Weeks 3-8 Development Flashcards
when primary germ layers give rise to tissues and organs; at the end of this period, main organ systems established
organogenesis
organogenesis is an ___ period that occurs from ____
embryonic; week 3-8
neurulation is the process by which the ____ forms the ____
neural plate; neural tube
neurulation occurs in the ____ via _____
ectoderm; notochordal induction
neurulation completed by the end of ____
4th week
four main events of neurulation
- formation of neural plate
- shaping of neural plate
- invagination of neural plate
- closure of neural groove
during neurulation, notochord induces thickening in overlying ____ along midline of ____ forming _____ (these cells make up neuroectoderm)
ectoderm; embryo; neural plate
laterally elevated edges
neural folds
depressed midregion of neural plate
neural groove
neural folds begin to move together and eventually fuse. this fusion begins in ____ and progresses both ___ and ____; this results in the formation of the _____
cervical region (5th somite); cranially; caudally; neural tube
____ fuse at midline (progressing cranially and caudally), forming the ____, which separates from the _____
neural folds; neural tube; ectoderm
neural groove will become the _____
neural canal
until fusion is completed the cranial and caudal ____ allow the ____ to communicate with the _____
neuropores; neural tube; amniotic cavity
closure of these neuropores indicates _____
the end of neurulation
As neural folds fuse, cells at lateral border (crest) of neuroectoderm dissociate, called _____
neural crest cells
neural crest cells undergo _____ transition and enter the underlying _____
epithelial to mesenchymal; mesoderm
mesoderm near midline proliferate to form thickened _____
paraxial mesoderm
more laterally, the mesoderm stays thin, known as _____
lateral plate mesoderm
in between paraxial and lateral plate mesoderm is the ______
intermediate mesoderm
intracellular cavities split lateral plate mesoderm into:
- somatic or parietal layer (lines the amnion)
- splanchnic or visceral layer (lines yolk sac)
the cavity between the somatic/parietal layer and splanchnic/visceral layer is the _____; it is continuous with the _____ on each side of the embryo
intraembryonic cavity; extraembryonic cavity
____ is the organization of the paraxial mesoderm which occurs at the beginning of week 3
somite
at the beginning of week 3, the paraxial mesoderm starts to organize into segments which form ____ to ____ beginning in ____ region; organized pairs called ____
cranially; caudally; occipital; somites
the paraxial mesoderm will give rise to most of the _____, _____and ____
axial skeleton; skeletal muscles; dermis of the back
somites (in pairs)
- 4 occipital (will disappear)
- 8 cervical
- 12 thoracic
- 5 sacral
- 5 lumbar
- 8-10 coccygeal (last 5-7 disappear)
the ____ of the embryo can be determined by counting somites
age
during somite differentiation, ____ cells undergo ____ and arrange in donut shape around _____
mesoderm; epithelization; small lumen
during somite differentiation, cells in ventral and medial walls shift position to surround _____, forming the _____
neural tube; sclerotome
during somite differentiation, cells between dorsomedial cells and ventrolateral cells form the _____
dermatome
during somite differentiation, cells at dorsomedial and ventrolateral edges of upper region of somite form precursors for _____
muscle cells
cells will become ____ and migrate beneath _____ and form the _____
mesenchymal; dermatome; myotome
somite derivatives
- sclerotome: vertebrae and ribs
- dermatome: dermis
- myotome: muscles
the outer lining of cells will become the ____
epidermis
intermediate mesoderm derivatives:
differentiates into urogenital structures of urinary system and reproductive system
lateral plate mesoderm derivatives: the _____ along with overlying ectoderm form lateral body wall folds that will help close _____
parietal mesoderm layer; ventral body wall
mesoderm cells of _____ surrounding the intraembryonic cavity form ______, i.e. _____ that line ______ and secrete ____
parietal layer; mesothelial membranes; serous membranes; peritoneal, pleural, and pericardial cavities; serous fluid
_____ together with overlying endoderm form walls of the _____
visceral mesoderm layer; gut tube
mesoderm cells of visceral layer form thin _____ around each organ
serous membrane
blood vessels arise from blood islands
vasculogenesis
blood vessels sprouting from existing vessels
angiogenesis
blood cells and blood vessels rise from ____, vasculogenesis is what is occurring in embryo
mesoderm
blood islands begin to form in mesoderm surrounding wall of ____ during ____, then later in the _____ and other regions
yolk sac; week 3; lateral plate mesoderm
endoderm derivatives will form the _____; lines the ____ of the embryo and forms the _____
gastrointestinal tract; ventral surface; roof of yolk sac
body folding simultaneously occurs in both the ____ as well as the _____ and takes the embryo from a ____ to a _____
sagittal plane (i.e. cranial/caudal folds); horizontal plane (i.e. lateral folds); flat disc; cylinder
in cranial folding, the _____ acts as a hinge and swings vertically
oropharyngeal membrane
in cranial folding, part of yolk sac endoderm is incorporated into embryo as the ____ (proximal portion of GI tract)
foregut
in cranial folding, the oropharyngeal membrane separates the ____ from the _____ (will rupture about day 26)
foregut; oral cavity
in caudal folding, the ____ swings ventrally
cloacal membrane
in caudal folding, portion of yolk sac endoderm is incorporated as the embryonic ____ (distal portion of GI tract)
hindgut
in caudal folding, the _____ (future umbilical cord) is now attached to ____ aspect of embryo
connecting stalk; ventral
in lateral folding, the ____ part of the yolk sac endoderm is incorporated as embryonic _____
dorsal; midgut
at the end of the 4th week, lateral folds fuse, except at region of ______
connecting stalk
In lateral folding, the ____ connection to the yolk sac constricts, leaving a narrower connection: ______
midgut; the omphaloenteric duct (vitelline duct)
parietal and visceral layer of serous membranes continuous at _____
dorsal mesentery
the dorsal mesentery suspends ____ from posterior body wall into _____
gut tube; peritoneal cavity
the ventral mesentery is only the ____ to the upper part of the _____; it results from the thinning of _____
caudal foregut; duodenum; septum transversum
mesenteries double layers of peritoneum which provides pathway for ___, ____ and ____
blood vessels; nerves; lymphatics
the embryonic body cavity is comprised of:
- pericardial cavity
- 2 pericardioperitoneal canals
- peritoneal cavity
what is the septum transversum?
mesoderm between the thoracic cavity and yolk sac
the septum transversum does not separate ____ and ____ cavities completely because of two _____ canals
thoracic; abdominal; pericardioperitoneal
as lung buds grow, they expand into ______
pericardioperitoneal canals
______ grow in medially from the lateral walls of the pericardial cavity, dividing it into the definitive ____ and ____ cavities
pleuropericardial folds; pericardial (1) and pleural cavities (2)
_____ develop from the dorsal body wall and fuse with the septum transversum, closing off the pericardioperitoneal canals on either side of the foregut during formation of the ____
pleuroperitoneal folds; diaphragm
diaphragm components:
- septum transversum
- pleuroperitoneal membranes
- mesentery of the esophagus
- body wall mesoderm
