Week 11 - Limbs, Skin

"Which embryonic layers contribute to the formation of limbs?"

"Ectoderm and mesoderm."

"Which statement about limb development timing is true?"

"The upper limbs begin to develop before the lower limbs."

"By which week of development does osteogenesis of the long bones begin?"

"7th week."

"Which chromosomal aneuploidy syndrome is classically associated with polydactyly?"

"Trisomy 13."

"Which statement about rickets is FALSE?"

"Affected individuals rarely have other clinical manifestations."

"Name the limb defect also called lobster-claw deformity or forked hand associated with ectodermal dysplasia."

Ectrodactyly

All of the following mechanisms are necessary for normal limb development except:

Apoptosis

Inductive interactions and secretions of SHH

HOX gene expression

Cellular migration of sclerotome from somites

Cellular migration of sclerotome from somites

"Most critical period of limb development (high teratogen sensitivity)"

"Days 24 to 36."

"During which period of development do most visible changes occur?"

"The embryonic period (3–8 weeks)."

"Which listed condition does NOT typically result in neonatal death:

Congenital heart defects

Hypertrichosis

Ichthyosis

Renal agenesis

hypertrichosis

"Which congenital heart defect in the list is NOT cyanotic:

Tetralogy of Fallot

Transposition of the Great Arteries

Patent Ductus Arteriosus

Truncus Arteriosus

Patent Ductus Arteriosus

"Which syndrome with abnormal tooth development is autosomal dominant?"

Treacher Collins syndrome

Rickets

Pierre Robin

Amelogenesis Imperfecta

"Treacher Collins syndrome."

"Digit abnormality commonly associated with skeletal dysplasias especially achondroplasia"

Adactyly

Brachydactyly

Polydactyly

Syndactyly

Brachydactyly

"Which skeletal dysplasia is also known as brittle bone disease?"

Camptomelic dysplasia

Chondrodysplasia punctata

Achondroplasia

Osteogenesis imperfecta

"Osteogenesis imperfecta."

"Which are risk factors for limb anomalies”

Uncontrolled maternal diabetes

Thalidomide exposure during embryonic period

Chromosomal aneuploidy

All of the above are risk factors for limb anomalies

1. Uncontrolled maternal diabetes

2. Thalidomide exposure during embryonic period

3. Chromosomal aneuploidy

Limb reductions defects range in severity depending on what embryonic age there was disruption of limb formation. Amelia is the most severe. (T/F)

True

Hair follicles and glands are derived from the epidermis and grow down into the dermis. (T/F)

True

"Most cases of syndactyly involve bone (osseous) and fully formed digits: true or false?"

"False; most are soft tissue/cartilage only."

"Recurrence risk for developmental hip dysplasia is less than 1 percent: true or false?"

"False; recurrence can range from about 1–36 percent."

"Minor limb defects are relatively common and can often be surgically corrected: true or false?"

"True."

Your skin has both thick and thin components and both contain sweat glands, hair follicles, arrector muscles of hairs, and sebaceous glands. (T/F)

False; The thick skin contains sweat glands (i.e. palms of your hands or bottom of your feet). Thin skin contains hair follicles, muscles, and glands.

The secretory parts of the eccrine and apocrine sweat glands open into the skin and begin to function shortly after birth. (T/F)

"False; eccrine open to skin surface at birth.

The eccrine sweat glands do open into the surface of the skin and begin to function shortly after birth (gotta stay cool!). The apocrine sweat glands, however, open into the canals of the hair follicles (not the surface of the skin) and secretions don't begin to function until around puberty.

"Do both males and females have lactiferous ducts?" (T/F)

"True."

"Can delayed tooth eruption be a sign of hypothyroidism?" (T/F)

"True."

Babies that are born very prematurely (i.e. before 26 weeks) are not at increased risk for neurological or developmental problems, however they may have fingernails that have not yet reached the tips of their digits and may have cardiovascular complications, such as patent ductus arteriosus. (T/F)

"False; they have a high risk for neurological and developmental issues."

"Explain incomplete penetrance in genetics."

"Having the disease-causing genotype but not expressing the phenotype; not all carriers of the mutation show the trait."

"Embryonic tissue origins of skin layers: epidermis vs dermis"

"Epidermis from surface ectoderm; dermis from mesenchyme (mesoderm)."

"Define vernix and lanugo."

"Vernix: cheesy fetal coating from periderm cells and sebaceous secretions; Lanugo: fine fetal body hair."

"Genetics and features of oculocutaneous albinism"

"Autosomal recessive; melanin deficiency due to tyrosinase defect; clinical features include fair skin and eye problems such as red eyes or ophthalmic issues."

"What is the hardest tissue in the human body?"

"Enamel."

"Poland syndrome key feature and associated anomalies"

Condition characterized by absence of the pectoralis major muscle that results in hypoplastic fused rubs, unilateral absence of breast, nipple, areola, hemivertebrae, syndactyly, brachydactyly, and in some cases dextrocardia.

"Name the three body cavities derived from the intraembryonic coelom in the 2nd month."

peritoneal, plural, pericardial

"Two fruity ultrasound signs linked to neural tube or CNS defects"

"Banana sign and lemon sign."

"What is a cystic hygroma and what is it associated with?"

"A lymphatic malformation associated with increased risk of chromosomal aneuploidy and poor pregnancy outcome."

"Potential fetal consequence of primary rubella infection"

"Cataracts (also CHD and hearing loss in classic triad)."

"Potential fetal consequence of tetracycline exposure"

"Tooth staining."

"Potential fetal consequence of high maternal blood sugar levels"

"Congenital heart defects (among other anomalies such as caudal regression and NTDs)."

"Potential fetal consequence of 1st-trimester thalidomide exposure"

"Limb malformations."

"Potential fetal consequence of primary Zika virus infection"

"Microcephaly."

A type of lower limb defect known technically as congenital vertical talus is also a feature of trisomy 18 =

rocker bottom foot

"Upper limb defect caused by failure of central digital rays to form"

"Ectrodactyly."

The most common musculoskeletal deformation, also associated with some neural tube defects.

congenital clubfoot

"Condition with hemifacial port-wine stain and leptomeningeal angioma causing seizures" (stain + angioma causing seizures)

"Sturge–Weber syndrome."

"Term for enlargement of male breast tissue often seen in Klinefelter syndrome"

gynecomastia

"Karyotype for Klinefelter syndrome"

47, XXY

"Term describing supernumerary nipples"

"Polythelia."

"Soft marker characterized by dilated renal pelvis on prenatal ultrasound seen in ~25 percent of Down syndrome fetuses"

pyelectasis