Skin

Q: During embryonic development, neural crest cells migrate to the skin. Some of these cells differentiate to produce melanin from tyrosine. These cells may be destroyed in a patchy distribution by an autoimmune process. What is the most likely condition to result from this autoimmune process?

Vitiligo. Patchy loss of pigmentation is typically the result of an autoimmune process directed at melanocytes. ---

Q: Which of the following secretes defensive secretions to cause irritation on human skin?

Millipedes. Millipedes secrete defensive fluids that irritate the skin. Centipedes bite. ---

Q: A 22-year-old woman has a congenital anemia. She has required multiple transfusions of red blood cells for many years. She now has a darker bronze colour to her skin on physical examination. Which of the following microscopic findings would most likely present in her liver?

Hemosiderin in hepatocytes. There is 250 mg of iron in each unit of blood. The body has no mechanism for getting rid of excess iron. A small amount of iron is lost with normal desquamation of epithelia, and menstruating women will lose a bit more. The excess iron becomes storage iron, or hemosiderin. Over time, hemosiderosis involves more and more tissues of the body, particularly the liver, but also skin (bronze colour), heart (with heart fail

The following are presumptive skin signs of pregnancy EXCEPT:

Skin

Temperature — hot in thyrotoxicosis, febrile illness; cold and clammy in shock
Hydration — assess skin turgor (pinch skin)
Pallor — check palms, conjunctiva, tongue
Jaundice — check sclera, posterior tongue, skin
Cyanosis — bluish discolouration; check hands (peripheral) and tongue (central)

Read this in General Clinical Examination: Revision Notes & Key Signs

Skin

• Temperature – Thyrotoxicosis, febrile illness, shock,
• Hydration – pinch the skin
• Pallor – Check palms, conjunctiva and tongue
• Jaundice – Sclera, Posterior tongue and skin
• Cyanosis –Bluish discoloration hands and tongue, central cyanosis vs peripheral cyanosis.

Read this in General examination (2) — Past Paper Questions & Answers

What our notes say

The following are presumptive skin signs of pregnancy EXCEPT: (Reproductive Health 1 End of Trimester CAT: 40 MCQs and 4 short answers)
Pigmentation, striae and vascular spiders are classic skin changes. (Reproductive Health 1 End of Trimester CAT: 40 MCQs and 4 short answers)
The skin disease is limited to hands, forearms and face. (Internal Medicine Rheumatology CAT: 30 MCQs and 5 short answer questions)
Other tests: FeNO, skin-prick or specific IgE (allergy), blood eosinophils, bronchial provocation (methacholine), chest X-ray (to exclude other causes). (Asthma)
Examination: clubbing, fine bibasal crackles, skin or joint signs of CTD, signs of pulmonary hypertension and right heart failure. (Interstitial Lung Diseases)
Skin changes: linea nigra, chloasma (melasma) and striae gravidarum. (Reproductive Health 1 End of Trimester CAT: November 2018)

Study material on Skin

Images

Number 11 (continued) - result of craniocaudal and lateral folding

Embryo with limb bud (A) and somites (B) alongside photos of albinism (C) and a scaly-skin condition (D)

Clinical photo of a large fluctuant swelling over the lower spine

Clinical photo of a neonate with a lower-body/sacral congenital anomaly

Number 22 - seven photographs of congenital skin and hair anomalies

Photomicrograph of keratinized stratified squamous epithelium (skin)

Photomicrograph of skin showing a hair follicle with an attached sebaceous gland

Practice questions on Skin

During embryonic development, neural crest cells migrate to the skin. Some of these cells differentiate to produce melanin from tyrosine. These cells may be destroyed in a patchy distribution by an autoimmune process. What is the most likely condition to result from this autoimmune process?

Albinism
Atrichia
Ichthyosis
Polythelia
Vitiligo

Answer: E. Patchy loss of pigmentation is typically the result of an autoimmune process directed at melanocytes. ---

Which of the following secretes defensive secretions to cause irritation on human skin?

Millipedes
Centipedes
American killer
Enterobius vermicularis
All of the above

Answer: A. Millipedes secrete defensive fluids that irritate the skin. Centipedes bite. ---

A 22-year-old woman has a congenital anemia. She has required multiple transfusions of red blood cells for many years. She now has a darker bronze colour to her skin on physical examination. Which of the following microscopic findings would most likely present in her liver?

Steatosis in hepatocytes
Bilirubin in canaliculi
Hemosiderin in hepatocytes
Glycogen in hepatocytes
Amyloid in portal triads

Answer: C. There is 250 mg of iron in each unit of blood. The body has no mechanism for getting rid of excess iron. A small amount of iron is lost with normal desquamation of epithelia, and menstruating women will lose a bit more. The excess iron becomes storage iron, or hemosiderin. Over time, hemosiderosis involves more and more tissues of the body, particularly the liver, but also skin (bronze colour), heart (with heart fail

Which factor MOST limits drug absorption through the skin?

Surface area
Blood flow to the skin
Stratum corneum barrier
Skin temperature

Answer: C. The stratum corneum (outermost layer of epidermis) is a lipid-rich barrier that significantly limits transdermal drug penetration. Only lipophilic, small molecules (<500 Da) penetrate effectively. ---

A small population exhibits high frequency of "blue-skin" from one couple. This is an example of

Mutation
Heterozygote advantage
Sexual selection
Genetic drift
Natural selection

Answer: D. In small populations, rare traits can increase in frequency due to genetic drift, especially if they originate from a small number of founders. ---

Albinism is a hereditary disease due to absence of the skin pigment melanin. The allele for albinism is recessive to the allele for normal pigment. One person in 10,000 is albino. What is the frequency of the dominant allele?

0.1
0.01
0.09
0.99

Answer: B. If 1/10,000 is albino, then q² = 0.0001, so q = 0.01. Therefore, p = 1 - 0.01 = 0.99. ---

Skin

Skin

Skin

What our notes say

Study material on Skin

Images

Practice questions on Skin

During embryonic development, neural crest cells migrate to the skin. Some of these cells differentiate to produce melanin from tyrosine. These cells may be destroyed in a patchy distribution by an autoimmune process. What is the most likely condition to result from this autoimmune process?

Which of the following secretes defensive secretions to cause irritation on human skin?

A 22-year-old woman has a congenital anemia. She has required multiple transfusions of red blood cells for many years. She now has a darker bronze colour to her skin on physical examination. Which of the following microscopic findings would most likely present in her liver?

Which factor MOST limits drug absorption through the skin?

A small population exhibits high frequency of "blue-skin" from one couple. This is an example of

Albinism is a hereditary disease due to absence of the skin pigment melanin. The allele for albinism is recessive to the allele for normal pigment. One person in 10,000 is albino. What is the frequency of the dominant allele?

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