Medical Genetics Quiz 3

Front 1

what is the chromosome number of gametes

Back 1

1N, haploid

Front 2

What is the function of the acrosome

Back 2

a compartment on the head of the sperm that carries the enzymes necessary to penetrate the zona pellucida

Front 3

Before fertilization, the oocyte is arrested at what stage of the cell cycle?

Back 3

Metaphase II

Front 4

Compare the genetic "varieties" of spermatozoons and oocytes

Back 4

sperm= x or y
oocytes x only

Front 5

Describe the morphological abnormalities associated with male gametes

Back 5

-many possible abnormalities including body and tail shape/ #
-up to 10% of sperm in every ejaculate are abnormal
-if >20% are abnormal, may have fertility problems

Front 6

What genetically related issues may lead to abnormal gametes

Back 6

-Chrososomal abnormalities such as nondisjunction, translocations, and deletions
-fresh mutations of single genes

Front 7

Where is the oocyte fertilized

Back 7

the outer 1/3 of the oviduct aka uternine tube aka fallopian tube

Front 8

Describe the journey of the sperm thorugh the male reproductive tract

Back 8

-move from testis to epididymis
-mature in epididymis (become motile, increase metabolism, changes in membrane)
-stored at based of epididymis until ejaculation when thye pass through the rest of the male duct system

Front 9

What "barriers" do sperm face once they enter the female reproductive tract

Back 9

1. acidity of vaginal fluid
2. cervical mucous
3. enter the wrong oviduct (only 1 has an oocyte in it)
4. rarely women can have antibodies to sperm

Front 10

Describe the layers of the oocyte

Back 10

-outermost layer is loosened follicle aka cumulus cells
-internal to the cumulus cells is the zona pellucida
-between the zona pellucida and the oocyte cell membrane is the perivitelline space

Front 11

Where is the oocyte released

Back 11

into the abdominal caivity
not the oviduct although it is quickly drawn in by aciton of the fimbriae and the cumulus cells

Front 12

Describe the path of the oocyte in the female reproducive tract

Back 12

The oocyte is released from the ovarian follicle into the abdominal cavity where it is swepty inot the oviduct by the fimbriae. It is drawn deeper into the oviduct by the peristaltic contractions of the muscular wall of the oviduct.

Front 13

What are the 7 steps of fertilization

Back 13

Capacitation, Binding of Sperm to ZP, acrosome reaction, penetration of ZP, fusion of cell membranes, oocyte activation, zygote formation
hint: Copulation Brings a pleasurable feeling oh zipee!!

Front 14

Describe the capacitation step of fertilization

Back 14

-final step in sperm maturation
-occurs when sperm is detained in isthmus
-changes occur that allow for the acrosome reaction, metabolic activity increases, become hypermotile
-able to respond to oocyte chemoattractant

Front 15

Describe the binding of the sperm to the zona pellucida (step 2 of fertilization)
What receptors are involved?
What features must the sperm have to suceed?

Back 15

-receptor mediated event, sperm SED1 binds to receptors on ZP proteins ZP2 and ZP3
-sperm must be acrosome intact

Front 16

Describe the acrosome reaction, the 3rd step in fertilization

Back 16

-occurs after sperm bind to ZP, mediated by ZP2, ZP3 and SED1
-Acrosome enzymes are exposed (involves Ca mediated signaling pathways)
-secondary binding reaction to ZP2 holds sperm to ZP while it penetrates

Front 17

Describe the penetration of the zona pellucida, the 4th step of fertilization

Back 17

-acrosome enzymes (acrosin) hydrolyze the ZP glycoproteins allowing the sperm to pass through
-movement of sperm tail facilitates penetration

Front 18

T/F all sperm that are capable of reaching the oocyte have the potential to fertilize

Back 18

false, only acrosome intact sperm can effectivley bind to and penetrate the ZP

Front 19

Describe the fusion of sperm and oocyte membranes, the 5th step of fertilization

Back 19

After the sperm penetrates the ZP, it enters the perivitelline space where it has access to the oocyte cell membrane. ADAM2 (FertilinB) on the sperm binds to an integrin on the oocyte (with help form CD9)
-after fusion, the head, mid, and tail (usually) eneter the oocyte cytoplams

Front 20

What proteins are necessary to facilitate sperm and oocyte membrane fusion

Back 20

sperm-ADAM2 (FertilinB)
oocyte-integrin (a6b1) and CD9
note only acrosome reacted sperm can properly bind oocyte membrane

Front 21

What are the steps in oocyte activation?

Back 21

1. Hyperpolarization
2. Cortical reaction
3. Zona Reaction
4.Completion of Meiosis
5. Pronuclei
hint: Holy Cow, Zygotes Make People!

