Premedical Biology Individual development in humans

Premedical Biology

Individual development in

humans

Questions, answers on the next slide

• What is the name of the cell after a fusion of sperm and

ovum cell?

• How many chromosomes does the cell have?

• What does the totipotent cell mean?

• What does a proliferation mean?

• What does a differentiation mean?

• Zygote (46 chromosomes) develops into embryo by cell

division (mitosis). Cell differentiate and create a three-

dimensional form = morphogenesis

• Zygote has genetic information for cell functions and the

program of differentiated cells of the whole organism, body.

• Zygote is totipotent cell

• Proliferation is cell division and growth

• Differentiation is a functional and morphological

diversification

Zygote and embryonal development


• What molecules are responsible for the regulation of early

differentiation of and embryo?

• What is the function in details of these molecules?

Responsible of early differentiation and

early development are:

1. Maternal determinants in egg:

protein molecules, RNA, mRNA….= cytoplasmatic

information molecules, cytoplasmatic determinants


• What molecules are also responsible for the regulation of

differentiation of an embryo?

• What is the origin of these molecules?

• What cells are able to react to these molecules ?

• What is the result of the interaction?

• What is the other way of a communication of cells in the

developing embryo?

• What are the general ways of cell communication ?

• What are the general types of cell signaling?

2. Signal molecules/ Induction

Signal molecules are determined by offspring genome.

It is a type of local signaling between cells in early embryo.

Signals (molecules) have target cells, target cell has an

ability to respond to signals by receptors. The interaction is

accomplished by a change of transcription /regulation of

gene expression.

Cell-cell surface interactions results in a change of

transcription /regulation of gene expression.

Induction / signalling / regulation of gene expression


• What does it mean morphogenesis?

• What molecules are responsible for the regulation of

morphogenesis?

• How does the morphogens work?

• What is the result of the interaction?

• What are products of morphogens?

= formation of the structure of an organism or part; differentiation

and growth of tissues and organs during development.

Anteriorposterior and dorsoventral axe

is done by gradients of products = transcription factors

of maternal regulatory genes ……..…morphogenes

= proteins, which interact with DNA. They activate or deactivate

the transcription of other genes.

In the end of regulatory cascade molecules control cellular

behaviors. Transcription factors have positional information,

they determine the location relative to body axes.

Morphogenesis

Question, answer on the next slide

• What is a consequence of morphogenetic different

expression of transcription factors?

Result of different gene expression, different regulation in the

different part of embryo, is a different development of body

parts.

Different types of cells in the body have the same genetic

information, but create different proteins as result of

regulation of transcription.

Results are tissue specific proteins / determinated

/differentiated cells

Morphogenesis


• What are the groups of genes responsible of morphogenesis,

segmentation and different development of body parts?

groups of genes

Egg-polarity genes, maternal - bicoid

Segmentation genes, embryonic:

Gap genes – division alongside the axe

Pair-rule genes – segmentation (every second)

Segment polarity genes

Homeotic genes

Positional information


• What are homeotic genes, homeobox?

• What is the consequence of mutation of homeotic gene?

• What do the homeotic gens encode?

Homeotic genes / Homeobox

are evolutionarily highly conserved. They are responsible

for a formation of specific anatomical structures of each

body part, for a identity of body parts.

Mutations lead to formation of the same structures at the

wrong parts.

HOX genes:

encode transcription factors with homeodomain, which is

able to bind to DNA / switch on or off

Homeotic genes / Homeobox are evolutionarily highly

conserved.


• What are the morphogenetic processes?

• What are the morphogenetic movements?

Morphogenetic processes

Proliferation

Distribution

Integration

Reduction

Morphogenetic movements

Movements of epitelial embryo cells:

- invagination movement of epithelium

- extension movement caused by rearrangement

- locomotive movement (migration)


• Assign humans in the animal kingdom according to the basic

developmental morphological differences…

Porifera - sponges

Cnidaria – jellyfish, corals, anemones

Ctenophora – coma jellies

Platyhelminthes – flatworms

Rotifera

Nematoda – roundworms

Nemertea – ribbon worms

Bryozoa

Phoronida

Brachiopoda

Mollusca – clams, snails, octopuses

Annelida – segmented worms

Arthropoda – crustaceans, insects, spiders

Echinodermata – sea stars, sea urchins

Chordata – lancelets, tunicates, vertebrates

two germs layers

Radial

three germs layers

Schizocoelom

Bilateral

Protostomia / mouth from

blastopore

Pseudocoelom

Coelom without segmetation

Coelom with segmentation

Segmentation homonomously

Sedmentation herenomously

Deuterostomia / anus from

blastopore, mouth

secondarily

Animal kingdom


• What are the early embryo stages of human development?

