BIOL204 EXAM 2 MATERIAL

LEC6-11

LEC 6: describe the general location, size, and shape of the heart

The heart is located in the middle mediastinum of the

thoracic cavity, within the pericardial cavity.

The heart is the size of a fist.

LEC 6: Identify the 4 chambers of the heart

left and right atria: thin upper chambers that receive blood returning to the heart through veins
left and right ventricles: thick, muscular lower chambers that pump blood out of the heart through arteries (away)

septa: muscular wall that divides the left and right side of the heart

functionally, the heart is a double pump

LEC 6: Identify the four heart valves, their structure, functions, and locations

Valves of the Heart – allow one-way flow of blood (respond passively to pressure gradients)

semilunar (SL) valves

function: prevent backflow into the ventricles when the ventricles are relaxing

1 heart valve: pulmonary valve

structure: honestly, like a round stomach with the beginning of big thighs (oval overall)

location: right ventricle - pulmonary artery

2 heart valve: aortic valve

structure: circle split equally into 3

location: left ventricle - aorta

atrioventricular (AV) valves

function: prevent backflow into the atria when the ventricles are contracting

3 heart valve: tricuspid valve

structure: honestly, gooch and thighs in a circle (3 cusps)

location: right AV valve

4 heart valve: mitral valve

structure: honestly, thick buns with a crack in the middle

location: bicuspid or left AV valve

4 valves are located within the cardiac skeleton (=fibrous skeleton) (connective tissue), stabilize their positions - prevents overdilation

LEC 6: Compare and contrast the structure of the atrioventricular and the semilunar valves

AV valves: chordae tendineae prevent them from being pushed up into the atria during ventricular systole (eversion)

SL valves: do not have tendons to resist prolapse, instead they are SL valves (cup shape) which fill with blood when closed (each has 3 half moon shaped cusps)

pulmonary valve: it has 3 flaps/cusps that open and close to control blood flow (gooch and thighs), mediates flow between the right ventricle and pulmonary artery

LEC 6: Describe the pericardium and its two layers

pericardium: sac-like structure wrapped around heart, made up of the outer fibrous pericardium and the inner serous pericardium (parietal and visceral layers)

fibrous pericardium: encloses the heart (like a bag)

pericardial cavity: contains pericardial fluid reducing friction

visceral layer of serous: coronary blood vessels travel through this layer

LEC 6: State the three layers of the heart wall

pericardium/epicardium - outer

myocardium - middle

endocardium - inner, continuous with endothelium in vessels

LEC 6: Analyze the structural characteristics of cardiomyocytes

short, thick, branched cells… mass of glycogen, theres intercalated discs striations, nucleus

almost totally dependent on aerobic metabolism (need oxygen) for energy

LEC 6: Analyze the role of intercalated discs connecting cardiomyocytes

specialized adhesive junctions - connect adjacent cardiac cells

specialized cell junctions - anchor cardiac muscle cells together

protein channels that connect the cytoplasm of neighboring cells allow electrical signals to pass directly from one cell to another, enabling rapid and synchronized contractions of the heart muscle - cells function together as single unit = functional syncytium

LEC 6: List the phases of the cardiac muscle action potential and explain the ion movements that occur in each phase

resting membrane potential

phase 0: rapid Na+ influx through open fast Na+ channels

phase 1: transient K+ channels open and K+ efflux begins to return the membrane potential to 0 mV

phase 2: influx of Ca2+ through channels balances the K+ efflux to create the plateau phase

phase 3: Ca2+ channels close and rectifier K+ channels remain open to return the membrane potential to -90 mV

phase 4: K+ rectifier channels maintain the negative resting potential (Na-K ATPase)

each phase results from a change in the balance of inward and outward ionic currents that become activated upon membrane depolarization

LEC 6: Explain the significance of the long absolute refractory period and the plateau phase in the action potential of a cardiac contractile cell

significance of long absolute refractory period: the interval of time during which a second action potential cannot be initiated → helps to prevent the heart from entering a state of rapid and disorganized contractions (fibrillation)

significance of plateau phase: unique for cardiac cells which allow enough calcium influx for a strong, sustained contraction to pump blood efficiently → this ensures that the ventricles have sufficient time to squeeze blood out efficiently with each beat

LEC 6: Describe in detail one complete cycle of heat contraction and relaxation (cardiac cycle)

cardiac cycle: the sequence of events that occur during one complete heartbeat

occurs in 2 phases:

contraction (systole) - blood leaves the chamber

relaxation (diastole) - blood refills chamber

pressure changes promote blood flow and valve opening and closing

-fluid will only flow if there is a pressure gradient (pressure difference)

-fluid flows from high-pressure to low-pressure joint

LEC 6: What is the cardiac cycle?