Front 22

describe the trasient hyperpolarization associated with oocyte activation
How is it activated? What is the purpose?

Back 22

-triggered by sperm and oocyte membrane fusion
-wave of intracellular Ca passes through oocyte
-blocks polyspermy

Front 23

Describe the cortical reaction, a step in oocyte activation

Back 23

Intracellular Ca oscillations stimulate fusion of cortical granules whith oocyte plasma membrane, leads to hydrolytic and oxidative enzymes released into perivitelline space

Front 24

Describe the zona reaction, a step in oocyte activation.
What is the purpose?

Back 24

The corical granule enzymes (released during the previous cortical reaction) enter the ZP and cross link the glycoproteins
-this prevents further sperm binding and penetration because it alters the configuration of sperm receptor molecules (located on ZP2 and 3)

Front 25

When does the oocyte complete meiosis? What triggers this reaction?

Back 25

-meiosis is completed during oocyte activation
-Ca ions deactivate a meitoic inhibited
-2nd polar body is extruded and transient female pronucleus forms
-note that meiosis occurs afterm the sperm enters but before the formation of the pronuclei (it must be this way because otherwise the maternal genome would be "tied up")

Front 26

Describe how the male and female pronuclei arise

Back 26

female-after completion of 2nd meiotic division which is trigger by Ca ions
male- chromatin condenses after the sperm head enters the oocyte cytoplasm

Front 27

Describe the zygote formation step of oocyte acivation

Back 27

-male and female pronuclei approach each other and nuclear membranes break down
-chromosomes form a metaphase plate
-zygote now begins first mitotic division

Front 28

When is the sex of an zygote determined

Back 28

upon fertilzation when the maternal and paternal genomes fuse

Front 29

Why doesn't parthenogenesis occur in humans

Back 29

male and female haploid genomes are not equivalent as a result of genomic imprinting

Front 30

Define hydatidiform mole (molar pregnancy)

Back 30

occurs when two paternal fuse in an oocyte forming an intrauterine tumor
the genome is not viable because genomic imprinting renders male and female haploid genomes unique

Front 31

how long are the gametes viable onces they reach the oviduct (site of fertilization)

Back 31

sperm-3-5 days
oocyte-24 hrs

Front 32

List the basic steps of invitron fertilization and embryo transfer (IVF-ET)

Back 32

stimulate ovulation=>collect oocytes=> obtain sperm=> capacitate sperm=> incubate gametes=> develop embryos to blastocysts=> implant blastocysts in uterus

Front 33

What is the weakest link of IVF-ET

Back 33

embryo transfer

Front 34

What is ICSI and when is it indicated

Back 34

ICSI-intracytplasmic sperm injection, spermatozoon is injected directly into the cytoplasm of an oocyte, indicated for men experiencing infertility due to insufficient sperm count or abnormal sperm

Front 35

What organ systems are affected by CF

Back 35

upper and lower respiratory tract, pancrease, sweat glands, reproductive tract, hepatobillary

Front 36

What is the "classic triad" of CF

Back 36

-recurrent sinopulmonary disease
-elevated sweat chloride
-pancreatic insufficiency

Front 37

In what ethnic group is CF most commont

Back 37

whites

Front 38

Where is the CF gene located

Back 38

Chromosome 7

Front 39

Which mutation accounts for the majority of CF cases

Back 39

ΔF508

Front 40

What is the role of the CFTR protein product

Back 40

muti-protein complex that controls the conductance of chloride from inside to outside of cell, can also regulate other ion channels

Front 41

T/F knowing the mutation in the CF gene can predict a patients lung function

Back 41

False, lung function cannot be predicted based on which mutation a pt has but pancreatic function can

Front 42

Which bacterial are most often indicated in CF related infections

Back 42

kids-Staph, H. influenzae
Adults-Pseudomonas areuginosa

Front 43

How does retention of airway secretions lead to infections in CF pts

Back 43

Retention of the secretions changes the pericillary space from aerobic to anaerobic which changes the Pseudomonas from planktonic to biofilm

Front 44

Why should adult CF patients be monitored closely for Pseudomonas aeruginosa colonization

Back 44

It is very important to avoid develpment of P. aeruginosa biofilms because these are resistant to tx and life thretening. If colonization is caught early, the pt can be treated with antibiotics

Front 45

What are some tools used to Dx CF

Back 45

-clinical sxs
-Family Hx
-sweat chloride
-genotype
-nasal potential difference
-newborn screening

Front 46

what problems might CF pts have with their livers

Back 46

-plugging leading to obstruction and cirrhosis
-elevated liver fxn tests
-portal hypertension
-also abnormal mucus in gall bladder leading to cholelithiasis

