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FunMed PBL > PBL 2 > Flashcards

PBL 2 Flashcards

1
Q

Non consanguineous

A

These are two individuals that are not related, they are further apart in terms of relation than second cousins.

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2
Q

Hepatosplenomegaly

A

disorder where both the liver and spleen swell beyond their normal size

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3
Q

Crackles

A

lung sounds that can be heard in

patients with pneumonia

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4
Q

Sonorous wheeze

A

low-pitched, course, loud,
low snoring or moaning sound, due to narrowing
of the large airways or an obstruction of the
bronchus

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5
Q

ESR - erythrocyte sediment rate

A

the rate at which RBCs sediment (settles
to the bottom of liquid) in a period of one hour;
elevated levels occur with inflammation,
anaemia, infection, etc.

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6
Q

Bilateral haziness

A

diffuse haziness that would

typically be called by inflammation, or thickening of tissues

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7
Q

Dactylitis

A

inflammation
of an entire digit, caused
by blocked blood
circulation

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8
Q

Hb electrophoresis

A

test to detect different types of haemoglobin

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9
Q

Nucleated RBCs

A

very immature forms of RBCs,
seen when there is a severe demand for RBCs to
be released by the bone marrow

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10
Q

Acute splenic sequestration crisis

A

refers to an

acute condition of intrasplenic pooling of large amounts of blood

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11
Q

Cefotaxime

A

antibiotic

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12
Q

Erythromycin

A

antibiotic

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13
Q

Peripheral blood smear

A

thin layer of blood

smeared on a glass microscope slide, and then stained in order to allow the blood cells to be examined via microscope

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14
Q

what is sickle cell anaemia

A

it is an autosomal recessive condition that affect the oxygen carrying capacity of haemoglobin molecules

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15
Q

what does autosomal recessive conditions mean that you need

A

Need two copies of the mutated gene n order to get sickle cel anaemia HbSS

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16
Q

what happens when you get one copy of the gene

A
  • this means that you have a sickle cell trait which is HbAS
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17
Q

what is the mutation for sickle cell anaemia

A
  • non conversed missense
  • occurs in one of amino acid which encodes the beta globin chain on chromosome 11 at position 6
  • converts glutamic acid to valine (thymine to adenine) in RNA A to U
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18
Q

what is haemoglobin A made out of

A

2 alpha, 2 beta chains
(dominates after 6
weeks of age)

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19
Q

what is haemoglobin S made out of

A

2 alpha, 2 mutant beta

chains

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20
Q

what is haemoglobin A2 made out of

A

2 alpha, 2 delta chains

21
Q

what is haemoglobin F made out of

A

2 alpha, 2 gamma chains
(dominates up to 6
weeks of age)

22
Q

what is haemoglobin F made out of

A

2 alpha, 2 gamma chains
(dominates up to 6
weeks of age)

23
Q

Describe how to do a solubility test for the diagnosis of an SCA

A
  • Is able to diagnose if there is HbS present
  • It is a very cheap and paper based screening test
  • It has 100% sensitivity to the presence of HbS
  • It has 100% specificity to HbS
  • You add 20μl blood to a solubility buffer (2.49 M
    phosphate buffer)
  • You then add saponin and a reducing agent (sodium
    hydrosulphite)
  • HbA and HbS are both identified in this test
24
Q

How do you use blood smears for the diagnosis of sickle cell anaemia

A

Most peripheral smears will not show abnormal
haemoglobin

This is because HbS will only cause sickling in
hypoxaemia

In hypoxaemia, the HbS form long polymer fibres,
and the cells sickle

To induce hypoxaemia, 2% sodium metabisulphite
(antioxidant) is added to the blood sample

25
Q

How do you treat sickle cell anaemia

A

Bone marrow transplant can potentially cure children

Hydroxyurea → drug which increases HbF production
→ this helps to reduce the symptoms and
complication of SCD

Antibiotics → reduce risk of infection

Pain relief → reduce pain levels

Blood transfusion → transfuse non-sickled blood into a
patient

Oxygen → increase O2 concentration in the blood

In the future? Possibly mutant ß-globin chain
switching → epigenetics

26
Q

what is the selective advantage of sickle cell trait

A

Being a sickle cell carrier gives an individual a
protective advantage over non-carriers in malaria

This might be why sickle cell is still present in
malaria endemic regions

RBCs infected with malaria have lower O2 levels

This makes them sickle, and allows the RBCs to
degrade

As a result, the parasite dies

27
Q

what is the mechanism for sickle cell trait protecting against malaria

A

P. Falciform infects an HbAS RBC

This requires higher oxygen consumption, and
decreases partial pressure of oxygen

