Testing, Testing, One, Two, Three...

You should by now be testing yourselves regularly to make sure that the material you are covering is moving from short-term to long-term memory. This website will help you do that by asking you to match structures to their name, and then label them yourself. Fifteen minutes each day should do the trick. Try it!

Biochemistry That Matters

but that apparently you have not covered yet....

A patient with familial hypercholesterolaemia undergoes a detailed serum lipid and lipoprotein analysis. Studies demonstrate elevated cholesterol in the form of increased LDL without elevation of other lipids. This patient's hyperlipidemia is best classified as which of the following types?

A. Type 1
B. Type 2a
C. Type 2b
D. Type 3
E. Type 5

The correct answer is B.

Hyperlipidemia has been subclassified based on the lipid and lipoprotein profiles. Type 2a, which this patient has, can be seen in a hereditary form, known as familial hypercholesterolemia, and
also in secondary, acquired forms related to nephritic syndrome and hyperthyroidism. The root problem appears to be a deficiency of LDL receptors, which leads to a specific elevation of cholesterol in the form of increased LDL. Heterozygotes for the hereditary form generally
develop cardiovascular disease from 30 to 50 years of age. Homozygotes may have cardiovascular disease in childhood.

Type 1 (choice A) is characterized by isolated elevation of chylomicrons.

Type 2b (choice C) is characterized by elevations of both cholesterol and triglycerides in the form of LDL and VLDL.

Type 3 (choice D) is characterized by elevations of triglycerides and cholesterol in the form of chylomicron remnants and IDL.

Type 5 (choice E) is characterized by elevations of triglycerides and cholesterol in the form of VLDL and chylomicrons.

Physiology Question Explanation

Only one of you attempted this question, which actually is extremely important. Hence it's worth re-stating together with the explanation for all you clinical students out there.

A 26-year-old man is admitted through the emergency department to the hospital for a heroin overdose. His heart rate is 45 beats/min, and his blood pressure is 75/40 mm Hg. Which of the following best depicts the results from an arterial blood sample ?

pH PaCO2 (mm Hg) HCO3- (mEq/L)
A. 7.22 66 26
B. 7.34 29 15
C. 7.40 40 24
D. 7.47 20 14
E. 7.49 48 35

The correct answer is A.

This man has a respiratory acidosis. Overdose with drugs that suppress ventilation (e.g., heroin, morphine, barbiturates, methaqualone, and "sleeping pills") often causes hypercapnia. In patients with an intact renal response, the respiratory acidosis causes a compensatory rise in plasma HCO3-, which lessens the fall in pH. However, the renal response requires several days to develop fully. The plasma HCO3- of 26 mEq/L (normal: 22-28 mEq/L) for this man is typical of acute respiratory acidosis with little or no renal compensation.

Choice B reflects metabolic acidosis.

Choice C is normal.

Choice D reflects respiratory alkalosis.

Choice E reflects metabolic alkalosis.

Mastication Question

Question: Contraction of which muscles contributes most to the backward movement of the lower jaw during the process of mastication?

Answer: Mastication is a complex process involving alternating elevation, depression, forward movement, and backward movement of the lower jaw. The backward movement step is accomplished by the posterior fibers of the temporalis muscle.

The digastric helps to depress the lower jaw during chewing.

The lateral pterygoid helps to move the lower jaw forward during chewing.

The medial pterygoid helps to elevate the lower jaw during chewing.

The mylohyoid helps to depress the lower jaw during chewing.

Muscles of Mastication

Some of you appeared confused by the muscles of mastication last week. Try this one:

Contraction of which of the following muscles contributes most to the backward movement of the lower jaw during the process of mastication?

A. Digastric
B. Lateral pterygoid
C. Medial pterygoid
D. Mylohyoid
E. Temporalis

Correct answer and explanation next week.

Surgery Question

Must not forget our third year students struggling with surgery. Here is one for you:

Crohn's disease:

A. Is caused by Mycobacterium paratuberculosis.
B. Is more common in Asians than in Jews.
C. Tends to occur in families.
D. Is less frequent in temperate climates than in tropical ones.
E. Is improved by smoking.

Biochemistry That Matters

And for those of you more interested in biochemistry, here is another:

A patient with familial hypercholesterolaemia undergoes a detailed serum lipid and lipoprotein analysis. Studies demonstrate elevated cholesterol in the form of increased LDL without elevation of other lipids. This patient's hyperlipidemia is best classified as which of the following types?

