1. PREGNANCY
Prof. Aziza Tosson

2. Outline Fertilization Development before Birth Embryonic Development
Fetal Circulation
Embryonic Development
Fetal Development
Birth

3. Conception
A secondary oocyte can be fertilized for about 24 hours after ovulation
Sperm remain viable for up to 48 hours within the female reproductive tract
This gives a three day “window” for intercourse to result in fertilization: two days before to one day after ovulation

4. Fertilization Steps of fertilization (Conception).
Several sperm penetrate corona radiata.
Several sperm attempt to penetrate zona pellucida.
One sperm enters egg and nuclei fuse, producing a zygote.
Egg’s plasma membrane and zona pellucida change to prevent polyspermy.

5. Fertilization

6. Fertilization usually takes place in the outer one-third of the uterine tube, but can take place in the abdominal cavity
Sperm swim up the female reproductive tract, aided by muscular contractions of the uterus stimulated by prostaglandins in the semen.
The oocyte may also secrete a chemical that attracts sperm

7. Occurrence of Pregnancy
When a zygote begins dividing, it is termed an embryo.
Developing embryo travels down oviduct and eventually implants in endometrium. (Implantation / pregnancy)
Presence of human gonadotropic hormone (HCG) in the blood confirms pregnancy.
If implantation does not occur, a woman never knows fertilization took place.

9. Human Development before Implantation

12. Zygote undergoes rapid mitotic cell division, but these do not increase the size of the zygote – called cleavage divisions
Cleavage produces a solid sphere of cells, still surrounded by zona pellucida – now called a morula.
At 4.5 to 5 days, cells have developed into a hollow ball of cells – blastocyst.
It is at this stage that it enters the uterus.

13. Cellular differentiation
Embryonic membranes
Amnion – inner layer
Chorion – outer layer
Both membranes form bag of waters
Amniotic fluid
cc normal
< 400 ml oligohydramnios
> 2000 ml polyhydramnios
Fetus contributes to amniotic fluid volume thru fetal urine
Amniotic fluid important for fetal lung development
As the cells differentiate, other structures begin to form. We have already mentioned the embryonic membranes.
The amniotic fluid helps to cushion ag injury, control the embryo’s temp, and assist in g&d of fetus allowing for movement and musculoskeletal dev. It is usually cc in volume – see others.
Wajed Hatamleh RN, MSN, PhD. 13

14. Cellular differentiation
Umbilical cord
Wharton’s jelly
2 arteries/ 1vein
Placenta
Site of metabolic and nutritional exchange
Maternal side – decidua basalis
Fetal side – amnion
15 – 20 cotyledons: contain the complex vascular system of villi
An umbilical cord forms that assist with the transport of nutrients and oxygen between the fetus and mother.see above.
The placenta develops at the site of implantation and serves a primary site of metab and nutri exchange. The decidua basalis is the part of the endometrium that is under the implanted blastocyst.
The cotyledons contain the complex vascular system of villi that support the growing fetus.
Cotyledons – subdiv of plac of villi and decidua tissue
Wajed Hatamleh RN, MSN, PhD. 14

15. Wajed Hatamleh RN, MSN, PhD.

16. Implantation
The blastocyst remains free in the uterus a short time, during which the zona pellucida disintegrates.
Blastocyst nourished by glycogen from glands of the endometrium.
At about 6 days after ovulation blastocyst implants – orients cell mass toward endometrium, and secretes enzymes which allow it to penetrate (digest) the endometrial wall. This nourishes the blastocyst for about a week after implantation.

17. Following implantation, the placenta
originates from maternal and fetal
tissues.
Placenta then produces human chorionic
gonadotropin (HCG) which maintains the
corpus luteum in the ovary until the
placenta begins its own production of
progesterone and estrogen.
Physical signs of pregnancy include : no
menstruation, increased urination,
morning sickness, increased size of
breasts, and darkening of areolae.

19. As early as days after fertilization, the blastocyst begins to secrete human chorionic gonadotropin or hCG.
hCG keeps the corpus luteum active until the placenta can produce estrogens and progesterone.
The presence of hCG is the basis for pregnancy tests.

21. Inner cell mass forms two cavities:
The yolk sac
Amniotic cavity
In humans the yolk sac produces blood cells and future sex cells
The amniotic cavity becomes the cavity in which the embryo floats. Fluid is produced from fetal urine, and secretions from the skin, respiratory tract, and amniotic membranes.

22. Gestation period Divided into three trimesters.
During first trimester individual starts out as a zygote, then morula, blastocyst, and after implantation, is called an embryo.
Embryonic phase of development lasts from fertilization until the 8th week of gestation, when it becomes a fetus.
By day 35 the heart is beating, and eye and limb buds are present.

26. Five-Week-Old Embryo

27. Fetus at 14 and 20 weeks gestation
Fetus at 14 and 20 weelks
Wajed Hatamleh RN, MSN, PhD. 27

28. By month four, the rudiments of all organ systems are formed and functioning, and from then on, fetal development is primarily a matter of growth.
By the end of the third month the placenta is functioning.

29. Three-to-Four Month-Old Fetus

30. Fifth through Seventh Months
Mother begins to feel fetal movement.
Wrinkled skin covered by fine hair, lanugo, is covered by a greasy substance vernix caseosa.
Lungs lack surfactant so if baby is born prematurely it will have to be on a respirator (respiratory distress syndrome).

31. Six-Month-Old-Fetus

33. The placenta The chorion develops into the fetal part of the placenta.
The chorionic villi connect the fetal circulation to the placenta
Composed of both fetal and maternal tissues

35. Functions of the placenta:
1 Transfer gasses
2 Transport nutrients
3 Excretion of wastes
4 Hormone production – temporary endocrine organ – estrogen and progesterone
5 Formation of a barrier – incomplete, nonselective – alcohol, steroids, narcotics, anesthetics, some antibiotics and some organisms can cross

36. Wajed Hatamleh RN, MSN, PhD.
Placental functions
Simple diffusion - water, oxygen, carbon dioxide, sodium and chloride
Facilitated transport – glucose and galactose
Active transport – amino acids, calcium, iron, iodine, vitamins, and glucose
Pinocytosis – albumin and gamma globulin
Hydrostatic and osmotic pressure
Endocrine – hCG, hPL, estrogen and progesterone
All of these functions take place in the placenta to assist the nutrition and oxygenation of the developing embryo and fetus. Do not memorize these specific processes but read the slide and be aware of the many functions of the developing placenta.
Wajed Hatamleh RN, MSN, PhD. 36

38. HORMONES OESTROGEN Produced in corpus luteum
Produced by placenta after 12 weeks
Responsible for growth particularly of uterus and breasts

39. progesterone Produced in corpus luteum and then the placenta
Relaxes smooth muscle
Inhibits uterine contractions until uterus is prepared for labour
Regulates storage of body fat

40. Human chorionic gonadotrophic
Secreted from trophoblast of the developing embryo
Maintains corpus luteum until placenta takes over
Used in tests to confirm pregnancy

41. Human placental lactogen
Alters maternal metabolism
Diverts glucose to fetus
Mobilises free fatty acids from maternal stores

42. RELAXIN Released by corpus luteum then the Placenta
Softens pelvic ligaments
Reduces myometrial tone