ugarit
عضو متقدم
المشاركات: 504
الانضمام: Aug 2008
|
RE: ولقد خلقنا الانسان من سلالة من طين
نعم شاهدته
الكتور كيث ل.مور عمل في جامعة الملك عبد العزيز في جدة ....لا عجب يعني !! سواء تاثره بالجو الاسلامي العام في السعودية او تاثره بالجو الدولاري السعودي !!
http://en.wikipedia.org/wiki/Keith_L._Moore
المراحل الاولى من تكون الجنين بغوغلة سريعة.. عل الماشي يعني
اقتباس:The embryo is not simply a set of instructions for making a new human being, like a blueprint for building a house. A blueprint is inert and cannot carry out instructions, but the embryo is active and begins work at once. A house needs builders, carpenters, electricians and plumbers to complete it; but the embryo has the ability to grow spontaneously, moving on to other phases of development and constructing the skeleton, flesh, nerve connections and a waste disposal system of the human body. After a house is built, a blueprint remains separate; but the embryo - already an essential human by virtue of the genes - is blueprint, builder and "house" together.
Implantation
After fertilisation the single cell splits into two, then the two cells double to four, four to eight, eight to sixteen and so on. Because the cell cluster looks superficially like a berry it is called the morula (Latin for "mulberry"), but the new life is always biologically human (species Homo sapiens).
The journey along the Fallopian tube continues slowly for about four days. Growth increases. By the time the womb cavity is reached, the cell cluster becomes hollow and fluid-filled, and is referred to as the blastocyst. However, this is not an inert clump of cells but a busily developing human individual: differentiation (organisation into different parts and functions) is already taking place. Meanwhile the uterus is forming a spongy lining within which the embryo will implant. To achieve this the embryo burrows into the wall of the womb and is covered over by the lining of the womb. This begins 6 days after fertilisation and is completed within the next 7 days.
If fertilisation has not taken place, the lining of the uterus comes away at the end of the monthly cycle as the woman's menstrual period. But once implantation occurs, the embryo sends out a hormonal signal which prevents the mother's period. This is usually her first indication of pregnancy.
Estimating length of pregnancy
Generally a woman does not know the exact date of her baby's conception. When she misses a period she may take a pregnancy test; she should see a doctor promptly to obtain professional care for herself and her child. The doctor takes the date of the first day of the mother's last menstrual period as the starting-point for a 40-week pregnancy. This gives the baby's gestational age. However since fertilisation only occurs when the ovum is released from the ovary, some two weeks from the beginning of the last period, the baby's actual (conceptional) age is also two weeks less. Full-time delivery occurs 38 weeks after fertilisation, but 40 weeks after the mother's last menstrual period. (In this booklet all developments of the embryo and foetus are dated from the time of conception, or fertilisation unless stated otherwise.)
Protection and life support
During and after implantation the embryo develops a protective, fluid-filled capsule which surrounds and cushions the developing body to prevent injury. Embryo and fluid are enclosed in two membranes, an inner amnion and an outer chorion. The chorion is covered in rootlike tufts, some of which form the early placenta - an organ made by the baby and the mother which transfers nutrients from the mother's bloodstream and removes waste products from the child's, though mother's and baby's circulatory systems remain separate. The placenta also produces hormones to maintain the pregnancy. In the ninth month it will alter the mother's hormonal balance and triggers off the birth process - although we are still unsure what causes labour to begin.
The baby is connected to the placenta by the umbilical cord, the lifeline channelling nourishment in and taking wastes out, which will be cut close to the baby's abdomen at birth and will leave the mark of the navel. During pregnancy the baby obtains oxygen from the mother's blood via cord and placenta, so does not drown in the surrounding fluid.
Body development
By 25 days from fertilisation the body is developing. Head and trunk appear and tiny arm buds begin to form, followed by leg buds. The early embryo seems to have a "tail", but this is really a protective covering for the spinal cord. Because the central nervous system (brain. spine and spinal cord) is so important, governing sensory and motor functions, the embryo's body is designed for rapid growth of head and back.
By 21 to 25 days the baby's heart is beating. Other internal organs are present in simple form and functioning as they grow. Early facial features appear. The doctor who performed the first-ever blood transfusion to an unborn baby has described the embryo at the end of the first month from fertilisation:
"By 30 days, just two weeks past mother's first missed period, the baby - one quarter of an inch long - has a brain of unmistakable human proportions, eyes, ears, mouth, kidneys, liver, an umbilical cord and a heart pumping blood he has made himself."3
The second month
Growing
The embryo increases in size from 5mm at four weeks to 4Omm by the end of the eighth week. The baby in the womb is usually measured from the top of the head to the bottom of the spine (crown-rump lengths).
Hands and feet
By the sixth week from fertilisation tiny fingers appear, followed within days by the toes. By the seventh week the baby has individual fingerprints; no two sets of fingerprints are ever the same. Even in utero the baby has unique characteristics.
Eyes and ears
By six weeks the eyes which appeared in simple form in the first month develop lens and retina; the eyelids start to take shape.
The ears continue to develop: by seven weeks the outer ear is present, and the inner ear, with its hearing and balancing mechanisms, is well established (see page 15 'Hearing')
Movements
Spontaneous movements begin at seven weeks:
"By 45 days, about the time of the mother's second missed period, the baby's skeleton is complete in cartilage, not bone, at first; ... he makes the first movements of his body and new-grown limbs, although it will be another 12 weeks before his movements are strong enough to be transmitted through the insensitive uterus to be detected by the mother's sensitive abdominal wall."4
Brain function
Brain waves have been recorded by EEG (electro- encephalograph) in the human embryo 40 days after fertilisation.5
Response to touch
Human embryos of five weeks gestational age have been seen to move away from an object touching the mouth area. The sensitive area extends to include the rest of the face in the sixth and seventh weeks and the palms of the hands and soles of the feet in the eighth and ninth weeks respectively.6
A British study shows that the baby's movements begin at the same time as sensory nerves begin to grow into the spinal cord in the second month of pregnancy; the nerve fibres respond to touches to the skin and movement of the limbs: at this stage the baby's sensory nerves "appear to be more sensitive than those of the adult or newborn baby."7
From embryo to foetus
Around eight weeks the baby's cartilage skeleton begins to turn into bone. The body is essentially complete. Now the baby can be referred to as the foetus - a Latin term meaning "young, offspring." Latin- or Greek-derived names are given to human beings at successive phases of development, e.g. "zygote" for the newly-conceived, "neonate" for newborn baby, "adolescent" for growing-up teenager, "geriatric" for a pensioner. These terms simply identify different stages in the human
.
http://www.spuc.org.uk/ethics/abortion/h...evelopment
سلملي على الدكتور كيث ل.مور
تحية
|
|
01-31-2010, 09:43 PM |
|
{myadvertisements[zone_3]}
{myadvertisements[zone_3]}
{myadvertisements[zone_3]}
|