Fetal Growth and Development PDF

GROWTH AND DEVELOPMENT OF THE EMBRYO DR. PAUL A ODEY BSC., MBBS, MSC, PHD, LMIH  GROWTH Growth refers to an increase in physical size of the whole body or any of its parts. It is measurable physical changes that occur throughout a person’s life.  It is multiplic...

GROWTH AND DEVELOPMENT OF THE EMBRYO DR. PAUL A ODEY BSC., MBBS, MSC, PHD, LMIH  GROWTH Growth refers to an increase in physical size of the whole body or any of its parts. It is measurable physical changes that occur throughout a person’s life.  It is multiplication of cells commencing from fertilization to physical maturity. It can be measured in Kg, pounds, meters, inches.  DEVELOPMENT Development refers to the increase of functional capacity specialised tissues. Development is a measure of functional or physiological maturation of the nervous system. It signifies accomplishment of mental, emotional and social abilities. It refers to the changes in intellectual, mental and emotional skills that occur over time.  Principles of Growth & Development Cephalocaudal direction: The head region starts growth at first. The child gains control of the head, then the arms and then the legs. Proximodistal direction: From centre or midline to the periphery (Near to far). The spinal cord develops before outer parts of the body. The child’s arm developsnbefore the hands. The hands and feet develop before the fingers and toes.  Principles (Cont’d) 3. General to Specific direction: From genetic sounds emerge words and then specific sentences with meaning. Children first able to hold pencil, then draw cycle to writing letters after the words. 4. Differentiality: Development does not occur at an even pace. Individuals differ in the rate of growth and development. Boys and girls have different development rates. Each part of the body has its own particular rate of growth.  Principles (Cont’d) Influenced by environmental and genetic factor: Individuals work with and affect their environment, and in turn the environment works with and affects them. Predictability: Growth and development are predictable Simple to Complex: Proceeds in this manner Continuity: From conception to death (Womb to Tomb). From child to be an adult in respect of body size, functioning, behavior. Adulthood changes to old age. Then comes the death which ends the life cycle.  Factors influencing Growth & Development Genetic factors: Parental phenotype & familiar patterns, race and nationality, Sex, genetic disorder (Chromosomal/gene defects) Prenatal factor: Maternal nutrition, infection, substance use, illness, hormones.  Factors influencing (End) Postnatal factor: Growth potentials, nutrition, childhood illness, physical environment, psychological environment, cultural difference, socio-economic status, climate & season, play & exercise, birth order of the child, hormonal influence.  EMBRYONIC DEVELOPMENT Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~early stage of development of multicellular organism Includes: 1. cell division 2. cell growth 3. cell differentiation~changing of unspecialized embryonic cells into specialized cells, tissues,& organs  EARLY EMBRYONIC DEVELOPMENT Cleavage is the first major phase of embryonic development. It is the rapid succession of cell divisions (Mitotic) that creates a multicellular embryo from the zygote. NO growth Stages:1. Morula~solid ball of cells 2.Blastula~ single layer of cells surrounding a fluid-filled cavity called the blastocoel  2 cells  4 cells  8 cells  OTHER EMRYONIC DEV PHASES Gastrulation is the second major phase of embryonic development The cells at one end of the blastula move inward,It adds more cells to the embryo It sorts all cells into three distinct cell layers The embryo is transformed from the blastula into the gastrula  OTHER EMRYONIC DEV PHASES The three layers produced in gastrulationEctoderm, the outer layerEndoderm, an embryonic digestive tractMesoderm, which partly fills the space between the ectoderm and endoderm. ectoderm cells~ eventually they develop into the skin and nervous tissue of the animal. endoderm cells ~develop into the lining of the animal’s digestive tract and into organs associated with digestion. mesoderm cells ~develop into the muscles, circulatory system, excretory system, and, in some animals, the respiratory system.  OTHER EMRYONIC DEV PHASES Organs start to form after gastrulationEmbryonic tissue layers begin to differentiate into specific tissues and organ systems Changes in cell shape, cell migration, and programmed cell death give form to the developing animalTissues and organs take shape in a developing embryo as a result ofcell shape changescell migrationEctoderm  Development programmed cell death (apoptosis) Cell suicide Dead cell engulfed and digested by adjacent cellprogrammed cell death (apoptosis).  