1) all chambers relaxed; AV valves open; ventricles fill passively to ~70%

2) atrial systole: atria contract together; finish filling ventricles

3) ventricular systole: first phase. contracting ventricles push AV valves closed but not enough pressure to open the SL valves

4) ventricular systole: second phase. increasing pressure opens SL valves; push blood into the pulmonary and systemic circuits; atria are relaxed (diastole) and filling

5) ventricular diastole: early. ventricles relax and their pressure drops; blood in aorta and pulmonary trunk backflows, closes SL valves

6) all valves closed; no volume change; blood passively filling atria

LEC 6: Explain the following concepts: end-diastolic volume, isovolumetric contraction, ventricular ejection, and isovolumetric relaxation

end-diastolic volume (EDV): the amount of blood in the ventricle at the end of diastole

isovolumetric contraction: the initial phase of ventricular contraction where the muscle fibers contract but the valves remain closed, resulting in no change in ventricular volume. it builds tension in the heart muscle, preparing it to eject blood

ventricular ejection: the phase of ventricular contraction where the aortic and pulmonary valves open, allowing blood to be ejected from the ventricles into the aorta and pulmonary artery (blood is pumped throughout body)

isovolumetric relaxation: the ventricles relax, but valves remain closed, resulting in no change in ventricular volume

LEC 6: Indicate what causes the sounds of the heartbeat

the closing valve cusps DO NOT make sound → the sound is made by TURBULENCE OF BLOOD HITTING a closed valve or RAPIDLY FILLING a chamber

when AV valves close; marks start of ventricular contraction = lubb (louder and longer)… when SL valve close = dupp (softer and sharper)… ventricular filling sound… inaudible (normal) audible (usually abnormal) = atrial gallop, occurs during active LV filling when atrial contraction forces blood into a noncompliant LV ← last 2 very faint

abnormal heart sounds, MURMURS, indicate problem with heart valves

valve problems cause valves to LEAK (regurgitation) or to NARROW (stenosis), which can lead to turbulent blood flow and create abnormal sounds

LEC 7: Identify the various cell types in the heart

smooth muscle cells: in the walls of blood vessels

endothelial cells: line the inner surface of heart and blood vessels

epicardium cells: cells that form the epicardium

fibroblasts: cells that produce and maintain the extracellular matrix (ECM). they are highly responsive to cardiac injury

cardiomyocytes: muscle cells, responsible for contracting and pumping blood

purkinje fibres: specialized muscle cells that form the Purkinje fibers, which rapidly conduct electrical impulses

pacemaker cells: they generate electrical impulses, spider- and spindle-shaped cells

LEC 7: Explain why the SA node normally paces the heart

auto-rhythmicity: cardiac muscle’s ability to contract at its own pace independent of neural or hormonal stimulation

conduction system consists of CONDUCTING CELLS which are nerve-like conduction pathways (made of modified cardiomyocytes) through the myocardium

PACEMAKER aka sinoatrial node (SA): sets the rate of the heartbeat (sinus rhythm), firing at 100 bpm, SA has fastest rate of spontaneous depolarization

LEC 7: List the parts of the electrical conduction system of the heart in the correct sequence for one contraction and explain how the electrical conduction system functions

1) PACEMAKER/SA: generates electrical impulse, spreads through the atria

2) BACHMANN BUNDLE/INTERATRIAL BUNDLE: helps spread the impulse to the left atrium

3) AV node: impulse reaches the AV node, which delays the impulse

4) bundle of His: delayed impulse travels through the bundle of His

5) Purkinje fibers: then through Purkinje fibers to the ventricles, causing them to contract

speed of depolarization AV > bundle of His > Purkinje fibers

LEC 7: Understand the differences between the two types of cardiac action potentials (muscle cells vs. pacemaker cells), including the role of the pacemaker potential in the SA node’s automaticity

the heart has 2 types of AP:

