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RESIT Termination of Pregnancy

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					RESIT 2005

Question 1
Miss X comes to the GP to ask for the oral contraceptive pill.
a) List six things to bear in mind when talking to patients about sex.
                                                                                        (12 marks)
         Remember that the patient may feel embarrassed and awkward. You should
          therefore try to put them at their ease and keep awkwardness to a minimum.
         The patient may be worried about confidentiality – understandably, they may not
          want other people to know about their sexual problems and so you must always
          remember to assure patients about confidentiality.
         Be aware of your own opinions and beliefs. If you bear these in mind, then you
          are less likely to impose these views on your patient.
         Never make assumptions – it is very easy to make assumptions about people’s
          sexuality/sexual behaviour etc…. but you should avoid this at all costs, as it can
          lead to wrong conclusions and this can be detrimental to the doctor-patient
          relationship and care of the patient. Therefore, always ask, never assume!
         Bear cultural differences in mind – many cultures have specific views about sex
          and so it is best to be aware of these – and if in doubt, ask!
         Be aware of your own tone of voice and body language. These can be very
          important to the patient – if your tone of voice sounds judgmental or disapproving,
          then the patient may not say what they want to say. If your body posture portrays
          embarrassment or inapproachability, then again, a patient may not be comfortable
          telling you what they need to say. This may lead to the patient not receiving the
          best care, which is not acceptable.

b) List four pieces of more detailed information the doctor might need to gather from this young
woman about her sexual relationships and history. (8 marks)

          Menstrual cycle information: When was her last period? Are her periods regular?
           Painful?
          Has she ever had a pregnancy, mniscarriage or abortion in the past?
          Is she currently sexually active? If so, is this with a steady partner or partners?
          Last sexual intercourse: when was this, who with (man or woman?), what kind of
           protection did she use…
      Question 2
      Mrs EP is a 45 year old woman admitted following a mugging. She is found to have a fracture of
      the left humeral shaft.
      a) In ideal conditions, how long will it take to form a bony callus (1 mark)
      6 weeks
      b) List 3 causes of delayed healing (3 marks)
      Malnutrition, infection (and immune system action) and nicotine intake.

      c) Name 6 complications of wound healing and briefly describe their aetiology and pathogenesis
      (2 marks each)
      Chronic wounds – wounds that will not heal, persist for far longer than they should. This is often
      due to venous ulcers or wounds in areas where there is little blood supply (the infamous shin
      wounds in the elderly!)
      Infection – when the wound gets infected by bacteria – this can be by common skin bacteria like
      S. Aureus, but it will slow the wound healing process.

      d) Name the shoulder movement illustrated by each of these diagrams (1 mark each)




                                                                                     Adduction




Flexion




Circumduction

                                                                             Medial Rotation
Question 3
The graph below shows a “Forest plot”, taken from the Cochrane library, displaying results of a
meta-analysis for the effects of barbiturates in preventing death in people with acute traumatic
brain injury. The lines represent estimates of Relative Risk (RR) with their 95% confidence
intervals
a) What is represented by the diamond in the diagram? Does it suggest any benefit for
barbiturates? (7 marks)
The diamond represents the combined relative risk and the confidence interval of this RR. It
has taken the results of all the individual studies and combined them into an overall value for the
relative risk. The centre of the diamond represents the combined relative risk. It lies at 1.09. This
would imply a very slight increased risk in death, when barbiturates are used. However, the
95% confidence interval (represented by the points of the diamond) is 0.81 – 1.47. This means
that the true value of the relative risk will lie between the two values in 95% of cases. This means
that the use of barbiturates could have either a protective or harmful effect – the results are
therefore statistically insignificant and no conclusion can be reached. The meta-analysis therefore
does not suggest a benefit for barbiturates (n.b. it also does not suggest a harmful effect!)

b) What is meant by “heterogeneity” in a meta-analysis? Is there any evidence for heterogeneity
in this Forest plot? (7 marks)
Heterogeneity is a description of how different the values in a particular set of results are. If the
results are heterogeneous then there is a large variety (no coherence) between the results and
these differences are larger than those that can be attributed to chance.
No, there is no evidence of heterogeneity here. The results are said to be homogenous. This can
be seen as it is possible to draw a line that will cross the confidence interval lines of all 3 studies
– that is, there is presence of multiple random intercepts in a dataset. The chi-square test gives a
value of 0.24, which indicates no heterogeneity.

