Pregnancy & Birth Flashcards
Functions of the Placenta: Endocrine
Secretes a # of hormones necessary for maintaining the pregnancy
Functions of the Placenta: Excretory
Transports nitrogenous wastes such as urea, uric acid, ammonia and creatinine from the foetal blood to the mother’s blood supply for excretion by the mother’s kidneys.
Functions of the Placenta: Immune
Transports antibodies from the mother into the foetal blood supply so that the foetus has immunity to some infectious diseases
Functions of the Placenta: Nutritional
Transports nutrients such as glucose, amino acids, fatty acids, vitamins and minerals from the mother’s blood to the foetal blood; stores some essential nutrients early in pregnancy and releases them later when the demand is greater.
Functions of the Placenta: Respiratory
Transport oxygen from the mother to foetus, and carbon dioxide from the foetus to the mother.
Insemination
When male ejaculates and the sperm are released in the vagina at the entrance of the uterus
The secondary oocyte is surrounded by what two layers?
Corona Radiata
Zona Pellucida
Corona Radiata
Outer layer consists of follicle cells held together by cementing materials that contain acid
Zona Pellucida
Inner layer is a glycoprotein matrix surrounding the plasma membrane of the oocyte.
What does the enzyme on the outer surface of the acrosome (sperm head) do?
Capable of breaking down the acid in the cementing material that holds the cells of the corona radiate together.
Causes digestive enzymes from the acrosome to be released when encountering the zona pellucida.
Outline fertilisation of the egg
Once the sperm has entered the oocyte the tail is absorbed and the head begins to move through the cytoplasm in the form of a male pronucleus - the haploid nucleus of the sperm.
The entrance of the sperm stimulates the oocyte to complete the second meiotic division.
The nucleus of the oocyte develops into a female pronucleus, which fuses with the male pronucleus to form a single nucleus that now has the diploid number of chromosomes.
Fertilisation is complete and the fertilised oocyte is a zygote.
Pregnancy
Period from conception to birth when a woman carries a developing foetus in her uterus.
Duration: 265 days
Zygote
Diploid cell resulting from the fusion of a sperm and an egg
Blastocyst
Hall ball of cells that surround a cavity filled with fluid
- The zygote travels down the uterine tube and begins to divide by mitosis.
By about 6 days after fertilisation, the zygote has developed into a blastocyst and reached the uterus.
- It has become a ball of rapidly dividing cells
When does HCG peak & what is its source?
Peak: 2nd Month
Source: Chorion
When does Progesterone peak & what is its source?
Peak: 9th Month
Source: Corpus luteum / placenta
When does oestrogen peak & what is its source?
Peak: 9th month
Source: Ovary / Placenta
When does prolactin peak & what is its source?
Peak: After Birth
Source: Pituitary gland
Embryonic period
First 2 months of pregnancy
Foetus
The developing individual
(Called that after the 2nd month)
What are the 3 Primary Germ Layers
Ectoderm
Mesoderm
Endoderm
Ectoderm
The outermost germ layer
Forms the outer layers of the body
E.g. skin, hair, mammary glands and nervous system
Mesoderm
Middle germ layer
Allows the formation of the stomach and intestines
E.g. skeleton, muscles, connective tissue, heart, blood & urogenital tract form
Endoderm
Innermost germ layer
Forms the lining of the digestive systems and lungs and thyroid
Amnion
1st membrane to develop
Surrounds embryo by 8th day of fertilisation
Enclosing a cavity, it secretes amniotic fluid
- Fluid protects the embryo against physical injust, acting as a shock absorber.
- Helps to maintain a constant temperature and allows the developing embryo to move freely.
Chorion
Form from outer cells of the blastocyst w/ a layer of mesodermal cells.
Surrounds embryo and other 3 embryonic membranes.
Amnion enlarges and fuses w/ inner layer of the chorion
Eventually becomes main of the foetal portion of the placenta.
Placenta outline
Forms from both foetal and maternal tissues during the first 3 months of gestation, with the foetal portion developing from part of the chorion.
Supplies nutrients to and remove wasters from the foetus.
Serves as an endocrine organ, producing a number of the hormones necessary to maintain pregnancy.
Gestation
Period of pregnancy
Embryonic period of an embryo
0-8 weeks
Embryonic period of a foetus
9-39 weeks
Outline the development of a one-month embryo
-Development of muscle segments on either side of the tube that is to become the brain & spinal cord.
- End of week 4 = 30 pairs of those muscle segments = beginning of the muscles & vertebrae of the spinal column.
- Brain, heart & liver begins to form & tail evident
Outline 5th week of development of an embryo
Arm & leg buds appear
Outline 8th week of development of embryo
Recognisably human form and all organs are present.
- Head half the size of embryo & eyes are slits
- Jaws, nose & ear lobes almost fully developed
- Arms & legs well proportioned & hands are formed.
- Toes & sexual organs evident
Outline 4th month (16 weeks) development of foetus
- Rapid growth
- Posture is more erect, fingerprints appear & foetus moves.
Mother:
- Posture is more erect, fingerprints appear & foetus moves.
- Uterus expand
- Woman’s abdomen begins to bugle
Outline week 20 of development of foetus
- Foetal movements - kicking & turning
Outline week 24 development of foetus
Mother shows obvious signs of pregnancy
Outline week 28 development of foetus
- Vigorous movements in uterus
- Brain enlarged & its surface is furrowed w/ developed function areas.
- If male - testes descend into the scrotum
Outline week 36 of development of foetus
- Circulatory system - fully developed
- Digestive system - needs time to mature
Outline week 40 of development of foetus
- Pregnancy - fufll term
- Foetal activity diminished
- Head is smaller in proportion to the body.
- Nose - well formed
Outline what the foetus does before birth
Changes its position in uterus & comes to lie with its head resting inside the curved shape of the pelvis.
Foetus growth is slow - placenta begins to fail (becomes more fibrous)
What are 3 changes in pregnant women?
- Abdomen bugles - internal organs are forced upwards & outwards
- Enlarged breasts - pregnancy hormones = development of milk-secreting tissue.
- Increased heart size and blood volume - caters for extra blood going to the placenta.
List the 3 stages of labour
Dilation
Expulsion
The placental stage
What is parturition
Process by which the foetus is expelled from the mother’s body at the end of gestation
It is preceded by a sequence of events - labour
Dilation
- Contractions force baby’s head into cervix, stretching until head enters the birth canal.
- Amnion bursts and releases amniotic fluid
Expulsion
- Baby moves into face-down position
- Contractions - stronger & closer together - forces baby through birth canal.
Placental stage
- Final contraction of uterus expelling the placenta, umbilical cord & membranes from mother’s body.
What do hormone changes do prior to labour?
- Causes pelvis ligaments to soften - more pliable
- Increase response of uterus to stimuli & strength contractions of its muscles.
What is the baby’s position prior to labour
Head settled in mother’s pelvis
Facing woman’s right or left hip bone w/ knees drawn up to its abdomen & legs crossed.
Ductus Venosus
Shunt that allows oxygenated blood in the umbilical vein, bypasses liver - essential for feotal circulation
Ductus Arteriosus
Vessel that bypasses the lung, allowing blood in the pulmonary artery to flow directly into the aorta.
Foramen Ovale
Hole between the left & right atria of the heart.
Beneficial - blood coming from placenta is highly oxygenated & can flow to the foetal tissues