1) muscles of atria and ventricles where they got plateau, contractile cells

2) in the pacemaker of heart aka SA, conducting cells

phase 4: “pacemaker potential,” bc it is responsible for the spontaneous repetitive depolarization (automaticity)

certain NONcontractile cardiac muscle cells exhibit automaticity and rhythmicity and can independently initiate APs bc their resting mb potential (RMP) is unstable bc it never “rests” = pacemaker potential

automaticity is due to the fact that these cells start leaking Na+ into cell as soon as they return to resting state

LEC 7: Define electrocardiogram (ECG or EKG)

electro - electrical activity

cardio - heart

gram - written record

ECG recording = sum of all the electrical potentials generated by all the cells of the heart at any instance in time

creates tiny voltage changes that are picked up by electrodes

LEC 7: Name the waveforms in a normal ECG and relate the electrical events to the normal mechanical events of the cardiac cycle

P wave = corresponds to the atrial depolarization phase of the cardiac AP

PR segment - atrial systole

PR interval - signal conduction thru AV node before activating ventricles

QRS complex = indicates ventricular depolarization and some atrial repolarization

ST segment - ventricular systole

T wave = represents ventricular repolarization

DEPOLARIZATION BEFORE MECHANICAL CONTRACTION

LEC 7: Define HR, heart rhythm, heart beat, fibrillation

heart rate (HR): calculated from R wave to R wave. a normal resting HR is 60-100 bpm

heart rhythm: electrical activity that underlies the mechanical function of heart

heartbeat: physical contraction and relaxation of heart muscle, which pumps throughout the body. its the mechanical action of heart

arrhythmia: extra or missed beat or FIBRILLATION when atria/ventricles contracting in uncoordinated fashion

sinus tachycardia >100 bpm

sinus bradycardia <60 bpm

sinus arrythmia: unequal time btwn beats

LEC 7: Explain the regulation of heart rate by autonomic nervous system

sympathetic NS: positive chronotropic effect → inc HR via SA node; positive inotropic effect by increasing intracellular Ca2+; positive dromotropic effect → inc AV conduction velocity (via beta1 adrenergic receptors)

parasympathetic NS: vagus nerve directly innervates SA node and dec HR; inhibits AV node conduction velocity w/ little effect on myocardial contractility

LEC 8: Identify the major blood vessels entering and leaving the heart

aorta: largest artery, most elastic, leaves left ventricle-oxygenated blood

ascending aorta: right and left coronary arteries supply blood to the heart itself

aortic arch: brachiocephalic artery emerges

right subclavian artery supplies blood to right arms

left subclavian artery supplies blood to right arms

right and left common carotid artery supplies blood to the head

—

vena cavae: largest veins in body, return deoxygenated blood from body to right atrium of heart

superior vena cava: carries blood from head, neck, and chest

inferior vena cava: carries blood from legs and abdomen

—

right ventricle discharges blood into → pulmonary trunk - splits into left and right and both lead to lungs

pulmonary veins return blood from lungs to heart (connects to left atrium)

LEC 8: Trace the path of blood through the right and left sides of the heart, including its passage through the heart valves, and indicate whether the blood is oxygen-rich or oxygen poor

blood flow within heart is unidirectional

1-superior vena cava = oxygen poor

2-inferior vena cava = oxygen poor

3-right atrium = oxygen poor

4-tricuspid valve = oxygen poor

5-right ventricle = oxygen poor, thinner wall; sends blood to adj lungs (pulmonary circuit)

6-pulmonary valve = oxygen poor

7-pulmonary arteries = oxygen poor

8-pulmonary veins = oxygen rich

9-left atrium = oxygen rich

10-mitral valve = oxygen rich

11-left ventricle = oxygen rich, blood enters and leaves the ventricles at base → ventricles must contract from bottom (apex) up to expel blood from base

12-aortic valve = oxygen rich

13-aorta = oxygen rich

—

force propelling the blood: pressure gradient, created primarily by the contraction and relaxation of the heart muscle

p1 left ventricle → p2 aorta

LEC 8: Explain how the heart is a double pump and why this is significant

the heart consists of 2 separate pumps:

pulmonary circulation - pumps blood thru lungs, where blood picks up oxygen and dumps CO2, and then blood travels back

systemic circulation - pumps blood thru body’s tissues, supplying them w/ oxygen and nutrients and removing CO2

