Embryology Flashcards
the heart and great vessels come from what cell line?
the mesenchymal cells in the cardiogenic area
at what point do vasculogenesis and angiogenesis, blood vessel development begin?
at the beginning of the 3rd week
where does vasculogenesis and angiogenesis happen?
in the extraembryonic mesoderm of the yolk sac, allantosis and chorion
how does the heart tube form?
2 endothelial-lined channels, known as the endocardial heart tubes, fused together to form the heart tube
by the end of the 3rd week what does the primoridal CVS look like?
the heart is represented by the heart tubes and is joined by blood vessels from the embryo and extraembryonic membrane
What 4 main segments compose the inferior vena cava?
- hepatic segment; from the hepatic vein and sinusoids. 2. prerenal segment; from the right subcardinal veins. 3. renal segment; from the subcardinal supra anastomosis 4. post-renal; from the right supracardinal vein.
what germ layer forms the excretory organs?
mesoderm
what germ layer forms the glands opening into the GI tract?
endoderm
what germ layer forms the glandular cells o the liver and and pancreas?
endoderm
what germ layer forms the lining of the GI tract?
endoderm
what remnants persist after the joining of the embryonic palantine processes and is located in the soft palate>
the palantine raphe
the embryonic ductus venosus become what after birth?
ligamentum venosum
the embryonic umbilical vein become what after birth?
ligamentum teres
the embryonic umbilical arteries become what after birth?
umbilical ligament
from what does the aorta and pulmonary trunk develop?
a. bulbar ridges fuse and become an aorti-copulmonary septum. b. this then divides the bulbus cordis and the truncus arteriosis into two arterial channels. c. these two channels become the aorta and the pulmonary tree.
The aorta and the pulmonary truck are formed when in gestation
between week 5 and 6
At what point can a fetal heart beat be detected by a doppler heart monitor?
7 weeks after the last known menstrual period, aka 5 weeks in fertilization terms.
Fetal circulation happens in what order?
The umbilical vein delivers oxygenated blood. After bypassing the liver, the blood moves from the ductus venosus into the IVC and the right atrium. It enters the left atrium and ventricle through the foramen ovale. It enters the pulmonary trunk at the same time via the ductus arteriosis. After it enters the lung and the peripheral body through the aorta, it is passed back to the placenta thanks to the umbilical arteries.
The embryonic foramen ovale become what after birth?
fossa ovalis
the embryonic ductus arteriosis becomes what after birth?
ligamentum arteriosum
what forms the atria?
the separation into the right and left of the primitive sinuatrium or septum primum.
the fusion of the endocardial and atroventricular cushions posteriorly and anteriorly forms what?
the tricuspid and mitral inlets which become the AV valves.
what does the interventricular foramen result in?
by the end of week 7 it closes resulting in the interventricular septum.
from what tissue does the hypothalamus develop?
ectodermal tissue (on day 32 the hypothalamic sulcus develops from the diencephalon)
what tissue invaginates to form the anterior lobe of the pituitary gland? what is this known as?
Ectodermal tissue of the oropharynx, Known as: Rathke’s pouch (which eventually extends down to the HTH and becomes the pituitary stalk)
from what does the posterior lobe of the pituitary gland arise ?
neural crest
what does the pancreas form from?
two diverticular buds of the foregut
by what week have the first islet of the pancreas appeared?
around week 10, they first appear at the tail of pancreas
from what tissue does the thyroid develop?
its starts developing in the primitive ailmentary tract and consists of endodermal cells.
where does the thyroid first develop?
in the buccal cavity
what structure does the thyroid gland help to develop as it matures?
the tongue
what embryonic connection do the thyroid and tongue share?
the thyroglossal duct
where on the tongue does the thyroglossal duct open?
the foramen cecum
from which pouches do the parathyroid glands develop?
the superior glands descend from the 4th pharyngeal pouch and the inferior glands from the 3rd pharyngeal pouch.
True or false; the adrenal cortex and medulla develop from the same embryonic line?
false, the cortex develops from the coelomic mesodermal tissue and the medulla arises from the ectodermal tissue of the neural crest.