A. Type 1
B. Type 2a
C. Type 2b
D. Type 3
E. Type 5

Neurophysiology

Just to prove that this site is about more than anatomy, here is a neurophysiology question for Year 2 students:

Administration of an experimental drug that acts on PNS myelin is shown to increase the space constant of an axon in a peripheral nerve. Action potentials traveling down the axon would be predicted to be

A. faster
B. larger
C. slower
D. smaller
E. unchanged

Correct answer and explanation will be posted next week.

Cranial Nerve Quiz

Which cranial nerve exits the skull base at the pars nervosa of the jugular foramen?

Quiz Response

Closure of the neural tube occurs around day 26 of embryonic life.

As the neural tube forms, the closing process is critical, occurring from the cranial to the caudal end as the anterior neuropore closes around day 24, the posterior around day 26. This is a critical event, as defects in closure may result in spina bifida or other neural tube defects. The risk of a neural tube defect can be decreased by folic acid supplements.

Surgery Quiz Questions for the USMLE

Preparing for the United States Medical Licensing Exam Step 1, 2 or 3 is difficult, time-consuming, and anxiety-provoking. Knowing the information cold is the best way to ace the test. Although the test is multiple-choice, studies have shown that being able to answer unkeyed questions shows a higher level of mastery of the material. Try these to see how you are doing...

High Power Microscopy is Low Power Histology

In the histology lab, a common mistake is to "zoom" right into every tissue. Make sure you spend time with your low-power objectives ... this strategy will really pay off during the exams. Check out the histoweb site for a good overview of why histology matters.

Skeleton and Skull Self-Test

For those of you still unsure of the names of all those cracks and holes, here is a self-test.

Renal Physiology

Another FREE site developed by medical students which summarizes the important aspects of renal physiology. Covers:

· Renal Handling of Sodium and Potassium

· Urinary Concentration & Dilution

· Diuresis & Diuretics

· Acid-Base Balance

· Divalent Cations

Take the quiz at the end.

Attention Year 2 Students

Closure of the neural tube occurs on around which day of embryonic life?

a) 26
b) 38
c) 56
d) 74
e) 90

Answers here please. Correct answer will be posted next week.

Attention Year 1 Students

Most fascia of the body that attach to bones attach by which of the following mechanisms?

A. Blending with the covering periosteum
B. Inserting deeply into the cancellous bone
C. Inserting deeply into the cartilage
D. Inserting deeply into the diaphysis
E. Inserting deeply into the marrow

Answers Here please. Correct answer and explanation will be posted next week.

Attention Year 1 and 2 Students

A 25-year-old female presents to her obstetrician after taking a home pregnancy test with a positive result. She states that twins run in her family and would like an ultrasound to determine if she has a twin pregnancy. Splitting of the embryo at the blastocyst stage results in which of the following?

A. Conjoined twins
B. Dizygotic twins
C. Fraternal twins
D. Monozygotic twins
E. Single gestation

Post your answers here. I will post correct answer on Friday.

Attention Years 1 & 2 Students: Embryology Question

The heart of an embryo first begins beating at which of the following ages?

A. 2 weeks

B. 3 weeks

C. 4 weeks

D. 6 weeks

E. 8 weeks

NB: Your final exam questions will be True/False and NOT MCQs as above.

Your Answers please.

Attention Year 2 Students: Neuroanatomy Question

A neuroscientist is investigating the development of the nervous system. In his experiments, he microinjects a dye into the embryo of an animal subject in vivo. After birth, he performs histological studies to determine the destination of the dye. In one animal subject, he locates the dye in the dorsal horn of the spinal cord. Which of the following locations in the embryo was the most likely site of the injection?

A. Alar plate

B. Basal plate

C. Neural crest

D. Rostral end of neural tube

E. Sulcus limitans

NB: Your final exam questions will be True/False and NOT MCQs as above.

Your Answers please. I will post correct answers on Friday.

Quiz Results

1. The neurovascular bundle passes deep to the internal intercostal muscles. True

2. The foramen spinosum transmits the middle meningeal artery. True

3. The dura is neuroectodermal in origin. True

Most of you got this last one wrong. Google the words neuroectoderm and dura and you will find information about a rare tumour called Ewing's Sarcoma.


4. The spinous processes of the thoracic vertebrae allow easy introduction of needles between the vertebrae.

False. This is why a lumbar puncture in the thoracic spine would be difficult. In any case, the spinal cord would be at risk.