PHYSIOLOGY OF PREGNANCY, PROCESSAND CHARACTERISTIC OF HUMAN GROWTH AND DEVELOPMENT

 


PHYSIOLOGY OF PREGNANCY, PROCESSAND CHARACTERISTIC OF HUMAN GROWTH AND DEVELOPMENT

 PHYSIOLOGY OF PREGNANCY

•  Following ovulation the ovum which is about 0.15 mm in diameter, passes into the uterine tube and is moved along towards the uterus
•  The ovum has no power of locomotion so it is wafted along by the cilia and by the peristaltic muscular contraction of the tube.
•  The cervix under the influence of oestrogen secretes a flow of alkaline mucus that attracts the spermatozoa. During intercourse about 300 million sperm are deposited in the posterior fornix of the vagina. Those that reach the loose cervical mucus survive to propel themselves towards the uterine tubes while the remainders are destroyed by the acid medium of the vagina. More will die on the journey through the uterus and only thousands reach the uterine tubes where they meet the ovum usually in the ampulla.
•  It is only during this journey that the sperm finally become mature and capable of releasing the enzyme hyaluronidase which allows penetration of the zonapellucida and the cell membrane surrounding the ovum. Many sperms are needed for this to take place but only one will enter the ovum. After this the membrane is sealed to prevent entry of any further sperm and the nuclei of the two cells fuse.
•  The sperm and the ovum each contribute half the complement of chromosomes to make a total of 46. The sperm and ovum are known as the male and female gametes and the fertilized ovum as the zygote.
•  Neither sperm nor ovum can survive for longer than 2or 3 days and fertilization is more likely to occur when intercourse takes place not more than 48 hours before or 24 hours after ovulation. It therefore follows that conception will take place about 14 days before the next period is due.

 DEVELOPMENT OF THE FERTILIZED OVUM

•  Fertilized ovum continues its passage through the uterine tube and reaches the uterus 3 or 4 days later. During this time segmentation or cell division takes place the fertilized ovum divides into 2 cells then 4, then 8, 16 and so on until a cluster of cells is formed known as the morula (mulberry). These divisions occur quite slowly about once every 12 hours.
•  Fluid filled cavity or blastocele appears in the morula which now becomes known as blastocyst. Around the outside of the blastocyst there is a single layer of cells known as trophoblast, the remaining cells are clumped together at one end forming the inner cell mass.
•  The trophoblast will form the placenta and chorion while the inner cell mass will become the fetus, amnion and the umbilical cord. On its journey the ovum is nourished by glycogen from the goblet cells of the uterine tubes and later the secretary glands of the uterus.

THE EMBRYO

•   This is the developing offspring after implantation and until 8 weeks after conception.
•  During the embryonic period all the organs and systems of the body are laid down in a rudimentary form so that at its completion they have simply to grow and mature for a further 7 months.
•  The conceptus is known as the fetus.

 A SUMMARY OF DEVELOPMENT
THE FETUS-DEVELOPMENT

•  It is convenient to regard pregnancy as beginning at the Last normal menstrual period because this is usually the only definitive date available.
•  Some individual woman may know the exact date of conception.
•  For the first 3 weeks following conception the term fertilized ovum or zygote is used.
•  From 3-8 weeks after conception it is known as the embryo
•  From 8 weeks it is known as the fetus until birth when it becomes a baby.

 0-4 WEEKS AFTER CONCEPTION

•  Rapid growth
•  Formation of the embryonic plate
•  Primitive central nervous system
•  Heart develops and begins to beat
•  Limb buds form

4-8 WEEKS

•  Very rapid cell division
•  Head and facial features develop
•  All major organs laid down in primitive form
•  External genitalia present but sex not distinguishable
•  Early movements
•  Visible on ultrasound from 6 weeks

8-12 WEEKS

•  Eye lids fuse
•  Kidneys begin to function and the fetus passes urine from 10 weeks
•  Fetal circulation functioning properly
•  Sucking and swallowing begin
•  Sex apparent
•  Moves freely (not felt by mother)
•  Some primitive reflexes present