c) Explain what is meant by publication bias in a meta-analysis. Do you think there is publication
bias in this case? Explain your answer briefly. (6 marks)

Publication bias is the phenomenon by which journals only tend to publish studies that show a
significant result. In this way, it may seem that there is a benefit to the treatment, but if you looked
at the unpublished studies, you may get a very different picture. I do not think that there is
publication bias in this case, as all three of the studies show no statistical significance, but have
still been published!
Question 4
Mr C is 23 years old and lives at home. He finds it difficult to make friends and shuns company,
preferring to stay at home. His mother became worried after her son had told her that “spies”
were watching their home and were “out to get him”. After some difficulty, she managed to get her
son via his GP to see a psychiatrist, who put him on medication. Following three weeks of
treatment, Mr C began to feel much better although in the first week he felt slightly sedated.
However, after these three weeks he now refused to continue his medication, complaining that he
had developed stiff muscles and spasms in his neck and face. Mr C‟s doctor changes his
prescribed medication and tells him that he must have his blood tested.

a) What disease do you think Mr C is suffering from and what type of drug was prescribed; give a
named example? (4 marks)
Schizophrenia
Typical anti-psychotic (neuroleptic) e.g. chlorpromazine

b) What is the scientific rationale for the treatment of the above disease? (6 marks)
Schizophrenia is thought to be due to errors in the dopaminergic neuronal pathways of the brain,
specially the mesolimbic and mesocortical pthways. Evidence comes from the correlation
between dopamine D2 antagonism and anti-psychotic activity. This is further backed up by the
psychotic action of amphetamine, which releases monoamines, such as dopamine. There is also
some evidence on PET scans of increased D2 receptors in the nucleus accumbens of
schizophrenics. The treatment rationale, tehn, is if dopaminergic transmission causes
schizophrenia, blocking it should decrease it. The treatment is therefore dopamine receptor
antagonists.

c) Why has Mr C developed stiff muscles and spasms in his neck? Further if Mr C is maintained
on the first medication he may develop another movement disorder. What is it called and give a
possible explanation of why it develops? (3 marks)
This is caused by dopaminergic antagonism in the striatum – the extra-pyramidal effects of
treatment. If he continues on this treatment he may develop tardive dyskinesia – stereotyped tic-
like movements. It is thought that under constant antagonism, the postsynaptic dopaminergic
receptors become supersensitive to stimulation, causing the symptoms.

d) What other unwanted effect/s may be observed with the first line medication? (3 marks)
Akathsia, rigidity and bradykinesia, sedation, bradycardia, dry mouth (anti-muscarinic effect)

e) What type of drug was Mr C placed on after complaining about his neck? Give an example and
explain how its pharmacological properties differ from that of the first drug and are there any other
major unwanted action/s attached to this type of drug? (4 marks)
Atypical antipsychotic e.g. clozapine
Although these are also dopamine antagonists, they are also thought to have some 5-HT2
receptor antagonism properties. They are more effective against the negative symptoms of
schizophrenia than typical agents.
The most significant side effect of this drug is the small risk of agranulocytosis. Although rare,
this is extremely serious.
Question 5

Give reasons why a patient may receive some of the following drugs either as a pre-medication
prior to a surgical operation or in the operating theatre, indicating the mechanism of action. (20
marks)
a) Atropine (2 marks)
This is a muscarinic acetylcholine receptor antagonist. It is used to dry the mouth and stop
bronchial secretions, so intubation and ventilation are easier and safer.

b) Diazepam (3 marks) This is a benzodiazepine. It acts on the GABA-A receptors to potentiate
the effect of the neurotransmitter GABA. It is used in pre-med to reduce anxiety (it is anxiolytic)
and will also produce some sedation.

