PBL Monday

what are the 2 main blood grouping systems?

- ABO

- Rhesus

what are the 4 different groups in the ABO grouping system?

- A

- B

- AB

- O

what are the 2 antigens of the ABO grouping system?

- A antigens

- B antigens

what antigens does type A have?

A antigens only

what antigens does type B have?

B antigens only

what antigens does type AB have?

A and B antigens

what antigens does type O have?

neither A or B antigens

what else contributes to the ABO grouping system?

antibodies:

- anti-A antibodies

- anti-B antibodies

what type of antibodies are anti-A and anti-B antibodies?

IgM

what antibodies does type A have?

anti-B antibodies

what antibodies does type B have?

anti-A antibodies

what antibodies does type AB have?

neither antibody

what antibodies does type O have?

both anti-A and anti-B antibodies

which blood type is the universal donor and why?

type O because it has no antigens on the surface that could interfere with other antibodies

which blood type is the universal receiver and why?

type AB because it does not contain any anti-A or anti-B antibodies that could interfere with antigens

how many different Rhesus (Rh) antigens are there?

5 clinically significant ones

what are the 5 clinically significant antigens?

- D

- C

- c

- E

- e

which is the main Rh antigen we focus on and why?

- Rh D

- because is it the most immunogenic, causes the greatest immune response

- most likely to cause a transfusion reaction

how do we determine whether someone is Rhesus positive or negative?

depends on whether they have Rh D antigen on surface of erythrocytes

when would someone be Rhesus positive?

if they have Rh D antigens

when would someone be Rhesus negative?

if they lack Rh D antigens

which blood can Rh+ people receive?

Rh+ and Rh-

which blood can Rh- people receive?

Rh- only

do all Rh- people have anti-D antibodies?

no, only when they have been exposed to Rh+ erythrocytes

when can the Rhesus grouping system cause problems in pregnancy?

if mother is Rh- and foetus is Rh+

what happens if foetus is Rh+ and mother is Rh-?

- presence of Rh D antigens stimulates production of anti-D antibodies

- maternal anti-D antibodies recognise and destroy foetal Rh D antigens - haemolysis

what is this called?

haemolytic disease of the new-born (HDN)

why is it not a large problem in nulliparous mothers?

the anti-D antibodies are mostly IgM which cannot cross the placenta

how do we prevent haemolytic disease of the new-born (HDN)?

administration of anti-D Ig prophylaxis

why is the Rhesus factor grouping system a large problem in multiparous mothers?

IgG anti-D anitbodies will be produced, which can cross the placenta

how does anti-D Ig prophylaxis work?

destroys feotal RBCs that leak into maternal circulation

what is the pericardium?

a fibro-serous, fluid-filled sac that surrounds the heart and roots of the great vessels

what are the 2 layers of the pericardium?

- fibrous layer

- serous layer

what is the fibrous pericardium?

- continuous with the central tendon of the diaphragm

- made up of tough connective tissue

what is the purpose of the fibrous pericardium?

it is non-distensible so prevents rapid overfilling of the heart

what 2 layers is the serous pericardium divided into?

- outer parietal layer

- internal visceral layer (epicardium)

what does the serous pericardium consist of?

single sheet of epithelial cells called the mesothelium

what lies between the outer parietal layer and internal visceral layer?

the pericardial cavity which contains some lubricating serous fluid

what is the purpose of the serous fluid?

minimises the friction generated by the heart as it contracts

what are all the layers from most outer to inner?

Fart Police Smell Villians:

Fibrous layer of pericardium

Parietal outer layer of serous pericardium

Serous fluid

Visceral inner layer of serous pericardium

give the 4 functions of the pericardium

- fixes the heart in the mediastinum

- prevents overfilling of the heart via the fibrous pericardium

- lubrication via the serous pericardium

- protection from infection as the fibrous pericardium acts as a physical barrier between heart and other organs

what nerve supplies the pericardium?

- phrenic nerve supplies the fibrous pericardium

- right and left vagus nerves supply serous pericardium

what arteries supply the pericardium?

