pregnancy hap 2

Question 1

 Capacitation

Answer 1

– even if a sperm reaches an oocyte within a few minutes of ejaculation, they must wait for capacitation to occur. Over 2-10 hours, sperm motility is enhanced, outer membranes around head become loose so that acrosomal enzymes can be released.

Question 2

 Acrosomal reaction

Answer 2

– sperm breaks through corona radiata (outer layer of of cells around ovum) then binds to sperm-binding receptors in the oocyte zona pellucida (glycoprotein layer) layer, calcium (Ca2+) levels in sperm rise, and then the sperm releases its acrosomal enzymes to digest a hole through the zona pellucida layer to get to the oocyte membrane. The sperm then binds with a sperm–binding receptor and most importantly, the sperm nucleus enters the oocyte.

Question 3

 Block to polyspermy

Answer 3

– means blocking entry of more than one sperm into a human oocyte as only 23 chromosones are needed. First, the oocyte membrane sheds its other sperm-binding receptors. Next, levels of Ca2+ rise in the oocyte cytoplasm. The elevated Ca2+ causes cortical granules to merge with the cytoplasm membrane. The zona pellucida layer above is hardened and sperm-binding receptors in the zona pellucida are removed.

Question 4

 Fertilization

Answer 4

occurs if Oocyte completes meiosis II, forming ovum & second polar body
Sperm nuclei and ovum nuclei swell into pronuclei
DNA replicates, pronuclei come close to each other, their membranes rupture and the maternal and paternal chromosomes combine together producing a diploid zygote
Fertilisation now completed, the zygote is ready to undergo first mitotic division of cleavage

Question 5

 Cleavage – from zygote to blastocyst

Answer 5

• can occur if fertilisation occurs within 24 hours
• 36 hours after fertilisation the zygote will undergo its first cleavage into two identical daughter cells called blastomeres.
• 72 hours later a berry shaped cluster of cells (morula) forms and passes along the uterine tube towards the uterus
• day 4 the morula hollows out and fills with fluid forming the blastocyst.
• Around day 7 the blastocyst inner cell mass is surrounded by trophoblast cells attaches to the uterine endometrium.
• by day 12 implantation completed
• The inner cell mass becomes the embryo and the trophoblast cells form the placenta

Question 6

function of the following female genitalia during pregnancy

Answer 6

Ovaries – corpus luteum producing estrogen and progesterone up until approximately week 12
Cervix – Mucus plug forms as a barrier against microbes
Uterus - will enlarge under the influence of estrogen and progesterone to accommodate fetal growth, and muscle layer contracts during labour to deliver the fetus

Question 7

placenta

Answer 7

transports nutrients to the fetus, transports waste products away from the fetus. The placenta has an immunological role to ensure the mother does not reject the fetus. Lastly, the placenta produces hormones during pregnancy e.g. estrogen, progesterone, hPL, ..

Question 8

Estrogen –

Answer 8

from Ovarian follicle & corpus luteum and after 12 weeks by the placenta. Stimulate growth of reproductive organs & breasts, promotes the proliferative phase of uterine cycle, development of secondary sexual characteristics, stimulate capacitation of sperms. Stimulates growth of the uterus and breasts during pregnancy.

Question 9

 Progesterone

Answer 9

from corpus luteum and after 12 weeks by the placenta. Acts with estrogen in stimulating growth of breasts, promotes the secretory phase of the uterine cycle. According to Stables & Rankin (2011, p. 162), progesterone has a sedative effect on the uterine muscle contractility.

Question 10

 Human chorionic gonadotrophin (hCG)

Answer 10

• produced approximately day 9 onward by trophoblast cells / developing placenta and by the embryo up to 9 weeks into pregnancy when production tails off rapidly. hCG ensures the ovaries (corpus luteum) produce estrogen and progesterone until placenta takes over this role around 12 weeks into pregnancy. The hCG can be detected in maternal urine by pregnancy tester.

