from upper extremities to brachiocephalic vein.
• Internal Thoracic veins: receive blood by anterior intercostal veins and drain to brachiocephalic veins
o Anterior intercostal veins: from anterior thoracic wall to internal thoracic veins
Renal Vein: from kidney to inferior vena cava
External and Internal Iliac veins: from lower limbs, join to form common iliac veins, which drain to the inferior vena cava.
Femoral veins: from lower limbs to external iliac veins. • Vessels of the Lymphatic System:
o Lymphatic System: drains the interstitial fluid away from the tissues of the body. o Lymph: interstitial fluid inside the lymph vessels
o The simple squamous endothelial cells of the lymph capillaries have a looser
association with one another making them especially permeable to the interstitial fluid (it does not easily flow back out because they work like valves).
o Lymph vessels are lacking in CNS, tissues that lack blood vessels and bone marrow. o Interstitial fluid forms via bulk flow from a greater pressure inside the capillaries and
towards a lower pressure outside.
o Lymph capillaries unite to form larger lymph vessels that contain: endothelial cells forming the inner layer, elastic membrane surrounding the endothelial cells, a middle layer consisting of smooth muscle surrounded by elastic fibers, and thin fibrous connective tissue comprising the outermost layer. Smaller vessels have regularly spaced bulges due to the one-‐way valves.
o Mobility of lymph is thought to result from: contraction of the surrounding skeletal muscles, contraction of the smooth muscle making up the lymph vessel middle layer, thoracic pressure changes resulting from respiration.
o Lymph nodes occur intermittently along the lymphatic system vessels.
Function as filtering stations removing bacteria and other disease-‐causing agents; this is critical because the lymph returns to systemic circulation through the right or left subclavian vein and thus become plasma again.
o As lymph vessels progress towards the subclavian veins they unite and become larger. The vessels from the right limb and the right side of the head and neck direct
lymph to the right lymphatic duct (smaller than the thoracic duct). • If an individual has more than one the first one will drain into the
subclavia vein while the additional two drain into the right internal jugular vein and the brachiocephalic vein.
The thoracic duct receives lymph from all other areas of the body; thorax, abdomen, lower limbs, left upper extremity, and left side of the head and neck. o The thoracic duct enlarges to form the cisterna chili in the upper abdominal region;
this portion receives lymph from the abdomen and the lower limbs. • Lymphatic System Function
o Fluid balance in the body. o Absorbtion of ingested fat
Lymph vessels called lacteals received the absorbed products of lipid digestion from epithelial cells of small intestine.
o Defense by filtering microorganisms and other substances from the lymph. Lymph nodes receive lymph from an afferent lymph vessel filter it and the
lymph exits through an efferent lymph vessel.
Lymph nodes are especially abundant in the inguinal nodes of the groin area, auxiliary nodes in the armpit area, and cervical nodes in the neck region. o Lymph node:
Capsule: layer of dense connective tissue that surrounds the lymph node Trabeculae: delicate extensions of the capsules that establish an internal
skeleton within the lymph node.
Reticular fibers from a fibrous network beteen the trabeculae and the capsule. Theese make up the tissues of the lymph with lymphocytes and macrophages. Lymph sinuses are areas containing only reticulated fibers.
Outer region is called cortex and it is comprised of lymph tissues separated by more diffuse lymphatic tissues, trabeculae, and lymph sinuses.
The inner region is de medulla and it is made up of branched, diffuse lymphatic tissues called medullary cords.
The presence of microorganismso stimulates the proliferation of lymphocytes, these newly generated lymphocytes can leave the blood and travel to other lymphatic tissues.
o A fibrous capsule surrounds the spleen; trabeculae extend in from the inner portion of the spleen.
Red Pulp: associated with venous blood White Pulp: associated with arterial blood Functions:
• Formation and storage of RBC • Breakdown of old RBC
• Storage of half of the body’s monocytes (can become macrophages and enter lymph nodes)
• Contains only efferent lymphatic vessels making it possible to pass monocytes destined to become macrophages.
o Thymus gland is bilobed and located near the sternum, it grows until puberty, produces lymphocytes.
• Factors Affecting Blood Circulation:
o Pressure, flow, resistance, and mechanisms regulating blood flow affect Blood circulation.
o We can regard a linear portion of blood within a vessel as being made up of a series of cross-‐sectional, ring-‐shaped liquid layer from the wall of the vessel towards the center. o The layers nearest the wall experience grater resistance and move slower.
o Laminar flow: streamlined flow of a fluid through a tubular structure.
o Laminar flow is disrupted by constriction, an uneven surface, a sudden turn, or some such change in the character of the vessel and results in turbulence.
o Rate of blood flow is the volume of blood moving through a vessel segment per unit time (L/min).
o In order to blood flow there must be a difference in pressure between two points in a vessel, and it is countered by resistance to this flow.
o Pouiseuille’s Law: Q= ΔP r4 π/ ηL 8
Q: Blood Flow
ΔP: pressure difference between two points
L: length between the two points r: radius of the blood radius
π: 3.14
η: Liquid viscosity: fluid’s resistance to flow
o Blood viscosity is the result of it’s cellular component called hematocrit which makes it three times as viscous than water.
o Critical closing pressure: pressure at which a blood vessel collapses causing tissues to be deprived of blood and making them susceptible to be necrotic.
o Law of LaPlace: the force causing a vascular wall to stretch is proportional to both blood vessel diameter and blood pressure.