Between the adrenal cortex and the medulla, which develops parallel with the sympathetic nervous system?
the adrenal medulla
angioblasts from from what?
mesoderm
angioblasts form what as they cluster?
blood islands
the blood islands fuse together to form what?
a primordial vascular network
hemocytoblasts arise from what?
core cells within blood islands
blood formation occurs at what week?
week 5
what is the allantosis?
it is the part of the yolk sac that extends outward into the connecting stalk
what is the role of the allantosis?
it is involved in early blood formation, plays a role in bladder development, and its blood vessels become umbilical arteries and veins.
the liver starts hematopoesis during which week?
week 6
the fetal spleen takes over hematopoesis when?
week 26 to 28
from what does the thymus arise?
the 3rd pharyngeal pouch
what tissue forms the cortex and medulla of the thymus?
the cortex is formed from the ectoderm and the medulla is formed from the endoderm
the spleen arises from which germ line?
mesoderm
what are present in the spleen by the first trimester?
macrophages
True or false: the spleen is capable of hematopoiesis during fetal life
True, as well as after birth
what germ layer forms the bone marrow?
mesoderm
before bone marrow develops where are blood cells formed?
they start being produced in the yolk sac, then the liver takes over, and lastly the spleen handles the responsibility till the bone marrow matures.
what germ layer forms the connective tissue?
mesoderm
what germ layer forms the epidermis?
ectoderm
from what do the dermis and hypodermis arise?
mesoderm
how does the periderm develop?
ectodermal cells proliferate and forma layer of epithelium called periderm and a basal layer at the same time.
what happens to the peridermal cells?
the cells undergo kertinization and desquamation and are slowly replaced by other cells arising from the basale layer.
what germ layer forms the retina of the eye?
ectoderm
what is the lanugo?
a downy coat of delicate hairs that cover a 5-6 mo old fetus
sweat and sebacous glands develop from what?
sebacous glands develop from epithelial root sheaths of hair follicles and eccrine sweat glands develop from down growths in the mesenchyme
What germs layer forms smooth ms coat?
mesoderm
what germ layer forms smooth ms?
mesoerm
what germ layer forms the skeleton ?
mesoderm
what germs layer form striated ms?
mesoderm
These pair blocks of mesoderm give rise to skeletal ms?
somites
what are the 3 layers that the somite splits into?
myotome, dermatome, and sclerotome layers
what are the 4 support cells (fibroblasts, chondrocytes, osteoblasts, and myofibroblasts) derived from?
mesenchyme
what activates the transcription of ms specific genes and mygoenic cell diffentiation?
MyoD
how do limb muscles develop?
cells migrate from the ventral dermomyotomes of somites and form limb buds.
what happens to cells that move into limb buds?
they undergo epitheliomesenchyma transformation
what germ layer forms the central and peripheral NS?
ectoderm
what happens after anteroposterior invagination of the neural placode?
the lateral ends fold to form the neural tube
once the neural tube has formed, what happens next?
neuroepithelial cells proliferate resulting into neuroblasts
after proliferation (resulting in neuroblasts) what do the cells do?
they migrate to mature sites in order to establish synaptic connection and extend axons to the target tissues
what doe the neural crest and neural tube eventually become?
the neural crest differentiates into the majority of the PNS and ANS (consisting of cranial, spinal, and autonomic ganglia). The neural tube differentiates into the CNS, consisting of the brain and spinal cord.
what are astrocytes and ependymal cells formed from?
Radial glial cells
what cells differentiate into microglial cells?
mesenchymal cells
the primordial meninx eventually become what structure?
the spinal meninges
what germ layer forms the epithelial lining of the resp tract?
endoderm
what is the sulcus larngotrachialis?
the groove in the ventral lower pharynx that will develop into the lungs
what is the next step in lung development?
the true lung primordium buds from the lower portion.
After the true lung primordium forms, what happens next?
it divides into 2 main bronchi and the endodermal branches into the lobes
when can the lung primordium first be observed?
28 days
the epiglottis develops from what structure?
the hypopharyngeal eminence
what cell is the precursor of ciliated epithelium and secretory cells in the pulmonary system?
cubic epithelium
a premature fetus born after 26 weeks has better odds of survival due to what?
capillaries have bulged into developing alveoli thus establishing a blood-air barrier and allowing for adequate gas exchange
at what point in development are the terminal sacules lined with type 1 alveolar cells?
by week 26
when do type II alveolar cell start producing surfactant?
by week 20 small amounts are produced, but adequate levels for survival are only produced around week 26-28.
what days on the menstrual cycle form the menstrual phase?
days 1-4
the secretory or luteal phase occurs on what days of the menstrual cycle?
days 15-28
the proliferative or follicular phase occurs on what days of the menstrual cycle?
day 4-14
what hormone is released to promote the development of the follicle?
FSH
what causes a surge of LH?
Estrogen
what is the zygote?
diploid cells resulting from union of sperm and ovum
what structure consists of 12-15 blastomeres?
morula
what contains are fluid-filled cavity that separates teh blastomere into two parts?
Blastula
how soon after fertilization does implantation in the endometrial epithelium of the uterus take place?
