Reproductive

Question 1

Spermatogenesis 3 stages

Answer 1

1) Mitotic proliferation
- Produces large number of cells

2) Mitotic division
- generates genetic diversity and 1/2 chromosomes

3) Cytodifferetiation (Spermatogenesis)
- when morphological features are given to the cell to effectively deliver the oocyte

Question 2

Pregnancy vs conceptus vs gestation period, embryo & fetus

Answer 2

Pregnancy: fertilisation to infant born

Conceptus: developing off-spring

Gestational period: Time from last menstrual period until birth- 280 days

Embryo: conceptus from fertilisation through week 8

Fetus: conceptus from week 9 through brith

Question 3

What is fertilisation/conception

Answer 3

• union of male (sperm) and female gametes (oocyte) to start the process of developing a new individual
• Fusion of genetic material contained within the sperm and that contained within the oocyte and results in formation of zygote

Question 4

What is required for fertilisation/conception to take place
- viability and ovulation times

Answer 4

Sperm must reach the ovulated oocyte
- oocyte viable for 24h
-Sperm viable for 48h

Coitus must occur no more than 2 days before and no more than 1 day after ovulation

Question 5

what is required for conception from sperm and egg- location and quality and general environmnet

Answer 5

Sperm
- Great enough quantity
- must be sufficient quality (motility, morphology and DNA integrity)

Egg
- Oocyte needs to be ovulated
- appropriate location at the time it contacts sperm- fallopian tube

Reproductive environmnet
- at least one patent fallopian tube to allow fertilisation

• Penetration of sperm into oocyte

Question 6

Number of chromosomes in cell bodies and gamates

Answer 6

46
- 2 sets of 23
Homologous chromosomes- one maternal and one paternal

Together called diploid chromosomal number- 2n

• Gametes have only 23 chromosomes- haploid chromosomal number (n)- only one member of homologous pair
• Gamate formation involves meiosis, which differs from mitosis

Question 7

Spermatogenesis- Spermatides to sperms
major regions and timing

Answer 7

Head
- Acrosome enable sperm penetration through the egg

Midpiece
- Metabolic region- mitochondria that produces ATP to move tail

Tail
- Locomotor region

takes 24 days to go from cell to sperm cell

Question 8

oogenesis before birth

Answer 8

• Production of female gametes takes years to complete
• Similar to sperm but longer
• Primary oocyte forms within ovarian follicle- one oocyte per follicle
• all oocyte within follicles and are all formed before birth
• no more follicles made after birth

Question 9

Formation of oogenesis beginning fetal period

Answer 9

• Oogonia- 2n ovarian stem cells multiply by mitosis and store nutrients (Similar to proliferation)
• Primary oocyte stalls in prophase 1 of meiosis 1

At birth, females are presumed to have lifetime supply of primary oocytes

Question 10

Oogenesis after puberty

Answer 10

• Each month after puberty, a few oocytes are selected and from them, dominant follicle is chosen what continues metaphase 1
• After division of meisosis 1 is completed, two haploid cells of different sizes are produced:
  1) primary- devoided of cytoplasm
  2) Secondary- most of mother cytoplasm and organelles

Question 11

After fertilisation

Answer 11

• Follicle around the secondary oocyte grow and rupture till the secondary oocyte is released.
• oocyte is surrounded by some cells of the follicles
• Secondary oocyte and sperm interact leading to fertilisation and meiosis 2 is only completed ones the sperm penetrates the oocyte.

Question 12

Anatomy of the ovulated oocyte

Answer 12

• Ovulated oocyte brings with it some cells of the follicle- corona radiata
• When the primordial follicle developed into the primary follicle, it secretes zona pellucida to form a thick battier around the cell which sperm has to pass through- two barriers to fertilise the oocyte

Question 13

Sperm transport

Answer 13

• 1/25,000 make it to site where fertilisation takes place- fallopian tube
• most ejaculated sperm do not make the 12-cm trip to join the egg
• those that do reach the egg, usually get there very quickly- 5mins

Question 14

Sperm capacitation

Answer 14

• sperm cant be fertilise an egg without being capacitated in the female reproductive track (Or within lab)
• Capacitation is process by which the sperm acquires the ability to penetrate into the oocyte
• caused by the acidity of vagina
• capacitation is the process that removes cholesterol from the plasma membrane allowing permeability of chemicals through the sperm membrane
• The cell membranes must become fragile enough to release hydrolytic enzyme 2-10 hours
• secretions of female tract help to weaken and thin out acrosome membrane
• This process also enhances motility to help the sperm push through the cumulous cells surrounding the oocyte
• basically the acrosome are weaken enough to release the enzymes that are needs to go through the corona radiata

Question 15

5 steps to each the egg

Answer 15

1) Approach
- Aided by enzymes, sperm weaves through corona radiata
- Chemicals on cell surface of sperm act to digest connection between cells of corona radiata, causing them to separate
- Sperm head binds to sperm-binding receptors in zona pellucida, triggering acrosomal reaction

2) Acrosomal reaction
- when triggered, enzymes from many sperm are released that digest holes in zona pellucida all around the cell. they work together for one particular spot so at least one cell can go through.

3) Binding
- After path has been cleared in zona pellucida, a single sperm forcibly swims towards oocyte membrane - Binding causes
- Fusion of oocyte and sperm membrane

4) oocyte and sperm membrane fuse
- cytoplasmic contents of sperm enter oocyte
- tail and other parts, such as sperm cell membrane and mitochondria are left behind on oocyte cell membrane surface and get distroyed.