c) Pancuronium (3 marks) This is a nicotinic receptor antagonist, which acts as a competitive
antagonist. It therefore causes non-depolarising block at the neuromuscular junction. They are
used, once GA is induced, to cause muscle relaxation. This facilitates surgery.

d) Neostigmine (3 marks) This is an anti-cholinesterase. That is, it inhibits the enzyme
acetylcholinesterase. This enzyme usually breaks down ACh. Therefore, when inhibited, the ACh
concentration increases – this can therefore overcome the block caused by pancuronium.

e) Thiopental (thiopentone) (3 marks)
This is a general anaesthetic, given intravenously that is used to induce anaesthesia. It is a
barbiturate and therefore binds to the modulatory barbiturate-binding site on the GABA-A
receptor, potentiating GABA‟s effect.

f) Nitrous oxide (3 marks)
This is an inhalation anaesthetic. It is not potent enough to use on it‟s own, but in combination
with another inhalation agent (e.g. halothane) it can be used to maintain anaesthesia.

g) Fentanyl (3 marks)
This is an analgesic agent, a synthetic analogue of morphine. It is an agonist at the opioid µ
receptors. This produces analgesia mainly by inhibiting pain transmission in the dorsal horn of the
spnal cord and by inhibiting the activation of pain afferents in the periphery.
Question 6
  Amy is a 3 month-old girl, normal in all respects except that her head diameter is larger than
  normal. CT and MRI scans reveal that she has grossly enlarged lateral and third ventricles.
a) What is the name of Amy‟s condition? (2 marks)
Hydrocephalus

b) What is the cause of the ventricular enlargement and why is it present in the lateral and third
ventricles but not the fourth ventricle? (8 marks)
The ventricular enlargement is due to an obstruction ot the flow of CSF. The CSF continues to be
produced, but it‟s flow is impede, and so it collects in the ventricles. These accordingly enlarge
(imagine filling a balloon with water). Hre, the obstruction must be within the cerebral aqueduct.
Most CSF is produced within the lateral ventricles. It then circulates through the interventricular
foramen, into the third ventricle and then through the cerebral aqueduct into the fourth ventricle. If
the cerebral aqueduct is obstructed, then the CSF will still be produced by the lateral ventricle
and pass into the third ventricle, but will not be able to pass into the fourth ventricle effectively,
This will lead to enlargement of the lateral and third ventricles, but not the fourth.

c) The ventricles were visualized in CT and T2-MRI scans. What are the underlying principles of
the two types of scan and would the ventricles be seen as light or dark regions in each type (8
marks)
In a CT scan, a large number of 2-dimensional X-Rays are taken from around a single axis of
rotation. A computer then assembles these images into the CT scans. The ventricles would show
up as darker areas.
In an MRI scan, the patient is subjected to a magnetic field. Under the influence of this field,
hydrogen atoms vibrate and this vibration can be measured and reconstructed into images –
different tissues give off characteristic patterns of vibration. The ventricles would appear lighter.

d) If the condition is progressive, what treatment could be used to prevent further ventricular
enlargement? (2 marks)

You would perform surgery to place a ventricular cathether into theventricular system to create a
ventricular shunt. This creates a path for the CSF to flow through (basic plumbing!)
Question 7
A 32 year old man presents with weight loss, a markedly increased neutrophil count and
splenomegaly. A diagnosis of chronic myeloid leukaemia (CML) is made

a) What is the key molecular abnormality underlying CML? (2 marks)
Producation of Bcr-Abl protein due to a t (9.22) translocation.

b) What are the key biological effects on cell function that result from this? (9 marks)
Abl is an oncogene. When it is translocated to chromosome 9, it gets joined to the bcr (a
promoter) and so there is excessive production of abl. Abl is a tyrosine kinase. This means that
the cells are hyper-responsive to growth factors.
c) What is believed to be the cell from which CML originates? Describe the evidence for this?
(4marks)
d) What treatments for CML could be used in this patient? (4marks)
Question 8
A GP referred a 30-year old woman who had a moderately abnormal cervical smear to a
consultant in the local hospital. Colposcopic examination, using acetic acid, revealed a white area
in the transformation zone. A cone biopsy was performed and the sample was sent for histology;
this confirmed cervical intraepithelial neoplasia (CIN) grade 3. The woman later asked the doctor
what had caused her disease. She was checked with regular smears after her operation and now
has a clean bill of health.
a) What is the transformation zone? (8 marks)
The transformation zone is an area of the cervix where there is an abrupt change in histology. In
the vagina and outer cervix, the external surface is covered with stratified squamous, whereas the
cervical canal is covered with columnar epithelium. The area od transition between the two is the
transformation zone.