Front 47

What problmes might CF pts have with their pancrease

Back 47

-plugging of pancreatic ducts leading to loss of exocrine function
-autodigestion of pancrease leading to recurrent pancreatitis
-CF related diabetes

Front 48

What drugs may be used in treating CF

Back 48

-antibiotics to combat infections and delay colonization
-mucolytics
-anti-inflammatory agents
-airway surface fluid restoration/ hypertonic saline

Front 49

what are the three primary germ layers of the embryo

Back 49

ectoderm, endoderm, mesoderm
note the early embryo has only epithelium and mesenchyme

Front 50

describe the characteristics of an epithelial cell

Back 50

-covers surfaces and lines cavities of body
-continuous layer of cells held together by tight junctions
-cells are polarized (apical and basal surfaces)

Front 51

define the embryonic period

Back 51

weeks 1-8

Front 52

define the fetal period

Back 52

weeks 9-38

Front 53

What significant events occur in the embryonic period

Back 53

-blastocyst formation and implantation
-formation of 3 layer embryo
-axis of symmetry, segmentation, and folding
-limb, trunk, head, and organ system formation

Front 54

What is the difference between gestational age and fertilization age

Back 54

Fertilizaiton age begins at fertilization and is the true timing of embryo develpment. Gestation age begins with the date of the last menstural peroid, it is usually 2 weeks ahead of fertilzation age

Front 55

Describe stage 1 of clevage. What happens? What are some observable features? Where does this occur? Is the zona pellucida present?

Back 55

stage 1= secondary oocyte to zygote, unicellular, occurs in oviduct, zp is present

Front 56

Describe stage 2 of clevage. What happens? What are some observable features? Where does this occur? Is the zona pellucida present?

Back 56

stage 2= 2-16 cells, morula which is multicellular but has no cavity, occurs in oviduct, zp is present

Front 57

Describe stage 3 of clevage. What happens? What are some observable features? Where does this occur? Is the zona pellucida present?

Back 57

stage 3= morula to blastocyst, cavity becomes present but blastocyst is not yet attached, occurs in the uterus, ZP may or may not be present

Front 58

Describe stage 4 of clevage. What happens? What are some observable features? Where does this occur? Is the zona pellucida present?

Back 58

Stage 4= blastocyst, attached to uterus, ZP is hatched

Front 59

What is unique about the cell divisions during cleavage

Back 59

-rapid but controlled, no G1 or G2
-cell divisons are asynchronous
-no cell growth occurs between divisions because it is restricted by ZP
-ratio of cytoplasm to nucleus changes from 600:1 to 3-6:1

Front 60

When is the embryonic genome activated

Back 60

-the first cell division is controlled by a maternal program written during oogenesis
-embryo genome is activated at the 2-4 cell stage
-paternal genes are now expressed and proteins encoded in activated embryo genome direct clevage and blastocyst formation

Front 61

Which genes direct the first cell division? Clevage? Blastocyst formation?

Back 61

-first cell division is activated by maternal genome
-embryo genome is activated at 2-4 cell stage, directs clevage and blastocyst formation

Front 62

When does the blastocyst forms

Back 62

day 4/5

Front 63

Describe the morphological features of the blastocyst

Back 63

-between the 8-16 cell stage
-cavity formation causes the ICM to be located on one side of a fluid filled vesicle lined by trophoblast cells
-capable of implantation

Front 64

what type of tissue is the trophoblast? What genes regulate its development

Back 64

Trophoblast is true epithelium, it forms only extraembryonic tissue, development is controlled by expression of paternally derived genes (imprinting)

Front 65

Describe the remodeling of the inner cell mass

Back 65

-initially non polarized
-becomes bilaminar disk
-lower disk=hypoblast, forms extraembryonic tissue
-upper disk= epiblast, forms embryo+ some extraembryonic tissue
-formation of the bilaminar disk estabilishes the first axis of polarity creating a dorsal (upper surface of epiblast) and ventral (lower surface) side

Front 66

What types of tissues will from from the epiblast and hypoblasts, the two sections of the bilaminar disks formed during the blastocyst stage

Back 66

epiblast-upper disk, embryo+ extraembryonic tissue
hypoblast- lower disk, extraembryonic tissue

Front 67

Describe the hatching from the zona pellucida
when? what purpose

Back 67

-hatching occurs during the blastocyst stage around days 4 or 5
-hatching allows a small increase in the size of teh embryo and facilliates implantation

Front 68

What is the purpose of the zona pellucida

Back 68

-sperm binding site
-keeps blastomeres together
-immunological barrier
-prevents premature implantation

Front 69

Describe the concept of regulation and explain how it related to embryonic clevage