12-16 WEEKS

•  Rapid skeletal development- visible on x-ray
•  Meconeum present in gut
•  Lanugo appears
•  Nasal septum and palate fuse

 16-20 WEEKS

•  Quickening-mother feels fetal movements
•  Fetal heart heard on auscultation
•  Vernixcaseosa appears
•  Finger nails can be seen
•  Skin begins to be renewed

 
20-24 WEEKS

•  Most organs become capable of functioning
•  Periods of sleep and activity
•  Responds to sound
•  Skin red and wrinkled

24-28 WEEKS

•  Survival may be expected if born
•  Eyelids reopen
•  Respiratory movement

28-32 WEEKS

•  Begins to store fat and iron
• Testes descend into the scrotum
•  Lanugo disappears from face
•  Skin becomes paler and less wrinkled

32-36 WEEKS

•  Increased fat makes the body more rounded
•  Lanugo disappears from body
•  Head hair lengthens
•  Nails reach tips of fingers
•  Ear cartilage soft
•  Plantar creases visible

 36-40 WEEKS AFTER CONCEPTION (38-42 WEEKS AFTER LNMP)

•  Term is reached and birth is due
•  Contours rounded
•  Skull firm

CHARACTERISTICS OF GROWTH AND DEVELOPMENT

GROWTH AND DEVELOPMENT

•  Are terms often used interchangeably. Each depends upon the other and in a normal child they parallel each other, but the terms are not the same

GROWTH

•  Refers to an increase in physical size of the whole body or any of its parts and can be measured in centimeters and kilograms. (Weight and height)

                  o It causes quantitative change in a child’s body.
                  o The most common cause of concern is a sudden slowing not typical for the age in any  aspect of growth

DEVELOPMENT

•  Refers to a progressive increase in skill and capacity to function
•  Development is orderly, not haphazard; there is a direct relation between each stage and the next.

1.  Every child is an individual and should never be considered a typical boy or girl.
2.  Each child has his own rate of growth but the pattern of growth shows less variability.
3.  For example, the child will be able to sit before he can stand alone.
4.  The age at which a child as an individual achieves these skills may occur at any range of time.
5.  Although physical, mental social, emotional, sexual and spiritual growth and development proceed at different rates they are so interrelated in the majority of children that the result is progressive development of the whole child from infancy to adulthood.
6.  The child may appear abnormal when growth in any aspect is unusually slow or advanced.
7.  For example: A boy of 14 years with a height of 6 feet may appear physically as a man but emotionally, socially and intellectually he may achieve at a normal pubescent level. If the child is notably different from others of his age he may need help in order to make adjustment at home and community life regardless of the cause.
8.  A child with long term illness or a handicap of body or mind also differs from his peers and will need help.

 FACTORS INFLUENCING GROWTH AND DEVELOPMENT

•  HEREDITY

1.  Heredity determines the extent of growth and development that is possible but environment determines the degree to which the potential is achieved.
2.  The relatively typical pattern of growth and development is influenced by heredity and environment.
3.  The heredity of a man and a woman determines that of their children
4.  Before the largeness or smallness of a child is evaluated the size of the parents should first be observed.

•  SEX

1.  Sex is determined at conception.
2.  After birth the male infant is both longer and heavier than the female infant
3.  Boys maintain this superiority until 11 years of age.
4.  Girls mature earlier and reach the period of accelerated growth earlier than boys and then taller on the average
5.  During the pre-pubertal spurt of growth thereafter boys again are taller than girls
6.  The sex of children determines not only their physical attributes and patterns of growth but also the manner in which others react to them.
7.  In all cultural groups family and friends have different attitudes towards and expectations of a child dependent on the child’s sex

 RACIAL AND NATIONAL CHARACTERISTICS

•  RACE

1.  Distinguishing characteristics called racial or sub racial development in prehistoric humans
2.  As to height, tall and short examples exist among all races and sub races.
3. Among civilized groups intermarriage has produced mixed racial types.
4.  The racial factor has a great influence on height, weight, colour, features and body constitution. A child of white race will be white & tall even hair and eye colour, facial structure are governed by the same race.