—

left side of heart has thicker muscular wall (must generate much force)

LEC 8: Define end diastolic volume (EDV) and end systolic volume (ESV), and calculate stroke volume (SV) given values for EDV and ESV

end diastolic volume (EDV): total volume of blood in ventricle right at the end of diastole, avg M 160ml, avg F 132ml

end systolic volume (ESV): remaining blood in the ventricle after contraction (systole), avg M 54ml, avg F 44ml

stroke volume (SV): volume of blood pumped out (ejected) of ventricle per contraction or beat (systole), avg 50-100 ml

SV = EDV-ESV

LEC 8: Describe the 3 primary factors that influence stroke volume (SV): preload, afterload, and contractility

preload: the degree of myocardial stretch at the end of diastole, directly proportional to EDV (described by Frank-Starling Law),

• affecting factors: venous return and rate of filling after diastolic phase

afterload: the pressure against which the ventricle must contract to eject blood

• affecting factors: systemic vascular resistance (SVR) and pulmonary vascular resistance (PVR)

  • vascular resistance: force that opposes flow of blood thru circulatory system

contractility: intrinsic strength of myocardial contraction (force with which ventricular ejection occurs)

• affecting factor: autonomic innervation

LEC 8: State the Frank-Starling Law of the heart

Frank-Starling Law: highlights intrinsic ability of the heart to adjust the force of its contraction in response to changes in ventricular filling (EDV)

1-when venous return inc, more blood fills heart during diastole

2-this inc volume stretches ventricular walls, lengthening sarcomeres

3-as sarcomeres approach optimal length, force of contraction inc → greater volume of blood ejected from heart during systole (SV)

LEC 8: Explain ejection fraction (EF)

ejection fraction (EF): the % of blood pumped out of the ventricles at every contraction- describes the efficiency of heart

EF normalizes SV for heart size by expressing it as % of EDV

avg EF is 50-70%

EF(%) = SV/EDV * 100

SV = EDV-ESV

—

heart failure (HF): heart’s inability to pump blood effectively to meet body needs

EF is used to classify HF into categories:

• HF with reduced ejection fraction (HFrEF) = impaired contractile function

• HF with preserved ejection fraction (HFpEF)

LEC 8: Define cardiac output (CO). Predict how heart rate (HR) and/or SV changes will affect CO

cardiac output (CO): volume of blood pumped out of the ventricles in ONE MINUTE

normal range: 5-6 L/min

SV: volume of blood pumped out of left ventricle in single heartbeat

normal range: 50-100 mL

CO = SV * HR

LEC 9: Define the terms artery, capillary, and vein

artery: strong elastic vessels which carry blood moving away from the heart, artery regulates blood flow to an organ

• smallest ones: arterioles - connect to capillaries, arterioles regulate blood within organs

capillary: allow exchange of materials (oxygen nutrients) between blood and tissues

vein: thinner, less muscular vessels carrying blood toward the heart

• capacitance vessels (hold high volume blood)

• thin-walled and flaccid

• collapse when empty, expand easily

• have steady blood flow (unlike pulses in arteries)

• small veins merge to form larger and larger one as they approach heart

  • types of veins: postcapillary venules, muscular venules, medium veins, large veins

LEC 9: List the three tunics associated with most blood vessels and describe the composition of each tunic

outermost-

tunica externa → adventitia

tunica media → [external elastic lamella (veins absent) > thick smooth muscle]

tunica intima → [internal elastic lamella (veins thin/absent) > basement membrane > endothelium]

→ lumen

innermost-

LEC 9: Indicate the function of specific types of arteries and arterioles

types of arteries

near the heart: aorta and its primary branches:

conducting (elastic or large) arteries: conduct blood away from heart, inc elastin: expand during systole and recoil during diastole which lessens fluctuations in BP

distributing (muscular or medium) arteries: distribute blood to body organs and tissues, thickest tunica media of all blood vessels

resistance (small) arteries: resistance vessels offer greatest resistance to blood flow due to small diameter, control amount of blood to various organs

• smallest resistance arteries are the arterioles which lead directly into capillary beds, regulate flow by Vd/Vc

types of arterioles

metarioles: link arterioles to capillaries, muscle cells form precapillary sphincter about entrance to capillary