Question 11

Prolactin

Answer 11

helps prepare the breasts for lactation and increases milk production in response to a suckling after the baby is born

Question 12

 Relaxin -

Answer 12

stimulates uterine growth, stops /restrains uterine muscle contraction during pregnancy, helps cervix soften before labor and helps the cervix efface during labor.

Question 13

 Inhibin -

Answer 13

inhibits secretion of the Follicle Stimulating Hormone (FSH)

Question 14

Oxytocin –

Answer 14

during the final stage of labour, the stretching cervix stimulates release of oxytocin from mother’s posterior pituitary. Oxytocin stimulates uterine muscles to contract and will stimulate placenta to release after the birth. The suckling infant triggers the hypothalamus to send efferent impulses to posterior pituitary to release oxytocin which triggers the breasts to release milk

Question 15

 Human placental lactogen (hPL) –

Answer 15

secreted by the growing placenta, works with estrogen & progesterone to prepare breasts for lactation, growth of fetus, glucose sparing = mother uses more fatty acids and less glucose. Thus, glucose is able to be used by the fetus.

Question 16

o Chloasma / pregnancy mask

Answer 16

• increases skin pigmentation, especially on the face (caused by  estrogen &  progesterone stimulating the anterior pituitary to produce melanocyte-stimulating hormone)

Question 17

Chadwick’s sign –

Answer 17

bluish-purple cervix and vagina on visual examination

Question 18

Linea nigra –

Answer 18

pigmentation of lower abdominal midline pigmentation of lower abdominal midline

Question 19

Breast enlargement

Answer 19

– preparation for lactation/breast feeding

Question 20

Growth of the uterus –

Answer 20

to accommodate growing fetus

Question 21

Lordosis –

Answer 21

sway back as growth of the fetus and enlarging uterus & placenta

Question 22

Waddling gait –

Answer 22

to accommodate abdominal enlargement Occurs as pelvic ligaments and joints are loosened by the placental hormone relaxin

Question 23

varicose veins and leg edema

Answer 23

pressure on iliac veins

Question 24

Why is the B vitamin folic acid needed, prior to and during pregnancy?

Answer 24

Answer – essential for development of erythrocytes, health of the nervous system, and fetal development. Strong protective effect against neural tube defects.

Question 25

Physiological changes

• Cardiovascular
• urinary
• digestive

Answer 25

• increase in blood volume by as much as 30-50%
• blood pressure variations
• slight decrease in systolic BP and greater decrease in diastolic BP thought to be due to hormonal vasodilation,
• increased renal function and more urination + pressure put on bladder.
• Digestive, morning sickness, heartburn, constipation.

Question 26

Physiological changes- respiratory

Answer 26

• nasal stuffiness – nasopharynx more oedematous increased mucus due to estrogen, with nose bleeds
• increase in tidal volume during pregnancy – because diaphragm raised, rib cage flares outward and upward, and tidal volume increases from normal 500 ml to 700ml
• decrease in residual volume
• dyspnoea in the later stages of pregnancy – due to enlarged uterus pushing upward under the diaphragm

Question 27

metabolic changes

Answer 27

+ metabolic rate

• effect of hPl, estrogen and progesterone on glucose and fat metabolism to stimulate breast maturation for lactation a fetal growth
• increased pTh and active vit D which leads to positive Ca+ balance.

Question 28

ovarian cycle

Answer 28

• FSH stimulates development of folicle in ovary
• folicle secretes estrogen and inhibin
• estrogen causes build up of endometrium and and stimulates secretion of inhibin and inhibiting FSH
• estrogen levels peak- stimulating LH secretion
• LH stimulates ovulation and corpus luteum formation
• corpus luteum releases estrogen, progesterone and -progesterone causes increased build up of endometrium and inhibits secretion of inhibinand inhibing FSH when there levels get low corpus luteum released
• causes decrese in progesterone and estrogen- menes