b) What is cervical intraepithelial neoplasia grade 3? (8 marks)

c) What is believed to be the proportion of women with CIN3 who progress to cervical cancer?
                                                                                        (2
                                                                                marks)
d) What is believed to be the main causative factor of CIN3? (2 marks)
Question 9
Mutations in the gene OSX cause Opitz Syndrome, a failure of development which leads to
midline defects such as cleft lip (in mild cases) and more extreme phenotypes. OSX is X linked.
Opitz syndrome may also be caused by dominant mutations in a gene on chromosome 22.

a) In the family below, is it more likely that the disease is caused by an X linked or an autosomal
mutation? (4 marks)


                                                              It is more likely to be an X-
                                                              linked mutation, because
                                                              only males are affected. If it
                                                              were an autosomal mutation,
                                                              you would expect both males
                                                              and females to be affected.




b) In another family the X linked form of the disease was proved to be present by the finding of a
nonsense mutation in OSX. What is a nonsense mutation? (4 marks)
A nonsense mutation is a kind of point mutation that changes the DNA sequence, so instead of
coding for an amino acid, it codes for a STOP. This causes the premature cessation of DNA
transcription and so the mRNA is shorter than it should be. When this mRNA is translated, a
truncated protein will result.

c) Physicians working with a third family found by fluorescence in situ hybridization a
microdeletion of 22q11.2 in a newborn boy with Opitz syndrome. Indicate on this diagram of
chromosome 22 your best guess as to where this deletion might be located. (4 marks)




                               It is on the LONG arm, at
                               the 2nd sub-band of the 11th
                               band.




d) The microdeletion was big enough to remove the entire relevant gene. What does this tell you
about the likely mechanism by which the dominance of the mutation occurs. (4 marks)

e) The phenotype of Opitz syndrome is very variable, what is the term used to describe genes
where the same mutation can give different degrees of severity of phenotype in different
individuals? (4 marks)

Question 10
Mrs P, aged 50 is limping and complains of right posterior calf pain. You suspect an achilles
tendon sprain
a) Name the muscles that insert onto the calcaneum and give their nerve supply (4 marks)

Gastrocnemius (tibial nerve)
Soleus (tibial nerve)
Plantaris (tibial nerve)

b) What action do the superficial muscles of the calf have on the ankle? (1mark)
They are the plantar flexors of the ankle

c) Name the cutaneous nerve that runs along the achilles tendon (1 mark)
Medial Sural Cutaneous Nerve

On examination, Mrs P‟s right calf is swollen and hot. Pulses are normal. You suspect impaired
venous return.
d) Complete this table of sites in the lower limb where pulses can be felt (6 marks)

Site where pulse can be palpated                    Name of artery
Popliteal fossa --behind the knee                   Popliteal artery
On top of the foot, lateral to EHL tendon           Dorsalis Pedis Artery
Back of ankle, behind medial malleolus              Posterior tibial artery

e) Name the superficial vein found on the posterior calf. Where does this terminate? (3 marks)
Small saphenous vein  popliteal vein

f) Name the structures labelled A-E involved in the venous pump of the calf in the
diagram below (5 marks)
A Great saphenous vein
B Tibial Nerve
C Gastrocnemius
D Perforating Vein
E Venae comitantes of the posterior tibial artery
Question 11
Brooklyn aged 2 was pulled up sharply via his left arm onto a bus by his mother. His elbow is
painful to touch and he refuses to supinate his forearm. You suspect subluxation of the radial
head („pulled elbow‟).
a) Name two ligaments that help to keep the radial head in contact with the ulna (2 marks)
Annular ligament, quadrate ligament
b) Name two muscles inserting in the region of the elbow that supinate the forearm (2 marks)
Biceps brachii, supinator
c) Name the large nerves that are related to the following regions of the elbow (3 marks)
Region           Nerve
Medial           Ulnar
Anterior         Median
Lateral          Radial

d) Label this diagram of the bones of the elbow
Lateral Intermuscular Septum                                         Medial Intermuscular Septum