Back 69

Regulation=the ability of an embryo or organ primordia (field) to produce a normal embryo/structure when parts have been removed or added.Embryos at the clevage statge exhibit the potential for regulation however this ability decreases with increasing age of development.
Note that regulation is also the basis of chimeric/ mosaic embryos

Front 70

Describe the change in potenc as the embryo goes from the 0-8 cell stage to after the 16 cell stage

Back 70

0-8 cell blastomeres are totipotent, they can make any tissues including both embryonic and extraembryonic. Once a blastomere differentiates into the trophoblast and ICM, the cells become pluripotent; the trphoblast makes only extraembryonic tissues and the ICM can make any of the 3 germ layers

Front 71

List some factors that can mediate the terminal differentiation of a cell during the clevage process

Back 71

cell position, number of cell divisions, distribution of cytoplasmic determinates, cell-cell interactions

Front 72

Describe the concept of patterning as it relates to embryonic clevage

Back 72

recognizable, ordered spatial arrangement occuring at serveral levels including genes, cells, and tissues. Often occurs along a particular axis or set of axes in the embryo

Front 73

Describe the difference between the origin of mono and di zygotic twins

Back 73

monozygotic-result from blastomere/ ICM separation
dizygotic- result from a double ovulation and fertilization

Front 74

When does implantation occur

Back 74

days 5-12, bridges weeks 1 and 2

Front 75

What two events must be syncrhonized in order for implantation to occur? What hormones influence this process?

Back 75

Develpoment of the embryo into a free blastocyst must be syncrhonized with the secretory phase of the menstural cycle so that both the embryo and uterus are ready to interact. The implantation process is influenced primarily by estrogen and progesterone

Front 76

What are the two phases of implantation

Back 76

1. Attachment of the blastocyst to the uterine endometrium
2.embedment of the blastocyst within the compact latyer of the endometrium (decidual rxn)

Front 77

What structure of the blastocyst participates in the attachement phase of implantation

Back 77

the embryonic pole

Front 78

What reaction does attachemnt of the blastocyst to the uterine wall trigger? (attachment is a receptor mediated event)

Back 78

Attachment triggers the dedcidual reaction leading to the maternal recognition of pregnancy. The reaction provides a solid mass of cells into which the embryo can implant and transforms the outer 1/3 of teh endometrium into the compact layer

Front 79

What is the decidual reaction

Back 79

Triggered by attachment of the embryo to the uterine wall leading to the maternal recognition of pregnancy. The reaction provides a solid mass of cells into which the embryo can implant and transforms the outer 1/3 of the endometrium into the compact layer
(endrometrium thickens, stromla cells hypertrophy, increased endometrial blood flow)

Front 80

Describe the cytodifferntiation of the trophoblast that occurs as a result of embryo attachment to the endrometrium

Back 80

Contact with the endometrium triggers the trophoblast to differentiate into the syncytiotrophoblast and the cytotrophoblast. The syn will go on to mediate the invasion of the endometrium and absorbtion of dedicual cell nutrients. The cyto will retain its epithelial nature and become mitotically active

Front 81

After the blastocyst attaches to the endometrium, the trophoblast differentiates into the syncytiotrophoblast and the cytotrophoblast. What is the role of the syncytiotrophoblast

Back 81

-multinucleated cytoplasmic mass with no observable intercellular bounderies
-directs the enzyme mediated controlled invasion into the endrometrium
-has microvilli that absorb nutrients from lysed decidual cells and eroded endometrial glands/ blood vessels

Front 82

After the blastocyst attaches to the endometrium, the trophoblast differentiates into the syncytiotrophoblast and the cytotrophoblast. What is the role of the cytotrophoblast

Back 82

-retains epithelial nature
-becomes activley mitotic after contact with endometrium
-later differentiates into teh intermediate trophoblast which anchors the placenta to the maternal endometrium

Front 83

What are lacunae? What do they do?

Back 83

-spaces within the synctiotrophoblast
-eroded endometrium vessels and glands empty their contents into lacunae
-establish the primordium of the uteroplacental circulation

Front 84

By what day is the embryo completely embeded within the uterine endometrium

Back 84

10-12

Front 85

Where does normal implantation occur

Back 85

upper middle "triangle" of the uterus

Front 86

An embryo that implants too close to the cervix may lead to...

Back 86

palcenta previa, which may lead to premature placenta detachment

Front 87

Where does extrauterine pregnancy usually occur? What are the sxs? What might cause it? What are the outcomes?

Back 87

-usually occurs in the outer 1/2 of the oviduct
-sxs include spotty bleeding and acute, severe abdominal pain at 2.5 months
-caused by factors that prevent or slow the passage of the zygote to the uterine cavity (tubal or paratubal infection, altered motility, premature hatching of ZP)
-ectpoic pregnancy is rarely compatible with a sucessfully pregnancy and is life threatening for the mother,

Front 88

Spnataneous abortion (miscarriage) ends about 50% of all preganancies in the first 3 weeks of development. What are some possible causes?