•   NATIONALITY
•  ENVIRONMENT

1.  Although each human being at birth has a gene determined physical, mental and biochemical potential, the potential may not be reached because of the influences of the environment.
2.  The influence of heredity and environment are so interrelated that they are practically inseparable.

•  PRENATAL ENVIRONMENT

1. The influence of intrauterine environment on the child’s future development is great particularly since the uterus shields the fetus from the full impact of external adverse conditions.
2.  Harmful prenatal factors
3.  Insufficient mother’s diet in terms of quality and quantity
4.  Endocrine disturbances such as diabetes mellitus may affect the fetus
5.  Infectious disease may affect the child
6.  Radiation for cancer or any other condition may also affect the fetus
7.  Any infectious disease that a mother suffers during pregnancy may affect the fetus
8.  For example Rubella (German measles) during the first trimester may lead to abnormal development of the fetus
9.  Other infections that can affect the fetus include:

                  - Toxoplasmosis
                  - Syphilis
                  - Herpes
                  - Malaria
                  - HIV
     10. Rhesus incompatibility may cause erythroblastosisfetalis
     11. Faulty placental implantation or malfunction may lead to nutritional impairment
     12. Drugs, Smoking, Alcohol may lead to abnormalities or prematurity.

•   POSTNATAL ENVIRONMENT
•  EXTERNAL ENVIRONMENT

1.  CULTURAL INFLUENCES
2.  Social economic status of the family
3.  Nutrition.
4.  Climate and season
5.  Deviation from positive health for example Dwarfism
6.  Long term chronic illness
7.  Congenital anomalies (cardiac e.t.c)
8. Exercise
9.  Exercise by increasing the circulation promotes physiologic activity and stimulates muscular development.
10.  Fresh air and moderate sunshine favour health and growth.
11.  Ordinal position in the family
12.  The behaviour of the parents towards and their expectations of each child are different, yet predictable according to the child’s position in the family.
13.  The 1st born child in the family receives all the parental attention until the 2nd child is born.
14.  Parents may be overly concerned about care giving especially if they have the knowledge of growth and development. The child may therefore be raised rigidly and with anxiety.
15.  The child develops a more anxious perfectionist personality than do the later siblings and is more conforming, intelligent and achievement oriented.
16.  The 1st born may learn at an early age to control and organize behavior of others. The only child develops more rapidly. The middle child gets less attention from parents. The youngest child tends to be more peers oriented
17.  These generalizations apply to many children however each child is different

•   INTERNAL ENVIRONMENT

1.  Intelligence-this influences mental and social development.
2.  Hormonal influences
3.  The important hormones which affect growth are:
4.  Somatotrophic
5.  Thyroid
6.  Those that stimulate the gonads.
7.  Emotions
8.  Relationship with significant other persons
9.  Parents provides food, warmth, love, and protection as child develops
10.  Siblings are child’s earliest peers
11.  The way the child relates to playmates and classmates depends largely on the parent child relationship in the home. As the child grows other people such as teachers, neighbor’s shopkeepers have great influence on emotional, social and personality development.
12.  If the child is not given the necessary care and love that promotes healthy development growth and development are retarded

SUMMARY

•  Growth and development are terms often used interchangeably, they depend upon each other but they are not the same.
•  Human growth and development starts as soon as the male and female gametes fuse. Therefore there is growth and development which takes place when the fetus is in utero which continues when the child is born.
•  Human growth and development is influenced mainly by heredity and environment. There is prenatal and postnatal environment.
•  All children go through a normal sequence of growth but not at the same rate.
• Adults who have a clear understanding of the stages of growth and development can apply the knowledge when caring for children