Embryo I Flashcards
definitions
process in the male by which sperm are formed
spermatogenesis
comprise walls of seminiferous tubules»_space; maintain environment for spermatogenic cells
Sertoli or sustenacular
provides an endless supply of stem cells called spermatogonia, some of which differentiate into primary spermatocytes
mitosis
produces haploid cells
meiosis
temperature dependent pathway in which spermatids are streamlined to produce sperm or spermatozoa
spermiogenesis
formation of eggs
oogenesis
oocyte encapsulated by a flattened single layer of stromal cells
primordial follicle
fluid filled cavity in follicle
antrum
release of the oocyte from the ovary
ovulation
“morning after” pills contain high doses of estrogens»_space; disrupts estrogen/progesterone balance thereby inhibiting ovulation
emergency contraception
follicular cells remaining in ovary that secretes progesterone which is essential in maintaining enhanced uterine lining
corpus luteum
follicular cells surrounding the oocyte
corona radiata
glycoprotein covering that directly surrounds the oocyte
zona pellucida
one haploid nucleus receives no cytoplasm
polar body
mixture of sperm and glandular secretion
semen
shorten life span of sperm and greatly decrease motility in female tract
intrauterine devices
removal of glycoprotein coat and seminal proteins from the acrosomal plasma membrane of the sperm
capacitation
activation and release of enzymes necessary to penetrate through the zona pellucida
acrosomal reaction
the process by which male and female gametes fuse to form a diploid zygote
phases of fertilization
primary enzyme responsible for penetration through corona radiata
hyaluronidase
primary enzyme responsible for penetration through zona pellucida
acrosin
after penetration of 1st sperm»_space; zona becomes impermeable to penetration by other sperm
zona reaction
when 2 sperm penetrate the zona pellucida simultaneously»_space; triploid fetuses spontaneously abort
dispermy
fertilization through implantation
pre-embryonic stage
implantation through 8 wk
embryonic stage
9 wk through birth
fetal stage
repeated rounds of cell division
cleavage of the zygote
solid mass of 16-32 blastomeres»_space; typical stage that enters uterus
morula
fluid filled hollow with inner cell mass (embryoblast) in embryonic pole
blastocyst
outer layer of cells
trophoblast
attachment and subsequent burrowing of the blastocyst into the uterine lining
implantation
connective tissue cells of endometrium that become engorged with carbohydrates and lipids at implantation site»_space; engulfed by syncytiotrophoblast
decidual cells
when an embryo implants somewhere other than the uterine lining»_space; first sign typically abdominal pain during early pregnancy
ectopic pregnancy
due to scarring of uterine tubes
tubal pregnancy
(prevents cell division) upon ultrasound confirmation of tubal pregnancy
methotrexate
the process by which the bilaminar disk develops into a trilaminar disk»_space; demonstrates three germ lines
gastrulation
thickening of epiblast due to proliferation and migration of cells
primitive streak
actively forms mesoderm until early fourth week»_space; then diminished to insignificant structure in embryo
fate of a primitive streak
when remnants of the primitive streak persist and proliferate
sacrococcygeal teratoma
cellular rod that develops from the notochordal process
notochord
thickening of ectoderm overlying the notochordal process, often called neuroectoderm»_space; first evident at approximately day 18
neural plate
formed by infolding and fusing of neural folds»_space; will form CNS
neural tube
last component of neural folds to close»_space; improper closing results in neural tube birth defects
caudal and cranial neuropores
forms many PNS structures (ganglia and sheaths of nerves) plus part of meninges and adrenal medulla
neural crest
enlargements of mesoderm located immediately lateral to the notochord
somites
will develop into body cavity
intraembryonic coelom
becomes body wall
somatopleure
becomes wall (but not lining) primitive gut
splanchnopleure
the development of new blood vessels»_space; begins in extraembryonic mesoderm and (wall of yolk sac) and then in lateral mesoderm of embryo
vasculogenesis
formation of new blood cells»_space; function of endothelial cells lining vessels of the extraembryonic mesoderm»_space; does not occur in embryo until week five
hematogenesis
consist of syncytiotrophoblasts with a cytotrophoblast core»_space; develop by the end of week 2
primary chorionic villi
have a mesenchymal core»_space; develop during the third week
secondary chorionic villi
contain capillaries in the core due to the differentiation of mesenchymal cells»_space; capillaries connected to embryonic circulation
tertiary chorionic villi
disorganized proliferating chorion (placenta) resulting from an abnomal pregnancy (
