Development of Integument Test II

Question 1

Describe formation of a multiple layered epidermis including the derivatives from intermediate layer.

Answer 1

Begins with the periderm a single layer of ectodermal cells formed by the end of the first month. P63 is activated and it causes differentiation into a three layered epidermis by the end of the third month.

Intermediate layer forms when p63 is inactivated due to miR-203. It eventually divides into stratum spinosum and stratum granulosum

Question 2

What role does apoptosis play in epidermal development.

Answer 2

Postnatal layers of epidermis form during the sixth month the peridermal cells undergo apoptosis.

Question 3

Relate pattern of epidermal ridges to morphology of volar pads and timing of ridge formation.

Answer 3

Volar pads are where ridges and creases of finger prints appear. Epidermal ridge formation is associated with the appearance of volar pads.

Question 4

What are the major groups of immigrant cells, where are they derived from and list basic functions.

Answer 4

Melanoblasts: from the neural crest, migrate to dermis and then epidermis, produce pigment by mid pregnancy

Langerhans’ cells: derived from bone marrow, APC in the dermis

Merkel cells: from neural crest, slow adapting mechanoereceptors

Question 5

Describe source of dermal cells on the dorsal surface of the body, limbs, and face.

Answer 5

On the dorsal surface of the body dermal cells original from mesenchyme from dermatome.

Limb from lateral plate mesoderm

Face and anterior neck from neural crest

Question 6

Describe the signaling pathways leading to the formation of dermis on various surfaces of the body.

Answer 6

Ectodermal Wnt signaling acts through B-Catenin pathway and specifies the dermomyotomal cells and mesenchymal cells of ventral somatopleure to become dermis. They now express Dermo1, a dermis marker.

Question 7

Describe how recombination experiments between mesoderm and ectoderm demonstrate instructive induction?

Answer 7

Referred to Instructive Induction
If ectoderm and mesenchyme are separated no differentiation occurs.

If abdominal ectoderm and sole mesoderm are put together the abdominal ectoderm is thickened and sole like.

Sole ectoderm and scalp mesoderm are combined and ecoderm differentiates as scalp epidermis with hair.

Question 8

List commonalities in development of epidermal derivatives.

Answer 8

Hair, nails, mammary glands.
Development of these involves ectodermal and mesodermal interactions and inductions, all begin as epidermal downgrowths into mesenchyme, ectoderm contributes to hair follicle, sebaceous glands, nails, and duct components of mammary glands. Dermis contributes to CT support of these.

Question 9

Describe developmental pathway for hair development.

ASK DR. A

Answer 9

Dermal induction occurs and Wnt-11 and FGF from mesoderm cause the ectoderm to express Noggin. Eda from mesoderm caues ectoderm to express Edar. Edar and Noggin in ectoderm block BMP. Other Wnts act through B-catenins. In the interfollicular zones Dickkopf blocks Wnt and BMP inhibits follicle development.

Epidermal induction occurs and expresses Shh via signaling path involving Edar receptor which stimulares formation of dermal papilla.

Dermal induction two occurs and Shh and cyclin D1 in epidermal placode stimulate further downgrowth of proliferation and final differentiation of hair involves Hox

Question 10

Describe adult hair cycle stage anagen.

Answer 10

Growth phase

Question 11

Describe adult hair cycle stage catagen.

Answer 11

Follicle regresses and growth stops

Question 12

Describe adult hair cycle stage telogen.

Answer 12

Resting stage

Question 13

Describe adult hair cycle stage exogen.

Answer 13

Shedding of hair occurs in this stage when next anagen stage begins to push it out

Question 14

When does the appearance of keratohyalin granules occur?

Answer 14

Stratum spinosum

Question 15

What differentiates mesenchymal cells into dermal cells?

Answer 15

Wnt

Question 16

What is responsible for blocking hair cell development?

Answer 16

BMP

Question 17

Inductive interactions in hair formation?

Answer 17

Specification of dermis, first dermal induction, epidermal induction, second dermal induction

Question 18

What are milk lines and how are they related to Wnt expression?