5) Blocks to polyspermy
Polyspermy does occur in some animals but not in humans. Its monospermy- one cell penetrates oocyte
- One-sperm per oocyte
- two mechanisms ensure monospermy
1) oocyte membrane block or fast block
-
2) zona reaction/ slow block

Question 16

Two mechanisms ensure monospermy

Answer 16

1) oocyte membrane block or fast block
- Sperm binds to sperm-binding receptors on oocyte, all other sperm-binding receptors are shed and other sperm can no longer bind to oocyte plasma membrane
2) zona reaction/Cortical reaction / slow block
- Inside the membrane the enzymes are able to distroy the sperm, sperm binding receptors ect.

• Zona pellucida hardens

Question 17

Completion of meiosis 2 and fertilization

Answer 17

• events involved include
  1) completion of meiosis 2 in oocyte
  2) Sperm and Ovum nuclei swell and become male pronucleus and female pronucleus
  3) Maternal and paternal chromosomes combine, forming diploid zygote
• fertilisation- moment chromosomes combine

Question 18

infertility may be consequences of-

Answer 18

• poor sperm quality or quantity
• annovulation, oocyte quality or poor timing of ovulation/ intercourse
• Passage of the sperm to the oocyte- may be due to mucous, overly acidic environment ect.
• Early fetal loss may be difficult to separate from infertility
• vagina acid too strong

Question 19

Week 1-cleavage what happens?
- fertilised egg name

Answer 19

• The fertilised egg is now known as zygote, encapsulated by zona pellucida still
• undergo first division 26 hours after and continue to divide into call of cells, float freely within uterine tube and into cavity of uterus and implants approx. 7 days after fertilisation
• each division is known as cleavage event

Question 20

what are each of the cleaved cells known as?
what happens on day 4 or 5

Answer 20

Blastomeres

• there is a loose collection of blastomeres known as a morula

day 4-5
- 100 cells which start to hollow out a cavity in the middle- early blastocysts

• At the same time, the zona pellucida breaks down and blastocyst “hatches” from it.

Question 21

what is blastocyst

Answer 21

• sphere
• outer shell of trophoblast cells- placenta
• Inner cell mass- 20-30 cells- baby and other tissues

Question 22

Blastocyst implantation

Answer 22

• Begins at about day 7
• can be high or low depending if the uterus is ready
• if endometrium is not mature, the embryo will implant lower
• trophoblast cells stick to endometrium triggering implantation
• blastocyst induces an inflammatory responds in the endometrium
• this erodes the endometrium allowing invasion of the trophoblast cells
• Trophoblast cells start to form two cell linages at this time

placenta
- cytotrophoblast- stem cell population
- syncytiotrophoblast

Question 23

bilayered embryonic disc- what are two circles that form called

Answer 23

• epiblast
• hypoblast

Question 24

what is gastrulation and the layers it makes

Answer 24

when the two layers fold within themselves and become three
1) Ectoderm
outer skin- nervous system and epidermis- spinal cord,

2) mesoderm
middle skin- everything others don’t

3) endoderm
inner skin- digestive respiratory… guts

Question 25

somites and mesoderm how many pairs and 3 functions

Answer 25

- 44 pairs of somites 3 functions -sclerotome cells produce vertebra, rib at each level - Dermatome cells form dermis of skin on dorsal part of body - myotome cells form skeletal muscle of neck trunk and limbs

Question 26

multiple pregnancies- two twin type

Answer 26

dizygotic twin - two oocytes are related and fertilised Monozygotic twin - identical twins - one fertilised oocyte divides and becomes two embryos

Question 27

fetal development

Answer 27

- the conceptus looks very human like with key external features already viable by the end of the embryonic period- week 8 - the fetal period- from week 9 is characterised by the time of rapid growth of body structures established in embryo - fetus grows 360mm and 3.4kg - fetus becomes less vulnerable to damage from environmental factors - less likely to cause death and major deformities - but because the fetus is more likely to survive, more minor deformities and long term consequences may be present after birth

Question 28

when does fetal development finish?

Answer 28

continues until birth - 40 weeks or 280 days preterm is less than 37 weeks

Question 29

what is the placenta and what role does it play in regulating fetal growth and gestational length

Answer 29

- placenta is central regulator of pregnancy outcomes - regulates fetal grough through multiple pathways and therefore deficits in placental function is the primary cause of IUGR - For any given body weight, there is an optimal placental weight - too large- inefficient placental - too small- poorly developed placenta key role - exchange-nutrients and gases- both blood never mix - barrier drugs n stuff dont mix - so if the mother is stress, the baby would be affected less. It metabolises things and protects the baby - immune function- lower immune so body doesnt reject the fetus - hormone production

Question 30

Placental transport type and example

Answer 30

1) Passive transport- diffusion- oxygen, fats, steroids, fetal waste 2) Facilitated diffusion - specialised transporters NO ATP required - Glucose through GLUT transporters 3) Active transport - specialsed transport -ATP required - amino acids, folate, micronutrients 4) vesicular transport - large molecules - captured by microvilli

Question 31

parturition and labour

Answer 31

- going into labour - combination of pregnancy and contraction of uterus to push the baby out.