Back 88

-homozygous lethal genes
-chromosomal abonormalities
-problems with corpus luteum

Front 89

During implantation, the embryo becomes bilaminar. What new tissues are formed and where do they come from?

Back 89

1. Amnion-comes from the epiblast
2. Yolk sak-formed from 2 waves of migrating cells from the hypoblast
3. extraembryonic mesoblast or mesoderm-unsure origin (maybe hypoblast, caudal epiblast, trophoblast),
4. Chorion once the EEM joins with the trophoblast, the group is known as the chorion
5. Body stalk-condensation of EEM

Front 90

Describe the formation and purpose of the amnion

Back 90

-forms during implantation on day 7-8 or 9
-extraembryonic membrane that will eventually surround the embryo
-formed from the epiblast
-holds fluid that facilitates symmetrical growth, lung development, homeostasis, movement, and temperature regulation

Front 91

Describe the formation and purpose of the yolk sac

Back 91

-days 8-13
-formed from hypoblast by 2 waves of migrating cells
-Blastocyst=>ICM=>hypoblast=>yolk sac
-extraembryonic membrane that metabolizes and transports nutrients from the trophobast to the embryo
-site of primordial germ cell segregation

Front 92

Describe the formation and purpose of the extraembryonic mesoderm EEM

Back 92

-days 9-12
-origin uncertain
-take form of mesenchyme rather than epithelium
-this tissue eventually beomes the chorion and the body stalk

Front 93

Describe the properties of mesenchyme cells

Back 93

-nonpolarized, free cell derivative of an embryonic epithelium which is often mobile

Front 94

Describe what must occur for epithelial cells to transform into mesenchyme cells

Back 94

-loss of polarity and cell shape
-detach from each other by downregulation of CAMs
-extend processes to bind to Extracellular matrix
-Up regulate substrate Adhesion molecules aka SAMs
summary ↑SAMs ↓CAMs and polarity

Front 95

What is a the chorion and how does it develop

Back 95

chorion-membrane of embryo
-term describing the association of the trophoblast with the extraembryonic mesoderm

Front 96

What is the body stalk and how does it develop

Back 96

The body stalk is a condensation of EEM at the posterior end of the embryo that suspends it within the chorionic cavity
-connects the embryo with the chorion and becomes the umbilical cord
-umbilical vessels will develop within the body stalk

Front 97

What are the major events occuring in week 3 of development

Back 97

-trilaminar disk
-formation of primary germ layers
-beginning or organogenesis
Hint: 3rd week=TRI laminar

Front 98

Which segement of the ICM contains all of the cells taht will form the embryo

Back 98

epiblast

Front 99

What is the primitive streak

Back 99

-transient midline thickening of the caudal epiblast due to converging of epiblast cells
-site of epithelial mesenchymal transformation
-creates a cranial-caudal axis because the streak always forms at what will be the caudal end
-changes shape from round to oval

Front 100

What morphological change occurs in the embryo as a result of the prmitive streak

Back 100

change round round to oval as a result of differential growth about the cranial-caudal axis created by the primitive streak

Front 101

where does the primitive node appear and what is its purpose?

Back 101

-appears on day 16 at the cranial end of the primitive streak
-functions as an inducer for the development of additiona structures
-site of epithelial-mesenchymal transformation

Front 102

Describe the reression of the primitive streak

Back 102

-streak becomes restricted to an elevated area at the caudal end of the embryo called the tailbud (caudal eminnece)
-normally the streak disappears at day 26

Front 103

What are teratomas and how do they relate to early development

Back 103

-neoplasm of more than one cell type unrealted to the structure to which it is attached
-can form from persistent primitive streak tissue
-usually sacrococcygeal, 4x more common in females

Front 104

There are two "waves" of mesenchyme cells that ingress through the primitive streak. What is that fate of each of these groups

Back 104

1st group-definitive endoderm, pass through streak at primitive node, spread out as a layer of epithelial cells that displaces the hypoblast and forms a roof for the yolk sac
-2nd wave- intraembryonic mesoblast, layer between endoderm and the epiblast

Front 105

When does the notochord form

Back 105

days 16-22

Front 106

What is the origin of the notochord

Back 106

group of cells that ingress at the primitive node and migrate cranially in the midline of the embryo

Front 107

Describe the steps involved in formation of the notochordal process. What becomes of it?