Answer 18

Most mammalian species have multiple pairs of mammary glands, not humans. The milk lines are where mammary glands can form running along body wall chest to abdomen.

Question 19

What role do Wnts neurogluin-3 Tbx-3 PTH, BMP-4 and Msx-2 play in mammary gland development?

Answer 19

Milk lines are marked by expression of Wnt
Neuregulin-3 causes proliferation of ectodermal cells of milk line. Tbx-3 marks the dorsoventral location.
Early epithelial downgrowth secretes PTH which increases sensitivity of mesenchymal cells to BMP-4.
BMP-4 signals for downgrowth of epithelial bud and expression of Msx-2 which inhibits hair follicle formation.

Question 20

What is testicular feminization and what is its relation to mammary gland development.

Answer 20

Female phenotype but genetic male. Has ammenoreah and when remove gonads it shows immature testis not ovaries. In a male the mammary bud regresses and in a female it forms duct system. Testosterone exposure to mammary bud causes male like mammary glands.

Question 21

Nails.

Answer 21

Epidermal thickenings at the end of the third month mark beginning of nail development.
Proiferation of cells into proximal part of nail field results in proximal matrix that gives rise to nail plate to then cover nail bed.

Question 22

Describe hormones in lactation.

Answer 22

Prolactin is released causing milk and fat synthesis and oxytocin being released causing milk letdown both released from anterior pituitary in response to suckling.

Question 23

Describe hormones in lactation.

Answer 23

Prolactin is released causing milk and fat synthesis and oxytocin being released causing milk letdown both released from anterior pituitary in response to suckling.

Question 24

Which of following are characterized as primary errors of morphogenesis and usually multifactorial involving number of ethological agents including genetic and environements?
A.Malformations
B.disruptions
C.syndromes
D.sequences

Answer 24

Malformations
Characterized as primary errors is key

Syndromes are interruption in normal sequence

Question 25

What refers to accumulation of edema fluid in fetus during intrauterine growth and was considered most commonly caused by hemolytic anemia by blood group incompatibility?
A. eclampsia
b. Neonatal respiratory distress syndrome
c. hyaline membrane syndrome
d. hydrops

Answer 25

Hydrops

Question 26

Folic acid deficiency is believed to be a major cause of what malformation class?

a. trisomies
b. neural tube defects
c. ambiguous genitalia
d. polyploidy

Answer 26

Neural tube defects

Question 27

Rh negative womans second son severely jaundiced what describes first child?

Answer 27

Rh positive

Question 28

Which of these anomalies can be attributed to disturbance is tissue reabsoprtion?

a. pelvic kidney
b. cleft lip
c. anal atresia
d. renal agenesis
e. amputated digit in utero

Answer 28

Anal atresia** anal column begins to form but gets reabsobed

cleft lip is lack of fusion
pelvic kidney is inability to migrate
renal agenesis is lack of kidneys

Question 29

Which of following is responsible for largest percent of congenital malformations?

Answer 29

Unknown factors

Question 30

Define and distinguish between cytodiffertiation and histiogenesis?

Answer 30

Cyto: cells that make up a tissue undergo increasing specialization through this process
Histio: Various types of cells develop in concert to form specific tissues

Question 31

Ventral and lateral surface of dermal cells comes from where?

Answer 31

Ventral and lateral surfaces of dermis comes from lateral plate mesoderm.

Question 32

Where do dermal cells come from in the cranial and anterior neck?

Answer 32

Cranial and anterior neck mesenchyme mostly from cranial neural crest

Question 33

Where do dermal cells that form the trunk dermis come from?

Answer 33

Trunk dermis comes from somitic dermatomes Wnt signaling responsible for this and produces Dermo1

Question 34

Pathway for hair formation? ASK DR. A

Answer 34

Thickening of ectoderm to form epidermal placodes occurs. FGF and Wnt-11 are expressed and inactivate BMP-4. This stimulates acrivation of other Wnt’s in ectoderm to form epidermal placode and act through Edar.

Question 35

Testicular feminization syndrome?

Answer 35

Genetic males lack testosterone receptors.

Even though they have high levels of circulating testosterone they develop female phenotypes.