Lecture 13 (Exam 2)

Question 1

This is a single layer of ectodermal cells formed by the end of the first month.

Answer 1

Periderm

Question 2

There is a three-layered epidermis formed by the end of the third month. The layers are…

Answer 2

Basal (germinative) layer
Intermediate layer
Superficial peridermal layer

Question 3

Progression from a single-layered ectoderm to a stratified epithelium requires the activation of the transcription factor _____, possibly in response to signals from the underlying dermal mesenchyme. Subsequently, through the action of ______, ______ must be turned off for cells within the stratified epidermis to embark on their terminal differentiation program, which involves their leaving the cell cycle.

Answer 3

p63
miR-203
p63

Question 4

The multilayered epidermis undergoes mitosis in the basal (germinative) layer to give rise to the intermediate layer. The intermediate layer consists of the stratum _______ and stratum ________.

Answer 4

Spinosum

Granulosum

Question 5

For the cells in the stratum spinosum (intermediate layer) to differentiate from the basal layer, there is a loss of adhesiveness from the basal lamina underneath. These cellular properties can be explained by the loss of several ________, which attach the basal cells to the underlying basal lamina.

Answer 5

Integrins

Question 6

These begin to appear in the cytoplasm of the outer, post mitotic cells of the stratum spinosum and are prominent components of the stratum granulosum. They are composed of two types of protein aggregates, one histidine rich and one sulfur rich, closely associated with bundles of keratin filaments.

Answer 6

Keratohyalin granules

Question 7

As the cells move into the outer layer, the stratum corneum, they lose their nuclei and resemble flattened bags densely packed with keratin filaments. The cells of this layer are interconnected by the histidine-rich protein called ________, which is derived from one of the granular components of keratohyalin.

Answer 7

Filaggrin

Question 8

Postnatal layers of the epidermis during the 6th month, and peridermal cells all undergo ________.

Answer 8

Apoptosis

Question 9

These are what form the loops, whorls, and arches of fingerprints.

Answer 9

Epidermal ridges

Question 10

Epidermal ridges are closely related to the earlier appearance of ______ ______.

Answer 10

Volar pads

Question 11

If a volar pad is high and round, epidermal ridges will form a _______.

Answer 11

Whorl

Question 12

If a volar pad is low, epidermal ridges will form a _______.

Answer 12

Arch

Question 13

If a volar pad is of intermediate height, epidermal ridges will form a _______.

Answer 13

Loop

Question 14

Early formation of epidermal ridges is often associated with the formation of (ARCHES/WHORLS).

Answer 14

Whorls

Question 15

Late formation of epidermal ridges is often associated with the formation of (ARCHES/WHORLS).

Answer 15

Arches

Question 16

This type of immigrant cell is from the neural crest. It migrates into the dermis and then into the epidermis. It stains with HMB-45 and produces pigment by mid-pregnancy.

Answer 16

Melanoblasts

Question 17

This type of immigrant cell is derived from bone marrow and is an antigen-presenting cell.

Answer 17

Langerhans’ cells

Question 18

This type of immigrant cell is from the neural crest and is a slow-adapting mechanoreceptor.

Answer 18

Merkel cells

Question 19

Dermal cells for the dorsal surface of the body originate from mesenchyme from _________.

Answer 19

Dermatome

Question 20

Dermal cells for the ventral and lateral surfaces of the body originate from mesenchyme from _______ ______ _______.

Answer 20

Lateral plate mesoderm

Question 21

Dermal cells for the cranial and anterior neck originate from mesenchyme mostly from the ______ ______ ______.

Answer 21

Cranial neural crest

Question 22

Ectodermal _____ signaling specifies the formation of dermal cells. Dermal cells express the dermal marker, ______.

Answer 22

Wnt

Dermo 1

Question 23

The future dermis is initially represented by loosely aggregated mesenchymal cells that are highly interconnected by focal tight junctions on their cellular processes. These early dermal precursors secrete a watery intercellular matrix rich in ________ and _______ _______.