                                                                         Coronoid Fossa
            Radial fossa
                                                                         Medial epicondyle
            Capitulum
                                                                         Trochlea




          Radial Head
                                                                       Coronoid process
            Radial Notch


   Radial Tuberosity




  Question 12 Mr J, aged 75, has had difficulty in passing urine for 10 years and the urine stream
  is weak. You suspect an enlarged prostate gland.
  a) What part of the urethra passes through the prostate gland? Is this portion normally the widest
  or narrowest portion of the urethra? (2marks)
  Prostatic (proximal) urethra. Usually widest part of the urethra.

  b) What change would you expect to see in the detrusor muscle of the bladder? (1 mark)
  It would be distended (enlarged)

  c) Name the nerves and spinal segments responsible for detrusor muscle contraction (3 marks)
  Nerves of the vesical plexus --

  d) If an aspiration needle is placed into the full bladder above the pubic bone will the needle pass
  through the peritoneum? (1 mark)
  No
e) Through which route might metastases to travel from the prostate to the spine as a result of
coughing? (3 marks)
Blood can be forced from the prostatic venous plexus to the vertebral venous pressure when
pressure is raised (e.g. when coughing). In this way, the cancer cells can travel to the vertebral
venous plexus and metastasize.

f) Give the approximate length in cm of the male and female urethra (2 marks)
Male: 20cm
Female: 5cm
g) Label this diagram of a posterior view of the bladder (7 marks)

                             Median Umbilical Ligament



                                 Ureter


                           Vas deferens


        Posterior aspect of bladder


                      Ampulla of vas




                           Seminal Vesicle



                                     Prostate Gland

Question 13 A 20 year old man presented to the Accident & Emergency Department with a short
history of severe headache, high fever, nausea and vomiting.

a) List three possible causes of his condition. (2 marks each)
Meningitis
Encephalitis
Influenza

A lumbar puncture was performed and the CSF gave the following results:
White blood cells 220 /mm 3 (normal <5 /mm3)
90% polymorphonuclear cells (neutrophils)
Red blood cells 16 /mm 3 Protein 0.7g /dL (normal < 0.41 g/dL)
Glucose 1.5 mmol /L (blood glucose6.1 mmol/l)

b) What diagnosis is this most compatible with? You must explain your answer briefly. (2 marks)
Meningitis -- the hugely increased WBC in CSF with a predominance of neutrophils is highly
indicative of meningitis. In encephalitis, the WBC would not be as raised (or may even be
normal!!)

c) List three additional tests that could be performed on the CSF to help with the diagnosis and
aid treatment. (2 marks each)
Opening pressure (>180mmHg is indicative of meningitis)
Proteins (>4.5mg/dL)
Gram staining for bacteria

d) List three ways in which this disease might be prevented in others. (2 marks each)
Immunisation against common meningitis causing agents such as haemophilus and neisseria
meningitidis
Preventative antibiotics for family members/housemates of the patient.
Isolation of patients with meningitis




Question 14 Janet and John have completed a cycle of IVF and have had a positive pregnancy
test. They have had two previous first trimester miscarriages, and some years ago Janet
underwent a therapeutic termination of pregnancy because the embryo was diagnosed as
suffering from spina bifida. The implanting embryo secreted a hormone that signalled its presence
to the mother:

a) What is the name of this hormone? (1 mark)
Human Chorionic Gonadotrophin
b) What receptor does the hormone act on? (1 mark)
LHCG receptor
c) In which organ are the receptors located? (1 mark)
Ovaries
d) Which hormone is secreted by this organ in response to the embryo? (1 mark)
Progesterone
e) Which hormone was administered early in pregnancy to account for a possible luteal
insufficiency? (1 mark)
Progesterone