LEC 9: Define capillary bed and its components

capillary bed: organized network of 10 to 100 capillaries that are supplied by single metarteriole

components:

arteriole on artery side…capillary bed... venules on vein side
capillary bed is site of exchange between blood and surrounding tissues

LEC 9: Explain the role of precapillary sphincter in autoregulation

precapillary sphincters: control blood flow into individual capillaries

when sphincters RELAXED/OPEN: blood flows through capillaries

when sphincters CONTRACTED/CLOSED: blood flows through thoroughfare channel, bypassing capillaries

LEC 9: Describe the forces that create capillary filtration and reabsorption (Starling Forces)

Starling Forces → 4 forces

1. capillary hydrostatic pressure (Pc) → pushes fluid OUT of capillary → filtration

2. interstitial fluid pressure (Pi) → pushes fluid INTO capillary → reabsorption

3. capillary oncotic pressure (πc) → proteins pull water INTO capillary → reabsorption

4. interstitial oncotic pressure (πi) → proteins pull water OUT of capillary → filtration

net filtration pressure (NFP) = (Pc + πi) - (Pi + πc)

positive NFP → filtration

negative NFP → reabsorption

LEC 9: List types of capillaries, state where in the body each type is located, and correlate their anatomical structure with their functions

1. continuous capillaries

• structure: tight junctions, small intercellular clefts

• location: most tissues and organs

• function: allows small molecules only

2. fenestrated capillaries

• structure: fenestrations/pores in endothelial cells

• location: kidneys, small intestine, choroid plexus

• function: rapid absorption and filtration **HINT like holes on sports bra

3. sinusoidal capillaries

• structure: large gaps, incomplete basement membrane

• location: liver, bone marrow, spleen

• function: allow proteins and blood cells pass

LEC 9: Indicate the factors aiding venous return

venous return = volume of blood flow returning to heart from veins

1. pressure gradient (veins → heart) - blood flow HIGH PRESSURE vein to LOW PRESSURE heart, venous blood TO heart

2. thoracic (respiratory) pump - inhalation: diaphragm contract and move down, chest pressure NEGATIVE, vacuum effect pull blood TOWARD heart

3. venous valves and muscle pump - veins have one-way valves → prevent backflow

LEC 9: Indicate variations in the circulatory pathways

1. simplest circulation pathway

• heart → arteries → arterioles → capillaries → venules → veins → heart

2. portal system

• blood flows thru 2 capillary beds in a row before returning to heart (hepatic portal system, hypothalamus-pituitary portal system)

3. anastomosis

• connection where two blood vessels merge

  • arteriovenous anastomosis (shunt) → bypass capillaries

  • arterial anastomoses → artery to artery connection

  • venous anastomoses → vein to vein connection

fetal circulation: deliver most oxygenated blood quickly to brain and heart

oxygenated blood come from placenta → umbilical vein

3 fetal shunts

1. ductus venosus → bypass liver

2. foramen ovale → RA to LA

3. ductus arteriosus → pulmonary artery to aorta

LEC 9: Define blood flow, blood pressure, and peripheral resistance

blood flow: volume of blood moving thru vessels, an organ, or whole body per unit time, mL/min, total blood flow = CO at rest (5-25 L/min)

perfusion: blood flow per unit mass or volume of tissue, mL/min/g

blood pressure: force blood exerts on vessel walls, systolic/diastolic pressure

peripheral resistance (SVR/TPR): resistance to blood flow created by blood vessels

BP = Blood Flow * Resistance

LEC 9: State and interpret the equation that relates fluid flow to pressure and resistance

equation: Q = ΔP/R

Q = blood flow

ΔP = pressure gradient (P1-P2), greater ΔP greater blood flow

R = vascular resistance, friction

flow inc when pressure difference inc

flow dec when resistance inc

LEC 9: Analyze 3 factors that affect vascular resistance (R)

Poiseuille’s Law:

• R = 8ηl/πr⁴

  • η = viscosity, l = vessel length, r = vessel radius

1. blood viscosity

• determined mainly by hematocrit (RBC volume)

• higher viscosity → greater resistance

2. vessel length

• longer vessel → greater resistance

3. vessel radius (MOST IMPORTANT)

