Premedical Biology

Individual development in

humans

Different types of cells have the same genetic

information, create different proteins as result of

regulatin of transcription.

Tissue specific proteins / determinated

[differentiated] cells

Maternal molecules in cytoplasm and local cell

signalling regulate transcription

General principles have being studied on model

organisms

Model organisms Drosophila melanogaster - fruit fly

Xenopus laevis - frog

Caenorhabditis

elegans – nematode

Mus musculus

Zygote / embryonal development means

cell division, cell differentiation and morphogenesis/

create a form

genetic information for many types of cells, for

threedimensional form / morfogenetic movements

1. Maternal determinants in egg:

protein molecules, RNA, mRNA….= cytoplasmatic

imformation molecules

Management

Cytoplasmatic determinants

2. Signal molecules/ induction

are coded of offspring genome,

Process is accomplished by chemical signals –

have target cells / local signalling

and cell surface interactions

- responsible of early diferentiation, early

development

Induction / signalling / regulation of gene expression

Positional information

• determine the location relative to body axes

and cell’s ability to respond to signals

• anteriorposterior and dorsoventral axe

is done by gradients of maternal morphogenes=

=products of genes, transcription factors

Group of genes

1. egg-polarity genes - bicoid

2. Gap genes

3. Pair-rule genes

4. Segment polarity genes

Homeotic genes / Homeobox

• identity of body parts

• evolutionarily highly conserved

HOX genes:

origin of transctiption factors with homeodomain

able to bind to DNA / switch on or off

Segmentation genes

Development

Zygote - cleavage

Morula - blastomers

Blastula / blastocoel / blastocyst

Gastrula – gastrulation

Organogenesis – primitive organs

Specific changes of shape, position and adhesion

Polarization / animal vegetal pole

Gastrulation

Epiblast - embryo

Hypoblast - yolk sac

Germ layers / invagination

Ectoderm – nervous system, skin

Endoderm – pancreas, epitels of digestive system

Mesoderm – kidneys, heart, muscle

ectoderm forms the outer layer of gastrula

endoderm lines the digestive tract and

mesoderm fills the space between the ectoderm and

endoderm

Gastrulation

Archenteron

Blastoporus

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 layersRadial

three germs layersSchizocoelomBilateralProtostomia / mouth from blastopore

Pseudocoelom

Coelom without segmetationCoelom with segmentationSegmentation homonomouslySedmentation herenomously

Deuterostomia / anus from blastopor, mouth secondarily

Animal kingdom

Body cavity

Space between

digestive tract

and

outer body wall

Organogenesis - chordata

Primitive organs from germ layers

folds, clefts, dense clumps – mechanisms

Neural tube - ektoderm – centre of nerve

system, brain and spinal cord

Notochord – mesoderm – backbone

Somites - mesoderm - the muscle segments

arrange along each side of notochord

notochord

neural tube

somites

archenteron

Primitive streak “blastoporus”

a rapidly proliferating mass of cells that spreads

between the ectoderm and endoderm, giving rise

to the mesoderm layer.

Gastrulation Chicken, mammals

Amniotic egg / reptiles, birds and mammals

Extraembryonic

membranes:Amnion / protection

Allantois / wastes

and gas exchange

Chorion / gas

exchange

Yolk sac

Human embryo

a slow rate of division - between 12 and 24 hours

Blastocyst – 7 days, more than 100 cells

Trofoblast – placenta

Primitive streak

Ectoderm: nervous system and epidermis

Endoderm: digestive tract and associated organs

Mesoderm: kidney, heart, muscles, inner layer of

skin

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.

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 (which are lined by involutions of the

ectoderm), 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.

• Sensory organs

• Cuticle [skin] of more levels and with derivatives

• Special blood cells carry oxygen, closed circulatory system

• Pairing kidneys of mesoderm origin

• Nervous system and system of glands of internal secretions

operate all life functions

• Ability to deposite of molecules of high energy

- Land vertebrate have egg with

amniotic sac and allantois,

Agnatha and Gnathostomata from pharyngeal slits

• Mammals, birds, reptiles, amphibians, classes of fishes

Vertebrates

Mammalia

Perfect thermoregulation - adaptation to fluctuating

tamperatures

Cornification of skin, hair

Epidermic glands, lactic, milk glands

Two-generation set of teeth

Two atrias, two ventriculi, left alveolar arch

Non-nucleated erythrocytes

Diaphragma

Placenta / placental mammals and marsupials

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