Back 107

1.Group of cells ingresses at the primitive node and migrates cranially
2. Notochordal process aquires a lumen and then fuses with the endoderm
3. The lumen becomes the neurenteric canal, a temporary communication between the amniotic cavity and the secondary yolk sac
4. the roof of the notochordal process becomes the notochoral plate
5.The plate infolds on itself to become the definitive notochord

Front 108

Gastrulation results in the formation of 3 primary germ layers (ectoderm, mesoder, and endoderm). The generation of new spatial relationshiops between embryonic tissues and cell groups sets up inductive tissue interactions between cell groups located in the 3 germ layers. What are the components of an inductive interaction?

Back 108

1. inducing cell/ tissue
2. induction signal
3. responding cell/ tissue (must be competent)

Front 109

Describe the formation of the cloacal and oral plates

Back 109

-distinct areas of the embryo where there is ectoderm-endoderm fusion with no mesoderm
-cloacal plate forms at day 16 and becomes the anus
-oral plate forms at day 22 and becomes the mouth

Front 110

Describe the formation and purpose of the allantois

Back 110

-forms at day 16
-diverticulum of the yolk sac (endoderm) that extends into the body salk
-site of early blood vessel formation

Front 111

When does morphogenesis of the embryo occur

Back 111

bridges weeks 3 and 4

Front 112

Describe the process of neurlation

Back 112

The notochord signals nearby ectoderm to thicken forming a neural plate

The neural plate folds at the MHP of the flor plate leading to neural folds and grooves

A secondary folding at the lateral hinge point creates the neural tube and neural crest

Front 113

Explain how the neural plate bends to form the neural tube
when does this occur

Back 113

-occurs between day 18-20
-changes in cell cycle and cell shape of floor plate cells creates a median hinge point leading to neural folds
-proliferation of mesoderm beneath the lateral area elevates the neural folds creating the neural groove
-folding at the lateral hinge point creates the neural tube and neural crest

Front 114

Explain how the neural tube closes
when does this occur?

Back 114

-occurs on day
-Apposition and fusion of neural folds is aided by formation of lateral hinge points near edges of crests

Front 115

Explain how the neural crest forms
what is it the site of
when does this occur

Back 115

occurs on day 22
-composed of a mesoderm derived from the apposing crests of teh neural folds before they fuse to form the neural tube
-source of many primary sensory neurons, autonomic ganglia, adrenal medulla, and pigment cells of skin

Front 116

Explain how the neutral tube forms the beginings of the brain. What three regions are formed

Back 116

-cranial part of neural tube forms the brain
-prosencephalon (forebrain) is cranial to the flexure that develops in the floor of the neural plate
-mesencephalon (midbrain) is at the flexure
-rhombencephalon (hindbrain) is caudal to the flexure

Front 117

Explain how the otic disc forms. when does it form

Back 117

forms on day 20
ectodermal thicekning on either side of the hindbrain becomes the otic discs that will form the internal ear

Front 118

Expalin how the optic sulcus forms. when does it form

Back 118

forms on day 22
grove on each side of the forebrain becomes the optic sulcus that forms the globe of the eye

Front 119

What three regions does the intraembryonic mesoderm develop into? What is their relationship to the notochord/each other? What do they develop into

Back 119

1. paraxial mesoderm, develops from mesenchyme on either side of notochord, forms vertebrae and parts of skull, skeletal muscles, fibrous connective tissues, and dermis of skin on back of body wall

2. Intermediate mesoderm-originates from mesechyme lateral to the paraxial mesoderm, will form urogenital ridge (kidneys, ureters, gonads, reprodutive ducts, and adrenal cortex)

3. Lateral Plate mesoderm- mesenchyme lateral to the intermediate mesoderm, will form dermis of skin on ventral lateral body wall, wall of GI and respiratory tracat, appendicualr skeleton, and cardiovascular structures

Front 120

Which intraembryonic mesoderm layer develops into the skull, skeletal muscles, fibrous connective tissues, and the dermis of the skin on the dorsal body wall?

Back 120

paraxial mesoderm

Front 121

Which intraembryonic mesoder will form the kidneys, ureters, gonads, reproductive ducts, and the adrenal cortex

Back 121

intermediate mesoderm

Front 122

Which intraembryonic mesoderm gives rise to the dermis of the skin on the ventrolateral body wall, the wall of the GI and respiratory tract, the appendicular skeleton, and cardiovascular structures?