The pregnancy has reached the end of the first trimester and all appears well on the scan.
f) What part of the conceptus secretes progesterone? (2 marks)
g) What is the main steroid conversion made by the fetus? (2 marks)
h) What else does the fetus do to steroids? (1 mark)
i) Where in the conceptus is oestriol synthesised? (2 marks)
j) What enzyme is responsible for converting androgens to oestrogens? (2 marks)

Janet was advised to take 1500 µg of folic acid daily before the cycle of IVF began.

k) Why was she advised to take such high folic acid supplements? (4 marks)
Folic acid deficiency has been suggested as one of the causes of spina bifida and so, with her
medical history, it would be advisable for her to make sure her folic acid levels are not too low.

l) Why was she advised to start the folic acid supplements before the start of the cycle of IVF? (2
marks)
Because it may take some time before her folic acid levels rise and once she has started the IVF
she may become pregnant immediately – too late to start!




Question 15
This question does not concern any particular patient
Comment on psychological problems during pregnancy and early postpartum (20 marks)

A pregnancy can result in significant stress for the mother, especially if the
pregnancy is unwanted. Being pregnant presents significant worries - over the
health of the foetus, the reaction of family/friends, the financial burden of a child,
arrangements with work, lack of support and knowledge etc…..
A significant proportion (some studies suggest as many as 20%) of pregnant women also
experience depression. This is particularly prevalent in young and first-time mothers, especially
where they feel they have no control over their situation. Depression is also prevalent in women
where the pregnancy is disapproved of by family or there are other serious adverse factors.
There are significant body-image changes associated with pregnancy. The weight-gain can
present serious psychological issues, especially in women with pre-existing eating disorders. The
pregnancy can exacerbate bulimia and anorexia.
Post natal depression is a serious form of depression suffered by 5-20% of women. A milder
form of depression, maternal blues (or baby blues) affect a much larger proportion -- as much as
80%.
The baby blues a mild and transitory form of 'moodiness' suffered by up to 80% of postpartum
women. Fathers also suffer from postpartum depression. Symptoms typically last from a few
hours to several days, and include tearfulness, irritability, hypochondriasis, sleeplessness,
impairment of concentration, isolation and headache. The maternity blues are not considered a
postpartum depressive disorder.
Post-natal depression has the same signs and symptoms of major depression. These
include depression of mood and anhedonia (lack of pleasure at usually pleasurable
events) alongside feelings of fear/foreboding, inability to feel other emotion, disturbed
sleep and eating patterns, as well as many other signs. It lasts a lot longer than the baby
blues (which generally last less than 1 month). The mother may have trouble bonding
with the child.
New mothers can also present with post-partum anxiety and post-partum obsessive
compulsive disorder and post-traumatic stress disorder.




Question 16 This question does not concern any particular patient Comment on
psychological considerations in ante-natal care (20 marks)

Just go away, you bastards!!!
Question 17
This question does not concern any particular patient
What are the conditions necessary for the establishment of a profession? Demonstrate how the
medical profession meets these conditions. (20 marks)

A profession is an occupation that requires extensive training and the study and mastery
of specialized knowledge, and usually has a professional association, ethical code and
process of certification or licensing.

I think this is sociology so I’m not going to do it!
Question 18 Mrs S. aged 45 complains that she often wakes up choking during the night. On
examination she has a smooth bilateral swelling at the root of her neck that moves upwards when
she swallows. She is diagnosed as an enlarged thyroid gland.

a) Why does the thyroid gland normally move upwards on swallowing? (3 marks)
The thyroid gland lies on either side of the larynx and moves with this structure. In the pharyngeal
phase of swallowing, the larynx is elevated and pulled forward to the epiglottis to relax the
cricopharyngeus muscle. This passively shuts off its entrance and the vocal cords, to prevent
aspiration (entry of food nto the airways).

b) Why might an enlarged thyroid cause breathing difficulties? (3 marks)
The thyroid gland lies against the trachea. If the gland enlarges, it may press against the trachea
and compress it, narrowing the airway. This will make breathing laborious.
Mrs. S. has surgery to remove part of the thyroid gland. Immediately afterwards she has a very
hoarse voice. You suspect she has sustained unilateral nerve damage during surgery while
clamping an artery that supplies the thyroid gland.

