Gestation and Birth Viv Rolfe. Lecture Outline To investigate the major events of gestation and...
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Transcript of Gestation and Birth Viv Rolfe. Lecture Outline To investigate the major events of gestation and...
Lecture Outline
• To investigate the major events of gestation and parturition.
• What is implantation?
• 3 stages of gestation (germinal, embryogenic and foetal phases).
• Structure and function of the placenta and umbilical cord.
• 3 stages of parturition.
Gestation and Partition(Pregnancy and birth)
(280 days/9 months)
Development of the zygote / embryo / foetusin the female reproductive tract,
and delivery from the female.
The ZYGOTE rapidly divides into a mass of cells called the MORULA.
The cells DIFFERENTIATE (change type) forming the BLASTOCYST: Trophoblast – large fluid-filled sphere (foetal placenta)
Inner cell mass (embryo)
Cellular Changes
Blastocystcavity
6-8 days after fertilization the blastocyst implants into the uterine wall.
The endometrial glands start to enlarge and becomes more vascularised.
Implantation
What is the word for the implantation and
development of the embryo outside of the uterine cavity?
Ectopic pregnancy.
Inutero-development
Chorionic villi (Placenta)
Body Stalk (Umbilical cord)
Yolk sacEarly source of nutrients
Ectoderm
Mesoderm
Endoderm
(GERM LAYERS)
Weeks 1-8.
A time of rapid cell differentiation and growth.
All the body tissues and organs develop from the PRIMARY GERM LAYERS.
The placenta also begins to develop.
Embryonic Period
Ectoderm Nervous system
Epidermis of the skin
Eye, ear
Endoderm Mucosal surfaces
Glands
Mesoderm Skeletal, smooth and cardiac muscle.
Cartilage, bone, blood, lymphoid tissue.
Germ layers
Foetal Period
• Weeks 12-38.• The embryo is referred to as a
FOETUS.• It has a human appearance.• It now rapidly grows (from a few
cm to up to 50 cm), occupying all of the abdominal space.
Forms a barrier between mother and embryoto deliver NUTRIENTS and OXYGEN.
Removes WASTE from embryonic blood.
Becomes an endocrine organ by producing HORMONES (oestrogen, progesterone) to control pregnancy
Placenta
• 1st trimester (first 3 months)• Embryonic period - development of body organs
• Baby’s heart starts beating about 4 weeks.
Summary of the Stages of Pregnancy
• 3rd trimester – (months 7-9).
•2nd trimester (months 4-6)
•Foetal period – rapid growth and much activity.
Effects on the mother
Enlargements of the uterus
Gastrointestinal symptoms
Morning sickness is due to elevated progesterone
Heartburn due to organ crowding by the fetus
Constipation is caused by declining motility
Urinary System
Kidneys have additional burden and produce more urine
The uterus compresses the bladder
Effects on the mother
Cardiovascular system
Body water levels rise
Blood volume increases by 25 to 40 percent
Blood pressure and pulse increase
Varicose veins are common
Labour – the series of events that expel the infant from the uterus
Initiation of labor Estrogen levels rise
Prostaglandin starts uterine contractions
Birth - parturition
Dilation Cervix becomes dilated
Uterine contractions begin and increase
The amnion ruptures
Expulsion Infant passes through the cervix and vagina
Normal delivery is head first
Placental stage Delivery of the placenta
Labour
Effects of birth on the foetus
• The baby undergoes amazing physiological changes at birth.
• What happens?
Oxygen and nutrients no longer supplied by the mother.
Carbon dioxide and other wastes aren't eliminated by her.
Loss of protection from the uterus.
Temperature drop.
Exposed to microbes!
Rapid Changes in the Lungs
• Change from being fluid filled and collapsed in the uterus, to filled with air.
• Blood CO2 is high at birth stimulating the respiratory centre in the brain.
• The baby draws its first breath.
Rapid Changes in the Heart
• Closure of the foramen ovale in the heart (which doesn’t close in “hole in the heart baby’s”).
• This diverts de-oxygenated blood to the LUNGS and not to the PLACENTA.
• The umbilical artery and vein close down.
• There is rapid red and white blood cell production at birth.