• What is it cleavage and does the cleavage of human embryo

have specific characteristics?

• What are the characteristics of blastomers?

• How does the human embryo look like after first

differentiation?

Development of humans

• Zygote - cleavage = the series of mitotic cell divisions that

produces a blastula from a fertilized ovum. It is the basis of

the multicellularity of complex organisms. I is a slow rate

division - between 12 and 24 hours

• Morula from blastomers, which are totipotent

• Polarization / animal vegetal pole

• Blastocyst (blastula with blastocoel for non-

mammalian) after differentiation, post-morula

stage, consisting of the trophoblast and an inner cell mass.

After 7 days, there is more than 100 cells

Early blastocyst. From Dorland's, 2000.


• What does a gastrula look like?

• What is it a gastrulation?

• What is an epiblast and what does it give rise to?

• What is a hypoblast and what does it give rise to?

Gastrulation

• Gastrula = stage following the blastula stage; the simplest type consists

of two layers of cells, the ectoderm and entoderm, which have invaginated

to form the archenteron and an opening, the blastopore. Thus, gastrulation

is process by which the bilaminar embryonic disk (Epiblast + Hypoblast) is

converted into a trilaminar embryonic disk.

Epiblast = the outer layer of a blastula that gives rise to the

ectoderm after gastrulation.

Hypoblast = cell layer adjacent to the yolk

sac cavity and subjacent to the epiblast of a

bilayered embryo.


• What is it primitive streak?

• What are the germ layers of human embryo?

Primitive streak An ectodermal ridge in the midline at the

caudal end of the embryonic disc from which arises the

intraembryonic mesoderm; achieved by inward and then lateral

migration of cells. The organizer is Hensen node

Germ layers: Ectoderm forms the outer layer of gastrula

Endoderm lines the digestive tract and

Mesoderm fills the space between the ectoderm and endoderm

Cells separate from the central part of the ectoderm and move

into the interior of the embryo, and become endodermal and

mesodermal cells.

Gastrulation in chicken, mammals


• What is it the function of amnion?

• What is the function of allantois?

• What is the function of chorion?

• What is the function of yolk sac?

Amniotic egg / reptiles, birds and mammals

Extraembryonic

membranes:

Amnion / protection

Allantois / wastes and

gas exchange

Chorion / gas

exchange

Yolk sac /nutrients


• What is the organogenesis?

• What are first primitive organs of human embryo and what do

they give rise to?

• What are somites?

Organogenesis - chordata

The formation and development of the organs.

Mechanisms of an origin of primitive organs from germ

layers are folds, clefts, dense clumps.

Neural tube - ectoderm – centre of nerve system, brain

and spinal cord

Notochord – mesoderm – backbone

Somites - mesoderm - a segmental mass of mesoderm,

occurring in pairs along the notochord and developing into

muscles and vertebrae

Illustration from

Anatomy &

Physiology,

Connexions

Web

site. http://cnx.

org/content/col

11496/1.6/, Jun

19, 2013.

http://cnx.org/content/col11496/1.6/




• What does ectoderm give rise to?

In vertebrates, the

ectoderm has three parts:

external ectoderm (also

known as surface

ectoderm),

the neural crest, and

neural tube.

The latter two are known

as neuroectoderm.


• What does mesoderm give rise to?

The body organs, tissues and systems derived from the

mesoderm:

• bones

• cartilage

• most of the circulatory system, including the heart and major

blood vessels

• connective tissues of the gut and integuments

• mesenchyme

• mesothelium

• muscles

• peritoneum (lining of the abdominal cavity)

• reproductive system

• spleen

• urinary system, including the kidneys

The following chart shows the products produced by the

endoderm.

Gastrointestinal tract

Respiratory tract

Endocrine glands and organs (liver and pancreas)

The endoderm

forms the epithelial lining of the entire alimentary canal

except part of the mouth, pharynx and the terminal part

of the rectum, the lining cells of all the glands which

open into the digestive tube, including those of the liver

and pancreas, the epithelium of the auditory tube and

tympanic cavity, of the trachea, bronchi, and alveoli of

the lungs, of the urinary bladder and part of the urethra,

and that which lines the follicles of the thyroid gland and

thymus.

Development of Human Embryonic Tissues.

(© 2001 Terese Winslow)

Campbell, Neil A., Reece, Jane

B., Cain Michael L., Jackson,

Robert B., Minorsky, Peter V.,

Biology, Benjamin-Cummings

Publishing Company, 1996 –

2010.

Thank you for your attention

Documents

Premedical Biology Individual development in humans