hydatidiform mole
triploid»_space; 23 maternal chromosomes and 46 paternal
results from either dispermy or endoreduplication of paternal chromosomes
fetus present but not viable
very low malignancy potential
partial hydatidiform mole
46 chromosomes»_space; all of paternal origin
results from an empty egg being fertilized by either two
sperm (dispermy) or a single sperm that undergoes endoreduplication
no fetus present
potential invasiveness and even metastatic malignancy
complete hydatidiform mole
lateral body wall folding toward median plane
lateral folds
gives rise to vertebrae and ribs
sclerotome
give rise to dermis of the skin on dorsum of body
dermatome
gives rise to gonads, kidney, adrenal cortex and ureter
intermediate mesoderm
dermis of skin on ventral surface
serosa of ventral body cavity
migrate into limb buds»_space; bones, ligaments and dermis
somatic mesoderm
smooth muscle of primitive gut + derivatives
serosa of viscera
heart, blood and lymphatic vessels
bone marrow and lymphoid tissues
splanchnic mesoderm
40 weeks LNMP or 38 weeks after conception
normal gestational period
irregular menstrual cycles
oligomenorrhea
major growth promoting factor during development»_space; both mitogenic and anabolic
insulin-like growth factor I (IGF-1)
when an infant is at or below the tenth percentile for its expected birth weight at a given gestational age
intrauterine growth retardation (IUGR)
chorion, yolk sac, amnion and allantois»_space; formed from embryo but do not become significant parts of fetus
fetal membranes
primary site of exchange between mother and fetus
placenta
functional layer of the gravid uterine lining that is shed after parturition
decidua
component deep to embryo»_space; will attach firmly to the chorionic villi to give rise to maternal portion of the placenta
decidua basalis
superficial portion of decidua that covers the aembryonic pole»_space; becomes stretched and then degenerates when compressed between the chorion and the decidua parietalis
decidua capsularis
all other parts of the decidua»_space; will come in contact with the growing chorion to obliterate the lumen of the uterus
decidua parietalis
villi under decidua capsularis degenerate
smooth chorion
villi adjacent to decidua basalis continue to grow and branch»_space; becomes fetal portion of the placenta
bushy or villous chorion
fragments of syncytiotrophoblast that enter maternal circulation»_space; degenerate without any problems
currently in development = maternal blood used for testing fetal DNA
syncytial knots
villi penetrate into myometrium (muscle layer of uterus)
placenta accreta
full thickness of myometrium
placenta percreta
placenta covers internal uterine os»_space; bleeding during 3rd trimester and Cesarean section required
placenta previa
contains allantois and umbilical vessels
connecting stalk
approximately 2 cm in diameter and 50-60 cm long
umbilical cord at birth
due to umbilical vessels being longer the cord itself
false knots
inserts at edge of placenta
battledore placenta
inserts into fetal membranes with vessels then transversing between amnion and chorion»_space; easily torn
velamentous insertion
result from tears in the amnion»_space; origin most likely infection or toxic insult
can encircle head or extremities»_space; amputations, ring constrictions or craniofacial abnormalities
amniotic bands
primarily composed of maternal interstitial fluid
minor amounts produced by amniotic cells
amniotic fluid
fetal excrement in the amniotic fluid»_space; occurs during very late pregnancy
meconium
too little amniotic fluid
oligohydramnios
nutritional source during weeks 3 and 4
first site of hemopoiesis
incorporated as midgut during week 4»_space; endoderm gives rise the epithelium of respiratory and digestive organs
site of development of primordial germ cells
yolk sac
its blood vessels give rise to the umbilical vessels
allows for better exchange through placental membrane
portion becomes the urachus»_space; becomes the median umbilical ligament
allantois
rostral u-shaped portion
pericardial coelom
superior lateral portions
pericardioperitoneal canals
inferior lateral portions
peritoneal coelom
double layer of peritoneum that originates as an extension of
the visceral peritoneum to cover an organ
mesenteries
located in lateral walls of pericardioperitoneal canals
pleuropericardial membranes
contribute muscle to the periphery of the diaphragm
lateral body walls
typically occurs posterolaterally allowing abdominal contents to enter thoracic cavity
results in pulmonary hypoplasia that can be life threatening
congenital diaphragmatic hernia
congenital anomalies = congenital malformations = developmental disorders present at birth
birth defects
agents that cause birth defects
teratogens
causes IUGR
cigarette smoke
constricts uterine blood vessels