Back 122

lateral plate mesoderm
this section of mesoderm forms the intracembryonic coelm which consists of splanchnic and somatic mesoderm, the splanchnic mesoderm is assocaited with the endoderm and eventually forms the pericardial cavity among other structures

Front 123

Describe the segmentation of the paraxial mesoderm

Back 123

-the subdivisions are aggregations of meenchyme termed somites
-somites are temporary structures that allow for further segreation of precursor cells

Front 124

Describe the steps in somite formation

Back 124

-begins at day 20
-pairs of somies form as the prmitive node regress caudally
-localized mesenchyme aggreagation forms presomites that then condenses into somites
(primitive streak=>intraembryonic mesoder=> paraxial mesoderm=> somites)
-somite mesenchyme then transfomrs into an epithelium that surrounds a small cavity in the center

Front 125

What do somites eventually turn into

Back 125

-segregate into a ventromedial area called a scleratome
-dorsolateral area called dermomyotome which later beomes the dermatome and myotome

Front 126

T/F all sections of the paraxial mesoderm differentiate into somites

Back 126

false. The 7 pairs in the head region remain unsegmented, no somites are formed

Front 127

What comprises a body wall segment

Back 127

structures derived from a single pair of dermomyotmes and the adjacent mesoderm

Front 128

What are the two myotome subdivisions and how are they innervated

Back 128

epaxial-dorsal, innervated by dorsal rami of spinal nerve
hypaxial-ventraolateral, innervated by ventral rami of spinal nerve

Front 129

From what intraembryonic mesododerm layer is the urogenital ridge formed at days 19-20

Back 129

intermediate mesoderm

Front 130

Describe the formation of the intraembryonic coelom

Back 130

-derived from the lateral plate mesoderm
-U shpaed coalescene of spaces within the lateral plate mesoderm
-blastocyst=>ICM=>epiblast=>primitive streak=>intraembryonic mesoderm=>lateral plate mesoderm=>intraembryonic coelm

Front 131

What are the two layers of lateral plate mesoderm called when they split to form the intraembryonic coelom

Back 131

1.The layer of LPM that associates with the endoderm is the splanchnic mesoderm
2. The layer of LPM associated with the ectoderm is the somatic mesoderm

Front 132

All extraembryonic membranes including the amnion and chorion are coated or lined with...

Back 132

extraembryonic mesoderm

Front 133

Angioblasts are the precursor cells of the vascular system. What tissue layer are they derived form and where and when do they initiall form

Back 133

-derived from mesoderm
-form in wall of yolk sac at day 16

Front 134

Describe early blood vessel formation

Back 134

-first vessels such as the yolk sac, heart, and aortas form in situ directed by angioblasts (vasculogenesis)
-remaining vessels develop via angiogenesis

Front 135

When does the heart form? Where are the precursor cell from?

Back 135

Heart forms on day 20
precursors are found within the splanchnic mesoderm lining the transverse part of the intraembryonic ceolom
(epiblast=>primitive streak=> intraembryonic mesoderm=>lateral mesoderm=> intraembryonic coelm=>splanchnic mesoderm)

Front 136

What two embryo folding events occur bridging the 3-4 week period

Back 136

1. Folding in the cranial/caudal (sagittal plane)
2. Folding in a lateral direction (transverse plane)

Front 137

Explain how sagittal plane folding occurs

Back 137

-folding in median axis results in C shaped embryo
-elongation of neural tube provides cranial and caudal force vectors
-creation of head and tail folds beyond edges of yolk sac

Front 138

explain how folding the lateral direction occurs

Back 138

-driven by expanding somatopleura and amnion

Front 139

how many body folds occur in the embryo

Back 139

4, head, tail, and 2 lateral

Front 140

What are the four results of embryo folding

Back 140

1. establishment of body form of embryo
2. relocation of structures to proper surface (dorsal to ventral, heart, septum transversum, oral and cloacal membranes)
3. closure of ventral body wall
4. embryo becomes completely surrounded by amnion

Front 141

Describe how the ventral body wall closes as a result of embryo folding. what occurs as a result of this

Back 141

-folding in the medain plane creates puches from the roof of the yolk sac at the cranial and caudal endo of the embryo
-the pouches becomes the foregut and hindgut, only the midgut remains connected to teh yolk sac
-the connection between the intra and extreambryonic coeloms is almost closed
-the gut is suspended within the coelom by a dorsal mesentary
-the amnion and ectoderm come together at the umbilical ring
-the embryo becomes completely surrounded by amnion

Front 142

what is the incidence of clincially significant birth defects

Back 142

2-3% at birth, 0.7% have more than 1 major defect, if the defect is not detected or manifests iself duing early childhood 4-6%

Front 143

What is the difference between a major and minor birth defect

Back 143

major-medical and/or social consequences
minor-no significant consequences (14% of children)

Front 144

Why is the prescence of minor birth defects significant even though they have no social/medical consequence

Back 144

The presence of a minor defect is a cue for checkin for major defects. Each minor found increases the chance of a major (0=1, 1=3,2=10, 3=90)

Front 145

List 5 factors associaed with increased incidence of birth defects

Back 145

1. parental age
2. season of year
3. country of residence
4. race
5. familial tendencies