Answer 23

Glycogen

Hyaluronic acid

Question 24

Early in the third month, the developing dermis undergoes a transition from the highly cellular embryonic form to a state characterized by the differentiation of the mesenchymal cells into ________ and the formation of increasing amounts of a fibrous intercellular matrix.

Answer 24

Fibroblasts

Question 25

In the developing dermis, the principle types of fibers secreted are ______ and ______ collagen, and _______ fibers.

Answer 25

Type I Type III Elastic

Question 26

In the developing dermis, after the formation and secretions of fibroblasts and other fibers, the dermis becomes highly _________, with an early capillary network transformed into layers of larger vessels.

Answer 26

Vascularized

Question 27

Shortly after the 8th week, _______ nerves growing into the dermis and epidermis help complete the reflex arc and thus allow the fetus to respond to pressure and stroking.

Answer 27

Sensory

Question 28

The underlying ______ influences the development of the epidermis and especially of the epidermal derivatives. There is a reciprocal influence by the epidermis on the ______.

Answer 28

Dermis | Dermis

Question 29

When ectoderm and mesenchyme are separated/alone, they (WILL/WILL NOT) differentiate any farther.

Answer 29

Will not

Question 30

If abdominal ectoderm is combined with sole mesoderm, the abdominal ectoderm will differentiate into what?

Answer 30

Thickened skin typical of the sole

Question 31

If sole ectoderm and scalp mesoderm are combined, the sole ectoderm will differentiate into what?

Answer 31

Scalp epidermis with hair

Question 32

This type of induction, where one germ layer instructors another on how to differentiate is referred to as...

Answer 32

Instructive induction

Question 33

Epidermal derivatives include...

Answer 33

Hair Nails Mammary glands

Question 34

Development of the epidermal derivatives involves _______-_______ interactions and inductions.

Answer 34

Ectodermal-mesodermal

Question 35

Hairs, nails, and mammary glands begin as epidermal downgrowths (ingrowths) into _________.

Answer 35

Mesenchyme

Question 36

________ contributes to the hair follicle, hair shaft, sebaceous glands, nails, eponychium, hyponychium, and secretory and duct components of the mammary glands.

Answer 36

Ectoderm

Question 37

________ contributes to the hair papilla, outer hair follicle, and arrector muscles.

Answer 37

Mesenchyme

Question 38

In the induction of ectodermal placode (thickening), ______ causes the expression of ______ in the mesoderm.

Answer 38

Wnt-1 | Wnt-11

Question 39

In the induction of ectodermal placode (thickening), ______ and ______ from mesoderm cause ectoderm to express _______.

Answer 39

Wnt-11 FGF Noggin

Question 40

In the induction of ectodermal placode (thickening), ______ from mesoderm causes ectoderm to express ______.

Answer 40

Eda | Edar

Question 41

In the induction of ectodermal placode (thickening), ______ and _______ block ______.

Answer 41

Edar Noggin BMP

Question 42

In the induction of ectodermal placode (thickening), other ______ act through Beta-catenins.

Answer 42

Wnts

Question 43

In the induction of ectodermal placode (thickening), in interfollicular zones _______ blocks Wnt, and ______ inhibits follicle development.

Answer 43

Dickkopf | BMP

Question 44

In the induction of dermal papilla, there is an epidermal induction with the expression of ______ via the signaling pathway involving Edar receptor stimulates formation of dermal papilla below epidermal placode.

Answer 44

Shh

Question 45

In the induction of hair germ, this involves the second dermal induction. Various inducers from dermal papilla along with _____ and _____ in epidermal placode stimulate further downgrowth of proliferation of epidermal placode. The final differentiation of hair primordia involves ______ genes.

Answer 45

Shh Cyclin D1 Hox

Question 46

In the development of nails, in the 4th month the primary nail field overlies a mesenchymal nail bed and extends (DISTALLY/PROXIMALLY) as the proximal matrix.

