Lecture 13 (Exam 2) Flashcards
This is a single layer of ectodermal cells formed by the end of the first month.
Periderm
There is a three-layered epidermis formed by the end of the third month. The layers are…
Basal (germinative) layer
Intermediate layer
Superficial peridermal layer
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.
p63
miR-203
p63
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 ________.
Spinosum
Granulosum
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.
Integrins
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.
Keratohyalin granules
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.
Filaggrin
Postnatal layers of the epidermis during the 6th month, and peridermal cells all undergo ________.
Apoptosis
These are what form the loops, whorls, and arches of fingerprints.
Epidermal ridges
Epidermal ridges are closely related to the earlier appearance of ______ ______.
Volar pads
If a volar pad is high and round, epidermal ridges will form a _______.
Whorl
If a volar pad is low, epidermal ridges will form a _______.
Arch
If a volar pad is of intermediate height, epidermal ridges will form a _______.
Loop
Early formation of epidermal ridges is often associated with the formation of (ARCHES/WHORLS).
Whorls
Late formation of epidermal ridges is often associated with the formation of (ARCHES/WHORLS).
Arches
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.
Melanoblasts
This type of immigrant cell is derived from bone marrow and is an antigen-presenting cell.
Langerhans’ cells
This type of immigrant cell is from the neural crest and is a slow-adapting mechanoreceptor.
Merkel cells
Dermal cells for the dorsal surface of the body originate from mesenchyme from _________.
Dermatome
Dermal cells for the ventral and lateral surfaces of the body originate from mesenchyme from _______ ______ _______.
Lateral plate mesoderm
Dermal cells for the cranial and anterior neck originate from mesenchyme mostly from the ______ ______ ______.
Cranial neural crest
Ectodermal _____ signaling specifies the formation of dermal cells. Dermal cells express the dermal marker, ______.
Wnt
Dermo 1
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 _______ _______.
Glycogen
Hyaluronic acid
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.
Fibroblasts
In the developing dermis, the principle types of fibers secreted are ______ and ______ collagen, and _______ fibers.
Type I
Type III
Elastic
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.
Vascularized
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.
Sensory
The underlying ______ influences the development of the epidermis and especially of the epidermal derivatives. There is a reciprocal influence by the epidermis on the ______.
Dermis
Dermis
When ectoderm and mesenchyme are separated/alone, they (WILL/WILL NOT) differentiate any farther.
Will not
If abdominal ectoderm is combined with sole mesoderm, the abdominal ectoderm will differentiate into what?
Thickened skin typical of the sole
If sole ectoderm and scalp mesoderm are combined, the sole ectoderm will differentiate into what?
Scalp epidermis with hair
This type of induction, where one germ layer instructors another on how to differentiate is referred to as…
Instructive induction
Epidermal derivatives include…
Hair
Nails
Mammary glands
Development of the epidermal derivatives involves _______-_______ interactions and inductions.
Ectodermal-mesodermal
Hairs, nails, and mammary glands begin as epidermal downgrowths (ingrowths) into _________.
Mesenchyme
________ contributes to the hair follicle, hair shaft, sebaceous glands, nails, eponychium, hyponychium, and secretory and duct components of the mammary glands.
Ectoderm
________ contributes to the hair papilla, outer hair follicle, and arrector muscles.
Mesenchyme
In the induction of ectodermal placode (thickening), ______ causes the expression of ______ in the mesoderm.
Wnt-1
Wnt-11
In the induction of ectodermal placode (thickening), ______ and ______ from mesoderm cause ectoderm to express _______.
Wnt-11
FGF
Noggin
In the induction of ectodermal placode (thickening), ______ from mesoderm causes ectoderm to express ______.
Eda
Edar
In the induction of ectodermal placode (thickening), ______ and _______ block ______.
Edar
Noggin
BMP
In the induction of ectodermal placode (thickening), other ______ act through Beta-catenins.
Wnts
In the induction of ectodermal placode (thickening), in interfollicular zones _______ blocks Wnt, and ______ inhibits follicle development.
Dickkopf
BMP
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.
Shh
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.
Shh
Cyclin D1
Hox
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.
Proximally
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.
Eponychium
The thickened epidermis underlying the distal most part of the nail is called the ________, and it marks the border between dorsal and ventral skin.
Hyponychium
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.
Milk lines
Milk lines are marked by the expression of various ______ within the ectodermal cells.
Wnts
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 ______.
Neuregulin-3
Tbx-3
Mammary ductal epithelial downgrowths are associated with two types of mesoderm: _______ and ______.
Fibroblastic
Fatty
In the development of mammary glands, the early epithelial downgrowth secretes ______, which increases the sensitivity of the underlying mesenchyme cells to ______.
PTHrP (Parathyroid hormone-related hormone)
BMP-4
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.
Msx-2
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.
Testosterone
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.
Testicular feminization syndrome (TFM)
If a mammary bud contains TFM ectoderm and normal mesoderm with testosterone, will the phenotype be a male or female morphology?
Male
Remember, mesoderm (dermis) determines the ectoderm differentiation
If a mammary bud contains normal ectoderm and TFM mesoderm with testosterone, will the phenotype be a male or female morphology?
Female
If TFM is expressed in the (ECTODERM/MESODERM) the genetic defect will be expressed.
Mesoderm
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.
Estrogens
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.
Progesterone
Prolactin
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.
Prolactin
Anterior
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.
Oxytocin
Posterior
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.
Luteinizing hormone
Hypothalamus
