Early embryology and brachial arch development

morula

After fertilization, there is the proliferative phase, in which the zygote initially undergoes a series of rapid divisions that lead to the formation of a ball of cells called __.

Morula

A solid ball of cells that makes up an embryo; in humans, this stage occurs within four days of fertilization.

Trophoblast

outer cells of the blastocyst that secrete enzymes that allow implantation

Black

Embryoblast

The inner cell mass of the blastocyst, which is the developing human organism.

Blue

4

What day does morula show

5-6

What day does blastocyst show

Blastocele

fluid filled cavity in blastocyst

Endometrium

inner lining of the uterus

Black

Trophoblast

Blue

Embryoblast

Red

Blastocoele

Yellow

Implantation of blastocyst

6 days after conception

bilaminar disc

two-layered disc (epiblasts and hypoblasts) that forms from the inner cell mass at around day 8-14

Epiblast

the SIMPLE COLUMNAR outermost layer of an embryo before it differentiates into ectoderm and mesoderm.

Hypoblast

layer of SIMPLE CUBOIDAL cells facing the blastocyst cavity

Prochordal plate

area where the epiblast and hypoblast fuse (axis of the embryo); future site of the mouth (1-2nd weeks)

1-2 weeks

How many weeks does the prochordal plate forms

Epiblast

Black

Hypoblast

Blue

Amniotic cavity

Red

Secondary yolk sac

Yellow

Prochordal plate

Green

primary yolk sac

Another name for blastocyst

Amniotic cavity

Fluid-filled cavity facing epiblast layer

Secondary yolk sac

Fluid filled cavity surrounded by Hypoblast

Gastrulation

bilaminar embryonic disc converted to trilaminar disc

Trilaminar disc

First to form, contains ectoderm, endoderm, mesoderm

Ectoderm

outermost germ layer; produces sense organs, nerves, and outer layer of skin

Endoderm

Digestive tract, respiratory tract, liver, pancreas,

Mesoderm

Muscles and skeleton

Amnion

Cells of inner cell mass begin to differentiate as __ forms

Gastrula

A __ develops when cells begin to migrate inward forming indentation and push forming the endoderm. Cells on the outside are called ectoderm

endoderm; ectoderm

A gastrula develops when cells begin to migrate inward forming indentation and push forming the __. Cells on the outside are called __

Mesoderm

The __ is formed as additional cells migrate inward between endo and ectoderm

Epiblast; Hypoblast

The three germ layers originate from the __ and not the __

Primitive streak

A groove on the surface of an early avian embryo along the future long axis of the body.

Primitive streak

__ (1) develops along the midline forming a narrow groove.

primitive node

The rostral end of the streak finishes in a small depression called __ (3) or pit (2).

pit

The rostral end of the streak finishes in a small depression called primitive node (3) or __ (2).

notochord

The __ (A), which is mesoderm, extends anteriorly from the primitive pit (2) to the prochordal plate (4).

Notochord

A flexible rod that supports a chordate's back

Mesoderm

Notochord is from the

primitive pit

The notochord (A), which is mesoderm, extends anteriorly from the __ (2) to the prochordal plate (4).

prochordal plate

The notochord (A), which is mesoderm, extends anteriorly from the primitive pit (2) to the __ (4).

separate

As a result of the cell migrations, the notochord/ mesoderm completely __ the ectoderm from endoderm, except in the prochordal (4) and cecal (9) plates.

prochordal; cecal

As a result of the cell migrations, the notochord/ mesoderm completely separate the ectoderm from endoderm, except in the __ (4) and __ (9) plates.

Cecal plate

Fusion area at the tail end of the embryo. (9)

prochordal plate

area where the epiblast and hypoblast fuse; future site of the mouth (4)

Primitive pit

Depression in primitive node (2)

cardiac plate

Cells that accumulate anterior to the prochordal plate give rise to the __ (5).

Cardiac plate

early development: the mesodermal cells continue to spread forward on each side of the notochord and prochordal plate. mesodermal cells that accumulate anterior to the prochordal plate give rise to the ______ _____ which will form the heart (5)

Rostral

toward the forehead or nose

Caudal

toward the tail

3-4 weeks

How many weeks for notochord formation begins

Notochord

Transient embryonic structure formed by condensed cells of the mesoderm layer

Embryo folding

Notochord influences the

Sonic hedgehog protein

Cells secrete ___ which difuses from notochord and help cells to know where they are in a 3D space

neurulation

The notochord extends from the primitive pit to the prochordal plate and starts the process of __

neurulation

development of the nervous system

Sonic hedgehog (Shh)

A secreted protein of the hedgehog family that plays a range of roles during development. For example it is involved in the specification of motor neurons in the developing spinal cord.

3-4 weeks

When does neural tube formation, cephalon folding, and neural crest formation

neuroectoderm

The nervous system develops as a

thickening within the ectodermal layer at

the rostral end of the embryo, forming the

neural plate or __.

Neural folds

thickening of tissue on either side of neural groove

neural groove

Neural folds delineate a deepening midline

depression (__).

neural tube

Fusion of neural folds occurs in central

body region (__) and then

proceeds cranially and caudally. Forms

anterior and posterior neuropores, when

closed (4th week) the central nervous

system is established.

Neural crest cells

Cells at the tip of the neural fold; this group of cells gives rise to many components of the peripheral nervous system.

somite

one of the paired, repeating blocks of tissue located on either side of the notochord in the early embryo

Ectoderm

Nervous system forms from

Paraxial mesoderm

gives rise to somites

Intermediate mesoderm

forms urogenital system

Lateral mesoderm

Connective tissue associated with muscle and viscera, cardiovascular system, blood, etc

Ectoderm

Black

Mesoderm

Blue

Endoderm

Red

Neural groove

Yellow

Paraxial mesoderm

Green

Neural tube

Black

Paraxial mesoderm

Blue

Lateral plate mesoderm

Red

Somite

Yellow

Endoderm

Green

Primitive pit

Black

Primitive streak

Blue

Neural groove

Red

Neural folds

Developing forebrain

Yellow

Primitive streak

Black

Area of closing

Blue

Forebrain

Red

Hind brain

Yellow

Midbrain

Green

Anencephaly

congenital deformity in which some or all of fetal brain is missing

Spina bifida

a congenital defect that occurs during early pregnancy when the spinal canal fails to close completely around the spinal cord to protect it

Neural tube

Both anencephaly and spina bifida are defects in closure of

stomatodeum

The head fold is critical to the

formation of the primitive oral

cavity (__) and

foregut.

buccopharyngeal membrane

separates the stomatodeum (primitive mouth) and the foregut. It is composed of ectodermal and endodermal tissue

Cephalic folding

Results in head development

Elongation brings only ectoderm

There is no mesoderm above the pituitary stalk

Stomatodeum

primitive oral cavity

Frontal prominence

Bulge in the forehead region that forms the upper facial area in the embryo.

Cardiac bulge

What is the inferior boundary of the stomodeum?

stomatodeum

When the __ is first formed, it is delimited rostrally by the frontal prominence and caudally by the developing cardiac bulge.