This leads to sickling of RBCs and then subsequent
removal of the cells

Thus, the parasite is killed

28
Q

What are the examples of other autosomal recessive disorders

A
  • haemoglobin S - sickle cell anaemia
    CFTR - resistance to tuberculosis - cystic fibrosis
    HEXA - tay sachs
    HBA1/HBA2 thalassemia
29
Q

what is the difference between glutamic acid and valine

A

Glutamic acid

  • charged
  • polar
  • tucks into haemoglobin

valine

  • hydrophobic
  • non polar
  • sticks out of haemoglobin
30
Q

describe sickle cell crisis

A

Describes several independent acute conditions
that occur in patients with SCD

Most of these crises last between 5-7 days

Infection, dehydration, and acidosis are all triggers
as they favour sickling

However, most of the time, there is no definitive
predisposing cause

31
Q

what can cause a sickle cell crisis

A

Infection, dehydration, and acidosis are all triggers

as they favour sickling

32
Q

how do you treat a vast-occlusive crisis

A

Treated with hydration, analgesics, and blood

transfusion

33
Q

what is a Vasco-occlusive crisis caused by

A

Caused by sickled RBCs obstructing capillaries and
restricting blood flow to an organ

  • Dactylitis → due to recurrent ischaemic necrosis of the
    small bones in the hands and feet
  • Swelling persists for 1-2 weeks even after pain is
    resolved
  • Infarction of abdominal and retroperitoneal organs
  • Initially spleen enlarges
  • Then undergoes auto-splenectomy
  • Can lead to hepatic (liver) infarct
34
Q

what is a splenic sequestration crisis

A
  • this is an acute, painful enlargement of the spleen
35
Q

what is a splenic sequestration crisis resulting in

A

Results in Hb levels falling, and a potential for
hypovolaemic shock

Because the spleen has narrow vessels, and is
responsible for clearing defective RBCs, the spleen is
commonly affected in SCD

36
Q

What causes a splenic sequestration crisis

A
  • caused by intrasplenic trapping of red blood cells
37
Q

what is the damage of the splenic sequestration crisis

A
  • Damage in spleen leads to an increased risk of infection
    from encapsulated organisms (i.e. bacteria with a
    protein coat)
  • Emergency → patient will die within 1-2 days without
    treatment
38
Q

what are the symptoms of acute chest syndrome

A 
Classified by two of the following symptoms:
- Chest pain
- Fever
- Pulmonary infiltrate/focal abnormality
- Respiratory symptoms
- Hypoxaemia
- 80% of patients have a vaso-occlusive crisis during
acute chest syndrome
39
Q

what increases the risk of sickle cell disease

A

afro caribbean parents

40
Q

what cases the…

  • hepatosplenomegaly syndrome
  • lung field rales/ sonorous wheeze
  • low haemoglobin
  • white cell count increase
  • platelet count lowering
  • high ESR
  • chest radiograph with bilateral hazinesss
  • diactylitis
  • peripheral blood smear
A

Hepatosplenomegaly → splenic sequestration
syndrome

Lung field rales, sonorous wheeze → lung infection

Low haemoglobin → due to haemolytic anaemia
associated with SCD

White cell count increased → due to infection

Platelet count low → vaso-occlusive crisis → spleen
is blocked and so platelets can’t exit into the
circulation

High ESR → because RBCs are being destroyed
quicker and, therefore, need to be replaced quicker

Chest radiograph with bilateral haziness → lung
infection

Dactylitis → vaso-occlusive crisis in the vessels
leading to and from the peripheral digits

Peripheral blood smear → low oxygen levels lead to
sickling of sickle cell RBCs

41
Q

what does genetic counselling teach

A

The genetic inheritance of SCD

Disease-related health problems e.g. splenic
sequestration syndrome

Future family planning

42
Q

How do you cope with a child who has a chronic illness

A
  1. learn about the illness
  2. join a support group
  3. face the possibility of early death
  4. maintain open and honest communication
  5. share leadership
  6. include all family members in decision making
43
Q

What is auscultation

A

this is the action of listening to a person’s lungs, heart and intestines during a physical examination in order to find a diagnosis

44
Q

What is the difference between foetal and adult haemoglobin

A 
Foetal Haemoglobin 
- has a higher affinity for oxygen than adults, can carry 30% more oxygen, this is because the maternal blood has to dissociate from oxygen in an area that has a low partial pressure for oxygen this means that the fatal haemoglobin needs to have an higher affinity in this area in order to bind to it  
- 2 alpha, 2 gamma chains
(dominates up to 6
weeks of age)

Adult haemoglobin

  • has 2 alpha chain and 2 beta subunits
  • dominates after 6 weeks of age
  • lower affinity for oxygen
45
Q

What happens once the red blood cells are infected

A

parasitisation of AS red blood cells this increases the oxygen consumption and deceases the partial pressure of oxygen therefore the red blood cells sickle
- these red blood cells are removed as fewer surface proteins which adhere to the endothelium

46
Q

What does hyroxycarbomide do

A

this is a form of treatment for sickle cell anaemia that promotes production of foetal haemoglobin so they can pick up more oxygen

  • given to patients once a day
  • drug is withdrawn and causes increase in haemoglobin
47
Q

what are the ways of diagnosing sickle cell anaemia

A
  • solubility test
  • electrophoresis
  • blood smear
48
Q

who should receive genetic counselling

A
  • parents of new borns with a sickle cell disorder or trait

- pregnant women/prenatal counselling

49
Q

How do you do a electrophoresis of sickle cell anaemia

A 
Able to differentiate between heterozygous (HbAS)
and homozygous (HbSS) states

The charged glutamic acid AA changes the speed
which the sample moves

Therefore, in HbAS one strand moves much faster
than the other

On the other hand, in HbSS both strands move quickly

FunMed PBL (7 decks)

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