Embronic development for f.y

EMBRYONIC DEVELOPMENT

Ravi Ranjan & Gunjan MehtaDept. of Biotechnology

Spermatogenesis

Oogenesis

1st Week of Development

Fertilization

Cleavage

Blastocyst Formation

Implantation

Cleavage

Implantation of the

Blastocyst

SPONTANEOUS ABORTION (Miscarriage)

• Can occur for many reasons:• 1. Implantation did not occur (woman never knows

she’s pregnant)• 2. Not enough hCG (menses occurs)• 3. Developmental problem in fetus death in utero• 4. Not enough progesterone lining breaks down• 5. Improper implantation• 6. Improper placenta

Summary

• Cleavage is a series of mitotic divisions that results in an increase in cells, blastomeres,which become smaller with each division. After three divisions, blastomeres undergo compaction to become a tightly grouped ball of cells with inner and outer layers. Compacted blastomeres divide to forma 16-cell morula.

• As the morula enters the uterus on the third or fourth day after fertilization, a cavity begins to appear, and the blastocyst forms. The inner cell mass, which is formed at the time of compaction and will develop into the embryo proper, is at one pole of the blastocyst. The outer cell mass, which surrounds the inner cells and the blastocyst cavity, will form the trophoblast.

Summary

• The uterus at the time of implantation is in the secretory phase, and the blastocyst implants in the endometrium along the anterior or posterior wall. If fertilization does not occur, then the menstrual phase begins and the spongy and compact endometrial layers are shed. The basal layer remains to regenerate the other layers during the next cycle.

2nd Week of Development

Development of Trophoblast

Development of Bilaminar Embryonic disc

Development of Amnion

Development of Yolk sac

Development of Sinusoids

Development of Extra embryonic mesoderm

Development of Chorions

Bilaminar layer, Exocoelomic membrane & Amnion

Maternalsinusoid

Endometrium capillaries around the developing embro becomes dialted and reffered as Maternal Sinusoids.

Gastrulation

Neurulation

Development of Chorionic Villi

Development of Placenta

3rd Week of Development

3rd Week of Development

Gastrulation

Primitive Stalk formation

Primitive Node formation

Trilaminar Disk formation

Notochordal process

Notochord

Oropharangeal & Cloacal membrane

Trilaminar Disk formation

Differentiation of Primary Germ Layers (from the gastrula)

Ectoderm Mesoderm Endoderm

Nervous system Skeleton Digestive tract

Epidermis of skin Muscles, Dermis of skin

Respiratory system, Bladder

Ear, lens, cornea Circulatory system Liver, pancreas

Salivary & Pituitary gland

Gonads Epithelial lining of Cowper’s, parathyroid glands, pancreas

Caudal (posterior)

Surface Ectoderm

Hollow tube

3rd Week of Development

NeurulationEctodermal cell Notochord Neural plateMesodermal cell Notochord Vertebral bodies

Neural plate, fold, groove, tube.

Development of somitesMyotome- Skeletal muscle of neck, limbDermatome- Connective tissue, Skin dermisSclerotome- Vertebrate

Development of Intraembryonic Coelom

Development of Cardiovasular System

3rd Week of DevelopmentDevelopment of Chorionic Villi

Development of Placenta

Gestation period• During first trimester individual starts out as a zygote, then

morula, blastocyst, and after implantation, is called an embryo.• Embryonic phase of development lasts from fertilization until

the 8th week of gestation, when it becomes a fetus.• By day 35 the heart is beating, and eye and limb buds are

present.• By the end of the third month the placenta is functioning.• By month four, the rudiments of all organ systems are formed

and functioning, and from then on, fetal development is primarily a matter of growth.

Functions of the placenta:1 Transfer gasses

2 Transport nutrients

3 Excretion of wastes

4 Hormone production – temporary endocrine organ – estrogen and progesterone

5 Formation of a barrier – incomplete, nonselective – alcohol, steroids, narcotics, anesthetics, some antibiotics and some organisms can cross

Development of the Placenta

4th Week of DevelopmentOrganogenesis

Embryonic folding

Median plane- fold- Head fold, tail fold & Horizontal fold

Lateral fold- Fore gut, Mid gut, Hind gut

Otic placode- Internal Ear

Lens placode- Eyes

Pharangeal arch- Head & Neck

Embryonic Period 1st to 4th week, 5th to 8th week

Fetal Period

Human Fetus at

Ten Weeks

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