Embryonic induction initiates organ formation  Induction is the mechanism by which one group of cells influences the development of tissues and organs from ectoderm, endoderm, and mesodermAdjacent cells and cell layers use chemical signals to influence differentiationChemical signals turn on a set of genes whose expression makes the receiving cells differentiate into a specific tissue  STAGES OF FETAL GROWTH AND DEVELOPMENT The name change from embryo to fetus signifies that the embryo has developed into a recognizable human being and that the primordia of all major systems have formed. Development during the fetal period is primarily concerned with rapid body growth and differentiation of tissues, organs, and systems. Head hair usually begins to appear at 20 weeks and eyebrows and eyelashes are usually recognizable by 24 weeks. The eyes open at approximately 26 weeks. CRL, crown-rump length. (See drawings next) A notable change occurring during the fetal period is the relative slowdown in the growth of the head compared with the rest of the body. The rate of body growth during the fetal period is very rapid, and fetal weight gain is phenomenal during the terminal weeks. Periods of normal continuous growth alternate with prolonged intervals of absent growth.  ESTIMATION OF FETAL AGE 1. Ultrasound measurements of the crown- rump length (CRL) are taken to determine the size and probable age of the fetus and to provide a prediction of the expected date of delivery. 2. Fetal head measurements and femur length are also used to evaluate age. 3. Gestational age is commonly used clinically, and it may be confusing because the term seems to imply the actual age of the fetus from fertilization. It synonymous with last normal menstrual period (LNMP).  PREGNANCY TRIMESTERS First trimester, all major systemIn the second trimester, the fetus grows sufficiently in size so that good anatomic detail can be  visualized during ultrasonography. During this period,  most major fetal anomalies can be detected using  high-resolution real-time ultrasonography. By the  beginning of the third trimester, the fetus may survive if  born prematurely. The fetus reaches a major  developmental landmark at 35 weeks of gestation. It  weighs approximately 2500 g, which is used to define  the level of fetal maturity. At this stage, the fetus  usually survives if born prematurely.  MEASUREMENT OF THE FETUS Biparietal diameter (diameter of the head between the two parietal eminences) Head circumference Abdominal circumference Femur length Foot length  Viability of Fetuses Viability is defined as the ability of fetuses to survive in the extrauterine environment (i.e., after a premature birth). Fetuses weighing less than 500 g at birth usually do not survive. Many full-term, low birth weight babies result from intrauterine growth restriction (IUGR). Most fetuses weighing between 1500 and 2500 g survive, but complications may occur; they are premature infants. Prematurity is one of the most common causes of morbidity and perinatal death.  STAGES OF GROWTH The stages of growth have been classified in different periods: Prenatal Period: The prenatal period comprises on the average 9 calendar months or 40 weeks. Prenatal growth has three distinct stages: Fertilized ovum (egg), Zygote (first 2weeks); Embryo (from 2 to 8 weeks) Foetus (from 9 to 40 weeks).  STAGES OF GROWTH Postnatal Period: Postnatal growth is commonly divided into the following age periods:  Neonate (0-28days): During this period baby establish independent respiration and circulation.  Infancy (28days to 1year): This is a period of rapid growth in most bodily systems and dimensions and rapid development of the neuromuscular system.  STAGES (End) Early Childhood: 1-6 years Late childhood: 6-12 years Adolescence: 12-18 years Early Adulthood: 19-40 Years Middle Adulthood: 40-65 Years Late Adulthood: 65 Years and Older  Difference btw Growth & Development GROWTH DEVELOPMENT 1. Quantitative Qualitative 2. Comprises Height, Weight, Size, Cognitive, social & emotional Shape of body organs changes 3. It is due to cell divisions It is due to motor & adjustment in mental processes and their interplay. 4. It is for limited period (stop at It takes place till death maturation) 5. It can be measured It can be observed by matured behaviour 6.Individual differences exist Children differs in the level of development 7. Not affected by learning Learning and experiences affect 8. It is purely physical attributes It implies improved adapatation & functioning. THANK YOU FOR LISTENING