Reproductive System Part 2

Question 1

Developmental biology

Answer 1

Terms:
Conception -> fertilization

Embryology -> early developmental events (conception - 8 weeks)

Fetal development -> week 9 - term (birth)

Pre fertilization -> 6-8 hours - weakening of the acrosomal membranes

Question 2

Acrosomal reaction

Answer 2

See note picture *

Acrosomes break open (takes a lot of sperm

One cell goes through -> loses outercell membrane
-> becomes male pro nucleas

Oocyte loses cell membrane
-> becomes female pro nucleas

Female and male pro nuclei combine to form zygote nucleas (2n)

Question 3

Early cell division

Answer 3

Cleavage divisions*

• early mitotic cell divisions that result in increasing numbers of smaller cells with no increase in total volume

Question 4

Cleavage divisions

Answer 4

1st - 36 hours -> 2 cells - blastomere

2nd - 48 hours -> 4 cells

3rd - 60 hours -> 8 cells

4th - 72 hours -> 16 cell solid ball - morula

** all happen in Oviduct **

*** fertilization must happen in Ampulla of Fallopian tubes (oviducts)

Question 5

Parturition

Answer 5

Positive feedback

Pic in notes*

Sensory receptors that detect cervical distortion (compression, stretch)
—send afferent neuron to—>

Hypothalamus
—>
Stimulates posterior pituitary gland

Posterior pituitary gland
—after cervical distortion—>
—> releases a blast of oxytocin—>
—> stimulates uterine contraction
—> pushes fetus into cervix
—> restarts feedback loop***

Question 6

Phases of labor (stages)

Answer 6

Dilation

Expulsion

Placental

Question 7

Stages of labor (dilation)

Answer 7

1.) dilation —> 1st “true” contraction to 10 cm dilation

• longest phase (> 6 hours)
• amnion ruptures
• effacement - flattening out of cervix
• engagement - fetal head - pelvic inlet

Question 8

Stages of labor (expulsion)

Answer 8

Birth

• crowning -> head visible in birth canal

Question 9

Stages of birth (placental)

Answer 9

10-15 min contractions continue

Inspection - pulls cord

Question 10

Vertex

Answer 10

Head first - head first

Question 11

Breech

Answer 11

Butt first
- cesarian -> surgical removal through abdominal way

• episiotomy -> surgical widening of birth canal

Question 12

Twins

Answer 12

Monozygotic

• identical twins
• 30% of twin births

Dizygotic

• two oocytes - fertilized by two different sperm
• fraternal twins - 70%

Question 13

Lactation

Answer 13

Placenta secretes

• estrogen
• progestins
• placental lactogen
• placental prolactin

** all stimulate alveolar development

Moms hypothalamus
—secretes prolactin releasing hormone on->
Moms anterior pituitary gland
—secretes prolactin —>
Stimulates alveolar development

Increased estrogen and progesterone inhibit production of milk

Loss of placenta ->
- decreases est and prog
—> milk synthesis

Milk synthesis
- first two days.. not milk, but colostrum

Colostrum:
- less fat
- more protein
-proteins -> antibodies -> passive
immunity

Question 14

Control of lactation

Answer 14

Milk let down reflex

Sucking stimulus on nipple
—detected by tactile receptors in nipple->
—impulses to-> hypothalamus

Hypothalamus 
    — prolactin releasing hormone 
             (for next feeding) 
   —> posterior pituitary gland 
             —> oxytocin 
                  —> contraction of alveoli
                      —> milk ejected !

Question 15

Breast cancer

Answer 15

13/100 females will develop

Risk factors: 
Increased risk if:
- early menarchy + late menopause 
- increased age at having first child or NO children 
- family history