Front 146

Describe the 4 D's that are used to classify disorders of development

Back 146

1. Defect-morphological abnormalities resulting from abnormal development,intrinsic to developmental process, can be inherited
2.dysplasia-distrubance in tissue organization
3. disruption-morphological abnormality resulting from breakdown or interference with originally normal developmental process, extrinisc, cannot be inherited
4. deformation-abnormal shape or position of a normally formed body part caused by nondistruptive mechanical forces

Front 147

What is the diffrence between defects and disruptions

Back 147

-defects are intrinisic to the developmental process and can be inherited
-disruptions are due to extrinsic factors that disrupt the developmental process and are not inherited
(note that inherited factors can influence the incidence of a disruption however).
- Both result in morphological abnormalities
Hint: Someone walking in from the outside is disruptive

Front 148

When do each of the following disorders of development take place
1. defect
2. dysplasia
3. disruption
4. deformation

Back 148

1.defect = embryonic period
2. dysplasia=embryonic period, some fetal period
3. disruption= embryonic to fetal
4. deformation = late in fetal period
(Hint- deformations are they only ones that take place late in the fetal period because they are based on mechanical forces acting on the fetus after the structures have begun to take form)

Front 149

Describe the 4 terms used to describe GROPUS of anomalies in infants born with mutiple problems

Back 149

polytrophic field effect-patter of anomalies derived from a single field of develpment

syndrome-pattern of multiple anomalies that are seen together and related to a common cause

association-nonrandom occurance of two or more features that occur together more frequently than expected by chance, cause often unknown

sequence-pattern or cascade of secondary anomalies that result from a single primary anomaly or initiating factor

Hint-mutliple problems make it hard to PASS develoment class

Front 150

Describe twow difference ways chromosome problems can lead to abnormal development

Back 150

1.Aneuploidy-any condition where the chromosome number is not correct e.g. trisomy and monosomy
2. Abnormal chromsome structure-deletion, translocation, duplication, inversion

Front 151

define teratogen

Back 151

any agent that can produce a congenital anomaly or raise the incidence of an anomaly. it must produce morphological anoomalies, be extrinsic to the embryo and influence development between fertilization and birth

Front 152

The degree and type of malformation caused by a teratogen depends on...

Back 152

1.dose
2. duration of exposure

Front 153

When would an acute dose of a teratogen have a greater effect than a chronic dose

Back 153

An acute dose of a teratogen can have more of a chance of affecting them embryo if it is given during a critical period for an organ or set of organs

Front 154

Give some examples of environmental teratogens

Back 154

-maternal infections
-ionizing radiation
-drugs and chemicals
-imbalance of essential metabolites and hormones
-maternal factors (illness, uterine abnormalities, age, etc)
-paternal factors-age, chemical agents, radiation, etc

Front 155

Describe the concept of multifactorial effects in relation to birth defects

Back 155

-cause 20-25% of birth defects
-result from the interaction of genetic endowment and developmental environment
-examples =cleft palate, neural tube defects

Front 156

Name the disease associated with the following trisomys
21, 18, 13

Back 156

21=down's syndrome
13= patau's syndrome
18= edward's syndrome

Front 157

Congenital adrenal hyperplasia (CAH) can result in babies with ambiguous genitalia. What is the cause of this disorder

Back 157

-deficiency of 21 hydroxylase results in overproduction of precurses proxmial to the blocked step
-the precurses are then shunted into the androgen biosynthetic pathway resulting in incrased androgen produciton
-this can masculinize female genitalia
-also have "salt-losing syndrome"

Front 158

List some clinical manifestations of CAH

Back 158

-masculinization of female genitalia, early postnatal virilization in males
-salt-lozing crisis due to adrenocortical insufficiency
-short stature due to premature fusion of epiphyses

Front 159

How is CAH treated

Back 159

-glucocorticosteriods to replace cortisol and supress excessive corticotropin production
-mineralcorticoid therapy to manage salt-wasting
-surgical procedures to correct female genitalia

Front 160

Give two examples of associations of birth defects

Back 160

Charge and Vacterl

Front 161

Describe the characteristic facial features of a child with fetal alcohol syndrome

Back 161

short palepebral fissures, flat midface, short nose, indistinct philthrum, thin upper lip, epicanthal folds, low nasal bridge, minor ear abnormalities, microganthia

Front 162

Women take an average of four drugs, excluding nutritional supplements during the first trimester of pregnancy. What is the approximate percetage of congenital anomalies known to be caused by environmental agents (including drugs)?

Back 162

10%

Front 163

Rapid growth and expansion of the___________ is primarily responsible for cranial-caudal folding of the embryo

Back 163

neural tube