• resistance ∝ 1/r⁴

• small dec in radius → large inc in resistance

LEC 9: Indicate the intrinsic (local) and extrinsic (humoral, neural) factors that affect peripheral resistance and blood flow to tissues

1. intrinsic (local) - autoregulation

• factors within tissue or vessel that regulate local blood flow

  • myogenic response: vessel constrict/dilate due to changes in wall tension

  • metabolic control: low perfusion → waste products accumulate → vasodilation → inc blood flow

2. extrinsic

• neural

  • control vascular tone and bp

  • a-adrenergic → vasoconstriction

  • b-adrenergic → vasodilation

• humoral (blood borne)

  • vasoconstrictors: angiotensin ii, catecholamines, thromboxane, leukotrienes, endothelin

  • vasodilators: prostaglandins, kinins, nitric oxide

—trigger

peripheral resistance controlled by:

intrinsic: myogenic + metabolic autoreg

extrinsic:

neural: alpha constrict, beta dilate

humoral: hormones/chemicals constrict/dilate vessels

LEC 10: Using a graph of pressures within the systemic circuit, interpret the changes that occur in the arteries, capillaries, and veins

aora/arteries: have the highest pressure (~120mmHg), pressure is pulsatile due to heart contractions

arterioles: largest drop in pressure, major resistance vessels

capillaries: low pressure (~10-30mmHg), prevents damage to thin capillary walls, allow diffusion of gases and nutrients

veins: very low pressure, blood moves back to heart slowly

vena cava: lowest pressure (~0mmHg)

LEC 10: Given values for systolic and diastolic BP, calculate pulse pressure (PP) and mean arterial pressure (MAP)

pulse pressure (PP) = systolic BP (SP) - diastolic BP (DP)

• SP: peak pressure during ventricular contraction

• DP: lowest pressure during ventricular relaxation

mean arterial pressure (MAP) = DP + (1/3)(SP-DP)

• MAP always closer to DP

• represents average pressure in arteries during one cardiac cycle

• MAP important bc it indicates pressure that perfuses organs

LEC 10: State the relationship between MAP, CO, and Total Peripheral Resistance (TPR)

MAP = CO * TPR

whenever CO dec, TPR inc to maintain MAP

LEC 10: State the arterial sensory receptors and their functions

BARORECEPTOR (baroreflex)

location: carotid sinus, aortic arch

function: stretch receptors that detect BP, send signals to brainstem to regulate BP

CHEMORECEPTOR (chemoreflex)

location: carotid bodies, aortic bodies

function: detect changes in O2, CO2, and pH, send signals to brainstem respiratory centers, adjust respiration and vascular tone

LEC 10: Explain the steps of the baroreceptor reflex and describe how this reflex maintains BP homeostasis when BP changes

rapid, short-term regulation of BP via negative feedback

steps when BP increases:

1. INC of BP stretches arteries

• baroreceptors in carotid sinus + aortic arch detect stretch

• fire more AP

2. signals sent to cardiovascular center

• medulla oblongata (nucleus tractus solitarius - NTS)

3. sympathetic activity DEC

• DEC vasoconstriction

• DEC heart activity

4. parasympathetic (vagal) activity INC

• DEC heart rate

• DEC contractility

BP dec back toward normal

LEC 10: State the functions of the blood

1. transport

• delivers O2, nutrients, hormones

• removes CO2 and metabolic wastes (urea)

2. regulation

• maintains pH balance

• maintains fluid balance

• thermoregulation (heat distribution)

3. protection

• immune defense (WBCs and antibodies)

• hemostasis (stop bleeding)

LEC 10: Describe the overall composition of plasma, including the major types of plasma proteins and cells

blood composition: 55% plasma and 45% formed elements, adult 5L

plasma composition: 90% water, 7% proteins, 1-2% other solutes like electrolytes, nutrients, hormones, wastes

major plasma proteins: most synthesized in liver

• albumin (60%) → maintains osmotic pressure

• globulins (35%) → transport and immune functions

  • alpha: transport lipids, metals, hormones

  • beta: lipid transport (ex. LDL)

  • gamma: immunoglobulins (antibodies), produced by immune cells

• fibrinogen (4%) → blood clotting/coagulation

• other <1%: hormone transport proteins: SHBG, CBG, TBG

formed elements (3 types)

1. erythrocytes (RBCs)