Answer 46

Proximally

Question 47

Close to term, the nail has grown close to the end of the fingertip. Much of the nail is covered by a thin ________, most of which will eventually degenerate.

Answer 47

Eponychium

Question 48

The thickened epidermis underlying the distal most part of the nail is called the ________, and it marks the border between dorsal and ventral skin.

Answer 48

Hyponychium

Question 49

The first morphological evidence of mammary gland development is the appearance of two bands of ectodermal thickenings called ______ ______ (part of the wolffian ridge) running along the ventrolateral body walls in embryos of both genders at about 6 weeks.

Answer 49

Milk lines

Question 50

Milk lines are marked by the expression of various ______ within the ectodermal cells.

Answer 50

Wnts

Question 51

Individual mammary placodes form from aggregation and proliferation of ectodermal cells of the milk line under the inductive influence of the signaling molecule ________. Their dorsoventral location is marked by the expression of the transcription factor ______.

Answer 51

Neuregulin-3 | Tbx-3

Question 52

Mammary ductal epithelial downgrowths are associated with two types of mesoderm: _______ and ______.

Answer 52

Fibroblastic | Fatty

Question 53

In the development of mammary glands, the early epithelial downgrowth secretes ______, which increases the sensitivity of the underlying mesenchyme cells to ______.

Answer 53

PTHrP (Parathyroid hormone-related hormone) | BMP-4

Question 54

In the development of mammary glands, BMP-4 signals within the underlying mesenchyme have two principal effects. First, they stimulate further downgrowth of the mammary epithelial bud. Second, they stimulate the expression of the transcription factor ______, which inhibits the formation of hair follicles in the region of the nipple.

Answer 54

Msx-2

Question 55

In the presence of ________, male mammary glands undergo a rapid involution. However, in the absence of this, they will develop similar to a female morphology.

Answer 55

Testosterone

Question 56

This is a condition in which genetic male individuals lack testosterone. Despite having high levels of circulating testosterone, these individuals develop female phenotypes, including typical female breast development, because without receptors, the tissue cannot respond to the testosterone.

Answer 56

Testicular feminization syndrome (TFM)

Question 57

If a mammary bud contains TFM ectoderm and normal mesoderm with testosterone, will the phenotype be a male or female morphology?

Answer 57

Male ***Remember, mesoderm (dermis) determines the ectoderm differentiation***

Question 58

If a mammary bud contains normal ectoderm and TFM mesoderm with testosterone, will the phenotype be a male or female morphology?

Answer 58

Female

Question 59

If TFM is expressed in the (ECTODERM/MESODERM) the genetic defect will be expressed.

Answer 59

Mesoderm

Question 60

At the onset of puberty (in females), increasing levels of circulating ______, acting on a base of growth hormone and insulin like growth factor activity, stimulate the proliferation of the mammary ducts and enlargement of the pad of fatty tissue that underlie it.

Answer 60

Estrogens

Question 61

During pregnancy, increased amounts of ________, along with _______ and placental lactogen, stimulate the development of secretory alveoli at the ends of the branched ducts in mammary glands.

Answer 61

Progesterone | Prolactin

Question 62

In lactation, it is stimulated by _______ secretions from the _______ pituitary which cause the alveolar cells to synthesize milk proteins (casein and a-lactalbumin) and lipids.

Answer 62

Prolactin | Anterior

Question 63

In a rapid response to the suckling stimulus, the ejection of milk is triggered by the release of _______ by the _______ portion of the pituitary. This causes the contraction of myoepithelial cells, which surround the alveoli.

Answer 63

Oxytocin | Posterior

Question 64

Suckling also causes an inhibition of the release of _______ _______-releasing hormone by the ________ that results in the inhibition of ovulation and a natural form of birth control.

Answer 64

Luteinizing hormone | Hypothalamus