6 days
what forms the wall of the gestational or chorionic sac?
chorion membranes
what forms the floor of the amniotic cavity?
epiblast
what forms the roof of the exocoelomic cavity?
hypoblast
what is the process of bilaminar embryonic disc development into trilaminar embryonic disc called?
Gastrulation
What are the 3 trilaminar layers called?
Ectoderm, mesoderm, endoderm
what germ layer forms the reproductive organs?
mesoderm
what fetal organs are developed at 4 weeks gestation?
Heart, forebrane, upper and lower limbs, ears, lens of the eye.
at what stage does the external auditory canal develop?
6 weeks
at what stage do the digits and external genitalia develop?
8 weeks
at what stage do do the intestines develop?
7 weeks
at what stage does the ossification of bone begin?
7 weeks
True or false: fibrocartilage forms the temporary fetal skeleton, which eventually is replaced by bone?
False, it is Hyaline cartilage
Describe the schema for fetal circulation.
oxygenated blood from placenta via umbilical vein; through ductus venosis (bypasses the liver), into the IVC and right atrium; through the foramen ovale to the left atrium and left ventricle, or into right ventricle and pulmonary trunk to ductus arteriosus (bypasses lungs); from aorta to internal iliac and umbilical arteries, to the capillaries in the chorionic villi of the placenta
the kidneys and ureter arise from what germ layer?
intermediate mesoderm
the kidney develop from what entity?
urogenital ridge
of the 3 subsets of the urogenital ridge, which matures into the actual kidneys?
the metanephros
from which part of the metanephros does the renal pelvices, calyces, and collecting duct develop?
the ureteric buds
the ureters develop from which portion of the metanephros?
the proximal part known as the ureteric ducts
what are the other 2 primitive kidney structures called?
the pronephros (formed in the begining of week 4), and the mesonephros (formed at the end of week 4)
the metanephros forms when?
its is formed in week 5, but it does not actually function till week 9.
from what germ line do the bladder and urethra develop?
urogenital sinus
What is the primordium of the central tendon of the diaphragm in the adult?
the septum transversum
What do the pair pleuroperitoneal membranes later become?
the fibrous pericardium surrounding the heart
what is the primordium of the crura of the diaphragm?
dorsal mesentery of the esophagus
when does the diaphragm become innervated by the phrenic nerves (originate C3, 4, 5)?
week 4
what is congenital diaphragmatic hernia?
herniation of the abdominal contents into the pleural cavity. Bochdalek’s hernia- most common and L posterior lateral
which pharyngeal arch makes the aorta?
4th arch
What fold is responsible for creating the trachea and esophagus (i.e. separating the two structures) and what major pathology would it cause if this did not occur properly?
Tracheoesophageal. Trachea and TE fistula can result with the failure to fuse to create the tracheoesophageal septum. (weeks 5-6)
what type of esophageal fistula is the most common?
“type c”, esophageal atressia w/TE fistula at the distal 1/3rd end of the trachea.
what do type 2 pneumocytes make?
surfactant (decreases surface tension in alveoli)– decrease seen in premies
function of type 1 pneumocytes?
provide a barrier of minimal thickness that is readily permeable to gases such as oxygen and carbon dioxide.
When do the lung buds form– into main (primary) bronchi?
week 5
what is the sequence of lung development?
main/primary bronchi –>lobar/secondary –>segmental /tertiary –> segmental bronchi
What are the periods of lung development?
Pseudoglandular: W 7-16, Canalicaular: W16-24, Terminal sac: W24-birth, Alveolar: W32-8 yrs
what other defect is seen with pulmonary hypoplasia (PH)?
Classically involves the right lung in association with right sided obstructive congenital heart defect and congenital diaphragmatic hernia. (no heart defects if occurs on Left side)
What disease is caused by the deficiency or absence of surfactant?
Hyaline membrane disease
Hyaline membrane disease is associated with what type of hemorrhage?
Germinal matrix hemorrhage(GMH)
What condition is associated with Bronchiectasis?
cystic fibrosis
What is the classic Xray finding of bronchiectasis?
honeycombing
the Ligamentum arteriosum used to be?
ductus arteriosusm (fetus)
the fossa ovale used to be…
foramen ovale (fetus)
the ligamentum venosum used to be…
ductus venosus (fetus)
the ligamentum teres used to be…
the left umbilical vein (fetus)
the medial umbilical ligament used to be…
right and left umbilical arteries (fetus)
what system does the intermediate mesoderm create?
GU : kidneys and gonads
the paraxial mesoderm is responsible for…
the head and somites (scleroderm, myotome, dermatome)
