Fetal Development Lecture Notes PDF

Fetal Development DEVELOPMENT OF FETUS ⦿ INTRODUCTION: ⦿ Life begins at the time fertilization of the ovum ⦿ The zygote formed is a single cell which develops into fully formed adult ⦿ Prenatal development is the process in which an embryo or fetus gestates during pregna...

Fetal Development DEVELOPMENT OF FETUS ⦿ INTRODUCTION: ⦿ Life begins at the time fertilization of the ovum ⦿ The zygote formed is a single cell which develops into fully formed adult ⦿ Prenatal development is the process in which an embryo or fetus gestates during pregnancy, from fertilization until birth. GESTATION PERIOD The gestation period of a) Germinal Period - This begins at fertilization and extends till the third week. b) Embryonic period – This extend from 4th ~ 8th week, involving changes in shape and external appearance. c) Fetal period – This extends from 3rd month up to termination of pregnancy. DEVELOPMENT OF SUPPORTIVE STRUCTURES OF FETUS & MAJOR EVENTS ⦿ Fertilization ⦿ Cleavage Division – The process of repeated mitotic division results in increase of number of cells ⦿ Cleavage give rise to blastomere. formation of morula and blastocyst ⦿ blastomere form compact ball called morula. The centre of morula is inner cell mass. ⦿ Blastocyst – The cells of morula continue to divide and forms blastocele. At this stage zygote is blastocyst. ⦿ Outer cell is trophoblast and inner cell mass is embryoblast. Implantation of blastocyst ⦿ Blastocyst attaches to endometrium and implantation takes place on 6th ~ 7th day after fertilization. Now Endometrium is ready to support the pregnancy, and is now referred as the decidua. ⦿ The Decidua ⦿ The corpus luteum continues to produce progesterone which stimulates secretery activity of endometrial glands ⦿ and increase the size of blood. ⦿ After implantation of the blastocyst the decidua is renamed as : i. Basal decidua – The decidua underneath the blastocyst. ii. Caspular decidua – It thin superficial layer covering the ovum. iii. Parietal decidua – the rest of decidua lining the uterine cavity outside the site of implantation. FANCTION OF DECIDUA ⦿ Functions ⦿ Provides bed for implantation ⦿ Supplies nutrition to early stage of growing ovum FORMATION OF GERM LAYER ⦿ This is first major event after implantation. ⦿ Three layers are formed – ⦿ Ectoderm – layer forms skin and nervous system. ⦿ Mesoderm – Layer forms bone, muscle, heart and blood vessel. ⦿ Endoderm – Forms mucus membrane and glands ⦿ The three layer together are known as embryonic plates. ⦿ Development of Placenta: ⦿ Placenta develops from two sources ⦿ - Fetal part ⦿ - Maternal part  PLACENTA ⦿ Functions and Roles of The Placenta ⦿ For nine months the placenta feeds and nourishes the fetus while also disposing of toxic waste. ⦿ The placenta is an extremely complex piece of biological equipment. It is a little bit like an artificial kidney. ⦿ This enables blood to pass across nutrients and oxygen to the baby, and waste products like carbon dioxide to go back from baby to mother. ⦿ It acts as the lung, kidney and digestive system for the baby.The placenta also performs the important function of protecting baby for possible infection ⦿ Amniotic fluid is a clear, slightly yellowish liquid that surrounds the unborn baby (fetus) during pregnancy. It is contained in the amniotic sac FUNCTIONS OF AMNIOTIC FLUID 1. Provides protection for embryo against shock, blow or pressure. 2. Embryo floats in the fluid. 3. It equalizes pressure 4. Allows fetal movement 5. Maintains constant temper Aids in effacement of cervix and dilation of uterine os. 6. Provides small amount of nutrient ⦿ The Fetal Circulatory System ⦿ During prenatal development, the fetal circulatory system is integrated with the placenta via the umbilical cord so that the fetus receives both oxygen and nutrients from the placenta. Other Organ Systems ⦿ During weeks 9–12 of fetal development, the brain continues to expand, the body elongates, and ossification continues. ⦿ Fetal movements are frequent during this period,. The bone marrow begins to take over the process of erythrocyte ⦿ The liver now secretes bile. The fetus circulates amniotic fluid by swallowing it and producing urine. The eyes are well-developed by this stage, ⦿ The fingers and toes begin to develop nails. By the end of week 12, the fetus measures approximately 9 cm. ⦿ Weeks 13–16 are marked by sensory organ development. The eyes move closer together. ⦿ The lips exhibit sucking motions. ⦿ the head The scalp begins to grow hair. ⦿ meconium, or fetal feces, begins to accumulate in the intestines. ⦿ During approximately weeks 16–20, as the fetus grows and limb movements become more powerful, the mother may begin to feel quickening, or fetal movements. ⦿ Developmental weeks 21–30 are characterized by rapid weight gain, which is important for maintaining a stable body temperature after birth. ⦿ The bone marrow completely takes over erythrocyte synthesis ⦿ Sebaceous glands coat the skin with a waxy, protective substance called vernix caseosa that protects and moisturizes the skin and may provide lubrication during childbirth. 23 WEEK ⦿ 33 weeks ⦿ In male fetus the testicles descend into the scortum. ⦿ Eyes are opened. ⦿ Week 35-40 ⦿ Fetus reaches a length of about 40-46 cm & weight is around 1,800-1,900 gms. ⦿ 37 Week Fetus is official full term. ⦿ Length reaches up to 42-48 cm. ⦿ 40 Week ⦿ Much of vernix has disappeared. 15 % of baby's body is fat. ⦿ Lungs will continue to develop until birth. ⦿ Fetus is 51cm &weight is around 3400 grams. ⦿ Any time & any day the fetus is delivered THANKS FOR ATTENTION