F = D x P
F: force required to move the blood D: diameter of blood vessels
P: blood pressure
o In areas of the blod vessel that have been weakened an aneurism can form, this is a bulge that results from pressure pushing on that wall area.
o Compliance: a vessel’s tendency to increase in volume in accordance with increased bp. C = ΔV/ VP
Blood vessels with high compliance stretch in response to little pressure increase, the ones that exhibit low compliance stretch little in response to pressure increases.
o Veins have a higher level of compliance than arteries and are used as blood storage areas, more blood is found in veins.
o There is a direct relationship between arterial pressure decreases in the systemic circulation and resistance to blood flow, the further from the aorta the greater the resistance to flow.
o Pulse Pressure: difference between systolic and diastolic pressures, heart stroke volume (directly related) and vascular compliance (inversely related) factor into pulse pressure.
o Capillaries deliver nutrients and remove wastes. BP in the capillaries is more than in the surrounding interstitial fluid and thus fluid moves into the interstitial space via bulk flow and fluid is moved into the capillaries via osmosis.
o The plasma is much higher in dissolved proteins tha canoot exit the capillaries and so the blood osmotic pressure moves water and smaller solubilized substances from the interstitium into the capillary. There is a net loss of capillary fluid and a net gain of interstitial fluid.
o Because of pressure difference (higher at capillary arteriole junction) more interstitial fluid entering the capillary via osmosis near the capillary-‐venule end.
o Gravity increases BP when standing causing more fluid to leave the vessel. • Regulation of Blood Flow in Tissues:
o Can be controlled by: nervous system
mechanisms within close proximity to those tissues receiving blood both of the above
o How these factor affect depend upon the metabolic state of the body.
o Blood flow to the skin can function to cool the body through heat dissipation. o Various stimuli cause changes in blood flow to tissues. (Table XIII.1 p421) o Hormonal regulation result from increased epinephrine and lesser amounts of
norepinephrine from the adrenal medulla. • Blood, a Fluid form of connective tissue
o Formed element: cellular blood component 45% of the blood 95% erythrocytes (25% of the total cells of the body)
• biconcave disk shape provides a higher surface area to low volume ratio that facilitates rapid diffusion.
• 7.5 µm in diameter • lack a nucleus
• filled with hemoglobin
• transport oxygen and carbon dioxide • cannot reproduce
5% leukocytes
• Spherical Shape
• nucleus but lack hemoglobin • five different forms
o Granulocytes: cytolasms contain granule like structures Neutrophils
• nucleus made up of four lobes joined to one another via thin filaments
• Phagocytize
• 10-‐12 µm diameter
• Granules stain pink to redish-‐purple when stained with a neutral agent
Basophils
• Nucleus made up of two lobes that are not clearly distinguished.
• Puerple stained granules with basic agent. • 10-‐12 µm diameter
Eosinophils
• nucleus made up of two lobes
• Granules stained orange to bright red • 11-‐14 µm diameter
• Inflammatory response, attacks certain parasitic annelids
o Agranulocytes Lymphocytes
• Spherical nucleus
• Establishes a thin preiperal margin about the nucleus 6-‐14 µm
• Releases antibodies that kills invasive agents, important component of allergic reactions, controls the immune system
Monocytes
• Nucleus: spherical, kidney-‐like, horseshoe-‐like • Cytoplasm makes up a greater amount.
• 12-‐20 µm diameter • phagocytizes o Platelets:
Portions of cells enclosed in a membrane. Contain granules.
2-‐4 µm diameter
cause blood to clot and release chemicals that modulate the clotting of blood
o Plasma: liquid matrix 55% of the blood
Made up of 91% water and 9% non-‐water substances.
Colloidal solution: made up of suspended material that does not settle out of solution.
Composed of: • Proteins:
o Albumin: maintains blood viscosity and osmotic pressure, regulates pH functions as a buffer.
o Globulin: movement of various nutrients, ions, and hormones; also functions as components of the immune system
o Fibrinogen: clotting properties
• Ions: form membrane potentials, generate action potentials, maintenance of blood pH.
• Nutrients: glucose, amino acids, cholesterol, triacylglicerol, and vitamins
o promote metabolic activities • Wastes:
o H+, uric acid, NH3, NH4+, creatinine; removed through the
kidneys
o Bilirubin: degraded RBC, incorporated into bile and excreted from the body via the intestines.
o Lactic Acid: can be metabolized by the liver into glucose • Gases:
o Oxygen, Carbon Dioxide
o Nitrogen: majority of dissolved gas within plasma • Regulatory Components:
o hormones and enzymes o Physiological Roles played by blood:
Maintenance: pH, distribution of heat of metabolism, and prevention of blood loss through clotting properties.
• Nutrients (oxygen, simple sugars, lipids and amino acids)
• Wastes (carbon dioxide, broken down cells, macromolecules, smaller molecule ions)
• Hormones from endocrine tissue to target cell • Cells conferring immunological properties. Protection:
• WBC and other blood components eliminate invasive agents that could compromise the function of or destroy the body.
• Loss of blood is also prevented through clotting properties of blood. o Carbonic anhydrase: present in erythrocytes and catalyzes the conversion of water and
carbon dioxide into carbonic acid.
Blood carbon dioxide is transported in the form of carbon dioxide so that the concentration gradient makes carbon dioxide is moving towards the blood. o Each hemoglobin binds 4 oxygen molecules; 280,000 hemoglobin molecules make up
an erythrocyte.
When carbon dioxide is in high concentation it binds to heme groups.
o Erythropoietin: glycoprotein hormone produced by the kidney synthesized in response to low blood oxygen levels causing blood erythrocytes to increase.