• 45% of blood

• transport oxygen

2. leukocytes (WBCs)

• immune defense

• types: neutrophils, lymphocytes, monocytes, eosinophils, basophils

3. platelets

• blood clotting

all arise from hematopoietic stem cells in red bone marrow

LEC 10: Indicate the morphological features of erythrocytes and their main function

morphological features:

• biconcave disc shape

• flexible membrane

• no nucleus

• no organelles

shape purpose: allow RBCs to squeeze thru narrow capillaries

main function:

• transport O2 from lungs → tissues… CARRY

• transport CO2 from tissues → lungs… REMOVE

LEC 10: Discuss the structure of hemoglobin

globular metalloprotein

quaternary structure (4 subunits)

• 2 alpha chains

• 2 beta chains

heme group

• each subunit contains heme group

• heme contains Fe2+ (ferrous ion) inside porphyrin ring

oxygen binding

• each Fe2+ binds 1 O2 molecule

• 1 hemoglobin can carry 4 O2 molecules

fetal hemoglobin

• beta chains replaced by gamma chain

LEC 10: Discuss the breakdown products of hemoglobin

Hemoglobin → globin + heme

globin → amino acids

iron → reused

porphyrin → bilirubin → bile → stercobilin (feces)

LEC 10: State the significance of the hematopoietic stem cell (HSC or hemocytoblast)

hematopoietic stem cells (HSCs)

• multipotent stem cells in bone marrow

• produce all blood cells types

2 main lineages

1. myeloid → RBCs, platelets, most WBCs

2. lymphoid → lymphocytes

LEC 10: Explain the basic process of erythropoiesis and define hematocrit

erythropoiesis: production of RBCs in red bone marrow

stimulated by: erythropoietin (EPO)

requires: iron, vitamin B12, folic acid, globin protein

stages of RBC development

proerythroblast → erythroblast stages → nucleus ejected → reticulocyte → mature erythrocyte (RBC)

hemoglobin synthesis INC during maturation

hematocrit (HCT/Ht): percentage of blood volume made up of RBCs

LEC 10: Describe the process of leukopoiesis and its key regulatory factors (CSFs and ILs)

Leukopoiesis = WBC formation in bone marrow

lineages:

myeloid → granulocytes + monocytes

lymphoid → T cells, B cells, NK cells

regulated by: colony-stimulating factors CSFs (G-CSF, GM-CSF, M-CSF), interleukins (IL-7, 15)

CSF myeloid lineage

IL/lymphocyte by cytokines

LEC 10: Indicate the types of leukocytes and their main functions. Classify each type as granulocyte or agranulocyte

1. granulocytes (granular cytoplasm)

• neutrophils → phagocytosis

• eosinophils → parasites

• basophils → histamine

2. agranulocytes (no visible granules)

• monocytes → macrophages

• lymphocytes → T cells and B cells

• NK cells → kill infected/cancer cells

innate immune system - first line of defense, recognize PAMPs using PRRs

adaptive immune system - highly specific, TCRs and BCRs → immunological memory

LEC 10: Describe platelets (thrombocytes), including their origin (how they form)

platelets (thrombocytes): small anucleate/no nucleus cell fragments, derived from megakaryocytes in bone marrow

formation

hematopoietic stem cell → myeloid progenitor → megakaryoblast → megakaryocyte → platelets

regulated by THROMBOPOIETIN (TPO) from liver + kidneys

main role: essential for hemostasis (clotting)

LEC 10: Describe the functions of platelets and identify and explain three main types of secretory organelles they contain

platelet function

• hemostasis

• thrombosis

• platelet adhesion, activation, and clot formation

3 types of platelet granules

1. alpha-granules (most abundant) → clotting proteins (eg. vWF)

2. delta-granules (dense bodies) → activation (eg. ADP, ATP, Ca2+, serotonin)

3. lysosomes → proteolytic enzymes

LEC 11: Describe the role of platelets in hemostasis and the steps involved in the formation of the platelet plug

hemostasis: process that stops bleeding after blood vessel injury

steps of hemostasis

1. vascular spasm → vasoconstriction reduces blood flow and loss

2. primary hemostasis (platelet plug formation) (adhesion → activation → aggregation)