c) Name the nerve damaged during surgery and the artery it is closely related to (2 marks)
Recurrent laryngeal Nerve, internal carotid artery.

d) Briefly describe the venous drainage of the thyroid gland (4 marks)
 Blood is collected into a venous network which is found on the surface of the gland. From here it
drains by three pairs of veins -- the superior, middle and inferior thyroid veins. The superior and
middle veins drain into the internal jugular vein, the inferior drains into the brachiocephalic veins
in the thorax.

e) Write the name of each of the structures labelled A – H in the diagram of a posterior view of
the thyroid gland in the table below (8 marks)




                                                                   A: Superior parathyroid Gland
                                                                   B: Inferior Thyroid Artery
                                                                   C: Brachiocephalic Artery
                                                                   D: Trachea
                                                                   E: Aorta
                                                                   F: Left recurrent Laryngeal nerve
                                                                   G: Left external carotid
                                                                   H: Superior thyroid artery




Question 19
This question does not concern any particular patient
Explain the endocrine pathways via which hydrophobic and hydrophilic hormones interact to
restore blood pressure following a loss of circulatory volume. (15 marks)

When there is a loss of extracellular fluid volume, it is detected by the juxtaglomerular cells of
the kidney. The JG cells are triggered to release renin (by the rapid release of prostaglandins).
Renin is an enzyme which catalyses the conversion of angiotensinogen  angiotensin I. The
angiotensin I circulates in the blood, and in the lung, the action of angiotensin converting
enzyme converts it to angiotensin II. Angiotensin II acts on the adrenal cortex, especially on the
zona glomerlosa cells, to release aldosterone.
Angiotensin II has actions that help to restore blood pressure. Angiotensin II acts as a
vasoconstrictor. By causing vasoconstriction, angiotensin II increases peripheral resistance.
As BP=COxTPR, if total peripheral resistance increses, then blood pressure will also increase.

Aldosterone acts to increase blood pressure, by increasing water reabsorption. Aldosterone
binds to the mineralocorticoid receptors on the principal cells of the distal convoluted tubule and
collecting duct of the kidney. It is a hydrophobic (lipophillic) hormone. It increases the
permeability of their apical (luminal) membrane to potassium and sodium and activates their
               + +                                                                   +
basolateral Na /K pumps, stimulating ATP hydrolysis, reabsorbing sodium (Na ) ions and
                                                     +
water into the blood, and secreting potassium (K ) ions into the urine. The reabsorption of the
water means that extracellular circulatory volume is increased.

Reduced plasma volume can also be detected by the baroreceptors in the arch of the aorta and
the carotid baroreceptors. Activation of these baroreceptors causes release of ADH from the
posterior pituitary (ADH is produced by the paraventricular and supraoptic nuclei neurons of the
hypothalamus and is then transported to the pituitary). ADH causes reabsorption of water from
the DCT and so causes less water loss in the urine. This means that ECV is increased and so
blood pressure maintained. ADH also has a pressor effect – that is, it causes vasoconstriction.
This also increases blood pressure, as described above.




Question 20
This question does not concern any particular patient
a) Identify the structures indicated by the letters A to E on the diagram; write your answers in the
box below (2 marks each)
                                                            A: hypothalamus
                                                            B: Supraoptic-hypothalamic
                                                            tract
                                                            C: Posterior pituitary
                                                            D: Anterior Pituitary
                                                            E: Hypophyseal portal
                                                            vessels




b) Name 2 hormones transported along structure B (2 marks)
Antidiuretic hormone, oxytocin

c) Name 5 hormones secreted from region D (5 marks)
Growth hormone, Thyroid stimulating hormone, prolactin, luteinising hormone,
follicle stimulating hormone.
d) Name a factor arising in region A which is capable of inhibiting hormone
synthesis/secretion in region D (1 mark)
Somatostatin

e) What is the most likely cause of failure in structures B and D? (2 marks)
Benign adenoma of the pituitary

				
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