Chapter 28

Question 1

Gestational Period

Answer 1

Time from last menstrual period until birth

Question 2

Embryo

Answer 2

Fertilization through week 8

Question 3

Fetus

Answer 3

Week 9 through birth

Question 4

Capacitated

Answer 4

Priming, motility must be enhanced, membranes must become fragile to release hydrolytic enzymes. Fluids in Female reproductive tract prepare for sperm

Question 5

5 Steps leading to a sperm entering an egg

Answer 5

1. ) Approach - weave passed granulosa cells of corona radiata.
2. ) Acrosomal Reaction - Binding of sperm to sperm-binding receptors on zona pellucida causes the Ca2+ levels to rise.
3. ) Binding - sperms membrane binds to oocyte’s sperm-binding receptors.
4. ) Fusion - The sperm and oocyte plasma membranes fuse, allowing sperm contents to enter oocyte.
5. ) Block of Polyspermy- Calcium is released, triggers cortical reaction, zona pellucida hardens and sperm receptors are clipped off.

Question 6

Steps leading to true fertilization

Answer 6

1. ) After the sperm penetrates the secondary oocyte, The oocyte Completes meiosis II, forming the ovum and second polar body.
2. )Sperm and ovum nuclei swell, forming pronuclei.
3. ) Pronuclei approach each other and mitotic spindle Forms between them.
4. ) Chromosomes of the pronuclei intermix. Fertilization is
   accomplished. Then, the DNA replicates in preparation for the first cleavage division.

Question 7

What is cleavage?

Answer 7

Miotic divisions of zygote while zygote moves toward uterus, first cleavage at 36 hours (2 daughter cells).

Question 8

Cleavage of cells

Answer 8

36 hours - 2 daughter cells
72 hours - Morula (16 cells)
4-5 days - Blastocyst (100 cells)
6-7 days - Implanting Blastocyst

Question 9

Events of Implantation

Answer 9

• 6-7 days after ovulation
• Trophoblast cells adhere to site with proper receptors and chemical signals and proliferate into cytotrophoblasts (inner layer) and syncytiotrophoblast (outer layer)
• Inflammatory-like response occurs in endometrium
• Blastocyst begins conversion to gastrula
• Inner cell mass develops into embryonic disc

Question 10

Cytotrophoblast

Answer 10

Inner layers of cells

Question 11

Syncytiotrophoblast

Answer 11

Cells in outer layers that start to invade and digest endometrium

Question 12

Blastocyst at implantation

Answer 12

burrows into lining surrounded by pool of leaked blood; endometrial cells cover and seal off implanted blastocyst

Question 13

What secretes hCG and what does it do?

Answer 13

Human Chorionic Gonadotropin, secreted by trophoblasts. Prompts corpus luteum to continue secretion of progesterone and estrogen which promotes placental development, HCG levels rise until end of 2nd month.

Question 14

Placenta

Answer 14

It is a temporary organ from embryonic and maternal tissues.
Maternal portion = Decidua Basalis
Fetal portion = Chorionic villi
Fully formed and functional by end of third month

Question 15

Roles of Amnion

Answer 15

Epiblast cells form transparent sac filled with amniotic fluid

• Provides buoyant environment that protects embryo
• Helps maintain constant homeostatic temp
• Allows freedom of movement, prevents parts from fusing
• Amniotic fluid comes from maternal blood and later fetal urine.

Question 16

Roles of Yolk sac

Answer 16

Forms part of digestive tube and earliest source blood cells and vessels

Question 17

What’s the allantois?

Answer 17

Small outpocket of yolk sac, base for umbilical cord and part of urinary bladder

Question 18

Chorion

Answer 18

Helps form placenta

Encloses embryonic body

Question 19

Neurlation

Answer 19

17 days - Flat 3-layered embryo has completed gastrulation, notochord, and neural plate are present
20 days - Neural folds from folding of the neural plate which deepens, 3 mesodermal layers form on each side
22 days - neural folds have closed forming tube, embryonic body is beginning to undercut.
4 weeks - Embryo undercutting complete (sclerotome, myotome, dermtome)

Question 20

3 vascular shunts in fetus

Answer 20

Ductus Venosus - Bypasses liver (umbilical vein - ductus venosus - IVC)
Foramen ovale - opening in interatrial septum; bypasses pulmonary circulation
Ductus arteriosus - bypasses pulmonary circulation (pulmonary trunk ductus arteriosus aorta)

Question 21

8 weeks

Answer 21

Limbs present, digits webbed, cardiovascular system fully functional, head nearly as large as body

Question 22

9-12 weeks

Answer 22

Sex readily detect, Retina of eye is present, Liver prominent and bile being secreted, blood cells formation begins in bone marrow

Question 23

13-16 weeks

Answer 23

Cerebellum becomes prominent, blinking of eyes, face looks human and body growth beginning to outpace head.

Question 24

17-20 weeks

Answer 24

Limbs reach near final proportions, quickening occurs, lanugo covers skin

Question 25

21-30 weeks

Answer 25

Myelination of spinal cord begins, eyes are open, skin is wrinkled and red, body is lean and well proportioned.

Question 26

30-40 weeks

Answer 26

Skin whitish pink, fat laid down in subcutaneous layer.

Question 27

Anatomical Changes of mother

Answer 27

Reproductive organs engorged with blood
Uterus expands, occupying most of abdominal cavity
Lordosis - curvature of spine
Relaxin causes pelvic ligaments and pubic symphysis to relax to ease birth passage
Weight gain

Question 28

Initiation of Labor

Answer 28

Fetal secretion of cortisol stimulates placenta to secrete more estrogen, causes production of oxytocin by myometrium which causes formation of gap junctions between uterine smooth muscle cells. Antagonizes calming effects of progesterone leading to Braxton Hicks contractions in uterus.

Question 29

Dilations Stage

Answer 29

6-12 hours
cervix effaces (softens) and dilates to 10 cm
Amnion ruptures, releasing amniotic fluid

Question 30

Expulsion stage

Answer 30

Full dilation to delivery, strong contraction every 2-3 min. urge to push increases, crowning, baby’s head extends as it is delivered

Question 31

Placental Stage

Answer 31

Strong contractions, detachment of placenta and delivery.

Question 32

What stimulates the first breath

Answer 32

CO2 stimulates respiratory control and takes a tremendous effort, tiny airways, lungs collapsed, surfactant helps reduce surface tension.

Question 33

Benefits of breast feeding

Answer 33

Fats and iron better absorbed, amino acids more easily metabolized. Immune system building, natural laxative encourages colonization of large intestine.