• adhesion → platelets bind to exposed collagen, vWF help

• activation → inc intracellular Ca2+, ADP and TXA2

• aggregation → GP Ilb/Ila receptors bind fibrinogen, cross link

3. secondary hemostasis (coagulation cascade)

• prothrombin → thrombin

• fibrinogen → fibrin

• fibrin mesh stabilizes platelet plug

requires Ca and K

LEC 11: Differentiate among the intrinsic, extrinsic, and common pathways of the coagulation cascade

coagulation cascade purpose: stabilize platelet plug w/ fibrin, clotting factors mostly produced in liver, serine proteases most factors

intrinsic pathway (contact pathway)

• trigger: blood contacts exposed collagen/vessel damage

• factors involved: 12 → 11 → 9 → 8 → 10, leads to activation of factor x

INTRINSIC = 12 11 9 8 10, FACTOR X

extrinsic pathway (tissue injury pathway)

• trigger: tissue factor (factor III) released from damaged tissue

• factors involved: 7 → 10

EXTRINSIC = 7 10

common path way (final clot formation)

factor x → Xa → prothrombin (ii) → thrombin (ila) → fibrinogen → fibrin → factor xiii cross link fibrin → stable clot

Ca (factor IV) → required for clotting rxn

K → needed to synthesize functional clotting factors

factor V → cofactor in prothrombinase complex

platelet granule molecules (help clot)

delta: ADP activate platelets, Ca2+ required for coagulation

alpha: vWF platelet adhesion to collagen, fibrinogen platelet aggregation, factor V clotting

LEC 11: Explain clot retraction

clot retraction: platelets contract and pull fibrin threads tgt, tighten clot

results: clot become stronger and smaller, serum squeezed out, edges of damaged vessel pulled tgt, blood flow partially restored

purpose: stabilize clot and help repair blood vessel

LEC 11: Discuss the process of fibrinolysis, including roles of plasminogen, tissue plasminogen activator, and plasmin

fibrinolysis: process that breaks down clot after healing begins

process of fibrinolysis:

endothelial cells release tPA (tissue plasminogen activator) → tPA converts plasminogen → plasmin → plasmin break down fibrin in clot → clot dissolves and normal blood flow returns

regulation: PAI-1 inhibit tPA, alpha2-antiplasmin inhibit plasmin preventing excessive clot breakdown

LEC 11: Explain the role of surface antigens on RBCs in determining blood groups

blood group determined by antigens on the surface of RBCs

2 main systems: ABO and Rh

if you lack antigen → you naturally have antibodies against it bc immune system is tolerant to self-antigens

A and B alleles are dominant, O allele is recessive

All RBCs have base structure H antigen. ABO gene make enzyme transferase that modifies H antigen

blood type → antigen on RBC → antibodies in plasma

A → A antigen → anti B

B → B antigen → anti A

AB → A and B antigens → none

O → none → anti A and anti B

Rh blood group: determined by Rh (D) antigen

LEC 11: Describe how the presence or absence of Rh antigen results in blood being classified as positive or negative

Rh blood type is determined by presence/absence of Rh (D) antigen on RBCs

type → meaning

Rh+ → RBCs have RhD protein antigen

Rh- → RBCs lack RhD protein antigen

LEC 11: Predict which blood types are compatible

you cannot receive RBCs with antigens your antibodies attack

universal donor: O-

universal recipient: AB+

ABO compatibility

blood type → can receive from

O → O

A → A, O

B → B, O

AB → A, B, AB, O

Rh rule: Rh+ can receive +/-, Rh- can only receive -

LEC 11: State the consequences of transfusing the incorrect ABO blood type

what happens: recipient antibodies bind donor RBC antigens, agglutination (RBC clump), hemolysis (RBC destruction)

consequences: clot block blood vessels, released hemoglobin damages kidneys, lead to kidney failure and severe transfusion rxn

LEC 11: Describe the development and clinical significance of anti-Rh antibodies

occurs when Rh- mom carries Rh+ fetus

first pregnancy: fetal Rh+ RBCs enter mom blood (usually during delivery), mother immune system recognize Rh antigen as foreign

maternal sensitization: mother product anti-Rh (anti-D) antibodies

subsequent Rh+ pregnancy: maternal anti-Rh IgG antibodies cross placenta

effect on fetus: antibodies destroy fetal RBCs → hemolytic disease of newborn (HDN)