- right and left internal thoracic arteries

- intercostal and superior phrenic arteries (inferior aspect)

- mediastinal branches of aorta (posterior aspect)

- epicardium by coronary arteries

what are the 5 surfaces of the heart?

anterior

posterior

inferior

right pulmonary

left pulmonary

what makes the anterior surface of heart?

right ventricle

what makes posterior surface of heart?

left atrium

what makes inferior surface of heart?

left and right ventricle

what makes right pulmonary surface?

right atrium

what makes the left pulmonary surface?

left ventricle

what are the 4 borders of the heart?

right border

left border

inferior border

superior border

what makes the right border?

right atrium

what makes the left border?

left ventricle (and some left atrium)

what makes inferior border?

left and right ventricles

what makes superior border?

right and left atrium and great vessels

what forms the sulci of the heart?

the four chamber divisions create grooves on the surface of the heart

what are the three sulci?

coronary sulcus

anterior interventricular sulcus

posterior interventricular sulcus

where is the coronary sulcus?

runs transversely where the atria divide form the ventricles

where are the anterior and posterior interventricular sulci?

they run vertically on anterior and posterior sides of heart, where the right and left ventricles separate

what are the pericardial sinuses?

passageways formed by the pericardium folds around the great vessels

what are the 2 pericardial sinuses?

oblique pericardial sinus - posterior surface

transverse pericardial sinus - superior surface

what is the definition of starlings law?

the ability of the heart to change its force of contraction and therefore stroke volume in response to changes in venous return

what happens to the stroke volume as the central venous pressure increases?

also increases

how does the stroke volume increase with venous pressure?

- the heart fills and stretches more

- this creates more regions of overlap for the actin-myosin cross-bridges to form

- allows for a greater force of contraction

is there a relationship between the force of a muscle fibre and the degree to which the muscle fibre is stretched?

yes - the more it is stretched the greater the force, until it reaches the optimal muscle fibre length

what happens if the preload is too high?

the optimal fibre length is surpassed which causes a decrease in contractility and stroke volume

what is on the x axis of the Starling curve?

left ventricular end diastolic pressure (LVEDP) in mmHg

what is on the y axis of the Starling curve?

stroke volume in μm

what happens to the curve in increased inotropy?

shifts up

what is inotropy?

force of contraction

what happens to the curve in decreased inotropy?

shifts downs

what effect does the sympathetic nervous system have on contractility?

positive inotropic effect

how does the sympathetic nervous system have a positive inotropic effect?

noradrenaline acts on B1 adrenoreceptors

what effect does the parasympathetic nervous system have on contractility?

negative inotropic effect

how does the parasympathetic nervous system have a negative inotropic effect?

acetylcholine acts on M2 muscarinic receptors

what can affect stroke volume? (3)

- preload

- contractility

- afterload

what is stroke volume?

difference between end diastolic and end systolic volumes

what increases the preload? (2)

- fast filling time

- increased venous return

what does an increased preload do to stroke volume?

increases end diastolic volume - so increases stroke volume

what decreases preload? (7)

- high or low sodium

- high or low potassium

- low body temperature

- drugs

- decreased calcium ions

- hypoxia

- decreased thyroid hormones

what increases contractility? (5)

- sympathetic stimulation

- epinepherine and norepinephrine

- increased calcium ions

- thyroid hormones

- glucagon

what does increasing contractility do to stroke volume?

decreases end systolic volume - so increases stroke volume

what decreases contractility? (4)

- parasympathetic stimulation

- acetylcholine

- hypoxia

- hyperalkaemia

what increases afterload? (3)

- hypertension

- vasoconstriction

- atherosclerosis

what does an increase in afterload to do the stroke volume?

increases end systolic volume - so decreases stroke volume

what decreases afterload?

vasodilation

what in the biggest unit that makes up a muscle?

fasicle

what makes up the fasicles?

muscle fibres aka muscle cells aka myocytes

what makes up the muscle fibres/cells/myocytes?

myofibrils

what makes up the myofibrils?

myofilaments

what are the myofilaments?

actin and myosin

which out of actin and myosin is thinner or thicker?

actin - thin

myosin - thick

what is the sarcolemma?

plasma membrane of a muscle fibre/cell/myocyte

what is the myofibril organised into?

sarcomeres - short segments of myofibril

where does the sarcomere span to and from?

Z line to Z line

what is the Z line made of?

actin

what is the centre of the sarcomere called?

M line

what makes up the M line?

myosin

what is the A band?

length of the myosin

what is the I band?

actin only area

what is the H band?

myosin only