nicotine
maternal consumption believed to be most common cause of mental deficiency»_space; more pronounced effects if poor nutrition also a factor
alcohol
children have behavioral and learning difficulties»_space; caused by moderate consumption or 1-2 binges
fetal alcohol effects
growth, physical and mental anomalies associated with children who mother was a chronic alcoholic during pregnancy
fetal alcohol syndrome
cause masculinization of female fetuses
androgens
component of birth control pills»_space; VACTERL syndrome (vertebral, anal, cardiac, tracheal, esophageal, renal and limb anomalies)
progesterone
genital tract anomalies in both sexes and increased incidence of adenocarcinoma of the vagina later within the child
diethylstilbesreol (a synthetic estrogen)
yellowing of teeth, low enamel deposition and diminished growth of long bones
tetracycline
handful of cases reporting 8th cranial nerve damage
streptomycin
classic example of a teratogenic drug
commonly utilized as to treat morning sickness 1957-61
causes meromelia
other medical uses but only for women on non-childbearing age
thalidomide
causes mental retardation and motor dysfunctions
most commonly obtained through fish and seafood
mercury
causes increased miscarriage, multiple anomalies, IUGR and functional deficits
maternal exposure to sub-clinical levels can cause neurobehavioral and psychomotor disturbances
most common source is dust or chips from paints used prior to 1978»_space; many other potential sources as well
lead
produce IUGR and skin discoloration
coolant/insulator used until 1979»_space; persists in environment and accumulates in sports fish
polychlorinated biphenyls (PCBs)
interferes with eye and/or ear development
rubella (German measles)
usually asymptomatic in mothers, but can be lethal in infants or produce mental retardation
cytomegalovirus
asymptomatic in mother, but affects CNS in infants
obtained from raw meats and the feces of domesticated animals, particularly cats
Toxoplasma gondii
high does rapidly kills proliferating cells»_space; also a mutagen
radiation as a cause of birth defects
poorly controlled diabetic mother 3-4X greater risk of birth defects, plus higher incidence of stillbirths, neonatal deaths and macrosomia
diabetes
high serum phenylalanine teratogenic for mental retardation, microcephaly and heart defects
phenylketouria (PKU)
animal studies link several vitamin and mineral deficiencies to birth defects, but only two widely accepted for humans
nutritional deficiencies
leads to congenital cretinism»_space; results in retarded growth and brain development
iodine deficiency
leads to neural tube disorders
folate deficiency
narrowing of lumen
stenosis
lack of lumen
atresia
celiac trunk is blood supply to ___?
foregut (distal to pharynx)
superior mesenteric artery is blood supply to ___?
midgut
inferior mesenteric artery is blood supply to ___?
hindgut
rapid growth to yield most of small intestine
cranial limb
intestines remain herniated into umbilical cord at birth
omphalocele
umbilicus does not properly close»_space; abdominal contents herniate upon increased abdominal pressure
umbilical hernia
incomplete closure of lateral folds resulting in protrusion of viscera
gastroshisis
results in small intestine on right and entire colon on left»_space; fairly common
nonrotation
results in appendix located near liver
subhepatic cecum
small intestine wrapped in a hernia-like mesentery sac
internal hernia
twisting of intestines»_space; creates obstruction
volvulus
causes anomalies when is fails to degenerate
omphaloenteric duct
proximal omphaloenteric duct fails to degenerate, leaving a blind-ends pouch»_space; can become inflamed and mimic appendicitis
Meckel’s diverticulum (ileal diverticulum)
produces umbilicus that is open to ileum»_space; allows release of digestive material
omphaloenteric fistula
can become infected»_space; painful with possible drainage through umbilicus
omphaloenteric cysts
can allow blood bleeding through umbilicus
persistent fibrous cord with vitelline artery
urethra, vagina and rectum empty into a single vestibule
persistent cloaca
anal canal ends blindly, or forms fistula with vagina or urethra
anal agenesis, with or without fistula
anus exists anterior to anal pit
anoperitoneal fistula
nonfunctional lungs histologically resemble an exocrine gland
pseudoglandular period (6-16 weeks)
development of respiratory bronchioles and distal structures + increased vascularization
canalicular period (16-26 weeks)
number of alveolar sacs increases + thinning of respiratory membrane
terminal sac period (26 weeks to birth)
increased number + thinning of alveoli»_space; 95% of mature alveoli develop postnatal
alveolar period (birth to 8 years)
premature infants lack surfactant and cannot ventilate properly
infant respiratory distress syndrome